US3707875A

US3707875A - Timing device for automatic sampling apparatus

Info

Publication number: US3707875A
Application number: US00130211A
Authority: US
Inventors: G Freeman
Original assignee: Gilford Instrument Laboratories Inc
Current assignee: Gilford Instrument Laboratories Inc
Priority date: 1971-04-01
Filing date: 1971-04-01
Publication date: 1973-01-02
Anticipated expiration: 1990-01-02

Abstract

The mechanical timing cam of an automatic sampling device is replaced by a solenoid actuated lever controlled by an electronic pulsing circuit. The lever is adapted to be moved against the actuating arm of a switch to move the arm from a first position to a second position. When the solenoid is not energized or energized with reverse polarity, the switch arm returns from its second position to its first position under the bias of a spring. In one of these positions the switch closes a circuit to a motor which in turn controls the length of time that a dip tube is in a receptacle of wash liquid. In the other position the switch closes a circuit to the motor which in turn controls the length of time that a dip tube is in a sample receptacle. Accordingly, adjusting the times that the solenoid is energized and deenergized by means of the electronic pulsing circuit, one can establish any desired ratio of sample to wash liquid or vice versa. Adjusting the cycle time of the energizing and deenergizing pulses, one can adjust the rate at which samples with intervening wash liquid are aspirated by the dip tube. A timing circuit is adjustable to achieve the desired ratios and cycle time, putting out solenoid energizing pulses.

Description

United States Patent 1 Freeman 1 Jan. 2, 1973 [54] TIMING DEVICE FOR AUTOMATIC SAMPLING APPARATUS [75] Inventor:

Gary Michael Freeman, Elyria, Ohio [73] Assignee: Gillord Instrument Laboratories Inc., Oberlin, Ohio [22] Filed: April 1, 1971 21 Appl. No: 130,211

[52] US. Cl. ..73/423 A, 317/141 R [51] Int. Cl. ..G01n 1/14, i-lOlh 47/18 [58] Field of Search...73/423 A; 335/63, 65, 67,278; 317/141; 336/65, 215

Primary Examiner-S. Clement Swisher Attorney--Silverman & Cass ,adapted to be moved against the actuating arm of a switch to move the arm from a first position to a second position. When the solenoid is not energized or energized with reverse polarity, the switch arm returns from its second position to its first position under the bias of a spring. ln one of these positions the switch closes a circuit to a motor which in turn controls the length of time that a dip tube is in a receptacle of wash liquid. ln the other position the switch closes a circuit to the motor which in turn controls the length of time that a dip tube is in a sample receptacle. 'Accordingly, adjusting the times that the solenoid is energized and de-energized by means of the electronic pulsing circuit, one can establish any desired ratio of sample to wash liquid or vice versa. Adjusting the cycle time of the energizing and de-energizing pulses, one can adjust the rate at which samples with intervening wash liquid are aspirated by the dip tube.

A timing circuit is adjustable to achieve the desired ratios and cycle time, putting out solenoid energizing pulses.

1 I2 Claims, 4 Drawing Figures [57] ABSTRACT The mechanical timing cam of an automatic sampling device is replaced by a solenoid actuated lever con- I 46 I'll! 2 b 5 (9 5 \J b2 a2 3c. 1 22 e4- 4 -40 PKTENTEDJM; Ian

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Rum-me somumo -4 8 ACT ATOR mvama Gary M. fi man I SM/erm 5' Cass llqrneys TIMING DEVICE FOR AUTOMATIC SAMPLING APPARATUS FIELD OF THE INVENTION The field of the invention is timing devices for controlling the sample to wash ratio of automatic chemistry equipment.

BACKGROUND OF THE INVENTION A type of automatic chemistry apparatus is in use today in which quantities of liquid sample are delivered to the processing portions of the apparatus through tubes, separated by bubbles of air and quantities of wash liquid. The purpose of separating the samples by wash liquid and air bubbles is to minimize contamination between samples. In order to control the quantities which are involved, sampling apparatus is used which includes a dip tube connected to the principal carrier tube and subjected to a vacuum so that whenever the dip tube is dipped in a receptacle carrying the sample it will aspirate a quantity of sample liquid, depending upon how long it is so dipped; whenever the dip tube is dipped in a receptacle containing the wash liquid it will aspirate a quantity of wash liquid, depending upon how long it is so dipped; and in the period of time that the dip tube is withdrawn from one receptacle and moves over to the other and into the other, it will aspirate air to produce a bubble in the connecting carrier tube.

