Method And Apparatus For The Suction Removal Of A Liquid

Abstract

A method and apparatus for removing a liquid sample from a liquid-containing receptacle without contaminating the remaining liquid, characterized by the provision of a suction conduit that is arranged in spaced relation above the liquid in the receptacle, said suction conduit having an inlet orifice that is spaced a given distance from the liquid level. A source of suction pressure is connected with the other end of said suction conduit to establish a uniform flow of fluid from the receptacle to the suction conduit. Means are provided for continuously lowering the inlet orifice end of the suction conduit at the same rate that the level of liquid decreases, thereby to maintain constant the given spacing distance between the inlet orifice and the liquid level and, consequently, the flow of liquid from the receptacle into the suction conduit.

Description

This invention relates to an improved method and apparatus for removing samples of liquid from a liquid-containing receptacle in a contamination-free manner. More particularly, the liquid is removed from the receptacle by means of a suction conduit the outer surfaces of which are prevented from coming into contact with the liquid in the receptacle.

It is well known in the prior art to remove liquid from a receptacle by means of a syphon tube, suction conduit, or the like. One problem inherent in such known devices is that the inlet orifice of the vacuum pressure removal means is submerged below the upper level of the liquid in the receptacle, whereby the liquid in the receptacle is subject to contamination by materials carried by the outer surfaces of the removal means. In the case where liquid samples are to be removed from a plurality of receptacles by a single suction removal means, quite often the specimen from one receptacle clings to the outer surfaces of the suction means and is transferred thereby to a subsequent receptacle. This contamination is particularly undesirable when analyzing various liquids such as blood with which various reactants are mixed prior to examination by photometric analyzing means of the type in which a light beam is directed through the mixture to determine a physical characteristic thereof (for example, the opacity of the mixture). Also, this buildup of residues on the outer surfaces of the suction removal means forms an undesirable porous layer that often acts as a sponge for absorbing materials that would contaminate liquid in a subsequent receptacle into which the suction removal means are submerged. The present invention was developed to avoid the above and other drawbacks of the known suction removal systems.

Accordingly, the primary object of the present invention is to provide an improved method and apparatus for removing a liquid sample from a receptacle by means of a suction conduit the end and outer surfaces of which are maintained out of contact from the liquid in the receptacle whereby contamination of liquid in the receptacle is avoided. In accordance with the present invention, the suction conduit is arranged with its inlet orifice spaced a given distance above the level of the liquid in the receptacle, whereupon suction is applied to the other end of the suction conduit to initiate discharge flow of the fluid from the receptacle into the suction conduit. Means are provided for lowering the inlet orifice end of the suction conduit at the same rate that the level of the liquid descends during removal of the liquid from the receptacle, thereby to maintain constant both the spacing distance between the inlet orifice and the liquid level, and the flow of liquid from the receptacle into the suction conduit.

In accordance with a further object of the invention, after the desired quantity of fluid has been removed from the receptacle, the suction conduit is maintained stationary while the suction force continues to be applied to the other end of a suction conduit. Consequently, the flow of liquid from the receptacle into the suction conduit will be terminated, and the ambient gaseous fluid (normally air) will be drawn through the suction passage to completely dry the inner wall surfaces thereof.

In accordance with a further object of the invention, the inlet orifice end of the suction conduit is displaced vertically relative to the level of the liquid in the receptacle by means of rotary cam and axially displaceable cam follower means. The cam configuration is such that initially the inlet orifice end of the suction conduit is quickly brought from a remote position to the desired position spaced from the liquid level, whereupon the inlet orifice end is continuously lowered at a uniform rate corresponding with the rate of decrease of the liquid level. The inlet end of the suction conduit is then quickly returned to its original remote position by the cam follower means, whereupon a further receptacle may be conveyed in position for removal of a specimen sample.

Other objects and advantages of the present invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawing, in which:

FIG. 1 is a diagrammatic illustration of the liquid sample removal means of the present invention; and

FIG. 2 is a detailed diagrammatic illustration of the contamination-free manner in which the liquid sample is drawn from the upper surface of the liquid in the receptacle.

Referring first to FIG. 1, a succession of identical receptacles 2 are transported by conveyor means 4 longitudinally of a trough 6 containing a liquid bath 8. The receptacles contain uniform quantities 10 of a liquid to be analyzed (for example, blood specimens). Preferably the liquid bath has a controlled temperature (which, in the case of a blood specimen, may be 37.degree. C.), whereby the temperature of the liquid specimen is controlled accordingly.

