US2308974A - Positive displacement pump - Google Patents

Description

Jan. 19, 1943. L. E. HARPER POSITIVE DISPLACEMENT PUMP 2 Sheets-Sheet 1 Filed Nov. 1, 1939 Vm Qm a Ra Y m w Patented Jan. 19, 1943 UNITED STATES: PATENT OFFICE Claims.

My invention relates to positive displacement pumps, and more particularly to a liquid feeding device of a pump-like. character that will accurately meter the amount of liquid fed by each reciprocation of the pumping device.

It is a particular purpose of my invention to provide a positive displacement pump for accurately measuring small quantities of liquid.

In order to accomplish this purpose it is necessary that an exact quantity of liquid be discharged by the pump for each cycle of operation thereof, that is, for each intake and discharge stroke. Preferably, this is accomplished by providing inlet and outlet valves for the pump, that are positively closed so that the outlet valve will be positively closed before the intake, or suction stroke, of the pump begins, and so that the inlet valve will be positively closed before the discharge stroke commences, it being, of course,- also preferred, inasmuch as the material that is pumped is a substantially non-compressible liquid, that the outlet valve be opened at least as soon as the discharge stroke begins, and that the inlet valve be opened at least as soon as the suction stroke begins.

It is a further purpose of my invention to provide a pumping device of the above mentioned character, which comprises a chamber that is provided with an inlet and outlet connection,

- having positively operated valves controlling certain inlet and outlet connections, which are positively operated in apredetennined timed relation to the strokes of a reciprocable member,

which varies the liquid capacity of the chamber, so-as to produce apumping action of the liquid that maybe received within the said chamber from the inlet connection and discharged through the outlet connection. Preferably, the reciprocable means is operated in such a manner that there is an interval of short duration at the point of reversal of motion thereof between the alternating strokes thereof, during which said reciprocable member is stationary for a sufficient period of time, so that the inlet valve can close and the outlet valve open, and vice versa, without there being any possibility of there being movement of the reciprocable member in the wrong direction, while either the inlet or the outlet valve is open, which would, of course, interfere with the accurate measurement of the liquid by means of the pumping device.

Preferably, my improved pumping device embraces means for varying the amount of liquid pumped per stroke of the pump, so that the measured amount of liquid furnished at a certain rate of rotation of the pump may be adjusted as desired, this being, preferably, accomplished by varying the length of the stroke of the reciprocable member. Preferably, adjusting means is provided for varying the length of the stroke of the reciprocable member, which is provided with indicating means thereon showing either the amount of liquid being pumped per stroke, or some other unit of measurement, or any arbitrary scale that may be decided upon, to indicat e the desired adjustment. It is also desirable to operate the reciprocable member in a manner that the discharge stroke is relatively long and the suction stroke relatively short, so

as to reduce the intermittent character of the supply of liquid from the discharge end of the pump, which necessarily exists due to the pumping cycle, in a single chambered pump. Furthermore it is desirable, in order to not have too great an inactive interval for the pumping device during which no reciprocation takes place, that the valves open and close abruptly, and suitable cam means for this purpose are, preferably. Provided.

Preferably, my improved pumping device is driven by a rotatable-member, which is provided with suitable means for reciprocating the reciprocable member, and has directly rotatably mounted thereon to rotate therewith, the cam means for actuating the valves. It will be obvious that not only can the capacity of the pump during any interval of time be varied by varying the stroke of the reciprocable member, but that this can also be varied by varying the speed of the rotatable means for reciprocating said member.

One of the purposes of my invention is to provide pumping means that comprises a diaphragm for varying the liquid capacity of the pump chamber, and one of the preferred means for flexing the diaphragm to vary said liquid capacity comprises a bore, .or cylinder, in which a reciprocable plunger, or piston, operates, the surfaces of the piston, and cylinder being of such hard material that these can be made to fit so closely that liquid interposed between said piston,

or plunger, and the diaphragm, will not leak 'past the engaging walls of said piston and cylever, that I do not intend to limit myself to the particular details shown or described, except as defined in the claims.

In the drawings:

Fig. l is a view partly in elevation and partly in vertical section of one form of my improved metering pumping device.

Fig. 2 is a section taken on the line 2--2 of Fig. 1, on an enlarged scale.

Fig. 3 is a section taken on Fig. l, on an enlarged scale.

