FAIL-SAFE MONITORING APPARATUS

• US 3,831,161 A
• Filed: 06/08/1972
• Issued: 08/20/1974
• Est. Priority Date: 06/08/1972
• Status: Expired due to Term

• Current Assignee: Robert S. Enabnit
• Original Assignee: Robert S. Enabnit
• Inventors: Enabnit, Robert S.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/260,935
• Time in Patent Office: 803 Days
• Field of Search: 340/259,58 73/146.5 226/11 331/65 330/1R
• US Class Current: 340/507
• CPC Class Codes: B60C 23/043 using transformer type signal transducers, e.g. rotary transformers
• CPC Class Codes: B65G 43/02 detecting dangerous physical condition of load carriers, e.g. for interrupting the drive in the event of overheating
• CPC Class Codes: G07C 3/005 during manufacturing process

Abstract

An amplifier oscillates when a moving close-circuited inductor increases the coupling between a pair of input and output inductors. The oscillatory bursts, due to the periodic and proximate passage of the moving inductor, are integrated and averaged to provide a voltage level sufficient to maintain a warning circuit in a '"'"''"'"''"'"''"'"'safe operating'"'"''"'"''"'"''"'"' condition indication. The absence or open-circuiting of the moving inductor drops the voltage to a level such that the warning circuit provides an '"'"''"'"''"'"''"'"'abnormal operating'"'"''"'"''"'"''"'"' condition indication.

Claims

1. Apparatus for monitoring the condition of a first member proximate and in relative motion to a second member comprising:

A. detector circuit means on the second member comprising an amplifier having input and output inductors with insufficient mutual coupling to provide positive feedback in the amplifier, said circuit means providing an output signal in response to coupling of the amplifier input and output inductors;

B. sensor circuit means on the first member to monitor the condition of the first member and to provide periodic coupling between the amplifier inductors when close-circuited in response to the monitored condition; and

C. indicator circuit means responsive to and accepting the output signal of the detector circuit means to provide an indication representative of the condition monitored by the sensor circuit means.

2. The apparatus of claim 1 wherein the sensor circuit means comprises a normally closed-circuited inductor that provides coupling between the amplifier input and output inductors sufficient to cause the amplifier to oscillate when said inductor is in proximate position to the amplifier inductors, said sensor circuit means adapted to be open-circuited upon the occurrence of an abnormal condition.

3. The apparatus of claim 2 wherein the detector circuit means further comprises:

a. means to demodulate the amplifier output signal to provide a pulse signal; and

b. means to sum the pulses to provide a first D.C. voltage to the indicator circuit means input representative of a close-circuited sensor circuit and to provide a second D.C. voltage representative of an open-circuited sensor circuit.

4. The apparatus of claim 3 wherein the indicator circuit means is responsive to the D.C. voltage at its input to provide a normal condition indication when the voltage is above a predetermined level and to provide an abnormal condition indication when the voltage is below the predetermined level.

5. The apparatus of claim 1 wherein the sensor circuit means comprises a normally open-circuited inductor adapted to be close-circuited upon the occurrence of an abnormal condition, said means providing coupling between the amplifier inductors sufficient to cause the amplifier to oscillate when close-circuited and in proximate position to said amplifier inductors.

6. The apparatus to claim 5 wherein the detector circuit means further comprises:

a. means to demodulate the amplifier output signal to provide a pulse signal; and

b. means to sum the pulses to provide a first D.C. voltage to the indicator circuit means input representative of an open-circuited sensor circuit and to provide a second D.C. voltage representative of a close-circuited sensor circuit.

7. The apparatus of claim 6 wherein the indicator circuit means is responsive to the D.C. voltage at its input to provide a normal condition indication when the voltage is below a predetermined level and to provide an abnormal condition indication when the voltage is above the predetermined level.

8. Apparatus for monitoring a condition on a first member proximate and in relative motion with respect to a second member comprising:

A. an indicator circuit on the second member adapted to indicate normal and abnormal condition occurrences in response to the voltage level at its input;

B. a close-circuited inductor on the first member adapted to be open-circuited upon the occurrence of an abnormal condition; and

C. a detector circuit on the second member coupled to proviDe an input signal to the indicator circuit, said detector circuit comprising;

a. an amplifier having uncoupled input and output inductors in proximate relative position to the close-circuited inductor on the first member, said amplifier adapted to provide an oscillatory output signal when the input and output inductors are coupled by the proximate position of the inductor on the first member;

b. means to demodulate the oscillatory output of the amplifier to provide a pulse for each amplifier output; and

c. means to sum the pulses from the demodulating means to provide a first signal voltage level to the indicator circuit in response to a close-circuited inductor on the first member and a second signal voltage level in response to an open-circuited inductor on the first member.

9. Apparatus according to claim 8 wherein the first member is a vehicle wheel and a pressure switch is adapted to maintain the inductor circuit closed under normal tire pressure.

10. Apparatus according to claim 8 wherein the first member is a conveyor belt, and said close-circuited inductor is embedded in the belt along its width and transverse to the direction of movement of the belt and adapted to being open-circuited upon a longitudinal break in the belt.

11. Apparatus according to claim 8, wherein the first member is a conveyor belt and a plurality of said close-circuited inductors are positioned at regular intervals along the length of the belt and embedded in the belt, along its width and transverse to the direction of movement of the belt to provide periodic coupling of the amplifier input and output inductors, said means to sum the pulses having a time constant longer than the period between two successive embedded inductors but shorter than the period to the next successive inductor such that open-circuiting of any one of the plurality of embedded inductors effects termination of the relative motion between the two members.