In accordance with the present invention, means are provided for removing portions of the liquid specimens from a receptacle without contaminating the remaining liquid. To this end, there is provided a suction conduit 12 having at one end an inlet orifice 12a. Connected with the other end of the suction conduit is a source of vacuum pressure 14. The inlet orifice end of the suction conduit 12 is connected with a vertically-arranged axially-displaceable cam follower member 16 that is elevated and lowered, respectively, relative to the corresponding receptacle 2 by the rotary cam member 18. The configuration of the cam 18 is such that when a given receptalce is conveyed to the sample removal position I directly beneath the cam follower, the cam follower is displaced quickly downwardly by the cam 18 to lower the inlet end of the suction conduit from a remote position to a position immediately adjacent, but spaced the given distance "d" (FIG. 2) from, the level of the liquid. Owing to the vacuum established within the suction conduit by the vacuum pressure source, there is initiated a flow of liquid from receptacle 2 to the suction conduit 12 via orifice 12a. As shown in FIG. 2, this fluid flow is established with the lower end and outer wall surfaces of the suction conduit completely out of contact from the liquid 10 in the receptacle 2. Owing to the contour of the rotary cam, the inlet orifice end of the suction conduit is progressively lowered at a given rate substantailly equal to the rate at which the liquid level decreases during the suction removal process, whereby the spacing distance "d" between the inlet orifice 12a and the liquid level, and the flow of liquid into the suction conduit, are maintained constant.

When the cam follower 16 reaches its lower limit of travel, the suction on the suction end of the conduit 12 is continued, whereby ambient air is drawn through the conduit to prevent drops of the removed sample from being discharged by gravity from the suction conduit into the receptacle, or from forming an undesirable film or residue on the inner wall surface of the suction conduit. At the end of this drying instant, the cam follower is quickly displaced upwardly by the biasing spring 20 and the contour of the cam 18 to rapidly withdraw the inlet end of the suction conduit to its initial remote position. Preferably the conveyor 4 is a step-by-step conveyor having dwell periods slightly greater than the time required for one complete revolution of the cam 18.

It is important to note that, in accordance with the present invention, at no time does the outer surface 12b of the suction conduit 12 come into contact with the liquid 10, whereby contamination of the fluid in any receptacle by the suction conduit is positively avoided.

While in accordance with the Patent Statutes the best form and embodiment of the invention has been illustrated and described, it will be apparent that various modifications may be made without deviating from the disclosed inventive concepts.

Claims

What is claimed is:

1. Apparatus for removing a quantity of liquid from a receptacle without contaminating the remaining liquid, comprising

a. a suction conduit having at one end an inlet orifice;

b. means supporting said suction conduit above the liquid contained in said receptacle with the inlet orifice spaced a given distance from the liquid level;

c. a source of suction pressure connected with the other end of said suction conduit, the pressure of said suction source being sufficient to establish a flow of liquid from said receptacle into the suction conduit via said inlet orifice; and

d. means for continuously lowering the inlet orifice end of said suction conduit at the same rate that the level of liquid in the receptacle decreases upon removal of liquid therefrom, thereby to maintain constant the spacing distance between the liquid level and inlet orifice, and the flow of liquid from said receptacle into said suction conduit via said inlet orifice, whereby the lower end and outer surfaces of the suction conduit are maintained free from contact with the liquid in the receptacle.

2. Apparatus as defined in claim 1, wherein said suction conduit lowering means comprises cam and follower means including a rotary cam, an axially reciprocating cam follower member, and spring means biasing said cam follower member into engagement with said rotary cam.

3. Apparatus as defined in claim 2, wherein the cam surface of said rotary cam has a configuration to effect, in succession:

a. rapid displacement of the inlet orifice end of said suction conduit from a position remote from the liquid level to the position adjacent and spaced the given distance from said liquid level;

b. progressively lowering of the inlet orifice end of the suction conduit at a uniform rate; and

c. rapid withdrawal of the inlet orifice end of the suction conduit from the receptacle.

4. Apparatus as defined in claim 2, wherein said suction conduit remains connected with said suction pressure source when the orifice end of the suction conduit reaches its lower limit of travel, whereby the flow of liquid to said suction conduit is terminated and ambient drying fluid is drawn into the suction conduit.