Fig. 4 is a section taken on the line 4--4 of Fig. l, on an enlarged scale.

Fig. 5 is a fragmentary section taken on the line 5-5 of Fig. 1, on an enlarged scale.

Fig. 6 is a view similar to Fig. 1, of another form of my invention.

Fig. 7 i a section taken on the line 1-1 of Fig. 6, on an enlarged scale.

Fig. 8 is a section taken on the line 88 of Fig. 6, on an enlarged scale.

Fig. 9 is a view partly in elevation and partly in section of the adjustable eccentric used in the form of the invention shown in Fig. 6.

Fig. 10 is a section taken on the line ill-l0 of Fig. 9, and

Fig. 11 is a view partly in elevation and partly in section of another form of my invention.

Referring in detail to the drawings, in Fig. 1 is shown a pumping device having a frame 20, upon a portion of which is mounted any suitable means for driving a shaft, such as the motor 2|, which is shown as driving the shaft 22 through a worm drive reduction gearing, indicated at 23, said shaft being mounted in suitable bearings 24 on the frame 28, and having provided thereon a main driving cam 25 and th valve cams 26 and 21, said cams 25, 26 and 21 being fixed to said shaft to rotate therewith.

Mounted on said frame in any suitable manner in fixed relation thereto, is a pump chamber 28 made up of the sections 29 and 38, said sections 29 and 30 being secured together in liquid tight relation by suitable securing elements 31 clamping the gasket 32 between suitable clamping faces on said members 29 and 30. The member 30 is shown as being provided with an inlet passage 33 and an outlet passage 34. While the particular shape of the chamber 28 may be varied, and the particular arrangement of inlet and outlet passages may also be varied, it is important that the inlet and outlet passages be so located that no air pockets can develop in the chamber 28, as no compressible gases must be contained therein, in order that the device will operate to measure the liquid passing therethrough properly.

The member 29 is, preferably, provided with a tubular projection 35 having a bore 38, which serves as a cylinder for the reciprocation of the cylindrical plunger, or piston, 31 therein. A tight joint is provided between the member 35 and the member 31 reciprocating therein, by providing a suitable packing gland arrangement made up of the compressible packing 38, and the packing nut 39 engaging the external threads 48 on the member 35. The member 31 is reciprocated by means of the cam 25, said member 31 having an extension 4|, which operates slidably through a suitable guide 42, and which is provided with a bracket 43 on the end thereof having bifurcations 44 providing a suitable mounting for a pivot 45 for a roller 46, which engages the cam 25 to reciprocate said member 31, it being, of course, obvious that the liquid capacity of the chamber 28, which comprises a portion or the bore 38 the line 3-3 0:

for certain positions of the plunger, or piston, 31 will be varied in accordance with the portion of the plunger, or piston, extending into said chamber 28 and its connected cylinder 36.

Means is provided for varying the amount of movement of the member 31 to vary the capacity of the chamber 28, the means shown varying the length of the return stroke so that the cam is only effective through a portion thereof when the stroke is reduced from its maximum. Any suitable means for varying the length of the stroke of the reciprocable member that operates in the chamber may be provided, the means shown comprising an adjustable stop member 41, which cooperates with a stop member 48 fixed to the extension of the member 31, a compression spring 49 being shown as being mounted between the member 48 and the nut 39 for retuming the plunger 31 from its furthest projected po. sition to make the roller 46 follow the cam until the stop 48 engages the stop 41. The stop 41 is made or such shape that the peripheral edge 50 thereof progressively extends from the pivotal axis of the member 41 a certain unit of measure for each predetermined unit of arcuate movement of the member 41 about its pivot, in this form of the invention shown, the member 41 being pivotally mounted on a headed pin 51, which screw-threadedly engages in a suitable threaded boss 52 in the frame 20, and which is provided with any suitable means, such as the cross bar 53 on the head 54 for tightening the same up when the member 41 has been moved to a desired adjusted position. A scale 55 is, preferably, provided on the member 41 and any suitable cooperating indicator, such as the knife edge projection 56, may be provided on the stop member 48 to indicate the adjustment of the member 41 to a desired length of stroke or volume of liquid pumped per stroke, the scale shown being merely arbitrary and for purposes of illustration, it being obvious that the same can be calibrated in any manner convenient to the operator of the device.

