US3401839A

US3401839A - Liquid sampling and dispensing device

Info

Publication number: US3401839A
Application number: US641760A
Authority: US
Inventors: Christie Theodore
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1967-05-29
Filing date: 1967-05-29
Publication date: 1968-09-17
Anticipated expiration: 1985-09-17

Description

3 Sheets-Sheet 1 T. CHRISTIE LIQUID SAMPLING AND DISPENSING DEVICE Sept. 17, 1968 Filed May 29. 1967 Sept. 17, 1968 T. CHRISTIE LIQUID SAMPLING AND DISPENSING DEVICE 3 Sheets-Sheet 2 Filed May 29, 1967 S MW RH ON T 1m W E I W D O n. T

Sept. 17; '1968 'r. CHRISTIE LIQUID SAMPLING AND DISPENSTNG DEVICE 3 Sheets-Sheet 5 Filed May 29, 1967 IN v E m'oa Tneooans Cums:

United States Patent 3,401,839 LIQUID SAMPLING AND DISPENSING DEVICE Theodore Christie, Chicago, Ill., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed May 29, 1967, Ser. No. 641,760 8 Claims. (Cl. 222-137) ABSTRACT OF THE DISCLOSURE An automatic diluter having a pair of motor driven plunger-type syringes for picking up precisely predetermined quantities of sample and diluent from separate supplies and for dispensing these quantities in common to form a diluted sample. Both plungers are driven by a single unidirectional electrical motor which is coupled to the plungers through a motion converting mechanism which changes the rotary output of the motor to the reciprocating motion necessary for plunger operation. Respective adjustable lost motion connections are provided between the motor and each of the plungers so that the stroke length of each of the plungers may be selected according to the respective portions of sample and diluent desired in the diluted sample. A control switch is provided in the motor supply circuit and is operated by a pair of camming surfaces which are rotated by the motor to interrupt motor operation when the plungers are at each limit of their respective reciprocations in order to automatically provide a hiatus between the pick-up and dispensing operations. A manually operable mode selector switch is connected in parallel with the control switch and has one position for interrupted operation in which it momentarily closes the motor supply circuit to permit the control switch to reclose and another position for continuous operation in which it maintains the motor supply circuit closed to override the operation of the control switch.

Summary of the invention This invention relates to automatic diluters and, more particularly, to diluters of the type to automatically form diluted samples containing precisely predetermined portions of sample and diluent.

It is an object of this invention to provide an automatic diluter wherein the drive is provided by a single unidirectional motor. A more specific related object is to provide an automatic diluter employing a single unidirectional motor wherein respective plunger-type syringes are employed to pick up and dispense sample and diluent. Another object is to provide an automatic diluter of the foregoing type wherein the stroke length of the respective plungers may be readily and accurately independently adjusted so that the respective portions of sample and diluent constituting the diluted sample may be precisely controlled.

A further object is to provide an automatic diluter with a single unidirectional motor with the dilute-r capable of operation in either a continuous or an interrupted mode and where, when the diluter is operated in the interrupted mode, a hiatus is automatically provided between the pick-up and dispensing operations. Finally, it is an object of this invention to provide an automatic diluter which is relatively economical and reliable, and yet which is entirely suitable even for the most demanding operation.

Brief description of the drawings Other objects and advantages of the present invention will be apparent upon reading the following detailed description with reference to the attached drawings, in which:

3,401,839 Patented Sept. 17, 1968 "ice FIG. 1 is a perspective view of an automatic diluter constructed in accordance with the present invention;

FIG. 2 is a flow diagram illustrating the operation of the automatic diluter shown in FIG. 1;

FIG. 3 is a front view of the automatic diluter with the front panel removed to expose the motion converting and lost motion portions of the drive mechanism;

FIG. 4 is a side view partly in section with the side panel removed to illustrate the single unidirectional motor and its connection to the motion converting portion of the drive mechanism;

FIG. 5 is a top view of the automatic diluter with the top of the diluter removed to show the motor and control switch for interrupting the operation of the motor; and

FIG. 6 is a schematic of the electrical supply circuit for the motor.

Detailed description of the illustrated embodiment Turning now to the drawings and particularly to FIG. 1 there is illustrated an automatic diluter, indicated generally 'by 11, constructed in accordance with the present invention. The diluter 11 includes a conventional delivery means, in this instance a pipette 12, which is connected at one end of a length of flexible tubing 13 (FIG. 2). In keeping with the normal practice, the tubing 13 is of sufiicient length that the operator may immerse the tip of the pipette 12 in a sample supply to pick up a quantity of sample and then remove the pipette 12 to a dispensing position, typically over a clean vessel for receiving the diluted sample. For convenient storage of the pipette 12 a clamp bracket 14 may be fixed to the diluter housing 15.