Sampling apparatus of the type which is used is disclosed in US. Pat. No. 3,251,229. In that patent, the ratio of quantity of wash liquid to sample liquid was controlled by means of a double cam having depressions and raised portions the circumferential extent of the depressions and raised portions being adjustable by rotating the parts of the cam with respect to one another and then fixing them in the adjusted position. The cam was rotated in a housing by a constant speed motor. The depressions and raised portions acted on the arm of a microswitch to throw the single-pole double throw switch to either one of two positions. In one position, that is, when a depression permitted the switch arm to move toward the center of the rotating cam, the dip tube of the sampling device was in the receptacle containing the washliquid. In the second position, that is, when a raised part engaged the switch arm to move it away from the center of the rotating cam, the dip'tube of the sampling device was in the receptacle containing the liquid sample.

In this manner the circumferential length of the depressions of the cam controlled the quantity of wash liquid aspirated by the dip tube; the circumferential length of the raised parts of the cam controlled the quantity of liquid sample aspirated by the dip tube; the ratio of these lengths controlled the ratio of wash liquid to sample liquid; and the sum of these length established the time for a cycle and hence controlled the rate at which these cycles occurred.

In accurate chemical analysis, the control of the quantities and their ratios is important, even critical in most tests.

The commercial version of a sampling device of the general construction disclosed in said patent uses single replaceable cams. Each combination of the number of cycles per hour and ratio of sample to wash requires a different cam. The user must therefore have a number of cams equal to the different combinations which he will wish to use or try in the course of using the sampler for different purposes.

The changing of cams is annoying, but even more importantly, such cams are basically inaccurate because of the sharp rise of the designs needed for this type of operation and because of backlash in the system. This latter condition is aggravated at higher speeds. The purchase of many cams is expensive.

The invention eliminates the need for using cams of any kind by providing a structure fitting into the cam housing that moves the actuating arm of the microswitch in accordance with the commands of an electronic pulsing circuit that can be adjusted to a great many permutations of sample to wash ratio and cycle time. No modification or change whatsoever is made to the sampling apparatus. Adjustment of the ratio and the cycle time are accomplished merely by changing the position of the dials on the housing containing the electronic timing device.

The timing device of the invention is simple, accurate and economical and makes the sampling apparatus more flexible in use, giving the operator the opportunity for experimenting with a wide range of times and ratios without requiring the expense of purchasing a large number of cams, storing them, changing them, and keeping account of the ones used.

SUMMARY OF THE INVENTION The timing device of the invention comprises a mounting plate adapted for engagement with the cam housing of the sampling device, a solenoid mounted on the plate and having a lever coupled to its armature, the lever being pivotally mounted in a position that when the solenoid is energized the lever engages against the actuating arm of the control switch of the sampling device, and when the solenoid is de-energized, spring bias draws the lever away from the actuating arm. The solenoid receives electric signals from an electronic pulsing circuit which in turn has means for adjusting the length of each signal and the length of the time between signals. Since the release of the actuating arm of the switch controls the wash time and the depression of the actuating armof the switch controls the sample time, thetiming device of the invention can be adjusted to achieve a wide range of wash to sample ratios and a wide range of cycle times. i

The timer produces the required pulses on the basis of the charging and discharging of a condenser operating in conjunction with an operational amplifier connected as a comparator and inverter. Adjusting the resistance in the charge and discharge circuit controls the ratio of wash to sample, and adjustment of the resistance in the inverter voltage reference circuit controls the cycle time. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the timing device of the invention in association with sampling apparatus.

FIG. 2 is a bottom perspective view of the timing device of the invention.

FIG. 3 is a fragmentary sectional viewtakenalong the line 3-3 of FIG. 2 and in the indicated direction.

FIG. 4 is ablock diagram showing the electronic pulsing circuit of the timing device of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A reference character designates generally the timing device of the invention, the same adapted to be connected by means of the cable 12 to the timing circuit 14 which is described in connection with FIG. 4.

