Fraction Dispenser

Abstract

A fraction dispenser for delivering predetermined quantities of a sample into receptacles. The invention comprises a group of receptacles individually supported in receptacle racks and a cam driven by a reversible motor, whereby the receptacles are shifted laterally and longitudinally so as to be in position to accept dispensing of the sample.

Description

BACKGROUND OF THE INVENTION

This invention relates to a fraction dispenser for dispensing predetermined measured quantities of a sample into receptacles.

More specifically, the invention is concerned with improvements in a fraction dispenser and has for its object an improved fraction dispenser incorporating a simplified device for shifting receptacles to accept delivery of predetermined amounts of liquid, resulting in compact construction, stable operation, and trouble-free maintenance.

SUMMARY OF THE INVENTION

Basically, the fraction dispenser of this invention delivers a fraction of liquid into a series of receptacles. The dispenser comprises a reservoir for the liquid, the reservoir being carried by a balance beam in such a way as to locate an outlet of the reservoir over a case holding racks of receptacles. The invention comprises means for shifting the receptacle racks laterally and longitudinally.

According to this invention, the receptacles are shifted laterally and longitudinally so as to be in proper position for delivery of liquid from the reservoir by the action of a single cam driven by a single reversible motor, thereby avoiding the use of complicated combinations of parts such as links, rods, and cams.

The invention also provides a safety device protecting the motor against possible overheating in the event that the receptacles are prevented from being shifted by an obstruction, thereby eliminating the necessity of visual control.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be more particularly described by way of example, with reference to the accompanying drawings; in which:

FIG. 1 is a plan view of the main part of a fraction dispenser according to the invention, partly broken away to show the means for feeding receptacle racks laterally and longitudinally;

FIGS. 2(a) and 2(b) are plan views of receptacle racks arranged in a rectangular-shape case;

FIG. 3 is a sectional view showing the relation between a driving motor and a cam;

FIG. 4 is a schematical view illustrating the operation of the lateral feeder pawls;

FIG. 5 is a schematic view illustrating the operation of the lateral feeder pawls; and

FIG. 6 is a circuit diagram.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the invention, the fraction dispenser consists essentially of two main sections, one of which is a rectangular-shape case 1 and the other is a group of receptacles 51 which are individually supported in receptacle racks A and B. The case 1 includes a lid plate 2 and an intermediate floor 1.sub.2 between which is provided a rack shifting arrangement. The lid plate 2 is defined by framework 3, so as to provide space for the receptacle racks to move laterally and longitudinally therein. The racks A and B are placed upright on the lid plate 2 with unoccupied spaces 4 as illustrated in FIG. 2, thereby allowing the racks to move laterally and longitudinally.

In each space 4 there are provided a pair of openings 5.sub.1, 5.sub.1 and 5.sub.2, 5.sub.2 for passing lateral feeder pawls 41 therethrough which are moved therein to push all the racks of one row in the lateral direction. Also, in each space 4 there are lengthy openings 6.sub.1 and 6.sub.2 for moving longitudinal feeder pawls 27 therein which push the racks receptacle by receptacle in their longitudinal direction.

Between the lid plate 2 and the intermediate floor 1.sub.2, there is provided a disc-shape cam 9 driven by an electric motor 7 which is mounted under the intermediate floor 1.sub.2 as illustrated in FIG. 3. The rotary shaft 8 of the motor has a threaded portion 18, in which a spring washer 17 is fastened by a nut 19. The cam 9 is freely carried by the rotary shaft 8 of the motor. When the nut 19 is tightened, pressure is exerted on the cam surface 12, thereby securing the cam 9 to the rotary shaft 8 of the motor. If an obstruction occurs preventing the cam from rotating, slipping will be caused between the cam surface 12 and the washer 17, thereby enabling the motor 7 to rotate continually. This protects the motor against overheating.