Referring to FIG. 2, the automatic diluter 11 includes first and second reversible fluid actuators, as illustrated the plunger-type syringes 16 and 17, respectively, which are drivable in one direction to pick up respective predetermined quantities of sample and diluent from separate supplies and in the other direction to dispense these quantities in common to form the desired diluted sample. More specifically, with the

plungers

18 and 19 at the top of their associated syringe bodies, 21 and 22, respectively, in a prepick-up position the complete system from the outer tip of the pipette 12 to the outer tip of the diluent intake line 23 is filled with diluent. To pick up a predetermined sample quantity, the tip of the pipette 12 is immersed in a sample supply (not shown) and the plunger 18 is driven downwardly a predetermined distance. A spring biased check valve 24 prevents additional diluent from flowing through the hydraulic lines 25 and 26 to fill this increased volume and consequently a quantity of sample equal to the volume of the syringe body 21 above the plunger 18 is drawn into the pipette 12. To prevent contamination of the sample and collection of the sample within the system, the volume of the pipette 12 is preferably larger than the quantity of sample picked up which, for example, in a typical clinical type diluter, may be 0-100 microliters. To pick up the de sired quantity of diluent at the same time, the plunger 19 is driven downwardly a predetermined distance causing the desired diluent quantity to flow from the diluent supply 27 through the intake means 23, a spring biased check valve 28, and the

hydraulic lines

31 and 32 into the portion of the syringe body 22 which is above the plunger 19. As an example, in a typical diluter, the syringe 17 should be capable of picking up 0-40 milliliters of diluent.

Upon the completion of the above described pick-up operation, the pipette 12 is removed from the sample supply and placed over a diluted sample receiving vessel (not shown). To dispense the quantities of diluent and sample previously picked up, the plungers -18 and 19 are driven upwardly. As the plunger 18 is driven upwardly,

diluent flows through the

hydraulic lines

33 and 13 into the pipette 12 forcing the sample quantity out. Likewise, as the plunger 19 is driven upwardly, the check valve 28 prevents return flow to the diluent supply 27 thereby causing the diluent to flow through the hydraulic lines 32, 25, the check valve 24, and the

hydraulic lines

26, 13 to force the predetermined quantity of diluent from the pipeite 12. The velocity of the diluent as it exits from the pipette 12 is generally sufiicient to obtain adequate mixing of the diluted sample.

From the foregoing, it will be understood that the

plungers

18 and 19 are reciprocated relative to their associated

syringe bodies

21 and 22, respectively, to pick up and dispense the desired quantities of sample and diluent. It will also be readily apparent that by maintaining an equality between the downward and upward stroke lengths for each of the

plungers

18 and 19, the amounts of sample and diluent dispensed are equal to the amounts picked up.

Turning now to FIGS. 3-5, the reciprocating drive for the

plungers

18 and 19 is provided by a drive mechanism indicated generally at 41. In accordance with an important aspect of this invention, the drive power is provided by a single unidirectional motor 42, in this instance a conventional electrical motor. In this manner, significant savings in terms of cost and complexity are realized with no loss in precision as will become apparent hereinafter.

To provide a drive speed appropriate for the diluter, typically 6 rpm, the motor shaft 43 may be coupled to the diluter drive shaft 44 through a conventional speed change mechanism 45. To convert the rotary motion of the drive shaft 44 to the reciprocal motion required for operation of the

plungers

18 and 19, the drive mechanism 41 also includes a motion converting mechanism indicated generally by 46. Moreover, in carrying out this feature of the invention, to provide the desired stroke lengths for each of the

plungers

18 and 19, the drive mechanism 41 further includes respective lost motion connections 47 and 48 between the motion converting mechanism 46 and the

plungers

18 and 19.

The motion converting mechanism 46 includes a drive member 51, as illustrated a disk, which is mounted for rotation with the drive shaft 44 by a hub 53. One end of a drive link 54 is pivotally connected at 55 to the disk 51 eccentrically of the drive shaft 44. The other end of the drive link 54 is pivotally connected at 56 to a collar 57 which is mounted for reciprocation along a guide shaft 58. The collar 57 carries a platform 59 and thus as the disk 51 is rotated, the platform 59 is reciprocated along the guide rod 58 with a fixed stroke equal to twice the distance between the drive shaft 44 and the pivot 55.

