Bulb-operated pipet

Abstract

A liquid transfer pipet consisting of a tubular barrel having an inlet conduit portion at one end and a reduced stem at the other end having a capillary bore. An apertured operating bulb is slidably and sealingly engaged on the stem. The capillary bore acts to allow filling of the barrel but substantially prevents liquid from entering the bulb because it allows the operator time to remove his finger from the vent aperture of the bulb. The capillary bore is of sufficiently small diameter to provide stable retention of liquid contained in the barrel. The operating bulb may form part of the cap or stopper of a bottle, vial, or similar vessel. The capillary bore may be formed merely in a solid top extension of the pipet main barrel without requiring the formation of a reduced stem.

Description

This invention relates to liquid transfer devices, and more particularly to a pipet of the bulb-operated type.

A main object of the invention is to provide a novel and improved bulb-operated liquid transfer pipet which is very simple in construction, which is easy to operate, and which is volumetrically precise.

A further object of the invention is to provide an improved bulb-operated pipet which is versatile in use, which is easy to control, and which acts to automatically substantially terminate liquid intake action as soon as its barrel is completely filled with liquid, the intake action being terminated by the resistance to flow of a capillary column, the resistance to flow being sufficient to give the operator time to discontinue the application of filling pressure.

A still further object of the invention is to provide an improved bulb-operated liquid transfer pipet which is compossed of relatively inexpensive and easily manufacturable parts, which extracts highly accurate measured volumes from liquid containers, and which allows said measured volumes to be safely and reliably transferred without loss.

A still further object of the invention is to provide an improved liquid transfer pipet of the bulb-operated type which is constructed so that substantially all of its liquid retention chamber is visible to the operator and so that he can quickly terminate filling pressure when the chamber is filled.

A still further object of the invention is to provide an improved liquid pipet, which once filled can be placed in any position or handled fairly roughly without losing its contents.

A still further object of the invention is to provide an improved pipet closure for containers of diagnostic test reagents.

A still further object of the invention is to provide an improved bulb-operated liquid transfer pipet wherein the operating bulb is combined with a closure cap for a container and wherein the bulb and cap are adjustable so that they can be at times shifted to a position allowing the pipet to reach a bottom corner portion of the associated container, whereby by tilting the container practically all the liquid in the container may be ultimately removed, thus minimizing waste of the liquid.

A still further object of the invention is to provide an improved bulb-operated pipet which cuts off filling pressure when its main chamber is filled and reduces the possibility of drawing liquid into its operating bulb, the time period required for filling the main chamber being a definite value so that the operator can terminate the filling pressure at the end of such time period, making it unnecessary for him to closely watch the chamber during the filling operation, the pipet being thereby usable with high speed and precision while requiring a minimum amount of visual and mechanical effort and requiring a relatively low degree of dexterity on the part of the operator.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIG. 1 is a vertical cross-sectional view taken through a typical bulb-operated liquid transfer pipet constructed in accordance with the present invention.

FIG. 2 is a vertical cross-sectional view of a modified form of pipet in accordance with the present invention, shown combined with a screw cap closure on a liquid container.

FIG. 3 is a vertical cross-sectional view of the pipet of FIG. 2, shown with its operating bulb and screw cap in an extended position enabling the pipet to reach residual liquid in a bottom corner portion of the associated container, with the container tilted.

FIG. 4 is a vertical cross-sectional view of the pipet of FIG. 2, shown combined with the ground glass closure stopper of a reagent bottle.

FIG. 5 is a vertical cross-sectional view of the pipet of FIG. 2, shown combined with the rubber stopper of a laboratory vial.

FIG. 6 is a fragmentary vertical cross-sectional view showing a further modification of a bulb-operated liquid transfer pipet according to the present invention.

Referring to the drawings, and more particularly to FIG. 1, 11 generally designates a typical liquid transfer pipet according to the present invention. The pipet comprises a tubular main barrel 12 having a reduced bottom inlet conduit portion 13 integrally connected to the main barrel 12 by a tapered portion 14. Main barrel 12 is provided with a reduced top stem 15 of substantial length having a capillary bore 16 which may be from about 0.002 to 0.02 inch in inside diameter. Slidably and sealingly mounted on stem 16 is a filling bulb 17 of resilient deformable material, such as rubber or the like. Bulb 17 is provided with a top vent aperture 18 adapted to be at times sealingly covered by the user's finger, for example, after the bulb has been squeezed to a collapsed condition and it is desired to draw liquid into barrel 12, or when it is desired to expel liquid from the barrel after it has been filled.