The timing device 10 includes a housing 16 formed ofa base 18 and a cover member 20, the base telescoping into the cover member thereby providing a shoulder 22. The timing device 10 is adapted to be engaged in the well 24 ofa sampler 26, the said well being cylindrical in configuration and opening to a support structure 28. The wall 30 which forms the well has a vertical slot 32 on one side thereof. A microswitch 34 leading to timing circuits of the sampler is disposed with its actuating arm 36 protruding into the well 24. A central vertically arranged shaft 38 having a pair of pins 40 adjacent the upper end thereof is disposed in the well for rotation through the medium of a motor (not shown).

The details of the construction and operation of the sampler 26 will be found in said US. Pat. No. 3,25 l ,229. As explained above, the switch 34 is a single pole, double-throw switch, operation of which controls the sample to wash ratio provided by the sampler during its operation. In the commercial version, as explained, a cam having high and low portions along its cam surface is engaged on the shaft 38 and keyed in position by means of the pins 40. The highs of the cam will engage the actuating arm 36 depressing the member 42 to throw the switch to the opposite pole represented by the position of the actuating arm 36 and the pin 42 shown in FIG. 1. Each cam is constructed for only a single sample-to-wash ratio and a single cycle time. Accordingly, whenever it is desired to have a different ratio or a different cycle time, that is, rate, a different cam must be used.

The timing device of the invention has a-block 44 secured to the bottom portion 18 thereof and a laterally protruding tongue 46 integral with the block. A solenoid 48 mounted on the base 18 has its armature 50 normally extending out of the solenoid to the left as viewed in FIG. 1, by means of a coil spring 52 between the end of the armature and the body of solenoid. An actuator 54 extends through a slot 56 and the tongue 46, being pivoted at 58 for swinging movement therein. The upper end of the actuator 54 is pinned to the armature 50 ofthe solenoid 48 at 60.

Installing the timing device 10 into the well 24 consists simply of causing the tongue 46 to engage in the slot 32 and swinging the device 10 into the well 24, so that the shoulder 22 engages on the upper wall 28 of the support structure with the shaft 38 engaged in a socket 62 formed in the bottom of the block 44.

As will be obvious from the above description, there is no modification which need be made to the commercial sampler 26.

When the solenoid 48 is energized, its armature 50 is pulled to-the right against the resistance of the spring 52 so that the lower end of the actuator 54 engages the actuating arm 36 causing same to move against the member 42. When the solenoid is de-energized, the actuator 54 takes the position shown in FIG. 1.

Attention is now invited to the block diagram of FIG. 4, which constitutes the timing circuit.

The timing circuit 14 has an operational amplifier connected in an inverting mode and thus comprising a comparator and inverter. The noninverting terminal 72 is connected through a condenser C to a negative source of DC voltage indicated at 74. The

reference characters

76 and 78 comprise transistors suitably connected to provide, in effect, positive and negative direct current sources operating with switching functions. Resistors R76 and R78 connect the two

elements

76 and 78 together, the center point between the resistors being connected by way of the line 80 to the output terminal 82 of the comparator 70, this terminal 82 also being connected to the

output elements

84 and 86. The switch and positive current source element 76 is connected through the switch SW1 to any one of the resistors R1, R2 Rn to the source of positive DC voltage 88. The switch and negative current source element 78 is connected through the switch SW2 to any one of the resistors R1", R2 Rn" to a source of negative DC voltage 90. The switches SW1 and SW2 are ganged as indicated by the broken line 92. The terminal 82 is also connected through an inverter voltage reference 94, and adjustable resistor Radj to ground through the switch SW3 which connects the terminal 96 to ground through any one of the resistors Rl', R2, Rn' depending on the position of the arm of the switch. From the terminal 96 there is a connection by way of the line 98 to the inverting terminal 100 of the comparator 70. Outputs of the

respective elements

84 and 86 are connected to the switch SW4, this comprising a double-pole, double-throw switch capable of reversing the connections from the

elements

84 and 86 to the output cable 12. Each line ofthe output 12 has a

lamp

102 and 104 respectively, these being also connected to a positive voltage source.