Referring to Fig. 3, it will be noted that the cam 25 is shown as being keyed to the shaft 22 and as having a cam surface made up of a low portion 51, which is concentric with the axis of rotation of the cam and a high portion 58, that is concentric with the axis of rotation of the cam. Between said portions 51 and 58 is an outwardly curved portion 59, which is steep adjacent the portion 51 and becomes less steep as it approaches the portion 58. Beyond the portion 58 is a gradually inwardly curved cam surface 60, which is much longer than the outwardly curved portion 59, and which extends to the portion 51. With the roller 46 in the position shown in Fig. 3 and the cam rotating in the direction indicated by the arrow, the roller will first travel along the cam portion 60 to move the piston, or plunger, 31 to the right in Fig. l, causing a gradual decrease in the liquid capacity of the chamber 28 and causing discharge of the liquid through the outlet passage 34, if the valve controlling the same is open. This movement will continue until the concentric cam face 58 is reached, whereupon there will be no movement of the reciprocable member 31 until after said portion 58 has been passed and the portion 59 -of the cam surface has been reached, whereupon the spring 49, which has been previously compressed, will move the roller 46 toward the left, as shown in Fig. l, to keep said roller in engagement with the cam surface 59 and, with a maximum stroke of the reciprocable member, this will continue until the cam surface 51, concentric with the axis of the cam 25, is reached, whereupon the reciprocation of the member 31 will be again halted until the cam face 68 engages the roller 46, whereupon a repetition of the cycle of movements of the reciprocable member takes place. If the member 41 is adjusted to shorten the stroke of the plunger 31 from the maximum, then the roller 46 will leave the cam surface 59 dueto engagement of the stops, before the cam surface 51 is reached, and will not engage the cam surface 68 until a point thereon is reached beyond the junction of the came surfaces 51 and 60, dependent upon the position of the adjustable stop member 41.

The inlet connection 33 extends from an inlet valve 6|, which leads from a supply pipe 62. Said inlet valve is illustrated as being provided with a diaphragm 63, which, when in engagement with the seat 64, closes the valve so that no liquid can pass through the same in either direction, the inlet valve being shown as being closed in Fig. 1. It is, of course, understood that the valve seat 64 extends transversely of the passage through the valve 6| and that the diaphragm will engage the entire length of said seat to completely cut off the chamber thus formed at 65 in the valve 6| from the chamber formed at 66 on the other side of the seat 64. The diaphragm 63, preferably, comprises some compressible material, which, when in engagement with the seat 64, will form a tight seal between said diaphragm and said seat, even though small solid particles might adhere to the seat, the flexible material providing means for such small particles to bury themselves therein temporarily, so that these will not interfere with the sealing of the closure of the valve. The diaphragm is connected with a reciprocable member, such as the valve rod 61, in any well known manner, said valve rod having a collar 68 secured thereto and a compression spring 69 mounted between said collar and the valve body portion, Said rod-like member 61 also extends through a guide member 18 provided on the frame 20 and is provided with a bracket 1| secured to the end thereof, which is provided with bifurcations 12 mounting a pivot member 13 for the roller 14 that engages the cam 26.

Said cam 26 is provided with a highportion 15 and a low portion 16, which are concentric with the axis of rotation of the cam 26, said cam being, of course, keyed to the shaft 22. Inclined connecting portion 11 and 18 connect the low portion 16 and the high portion 15 of said cam. The compression spring 69 will hold the roller 16 constantly in engagement with the cam surfaces and the rotation of the cam 26 is in the direction of the arrow shown in Fig. 4. The inlet valve being closed in the position of the parts shown in Figs. 1 and 4, the roller 14 will be in engagement with the cam surface 15 until the inclined portion 11 is reached, whereupon the terval and will then again close quickly, and then again go through the same cycle of operations. The arrangement of the cams 25 and 26 on the shaft is such that the portion 15 of the cam 26 will be in engagement with the roller 16 during the entire time that the roller 66 is in engagement with the cam surface 68, and the roller 18 will still be in engagement with the cam surface 15 when the'cam portion 58 engages the roller 46. However, as the roller 46 continues in engagement with the cam portion 58 the roller 14 engages the cam. portion 11, opening the valve 6|, said valve being completely opened and the roller 14 in engagement with the cam portion 16 at the time that the roller 66 begins engagement with the cam portion 58 and this engagement of the cam portion 16 by the roller 14 continues until the cam portion 51 has engaged the roller 46. However, during the major portion of the engagement of the cam portion 51 with the roller 46, the roller 18 is in engagement with the cam portion 18, so that the valve 6! is moved to closed position before the roller 66 is engaged by the cam portion 60. Thus there can be no accidental backward flow of liquid through the inlet passage 33 and the valve 6|, and also no negative pressure created in the chamber 28 by means of the plunger 31, as during the entire suction stroke of said plunger 31, the inlet valve will be open, and during the entire discharge stroke of said plunger the inlet valve will be closed.

