Micropipette With Disposable Tips

Abstract

A spring loaded plunger actuated vacuum pipette tube is disclosed for use in combination with removable disposable molded plastic tip members wherein a plurality of adjacent concentric internal annular rings are formed within the larger open end of the tip member, and annular rings being of successively decreasing diameter progressing inwardly, for cooperative airtight frictional engagement with a smoothly tapered end surface of the pipette tube. The foregoing abstract is not to be taken either as a complete exposition or as a limitation of the present invention. In order to understand the full nature and extent of the technical disclosure of this application, reference must be had to the following detailed description and the accompanying drawing as well as to the claims.

Description

BACKGROUND OF THE INVENTION

In busy chemical and pharmaceutical laboratories, for the expeditious performance of numerous analytical tests it is necessary to quickly and accurately measure and deliver micro volumes of various reagents and samples for analysis. For this purpose various vacuum pipettes have been developed in the prior art.

The present invention is directed to improved disposable pipette tips, formed of injection molded plastic material, such as polyethylene, which are functional for a wide range of applications and are impervious to acids, alkalies and most organic solvents, and have non-wetting characteristics. The tips are easily and quickly inserted on the end of a pipette tube with which they form an airtight seal, and are just as easily and quickly removable therefrom for disposal after use. Because of their low cost the plastic tips of the invention may be discarded after each use, thus eliminating the need for washing and sterilization for the next operation. By reason of an external annular shoulder formed around the larger open end of each tip a quantity of tips may be stored in a sanitary jig or fixture from which individual tips may be easily picked up by simply inserting the end of a pipette tube, and they may be subsequently removed from the instrument simply by pressing the external shoulder against the lip of a disposal container -- all in a single handed operation.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an inexpensive disposable micropipette capable of easy and convenient one-hand operation without need for or risk of the operator's hand touching any part which comes in contact with chemical reagents.

It is a further object to provide such a pipette which is impervious to acids, alkalies and organic solvents.

An overall object of the invention is to provide such a micropipette which affords maximum convenience, cleanliness, ease of operation and the elimination of cross-contamination.

Other objects of the invention will in part be obvious from the following description and the claims.

The invention accordingly comprises an article of manufacture possessing the features, properties, and the relation of elements which will be exemplified in the article hereinafter described, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWING

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which:

FIG. 1 is a horizontal view, partially cut away, of a pipette instrument with a disposable tip member mounted on the vacuum end thereof;

FIG. 2 is an enlarged view of the tip member mounted on the instrument end, and shown partially in section substantially along the line 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view of the large end of the tip member taken along the line 3--3 of FIG. 2; and

FIG. 4 is a greatly enlarged cross-sectional view of the large end portion of the tip member of the invention showing the manner in which the concentric internal annular ringed rib portions decrease in diameter inwardly to provide effective airtight sealing means for the pipette tube.

DETAILED DESCRIPTION

Referring now in greater detail to FIG. 1 of the drawing, a preferred embodiment of the invention includes a vacuum pipette instrument indicated generally at 5, having (from right to left) a finger operated plunger 6 axially mounted within an annular finger grip 7 which is affixed to one end of a hollow cylindrical tube 8. Affixed to and coaxial with the opposite end of cylinder 8 is a reduced diameter elongated hollow nozzle portion 9, the end of which is tapered as may be seen more clearly in FIG. 2.

Still referring to FIG. 1, within the hollow cylindrical tube 8 is a spring loaded air pump piston 10 which is operable by depression and release of plunger 6 to produce a controlled stroke, measured volume air displacement. An airtight axial valve formed between the internal central rod 11 and a valve seat formed in coaxial bushing 12 is opened when the plunger 6 is depressed and is closed when plunger 6 is fully released. As shown to the left in FIG. 1 an elongated hollow tapered tip member 14, which is preferably formed as a right circular cone, has its larger open end fitted over the tapered end of nozzle 9 on the plunger instrument 5. The opposite end 16 of tip member 14 is provided with a small diameter coaxial opening through which controlled amounts of fluid may be admitted and discharged when the tip end 16 is immersed in sample liquids or reagents and the plunger 6 is depressed. In use the device of FIG. 1, including the pump instrument 5 with tip member 14 affixed as shown, is held in a generally vertical position by one hand, with two fingers under the annular grip 7 and a thumb or forefinger resting on plunger 6 in a position for depressing the plunger at will. The plunger 6 is then depressed, the tip 16 is immersed in the liquid to be sampled, and the plunger 6 is then released, thereby drawing an accurately measured volume of liquid into the lower end of tip member 14. Because of the closure of the airtight valve 11-12 upon release of plunger 6 the liquid drawn into a tip member 14 remains therein, under the force of external atmospheric pressure, until such time as the plunger 6 is again depressed to expel the sample fluid from the small end opening at 16. Because the total internal volume of the conical tip member 14 greatly exceeds the accurately measured volumetric displacement of plunger 10 within cylinder 8, the sample fluid within the tip 14 never rises far enough to contaminate (or be contaminated by) the nozzle 9 of instrument 5. After discharge of the measured sample from tip 14, the tip member may be easily removed from the nozzle 9 by a simple "wiping" motion, as achieved by placing the annular shoulder portion 17 against the inner lip of an open refuse container and merely pulling backward (from left to right in FIG. 1) on the annular finger grip 7. A fresh unused tip may then be easily picked up simply by inserting the tapered end of nozzle 9 into the open end of a new tip member, which may be conveniently held either by hand or in a table top fixture rack.

