Vital relay operating circuit

Claim 2

Fail safe relay actuating means comprising in combination: (a) an a.c. signal source modulated at a predetermined rate to signals of first and second frequencies; (b) discriminator means coupled to said signal source rectifying said signals of said first and second frequencies for producing an output potential, between a pair of terminals, which reverses polarity at said predetermined rate in response to the modulation of said a.c. signal source; and (c) first and second polarity responsive means coupled in parallel between said pair of terminals for producing relay control signals in response to said polarity reversals.

Claim 3

The combination as set forth in claim 1 and including a voltage doubling circuit, coupled between said polarity responsive means and the relay for energizing the relay in response to said relay control signals.

Claim 4

The combination as set forth in claim 2, wherein the coupling between said polarity responsive means and the voltage doubling circuit comprises photoelectric coupling.

Claim 5

The combination as set forth in claim 3, wherein said voltage doubling circuit includes switching means.

Claim 6

The combination as set forth in claim 4, wherein said switching means comprises light responsive resistor means.

Claim 7

The combination as set forth in claim 1, wherein said discriminator means comprises rectification means for producing said reversing polarity output potential only in response to the alternate domination of said first and second frequencies.

Claim 8

The combination as set forth in claim 6 and including a voltage multiplying circuit, coupled between said polarity responsive means and the relay, for producing a relay actuating signal in response to said relay control signals.

Claim 9

The combination as set forth in claim 7, wherein said voltage multiplying circuit includes impedance means whose impedance is independent of the polarity of said relay actuating signal.

Claim 10

A circuit for actuating a vital relay in response to an a.c. signal being alternately modulated to signals of first and second frequencies and comprising in combination: (a) first and second rectification means responsive to said first and second frequencies for producing first and second d.c. output potentials, respectively; (b) said first and second d.c. output potentials coupled in series opposition across a terminal pair for producing an output potential having the polarity of the dominant one of said first and second d.c. output potentials; (c) first and second polarity responsive control means bridged in parallel across said terminal pair for producing first and second signals and second and first signals, respectively, when the potential across said terminal pair is of the polarity of said first and second d.c. output potentials, respectively; (d) first and second switching means coupled to said first and second polarity responsive control means, respectively, and responsive to said first signals for rendering said first and second switching means conducting; and responsive to said second signals for rendering said first and second switching means relatively nonconducting; and wherein (e) said first and second switching means control the flow of current to the vital relay.

Claim 11

A circuit for actuating a vital relay in response to an a.c. signal being alternately modulated to signals of first and second frequencies and comprising in combination: (a) first and second rectification means responsive to said first and second frequencies for producing first and second d.c. output potentials, respectively; (b) said first and second d.c. output potentials coupled in series opposition across a terminal pair for producing an output potential having the polarity of the dominant one of said first and second d.c. output potentials; (c) first and second polarity responsive control means bridged in parallel across said terminal pair for producing first and second signals and second and first signals, respectively, when the potential across said terminal pair is of the polarity of said first and second d.c. output potentials, respectively; (d) first and second switching means coupled to said first and second polarity responsive control means, respectively, and responsive to said first signals for rendering said first and second switching means conducting; and responsive to said second signals for rendering said first and second switching means relatively nonconducting; and wherein (e) said first and second switching means control the flow of current to the vital relay.

Claim 12

The combination as set forth in claim 9, wherein said first and second switching means comprise light responsive resistor means.

Claim 13

The combination as set forth in claim 10, wherein said first and second polarity responsive control means include a source for emitting light only in response to the polarity across said terminal pair being said one polarity and said reverse polarity, respectively.

Claim 14

The combination as set forth in claim 9, wherein the only coupling between the combination of said first and second switching means and the vital relay, with said first and second control means, is photoelectric.

Claim 15

The combination as set forth in claim 9 and including means intercoupling said first and second switching means for interrupting the flow of operating current to the vital relay in response to the cessation of the alternate production of said first and second output potentials.

Claim 16

The combination as set forth in claim 13, wherein said intercoupling means includes a capacitor.

Claim 17

The combination as set forth in claim 14, wherein said first and second switching means and said intercoupling means comprises a voltage doubler.

Claim 18

The combination as set forth in claim 9, wherein said first and second switching means comprises impedance means whose impedance is independent of the polarity of the potential thereacross.

Claim 19

The combination as set forth in claim 16, wherein said first and second switching means comprises part of a voltage multiplying circuit coupled between said polarity responsive means and the relay, for producing a relay actuating signal in response to said control signals.

Claim 20

The combination as set forth in claim 17, wherein said voltage multiplying circuit produces said relay actuating signal only in response to the alternate receipt of said first and second signals by said first and second switching means.