CA1108957A - Method and apparatus for controlling intravenous administration of fluid to a patient - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
This invention relates to a method for controlling the dispensing of fluid to a patient from a source at a hydro-static pressure involving the sequential measuring and dis-pensing of predetermined volumetric increments of fluid from the source of fluid during different ones of a series of time intervals, Apparatus is also provided for controlling the dispensing of fluid, including metering means for receiving a predetermined increment of fluid, conduit means for delivering fluid from a source of fluid to the metering means, and con-trol for receiving one predetermined increment of fluid and a condition for emptying the predetermined increment of fluid.
The method and associated apparatus provide for administration of fluid at an accurately controlled rate irrespective of variables, such as, the level of fluid in the source, the venous pressure of the patient, and the viscosity of the fluid.

Description

..

This lnvention relates to a mekhod and apparatus ~or controlling the dispensing of fluid, and more particularly, 'co a means for controlling the intravenous admini~tration of fluid at a hydrostatic pressure to ~ patient.
In the prior art, apparatus used for the intravenous administration of fluid have been generally o~ two basic vari-eties. The most common intravenous adminlstratlon device is o~
the gravity flow type in which the rate o~ delivery o~ fluid is adjusted by means o~ a variable restri~tion. In such gravlty flow æystems, the variable restr~ction is usually provlded by a clamping de~ice that ae~orms a resilient ~lUid dellvery tube connected to the hypodermic needle through which the fluid is introduced into the ~ascular system of the patient. The grav-ity ~low types of devlces may vary wldely in cost and in the manner and complexlty ~or controlling the ~low rate o~ the fluid delivered to the pat~ent.
It has been ~ound that such grav~ty flow dev~ces em-ploying a variable restriction are incapable of reliable and uni~orm operation due to a number of ~actors~ such as, the tendency o~ the plastic delivery tube to be subject to delayed plastic ~low under stress, the v~riations ln the hydrostatic pressure ~rom the volume of fluid to be administered, varia-tions ~n ~luid viscosity, and changes in physical position and vascul~r pressure of the patient that may o~cur during admin-istration of a quantity of ~luid. In the gravlty flow kypes of device~, the ad~ustment o~ the variable restrlct~on governing the ~low rate m~y be required to be per~ormed manually, which is time consuming and subject to erroneous ad~ustment. Also, it is desir~ble for a dockor or nurse to ~requently check the ~low rate ln administr~tion o~ fluid in such devices to make sure that it is properly regulated. Moreover, ~ posslble seri-.`B~ 7 ous problem may occur in use o~ these types o~ devicea when acomplete stoppage o~ flow o~ fluid takes place, L~ khe device is unattanded at the time of exhaustlon of the ~luid. The un-attended stoppa~e o~ ~low o~ fluid at the needle i~ the patient may result in a blood clot which may cause a dangerous condl-tion ~or the patient.
The other common variety of intravenous aclministra-tion device is o~ the pump type which was designed to overcome various disadvantages of the gravity ~low types o~ intravenous administration devices. Many di~ferent ana complicated ar-rangements have been developed for regulating the pumping ac-tion and the quantity of ~luld discharged. In the prior art, much design e~fort has been e~erted to overcome the lnherent capacity o~ the pump to force air lnto the patient with pos-sible ~atal consequences. The pump type o~ intravenous admin-istration device has tended to be expensive, cumbersome7 and complicated in structure. Further, the~e devices have been depenaent upon a source o~ power grea~er than can be reliably and eco~omically supplied by a battery. ~arious clinical rea-20 sons exist for avoiding the ~se o~ alternating current sourcesof power wlth intravenous adminlstration devices, such as, electro-magnetic interferenc~ cre~ted by the power supply in-terfering with sensitlve clinical devices and electrical im-pulses from the electrical systems ~or the pump devices being transmitted through intravenous ~luid, which may be electric-ally conductive, to pat~ents ha~in~ sensltive heark conditlons.
The ob~ect o~ the presen~ lnvention is to provlde a method and associated apparatus ~or intravenous admlnistratlon of ~luid at an accurately controlled rate irresp0ctl~e of variables, such as, the level o~ fluid in the source, the venous pressure of the patlent, and the viscosity of the ~luid.

-2-' ~ '7 The present invention provides apparatus for conkrolling the intravenous adminlstration o~ ~lu~d to a patient ~rom a source o~ fluid at a hydrostatic pressure, comprising me'cering means having inlet means for receiving a predetermined increment of ~luid ~rom the source o~ fluid and outl~t means ~or emptylng the predetermined increment of ~luid without substantial pres-sure; and control .~eans ~or actuating the metering means be-t~een a first condition f~or receiving one predetermined incre-ment of fluid and a second condition ~or emptying the one pre-determined increment o~ ~luid, said control means repetlt,ivelyactivating the metering means between the ~irst and second con-ditions ~or havin~ a dose o~ fluid ~rom the source of fluid aa~
ministered at a predetermined rate of administration.
The present invention also provides a method of con-: trolling the intravenous administration o~ a ~luid to a patient from a ~olume of ~luid at a hydrostatic pressure~ which com-prises the steps of: measuring the fluid ~rom the volume into predetermined volumetric increments, providing desired time in-tervals for se~uentially measuring and dispensing o~ the pre-determined volumetric increments o~ ~luid, and repetitively ~illing and drainLng meterlng means with each of the ones of the predetermined ~olumetric increments of fluid fxom the volume duri~g di~ferent ones of' the time inter~,als and admlnistering intravenously each of the volumetric increments to the body.
The present apparatus enables automatic and progres-sive reduction of the rate of admini~tration o~ the ~luid at or near the time the desired dose has been adm~nistered and be~ore complete e~haustion o~ the ~luid in the administrat:lnn appara-tus so that air ls not lnjected into the patient and blood clotting at the point o~' admlni~tration is pr~vented.
The apparatus is small in size, light ln welghtJ

easil~ portable, and rugged in design. In a preferred ernbodi-ment, the apparatus includes a xeusable timer capable o~ a long expectancy of use and a small, porta~le~ replaceable power sup-ply capable o~ supplylng power to the apparatus. In addition, the parts o~ the apparatus are pre~erably adapted to cooperate together ~n operati~e relationship only when the apparatus is properly assembled and conditioned for sa~e admlnistration o~
fluid and provide such an apparatus which minimizes the likeli-hood o~ error b~ the person responsible ~or performing the intravenous admlnlstration of ~luid to the patient.
The apparatus o~ the present invention may be used in many di~ferent applications for controlling the rate of flow o~
~luid from a source of fluid. The use v~ the present apparatus is not limited to administration of ~luid from a ~ixed volume or quantity of fluid. The apparatus can be used, ~or example, in proportioning the mixture o~ two or more ingredients in a mixing or processing operation where one or more apparatus in accordance with the present invention is employed. While the apparatus for controlling the dispensing o~ ~luid at a hydro-stat~c pressure in accordance with the present invention may beused for dispensing fluid in a wide variety of appl~cations, the apparatus will be described ln use in lntravenous adminis-tratiQn o~ a ~olume of ~luid as a dose in~ected into a host, ~ which may be an animal or human and will be re~erred to herein-; after a~ a patlent. The apparatus o~ the present invention is particul~rly use~ul in this latter applicatlon where an accur-ately con~rolled rate o~ admlni~trat~on o~ ~lU~d ls requi.red and sa~ety in operation o~ the apparatus ls important.
The arrangement o~ the metering me~ns or unit and con-trol means or unit is pre~erably such that, ln dispensing the~luid, the fluid pa~ses through the metering unit without con-~4--~ ,3~
tacting the control unit. ~ence, the control unit does not have to be malntained in a sterile or uncontamina,ted condikion.
The control unit will be reused and only the meter~ng unit) which is made as a disposable item~ will be discardea a~ter having been used once. Therea~ter, upon the next desired use o~ the apparatus, a new metering unit is used ~n cooperatiorl with the control unlt. It should be appreclated that the intra-venous administration apparatus of the present invention can be used for many intravenous adm.lnlstrations of ~luld and only re-quires replacement of the inexpensive metering unit betweenuses. ~urther, the ~eatures of the present invention minimize the llkelihood o~ error in administration of fluid by the per-son responsible ~or using the apparatus and has many safety ~eatures to prevent the occurrence o~ dangerous conditions to the patient during the intravenous administration o~ the fluid.
The invention will now be described with refere~ce to the accompanying drawings~ in which:
Figure 1 is an elevationai view showing an apparatus ~or controll~ng the dispensing o* fluid embodying the present inventio~ connected with a container o~ fluid, Figure 2 is a perspective view o~ the control unit and metering un~t of Figure 1 and showing the units prior to being fastened together;
Figure 3 is a perspecti~e view of the control unit and metering unit of Flgure 2 ~ut showing the unlts ~astened together in operative relatlonshlp;
Figure 4 is an enlarged ~ragmentary sectional vlew take~ along line ~4 of F;igure ~;
Flgure 5 is a ~ragmerltary slde elevational vlew of the meter~ng unit o~ Figure 4 but showing the cover panel o~
the meterlng unit and the metering unit diaphragm removed;