The barrel 12 has a generally frusto-conical top wall 19, with the stem 15 integrally formed at its apex. When liquid drawn into the barrel 12 reaches top wall 19, it is thereafter forced into the capillary bore 16, which imposes a high resistance to flow and thereby substantially abruptly terminates intake of liquid into the barrel. With a given pipet, the filling time will therefore be substantially constant, and an operator can quickly learn to remove his finger from the aperture 18 at the end of the filling time period after a few experimental usages of the pipet. Alternatively, the operator can easily visually determine when the liquid reaches top wall 19. In either case, the intake flow is so retarded by the action of the capillary bore 16 that the operator has sufficient time to remove his finger from aperture 18 after barrel 12 is filled to prevent liquid from being forced completely through and beyond the capillary bore 16.

After filling, the surface tension of the liquid in the capillary bore 16 acts in a manner to cause this liquid to seal the bore and to thereby allow the pipet to be transported without loss of liquid from the filled barrel 12. The liquid can be thereafter discharged from the pipet by sealing vent aperture 18 with the user's finger and applying squeezing pressure to the bulb 17.

In the event that during filling the operator fails to release his finger from the vent aperture 18 in time to prevent liquid from overflowing from the top end of capillary bore 16 into the bulb 17, it will not re-enter the bore when the pipet is discharged in the above-described normal manner since it will tend to accumulate at the bottom of the bulb around the stem 15. The possibility of such overflow can be minimized by making stem 15 of substantial length, for example, from about 3/4 inch to as much as 2-1/2 inches. To further reduce the possibility of re-entry of overflow liquid from bulb 17 into the capillary bore when liquid is discharged from the pipet, the top end of the capillary stem portion may be made conical, as shown at 21 in FIGS. 2 to 5, or frusto-conical, as shown at 22 in FIG. 6.

As shown in FIG. 6, the capillary bore 16 may be formed merely in a solid top extension 20 of the pipet main barrel, wherein no reduction in diameter of the top portion of the main barrel body is necessary.

Although the capillary bore 16 is of substantial length, its inside diameter is so small that its entire volume, compared to the measured volume in the main barrel of the pipet, is not large enough to cause any significant error in the measured volume of liquid dispensed by the pipet.

Referring now to FIGS. 2 and 3, a pipet 23 generally similar to the previously described pipet 11 is shown combined with a screw cap closure 24 threadedly engageable on the neck 25 of a conventional bottle 26. In this embodiment the operating bulb, shown at 27, is integrally formed with a generally frusto-conical annular bottom sealing stopper 28 which is received beneath an inturned annular top lip or flange 29 of the generally ring-shaped rigid screw cap 24, so that when the cap 24 is tightened the stopper element is clamped sealingly on the top rim of the bottle neck 25. The top stem, shown at 15', is slidably and sealingly engaged through the thickened bottom portion 30 of the bulb 27 concentrically with stopper 28. With the screw cap 24 loosened sufficiently to allow atmospheric air to enter the bottle through the neck 25, the pipet assembly can be employed in the same manner as previously described to dispense accurately measured liquid volumes from the bottle 26. To remove practically all of the liquid from the bottle, so as to minimize waste, the cap 24 may be unscrewed from the neck of the bottle and the bulb 27 can be adjusted upwardly on the stem 15', as shown in FIG. 3, whereby the inlet conduit portion 13 can be manoeuvered to reach the lowermost corner portion of the bottle, in the tilted position of the bottle illustrated, whereby to draw the last remaining amounts of liquid into the pipet.

In the embodiment illustrated in FIG. 4, the pipet assembly of FIG. 2 is combined with a stopper plug 31 similar to the ground glass sealing plug of a reagent bottle 32. The stopper plug 31 is of hollow construction and has a top wall which is centrally apertured to receive a rubber, or similar resilient deformable grommet 33, and the stem portion 15' of the pipet assembly is slidably and loosely engaged through said grommet and the pipet assembly may be employed in the same manner as described above in connection with FIGS. 2 and 3 to dispense accurately measured volumes of liquid reagent from the bottle 32.

