CA1073778A - Safety valves for protection against liquid contamination - Google Patents

Abstract

Abstract of the Disclosure A safety valve which may be used in a pipette or in medical or biological equipment such as collection bottles, employs a carrier which is inserted in a flow line and contains a material which swells in the presence of an unwanted fluid to block the line and provide protection against contamination.

Description

~73778 'rhis invention relates -to safety valves ~or prot~ction a~ai~s-t :eluid cont~mination particularly in chemical, hlolo~ica~and bacteriological equipment and instrumentation and to apparatus incorp~rating sueh valves.
One speci~ic use for these safety valves is in surgical colleetion bottles, and another is in pipettes.
Where bacteriological samples are to be dispensecl it is important that traces o~ the sample do not reaeh and - cause contamination in areas where they are nob wanted.
For e~ample it is vital that wi-th manual pipettin~, traees of a toxic sample are not sucked up into the mouth; and in mechanical devices it is important that pumping and feedlng mechanis~s are not contaminated in use. Where mechanisms are con-taminated there is ris~ o-f traces of one sample being ~ 15 earried over to the next, and the need ~or very thorough `~ eleaning between eaeh operation. With medical equip~ent, , such as surgical collection bottles for body fluld,~ the ; possibility oE infected liquid being earried into - mechanical parts and giving rise to further in~eetion is something to be avoided; and ln equipment ased in ~ood ~ ;
production baeteriological hazards should not be allowed to arise. The invention is eoneerned with safeguarding - against sueh problems. ~ ~ `
Aeeordingly the invention provides a saEety valve eonsisting o~ a hollow earrier arran~ed for insertion in a ~low line and eontaining a material which allows Elow ; through said earrier oE one Eorm oE Eluid, but whieh in `~
the presenee of a seeond Eorm of EluLd swel]s to b]ock said earrier and preven-t -fur-ther flow.
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. ' ' , ' ln lts simplesG form the material is arran~ed go as to allow air or oth~ ases to flow through, but in the presence of a l-iquid, the material absorbs that liquid, swells and blocks the carrier.
r~he invention ~inds particular application in surgical collection bottles for body fluid, where it can replace the conventional ball ~loat valve resulting in a cheaper, and in some cases disposable, device.
The material may be a packing o~ granu1ar or powdered water-soluble polymeric material, for e~amplé gelatine, sodium alginate or agar, which allo~s passage o~ air (even when the air is c3amp). I~ liquid water 0nters the device, however, the polymer immediately swells and blocks the carrier, after which neither water nor air can pass.
Certain chemically modified cellulose derivatives in granular form are particularly effective as the material :
~n the carrier which swells in the presence o~ water.
A particular example is the Briti~h Celanese product ..v Courlose p.350 which is powdered or granular form o~ -~` 20 purified sodium carbox~methyl cellulose (a 1% solution has a viscosity o~ 300 to 450 cps). Staroh derivatives may also be used~
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he device may also be used when both fluids are ~ liquids. For e~ample i~ the material in the carrier is `~ 25 in the form of hydrocarbon polymer granules, e.g. rubber~
a flowing stream of ~at0r will be stopped by the presence of a hydrocarbon liquid in that stream. By selection o~ -`
i~ a different material the converse can be achieved i.e. a flowing stream o~ hydrocarbon liquid ~ill `be s-topped when signieicant traces of water appear.
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It ~ilL be appreciate(l that in selecting a material ~or use in the saCety valve according to the invention, only a s:in~le clearly recognisable property, namely swelling ancl blocking in the presence o~ the anwanted fluid, has to be identi~ied in the material. Thus the material can be selected Yery easily by trial and error, or t~rough recourse to well-known Chemical textbooks, e.g.
Kirk-Othmer Encyclopaedia O:e Chemical Technology Vol III
p 599 et seq ancl particalarly page 622. It will be unders-tood also, that the arrangement should ensure that the valve does bloc~ when required under the normal conditions of use. To ensure this, excessive temperatur~s, pressures or other conditions o e use which mig~ wash or dissolve the material away al-together should not be ~ - ~
employed, and in some cases mechanical restraint should be included, ~or~example cottonwool or other iner~ plugs, or other mechanical constraint which allows ~low o~ the `
normal fluid but retains the blocking ~aterial in place.
Several embodiments of the invention will now be described by way of e~ample with reference to the .
accompanylng diagrammatic drawings in which: ;
Fi~ure 1 shows a perspective view of an insert;
Figure 2 is a sectioned side elevation o~
a surgical vaouum pump collection bottle;
Figure 3 is a sec-tioned side elevation of another form O:e collection bottle;
Fi~ure A is a sectioned sicle e:Levation o e a third ~orm O-e collection bottle;

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Figure 5 is a perspec-tivc view o~ a i~our-th eorm of collection bott]e; ', Figure 6 is a perspective view o~ a ~lodi~ied pa~t of the Figwre 5 bottle;
Fi~ure 7 and Figure 8 show views of a pipette using an insert.
Referring to Figure 1, a safety valve in accordance with the invention comprises a hollow carrier 1 which is in tubular :form and there~'ore capable o~ insertion, i~ a flow line. ~he carrier contains a material 2 consisting o~ loosely packed granular water soluble polymeric material. Suitable materials are gelatine? sodium alginate, and agar for protection o~ a flowing gas against ingress of liquid. Courlose p.350 made by British ~;~
~¦-- Celanese Limited was used in the present example. The ` granular material is maintained in position by cotto~wool ' ,. .
plugs 3 at each end. With alternative shapes o~ carrier - the material is kept in place'by suitable shaping o~ the internal walls of the hollow carrier rather than~the ' cottonwood plugs.