i7 Figure 6 is a ~ragmentary perspectlve view o~ themetering unit diaphragm of Figure 4;
Figure 7 is a sectional view taken along line 7~7 o~
Figure 5;
Figure 8 is a sectlonal view taken along line 8-8 of Figure l;
Figure 9, appearing on the fl~th sheet of the draw-ings, is a ~ragmentary sectional view kaken along line 9-9 o~
Figure 8;
Figure 10 is a sectional view ~aken along line 10-10 of Figure 9;
Fi~ure 11 is a fragmentary sectional view taken along line 11-11 o~ Figure 9, Figure 12 is a fragmentary sectional view taken along line 12 12 o~ Figure 9;
Figure 13 is a reduced-dlmension perspective ~iew of one o~ the valve actuator pins of Figure 9, Figure 14, appearing on the ~ourth sheet o~ the draw-ings, is a sectional view ta~en along line 14-14 of Figure 8 and showing the control unit in the condition in ~hich the metering unit (sho~n in dot-and-dashed lines) is coupled to the ~ontrol unlt, Figure 15 is a sect~onal view similar to Figure 14 but showing the retaining and positioning means of the control unit in a condition in which the metering unit (shown in dot-and-dashed lines) ls rele~sed ~rom, or recei~ed by, the control unit;
Figure 16 ig a ~ra~mentar~ sectional view o~ a portlon of khe mekering unlt and a portlon o~ the control unlt and show~
ing the interlock sensor mechanism o~ the control unitin a condi-tion for preventlng the retaini.ng and positioning means from , ~
: :

~o~

moving the metering unlt into f'ixed operatlve relationship withthe control unit;
Figure 17 is a fragmentary sectional view of a por-tion of the metering unit and a portion of the control uni'c of Figure 16 but showing thelnterlock s0nsor mechanism of khe con-trol unit in a conditlon ~or permltting the retaining and posi tioning means to rnove the metering unit into fixed operatlve relationship with the control unik;
Figure 18 is a fragmen'cary sectional view o~ an al-ternative embodiment o~ a metering unit which may be employedin accordance with the present invention;
Flgure 19 is a plan view of the metering unit of Fig-ure 18; and Figure 20 is an electrical schematic diagram3 partly in bloc~ ~orm, illustrating the timer control clrcuit for pro-viding time intervals during which the control unit actuates the metering unit to receive and empty ~luid~
Referring now to the embodiment of' the invention il-lustrated in Figure 1, the invention is sh~wn in use for intra-venous administration o~ fluid to a patient (not shown~. Theintravenous administration apparatus generally designated 10 for controlling the dispensing of ~luid at a hydrostatic pres-sur~ to a patient is connected to a source o~ fluid 12, which is shown as a fluid storage bottle or container adapt~d to be supported above the apparatus 10, which in turn is pre~erably posltloned a dlstance above the polnt of.' applLcatlon o~ the fluld into the pat~ent. The ~luid may be admlnlstered :Lnto the patient by a hypodermic needle (not shown) inserted into the vascular system o~ the patienk and connected to the output o~ :
the apparatus 10 by suitable, f'lexible kublng 14. It is prefer-red f'or the apparatus 10 to be suspended at a height o~ about , ri 7 thirty inches (76~4 cm.) above the point o~ appllcation ko thepatient to cause fluid to flow from the cont~lner through the apparatus to khe patient by gravity flow. The hydroskatic pressure o~ the fluid as re~erred to herein indlcat~s the ~orce or pres~ure that the ~luid exerts as it ~lows into the apparatus 10, and in the applicatlon of the apparatus in Figure 1, the hydrostatic pressure corresponds to the force or pres~ure of gravity. 0~ course, in intravenous administration~ the term fluid is used to indicate a liquid.
There i~ shown in Figures 1-3 the apparatus 10 com-prising a meterlng means or unit generally designated 16 ~nd a control means or unit generally designated 18. The metering unit 16 and control unit 18, which are shown separated in Fig-ure 2s are adapted to inter~it together, as lndicated in Fig-ures 1 and 3, with the control unit having releasable faskening means cooperating wlth the metering unit for holding the meter-ing unit in ~ixed operative relationship to the control unit 18, The metering unit and control unit are adapted to cooperate together in operative relatlonship such that in dispensing the ~luid by the apparatus, fluid passes through the metering unit 16 without contacting the control unit 18. More parkicularl~, the metering unit 16 is provided for receiving predetermined increments of ~luid from fluid supply bottle or container 12 through lnlet tube or conduit means 20 and for emptying the predetermined increments o~ fluid through butlet tube or con-duit means 14 to the patlent, Control unlt 18 1~ pr~vlded :~or actuating the metering unik between a condltlon ~or recelvlng a predetermined lncrement o~ fluld and a condltion for emptylng the predeterminea increment o~ fluld in a sequential manner.
~ccording to the prererred process o~ use of the in-ventionJ the flu:Ld ~rom the supply container is measured into predetermlned volumetric increments in the metering unit and time intervals are set for measurlng and dispensin~ o~ the pre-determlned volumetric increments o-f fluid through the meteri.ng unit. In this procedure, the invention provide~ ~equential measuring and dispenslng o~ each o~ the predetermined volumet-ric increments o~ fluid durlng di~ferent ones of the time in-tervals. The measuring and dispensing of the volumetric in-crements of fluld is referred to herein as metering o~ fluid.
In thls arrangement, the metering unit 16 is provided with a receptacle or metering chamber having a size of the predeter-mlned volumetric increment and the receptacle is ~illed with fluid by gravity flow from the ~luid supply container and then the receptacle is emptled of fluid for intravenous administra-tion into the body during each of the time intervals, as will be explained more ~ully hereina~ter.
The metering unlt 16 for receiving the fluid from the container 12 and emptying the fluid in predetermin~d volumetric increments to the patlent is shown most clearly in Figures 4, 5, and 9. Metering unit 16 includes a reservoir or drip cham-ber 22, metering chamber 24, inlet conduit 26 connected be-tween drip chamber 22 and metering chamber 24, and sutlet con-duit 28 extending from the metering chamber to an enlarged fluid chamber 30. The *luid from fluid chamber 30 passes through outlet passage 32 into tube 14, which is received in an increased diameter recessed encircling passage 32. The outlet conduit 28 al~o cornmunicates directly wl~h outlet pa~ge 32 by means o~ a channel or groove 32a ~ormed l.n body portion 34 and extending through f'luid cha~er 30, as ~hown in Figures 4, 5, and 9. Metering unit 16 is pre~'erably made o~ a rlgid plas-tic material, such as polystyrene, and includes a main bodymember or portion 34 and a cover portion or panel 36, which _g_ divides the metering unlt inko two parts in ~orrni~g a portion o~ inlet conduit 26~ metering chamber 24, outlet conduit Z8, and fluid chamber 30, as ~hown most clearly in Figures 4 and 9.
Further, a resilient metering diaphragm 38 o~ resilient plastlc material, such as polyurethane, is captured between the metering unit body portion 34 and the meterlng unit cover panel 36. The metering unit bod~ portion 34 and meterlng unlt cover panel 36 with diaphragm 38 captured therebetween are preferably joined together by ultrasonic or high-frequency induction bonding, or may be ~oined together by any suitable epoxy or bonding comp~und or by screws.
As shown most clearly in Figure~ 4, 5, and 9, the in-let conduit 26 has inlet valve means generally designated 40 therein and is a serpentine shaped pas~age aro~nd raised portion or projection 42, which closes inlet conduit 26 in body portion 34 and forms a valve face. Cavlty 44 formed as a recess in cover panel 36 provides a valve cavity and facilitates flow o~
fluid around projection 42 in inlet chamber 26~ Simllarly, out-let conduit 28 has outlet valve means generally designated 46 therein and is a serpentine-shaped passage around raised por tion or projection 48g which closes outlet ~onduit 28 in body portion 34 and ~orms a valve ~ace. Cavity 50 formed as recess in cover panel 36 pro~ides a valve cavity and ~acilitates ~low o~ ~luid around projection 48 in outlet conduit 28. In this arrangement, ~he diaphragm 38, as shown in Figure 6, has a pro-trusion 52, whi.ch provides a resillent valve e}ement received in valve cavity ~4 and a secvnd protrusion 54, whlch provides a re-silient valve element recelved in valve cavlty 50. The resll-ient valve elements 52 and 54 are normally ln the posltlon shown in Figure 4 whlch have the inlet conduit 26 and outlet conduit 28, respectively, in a condition to permit ~luid to ~low ~e~ 7 therethrough. The resilien~ valve elements 52 and 54 are actu~
ated from positions in which the inlet and outlet conduits are open and to positions in which the inlet and outlet conduits are alternately closed by valve actuator means of the control unit, as will be explained more fully hereina~ter.
The metering chamber 24 of the metering unit 16 is ~ormed by two opposed arcuate-ghaped domes or cavitie~ 24a and 24b in body portion 34 and cover panel 36~ respectively. There is provided in arcuate-shaped dome 24a o~ metering chamber 24 a series of arcuate-shaped recesses 56 communicating with drain passage 58~ which in turn communicates with outlet conduit 2~.
The recesses 56 and passage 58 are provi~ed to ~acilitate com-plete emptying of ~luid ~rom the metering chamber when it is desired to empty the ~luld from the metering chamber. In this arrangement, the diaphragm 38 extends through the metering cham-ber 24 and is provided with an arcuate~shaped dome 60, which generall~ con~orms to the shape of arcuate-shaped dome 24a o~
the metering chamber in its normal condition, as shown in Fig-ures 4 and 6. The arcuate-shaped dome 60 o~ the diaphragm pro-~ides a mova~le wall and also conforms to the ~hape of arcuate-shaped dome 24b of the metering chamber. The diaphragm wall 60 is moved by the ~orce of fluid ~lowing lnto the metering chamber to be ad~acent dome surface 24b, when the metering chamber is f~lled wlth fluid as shown in Figure 9. A cylindrical air pas-sage 62 is provided through cover panel 36 communicating with dome portion 24b o~ the metering chamber to p~rmit the movement o~ air ~rom and into the meterlng chamber behind movable di-aphragm wall 60 as the diaphragm wall 60 mo~es betw~en a posl-tion in whlch the metering chamber is emptied, as shown in Fig~
ure 4, and a position in whlch the metering chamber is ~illed with fluid as shown ~n F~gure 9.

