US3138299A - Squeeze bottle pipette - Google Patents

Description

June 23, 1964 J. J. J. STAUNTON 3,138,299

SQUEEZE BOTTLE PIPETTE Filed Jan. 9. 1961 20 INVENTOR.

flu. "1M r M 1 1 ATTORNEYS.

United States Patent 3,138,299 QUEEZE BOTTLE PIPETTE John J. .I. Staunton, Oak Park, Ill., assignor, by mesue assignments, to Coleman Instruments Corporation, Maywood, Ili., a corporation of Delaware Filed Jan. 9, 1961, Ser. No. 81,495 9 Qlaims. (Cl. 222-207) This invention relates to an improved construction for a pipette of the type used in microchemical analysis.

Basically a pipette tube is drawn to a small tip at the delivery end and open at the other end. The volume of the bore of this tube is known and indicated either by an index mark on the tube or, in the case of micro pipettes (less than 1 milliliter), the whole length of the pipette is used for the measured quantity of liquid. The pipette tube may be filled by direct suction with the mouth followed by placing the finger over the open end to prevent discharge of the liquid content until released. Where corrosive or poisonous liquids are to be handled a pipette filler, such as a rubber bulb, may be attached to the pipette tube to dispense with oral suction. The present invention relates to a pipette of this kind and includes a squeeze bottle having a dome enclosing its mouth and a pipette tube extending through the wall of the dome.

Very small wettable pipettes having a volume of a few microliters may be filled by capillary action because of their small bore. Small pipettes may be designed to be completely filled from end to end of their capillary bore; they are then said to be self-adjusting as any excess liquid will fall off or can be readily removed or, if capillary action fills them, the entering liquid will automatically stop at the end of the bore. The class of pipettes with which my invention is primarily concerned covers capacities from to 250 microliters. It should be understood, however, that the invention is not limited to this range and may be expanded at either end.

Pipettes of this size are being currently used in ultramicro analytical methods for clinical analysis using small samples. It has been proposed heretofore to make a dispensing pipette of this type by incorporating a polyethylene pipette tube in the wall of a vented glass dome covering the mouth of a squeeze bottle. When this construction is used as a reagent dispenser the bottle has a dip tube extending nearly to the bottom of the bottle and communicating with the dome from which the liquid is transferred to the pipette tube. To operate, the bottle is squeezed to force the reagent into the dome above the open end of the pipette tube therein. The vent in the dome is then closed with a finger and further squeezing forces reagent into the pipette tube. It is filled when a drop emerges from its constricted end. The vent is opened by removing the finger and the bottle is released in that order and the drop excess wiped from the tip. To deliver the contents of the pipette tube the vent in the dome is again closed with a finger and the bottle squeezed to force out the contents. This device may also be used as a sample pipette which is designed to draw a liquid sample from an external container. For such use the dip tube in the bottle may be dispensed with. To fill the pipette the bottle is squeezed, the pipette tube is dipped into the sample, and the bottle released until the pipette fills and an excess drops off the back or open end of the pipette tube. Delivery is the same as for the reagent pipette.

The prior pipette construction has a number of defects which make it diificult for the nonexpert to operate with ease and accurate results. The polyethylene pipettes are easily deformed so that they do not remain accurate in volume. The glass dome is expensive, hard to clean, and the vent hole is difficult to cover tightly. The neck of the bottle often does not seal properly against the dome. The longer pipette must be held almost level to prevent the solution from running out. A reagent pipette of this type is dangerous to use with poisonous or corrosive reagent liquids because any initial squeeze of the bottle, unless very slow, sends a jet of reagent up into the top of the dome from whence it squirts forcibly out the vent hole. Even where the reagent is not corrosive or poisonous this action is always annoying when it occurs. The operation of the sample pipette is also difficult because it is hard to stop releasing the bottle just when the liquid reaches the back end of the pipette and then take the finger oil the vent while holding the bottle fixed in size, not to mention removing the tip from the sample before any of the pipette contents run back.