'~ ~he carrier described in Figure 1 may be used i~
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~' numerous dif~erent applications in ~oods, medical'and ~, similar equipment where fluids ~low, to sa~eguard against ;1 25 accidental contamination. Two sach, one for medica~ ,, collection bo-ttles and the other ~or pipettes will now be described.

-' Figure 2 shows a glass collection bottle 4 ~or use in conjunction with a swrgical vacuum pump in pumping body ~luid ~rom a patierlt after an operation. In u~e a vacuum ' .

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~:373778 pu~p w:ithdraws air at -the location of arKow ~ while i`he .reduced pressu:r~ ~ithirl the container resul-ts in bo~y liquid being withdrawn into the con-tainer in the d:irection o~ arrow B.
Such vessels are well known and conventionally a float valve near the top o~ the container acts as a protection ' device to protect ~or the situa-ti.on when the liquid level . ~ithin the container reaches -the top, to ensure that liquid is not then drawn into the vacuum pwmp along the path o~ ~
arrow A.
' The conventional valve assembly is replaced in àccordance with the invention by an insert 5 constructed ~ internally as shown in Figure 1. This is cheaper and ~ :
: more convenient in use than the conventional ~loat valve~
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~i In practice, operation o~ the system will~not normall~ .; '' .. result in operation of the safety valve 5, the operator ~ .
observing the li~uid level and switching o~ the pump and -~
~ replacing the bottle when liquid level is near but not :: 20 quite at the top. When however the liquid level does ':':
':` reach the top o~ the container and start to ~low in the : direction o~ arrow A, it flo~s into the safety valve 59 ~'. causes the granulated gelling material 2 to a'bsorb liquid9 swell and block off further flow along the vacuum.;line.

2~ This ensures that no conta~ination o~ the vacuum pump ' takes place and it is then a simple matter to insert a :.` new valve 5 and clean out the bottle ~or ~urther use.
, '.' The sa~ety valve is a cheap and easily replaceable item.
Figure 3 shows a si.mi'lar system where -the container is a plastics 'bot-tle. Thi.s has become possible s:ince : - 6 -,~

, ~C9737~8 ster111~ation and cleaning o~' the relatively e~pensive valve ~echanism has been eliminated.
Figure 4 shows a system where the bottle has been replaced by a disposable collapsible bag 6. This disposable bag is suspended within an outer container 7 and ; the air line system i9 arranged so that the ~le~ible bottle 6 automatically opens out in use. This is achieved by ~eeding the outlet of the air line from the insert~5 to the space between the inner container 6 and the ou-ter container 7, and thence to the vacuum pump. Since there is a slight drop in pressure across the insert 5, this means that there is a greater vacuum on the outside of the inner container 6 than on the inside and therefore this causes the containér to open out as soon as the vacuum pump is switched on.
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Figure 5 show~ a -further form in which the outer ~ -container is no longer needed nor are the measures ~or .1 . : ~:
opening out the ba~ re~uired. In this case the bag has ~ ~ -. j , .
i loops 8 welded at its corners and the bag is loop~ed over a ~ ~;
holder 9 havin~ upstanding bars 10 which are inserted into the loops 8. ~hus the bag lS held open dur mg use. . ;~
In the arrangement shown in Fi ure ~ the bag is disposable while a lid including the pipe connections and - the valve 5 i9 a permanent component. Figure ~ shows a varian-t on the Figure 5 arrangement where the connection~
and thé valve~5 are all part of ~the disposable sy~tem~
Figu~ 7 and 8 show the valve as applled to a hand pipette. In this case the pipette has a mouth piece li which incorporates the valve and the water swellable granules which ~re located in a hollow part o~ the mouth piece at the location 12. In operation the mouth piece '';~
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is simply slipped onto the end o:~ a standa:rd l):ipe-tte and if` the oper~to:r sucks liquid up too Iar it blocks o~ the pipe~te and harm-~ul liquids eannot ente:r the operator's : mouth. When the mouth plece is blocked it can either be di sca.rded, or it can be cleaned ou-t and re~illed with material in the cavity 12 :Eor :eurther use.

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Claims (2)

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

1. A safety valve for protection against fluid contamination comprising a hollow carrier adapted for insertion in a flow-line and containing a valve element consisting essentially of loosely packed swellable hydrocarbon polymer granules which allows flow through said carrier of a stream of water, but which in the presence of a hydrocarbon liquid swell to block said carrier and prevent further flow.

2. A pipette incorporating a safety valve according to claim 1 located between a mouthpiece and a collection chamber so as to protect the mouthpiece and user from liquid contamination.