# US 3,970,942 A · Anti-hunting system for valve operator circuit

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- Number: US 3,970,942 A
- Document ID: US3970942A
- Status: Granted
- Kind: A
- Application number: 05/537,994
- Filed: 1975-01-02
- Granted: 1976-07-20
- Earliest claimed: 1974-04-22
- Assignees: Sun Oil Company of Pennsylvania
- Inventors: Robert Mayer
- Web page: https://patentgrep.com/patent/US3970942A

## CPC

- B67D 7/744: {involving digital counting}
- G05D 11/132: {by controlling the flow of the individual components (G05D11/133 takes precedence)}
- G05B 2219/36012: Percentage keys, input percentage values
- G05B 2219/41122: Mechanical vibrations in servo, antihunt also safety, stray pulses, jitter
- G05B 2219/41247: Servo lock
- G05B 2219/41326: Step motor
- B67D: DISPENSING, DELIVERING OR TRANSFERRING LIQUIDS, NOT OTHERWISE PROVIDED FOR (cleaning pipes or tubes or systems of pipes or tubes B08B9/02; emptying or filling of bottles, jars, cans, casks, barrels, or similar containers, not otherwise provided for B67C; water supply E03; pipe systems F17D; domestic hot-water supply systems F24D; measuring volume, volume flow, mass flow or liquid level, metering by volume G01F; coin-freed or like apparatus G07F)
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

An anti-hunting system for use with a valve operator circuit which compares two trains of pulses to place a valve in the correct position. The anti-hunting system includes a J-K flip-flop circuit receiving a clock pulse train having an absolute time relationship with the input pulse trains. Also included in the valve operator circuit is a system having a shift register for controlling the energizing of the leads to a stepping motor controlling the valve position.

## Claims

### Claim 1

A pulse rate comparison system for comparing two input pulse trains to control a stepping motor and having means for preventing hunting action, and comprising:
a. a J-K flip-flop circuit, said J-K flip-flop comprising,
i. a flip-flop circuit with a set terminal, a reset terminal and a clock terminal as input terminals and Q and Q output terminals,
ii. a first AND gate having one input terminal designated as the J input terminal and a second input terminal connected to the Q output terminal, the output of said first AND gate being connected to the set input terminal of the flip-flop circuit, and
iii. a second AND gate having one input terminal designated as the K input terminal and a second input terminal connected to the Q output terminal, the output of said second AND gate being connected to the reset input terminal of the flip-flop circuit;
b. means for applying one of two input pulse trains to be compared to the J input terminal of the J-K flip-flop circuit;
c. means for applying the remaining or second pulse train to the K input terminal of the J-K flip-flop circuit;
d. means for combining the two input pulse trains to form a third pulse train having an absolute time relationship with the input pulse trains;
e. means for applying the third pulse train to the clock pulse terminal of the J-K flip-flop circuit; and
f. means, responsive to the state of the input and output terminals of the J-K flip-flop circuit, for controlling the energizing of the stepping motor so that the motor is moved into the correct position without hunting, whereby a control pulse for energizing the stepping motor is produced only when a pulse is received by either the J or K input terminals of the J-K flip-flop circuit which does not change the state of the output of the J-K flip-flop circuit.

### Claim 2 (depends on 1)

The pulse rate comparison system recited in claim 1, wherein the means for combining the two input pulse trains includes a NAND gate.

### Claim 3 (depends on 1)

The pulse rate comparison system recited in claim 1, wherein the means for controlling the energizing of the stepping motor comprises:
a. means for summing the pulse trains from the J and K input terminals and Q and Q output terminals to produce a sum output pulse train having a pulse only when a pulse occurs on one of the input terminals of the J-K flip-flop circuit which does not change the state of the output of the J-K flip-flop circuit; and
b. means, responsive to the sum output pulse train and the state of one of the output terminals of the J-K flip-flop circuit, for energizing the appropriate electrical leads of the stepping motor so that the motor is stepped into its correct position.

### Claim 4 (depends on 3)

The pulse rate comparison system recited in claim 3, wherein the summing means comprises:
a. a first NAND gate having one input terminal receiving the input pulse train applied to the J input terminal and a second input terminal receiving the pulse train experienced at the Q terminal of the J-K flip-flop circuit;
b. a second NAND gate having one input terminal receiving the input pulse train applied to the K input terminal and a second input terminal receiving the pulse train experienced at the Q terminal of the J-K flip-flop circuit; and
c. a third NAND gate having one input terminal receiving the output pulse train of the first NAND gate and a second input terminal receiving the output pulse train of the second NAND gate.

### Claim 5 (depends on 3)

The pulse rate comparison system recited in claim 3, wherein the means for energizing the stepping motor electrical leads comprises a shift register.

### Claim 6 (depends on 5)

The pulse rate comparison system recited in claim 5, wherein the shift register has a clock pulse terminal which receives the sum output pulse train and a parallel enable terminal connected to one of the J-K flip-flop circuit outputs, and means for interconnecting the stages of the shift register and the leads of the stepping motor so that upon receiving pulse trains with predetermined waveforms at the clock pulse terminal and the parallel enable terminal, the leads are energized in a predetermined manner, thereby causing the stepping motor to move a predetermined amount in a predetermined direction.