-It will be appreciated thatJ as the diaphragm wall 60 moves back and forth for fluid to be received and emptied ~rom the metering chamber 24, fluid only contacts one side of the diaphragm wall 6~ and the area between metering chamber dome 24a and diaphragm wall 60 defines the active fluid receiving and dispensing portion, generally designated 24c in Figure 4, of the metering chamber. Although the size o~ the active fluid portion 24c of the metering chamber 24 varies in size as fluid ~ills and is emptied from the metering chamber, for convenience in describing the apparatus and its operation, the active ~luid portion 24c o~ the metering cham~er 24 will merely be re~erred to as the metering chamber 24 for receiving and emptying fluid.
In the embodiment o~ the diaphragm 38 illustrated in the drawings, the pressure to move the diaphragm wall 60 from the position shown in Flgure 4 to the posltion shown in Figure 9 is as little as one hal~ inch (1.27 cm.) or less of water head. Therefore~ there is alwa~s more than adequate hydrostatic pressure to cause movement o~ the diaphragm wall 60 until the fluid supply above inlet valve 42 ls nearl~ completely exhaust-ed. It is also noted that preferably the diaphragm wall 60moves between its position in which the metering chamber is empty and its position in which the metering chamber is fillea with fluid without subst~ntial resistance. Accordingly, the diaphragm is preferably made of a thin resilient material.
Although the volumetric capacity of metering chamber 2L~ may be made to var~ wirlely depending on the quantity of ~luid desired to be delivered by the apparatus in each volu-metric increment and the particular applicatlon o~ the appara-tus involved, in intravenous administration of fluid lt is preferab~e that the metering chamber be less than one cu~ic centimeter. Particularly, in intravenous administration of r ~

fluids to humans, it is preferable that the volumetric capacityo~ the metering chamber ~or fluid be on the order of two tenths of a milllliter, which is received and emptied from the meter-ing chamber ~s the resilient diap~ragm wall 60 moves back ~nd ~orth. Hence, the predetermined volumetric increment o~ fluid received and emptied by the metering unlt during each time in-terval will be two tenths of a milliliter of ~luid ~or khis capacity o~ the apparatus. In this arrangement o~ the metering chamber, it is preferable to have lnlet conduit 26 and outlet conduit 28 of suf~icient internal cross-sectional area to per-m~t a flow o~ two tenths o~ a milliliter of water through khe conduits in five tenths of a second at a ~our inch (10016 cm.) hydrostatlc pressure o~ the water ~lowing into the metering unit.
The meterlng unit dlaphragm 38 is also provided with a resillent cup-~haped portion 64 arranged to nor~ally extend into ~luid chamber 30, a~ shown in Figure 4. The c~p-shaped portion 64 o~ diaphragm 38 is movable ~rom its normal position to a position where the cup-shaped portion extends into cylin-drical opening 66 through cover p~nel 36 in response to ~luidf illing fluid chamber 30) as when fluid is prevented f~Dm flow-ing through tube 14 (by a closure, not shown, at the lower end o~ tube 14) as showrl in Figure 17. For ex~mple, fluid is pre-vented from flowing through tube 14 when the apparatus is as-sembled and readied ~or operation. The cup-shaped portion 64 o~ the diaphra~m 38 is employed with the ~luid chamber 30 to provide hydraulic mean~ cooper~ble wlth actuatlng mean~ in the control unit to move ~luid f~om the ~luld charnber into the meter~ng chamber to cau~e ~ir in the meterlng chamber to be ex-pelled through the ~nlet condulk 26. The ~luid ls forced fromthe fluld cham~er when the metering unit ls ~astened to the control unit, as will be explained hereinafter in connectionwith assembling the metering unit with the control unlt. A
rigid plastic dlsc 68 i~ pre~erably bonded to the bottom sur-face o~ the cup-shaped portion 64 of diaphragm 38, as shown in Figure 4, in order to str~ngthen the bottom sur~ace o~ the cup-sh~ped portion 64.
The outlet condult 28, whlch communicates between the metering chamber 24 and the ~luid chamber 30, has an ln-creased dimension portlon 28a adjacent the opening to the fluid chamber. The increased dimension portion 28a, as shown clearly in Figure 5, provides an air trap to assure that air in the ~luid chamber 30 passes into the outlek conduit and hence through the metering chamber to the drip chamber 22, as fluid is forced from the ~luid chambex 30 through the metering cham-ber~ when the metering unit is belng coupled into operative rëlationship with the control unit.
Re~errlng to control unit 18 o~ Flgures 1-3, the control unit 18 has an outer case 80 which has removable side panels 82 and 84 secured to the case as by screws 86. Case 80 o~ control unit 18 includes a battery compartment 88, which may contain battery 90 to provlde a source of power ~or elec-trical circuitry in the control unitO Access to tha battery compartment is provided through removable side panel 82~ The opposlte side o~ case 80 houses control compartm~nt 92, which receives electro-magnetic valve actuating means or mechanism generally de~ignated gL~, shown in dot-and-dashed lines in Flg-ure 1, and the electronic timer means eenerally designated 96, which is also shown in do~-and-dashed line3 in Figure l as in-cluding components on a circuit board ~'ixed to removable end panel 84.
The control unit 18 has a central receiving portlon - ~14-or receptacle 98 for receiving the metering ~nlt in inter~itting relationship with the control unit. The control unik -~eceptacle 98 is provided by an opening 100 in front panel 102 of c~ntrol unit case 80, opening 100 dividing front pa,nel 102 into two sec-tlons. More particularly, opening 100 in front pane~ 102 has an lncreased dimension step portlon 104 along its length adapted to recelve increased dimension step portion 34a of the body portion 34 of metering unlt 16 and a step portion 106 serving to close a portion of the ope~ing 100 adjacent the area where lower end 36a of cover panel 36 of the metering unit 16 is to be receivedO In this arrangement, the metering unit will pass ~hrough opening 100 in front panel 102 o~ control unit 18 in only one orienta-tion o~ the metering unit. The top panel 108 of the control unit 18 has a generally L-shaped opening 110 with the end of one leg communicating with opening lOOg and the bottom panel 112 of control unit 18 has a generally L-shaped opening 114 with the end of one ~eg communicating with opening 100 in the front panel. The openings 110 ~d 114 are in regi~try to complete the L-shaped control unit receptacle 98 in the control unit case 80.
The control unit receptacle 98 ls adapted to receive ~ma~ing portions of the metering unit 16 and provldes a cavity o~ suffi-cient size to permit the metering unit to be inserted into the control u~it along one leg of the L-shaped receptacle to a first position in the receptacle, as shown ~n Figure 15, and moved laterally along the other leg o~ the L~shaped receptacle into the contr~l unit to ~ second positlon in whlch thè metering unit is in operati~e relationship with the control unit a~ shown in Figures 1, 39 9, and 14, wherein the electro-magnetic valve actu-ating mechanism of the control unit actuates the valve mean~ of the metering unit to control the receiving and emptying of ~luid ~y the metering unit.

