Sample Conveyors

This invention relates to sample conveyors for measuring systems, more particularly to sample conveyors suitable for use in systems for making repeatitive measurements on a large number of consecutive samples; it also relates to individual components of such conveyors and in particular to cassettes for receiving a plurality of samples and enabling the same to be handled en bloc.

An important but not exclusive use of the invention is in systems for counting the radio-activity of samples in test tubes or vials. Most present art liquid scintillation counters use automatic sample changers comprising a sample conveying chain conveyor. All the samples loaded in the conveyor are brought consecutively to an elevator which moves down the sample to a counting station where its activity is determined and then returns the sample to the same link of the conveyor. Automatic sample changers of this kind are simple and reliable but their capacity is limited to the number of links in the conveyor, they are bulky and the samples must be placed in the chain links one at a time.

Another prior art automatic sample changer comprises trays or racks into which samples can be placed outside the apparatus, the trays or racks then being placed in the changer. A mechanism which is much more complex and slower than the conventional elevator system is then needed to transfer the samples to the counting station.

It is an object of the invention to provide a sample conveyor for measuring systems which improves upon the prior art devices and has the advantages of the tray or rack systems while making it possible to retain an elevator system.

According to an aspect of the invention, there is provided a sample conveyor for a measuring system, comprising: a plurality of cassettes each provided with sample receiving locations distributed regularly in the cassette and each having mechanical means for supporting a sample at each said location; means for moving said cassette consecutively and stepwise along a closed path for sequentially bringing said locations to a transfer station; and means at said transfer station for forcibly opening said mechanical means so that the sample in said cassette can be moved out of the cassette.

The means for mechanically supporting a sample typically consists of bottom wall means. Such bottom wall means may be in the form of a pair of confronting lips at each sample receiving location. The sample is of such size as to be supported by the lips when the latter are in released condition. The system includes a mechanism which, when operated, spreads apart the lips. That mechanism may be constituted by a stationary ramp which cams out the lips when the corresponding location is moved to the transfer station. It may also comprise movable fingers adapted to separate the lips from one another for the time necessary for the sample to be moved across the lips in the upward or downward direction. The advantage of the mechanism including movable fingers over a ramp is that friction is less important and the lips are stressed only for the time necessary for passage of the sample. The lips are for instance carried by vertical resilient legs which tend to restore the lips to their sample retaining position.

The invention will be better understood from the following description of a conveyor which is a non-limitative embodiment of the invention. The description refers to the accompanying drawings.

FIG. 1 is a very diagrammatic plan view showing how the cassette carriers are arranged in a conveyor which brings samples to a counting station in sequence;

FIGS. 2 and 3 are very diagrammatic views of the relative arrangement of a cassette carrier, a cassette, a vial and a transfer elevator in vertical section along line II--II of FIG. 1, with the bottom wall of the cassette open and closed, respectively;

FIG. 4 shows the front and rear portions of a cassette carrier in section along its longitudinal centre plane;

FIG. 5 is a view in elevation of the terminal parts of cassette adapted to be received in the carrier of FIG. 4;

FIG. 6 is a view on an enlarged scale of one of the terminal parts of the cassette of FIG. 5, the view being partly a plan view and partly a mid-height section;

FIG. 7 is a sketch indicating the operative connections between the mechanism for opening the bottom walls of the cassettes and the sample elevator.

Referring to FIG. 1, there is shown the general layout of the conveyor. The conveyor has a plate and a predetermined number of cassette carriers 10 which are arranged to be moved on the plate along a planar path indicated by arrows f. The plate has slide ways 40 which retain the carriers 10 located in two parallel rows on either side of a mid plane of the plate. The space behind the last carrier of each row forms a passage 11 via which the first carrier of each row can be moved to the back of the other row. Means including two pushers 41 and 42 or the like are provided for advancing each row by steps equal to the width of a carrier. The system also includes means for advancing the first carrier of each row stepwise to the back of the other row. Such means includes endless belts 43 and 44 having projecting pins for engagement with the carriers.

Each carrier is adapted to receive a cassette 12. A single cassette 12 is shown diagrammatically in FIG. 1. That cassette has n sample receiving locations. Each sample consists of a bottle or vial containing a liquid solution if the system is a liquid scintillation spectrometer. Each sample 13 is separated from the adjacent sample by a distance equal either to the incremental movement or step of the carrier 10 or to an integral multiple of such step.