The outlet valve 19 is constructed in a similar manner to the valve 61 and is connected with the discharge pipe 88 in a similar manner, the seat 8| of said valve 19 cooperating with the diaphragm 82 in a similar manner to that pre-' viously described. The operating or valve rod 83 is connected with the diaphragm 82 in the same manner as is the rod 61 with the diaphragm 63 and the collar 84 and compression spring 85 I operate in the same manner as previously deroller will travel through a very short arcuate scribed. A guide lug 86 may be provided on the frame 20 for the rod 83 and. a bracket 1|, such as previously described, is provided thereon for mounting the roller 81 that engages the cam 21.

The cam 21 has a low portion 88, whichha's substantially the same arcuate extent as the high portion 15 of the cam 26, and a high portion 89, which has substantially the same arcuate extent as the low portion 16 of the cam 26. The inclined portions 90 and 9! connect the high and low portions of the cam, the roller 81 being held in engagement with all portions of the cam surface due to the provision of the compression spring 85. The cam 21 is related to the cam 25 in such a manner that while the roller 81 is in engagement with the cam portion 88 and the valve 19 is opened in consequence thereof, the roller 46 will be in engagement with the cam portion 60, and this engagement of the roller 81 with the cam portion 86 will continue until the cam portion 58 engages roller 86, whereupon the. outlet valve 18 will be closed due to engagement of the roller 81 with the cam surface 98, causing movement of the rod-like member 81 to the right, engagement of the cam portion 88 with the roller 81 holding said valve in closed position until the cam portion 91 is reached, whereupon the roller engaging the cam portion 8| under the influence of the spring will cause the valve 19 to be opened. Preferably, the cams 26 and 21 are so constructed that the valve 6| will not open until the valve 18 has already been closed and the valve 6! will close before the valve 19 is opened. Thus, while the cam portions 89 and 16 are of substantially the same arcuate extent, they are preferably not of exactly the same arcuate extent, the angle measuring the arc I6 being, preferably, slightly less than the angle measuring the are 89, thus assuring such operation of the valves as above referred to.

It will be obvious that with this arrangement of valve cams and driving cam for the reciprocable pumping member, the intake action of the pump wil be rapid and the discharge action of the pump will be relatively slow and gradual.

If this is of no importance, an eccentric can be used to drive the pump, or a cross head arrangement can be used. If either of these types of drives are used, the cams that operate the valves will, of course, have to keep the valves open through substantially half the stroke and the valves will have to open and close during the reversal of motion of the reciprocable member at opposite ends of the stroke. In an eccentric drive the rate of movement of the plunger, when the direction of movement reverses, is at first so very small that no harmful compression in the pump chamber will result therefrom. Also this can be taken care of in utilizing a diaphragm pump, the movement of the diaphragm being so small that any increase in the pressure of the liquid that might result momentarily could be taken care or by the diaphragm. Such an arrangement is shown in Figs. 6 to 10, inclusive, the frame therein being indicated by the numeral 20 and the pump chamber comprising the member 30, previously described, and a member 92, which is secured to the member 30 by securing elements 93 to clamp the peripheral edge of the diaphragm 95 between suitable seats on the member 30 and the member 92. Said member 92 is provided with guiding means for the reciprocable rod-like member 96, said guiding means comprising a tubular boss 91 provided on the spider-like body portion of the member 02. Said rod-like member 96 is secured to the diaphragm 95 in any suitable member so that a liquid tight chamber 98 is formed between the diaphragm and the member 30.