. , . ,, . : , , For the purpose of~ moving the metering Imit laterally in control Imit receptacle 98 ~rom the first position to the second position to be in fixed operative relationship with khe control unit, the control unit 18 i9 provided wlth manually re~
leasable ~astening means generally designated 116, which co-operates with the metering unit for fastening or holaing the metering unit to t,he control unik~ The ~stening ~unction is preferably provided by retaining and po3itioning means or mecha-nism also designated 116. ~he retaining and positioning mech~-nism 116 prefer~bly includes a sliding carriage 118 movable be-tween the ~irst position shown in Figure 15 for receiving and permitting removal o~ the metering unit and the second position shown in Figure 14 for holding the metering unit ln fixed opera-tive relatlonshlp with the control unit. The sliding carr~age 118 is preferably made from a piece of sheét metal and ls ~orm-ed with arms 120 and 122 on one side extending through openings in interior partition or rib 12~ of the control case 80, the partition 12~ defining the inter~or wall o~ battery comp~rtment 88. Slidlng carriage 118 also has arms 126 and 128 extending through openings in internal partition or rib 130 o~ control case 80, partition 130 ~or~ing the internal end wal1 o~ control compartment 92. The arms 120, 122, 126, and 128 position the sliding carriage and mainta~n alignment o~ the car~i~ge as it moves between the first position for receiving the metering unit and the second position in which the metering unit is re-tained in the control unlt.
For ease o~ movement o~ sliding carriage 118, arm 122 i5 generally U-shaped to receive a roller 132, which may be supported by a screw, between the ~ldes of arm 122, and arms 126 and 128 cooperate with rollers 134 and 136, respectively, which m~y be supported by screws, in positioning and guiding ' ,~ f~

movement of the sliding carrlage. In oxder to posi~ion themetering unit 16 on sli.ding carriage.U8 for rnovement with the carriage, sliding carriage 118 has a U-shaped keeper 137 wikh legs or projections 138 and 140 adapted to extend on opposike sides o~ the metering unlt 16. Sllding carr~age 118 also has legs 142 and 144 which extend on opposite sides o~ the meter-ing unit and support the metering unit in lts movement wlkh the sliding carriage between the first position to the second position in the control unit receptacle g8.
Sliding carriage 118 of retaining and positioning mechanism 116 is mo~ed between its first position ~or receiv-ing and removal o:~ the meteri~g unit and its second posltion for having the meteri~g unlt retained in fixed operative rela-tionshlp with the control unit by actuating lever 150 and toggle link 152, as shown in ~igures 8, 14, and 15. More specifically, actuating lever 15~ on the outside o~ back panel 157 has a finger grip projection 154 at one end and is con-nected at its other end 'co pivot stud 156 positioned ln small slot 158 in back panel 157 of control unit case 80. Toggle ~0 link 152 on the inside of back panel 157 is conne~ted to actu-ating link 150 b,y pivot pin 160 extending through arcuate slot 162 in back panel 157, arcuate slot 162 permitting movement of pivot pin 160 over the desired movement of actuating lever 150.
The other end o~ toggle link 152 is pivotally connected to sliding carriage 118 by pi~ot pin 164. Toggle link 152 ha~ an extended end portion 152a with a groove (not shown) adapt~d to receive one end o~ lea~ spring 166, which ha.s its o~her end positioned in a groove in ~lange 168 o~ ,sllding carriage 118.
Leaf spring 166 is adapted to blas toggle link 152 in an over-center position of mov0mentO Stress relie~ spring 170, whlchis held at its opposite ends by tab 172 on back panel 157 and , pivot stud 156 in conjunctlon with b:iasing tab 174 ~ormed lnback panel 157, acts to bias pi.vot stud 156 toward the slidlng carriage in slot 158 to relieve ~tress and provide greater tol-erance in movement o~ the toggle retaining mechanlsm in coopera-tion with sllding carriage 118.
In operation of retainlng mechanlsm 116, the metering unit is positioned within the control unit receptacle 98 with the retaining mechanism in the position shown in Figure 15.
A~ter the meter~ng unit is moved into control unit receptacle 98 abutting the sliding carriage assembl~ 118, actua~ing lever 150 is pivoted from the position shown in Figure 15 clockwise to the position shown in Figure ].4, thereby mo~ing sliding carriage 118 and the metering unit (æhown in dot-and-dashed lines in Figures 14 and 15) to the position shown in Figure 14, wherein the metering unit 16 is in fixed operatlve relationship with the control unit 18. It should be appreciated that the surfaces o~ the control unit ~orming the receptacle together with the legs o~ the sliding carriage provide alignment means for receiving the metering unit and the meterlng unit sur*aces provide mating guides ~or aligning and positioning the metering unit correctly within the control unit.
As the retaining and positioning mechanism 116 moves the meterlng unit from the first position in Figure 15 to the second position in control unit receptacle 98 shown in Figure 14 for havlng the meterlng unit in operative relationship with the cont.rol unit, the hydr~ullc means, compri~ing cup-shap~d diaphragm element 64 in ~luid chambel 30 o~ metering un~t 16, is actuated by actuat~ng means, whlch 1~ pruvided by ram aur-~ace 180a o~' hydraulic actuator boss 180 on partition 130 of control unit case 80. If ~luid chamber 30 of the hydraulic means is ~illed with fluid when the retainlng and positioning . ~, ' ' , ,, mechanlsm moves the ~etering un~t into f'ixed opexative rela-tionship with the control unit, the ~luid in the ~luid cham-ber is forced upwardly in'co the metering chamber by khe action o~ ram sur~ace 180a acting on the cup-shaped diaphragm portion 64, as shown in Figure 17, to move diaphragm portion 64 to a position as shown in ~igure 9. This movement o~ fluid from the ~luid chamber into the metering chamber ~orces air in the metering chamber to be expelled to the drip chamber 22 in the metering unit 16, which prepares the metering unit ~or safe operation with the control unit~ In order to sense whether su~icient fluid is in the fluid chamber 30 to adequately purge air ~rom the metering chamber 24, interlock sensor means generally designated 184, as shown most clearly ln Figures 16-17~ is provided for sensing ~luid in the ~lu~ chamber. The interlock ~nsor means prevents the sliding carriage 118 o~ the retaining and positioning mechanism 116 from moving the meter- -ing unlt into the fixed operative re~ationship when a su~
cient volume o~ ~luid is not present in the ~lui~ chamber 30.
The interlock sensox means or mechanism 184 ~s pro-vided by plunger 186 positioned in a central axial bore through hydraulic actuator boss 180 and extending through a reduced di- ::
~meter opening in partition 130 of the control unit cas~ng 80.
Interlock sensor means 184 also includes L~shaped link 188 plvotally attached to back panel 157 o~ case 80 by pi~ t pin 190~ and connecting rod 192 ~ixed to the plunger and pivotally attached to one end o~ pivoted llnk 188, ~s shown ln ~igures 16 and 17. Pivoted link 188 at it~ other end has a latch mem-ber or pawl 194 adapted to be recei~ed ln detent 196 in arm 128 of sl~ding carrlage 118. Pivoted llnk 188 is norma3.1y biased into a positlon to have pawl 194 engage detent 196 by helical spr~l~ 198, which surround~ a reduced dlameter portion ~' ~L~a3~7 186a o~ the plunger 186 and acts between the head of plunger 186 and partition 130 o~ the control unit case. In thls ar-rangement, when the sliding carriage with the metering unit is moved from its *irst position to its second position, if su~icient fluid is present in the ~luid chamber 30 to have the cup-shaped diaphragm portion 64 in opening 66 in cover panel 36 of the metering unit, as shown in Figure 17, the plunger 186 is forced into boss loO to move pawl 19~ o~ link 188 to a position where detent 196 on sliding carriage 118 is not engaged by pawl 194. Howeverg if suf~icient fluid ls not present in fluid chamber 30, as shown in Figure 16, spring 198 acting on plunger 186 will cause the pivoted l~nk 188 to be biased through rod 192 to have pawl 194 engage detent 196 to prevent sliding carriage 118 from moving the metering unit to its operative position within receptacle 98 o~ the control unit.
whQn the retaining and positioning mechanism 116 ln-cluding sliding carriage 118 moves the metering unit 16 into control knit receptacle 98 to the position shown in Figure 14, metering unit 16 i9 in *ixed operative relationship with control unit 18 to have the valve actuator means ~ o~ the control unit operate the valve means 40 and 46 in the metering unit. With the metering unit fastened to the control unit, as represented in Figure 9, the m~tering unit would abut again~t projections 200 o~ pa~tition 130 to space the metering unit a sl~ght dis-t~nce ~rom partltion 130 to perm~t air to enter opening 62 into the metering chamber 24 enabl~ng ~le~ible cllaphragm wall 60 to move back and ~orth in the meterln~ chamber withouk substantial air resistance or creating a ~acuum. Pre~erably, pro~ectlons 200 ~ormed on partition 130 o~ the control unit case 80 are provlded by three pro~ectlons spaced ln a triangular rnanner to , ,, ' B~7 accurately position the metering unit ad~acent partition 130in the control unit. In a~dition, partitiQn 130 is provided with two outwardly extending positioning bosses 202 and 20l~, whlch are received in mating recesses 206 and 208, respective-ly, of the metering unit, the bosses 202 and 204 and m~ting recesses 206 a~d 208 providing positioning and guide means ~or further aligning and metering unit in operative relakionship with the control unit.
The electro-magnetic valve actuator mechanism 94 of the control unit comprises two electro-magnetic csil assemblies 210 and 212 wound around core member 21~ and spaced apart along the core by support bracket 216) which has a recess 216a in one side adapted to receive a reduced diameter portion 214a o~ core 214 between the coil assemblies 210 and 212, as shown in Fig-ure~ 9 and 11. The other side of support bracket ~16 is sup-po~ted in elongated slot 226 ln partltlon 130. Coll assemblies 210 and 212 and core member 214 are further supported by brack-ets 218 and 220, which encircle core member 214 at opposite end~ thereof to capture the coil assemblies therebetween. The brackets 218 and 220 are fixed to partition or wall 130 as by screws 222 and 224, respectively.
The magnetic circuit for the coil assemblies 210 and 212 is completed by rocker armature 230, wh~ch has leg 23Qa bent to extend closely adjacent end 214a of core member 214 and leg 230b bent closely adjacent end 214b of the core member.
Rocker armature 230 extend~ throu~h a recess ~16b o~ ~upport member 216 and is pivotally positioned at beveled surface 216c o~ support member 216 by lea~ spr:in~ 232, which has one end ~ixed in a slot in partition 130 and lts other end recelved in a slot in rocker armature 230 adjacent the beveled pivot sur-face 216c. A leaf spring 234 is provided tv bias rocker arma-ture 230 in an overcenter condition in its tw~ extreme posi-tions about pivot surface 216CJ and leaf spring 234 is held at one end by pin 236 ~ixed to end 230b o~ rocker armature 23 and at its other end supported in a recess in bracket 220. ~y thi~ arrangement, lea~ spring 234 biases rocker armature 230 in the over center po~ i tion ln which leg 230a is ad~acent end 214a of core member 214 or in the posltion in which rocker armature leg 230b is positioned adjacent end 214b of core mem-ber 214.
As rocker armature 230 moves from one extreme o~ its travel3 such as when coil 210 is energized pulling rocker arma-; ture leg 230a adjacent the core end 214a shown in Figure 9, to the other extr~me of its travel, such as when coil assembly : 212 is energlzed pulllng rocker armature leg 230b ad~acent the core end 214b, the rocker arm~ture moves first valve actuator pin 240 and second valve actuator pin 2~2 between condltions ~or actuating the valve elements 52 and 54, respectively, o~
the first and second valve means 40 and 46, respectively, o~ the metering unit. Mcre speci~cally, valve actuator pins 240 and 242 extend through openings 244 and 246, respectively, in parti-tinn 130, the openings 244 and 246 extending through bosses 202 and 204, respectively. The valve actuator pins 240 and 242 ; further extend through openings in the cover panel 36 o~ the meterlng unlt into ~he valve chambers of cavities 44 and 46, respectively~ to be en~ageabl~ ~rikh the dlap~agm v~lve ~le-ments 52 and 54~ respectively. The outer end~ 204~ and 242a o~
the valve actuator pins 240 and 242~ respectlvely have beveled sur~aces to provide wed~e~haped ends ko lnterack wlth the diaphragm valve elements 52 and 54, respectively, in alkernate-ly closing inlet conduit 26 and outlet conduit 28, respective-lg. It should be apparent that diaphragm 38 provides a seal -2~-between the body portion 34 and cover panel 36 of the meterlngunit so that ~luid flowlng throu~h the metering unlt i~ pre-vented ~rom contactlng cover panel 36, the valve actuator pins and other structure of the control unit.
The valve actuator pins 240 and 242 are actuated through their coupling to rocker armature 230~ as shown most clearly in Flgure ~. More speci~lcally, each o~ valve actua-tor pins 240 and 242 extend through rocker armature 230 and have two positioning pins 240b and 240c and 242b and 242c, re-spectively, extending thro~gh and axially spaced along thevalve actuator pins on opposite sides ol the rocker armature.
Biasing springs 250 and 252 encircle valve pins 240 and 242, respectively, and hare o~ end ~ixed to rocker armature 230 and their other ends abutting washers 254 and 256, respectively, which encircle the valve pins and rest against positioning pins 240c and 242c, respectively. The valve actuator pins 240 and 242 extend through openings in legs 218a and 220a of bracket~
218 and 2209 respectively. Guide pin~ 258 and 260 are fixed to bracket legs 218a and 220a and are received in axlal align-ment slots at the ends o~ valve actuator pins 240 and 242, re-spectively, such as alignment slot 240d of pin 240 shown in Flgure 13. The guide pins 258 and 260 maintain the alignment o~ the valve actuator pins 240 and 242 as the valve actuator p.ins move back and ~orth in actuating their assocl~ted valve elements.
With the metering unlt 16 in operatlonal po~tion within the control unit 18~ the coll a~embly 210 ~ay be ener-gized to have rocker armature leg 230a drawn to the posltion shown in Figure 9 adjacent core end 214a. The magnetic circult for core assembly 210 in this lnstance is through core mernber 214, rocker armature leg 230a, and support bracket 216 to the ~3-other side of coil assernbly 210. In the condition with coil210 energized, rocker armature 230 will bias valve actuator pin 242 against diaphragm valve element 54 to close the outlet valve 46 and prevent flow of fluid through outlet conduit ~8.
With the inlet valve 42 open and the outlet valve 46 closedf an increment o~ ~luid is permitted to ~low into metering cham-ber 24 filling the metering chamber, diaphragm wall 60 being moved to the position in Figure 9 with the meterlng chamber at ~ull capacity.
When coil assembly 210 is deenergized and coil assem-bly 212 is energized, rocker armature end 230b will be drawn ad~acent core end 214b to move valve actuator pin 240 to deform valve element 52, closing inlet valve 42 and hence inlet con-duit 26. In this condition, valve actuator pin 242 does not deform diaphra~m valve element 54 and :~low of fluid is perm~tted through ~utlet valve 46 and hence outlet conduit 28. With the inlet valve 42 closed and the outlet valve 46 open, the ~ncre-ment o~ fluid in the meter~ng chamber 24 w17 1 be emptied and the diaphragm wall 60 will collapse the metering chamber to be in its normal posltlon as shown in Figure 4. Thus, the resil-ient diaphragm wall 60 provides a movable wall in the metering chamber for varying the size of the metering charnber in re-sponse to fluid being recelved in the metering chamber and emp~ ;
tied ~rom the metering chamber. Thls cycle of operation of the inlet and ouklet ~lves i5 repeated a~ the coll assembli~s 210 and 212 are sequent~ally energiæed to move rocker armature 230 between its extreme posLtlon~ actuatLng valve pins 240 and 242 to alternatelg clo~e the inlet and outlet valves~ It should be appreciated that, when the metering unlt 16 Ls moved lnto operakive relation~hlp with the control unit 18 bg retalningand p~sitioning mechani~m 116, one o~ the valve actuator plns -2~