The object of the present invention is to obviate the defects in the prior pipette constructions as set forth above. In a preferred form of the invention the pipette tube is made from glass which is always capable of accurate measurement. The end of the pipette within the dome is designed to cooperate with the resilient wall of the plastic dome in such a manner that automatic valve action is provided to hold or discharge the liquid from the pipette tube. Another object is to provide a glass pipette tube having a plastic cap containing a restricted orifice covering the open end thereof, thereby taking advantage of the accuracy of glass and the formability of plastic to provide the restriction in the end of the tube. Another object is to provide a pipette having a squeeze bottle and a communicating vented dome with a baflle in the communicating conduit to prevent accidental discharge of reagent from the bottle through the vent. Another object is to provide an improved ventconstruction which may be easily closed, using light digital pressure. These and other objects and advantages of the invention will be apparent from the following description when read in conjunction with the accompanying drawings, in which- FIGURE 1 is a sectional view through a pipette constructed in accordance with the present invention;

FIGURE 2 is a sectional view taken along the line Z2 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary view in section showing the restricted end of the pipette adjacent the cooperating inner wall of the plastic dome; and

FIGURE 4 is a sectional view through the dome and pipette tube showing an alternative form of dome construction.

Referring now to the illustrated form of the invention as shown in the drawings, the bulb or bottle is indicated by the numeral 10 and is molded from polyethylene or some other suitable flexible transparent plastic material. Polyethylene has proved to be highly satisfactory for this purpose although other plastics such as Teflon may be used if the wall is thin so that it may be readily compressed. It will also be appreciated that the material from which the bottle is made must be resistant to the reagent which will be placed therein. The bottle 10 terminates at its upper end in a relatively wide mouth 12 which is externally threaded as indicated at 14. A plastic dome 16 encloses the open mouth of the bottle. It has an outwardly extending peripheral flange 18 which rests on or just above the top edge of the mouth of the bottle. An internally threaded ring 20 having an inwardly extending upper flange or, shoulder 22 bears against the flange 18 to form a leak-tight seal at the connection. The dome 16 is preferably molded from a transparent plastic material similar to the bottle 10. A vent opening 24 is provided in the top wall of the dome 16. A peripheral rim 26 surrounds the opening so that the opening may be closed very simply by applying light digital pressure against the 1 peripheral rim 26.

The pipette tube is indicated by the numeral 50 and terminates at its discharge end in a tapered downwardly turning portion identified by the numeral 52. The tube is disposed within a sleeve or stopper 57 which in turn fits within an opening 55 in the side wall of the dome 16. The sleeve 57 may carry a circumferential projection 56 to facilitate handling the tube. It will be noted that the open end 54 of the tube 50 is of the same diameter as the rest of the tube except, of course, for the restricted tip 52. For purposes of the present invention as explained hereinbelow it is desirable to have a capillary orifice in the end 54 of the tube 50. This may be provided by shaping the glass at this end with the desired small diameter bore but this is a very difiicult fabricating job and would greatly increase the cost of the pipette tube. We have solved this problem by providing a plastic molded cap 58 which fits snugly over the open end 54 of the tube. The plastic cap terminates at its outer end in a tapered terminal portion 62 containing a capillary constricted orifice or bore 69. According to a preferred method for opcrating a pipette of the invention, this plastic cap is disposed within the dome so that its end is adjacent the flat wall 17 thereof.

As best shown in FIGURE 2, the plastic dome 16 is preferably molded with thickened side wall portions located normal to the axis of the pipette tube 50. The sleeve 57 fits into the opening 55 which is formed in one of these walls and the pipette tube cap 58 abuts the other of said walls. These thickened walls are joined by relatively thin side walls which readily fiex for providing the automatic valve action which is described below.