A counting system (not shown) is associated with and disposed below the plate. A transfer mechanism is provided for bringing a sample vial retained by the carrier at the transfer station from the cassette 12 to a counting station, then for returning it to its initial position.

The transfer mechanism comprises an elevator which can be of the type disclosed in U.S. Pat. No. 3,809,897 assigned to the assignee of this invention and to which reference may be had. The platform 14 of the elevator which supports the sample vial during its upward and downward movements, has been shown in FIGS. 2 and 3.

The cassettes 12 have a base or bottom wall for retaining the vials while the cassettes are handled or are moved on the plate and for allowing the vials to pass through so that they can be transferred to the counting station.

The cassette which is shown diagrammatically in FIGS. 2 and 3 and partially in FIGS. 5 and 6 consists of a molded part of a slightly resilient material, typically plastics material. The cassette frame has lateral vertical walls 15 and vertical end walls 16. The lateral walls 15 have flangers 17 adapted to be supported by the carrier 10. The cassettes can be positioned and removed by means of a handle 18. The lateral walls of the cassette are interconnected by integral molded transverse partitions 19 separating chambers or locations for receiving vials 13, there being e.g. 10 such chambers or locations. In the embodiment shown, each vial receiving chamber has a bottom wall adapted to be opened independently of the bottom wall of the other chambers; the bottom wall consists of two lips 20 which project transversely inwardly from two legs 21 integral with the upper portion of the cassette 12, which is thicker than the leg and constitutes the frame. Each leg 21 is formed below the lip 20 with a projection 21b which enables a finger 22 at the transfer station to move the leg 21 outwardly far enough for the vial to pass through the lips 20 (FIG.3).

A mechanism for actuating the fingers 22 and the elevator in time relation is illustrated in simplified and diagrammatic form on FIG. 7. It includes a motor 47 whose shaft carries a rotating cam 48 and a disk 49.

The cam 48 is formed with a groove 50 which retains a roller carried by a lever 51 connected by a flexible web or wire 52 to a toggle 53 which moves the finger 22 from the position illustrated in solid line to the position illustrated in dash-dot line upon a 90.degree. rotation of cam 48. The cam is also formed with a notch 54 cooperating with switches 55 and 56 which are closed except when confronting the notch and are serially mounted in an energization circuit of motor 47.

A lever 57 is pivotally connected with disk 49 and controlls the platform 14 via a linkage which need not be described since it may be quite similar to that described in U.S. Pat. No. 3,809,897.

Referring to FIG. 4, there is shown a carrier 10 having a frame whose lateral walls 23 are interconnected at one end by a cross-partition 24 which extends over most of the height of the carrier 10 and at the other end by a partition 25 appreciably lower. The bottom wall of the carrier 10 is open; however, for increased rigidity, the lateral walls 23 are interconnected by horizontal ribs 26. The carrier 10 is so shaped that the legs 24 of the cassette 12 in the carrier can be bent apart from one another; to use the available space more efficiently the lateral walls 23 are cut to leave castellations 27 opposite the positions of the legs. The transverse dimension of the carriers can therefore be only slightly greater than the transverse dimension of the cassettes.

The carriers are associated with means for guiding them onto the plate and for driving them stepwise. Referring to FIG. 4, the end walls 24, 25 of each carrier have two flanges which straddle the slideways 40 of the plate during the movement of the carriers 10 in the rows. The top flange 29 of the rear wall 24 is formed with a recess aperture adapted to receive a programming plug giving automatic determination of the parameters of the required measurements. Such plug can be e.g. of the type disclosed in U.S. Pat. No. 3,749,916 assigned to the assignee of the present invention, or in French Patent Application No. 74.23515.

For the stepwise drive of the carriers near the transfer station, the lateral walls 23 are formed with slots 30 engageable by the pins of the drive belts 43, 44. The slots 30 are distributed at equal spacings and there are e.g. three slots in each lateral wall. The cassette is so designed as not to interfere with the engagement of the pins and to allow the connecting ribs 26 to pass; accordingly, the cassette shown in FIGS. 5 and 6 is formed with straight-walled recesses 31, for association with the ribs 26, and with wider slots 32 which extend beyond the slots 30.