will be actuating its associated diaphragm valve element, such as valve actuator pin 242 actuating diaphragm valve element 54 to close the outlet valve 46 in Figure g. The particular valve actuator pin actuated to close ~ts assoclated valve ~lill depend upon the overcenter position o~ rocker armature 230 when the units are assembled together.
With the meterlng u~it 16 and control unit 18 assem-bled together in operative position, it ls desirable to be able to permlt fluld to flow through the metering unit be~ore the coil assemblies 210 and 212 are alternately energized. For this purpose, val~e-release cam mechanism generally designated 270 is provided to move the engaged valve actuator pin ~rom closin~ its associated valve element in the metering unit.
More speci*ically, valve-release cam mechanism 270 comprises a slidable cam bar 272, as shown in Flgure 12, received in a cav-ity or recess 274 ~n partition 130 of control unlt ~ase 80.
The cavity 274 is formed in a shape to permit limited longitu-d.inal movement of the cam bar 272. The cam bar 272 may be held within cavity 274 by any suitable means, such as screws 276 and 278 having their heads extend over the cam bar in cavity 274.
Cam bar 272 has ta~s 272a and 272b whlch provide cams adapted to contact pins 240c and 242c, respe~tively, if the associated valve actuator pin 240 or 242, respectively, is in a position to close its associated valve~
Actuation of cam bar 272 is provided by manual depres-sion o~ plunger 280, whlch is fixed at one end to flange 272c of the cam bar and ak its other end exkend,s through an openlng ln top casing panel 108 to receiv0 pu~h butkon 282. A helical spring 28~ encircles the push button 282 between khe head o~
the push button and top panel 108 to bias the push button, and, hence, ~am bar 272 to one extreme position o~ its travel in which cam ~ar 272 engages end 274a o~ ca~ity 274 When it isdesired to open both valves in the metering unit to permit flow of fluid through the metering unit, push button ~80 is manually aepressed moving cam bar 272 along its path of travel to have the appropriate cam tab engage the positioning pin of the actu-ated valve actuator pin. For example, in the arrangement shown in ~igure 9J when push button 282 is manually dep~essed moving cam bar 272 along its path o~ travel, cam tab 272b would engage positionin~ pin 242b to move valve actuator pin 2~2 out of de-forming engagement with diaphragm valve element 54. A similarmovement of valve actuator pin 240 would occur, if valve actua-tor pin 240 was deforming its dla~hragm valve elem~nt as when rocker armature 230 is in its other extreme position of move-ment.
A circuit for energizing the coil assemblies 210 ana 212 is schematically shown, partly ln block form, in Figure 20.
The schematic diagram of Figure 20 illustrates the timer means ; ~or sequentially providing a flrst time interval in which the inlet valve permits p~3sage of fluid inko the metering chamber ~or filling the metering chamber and the outlet valve is re-sponsive to the valve actuator pin 242 of the control unit t~
prevent the passage of fluid and providing a second time inter-val in which the inlet valve is responsive to valve actuator pin 240 o~ the control unit to pre~ent passage of ~luid into the meter~g chamber and the outlet valve permlts emptying o~
the increment o~ fluld contained in the meterln~ chamber. The first time interval and second time interval are added to pro-vide a total ~lme interval for a cycle o~ operation o~ the - meterlng unit wlth the control unit.
In the ~chematic diagram o~ Figure 20, battery 90, which is located in control unit battery compartment 88 as . :.- .. , , ...... , , ~
.. , .,. . . . ,. -, .

