US3923205A

US3923205A - Liquid dispensing device

Info

Publication number: US3923205A
Application number: US452063A
Authority: US
Inventors: Erik Lars Ohlin
Original assignee: Swelab Instrument AB
Current assignee: Swelab Instrument AB
Priority date: 1973-03-29
Filing date: 1974-03-18
Publication date: 1975-12-02
Anticipated expiration: 1992-12-02
Also published as: IT1011649B; FR2223673B3; GB1457055A; FR2223673A1; SE371370B

Abstract

A device for repetitively dispensing a measured volume of liquid includes a self-contained dispenser which can be used either separately as a manual pipette or in combination with a power actuator when automatic repetitive dispensing is desired. The power actuator is constructed to provide unobstructed access to it for the dispenser so that the dispenser can be placed in and removed from the actuator through a simple movement. In addition to the placing of the dispenser on a support in the actuator, or the taking away of the dispenser from the support, no manipulative operation is required to make the combination ready for operation as an automatic pipette respectively to separate the dispenser from the actuator.

Description

Unite States atet 1 1 l 11 3,923,205

Ohlin Dec. 2, 1975 1 41 LIQUID DISPENSING DEVICE [75] Inventor: Erik Lars Dhlin, Stocksund, Sweden f Em'n,7er RObert Reeves Assistant E.\'ammerFreder1ck R. Handren 1 1 Assigneel Swelab Instrument Sweden Attorney, Agent, or FirmHil1, Gross. Simpson. Van [22] Filed: Mar. 18 1974 Santen, Steadman, Chiara & Simpson [21] Appl. No.: 452,063 [57] ABSTRACT A device for repetitively dispensing a measured volume of liquid includes a self-contained dispenser which can be used either separately as a manual pipette or in combination with a power actuator when automatic repetitive dispensing is desired. The power actuator is constructed to provide unobstructed access to it for the dispenser so that the dispenser can be placed in and removed from the actuator through a simple movement. In addition to the placing of the dispenser on a support in the actuator, or the taking away of the dispenser from the support, no manipulative operation is required to make the combination ready for operation as an automatic pipette respectively to separate the dispenser from the actuator.

4 Claims, 1 Drawing Figure US. atnt Dec. 2, 1975 LIQUID DISPENSING DEVICE This invention relates to a device for automatic repetitive dispensing of liquids.

Devices of this kind, which are sometimes termed automatic pipettes, are used in automatic chemical analyzers, for example, where they may serve to dispense a predetermined volume, of a liquid reagent or diluent to each of a plurality of liquid samples.

Although some known automatic pipettes used in automatic chemical analyzers. can be used independently of the analyzers with minor or no modifications, they are too elaborate to be justified for use only in connection with the analysis or treatment of shorter series of samples. In many chemical laboratories, however, there is a great need forautomatic pipettes which can be used as separate units, but in order that the purchase of such automatic pipettes may be justified, they have to be substantially cheaper than the automatic pipettes which are constructed primarily with a view to their use in automatic analyzers. On the other hand, they must not be inferior in accuracy and they must not be suceptible to damage or malfunction.

In accordance with the invention there is provided an inexpensive device filling the just-explained need. As will become apparent from the following description, the construction of the dispensing device according to the invention is based on the concept that the part performing the actual dispensing, hereinafter termed the dispenser, and the part repetitively actuating the dispenser, hereinafter termed the actuator, should not be more or less integrated components of the complete automatic dispensing device but should be capable of use independently of each other. Thus, the dispenser should also be capable of use as a manual pipette, and one and the same actuator should be capable of use with different dispensers. When the dispenser is to be used for the automatic repetitive dispensing, it should be possible to place the dispenser in a dispensing position on or in the actuator by a mere shift and then the dispensing device should be ready for operation as an automatic pipette. In other words, no additional manipulative steps should be required to operatively connect the dispenser and the actuator.

A full understanding of the invention and its objects, features and advantages will be had from the following description of a preferred embodiment, reference being had to the accompanying drawing the single FIG- URE of which is a perspective view of a dispensing device constructed in accordance with the invention.

The illustrated dispensing device comprises two separate main parts, namely a self-contained dispenser 11 and a power actuator 12.