Where the bottle 10 is to be used to dispense reagent it is desirable to provide a dip tube 37 which extends from the neck or mouth almost to the bottom of the bottle. In accordance with the present invention the dip tube 37 is supported on a plug having a circumferential flange 39 which may be disposed between the upper edge of the mouth of the bottle and the lower side of the flange 18 of the dome 16. The plug has a downwardly extending skirt 32 which is sufficiently flexible to permit pushing the plug readily into the mouth of the bottle. A boss 34 projects downwardly from the center of the plug and contains a bore 36 which receives the tube 37 in frictional engagement. The upper end of the bore 36 terminates in a well 38 of considerably larger diameter than the bore 36. The well 38 is adapted to receive a bathe member 40 comprising half a cylinder having outwardly extending flanges 42 on either side thereof. The ends of the flanges 42 are curved to fit the circular wall of the well 38. The sides of the baffle member 40 are cut straight so that there is a space 43 provided between the sides of the bafile and the circular wall of the well through which liquid will pass in its journey from the bottle to the dome. It will be appreciated that this construction prevents forcing liquid from the bottle out through the vent 2a in the top of the dome. All liquid which passes through the tube 37 is directed against the underside of the bafiie and is thus diverted laterally to emerge through the open spaces 43 on either side of the baffle member. The plug member 31') may be molded from polyethylene resin just like the dome and the bottle. Because the plug need not be transparent a wider range of thermoplastic resilient resins may be used than in the case of the dome and the bottle. The plastic must be resilient, however, so that it fits well within the mouth of the bottle and seals well as the flange 39 is compressed with the dome flange 18 beneath the shoulder 22 of the screw cap 20.

The inner end of the sleeve 57 is tapered and is of slightly smaller diameter than the well 38 in the plug 30. This construction permits the pipette to be secured directly to the cap after the dome 16 has been removed. In this way a detergent solution within the bottle it) can be forced through the pipette to clean it. Furthermore, the plug 30 may be inverted and with a plastic delivery tip in place of the glass dip tube 37 it can be used as a wash bottle for cleansing other components of the analytical apparatus. It will also be appreciated that the ready separation of the dome, the plug and the ring facilitates cleaning of these elements. Preferably the plastic is molded so that the surface is very smooth which substantially eliminates adhesion of liquid to the surface of the plastic. Furthermore, the provision of a polished surface provides best transparency.

One of the important advantages in the operation of the present construction lies in the novel pipette valve resulting from the cooperation of the end of the cap 58 with the side wall 17 of the dome. In the use of micro pipettes, especially for sampling, it is often desirable to be able to incline the pipette, tip down, to facilitate withdrawal from or delivery into a bottle or test tube. Small pipettes, either of our design or prior art design, are able to be inclined considerably, the maximum angle with the horizontal below which draining or run-out will not occur being determined by the amount of capillarity or surface tension at the ends and by the length of the pipette. The length of the pipette, of course, develops the hydrostatic head tending to overcome surface tension and cause draining. With larger pipettes construction of the ends to increase the surface tension is necessary, but even this will not permit pipettes of over 100 microliters to be inclined very far without the contents being lost. It will be noted that the glass pipette tubes of the invention have a turned down tip which greatly increases ease of use over the straight prior art pipette tubes. The use of such a tip requires volumetric adjustment to be made at the back end of the pipette-a length adjustment. This adjustment becomes dilficult if the back end also must be constricted to prevent run-out at the tip end. It will be appreciated that surface tension is only effective against run-out at the end opposite the constricted end. Hence, any efilux at the same end promptly reduces the surface tension by increasing the size of the liquid surface. In accordance with our invention this effect has been turned to an advantage in the automatic valve. The polyethylene cap 58 having the restricted orifice 60 accomplishes the function of providing a restricted end to the pipette tube without complicating the process of volumetric adjustment effected by grinding the end. Because of the square inside shoulder of the cap and the small diameter bore 59, attaching the cap 58 does not significantly alter the pipette volume if the pipette is bottomed in the recess of the cap. The cap is made transparent to permit this bottoming to be checked and to permit viewing any bubbles that may be present. It will be appreciated, therefore, that even without the cooperation of the wall of the dome this construction offers many improvements in manufacturing and can be tilted farther from horizontal without run-out because the end is constricted.