previously mentionedJ has its negative terminal connected to electrical ground and its positive terminal connected ko manu-al control switch generally designaked 301 having pole or switch actuator 302, which ls shown as a switch button on :front panel 102 o~ control unit casing 80 in Figures 1-3. The other side of switch 301 is electrically connected to coils 210 and 212 from common electrical line 303, as shown in Figure 20.
The other sides of coils 210 and 212 are connected to first timer output circuit 304 and second timer output circuit 306, respect~vely. The ~irst timer oukput circuit 304 and secon~
timer output circuit 306 have switching circuit 308 connected therebetween and each o~ circuits 304, 306, and 308 are elec trically connected to switch 301 by their connection to co~mon electrical line 303 in Figure 20. The function of first timer output circuit 304J second timer output circuit 306, and switch-ing circuit 308 in timer circuit 300 is merely to provide the ~irst time interval in which coil 2~0 is energized and the second tlme inter~al ln which coll 212 is ener~lzed. 0~
course, when coil 210 is energized, coil 212 is deenergized, and vlce versa. Thereafter, the cycle repeats itself with coll 210 ~irst being energized and then deenergized and sub-sequently coil 212 being energized and deenergize~ during the di~ferent time intervals. The sum of the number of tot~l time intervals would comprise a kime period in which a desired dose or ~uantit~ of ~luid would be admi~istered to the patient.
Circuits of the type to ~unction as set ~orth above to alternately energiz0 and deener~ize colls 210 and 212 are conventional in electrical circuitry and the desi~n of thls type of clrcuit is within khe skill in the art. The schematic timer circuit 300 o~ ~igure 20~ is merely provided to indicate one t~e o~ schematic illustration ~or a clrcult to energlze coils 210 and 212. For example, in one sp0cific arrangement ofthe timer circuit ~or Figure 20, first timer output circuit 304 and second timer output circuit 306 are provided b~ s-imilar electrical components. First timer output circuit 304 is pro-vided by a circuit including a programmable unijunction tran-sistor whlch ls rendered conductive ~y the ch~rging of a capa-citor and controls a circuit through the coil 210, the charging ti~e of the capacitor being regulated by a varlable resistor in the programmable unijunction transiskor circuit. When the capa-citor is charged to a predete~mlned potential the unijunctiontransistor is rendered conductive to cause a circuit to be com-pleted through the coil 210, and, when the charge on the capa-citor is dissipated~ the uni~unction transistor ceases to con-duct ~nd the circult through coil 210 is opened to deenerglze the coil 210. Such operation o~ the programmable unijunction transistor circuit also provides an output to switchin~ circuit 308. A simllar type of programmable unijunction transistor circuit with a variable resistor and capacitor arrangement to govern the conduction o~ the prograr~nable unijunction transis~
tor is provided ~or second timer output circuit 306 to control the energizing and deenergizing of coil 212 and provide an out-put to swltching circuit 308.
With this type of programmable unijunction transis-tor circuit for the first and second timer output circuits, ~he ~w~tching circuit 308 is pro~Lded by a bistable flip-~lop cir-cuit, which provides alternatln~ acklv~tlon of the flr~t and second tlmer output circults 304 and 306. An overall manner of operation ~or the ~lr~k and second t.Lmer output circults ln conjunctlon with the ~lip-~lop circuit 308 with the components as outlined abo~e would be a~ follows. When swltch 301 is closed, switching circuit 308 will be in one o~ its stable -2~-conditions to have one of the timer output circuits begin itscycle of causing energization of its associat,ed coil~ For ex~
ample, if switching circult 308 ls in the condition to have the ~irst timer output circuit 304 begin in it~ cycle o~ operation, a capacitor is charged to a potential for rendering conductive its asso~iated programmable unijunction transistor to cause completion of the circuit throu~h the coil 210, thereby ener-gizing the coll. ~hen the ~irst timer output circuit becomes non-conductive, current ~low through coil 210 wlll stop. A
light ernitting diode 310 ~s shown connected across coll 210 and is operated by the voltage created by the collapsing field in coil 210 to energize the light emitting dlode 310. Thus, without draining energy ~rom the battery, ~iode 310 provides a light signal indicating khat the control unit is operating.
The light emittlng diode 310 may be positioned in the front panel o~ the control unit casing 80, as shown in Figures 1-3, to provide a clearly visible indication o~ the operatio~ of the control unit. When first timer output cirouit 304 is actuated between its conductive and non-conductive states, a signal is provided to flip~flop circuit 308, which switches it to permit second timer output circuit 306 to operate through its cycle of conductive and non conductive states to energize coll 212 and reset the flip-flop circuit to begin the cycle of conduction and non-conduction for the first timer output circuit. This cycle of operation continues throughout the administration of a desired dose of fluid, thereby causing the meterin~ chamber to recelve and drain the volumetric lncrement~ of fluld of a ~uan-tity predetermined by the capacity of the metering charnber 24.
In the admlnlstration of fluid to a patlent, lt Ls ~; 30 preferàble to have the tlme interval ~or permittln~ the metering chamber to be drained or emptied longer than the time interval for filling the metering chamber, so that ~ufficient time will always be allowed to permit complete draining of the metering chamber during each drain cycle or interval irrespective of the several variables which affect the rate of flow of fluid ~rom the metering chamber. The time in~ervals for operation of the inlet and outlet ~alves may be set at di~ferent len~th.s by ad-justing the variable resistors which regulate the charging of the capacitors in the ~irst and second timer output circuits 304 and 306. In the pre~erred arrangement of the apparatusJ
the time interval ~or the inlet valve being open ~or ~illing the metering unit would remain constant and need not be vari~d in use of the apparatus in controlllng the lntravenous adminis-tration o~ fluids. In order to facllitate variations in time ~or the outlet valve to be opened, a control dial 312 for con-trolling the resistance o~ the variable resistor in the first timer output circuit 304 is provided. In this manner, the time for energlzing coil 210 and, hence, closing the outlet valve is varied. The dial 312 varying the time interval of operation o~ the ~irst timer output circuit 306 is pro~ided on front panel 102 oP control unit case 80, as shown in Figures 1~3, and is calibrated in milliliters per minute for ease of use o~ the apparatus. For example, dial 312 may be calibrated from two tenths milliliters per minute of administration of fluid to ten milliliters per minute o~ administration o~ fluid to provide a gradation in rate of admlnistration of ~lu~.d by the apparatus. For e~ch adminlstxatlon of a dose of ~luid to a patient, dial 312 would be set to a deslred ~low rate o~ the ~luid.
In the setup o~ the apparatus in accordance w:Lth the present invention to administer a prescribed dose of ~luLd to a patient, the metering unit 16 is connected to tube 14. A cap ~