The salient feature which facilitates the airtight engagement of the tip members such as 14 with the instrument nozzle 9, and the ease of application and removal therefrom as described above, will now be described in detail with reference to FIGS. 2 through 4 of the drawing.

Referring first to FIG. 2, which is an enlarged view of the left-hand portion of FIG. 1 with the tip member 14 foreshortened at 13 to conserve drawing space and the right half of member 14 cut away in section to show the internal cavity 20, the tapered end surface 18 of nozzle 9 may be seen inserted into frictional engagement with a plurality of inner annular ring ribbed portions 19 formed on the inner open end 15 of tip member 14. As the tip member 15 is formed of injection molded plastic material, such as polyethylene, the annular ribs 19 are semiflexible and compressible and thus provide a mechanically rigid airtight seal with the tapered metallic surface 18 of nozzle 9.

FIG. 3, being a cross-sectional view taken along the line 3--3 of FIG. 2, further illustrates the cooperative engagement of collar end 15 of tip member 14 surrounding the tapered surface 18 of hollow nozzle 9.

Referring now to FIG. 4, which is a greatly enlarged cross-sectional view of the right-hand end portion of tip member 14 as shown in FIG. 2, the plurality of inner annular ringed ribs indicated generally as 19 in FIG. 2 are shown separately as 21 through 25. From this figure it may be seen that the annular ribs 21-25 decrease in diameter inwardly from 25 to 21; i.e., the inner diameter of 25 is greater than that of 24, which in turn is greater than 23, etc. Significantly, a line drawn tangent to the inner annular surfaces of ribbed rings 21-25 forms a greater angle with the horizontal (in FIG. 4) than does the taper 18 of nozzle 9 in FIG. 2. Thus, when the tapered end of nozzle 9 is inserted into the larger open end of tip member 14, the surface 18 first engages outer annular rib 25; as the nozzle 9 is protruded further into tip 14 the surface 18 successively becomes frictionally engaged with annular ribs 24, 23, etc., compressing each rib further as it is inserted farther, thereby establishing both a mechanical coupling and an airtight seal between tip member 14 and instrument 5.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above article without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention which, as a matter of language, might be said to fall therebetween.

Claims

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The combination of a spring loaded plunger actuated vacuum pipette and a removable disposable plastic tip member comprising a taper formed on the end of the pipette opposite the plunger thereof, and a plurality of adjacent concentric internal ringed ribs of successively decreasing diameter formed on the inner surface of an open end of said plastic tip member, whereby said ringed ribs frictionally engage said tapered end to form an airproof seal therebetween.

2. The combination of claim 1 wherein the taper formed on the end of said pipette is less than the taper formed between the inner surfaces of the innermost and outermost of said successive internal ringed ribs.

3. The combination of claim 1 and an outer annular shoulder portion formed on the outer open end of said tip member adjacent to and surrounding said concentric ringed ribs.

4. For use with a spring loaded plunger actuated vacuum pipette instrument, a detachable and disposable tip member formed of molded plastic in a substantial right cylinder elongated hollow cone, having an outer annular ring portion formed around its larger open end and at least one elastically deformable annular inner ringed rib formed within said larger open end and concentric with the axis of said cone.

5. The combination of claim 4 including a plurality of adjacent annular ringed ribs formed on the inner conical surface of said tip member within the larger open end thereof, said annular ringed ribs being of progressively decreasing diameter inwardly from said open end.

6. The combination of claim 5 wherein the diameters of said adjacent annular ringed ribs decreases progressively in such manner that a conical surface tangential to the inner surfaces of all said annular ribs forms a greater taper than that of a pipette instrument adapted for insertion therein.