When the end 61 of the cap 58 is pushed into gentle contact with the flat wall 17 of the dome a valve is provided which can either operate automatically or by manual pressure applied to the dome vent 24. The details of this construction are best shown in the enlargement of FZGURE 3. In this view the clearance between the tip 61 and the wall has been exaggerated. The clearance is produced by first filling the horizontal pipette tube, then pressing in on the pipette sleeve 57 to seal the tip 61 against the wall; and finally, with the pipette tip 52 elevated to loosen the seal just enough to permit slow run-back into the dome. The pipette is now ready to use. As a reagent pipette the filling procedure is as previously described. Speed of filling because of the constriction is somewhat reduced, making control easier. The tapered end 62 prevents a drop of liquid from being caught between the end 61 of the cap 58 and the wall 17. A'residual drop, outlined as a-a in FIGURE 3, will drain away after the receding fluid in the dome or if the tip 52 of the pipette tube is held down, will recede into the pipette. This is aided by the condition that the surface of the residual drop. decreases and the surface tension increases as the drop shrinks from a to b to c. At some point between b and c equilibrium is reached and no further fluid appears at the pipette tip 62. With the wiping off of the drop at the tip the pipette is ready for delivery. It can be held vertically, tip down, with no run-out due to the effective automatic action of the valve. Discharge is effected in the usual manner and will be rapid because the constriction 60 offers little resistance to air flow once the surface tension lock is released.

In using the valve with a sample pipette a further desirable feature results. On filling the pipette in the normal manner the liquid inrush is rapid because the air leaves the backaof the pipette freely. In the construction of the invention the incoming liquid, on reaching the constricted bore 60, slows down so abruptly that the change in speed can be both felt and heard by the user. If he then takes his finger otf the vent 24 the pipette will adjust itself when held tip down and will not run out. This obviates the difliculty of releasing the bottle precisely when the liquid reaches the back end of the tube. Thus filling is greatly simplified, in accordance with the invention.

Should a higher filling or delivery speed, or more positive valve action than produced by the automatic valve, be desired the same valve may be used with manual action. An increased pressure on the vent 24 will depress the top of the dome to distend the thinner wall portions and force the thicker front and back wall portions apart, thus moving the pipette end 61 away from the backward moving back wall 17. This opens the valve. It will be noted that this opening occurs when the valve is closed and is arrested when the vent is open, thus requiring no change in technique from the normal procedure described above in using the device either as a reagent or as a sample pipette. For most positive valve operation I have found that the cap 58 should be as rigid as practical to avoid resilient springing of the sealing end of the cap which would reduce the effective valve travel.

In FIGURE 4 we have shown an alternative form of construction for the dome which facilitates operation of the valve so that it may go from positively closed to nonrestrictively open by applying a pressure of just a few ounces on the rim 26 surrounding the vent 24. The construction is the same as that shown in FIGURE 1 except that it includes additionally a pair of diagonal ribs 75 which extend from the vent opening 24 downwardly to a point somewhat above the pipette tube 50. These ribs are triangular in shape and are integrally molded with the dome so that they join the thicker portions 17 at the front and back of the dome. By applying pressure on the rim 26 to the construction shown in FIGURE 5 the front and back walls 17 of the dome will travel twice the distance of the structure of FIGURE 1 which does not have the ribs 75. While this construction makes adjustment of the valve sealing pressure or spacing less critical one caution must be taken if the full manual system is used on a sampling pipette. Automatic adjustment will not occur, and any residual drop at the tip of the cap 58 must be removed by flicking the side of the dome with the finger. It will be apparent that any degree of adjustment from full manual to automatic can be had without change of technique other than mentioned above.

It will be appreciated that various modifications may be made in the construction and in the materials of the pipette illustrated and described herein. It is our intention to include within the scope of the appended claims any such modifications which they might reasonably embrace.

What is claimed is:

1. In a pipette comprising a squeeze bottle having an open mouth, a resilient dome covering the mouth of the bottle having a vent through the top thereof, and a pipette tube extending laterally through the Wall of said dome,

the improvement comprising a plug member disposed within said month, an opening extending through said plug member to permit communication between the interior of said bottle and said dome, said opening terminating in a well of larger diameter than said opening, and a baifie member disposed within said well for deflecting fluid flow from said opening laterally into said well, thereby preventing fluid from being forced out through the vent.