(not shown) normally provides clssure of the other end o~ out-let tube 14 and is subsequently removed ~or connection 3~ the hypodermic needle to tube 14. Conduit means 20 o~ the mek~ring unit 16 is plugged into st~ndard dose container or ~ot'cle 12, containing the prescribed dose o~ fluid to be administered.
Container 12 is then suspendcd in an inverted position with the metering unit connected thereto above the level of the patient to whom the ~ose is to be admini~t,~red so that fluid will drain through the metering unit by gravity flow and so that the meter-ing chamber is permitted to drain completely during each draininterval. For a patient con~ined to bed, the metering unit should be positioned at a level about thirty inches or more above the patient. This arrangement prov~des a sufficient pres-sure di~ferential between the level o~ fluhd in the metering chamber and the venous pressure o~ the patient to overcome the venous back pressure of the pat~ent and allow complete emptying oi the metering chamber during each drain inter~al. Also, the pressure o~ the fluid flowing ~rom the container by gravity flow provides the fluid at a hydrostatic pressure to properl~
operate the filling of the metering chamber.
In this orientation o~ the fluid container 12 and metering unit 16, fluid will flow by gravity down into the metering unit, which will subsequently be coupled to the control unit, through the inlet valve to partially ~ill the metering chamber by moving diaphragm wall 60 under the pre~sure o~ the fluid. The ~luid will also pass ~rom the meterlng chamber through the outlet valve into the ~luld chamber, thereby moving cup-shaped dome 64 of the diaphragm under the pressure of the flu~ to increase the capacit~ of flui.d chamber 30, a~ when cup-shaped diaphragm portion 64 is ln the positlon shown ln Figure 17. The fluid ln passlng through the metering unit 16, as described above, will also generally flow a distance into the top o~ outlet tube 14 before the pressure of air will re-strain the ~luid flow. It should be appreciaked that khe fluid flowing through the metering unit a~ described will drip through the reservoir or drlp cham~er 22 without filling the drip chamber or causing a reservoir of ~luid in the drip cham-ber due to the air captured therein.
The control unit 18 is next coupled to the metering unit by inserting the metering unit into control unit receptacle 98 within the legs o~ sliding carriage 118, as when the retain-ing a~d positioning mechanism 116 of the control unit 18 is in the position shown in Figure 15 with the metering unit being indi~t~d in dot-and-dashed lines. As pre~iously mentioned, the surfaces de~ining the control unit receptacle and the meter-ing unit are provided such that the metering unit fits within the control unit receptacle 9~ in only one orientation. The actuating lever 150 of the fastening or retaining mechanism 116 is moved in a clockwise direction, as shown in Figure 15, to move the sliding carriage and, hence, the metering unit into operative relationship with the control unit, in which condi-tion the meterlng unit is ad~acent p~rtition 130 o~ the control uni~ so that valve actuator pins 240 and 242 may open and close the inlet and outlet valves of the metering unit when the electro-magnetic mechanlsm 94 is energized. It should be ap-preciated that, with ~luid in the fluid cham~er, cup-shaped diaphragm port~on 64 actuates the plunger 186 o~ interlock sensor means 148 to permit detent 196 of' slldirl~ carriage 118 to move free o~ pawl 194 to the second position u~ the sliding carriage shown in Figure 14.
As the metering unlt 16 is moved into ~ixed operative relati~nship with the conkrol unit, the hydraulic actuator :

'7 moves cup~shaped diaphragm portion 64 into its normal position~
thereby ~orcing ~luid ~rom the ~luid chamber 30 into metering chamber 2~ and drip chamber 22. This ~orcing of fluid ~rom the ~luid chamber into the metering chamber purges air ~rom the metering chamber and communicating conduits and partially ~ills the reservolr or drip chamber 22 with ~luid. To purge air from the outlet tube 14, the cap (not shown) on the tube 14 is re moved and valve release cam mechanism 270 is actuated by br~e~-ly depressing push button 282 to cause both the inle~ and out-let valves to be opened to permit fluid to ~low through themetering unit and tube 14. With tube 14 filled wlth ~luid, the hypodermic needle is connected to the tube in a convention~
al manner, the h~podexmic needle being inser-ted into the vascu-lar system o~ the patien-t.
The app~ratus is set to ~ desired flow rate of the fluid b~ rotating dial 312 to the desired point as indicated ; on the calibration scale on the front panel. The settlng of dial 312 is translated into a desired rate o~ administration o~
each volumetric increment o~ fluid held by the metering chamber by varying the time interval that the outlet ~alve remains open ~or emptying o~ the predetermined increment o~ fluid ~rom the metering chamber. Initiation of the administratiQn o~ ~luid is begun by actuating switch button 302 to its "ON" position, mov-ing the switch pole 302 to close switch 301 in timer cir~uit 300. The operation o~ timer circuit 300 recycle~ the electro-magnetic valve actuating mechanism to cau~e the ~llling and emptying o~ the metering chamber once during e~ch cycle of oper-ation o~ opening and closing the inlet and outlet valves o~ the metering unlt. As previously rnentioned, during each cycle o~
operation o~ the timer circuit, the inlet valve would be open to permit ~llling of the metering chamber to capacity with ~ ~13~

diaphra~m wall 60 abutting metering chamber sur~ace 21~b andthen the inlet valve would be closed and the outlet valve open so that ~luid flows by gravity from the meterlng chamber to the patient emptying the metering chamber bePore another cycle of operation. Hence, the inlet valve and outlet valve are alter-nately opened and closed during each time lnterval, as rocker armature 230 moves from one of its 0xtreme positio~s to the o.bher. However, it should be appreciated that when rocker arma,-ture 230 pas~es through its neutral position~ both the inlet valve and outlet valve are closed by the valve actuator pins 240 and 2~2, respectively, so khat at no time are both valves open when the metering unit is fastened in operative relation~
ship with the control unit.
~ ormally, the termination of administration ~f a dose is accomplished by the removal o~ the hypodermic needle from the patient immediately upon completion of administration of the prescribed volume o~ fluid and while fluid ls still flowing through the hypodermic needle or immediately after flow of fluid is stopped. The container containing the prescribed dose usual-l~ contains a quantity of *luid beyond the prescribed dose forsafety in preventing the stoppage of ~low of fluid immediately upon a prescribed dose being administered~
In accordance with the pres~nt i~ention, as hydro-static pressure in ~he supply source container decreas~s due to the level o~ ~luid being lowered some distance below the level where the prescrlbed dose has been admlnistered (or the ~:luid source contalner has been dralned below a predetermined level), the volume o~ ~luid in each increment passing through khe meter-ing chamber will automakically be ~radually reduced. For ex ample~ when ~luid only remains in the reservoir or drlp chamber 22, which has the fluid at a lower or second hydrostatic pressure than that provlded by the f~luid in supply conkainer 12, fluia will only ~ill the metering chamber to a reduced volume during the time intervals when the outlet valve is closed and the in-let valve is open in the metering unit because the pressure of the ~luid is not sufficient to cause fluid to flow into the metering chamber ~ast enough to fill the metering chamber to capacity within the tlme interval provided.
It will also be appreciated that the fluid level at ~lch the reduction in the size of the volumetric increments of ~luid in the metering chamber occurs a~ter the desi~ed dose has been administered will be affected by the viscosity of the fluid bein~ admini~tered. Nevertheless, the apparakus will operate at ~ reduced rate o~ ~luid administration to protect the patient and permit a longer time period for the hypodermic ~eedle to be removed from the patient by the doctor or nurse without serious adverse conse~uences to the patlent. It will further be appreciated that~ even after there isinsuff'icient fluid above the inlet valve to cause movement of the diaphragm wall in the metering chamber, air will not pass through the metering chamber due to an inherent tendency of the diap~agm wall 60 to act as a shuto~ valve when the hydr~static pressure in the part of the drainage system directly below the metering chamber is below atmospheric pressure.
It should be understood that many modi~lcations rnay be made in the arra~gement of the apparatus in accordance with ths present invention whlle st,ill employing the concept of the invention. A modifled embodiment of t,he metering unlk ~s shown, for example, in Figures 18 and 19. In the ~mbodiment shown in Figures 18 and 19, the metering unit has been modi~led to provide greater ef~ectiveness o~ the automatic c:lowing down of the rate of' administration of fluid through the metering unit a~ter a prescribed dose has been administered. The primar~ di~erence in structure o~ the metering unit Or Figures 18 and 19 and that o~ Figures 1~4 lies in the change in size and location of the reservoir or drip chamber. Metering unit - 400 in Figures 18 and 19 has a meterlng unit body 402 which is identical to the m0terlng unit body o~ the metering unit o~
Figure 4 in the provlsion o~ the inlet valve, metering charnber, outlet valve, and ~luid chamber arrangements. The metering unit 400 has its reservoir or drip chamber 404 o~set, lowered, ànd enlarged from the location in Figure 4. Drip chamber 404 is enlarged ~or increased capacit~ to provide a greater reser-voir supply ~or fluid, and the drip chamber is of~set and lowered with respect to the inlet val~ in the metering chamber ~n order ~or the arip chamber to supply the last few cubic cen-timeters o~ fluid to the metering chamber at a very 10W hydro-static pressure as the fluid drains ~rom the drip chamber into inlet conduit 408. Inlet conduit 408 is shaped to have the fluid ~low upwardl~ along a vertical path before proceeding downwardly through the metering unit inlet valve generally designated 110 to the metering chamberO Also, in Figure 18, the length o~ inlet passage 406 is increased in order to pro-vide a æufficient hydrostatic pressure above the metering cham~
ber for reliable operation with a very short time interval for filling the metering chamber. In th~s arrangement, the rate of administration o~ ~luid through the metering unit will de-crease slgnlficantly before the ~luid level in passa~e 406 ls e~hausted and will decrease to a minute ~raction o~ khe selecked rate of administratlon be~ore stopping completely~ Xn use of the metering unit of Figures 18 and 19, the receptacle o~ the control unlt, such as shown in Figure 3, would have to be en-larged and modi~ied in o~der to accommodate the enlarged and oP~set drip chamber porti~n of the modified metering unit as would be obvious to those skilled in the art. It should also be understood that the drip chamber illustrated in Figure 1~
could be considered a lower extension of the supply container for the purposes of accomplishing the automatic reduction ln rate of Pluld administration of this invention and the reser-voir or drip chamber need not be integrally attached to the body o~ the metering unit as part of the metering unit. For exampleg the reservoir chamber might be connected ko the meter-ing unit by a flexible tube.
It should be appreci~ted th~t provision may ~e madein the apparatus for means to vary the size of the metering chamber~ depending on the desired quantit~ of fluid to be de-li~ered in each increment received and dispensed by the meter-ing chamber. An adjustable member could be provided from the control unit extending through opening 62 o~ the metering unit into the metering chamber to vary the stroke of the diaphragm wall 60 in filling the metering chamber wlth the desired incre-ment of fluid. Further~ many di~erent electro-magnetic valve actuator arrangements may be provided besides the specific toggle rocker armature arrangement disclosed. Electronic cir-cuitry could be provided to independently actuate each valve element to open and close the inlet and outlet valves in the metering unit. Moreover, in m~ny application~ of the metering apparatus, the drip chamber may be omitted ~rom the apparatus, and the ~luld chamber and a~soclated ln~erlock sensor mechanlsm may be omltted. Furthermore, the Pa3tening means for h~lding the metering unit and control unit together in ~lxed operative relationship could be provided as part of the metering unit, ; 30 if desired.