The cam 9 has pins 10 and 11 on its surface, and each pair of pins 10.sub.1, 10.sub.2 and 11.sub.1, 11.sub.2 are placed symmetrically in the radial direction as illustrated in FIG. 1. All the pins are equally projected towards the receptacles 51 arranged on the lid plate 2. The cam 9 is provided with four indentations 13, 14, 15, and 16, which are spaced at given intervals. These indentations are engaged by the actuators of microswitches, whereby the switches are appropriately closed and opened to energize and deenergize the motor 7, as is described hereinafter.

The longitudinal feeder pawls 27 are uprightly supported by pawl carriers associated with longitudinal feeder plates 28, which are displaceably held by holding posts 29 and guide pins 30. The feeder plates 28 are reciprocally moved substantially in parallel with the lengthy openings 6, thus enabling the pawls 27 to reciprocate therein. The feeder plates 28 are connected with the pins 10 and 11 on the cam 9 by means of arms 31, which have slots 32 for receiving these pins. Accordingly, when the pins are engaged in the slots 32 of the arms, the feeder plates 28 are caused to reciprocate as the cam 9 rotates in the directions of a and b. During this reciprocal movement the feeder plates 28 are vertically displaced under the action of a guide 34, thereby enabling the upright pawls 27 to fluctuate in relation to the receptacle racks. The guide cam 34 is generally made of resillient material, including a bent portion 35, a horizontal cam face 36 and a slant cam face 37. The feeder plates 28 are provided with pins 33, which are extruded sideways from the feeder plates 28 so as to mount on the guide cam 34. As the pins 33 slide on the guide cam, the feeder plates 28 are caused to be displaced upwardly as illustrated by the dotted lines in FIG. 4. In the bottom of receptacle racks A and B are provided projections 39 to be hooked by the pawls 27. As the feeder plates 28 are elevated, the pawls 27 are also raised to engage one of the projections 39, thus advancing the racks in their longitudinal direction. The distance to be fed is arranged to be P, which is equal to the distance between the centers of the adjacent receptacles. This intermittent motion of the racks is achieved by disengaging the pawls 27 out of the projections 39 when the pins 33 fall from the terminating edge 38 of the horizontal cam face 36. When the feeder plates 28 are moved backwards, the pins 33 pass underneath the guide cam 34, thus preparing for the next feeding operation. In this respect, the slant cam face 37 allows the pins 33 to pass thereunder by virtue of its resilient property. In order to achieve longitudinal feeding of the racks over the distance P the size and length of the guide cam 34 and the feeder plates 28 must be properly determined.

The lateral feeding of the receptacle racks is effected by lateral feeder pawls 41 carried by respective carriers 40.sub.1 and 40.sub.2, which are associated with lateral feeder plates 42 having a pair of slots 43 and projecting sides 45. The projecting sides 45 are engaged by the pins 10 and 11 on the cam 9, thereby causing the feeder plates 42 to reciprocally move as the cam 9 is rotated in the directions of a and b. However, this reciprocal movement of the feeder plates is restricted by stopper pins 44 received in the slots 43. The feeder plates 42 are helped by springs 46 to return to their original position. The upright pawls 41 engage the sides of the receptacle racks A.sub.1 and B.sub.1 to push all the racks of one row sideways.

The motor 7 is rotated in opposite directions by the actuation of switches 20, 21, 22.sub.1, 22.sub.2. The switch 20 has a one-way actuator 23 which is closed only when the actuator is in contact with the cam rim 12 on its rotation in the direction of b. In contrast, the switch 21 is closed as long as the actuator 24 thereof is in contact with the cam rim 12, regardless of the direction of the cam's rotation. The switches 22 are provided with levers 25 protruding outside the case 1, which are to be engaged by the end face of the rack when the rack is completely shifted from one row to the other as illustrated in FIG. 2. Only slight pressure is required to close the switches.

