US 3846077 A
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Description (OCR text may contain errors)
Nov. 5, 1974 P. QHRINGER LIQUID SAMPLE COLLECTION TUBE 2 Sheets-Sheet 1 Filed Sept. 18, 1972 W74 P. OHRENGER 3,84
LIQUID SAMPLE COLLECTIQN TUBE Filed Sept. 18, 1972 2 Sheets-Sheet a United States Patent i US. Cl. 23259 12 Claims ABSTRACT on THE nrscLosunn A collection container for isolating a liquid sample from a specimen container consisting of an elongated cylindrical tube with an outside diameter slightly smaller than the specimen container, and having a hollow neck formed at one end of the tube. A circular disc is formed radially on the neck for slidably engaging the internal cylindrical walls of the specimen container and a shoulder is formed on the neck adjacent to the circular disc for engaging and supporting at least a portion of the circular disc. The container also includes a filter disposed in said neck aperture to limit the fluid flow from the tube.
This invention relates to an apparatus for isolating the formed elements of blood fro-m the serum or plasma after these elements have been separated.
More specifically, this invention relates to an apparatus for filtering the serum or plasma from a separated blood sample.
When blood specimens are tested in clinical laboratories, it is frequently necessary to obtain a cell-free sample of blood serum or plasma after the serum has been sep arated from the suspended cellular material. The cellular material or blood cells are separated preferably by centrifugal force driving the cells to the bottom of the tube containing the blood specimen. The serum or plasma which remains in the top portion of the tube is then removed and clinically tested.
It is important to remove the serum or plasma within a short time after the blood cells are separated since these cells will begin to liberate potassium and other contaminants which may interfere with the tests to be performed. In a clinical laboratory where many hundreds of blood tests are made each day, it is also desirable to provide a quick and accurate device which can remove or isolate the serum or plasma after it has been separated from the blood cells before the blood cells liberate other contaminants.
Blood samples are generally taken in a specimen tube such as a Vacutainer manufactured by Becton-Dickinson Company. After these samples are delivered to the testing laboratory, they are mechanically centrifuged to separate the blood cells from the clear liquid in the sample. The serum can then be drawn off with a conventional syringe, decanted by pouring the serum off, drawn off by pipettes, or collected by using a plunger-like apparatus which is inserted into the specimen tube. Over the past few years, a great many advancements have taken place in the development of plunger-like tubes for removing the serum or plasma from the blood sample. In one such device, a capillary tube is disposed within the plunger so that the clear sample will be pushed through the capillary tube and dispensed either in a separate collection tube, or within a collection tube connected to the plunger. In another plunger-type device, needles are inserted through the plunger and a membrane connected to the opposite end of the collection tube, so that after the collection tube is inserted into the sample tube, one of the needles can be removed to entrap the clear sample within the collection tube. In a further plunger-like device of the prior patented art, the plunger includes small valves consisting of over- 3,846,077 Patented Nov. 5, 1974 lapping elastic material to serve as one-way valves to permit the clear sample to enter the collection tube when the collection tube and plunger are inserted into the specimen tube. This plunger-like device further includes a second one-way valve capping the opposite end of the collection tube so that when the tube is withdrawn from the specimen tube, the entrapped air in the collection tube together with the action of the one-way valves will prevent the clear sample from returning to the specimen tube. All of the plunger-like collection devices of the prior patented art suffer from the disadvantages that they are expensive to manufacture and assemble, they are diflicult to withdraw from the specimen tube due to the suction, and require additional functional parts to accomplish the separation of the clear liquid from the blood sample.
Accordingly, the present invention provides an improved plunger-like liquid separation device and filter combined whereby the plunger mounted on the end of the collection tube seals only during the insertion of the collection tube into the sample tube. When the collection tube is withdrawn from the sample tube, it no longer seals so that substantially no suction is created and the clear sample remains in the collection tube without the aid of additional one-way valves to prevent the sample from being removed. In a preferred embodiment, the collection tube and plunger are an integrally formed part which include a shoulder flange mounted adjacent to the plunger so as to support the body of the plunger while it is inserted into the specimen tube. The plunger, being constructed of a very thin plastic material has no support on its front surface so that it effectively collapses when it is withdrawn from the specimen tube. A filter is also concentrically disposed within the body of the plunger at the neck of the tube so that the liquid is filtered while it passes into the collection tube and is restricted from returning to the specimen tube as the collection tube is withdrawn.
It is therefore an object according to the present invention to provide a blood serum collection tube which utilizes a one-way plunger in combination with the collection tube for isolating the serum from a blood sample.
It is another object according to the present invention to provide a serum collection tube which is simple in design, inexpensive in cost and efiicient in operation.