In order to protect the diaphragm 95 and prevent any undue flexing thereof adjacent the point of securement of the member 96 therewith, a pair of concave-convex disk-like washers 99 are provided on opposite sides of the diaphragm 95. The end of the rod-like member 96 remote from the diaphragm is secured in a socket I of an eccentric sleeve IOI. The eccentric sleeve and the adjustable eccentric provided in this form of the invention are shown more in detail in Figs. 9 and 10. The eccentric is mounted on a shaft 22, which is driven in the same manner as the shaft 22, previously described, and similarly mounted on the frame in the bearings 24. The eccentric I02 is keyed to the shaft 22, as will be evident from Figs. 9 and 10, while the eccentric sleeve has mounted within the same and between the eccentric I02 and said sleeve IOI a member I03 that has an eccentrically located opening therein of the same diameter as the eccentric I02, so that said eccentric I02 and said member I03 are relatively rotatable to adjust the relative positions thereof. The member I03 is freely rotatable within the eccentric sleeve I0 I and is shown as having an outwardly directed flange I04 and a detachable side plate I05 thereon forming a channel, this being merely illustrative, as any suitable means may be provided for holding the sleeve IOI and eccentric I03 assembled for rotation of said eccentric within said sleeve. The

directed flange I08 cooperating with the side plate I05 to confine the member I02 therebetween.

The member I03 i adjustable to diflerent positions relative to the member I02 by rotation of the member I03 relative to said member I02, by means of the handle I01, so as to obtain a different length of stroke for the member I06. A clamp I08 held in clamping engagement with the eccentric member I03 by means of a screw-threaded headed member I08 engaging athreaded opening in the eccentric member I02 holds the members I02 and I03 in adjusted position. In Figs. 9 and 10 the parts are so adjusted that the rod 96 will not reciprocate, but by rotating the member I03 through 180 degrees the maximum throw of the eccentric and stroke of the member 93 is obtained, and, of course, any adjustment between these two positions will give adjustments of the length of the stroke of the reciprocable member 96 between such maximum and minimum strokes. Any suitable scale can be provided for indicating the adjustment of the member I 03 relative to the sleeve IN to indicate the desired adjustment of the eccentric to get the desired throw thereof and the desired stroke of the reciprocable member 96, such as shown in Fig. 9. The particular clamping means for holding the parts in adjusted position may be varied as desired.

The inlet connection 33 is connected with a conduit I09 and the outlet connection 34 is connected with a conduit H0. The conduit I09 is provided with an inlet valve III and the liquid supply pipe 62 leads into said inlet valve. Said Inlet valve may be of any desired construction, but is shown to be the same type of valve as the outlet valve, or discharge valve, H2, which is interposed between the conduit H0 and the discharge pipe II3. Each of said valves is provided with a tapered valve H4 provided on a. rod-like member 5, and fixed in liquid tight relation to the member H5 is a disk-like member IIB, an accordion-like diaphragm member I52 being secured at one end to the member H6 and at the other end to the valve casing to provide for movement of the valve rod H5 and to provide at the same time a liquid tight connection between the valve casing and said valve rod. The guide members I0 and 86, previously, described, are provided for the valve rods H5, and said valve rods are provided with brackets II thereon, that rotatably carry the rollers 14 and 81, similar to those previously described in connection with Fig. l. The roller 14 engages a cam H1 and the roller 01 engages a cam IIB, both cams being keyed to the shaft 22, as will be obvious from Figs. '7 and 8. The rollers 81 and 14 are held in engagement with the respective cams by means of the compression springs II9 provided between the members II and the collars 68 and 84, provided on the two rod-like members I I5, in a similar manner as described in connection with Fig. 1.

In the position of the parts shown in Figs. 6, 7 and 8 the valve III is closed and the valve H2 is open. However, the position of the parts is such that the outlet valve member Ill in the outlet valve II2 will move into engagement with the seat I20 and the valve III will open upon slightly further rotation of the cams than that shown in Figs. 7 and 8. Also, when this takes place the diaphragm 95 will be flexed to the left to increase the capacity of the chamber 98 due to the fact that the position of the eccentric will be such that the rod-like member will be reciprocated toward the left, as viewed in Fig. 5.

The cam I H has a high portion I2I and a low portion I22, each concentric with the axis of rotation of the cam H1, and inclined portions 923 and I24 connecting said high and low portions, whil the cam II8 has a high portion I25 and a low portion I26 concentric with the axis of rotation of the cam H8, and inclined portions I21 and I28 connecting said high and low portions of the cam. The. rotation of the cams is in the direction of the arrows shown in Figs. 7 and 8.-

The roller 81, controlling the outlet valve, is in engagement with the low portion of the cam in the. position shown, but the inclined portion I28 is just ready to engage said roller 81 so as to move the rod II 5, controlling the valve I I2, to

the right to seat the valve II4 against the seat I and close said valve. This occurs substantially instantaneously, as the arcuate distance traveled by the cam H8 as said roller 81 rides along the inclined face I28 is very short, and this occurs at the time the eccentric causes the reversal of movement of the reciprocable member 96, at which time the movement of said reciprocable member in the direction of its length is very small compared with the amount of rotation of the eccentric that takes place.