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Claims (17)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A disposable metering unit for use in control-ling the intravenous administration of a fluid to a patient, comprising:
inlet conduit means for delivering fluid at a hydro-static pressure from a source of fluid; metering means for receiving a predetermined increment of fluid from the con-duit means and for emptying the predetermined increment of fluid without adding substantial pressure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means being capable of being moved at the hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm means, and a second position in which the diaphragm is in contact with the other of said opposed inner walls of the metering cham-ber with substantially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering means may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means; and outlet conduit means communicating with the meter-ing means for receiving said increments, both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communicating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in contact in its second position, to facilitate free flow of air into and out of said metering chamber as said dia-phragm means moves between its first and second positions;
and means for permitting the alternative and sequen-tial valving of fluid through said inlet conduit means and outlet conduit means.

2. The disposable metering unit of Claim 1 in which a projection is positioned on the inner wall of each inlet and outlet conduit means in opposed relation to apertures in said walls to serve as part of said valve means.

3. The metering unit of Claim 1 in which the unit includes a rigid body portion and a cover portion with a cavity formed in the unit to provide the metering chamber, the size of the cavity determining the capacity for the predetermined increments of fluid.

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4. The metering unit of Claim 1 in which the mov-able diaphragm means is resilient to conform to the shape of the cavity.

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5. The metering unit of Claim 1 in which the unit includes a rigid body portion and a cover portion with an arcuate-shaped cavity formed in the body portion and a . communicating arcuate-shaped cavity formed in the cover portion to provide the metering chamber.

6. The metering unit of Claim 1 in which the meter-ing chamber has a volumetric capacity of less than one cubic centimeter.

7. The metering unit of Claim 6 in which the valve means is actuated to provide the predetermined rate of administration of fluid in the range of two tenths milliliter per minute to ten milliliters per minute.

8. The metering unit of Claim 1 further including hydraulic means with a fluid chamber receiving fluid from the metering chamber for having fluid in the fluid chamber moved into the metering chamber to cause air in the metering chamber to be expelled through the inlet conduit means when the metering unit is in operative relationship.

9. The metering unit of Claim 1 further including a reservoir chamber adapted to receive a portion of the in-crements of fluid from the source at a first hydrostatic pressure and to hold the fluid at a second hydrostatic pres-sure, the metering chamber receiving the predetermined in-crement of fluid from the reservoir chamber and emptying the predetermined increment of fluid without adding sub-stantial pressure to the second hydrostatic pressure.

10. The metering unit of Claim 9 in which means is provided for supporting the reservoir chamber with respect to the metering chamber so that when the source of fluid has been drained below a predetermined level, the second hydro-static pressure of the fluid in the reservoir chamber is only sufficient to have the metering chamber receive a portion of a predetermined increment of fluid from the reservoir chamber to be emptied from the metering chamber,

11. A disposable metering unit for use in control-ling the intravenous administration of a fluid to a patient, comprising:
inlet conduit means for delivering fluid at a hydro-static pressure from a source of fluid;
metering means for receiving a predetermined incre-ment of fluid from the conduit means and for emptying the pre-determined increment of fluid without adding substantial pres-sure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means being capable of being moved at said hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm means, and a second posi-tion in which the diaphragm is in contact with the other of said opposed inner walls of the metering chamber with substan-tially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering means may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means;
, outlet conduit means communicating with the meter-ing means for receiving said increments, the transverse dimensions of said inlet and outlet conduit means being substantially less than the transverse dimension of said metering means, said diaphragm means defining extensions re-siding in said inlet and outlet conduit means; both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communicating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in contact in its second position, to facilitate free flow of air into and out of said metering chamber as said diaphragm means moves between its first and second positions; and apertures positioned in said inlet conduit means and outlet conduit means adapted to permit passage of plunger means respectively into said inlet and outlet conduit means to respectively press said diaphragm extensions into sealing relationship with walls of the inlet and outlet conduit means, to selectively block liquid flow through said inlet and outlet conduit means.

12. The disposable metering unit of Claim 11 in which a projection is positioned on the inner wall of each inlet and outlet conduit means in opposed relation to said apertures, to define a valve face against which said diaphragm extensions are pressed by said plunger means.

13. A disposable metering unit for use in control-ling the intravenous administration of fluid to a patient, comprising:
(a) a metering chamber for receiving a predetermined increment of fluid from a source of fluid at a first hydro-static pressure and for emptying the predetermined increment of fluid without adding substantial pressure to the hydrostatic pressure;
(b) a reservoir chamber adapted to receive a portion of the increments of fluid from the source at said first hydro-static pressure, and to hold the fluid at a second hydrostatic pressure;
(c) conduit means for delivering fluid at the source of fluid having a supply of predetermined increments of fluid to the metering chamber; and (d) valve means actuatable for regulating the re-ceiving and emptying of each of the predetermined increments of fluid by the metering chamber to be administered to the patient at a predetermined rate of administration.

14. The metering unit of Claim 13 in which means is provided for supporting the reservoir chamber with re-spect to the metering chamber so that when the source of fluid has been drained below a predetermined level, the second hydrostatic pressure of the fluid in the reservoir chamber is only sufficient to have the metering chamber receive a portion of a predetermined increment of fluid from the reservoir chamber to be emptied from the metering chamber.

15. Apparatus for controlling the intravenous ad-ministration of fluid to a patient which comprises:
inlet conduit means for delivering fluid at a hydro-static pressure from a source of fluid;
metering means for receiving a predetermined incre-ment of fluid from the conduit means and for emptying the predetermined increment of fluid without adding substantial pressure to the hydrostatic pressure, said metering means defining a metering chamber having opposed inner walls, and movable diaphragm means positioned in the metering chamber, said diaphragm means capable of being moved at the hydrostatic pressure between a first position in which said diaphragm means is positioned against one of the opposed inner walls of the metering chamber with substantially all of the volume of the chamber being on one side of the diaphragm and a second posi-tion in which the diaphragm is in contact with the other of said opposed inner walls of the metering chamber with substan-tially all of the volume of said metering chamber being on the other side of said diaphragm means, whereby said metering chamber may be repeatedly filled with fluid to impel the diaphragm means into its second position and then to drain said fluid from the metering means with the diaphragm means moving to the first position, whereby said predetermined increments of fluid may be of constant volume and may be passed through said metering means, both said inlet and outlet conduit means communicating with the metering chamber at the same side of said diaphragm means, said metering means defining exterior vent means communi-cating into said metering chamber adjacent the opposed inner wall of said metering chamber with which the diaphragm is in , contact in its second position, to facilitate free flow of air into and out of said metering chamber as said diaphragm means moves between its first and second positions; and outlet conduit means communicating with the metering means for receiving said increments, and means for permitting the alternative and sequential valving of fluid through said inlet conduit means and outlet conduit means.

16. The apparatus of Claim 15 in which the transverse dimensions of said inlet and outlet conduit means are sub-stantially less than the transverse dimension of said meter-ing means, said diaphragm means defining extensions residing in said inlet and outlet conduit means, apertures positioned in said inlet conduit means and outlet conduit means, and plunger means adapted to pass respectively into said inlet and outlet conduit means through said apertures to respec-tively press said diaphragm extensions into sealing relation-ship with walls of the inlet and outlet conduit means, to selectively block liquid flow through said inlet and outlet conduit means.

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17. The apparatus of Claim 16 in which a projection is positioned on the inner wall of each inlet and outlet con-duit means in opposed relationship to said apertures, to de-fine a valve face against which said diaphragm extensions are pressed by said plunger means.