The element 76 comprises a PNP transistor and the element 78 comprise an NPN transistor. The collectors of the transistors are connected together through the line 106. The bases are connected together through the resistors R76 and R78. The emitter of the PNP transistor is connected through a single primed resistor to voltage source 88 and acts as a positive current source. The emitter of the NPN transistor is connected through a double primed resistor to voltage source 90 and acts as a negative current source.

The

output elements

84 and 86 comprise oppositely poled transistors for handling the reversing of the polarity of the point 82 to the cable leads 12 so that the ratio controlled by the chosen resistors results in opposite polarity energizing ofthe solenoid 48.

In operation, when the circuit 14 is energized the condenser C charges through positive current source 76, the rate being controlled by the value of whichever resistor R1 to Rn is in circuit. The condenser C charges at a linear rate due to the choice of circuit components. At the same time, the inverting terminal of the comparator 70 is positive but its output at the terminal 82 is negative. The output of the inverter voltage reference 94 is positive so that, depending upon the position of the switch SW3, a voltage is applied to the inverting terminal 100 which is also positive.

It will be noted that the condenser C is connected to some negative voltage 74 to give the necessary switching characteristic.

The noninverting terminal 72 commences to rise in voltage until it exceeds the positive voltage on the inverting terminal 100. At that point, the comparator changes its output from negative to positive so that after this conversion, the terminal 82 becomes negative. Again, the inverter voltage reference 94 assumes a new negative voltage which is determined by the position of the switch SW3. In both cases, the exact voltage can be adjusted by the resistor Radj.

When the output of the comparator switched from negative to positive, this condition was applied to the

elements

76 and 78 through the line 80. At that point, the upper switch and current source 76 cuts off and the lower switch and current source 78 turns on. V

The condenser C now starts to discharge on a linear characteristic through the current source 78 which is negative and the particular resistor R1" to Rn" chosen by the switch SW2. When the voltage on the condenser C reaches a negative value below the negative voltage of the inverting input 100, again the output of the comparator 70 suddenly changes from positive to negative and the process continues in this manner.

Elements

84 and 86 are merely transistors producing outputs of opposite polarity which are readily switched by the switch 4. The

lamps

102 and 104 will go on each time the wash or sample portion of the output characteristic is occurring, respectively. Adjustment of the switch SW3 controls the rate or cycle time, and adjustment of the switches SW1 and SW2 controls the ratio of wash-to-sample or sample-to-wash. The same proportions of resistors are used but by means of the inverting switch SW4 the ratio is reversed. In other words, if a given setting produces a sample-to-wash ratio of l to 6, throwing the switch SW4 to its other position will produce a sample-to-wash ratio of6 to 1.

It will be obvious that other timing circuits could be used to achieve the necessary output signals. in the particular circuit used, the signal on the noninverting terminal 72 is in the form of a sawtooth wave with the positive and negative slopes being controlled by the position of the switches SW1 and SW2. The output at 82 is a rectangular wave jumping between the positive and negative voltages to cause energization and deenergization of the solenoid 48.

What is desired to be secured by Letters Patent of the United States is:

l. A timing device adapted to be associated with an automatic sampling apparatus, said apparatus comprising a support structure having an upper wall, a well in said apparatus opening to said upper wall, a-central post in said well, a switch mounted to said support structure and presenting an actuating arm laterally to said well, depressing and releasing of said actuating arm adapted to control the aspiration of two respective liquids by the sampling apparatus, said timing device comprising:

A. a housing adapted to be mounted on said wall and having a portion thereof engaging in said well;

B. a central member secured to said portion and having a socket and said post adapted to enter said socket for centering the housing,

C. said portion having positioning means adapted to cooperate with said well to establish a predetermined circumferential relationship between the housing and the actuating arm,

D. an electrical solenoid in the housing and having an armature adapted to reciprocate between two positions when the solenoid is energized and deenergized, E. an actuator member coupled with said armature,

extending downward from said portion to a position adapted to be in alignment with said actuating arm when the housing is installed in said well in said predetermined circumferential relationship, and i means for continuously energizing and de-energizing said solenoid in a predetermined timed relation whereby to cause said actuator member to depress and release said actuating arm in repetitive cycles. 2. The timing device as claimed in claim 1 in which the armature is disposed in a substantially horizontal aspect, said actuator member has its upper end connected to said armature and is pivotally connected to said portion with its lower end free and adapted to extend into said well.