For most applications of the automatic diluter, the length of the stroke of the platform 59 is considerably greater than the desired length of the stroke of either

plunger

18 or 19. For this reason, to couple the reciprocating motion of the platform 59 to the

plungers

18 and 19 with respective desired reductions in the stroke lengths for each of the plungers, the lost motion connections 47 and 48 are provided. To adapt the diluter for use where different portions of sample and diluent are desired, the amount of motion lost by each of the connections 47 and 48 is preferably independently adjustable. To this end in the illustrated embodiment, the lost motion connection 47 includes a plate 61 to which the plunger 18 is fixed and through which a bolt 62 is threaded. The shank of the bolt 62 freely passes through an aperture in the plate 59 and terminates below the plate 59 in a head 63 which is large relative to the aperture. Similarly, the lost motion connection 48 includes a plate 64 to which the plunger 19 is fixed and through which a bolt 65 is threaded. The shank of the bolt 65 passes freely through an aperture in the plate 59 and terminates below the plate in a head 66 which is large relative to the aperture in the plate 59 through which the shank of the bolt passes.

Guide rods

67 and 68 are passed through the

plates

61 and 64, respectively, to prevent any tendency of the plates to pivot in a horizontal plane. Thus, it will be appreciated that the lengths of the respective strokes of

plungers

18 and 19 may be readily selected by simply turning the bolts 62 and 65. For most purposes, suflicient adjustment sensitivity is available if the bolts 62 and 65 have approximately 32 threads/inch.

At this point it should be noted that the automatic diluter of the present invention may be employed where it is desired to simply dispense constant amounts of diluent such as for purposes of diluting a series of premeasured samples. For this form of operation the lost motion connection 47 is adjustable to a position where the plunger 18 remains at the top of the syringe body 21 as the platform 59 reciprocates.

Also, provision may be made for instance where the

plungers

18 and 19 are of different lengths. To this end adjustable stops 69 and 70 are fixed to the platform 59 and project therefrom to engage the

plungers

18 and 19, respectively, during the upward stroke of the platform 59. The heights of the stops 69 and 70 are adjusted so that the

plungers

18 and 19 both reach the tops of their associated

syringe bodies

21 and 22, respectively, just as the platform 59 reaches the upper limit of its reciprocation.

To maintain the

syringe bodies

21 and 22 stationary during reciprocation of the

plungers

18 and 19, the syringe bodies are fixed to a mounting plate 71 by clamp plates 72 and 73, respectively. The mounting plate 71 is fixed to the diluter housing 15.

Referring now to FIG. 6 in addition to FIGS. 3-5 and particularly to the supply circuit 81 for the motor 42, the supply circuit may be connected to a wall receptacle through a conventional male connector plug 82 and may also include an on-off switch 83, illustrated as a conventional rocker-type switch, and a power-on indicating pilot light 84.

To prevent any loss of sample from the pipette 12 upon the completion of a pick-up operation and during the movement of the pipette 12 from the sample supply to the diluted sample receiving vessel, and to prevent the introduction of air into the pipette 12 upon completion of a dispensing operation, provision is preferably made to automatically interrupt the operation of the motor 42 when the

plungers

18 and 19 are at either of the limits of their respective reciprocations. To this end in the illustrated embodiment, a normally closed control switch 85 is connected in series with the motor 42. To provide the desired interruption in the operation of the motor 42, the switch 85, in this instance a microswitch, is provided with an operating arm 86 which is biased into the path of a pair of diametrically opposed camming surfaces 87 and 88. The camrning surfaces 87 and 88 are carried by the disk 51 and their positions thereon are related to the point at which the drive link 54 is connected to the disk so that the surface 87 engages the operating arm 86 to open the supply circuit 81 when the

plungers

18 and 19 are at the bottoms of their respective strokes while the surface 88 engages the operating arm 86 when the

plungers

18 and 19 are at the tops of their respective strokes.

To prevent fluid accumulation beyond the tip of the pipette 12, such as the formation of droplets, the carnming surfaces 87 and 88 are preferably positioned on the disk 51 so that motor interruption occurs after the platform 59 has completed its stroke in one direction and started its stroke in the other direction. In this manner, all drive force is removed from the plungers during motor interruption.

In order to provide effective interruption, the travel of the disk 51 after the motor supply circuit 81 has been opened must be limited to a distance less than the circumferential length of the camming surfaces 87 and 88.

To this end, the motor 42 is preferably provided with a brake (not shown), such as a friction brake. For the same reason, the inertia in the system is minimized as by removing unnecessary material from the disk 51, conveniently done by forming the apertures 89 therein.

To enable the operator to select the mode of operation for the diluter, the motor supply circuit 81 may be provided with a mode selector switch 90. As shown the selector switch 90 is a two position, double throw switch connected in parallel with the control switch 85. For an interrupted mode of operation, the switch 90 has one contact set, say the upper set 91, 92, from which the contactor 93 is returned to an open position by bias means (not shown), such as a spring. In this position, the contactor 93 momentarily engages the contacts 91, 92 to restart the motor 42 thereby causing the switch 85 to reclose. For a continuous mode of operation, the contactor 93 locks-in when brought into engagement with the lower contact set 94, 95 and thereby overrides the operation of the control switch 85. For convenience of operation, the contactor 93 may be carried by a lever arm 96 projecting from the diluter housing 15. For an alternative method of mode selection, a treadle switch (not shown) may also be coupled in parallel with the control switch. The provision of a treadle switch enables the operator to select interrupted or continuous operation simply by tapping the treadle for interrupted operation or by maintaining the treadle depressed for con tinuous operation.