The carrier shown in FIG. 4 can receive not only cassettes of the kind shown in FIGS. 5 and 6 (such cassettes taking up the entire width of such carrier) but also cassettes for samples having a smaller transverse size. Of course, it would be possible to provide cassettes in which samples contained in narrow vials or list tubes are distributed at the same interval, but then the capacity of the system would not be fully used. To obviate this disadvantage, cassettes other than the regular cassettes shown in FIGS. 5 and 6 can be provided in which the sample-receiving locations are distributed at intervals representing a fraction (generally one-half) of the interval between the sample-receiving locations in the regular cassette. In this case, if the mechanism for driving the carriers is designed to optionally move them by increments of half a normal step, the capacity can be almost doubled (19 half-diameter sample bottles being accomodated in one carrier). A sample identification probe 46 is then provided (FIG. 1). The ribs 26 of the carrier shown in FIG. 4 are such that modified cassettes of the type just described can be used, since the ribs 26, which are in positions where they do not exhibit the passage of the sample bottles, are of reduced longitudinal size. The program plug 35 carried by the rear cross-wall 24 of the carrier can as well carry a coded indication for a sensor to determine whether the arriving carrier contains a standard 10-sample cassette or a 19-sample cassette.

Carriers compatible with several types of cassettes (the samples being disposed at different intervals according to the type of cassettes) may be used as well when the samples are removed otherwise than through the bottom of the cassette. Compatibility is even easier in the case of upwards removal by grippers which engage with the neck of a vial, test-tube or test-tube container of any diameter in the cassette.

Since the operation of the facility hereinbefore described is apparent from the foregoing description, it will merely be summarized, assuming that all the carriers 10 contain standard cassettes of the kind shown in FIGS. 5 and 6. No reference will be made to the mechanisms for moving the rows of loaders since there are many known mechanisms of such a kind, nor will there be any reference to means for carrier identification. It is sufficient to note that the carriers may be numbered sequentially, e.g. from 1 to 40. An identification mark on the carrier numbered 1 serves to reset a counter whenever that carrier passes by the counting station, and the counter subsequently gives a continuous display of the number of the cassette carriers present at the transfer station.

Assuming that the carriers are initially grouped in two complete rows, with the carriers of the upper row in the position illustrated in FIG. 1 and the carriers of the lower row moved by one step to the left, the stepwise belt 43 for the carrier of the lower row operates and in a first phase brings the first sample location 13 opposite the transfer station 58 (as shown in dash-dot lines in FIG. 1). If a detector system at the transfer station, for instance, including a light emitter 33, and a detector 34 detects the presence of a sample, an operating sequence of the transfer mechanism is initiated.

In initial condition, cam 48 is an angular position for which switch 55 confronts notch 54 and is open while switch 56 is closed. When the motor is energized by a separate circuit, cam 48 rotates and switch 55 closes thereby maintaining energization of motor 47. During initial rotation of the motor and cam, lever 51 is moved angularly and drives the fingers 22 apart. The sample then rests onto the platform 14. For that time period, disk 49 is also rotated and drives lever 57 which takes up the lost motion of its connection with a second lever without moving the wheel 59 which remains in its upper position (in dash-dot line on FIG. 7). Continuing movement of motor 47 retains the fingers 22 in spaced conditions and causes downward movement of wheel 59. When the cam 48 has moved by 180.degree. from its initial position, switch 56 opens and the motor stops. During the final portion of the angular motion of the cam, the fingers 22 move back and release the legs of the cassette which return to their rest condition.

The sample is then counted under conditions (e.g. precount, pretime, width of energy windows . . . ) which may be automatically adjusted in response to the information read from the plug 35 (FIG. 4).

After the counting operation has been completed, motor 47 is energized again. Cam 48 rotates and closes switch 56. The fingers 22 are moved apart while the platform 14 lifts back the sample to the cassette to a level above the lips 20. Last the lips close and switch 55 opens. The platform 14 can have a flange-like edge 36 which determines the appropriate height by bearing on an abutment.

The belt mechanism then moves the carrier on by one step and the same sequence is repeated.

The invention therefore provides a sample conveyor which is very convenient to use since prefilled cassettes can be substituted rapidly and conveniently into captive cassette carriers for other cassettes. None of the advantages of conventional elevator mechanism is lost. The conveyor is very flexible since it is adaptable to samples of different kinds and transverse sizes, with optimum use of available capacity.