3. The timing device as claimed in claim 1 in which the positioning means comprises a laterally protruding tongue adapted to engage within a lateral slot provided in said well.

4. The timing device as claimed in claim 1 in which the housing comprises a base and cover member telescopically engaged and providing a shoulder, the shoulder adapted to engage the upper wall and the part of the base below said shoulder comprising said portion.

5. The timing device as claimed in claim 4 in which said solenoid is mounted on said base and encased by said cover member.

6. The timing device as claimed in claim 4 in which said solenoid is mounted on said base, and said base has a slot, the actuator arm being pivotally engaged in said slot and having its upper part within the housing pinned to said armature and its lower part depending from said slot and providing a free end adapted to be so aligned with said actuating member.

7. The timing device as claimed in claim 1 in which said last-mentioned means comprise a timing circuit having means for adjusting the ratio of energization to de-energization of the solenoid to any of a plurality of different ratios, and means for adjusting the time of one cycle of energization and de-energization to any of a plurality of different times.

8. The structure as claimed in claim 7 in which there are provided capacitance-resistance charge and discharge circuits alternately activated to control said ratio, and the means for adjusting the ratio include means for changing the resistance of the charge and discharge circuits.

9. The structure as claimed in claim 8 in which the timing circuit includes means for automatically switching the output of said circuit from energization signals to de-energization signals simultaneously with said alternate activation.

10. The structure as claimed in claim 9 in which said automatic switching means include an operational amplifier connected in inverting configuration.

11. In a device of the character described, and in combination with a solenoid-operated actuator arm adapted to control the ratio of wash-to-sample time and rate of an automatic sampling apparatus, an electronic are produced including an operational amplifier connected in inverting configuration, the inverting terminal having a variable voltage reference and the capacitance-resistance circuits being connected to the noninverting terminal.

12. The device as claimed in claim 11 in which the capacitance-resistance circuits include alternately operating electronic switches, the output of the operational amplifier being fed back to said electronic switches for alternately operating the same.

Claims

1. A timing device adapted to be associated with an automatic sampling apparatus, said apparatus comprising a support structure having an upper wall, a well in said apparatus opening to said upper wall, a central post in said well, a switch mounted to said support structure and presenting an actuating arm laterally to said well, depressing and releasing of said actuating arm adapted to control the aspiration of two respective liquids by the sampling apparatus, said timing device comprising: A. a housing adapted to be mounted on said wall and having a portion thereof engaging in said well, B. a central member secured to said portion and having a socket and said post adapted to enter said socket for centering the housing, C. said portion having positioning means adapted to cooperate with said well to establish a predetermined circumferential relationship between the housing and the actuating arm, D. an electrical solenoid in the housing and having an armature adapted to reciprocate between two positions when the solenoid is energized and de-energized, E. an actuator member coupled with said armature, extending downward from said portion to a position adapted to be in alignment with said actuating arm when the housing is installed in said well in said predetermined circumferential relationship, and F. means for continuously energizing and de-energizing said solenoid in a predetermined timed relation whereby to cause said actuator member to depress and release said actuating arm in repetitive cycles.

2. The timing device as claimed in claim 1 in which the armature is disposed in a substantially horizontal aspect, said actuator member has its upper end connected to said armature and is pivotally connected to said portion with its lower end free and adapted to extend into said well.

11. In a device of the character described, and in combination with a solenoid-operated actuator arm adapted to control the ratio of wash-to-sample time and rate of an automatic sampling apparatus, an electronic timing circuit adapted to provide energizing and de-energizing signals in a predetermined timed relation to move said actuator arm in repetitive cycles, said timing circuit including a pair of capacitance-resistance circuits adapted alternately to charge and discharge a capacitor, means for activating the circuits alternately at a predetermined rate and providing an output comprising said energizing signal while one circuit is activated and a de-energizing signal while the other circuit is activated and adjustable means for varying the rate at which the energizing and de-energizing signals are produced including an operational amplifier connected in inverting configuration, the inverting terminal having a variable voltage reference and the capacitance-resistance circuits being connected to the noninverting terminal.