Other objects and features of the present invention will become apparent from the following detailed description considered in connection with the accompanying drawings which disclose the embodiments of the invention. It is to be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention.
In the drawings, wherein similar reference characters denote similar elements throughout the several views:
FIG. 1 is a perspective view of the collection tube according to the invention;
FIG. 2 is a cross-sectional view taken along section 2-2 of FIG. 1;
FIG. 3 is a detailed cross-sectional view of the invention of FIGS. 1 and 2 shown inserted into a specimen tube;
FIG. 4 is a further detail of the embodiment of FIG. 3 being withdrawn from a specimen tube;
FIG. 5 illustrates the sequence of operations of removing the liquid from the blood sample contained in the specimen tube;
FIG. 6 discloses the use of end caps for closing the ends of the collection tube; and
FIG. 7 shows a further end cap which serves also as a stand for supporting the collection tube.
Referring to FIGS. 1 and 2, there is shown the collection tube having a plurality of graduations 17 formed along the walls of the tube preferably in units of measuremeat such as milliliters. At the top of collection tube is formed an air escape opening 18.
At the bottom end of collection tube 10 is formed a funnel-like taper 11 terminating in a hollow plunger. The plunger has a cylindrical neck or base 12 coupled to the end of funnel 11 and includes a cylindrically projecting shoulder 14 mounted adjacent to and partially covering a cylindrical disc or wafer 13. In the hollow center of the plunger is disposed a filter 15 formed of a sponge-like porous material, such as foam plastic. An inwardly pro jecting radial flange 16 formed at the end of cylindrical base 12 partially covers filter 15 so that in a preferred embodiment, the filter will not accidentally become dislodged. At the top portion of plunger base 12 is a further inwardly directed annular flange 9 which prevents the filter from accidentally entering the collection tube.
Referring to FIG. 3, the collection tube is shown inserted into a specimen tube, such as a Vacutainer manufactured by Becton-Dickinson Company. The specimen container includes a separated blood sample. The serum or plasma 19 is forced, as shown by the upwardly directed arrows 21, through filter 15 to become the clear fluid 22 collected in tube 10. The downward pressure of the collection tube also forces separated blood sample 19 to overcome the fluid resistance of filter 15 and thereby enter into collection tube 10. The downward motion of collection tube 10 maintains plunger disc 13 in sealing contact with the internal walls of specimen container 20 since shoulders 14 immediately behind disc 13 maintain a pressure against the disc so that it serves as a sliding seal and plunger to prevent any of sample 19 from passing around the disc into the other side of the plunger. Collection tube 10 is easily inserted into specimen tubes by placing an index finger at the top of the collection tube and forcing it downward so that as the filtered specimen enters the collection tube, the air displaced by the entering fluid can easily leave the tube through opening 18 as shown in detail in FIG. 2.
Referring to FIG. 4, when a sufiicient quantity of filtered specimen 22 has been collected in collection tube 10, the tube can be lifted upward in the direction of the vertical arrows so that circular plunger disc 13 deflects in the opposite direction away from support shoulder 14, thereby breaking the seal originally formed with the inner walls of serum tube 20 to permit air to enter around the disc and begin filling in the expanding space on top of the blood specimen. Because of the fact that the plunger contains very little or no strength to resist the withdrawal of the collection tube from the specimen tube, there is little or no suction created even when the collection tube is rapidly withdrawn so that the collected serum or plasma 22 is maintained within the collection tube by the fluid resistance of filter 15.
The complete cycle of isolating the plasma or serum from a blood sample is shown pictorially in FIG. 5. In the first diagram on the left, collection tube 10 is moved downwardly to engage specimen tube 21 which contains the blood sample having separated cells 23 from clear plasma 19. Moving in the direction of arrow 24, as the collection tube with its plunger moves downwardly forming a seal with the inner walls of specimen tube 20, air is initially forced through the filter before the plunger engages liquid 19. In the next step after arrow 26, fluid enters the collection tube by overcoming the fluid resistance of the filter and begins to fill the lower inside cavity of the tube. In the next step after arrow 28, whereby a suflicient quantity of liquid 19 has been collected within the tube, the tube can then be withdrawn from the specimen container as shown after arrow so that the plunger inverts within the specimen tube and breaks its sealing contact to permit air to replace the collected specimen as the collection tube is withdrawn. As shown in the final diagram following path 34, the entire collected specimen remains within the collection tube after the collection tube is separated from the specimen tube.
Referring to FIG. 6, there is shown collection tube 10 with a cylindrical plunger cap 35 consisting of a cup-like container which is adapted to seal the end of the collection tube While further tests are to be performed on the collected specimen. Likewise, the open end of collection tube 11} can also be closed by means of cap 36 which includes an annular groove 37 adapted to fit over the cylindrical rim of the tube and completely enclose opening 18. This will prevent air from affecting the chemistry of the contents of the collection tube if the tube and its specimen have to be stored for any length of time.