Referring to FIG. 6, in which an energizing circuit for the motor 7 is shown, a relay 47 for starting the motor is closed when it receives signals indicating that the receptacle has been filled with a predetermined amount of liquid. Many methods for measuring the quantity of liquid can be selected. For example, a droplet counting method can be employed, wherein the final droplet of liquid produces the signal to the relay 47, thereby enabling the relay to close from the left-hand position to the right-hand position in FIG. 6. Hence, a circuit of S-22-20-21-47-48-49-7-T is completed to start the motor 7, thereby causing the cam 9 to rotate in the counter-clockwise direction indicated by an arrow a in FIG. 1. The circuit represented by the solid lines in FIG. 6 indicates that the receptacle racks A and B are in position as shown in FIG. 2 and that the cam 9 is in position as shown in FIG. 1. When the cam 9 is rotated in the direction of a, the actuators 23 and 24 come into circumferential contact with the cam, thereby closing the switches 20 and 21 as illustrated by dotted lines in FIG. 6. The relay 47 does not close until it receives the signal that the receptacle has been filled with liquid. When the motor 7 starts, the relay 47 is opened to complete a circuit of S-22.sub.1 -20-49-7-T, thereby enabling the motor to continue its rotation in the direction of a.

As the cam 9 is rotated, the pins 10 push the arms 31, causing the longitudinal feeder plates 28 to move longitudinally. During the movement, the feeder plates 28 are displaced as described above, thereby causing the pawls 27 to engage the projections 39 in the underface of the racks 51. Thus the racks 51 are shifted into the spaces 4 by the distance P, whereby the filled receptacle 51.sub.1 is replaced by the adjacent empty receptacle 51.sub.2 so as to accept droplets of liquid from a reservoir (not shown). When the second empty receptacle takes a position corresponding to fitting of the actuator 23 of the switch 20 in the indentation 14 of the cam to open the switch, the circuit of S-22.sub.1 -20-21-50-7-T is completed for reversing the rotation of the motor 7. Accordingly, the cam 9 is reversely rotated in the direction of b leaving the actuator 23 in circumferential contact with the cam. However, as described above, the actuator 23 is a one-way actuator so that the non-actuation of the switch 20 is maintained until the actuators 23 and 24 come into engagement with the indentations 13 and 16. When the actuators 23 and 24 are in engagement with the indentations 13 and 16, the motor 7 is stopped. As the cam 9 is reversely rotated in the direction of b, the longitudinal feeder plates 28 are moved rearwardly to prepare for the next feeding operation.

When the next empty receptacle 51.sub.2 has been filled with a predetermined amount of liquid the relay 47 resumes operation, whereby the same procedures as mentioned above are followed. In this way, the receptacles 51 are filled with liquid one by one. When all the receptacles in a rack are filled with liquid, i.e., the rack is completely shifted in the space 4 as shown in FIG. 2, the top end thereof presses the lever 25 to connect the switches 22.sub.1 and 22.sub.2 to the circuit indicated by the dotted lines in FIG. 6. In this situation, the actuator 23 of the switch is in contact with the indentation 14 of the cam after the cam has continued to rotate in the direction of a as a result of the closed circuit of S-22.sub.1 -22.sub.2 -49-7-T, which was effected by the actuation of the switches 22.sub.1 and 22.sub.2. As the cam is further rotated, the pins 10.sub.1 and 10.sub.2 are separated from the arms 31.sub.1 and 31.sub.2 and engage the projecting sides 45.sub.1 and 45.sub.2 of the lateral feeder plates 42 whereby the lateral feeder plates 42 are pushed against the springs 46. Thus, the upright feeder pawls 41 move all the receptacle racks of each row sideways, thereby emptying the spaces 4 occupied by the racks as illustrated in FIG. 2. When the racks are shifted, the switches 22.sub.1 and 22.sub.2 are returned to the condition indicated by the solid lines in FIG. 6. On the other hand, the actuator 24 of the switch 21 is in contact with the cam rim 12, and maintains its actuation position, thereby completing a circuit of S-22.sub.1 -20-21-50-7-T to reverse the rotation of the cam to the direction of b. As the cam is rotated in the direction of b, the pins 10.sub.1 and 10.sub.2 come into engagement with the arms 31, and the pins 11.sub.1 and 11.sub.2 come into engagement with the projecting sides 45, thereby enabling the longitudinal feeder plates 28 and the lateral feeder plates 42 to return to their original position, where each feeder plate starts the next feeding operation. The returning of the lateral feeder plates 42 is aided by springs 46.