It will be noted that the roller 14, at the same time that the roller 81: engages the low part I26 of the cam H8, is in engagement with the high part I2I of the cam I I1 and that this engagement continues for an interval after-the cam portion I28 engages the roller 81, and thus the inlet valve will remain closed until the outlet valve has been closed, whereupon the roller 14 will engage with the cam surface I24 and ride down along the same until the cam surface I22, or low portion of the cam II 1, engages the roller 14, at which time the inlet valve I I I is wide open, while the outlet valve is held closed due to engagement of the high part of the cam I25 with the roller 81. In a similar manner the valve II2 will remain closed until after the inlet valve has again been closed, due to engagement of the inclined portion I23 of the cam II1 with the roller 14 and the high portion I 2I thereof with said roller, this taking place when the reciprocable member 96 has reached the limit of its movement to the right, at which time the eccentric reaches a point at which such reversal takes place, but the movement of the member 96 in the direction of its length is very small in proportion to the amount of rotation of said eccentric. As a result there will be very little increase in pressure in the liquid in the chamber 98. due to the fact that both valves are closed while this slight movement of the member 96 is taking place under the action of the eccentric provided for rec procating the same.

In case the metering action of the pump does not have to be as accurate as would be the case where the forms of the invention shown in Figs. 1 to 5, inclusive, and 6 to 10, inclusive, are utilized, the apparatus shown in Fig. 11 may be utilized to feed said liquid. The feed pipe I29 is provided with a ball check valve I30 connected by the conduit I3I with an inlet connection I32, which leads into the liquid chamber I33 provided in the member 30, the outlet connection I34 connected by a conduit I35 with a ball check valve I35 leading to the discharge pipe I31. A diaphragm I38 is clamped between suitable faces on the member 30 and the member I39, which is provided with a threaded hollow boss I40 thereon, with which a cylinder MI is connected in liquid tight. engagement. Said cylinder l ii is, preferably, made of a very hard material, at least on the inner cylinclricalv surface thereof, providing the bore 542, said cylinder being, preferably, made of an alloy that can be nitrided, such as the alloy known as Nitralloy, manufactured by the Ludlum Steel Company, which is a low carbon-manganesesilicon-chromium-molybdenum-steel alloy, containing aluminum. This alloy can be surface hardened so as to have such an extremely hard surface that it will not be scored and will not gald when used in the manner illustrated. A plunger, or piston, I43 of a cylindrical character is, preferably, made in a similar manner and is similarly nitrided to surface harden the same, said piston fitting the cylinder so closely that liquid contained in the chamber between the diaphragm I38 and the body of the member I39 will not escape between the walls of the piston, or plunger, and the inner surface of the cylinder, with which it slidably engages. This is possible because, due to the extreme hardness of the materiaLsuch a close fit can be provided without having excessive friction. The reciprocable member can be driven in any of the ways previously described, or can be driven by means of a rod I44 pivoted thereto and connected with a cross :head'I45, so as to be adjustable relative to the center of rotation of the member I46 carrying said cross head, so as to vary the stroke of the piston, orplunger, I43 by movement of the member I 41 in the slot I48 provided in the member I45 rotating with the rotatable member I46.

A liquid, which is preferably thick, heavy and of high viscosity, such as a heavy-bodied grease, indicated at I49, is provided in the chamber between said diaphragm I38 and the wall of the member I39, said liquid being substantially noncompressible and being, preferably, of a character that it has such a viscosity that there can be no escape thereof between the wall I42 and the piston I43, said liquid, of course, entering the cylinder bore I42 that communicates with the chamber between the diaphragm I38 and the casing I39, and it being obvious that the diaphragm will be flexed, dependent upon the position of the piston I43, thus varying the capacity of the chamber I33 in accordance with the position of said piston I43, thus drawing in fluid through the check valve I30 and discharging it through the check valve I38 in a well known manner.