Referring to FIG. 7, there is shown another embodiment of a plunger cap consisting of a cylindrical receiving tube 38 which is closed at its bottom end and expanded by a further flange 39 which forms a stand for maintaining the collection tube in a vertical stable position. The stand and cylindrical receiving tube are preferably formed of a single integral piece of resilient material, such as plastic or nylon.
Collection tube 10 is preferably constructed from a single piece of plastic material, wherein the graduations, and the entire plunger assembly are molded in a single piece construction before the filter is inserted into the plunger. Because the collection tube of the present invention is made from a single piece of molded plastic material so that the only additional step of manufacture includes the insertion of the filter, it is very inexpensive to manufacture and therefore disposable after use because of its low cost. The plastic material may be any soft or resilient plastic, such as PVC, polyethylene or polypropylene. The diameter of the collection tube and its graduations would be preferably slightly smaller than the internal diameter of the specimen tube and plunger disc or Wafer 13 would be slightly larger in diameter than the internal diameter of the specimen tube so as to form a seal when it contacts the inside walls of the specimen tube. In a preferred embodiment of the invention, the collection tube has an outside diameter of approximately .5 inch and the diameter of the plunger disc is approximately .57 inch. The edge of plunger disc 13 is approximately .01 inch in thickness and is separated from its supporting surface 14 by approximately .01 inch. The collection tube is preferably approximately 4 inches in length to accommodate up to about 10 ml. in quantity.
The filter is preferably constructed from a resilient cellular material, such as foam plastic, so that it can be slightly compressed when it is inserted into the neck or base of the tube. It can also be cemented into the tube opening if mechanical retaining means are not used.
While only a few embodiments of the present invention have been shown and described, it will be obvious that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.
What is claimed is:
1. A collection container for isolating a liquid sample from a specimen container comprising:
an elongated cylindrical tube having an outside diameter smaller than the specimen container, and including an aperture at one end communicative with said tube; circular disc means formed radially at said aperture end of said tube for slidably engaging the internal cylindrical Walls of the specimen container;
abutment means formed on said tube adjacent to said circular disc means for engaging and supporting at least a portion of said circular disc means; and
fluid resistance means disposed in said aperture to limit the fluid flow from said tube so that when said tube is inserted into the specimen container, said circular disc means will contact and be supported by said abutment means to form a seal against the internal specimen container walls and when said tube is removed from the specimen container, said circular disc means will separate from said abutment means to release the seal from the container Walls.
2. The collection container as recited in claim 1 additionally comprising a neck formed at the aperture end of said elongated cylindrical tube, said neck having a smaller diameter than said tube and surrounding said aperture.
3. The collection container as recited in claim 2 further comprising a tapered funnel joining said neck to said cylindrical tube.
4. The collection container as recited in claim 2, wherein said fluid resistance means comprises a filter partially sealing the aperture of said neck.
5. The collection container as recited in claim 1, wherein said cylindrical tube includes spaced-apart graduaations formed in said tube.
6. The collection container as recited in claim 1, wherein said elongated tube includes at least one air escape opening formed at the opposite end of said tube.
7. The collection container as recited in claim 4, wherein said neck additionally comprises filter retaining means formed in the neck aperture for demountably retaining said filter.
8. The collection container as recited in claim 1 further comprising a plunger cap for enclosing and sealing said circular disc means.
9. The collection container as recited in claim 2, wherein said circular disc means comprises a flexible wafer disposed on the end of said neck and said fiange means comprises a circular shoulder disposed adjacent to said water between said Wafer and said tube.
10. The collection container as recited in claim 6 additionally comprising an end cap for closing the opposite end of said cylindrical tube, said cap including an annular channel for enclosing the cylindrical rim of said tube and the air escape opening.
11. The collection container as recited in claim 1 additionally comprising a second plunger cap having a cylindrical receiving tube closed at its bottom end, and an enlarged flange formed at the bottom end of said receiving tube for supporting said tube in a vertical position.
12. The collection container as recited in claim 1 wherein said abutment means comprises a cylindrical projecting shoulder.
References Cited UNITED STATES PATENTS 3,493,503 2/1970 Mass 23-230 B 3,508,653 4/1970 Coleman 210-Dig. .023 3,586,064 6/1971 Brown et al 23-259 X 3,481,447 2/1969 Farr 23-259 3,512,940 5/1970 Shapiro 210-359 X 3,661,265 5/1972 Greenspan 210-359 3,693,804 9/1972 Grover 210-359 RONALD E. SERWIN, Primary Examiner US. Cl. X.R.