|Publication number||USRE30483 E|
|Application number||US 05/897,871|
|Publication date||Jan 20, 1981|
|Filing date||Apr 19, 1978|
|Priority date||Apr 19, 1978|
|Publication number||05897871, 897871, US RE30483 E, US RE30483E, US-E-RE30483, USRE30483 E, USRE30483E|
|Inventors||Lamont J. Seitz, Louis Jerg|
|Original Assignee||Baxter Travenol Laboratories, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (1), Classifications (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The pipette, or metering syringe, of the invention as will be described herein, is useful in conjunction with a blood clot timing mechanism of the type described, for example, in copending application Ser. No. .[.730,832.]. .Iadd.738,382. .Iaddend.However, it will become evident as the description proceeds that the metering syringe of the invention has general utility whenever a precisely metered amount of a liquid is to be introduced into a receptacle, or the like, for test or other purposes.
The blood clot timing system described in the aforesaid copending application, in one of its aspects, is capable of detecting clotting in a blood or plasma sample, this being achieved by the application in special equipment of a test for determining the prothrombin time. The aforesaid test involves the addition of a measured amount of the patient's blood, or plasma, to a reagent, such as thromboplastin; and the subsequent addition of a measured amount of calcium chloride, or other source of soluble calcium ions, to the solution. As described in the copending application, a timer in the equipment is started at the precise time the calcium chloride is added to the solution.
The metering syringe of the present invention is particularly suited for use in conjunction with the test described in the preceding paragraph. The syringe may be equipped with a replaceable, disposable tip so that it may be used to add different blood samples to different receptacles of reagent, and also to add the calcium chloride, all without fear of contamination. For each operation, the previous tip is discarded and replaced by a new sterile tip.
The improved metering syringe of the invention is also equipped with an improved simplified purging mechanism, which is effective to provide an additional discharge stroke as compared with the intake stroke. This additional discharge stroke enables the last drop of the liquid, which was drawn into the instrument by the intake stroke, to be discharged during the discharge stroke. In this manner, the exact quality of liquid drawn into the syringe instrument is discharged, and also the instrument is completely purged.
The improved syringe to be described herein is also equipped with electrical contacts which are closed at the end of the discharge stroke. These contacts are useful, for example, in conjunction with the equipment of the copending application to control the commencement of the timer the instant the calcium chloride is added to the solution.
The invention provides, therefore, an improved syringe type of instrument which is capable of introducing a precisely measured amount of liquid into a receptacle, and which includes a purge control so that all the liquid drawn into the instrument is discharged during the discharge stroke. The instrument to be described is extremely simple in its construction, and yet it is precise and accurate in its operation. The instrument to be described, moreover, is capable of closing an electric circuit at the termination of its discharge stroke, for reasons such as mentioned above.
The instrument of the invention finds particular utility in blood tests, such as referred to above. This is because precision is an essential requirement in such tests, as is freedom from contamination. However, it will become evident as the description proceeds, and as mentioned previously herein, that the instrument of the invention has general utility.
FIG. 1 is a side view of a pipette, pipetter, or metering syringe, incorporating the concepts of the present invention;
FIG. 2 is a side section of the instrument of FIG. 1, taken essentially along the line 2--2 of FIG. 1; and
FIG. 3 is a fragmentary section, similar to the section of FIG. 2, but turned through 90° about the longitudinal axis of the assembly to reveal other operating components.
As shown in FIG. 1, the improved syringe of the present invention comprises essentially an outer tube 10, and an elongated hollow member 12 threaded to one end of the tube. A push button 14 protrudes through the other end of the tube 10. A replaceable plastic tip 16 is frictionally placed on the extremity of the elongated hollow member 12. The plastic tip may be replaced after each use, and a quantity of such tips may be supplied with the instrument, all in a sterile condition. The instrument also incorporates an electric cord 18 and plug 20.
As will be described in more detail subsequently, the button 14 may be moved into the tube 10 until a yieldable stop is engaged, and the tip 16 may then be placed in a receptacle of an appropriate liquid. Then, when the button is released, a precisely measured amount of the liquid is drawn from the receptacle into the replaceable plastic tip. This tip contains all of the liquid so that there is no liquid contamination of member 12. The liquid may then be discharged as a pressurized stream into another receptacle from the replaceable tip 16, by again depressing the button 14.
When the yieldable stop is engaged during the discharge stroke, the button 14 may be pushed still further as a purge control, so that the last drop of liquid may be discharged through the end of the replaceable tip 16. This latter operation also closes electrical contacts within the instrument, so that the cord 18 and plug 20 provide an electrical control for associated equipment, as referred to above.
As shown in FIG. 2, for example, the outer tube 10 encloses an elongated rod 20 which is movable along the longitudinal axis of the tube. The rod 20 may be composed, for example, of stainless steel. In a constructed embodiment, the rod 20 has a diameter of 1/8 of an inch.
The push button 14 is threaded to one end of the rod 20, as shown. A snap-ring 22 is positioned in a peripheral channel in the bore of the tube 10 at an intermediate position within the tube. The snap-ring 22 acts as a stop, and also acts as a retainer for holding the various components of the assembly within the outer tube 10.