What I claim is:

l. A metering pump of the character described, comprising a pump chamber, a reciprocable member for varying the liquid capacity of said chamber, driving means for said reciprocable member, an inlet connection leading to said chamber, an inlet valve controlling supply of liquid to said chamber, an outlet connection leading from said chamber, an outlet valve controlling discharge of liquid from said chamber, said chamber being sealed whenever both said valves are closed, and means including cams positively driven by said driving means for opening and completely closing said valves in positively timed relation to each other and to the reciprocations of said reciprocable member, said driving means comprising meansfor moving said reciprocable member more rapidly in a chamber capacity increasing direction than in a. chamber capacity decreasing direc- 2. A metering pump of the character described, comprising a pump chamber, a reciprocable member for varying the liquid capacity of said chamber, means for reciprocating said reciprocable member including driving means, means for adlusting said means for reciprocating said member to vary the length of the stroke of said reciprocable member, an inlet connection leading to said chamber, an inlet valve controlling supp of liquid to said chamber, an outlet connection leading from said chamber, an outlet valve controlling discharge of liquid from said chamber, said chamber being sealed whenever both said valves are closed, and means including cams positively driven in synchronism with said driving means for opening and completely closing said valves in positively timed relation to each other, said driven means positively holding both said valves closed over predetermined intervals, the means for reciprocating said member including means for holding said reciprocable member stationary whenever said chamber is sealed.

3. A metering pump of the character described, comprising a pump chamber, a reciprocable member for varying the liquid capacity of said chamber, means for reciprocating said reciprocable member including driving means, means for adjusting said means for reciprocating said member to vary the length of the stroke of said reciprocable member, an inlet connection leading to said chamber, an inlet valve controlling supply of liquid to said chamber, an outlet connection leading from said chamber, an outlet valve controlling discharge of liquid from said chamber, said chamber being sealed whenever both said valves are closed, and means including cams positively actuated by said driving means for opening and completely positively closing said valves in positively timed relation to each other and to the reciprocations of said reciprocable member, said means positively holding both said valves simultaneously closed over predetermined intervals, said means for reciprocating said member including means for holding said reciprocable member stationary whenever said chamber is sealed.

4. A metering pump of the character described, comprising a pump chamber, a reciprocable member for varying the liquid capacity of said chamber, means for reciprocating said reciprocable member including driving means, an inlet connection leading to said chamber, an inlet valve controlling supply of liquid to said chamber, an outlet connection leading from said chamher, an outlet valve controlling discharge of liquid from said chamber, said chamber being sealed whenever both said valves are closed, and means positively actuated by said driving means for opening and completely closing said valves in positively timed relation to each other, comprising means including a cam for opening said outlet valve before the capacity decreasing stroke of said reciprocable member commences and holding said outlet valve open during the entire capacity decreasing stroke or said reciprocable member and means including a cam for opening said inlet valve before the capacity increasing stroke of said reciprocable member commences and holding said inlet valve open during the entire capacity increasing stroke of said reciprocable member, said means positively holding both said valves closed for intervals alternating with the periods during which said valves are alternately held open, said means for reciprocating said member comprising means for varying the length of the stroke of said reciprocable member between zero and full stroke without affecting the relation of said valve positions to the strokes thereof.

5. A metering pump of the character described, comprising a pump chamber, a reciprocable member for varying the liquid capacity of said chamber, means for reciprocating said reciprocable member including driving means, an inlet connection leading to said chamber, an inlet valve controlling supply of liquid to said chamber, an outlet connection leading from said chamber, an outlet valve controlling discharge of liquid from said chamber, said chamber being sealed whenever both said valves are closed, and means positively actuated by said driving means for opening and completely closing said valves in positively timed relation to each other, comprising means including a cam for holding said outlet valve open during the entire capacity decreasing stroke of said reciprocable member, and means including a cam for holding said inlet valve open during the entire capacity increasing stroke of said reciprocable member, said means positively holding both said valves closed for intervals alternating with the periods during which said valves are alternately held open, said means for reciprocating said member comprising means for holding said reciprocable member stationary during the intervals during which both said valves are closed and including means for varying the length of the stroke of said reci ocable member between zero and full stroke without affecting the relation of said valve positions to the strokes thereof, comprising resilient means for moving said reciprocable member in one direction and an adjustable stop for limiting such movement by said resilient means.

LYNDUS E. HARPER.

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