The dispenser includes a glass container 13 holding the liquid to be dispensed and having a cap 14, and a positive-displacement pump which is mounted on the cap and includes a single-acting vertical piston pump 15 having a discharge tube 16 and an operating member 17 projecting upwardly from the cap and fixedly connected with the pump piston 18. The operating member 17 is urged upwardly by a spring 19 and can be displaced up and down between an advanced, lower extreme position, which is fixed and defined by the engagement of the pump piston 18 with a fixed stop, namely the bottom of the pump cylinder 20, and a retracted, upper extreme position, which is defined by the engagement of a knob on the upper end of the operating member with a vertically adjustable stop 21. The detailed construction of the pump 15 forms no part of the present invention and hence it is believed sufficient to state that once the pump. is filled with liquid from the container 13, the depression of the operating member 17 from the upper to the lower extreme position will cause a liquid volume determined by the setting of the stop 21 to be dispensed through the discharge tube 16. When the operating member is then released, it is returned to the upper extreme position by the spring 19, thereby performing the final portion of a pumping cycle and aspirating an equal volume into the pump from the container.

The'actuator 12 has a base plate'22 and a head 23 supported above the base plate, which serves as a support for the dispenser, by means of a pair of vertical posts 24. The spacing of the posts 24 is sufficient to permit a ready positioning of the dispenser in a dispensing position on the base plate between the posts and a ready removal of the dispenser from that position. The base plate 22 may be provided with a recess, a rim, pilot projections or other elements facilitating the placing of the dispenser in the dispensing position.

The head 23 includes a vertically guided driver rod 25 which is reciprocable between a lower, extended extreme position and an upper, withdrawn position by a slot-and-pin drive mechanism 26 having a motor 27. The controls of the motor are arranged such that the motor either rotates continuously or rotates only one revolution at a time and such that it is always stopped when the driver rod is in or near its upper extreme position. The lower end of the driver rod 25 is provided with a pusher member 28 which is adapted to press on the upper end of the operating member 17 of the dispenser 11 and which is displaceable upwardly relative to the driver rod against the action of a compression spring 29. The downward bias imposed on the pusher member 28 by the spring 29 is at least slightly greater than the maximum upward bias imposed on the operating member 17 by the spring 19.

The fixed distance between the extreme positions of the driver rod 25 is at least slightly greater than the maximum distance between the extreme positions of the operating member 17, the arrangement being such that the lower end of the vertical path traversed by the lower end of the pusher member 28 during reciprocation of the driver rod 25 with the dispenser 11 removed from the base plate 22 is situated slightly below the lower extreme position of the upper end of the operating member 17. As a consequence, when the driver rod 25 is in its withdrawn or upper extreme position, the dispenser 11 can be placed in the dispensing position on the base plate 22 with the operating member 17 exactly below the driver rod and the pusher member, and then removed therefrom, there being nothing impeding this positioning and removal, which can be effected by a mere horizontal shift of the dispenser, even if the operating member 17 is in its upper extreme position. In addition, it is ensured that the pusher member 28 of the driver rod 25 depresses the operating member 17 to its lower extreme position. The excess displacement of the driver rod 25 adjacent the lower extreme position is accomodated by pressing the pusher member upwardly a small distance relative to the driver rod against the bias provided by the spring 29.

What is claimed is:

1. A device for repetitively dispensing a predetermined quantity of liquid, comprising:

a. a dispenser including a positive-displacement pump having an operating member, said operating member being displaceable between an advanced position defined by a stop and a retracted position operating member to displace it to said advanced position of said operating means and for accommodating the difference in said distances, said pusher having a bias toward its extended position exceeding that of said biasing means.

2. A device according to claim 1, in which said base provides unobstructed access to said dispenser for the removal thereof when said pusher is in its extended position.

3. A device according to claim 1 including a pin and slot connection between said pusher and said driver, the slot having a length at least as great as said differences in distances.

4, A device according to claim 1 including a motor having a crank arm, and a pin and slot connection between said crank arm and said driver.

Claims

1. A device for repetitively dispensing a predetermined quantity of liquid, comprising: a. a dispenser including a positive-displacement pump having an operating member, said operating member being displaceable between an advanced position defined by a stop and a retracted position defined by an adjustable stop, and means biasing said operating member toward the retracted positon; and b. an assembly including a base for removably supporting said dispenser, a power-operating driver movably supported on said base for movement between an extended position and a withdrawn position, the distance between said positions of said driver exceeding the distance between said positions of said operating member, and a pusher member slidably carried on said driver for engaging said operating member to displace it to said advanced position of said operating means and for accommodating the difference in said distances, said pusher having a bias toward its extended position exceeding that of said biasing means.

4. A device according to claim 1 including a motor having a crank arm, and a pin and slot connection between said crank arm and said driver.