'2. The pipette of claim 1 in which said bafiie consists of a semi-tubular member of lesser length than the diameter of said well. 7

3. A pipette comprising a squeeze bottle having an open mouth, a resilient plastic dome covering said mouth and having a vent in the top thereof, said dome having opposed side Wall portions of greater thickness than the wall portions intermediate said opposed side wall portions, at least one of said opposed wall portions having a flat surface, a pipette tube extending laterally through one of said opposed wall portions and terminating adjacent said fiat surface, the terminus of said tube containing a capillary bore of smaller diameter than the inside diameter of said tube whereby the distance between said terminus and said fiat surface may be increased by applying an external force to said dome.

4. The pipette of claim 3 in which said terminus of the pipette tube consists of a plastic cap and said tube is made from glass.

5. A pipette comprising a squeeze bottle having an open mouth, a resilient transparent plastic dome covering said mouth and having a vent in the top thereof, a pipette tube extending laterally through the wall of said dome and terminating at its inner end in a capillary bore of smaller diameter than the inside diameter of said tube, said inner end being adjacent a portion of the side wall of said dome, said portion being fiat for cooperating with said inner end to provide valve means to regulate fluid flow into said pipette tube through said bore, said valve means being operated by applying force to said dome to increase the distance between said inner end and said flat portion.

6. The pipette of claim 5 wherein said pipette tube is made of glass and terminates at its outer end in a down turned restricted portion.

7. The pipette of claim 6 in which said inner end of the pipette tube consists of a plastic cap containing said capillary orifice.

8. The pipette of claim 5 in which said dome has integrally molded internal ribs extending from the top to the side walls and lying generally in a plane extending through the axis of said pipette tube, said ribs serving to transmit force on the top of said dome directly to the wall portions of the dome in alignment with said tube for actuating said valve means.

9. A pipette comprising a polyethylene squeeze bottle having an open mouth, a vented polyethylene dome enclosing said mouth, and a glass pipette measuring tube piercing the wall of said dome, said tube terminating at its outer end in a tapered constricted orifice and at its inner end in a plastic cap having a capillary orifice therein communicating with the interior of said pipette tube, said cap having its outer end in contact with the inside wall of said dome to provide automatic valve means for controlling liquid flow in and out of said pipette tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,845 Stephens Jan. 9, 1934 2,024,723 Dykema Dec. 17, 1935 2,311,367 Chambers Feb. 16, 1943 2,533,726 Floyd Dec. 12, 1950 2,715,980 Frick Aug. 23, 1955 2,765,004 Williams Oct. 2, 1956 2,974,528 Sanz Mar. 14, 1961 FOREIGN PATENTS 863,537 Great Britain Mar. 22, 1961

Claims (1)

1. IN A PIPETTE COMPRISING A SQUEEZE BOTTLE HAVING AN OPEN MOUTH, A RESILIENT DOME COVERING THE MOUTH OF THE BOTTLE HAVING A VENT THROUGH THE TOP THEREOF, AND A PIPETTE TUBE EXTENDING LATERALLY THROUGH THE WALL OF SAID DOME THE IMPROVEMENT COMPRISING A PLUG MEMBER DISPOSED WITHIN SAID MOUTH, AN OPENING EXTENDING THROUGH SAID PLUG MEMBER TO PERMIT COMMUNICATION BETWEEN THE INTERIOR OF SAID BOTTLE AND SAID DOME, SAID OPENING TERMINATING IN A WELL OF LARGER DIAMETER THAN SAID OPENING, AND A BAFFLE MEMBER DISPOSED WITHIN SAID WELL FOR DEFLECTING FLUID FLOW FROM SAID OPENING LATERALLY INTO SAID WELL, THEREBY PREVENTING FLUID FROM BEING FORCED OUT THROUGH THE VENT.

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