US2398234A - Adjustable automatic pipette - Google Patents

Description

April 9, 1946. w D. LONG ADJUSTABLE AUTOMATIC P IPETTE Filed Dec.

FIG.

FIG. 2.

. INVENTOR' WENDAL D.

LO NG ATTQRNEY Patented Apr. 9, 1946 ADJUSTABLE AUTOMATIC PIPETTE Wendal D. Long, Los Angeles, Calif., assignor to Horton & Converse, Los Angeles, Oalifi, a corportion of California Application December 11, 1942, Serial No. 468,738

3 Claims.

My invention relates to improvements in automatic pipettes of the overflow type; and the object of my improvement is to provide a method for adjusting the volume delivered by the pipette.

I attain this object by mechanism illustrated in the accompanying drawing, in which Figure 1 is vertical section of a double action pipette; Figure 2 a vertical section of a single action pipette; Figure 3 a vertical section of the barrel of the volume chamber; and Figure 4 a vertical section of the movable plunger and overflow bulb.

Similar numerals refer to similar parts throughout the several views.

Delivery of a desired volume of liquid is accomplished by regulating the volume of chamber I by adjusting the position of plunger 2 in barrel 3. The plunger is held in place by a suitable clamp.

In operation, with stopcock 6 in fill position, liquid from reservoir 4 flows through tube 5 and stopcock 6, fills chamber 1, then rises in tube 1, overflows into bulb 8, then flows through tube 9 and rises in flexible tube Hi to the level of liquid in reservoir 4. When stopcock 6 is in empty position, liquid flows downward from overflow tip ll, tube l and chamber I through stopcock 6, and out delivery tube I2. The liquid in tube 9 and flexible tube It) flows into overflow bulb 8 and on the next cycle is forced into reservoir 4 at point l3.

An opening it into reservoir 4 is provided to equalize the pressure within the apparatus when liquid is delivered.

In operation of double action adjustable automatic pipette Fig. 1, one chamber is filled while the other is emptied by use of a double Y stopcock.

The apparatus is preferably but not necessarily constructed of glass with the exception of flexible tube H] which is rubber or other suitable material. The invention is designed to deliver a multiplicity of volumes of liquid with great accuracy, one of its principal uses being for analytical procedures. This accuracy is attained by reason of the fact that the liquid delivered is only that portion contained in vent pipe I, chamber I, stopcock 6 and outlet tube [2. The bulb 8 serves the essential function of trapping the overflow liquid (from filling operation) contained in tubes 9 and H). The tube in is necessarily connected to reservoir 4, as it serves the necessary function of allowing the liquid trapped in the overflow bulb 8 to be forced out through tubes 9 and I0 into the reservoir 4, which enables the air in the empty system to be replaced by liquid during the filling cycle. In operation, liquid from the reservoir 4 flows downward through tube 5 into stopcock 6 filling one adjustable chamber I and then flowing upwardly through hollow rod 1 overflowing into overflow bulb 8. The overflow liquid then rises in return flow tube ID to the liquid level in the reservoir. On turning the stopcock 6 one-half turn, the liquid flows downward from overflow point I l emptying the adjustable chamber at the delivery tube l2, the volume delivered being regulated by raising or lowering the plunger 2. The liquid in the return flow tube is trapped in overflow bulb B and is forced back into the reservoir on the next cycle. One pipette fills as the other one delivers, thus one volume is delivered with each one-half turn of the stopcock. The air vent I 4 serves several purposes. It equalizes the air pressure in the reservoir when the unit is being used without connection to a bulb bulk supply source, may be connected to a bulk supply source arranged to flow into the reservoir 4 by gravity. and air pressure may be applied through this vent where greater filling speed is desired or heavy liquids are being handled. When one side of the device has discharged, the liquid previously in tube II! is trapped in bulb 8. The amount discharged cannot possibly vary from the volume of the chamber, outlet system and vent pipe 1.

I am aware that prior to my invention automatic pipettes of the overflow type have been made. However, to my knowledge none have been made with the adjustable feature herein described.

I therefore claim:

1. A structure of the class described comprising a reservoir, a chamber below the same, a conduit depending from the reservoir and communicating with the lower portion of said chamber, a piston in said chamber, said piston being adjustable in the chamber to vary the capacity of the latter, a bulb on said piston disposed above said chamber, a hollow rod extending from the piston so that material may pass from the chamber into the bulb, said hollow rod being disposed within said bulb so as to form a trap, and a tube extending upwardly from said bulb and communicating with said reservoir above said conduit.

2. A structure of the class described comprising a reservoir, a conduit depending therefrom, a chamber below the reservoir in communication at its lower end with said conduit, a piston adjustable in said chamber to vary the capacity of the latter, a bulb on said piston above said chamber, a hollow rod extending from the piston to permit passage of material from the chamber through the piston into said bulb, said hollow rod being disposed within said bulb so as to form a trap, and a tube extending from said bulb and communicating with said reservoir above the conduit.

3. A structure of the class described comprising a reservoir, a conduit depending from the reservoir, a pair of chambers in communication at their bases with said tube, a piston adjustable in each of said chambers to vary the capacity thereof, a bulb on each of said pistons above said chambers, each of said pistons being hollow and having a tubular portion extending into its corresponding bulb so as to form a trap therein and to establish overflow communication between each of said chambers and its corresponding bulb, tubes establishing communication between each of said bulbs and said reservoir above the conduit. and a Y stopcock means between the conduit and said chambers adapted to enable one chamher to be filled while the other chamber is emptied.

WENDAL D. LONG.

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