Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1987-09-29
1989-09-26
Pellegrino, Stephen C.
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
251 6, A61M 514
Patent
active
048697214
DESCRIPTION:
BRIEF SUMMARY
This invention provides means to control the flow of liquids and has particular relevance to controlling liquid flows that have to be regulated accurately and are small in volume. Examples of uses for the proposed apparatus is in the regulation of the flow of liquids through devices whereby blood or saline solution or like liquids are introduced intravenously to patients.
In one presently used apparatus for the above purpose liquid passes through a fixed size discharge orifice from a first chamber member into an elongated orifice of tapered shape in a second member, the maximum cross-section of the tapered orifice being smaller than the fixed size orifice. The tapered orifice discharges into a tube to deliver the liquid to its destination. The first member and the second member are movable one relative to the other to bring the fixed size orifice in the first member over different portions of the second orifice, the size of the portion of the second orifice exposed to the fixed size orifice can thus be varied and this determines the rate of flow of the liquid.
This form of apparatus has two major disadvantages. Firstly the liquid passes through the device and therefore sterilization of the parts of the device is required. Secondly, there are locations in the device where the liquid flows very slowly or may even cease to flow allowing blood co-agulation can occur.
In another form of device which operates much the same as the apparatus proposed by this invention, there is a plastic tube through which the liquid flows from a supply to a destination. The tube passes through a clamp means which by squeezing the tube transforms the circular bore of the tube into an elongated parallel sided slit with the width of the slit being the principal determining factor for controlling the flow rate of liquid through the tube. This has the disadvantage that as the slit becomes narrower the flow of liquid equates to a film with an increase in frictional drag which tends to inhibit flow. When the film is very thin blood co-agulation can readily occur. The use of the device usually involves constant supervision to ensure the required flow rate is maintained.
Another problem with known apparatus is the difficulty in accurately setting the flow rate where small flow rates are required and the apparatus acts as a restrictor to provide a thin film flow. Where the apparatus in being handled heat from the hand of an operator can cause expansion of the apparatus and when the apparatus returns to ambient temperature the flow rate will be different from that originally set by the operator. In addition, where thin film flows are caused by the apparatus and assuming no coagulation of the liquid flowing, there is a significant variation in the flow rate as the volume in the reservoir drops. In other words the flow rate is very sensitive to the hydraulic head acting on the liquid. This is negated to a large extent where thin film flows are avoided.
Despite the disadvantages outlined above which occur with the "squeeze" method for controlling the flow of liquid through a delivery tube there are compensating aspects. The system is simple, there is no sterilization problems as with the first known arrangement described above and the equipment is inexpensive. The present invention provides apparatus to overcome most of the disadvantages of the squeeze method by providing a minimum surface area of the bore of the tube for all cross-sections the tube adopts during the sqeezing process right down to the throttle condition where the flow is completely stopped. This is achieved by the progressive reduction of the cross-section of the bore of the tube while maintaining the cross-sectional shape of the bore of the tube substantially circular.
Broadly, the invention can be said to comprise a flow regulator for liquids passing through a resiliently deformable tube, the regulator comprises an elongated body part including a channel having a floor and two parallel sides which extend in the length direction of the channel beyond one end of the channel fl
REFERENCES:
patent: 2595511 (1952-05-01), Butler
patent: 3893468 (1975-07-01), McPhee
patent: 3918675 (1975-11-01), Forberg
patent: 4238108 (1980-12-01), Muetterties
patent: 4270725 (1981-06-01), Scott et al.
patent: 4662599 (1987-05-01), Attermeier
Lewis Ralph
O'Brien Anthony A.
Pellegrino Stephen C.
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