In the embodiment illustrated in FIG. 5, the pipet assembly of FIG. 2 is employed with a centrally apertured rubber or similar stopper plug 34 similar to the stopper plug of a conventional serum vial 35. The barrel 12 of the pipet assembly is loosely engaged through the central aperture of the plug 34, and the pipet assembly may be employed in the same manner as described above in connection with FIGS. 1, 2 and 4.

In each of the embodiments illustrated in the drawings and described above, the capillary bore at the top end of the pipet barrel serves to 1) inhibit further entry of liquid into the barrel when the measuring cavity therein has been completely filled, and thereby give the operator time to remove his finger from the vent aperture 18, and 2) provide a retention means, namely, the capillary column of liquid in the bore, to enable the filled pipet to be safely transported without risk of loss of its contents, since the capillary column provides a holding effect sufficient to support the liquid in the filled pipet barrel. In pipets of the type previously employed, either of the mouth-operated or bulb-operated type, the operator must place and hold his finger in sealing engagement with the top end of the pipet or other vent aperture of the pipet when the pipet is to be transported, calling for considerable dexterity on the part of the operator. This is not necessary with the above-described apparatus.

In operating any of the above-described forms of the present invention, the operating bulb is first squeezed to a collapsed condition, after which, with the intake end of the pipet immersed in the liquid to be dispensed, the operator covers aperture 18 with his finger and allows the bulb to resume its normal shape. This draws liquid into the pipet barrel, filling the pipet barrel cavity, the liquid rising therein until it enters the capillary bore 15, at which time the filling action is abruptly terminated by the resistance imposed by the capillary bore, as above described. The operator then removes his finger from aperture 18 and the pipet can then be transported to the intended receiving vessel or receptacle, into which the liquid in the pipet may be then discharged by again covering the aperture 18 and squeezing the operating bulb.

In the various different forms of the invention above-described the portion of the barrel carrying the operating bulb is preferably of cylindrical shape and of uniform cross-sectional diameter, whereby to facilitate adjustment of the bulb therealong as required.

While certain specific embodiments of liquid transfer pipets have been disclosed in the foregoing description it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

Claims

What is claimed is:

1. A liquid transfer pipet comprising a barrel member having a liquid-receiving cavity portion and an intake conduit element at one end of said barrell member communicating with said cavity portion, the opposite portion of said barrel member being formed with a capillary bore coextensive in length therewith in communication with said cavity portion and opening at the opposite end of the barrel member, and a flexible operating bulb sealingly engaged on and slidably receiving said opposite portion, said bulb being formed with an upper vent opening adapted to be sealingly engaged at times by an operator, and wherein said opposite portion of the barrel member is of substantial length and of uniform cross-sectional size and shape and is much smaller than the bulb, whereby the bulb may be adjusted to a position along said opposite portion wherein said opposite portion projects upwardly a substantial distance through an opening in the bulb to define within said bulb above said opposite portion an air space and within said bulb below said opposite portion an overflow space of substantial volume in the bottom of the bulb around said opposite portion, and said upper vent opening being in communication with said air space, and whereby liquid accumulating in said overflow space will not re-enter said capillary bore when the bulb is squeezed to discharge liquid from the pipet.

2. The liquid transfer pipet of claim 1, and wherein said capillary bore has an inside diameter of between 0.002 and 0.02 inch.

3. The liquid transfer pipet of claim 1, and wherein the end of said opposite portion received in the operating bulb is tapered, whereby to minimize the possibility of re-entry of overflow liquid from the bulb into the capillary bore when liquid is discharged from the pipet.

4. The liquid transfer pipet of claim 1, and wherein said opposite portion is in the form of a reduced stem of substantially uniform cross-sectional size, whereby the operating bulb may be at times adjusted in position along said reduced stem.

5. The liquid transfer pipet of claim 1, and wherein the capillary bore is sufficiently small in inside diameter and of sufficient length to develop the capillary sealing action required to support the total volume of liquid receivable in said cavity.

6. The liquid transfer pipet of claim 1, and wherein said opposite portion is in the form of a reduced stem of circular crosssectional shape.