After a single cycle of lateral and longitudinal feeding is thus completed, the same procedure is followed repeatedly, thereby achieving an automatic replacement of receptacles without the use of a complicated combination of parts, such as links, cams, switches and rods. The replacement of receptacles is accomplished mainly by a single cam driven by a single reversible motor, resulting in a simplified and compact device. Also the device is lightweight and may easily be carried. The simplified construction helps avoid failures and problems thereby leading to increased reliability and stability.

It will be understood that it is intended to cover all changes and modifications of the preferred embodiment of the invention herein chosen for the purpose of illustration which do not constiture departure from the spirit and scope of the invention.

Claims

What is claimed is:

1. A fraction dispenser comprising:

1. a plurality of receptacles supported in a plurality of racks;

2. means for dispensing samples into said receptacles as they are individually positioned under said dispensing means; and

3. means for shifting said plurality of racks in lateral and longitudinal directions to position said racks with respect to said dispensing means so that the receptacles of respective racks are sequentially individually positioned under said dispensing means, said shifting means comprising:

a. driving means;

b. a cam having projection means thereon and rotatably connected to said driving means;

c. first means operative to be selectively engaged by said projection means and operative in response to rotation of said cam to shift said racks in the longitudinal direction;

d. second means operative to be selectively engaged by said projection means and operative in response to rotation of said cam to shift said racks in the lateral direction; and

e. means associated with said cam, and driving, first and second means operative to control rotation of said cam to selectively engage said first and second means.

2. The combination as claimed in claim 1 and wherein said cam is disc-shaped and said projection means comprise a plurality of pins connected to said cam.

3. The combination as claimed in claim 2 and wherein said first means comprises:

a. a plurality of arms having slots operative to be engaged therein by said plurality of pins;

b. at least one longitudinal feeder pawl associated with each of said plurality of arms;

c. means connecting each of said longitudinal feeder pawls to said plurality of arms operative to move said longitudinal feeder pawls in the longitudinal direction in response to rotation of said cam; and

d. guide means for moving said longitudinal feeder pawls in a vertical direction during at least a portion of the movement of said longitudinal feeder pawls in the longitudinal direction.

4. The combination according to claim 3 and wherein said guide means comprises a guide cam and a guide pin associated with each of said longitudinal feeder pawls, said guide cam having a bent portion, a horizontal portion and a slanted portion, said guide pin being connected to said connecting means and operative to pass over each of said cam portions in succession.

5. The combination according to claim 1 and wherein said second means comprises:

a. a plurality of lateral feeder plates having a projecting side operative to be engaged by said plurality of pins;

b. at least one lateral feeder pawl associated with each of said plurality of plates; and

c. means connecting each of said lateral feeder pawls to said plurality of plates operative to move said lateral feeder pawls in a lateral direction in response to rotation of said cam.

6. The combination according to claim 4 and wherein said driving means comprises an electric motor and wherein said control means comprises a plurality of indentations in the surface of said disc-shaped cam, a plurality of switches having arms operative to be engaged by said indentations in said cam surface operative to actuate said switches responsive to rotation of said cam to thereby control rotation of said cam by energization and de-energization of said electric motor.

7. The combination according to claim 5 and wherein said driving means comprises an electric motor and wherein said control means comprises a plurality of indentations in the surface of said disc-shaped cam, a plurality of switches having arms operative to be engaged by said indentations in said cam surface operative to actuate said switches responsive to rotation of said cam to thereby control rotation of said cam by energization and de-energization of said electric motor.

8. The combination according to claim 1 and wherein said driving means comprises an electric motor having a shaft with a threaded portion thereon, said cam being freely carried on said shaft, and a spring washer supported on said shaft by a nut operative to exert pressure on said cam to rotate said cam in response to rotation of said shaft.