I claim as my invention:

1. An automatic diluter for withdrawing a predetermined sample quantity from a sample supply and a predetermined dilute quantity from a diluent supply and for dispensing these quantities of sample and diluent to form a diluted sample, said diluter comprising the combination of delivery means immersible within the sample supply for withdrawing a sample and removable therefrom for discharging the sample and diluent, a first reversible fluid actuator connected to the delivery means and drivable in one direction for drawing the predetermined sample quantity into the delivery means and in the other direction for dispensing said sample quantity from the delivery means, diluent intake means immersible within the diluent supply, a second reversible fluid actuator coupled to the intake means and to the delivery means and drivable in one direction for drawing the predetermined diluent quantity into the intake means and in the other direction for dispensing said diluent quantity from the delivery means, and drive means including a single unidirectional motor coupled to drive both of the actuators alternately in said one and said other directions.

2. The automatic diluter of claim 1 wherein the first and second actuators each include a syringe of the type having a plunger movable within a body, said motor has a rotatably driven output shaft, and said drive means further includes motion converting means coupled between the output shaft of the motor and each of the syringes for converting the rotary motion of the motor output shaft into reciprocating motion of each of said plungers relative to its associated body.

3. The automatic diluter of claim 2 further including means connected to the motor for automatically interrupting motor operation upon the completion of the first actuator plunger stroke in both said one and said other directions whereby the delivery means may be removed from the sample supply without the loss of any of the sample from the delivery means and returned to the sample supply without the introduction of any air into the delivery means.

4. The automatic diluter of claim 2 wherein the motion converting means includes a drive member connected to the output shaft for rotation therewith, a guide shaft, a platform mounted for movement along the guide shaft, a drive link having one end pivotally connected to the platform and an opposite end pivotally connected to the drive member eccentrically of the motor shaft whereby the platform is reciprocated along the guide shaft with a constant stroke length, and respective lost motion connections between the platform and each of the plungers of the first and second actuators whereby the first actuator plunger is reciprocated with a stroke length corresponding to said predetermined quantity of sample and said second actuator plunger is reciprocated with a stroke length corresponding to said predetermined quantity of diluent.

5. The automatic diluter of claim 4 wherein each of lost motion connections includes adjusting means for setting the amount of motion lost thereby whereby the respective amounts of sample and diluent dispensed from the delivery means are independently selectable.

6. The automatic diluter of claim 4 wherein the drive member has a pair of diametrically opposed camming surfaces projecting therefrom, and the motor is an electric motor with a supply circuit which includes a control switch having an operating arm disposed for actuation by the camming surfaces to open the switch thereby interrupting operation of the motor, the camming surfaces bing positioned on the drive member relative to the connection of the drive link thereto so that one of the camming surfaces actuates the operating arm when the plungers of the first and second actuators are at one extreme limit of their respective reciprocations and so that the other of the camming surfaces actuates the operating arm when the plungers of the first and second actuators are at the other extreme limit of their respective reciprocations whereby the delivery means may be removed from the sample supply without the loss of any of the sample from the delivery means and returned to the sample supply without the introduction of any air into the delivery means.

7. The automatic diluter of claim 6 wherein the motor supply circuit further includes a mode selector switch connected in parallel with the control switch, the mode selector switch having at least two positions and being operable in one of the positions to momentarily close the supply circuit to restart the motor after its opera-tion has been interrupted through actuation of the operating arm by one of the camming surfaces and in the other position to override the control switch by maintaining the supply circuit closed when the operating arm is actuated by either of the camming surfaces.

8. The automatic diluter of claim 6 wherein the camming surfaces are positioned on the drive member relative to the connection of the drive link thereto so that motor operation is interrupted while the plungers of the first and second actuators are at each of the extreme limits of their respective reciprocations but after the References Cited UNITED STATES PATENTS 3/1956 Eberz 222 XR 1/ 1963 Lewis-Smith 222-135 WALTER SOBIN, Primary Examiner.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, 0.6. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,401 ,839 September 17 1968 Theodore Christie It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

\In the heading to the printed specification, lines 3 and 4 "Honeywell Inc. Minneapolis, Minn. a corporation of Delaware" should read Precision Scientific Company, Chicago, Ill.

a corporation of Illinois Signed and sealed this 10th day of February 1970.

(SEAL) Attesti.

Edward M. Fletcher, Jr.

Attesting Officer Commissioner of Patents WILLIAM E. SCHUYLER, JR.