A switch supporting bracket 24, which has a generally tubular configuration, is mounted in coaxial relationship with the rod 20, and one end of the bracket 24 bears against the snap-ring 22. The other end of the bracket 24 is counter-bored to receive a first spring 26. The spring 26, for example, is coiled around the rod 20, and one end bears against the bracket 24, and its other end bears against the inner end of the push button 14. Therefore, the spring 26 serves to bias the rod 20 to the right in FIG. 2 with respect to the tube 10. A retainer ring 28 is mounted on the rod 20, and this retainer ring engages a stop washer 30, and biases the stop washer 30 against the ring 22, as the spring 26 biases the rod 20 to the right in FIG. 2.
Another retainer ring 32 is mounted on the rod 20 on the opposite side of the washer 30, and this ring 32 is moved against the washer 30, as the button 14 is depressed into the tube 10 to move the rod 20 to the left in FIG. 2. The washer 30 serves as a yieldable stop for the retainer ring 32, since the washer is biased against the ring 22, by a second spring 36. The second spring 36 is interposed between the washer 30 and a bushing-like retainer 38 which is interposed between the elongated hollow member 12 and the other end of the spring 36. An O-ring 40 serves to seal the member 12 to the rod 20.
Therefore, as mentioned above, the washer 30 serves as a yieldable stop for the retaining ring 32. That is, when the button 14 is pushed into the tube 10 to shift the rod 20 to the left in FIG. 2, the movement may continue until the retaining ring 32 moves against the washer 30. Then, an additional force must be applied to the button 14, in order to move the rod 20 further, during which movement the retaining ring 32 moves the washer 30 against the additional bias afforded by the spring 36.
Therefore, in the operation of the instrument, the button 14 is first moved into the tube 10, until the retaining ring 32 moves against the washer 30. Then, the button 14 is released, so that the rod 20 moves to the right drawing a precisely measured amount of liquid into the replaceable disposable plastic tip 16 of FIG. 1. Then, the liquid in the replaceable tip 16 may be subsequently discharged by again moving the rod 20 to the left in FIG. 2, by depressing the button 14 into the tube 10. During this discharge operation, the rod 20 is moved beyond the yieldable stop afforded by the washer 30, so that the last drop of fluid may be discharged in a purging action.
A pair of resilient switch contacts 70 and 72 are supported on the bracket 24 by means, for example, of appropriate screws 73 and 74. The bracket 24 may be composed of electrical insulating material, so that the switch contacts 70 and 72 are normally insulated from one another. The contacts 70 and 72 are connected to the electric cable 18 of FIGS. 1 and 3 by respective electric leads 76 and 78.
A bridging electrically conductive member 80 composed, for example, of brass is mounted as a ring about the inner end of the button 14, the inner end having a reduced diameter, as shown. During the initial operation of the instrument, during which the rod 20 is not moved beyond the yieldable stop 30, and during which liquid is drawn into the replaceable plastic tip 16, the bridging member 80 does not engage the switch contacts 70 and 72. However, during the subsequent discharge operation, during which the rod 20 is moved fully to the left beyond the yieldable stop provided by the washer 30, the conductive member 80 moves between the switch contacts 70 and 72 to provide a bridging connection therebetween. This, therefore, provides a control corresponding to the discharge of the last bit of fluid from the instrument. Such a control, as mentioned, is appropriate in equipment, such as described in the aforesaid copending application.
It will be appreciated that the assembly shown in FIG. 2, for example, is exceedingly simple, and the snap-ring 22 serves as the sole support for all the components within the tube 10. Also, the metering accuracy of the instrument depends only on the diameter of the rod 20, on the spacing between the retaining rings 28 and 32, and on the thickness of the washer 30. All these dimensions and parameters can be established to extremely close tolerances. Since the metering accuracy of the instrument is independent of other dimensions and parameters, a high degree of precision is achieved in a relatively simple way and by relatively simple and inexpensive components.
The instrument of the invention, therefore, is precise and accurate in its operation, yet it is relatively inexpensive and may be constructed in a relatively simple manner. The instrument is advantageous, since it provides a convenient and simple means for transferring precisely metered amounts of liquid. In addition, the illustrated embodiment is capable of providing appropriate electrical controls which are required in many types of instruments.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US2530909 *||Nov 14, 1947||Nov 21, 1950||Carl A Nisson||Mechanical pipette|
|US2959964 *||Jul 24, 1956||Nov 15, 1960||Nat Children S Cardiac Hospita||Pipette adaptor|
|US3244009 *||Aug 22, 1963||Apr 5, 1966||Becton Dickinson Co||Automatic pipette|
|US3302462 *||May 25, 1964||Feb 7, 1967||Dow Chemical Co||Pipetting device with stop mechanism|
|US3343539 *||Oct 22, 1964||Sep 26, 1967||Moorhouse Turkey Hatchery Inc||Piston type artificial insemination syringe having stroke adjusting means|
|US3494201 *||Aug 16, 1968||Feb 10, 1970||Oxford Lab||Pipetting system|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US20140091110 *||Sep 30, 2013||Apr 3, 2014||Brightwell Dispensers Limited||Dispensing device|
|U.S. Classification||73/864.18, 422/925|