US 4,535,959 AGranted

Vital solid state relay for railroad alternating current track circuits

AssigneeAmerican Standard Inc.

InventorHeinz Gilcher

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Abstract

This vital solid state relay incorporates only passive elements and is intended for use as a replacement for a two element AC track relay in AC track circuits. The local input signal is applied to a transformer whose secondary output, across a Zener diode, is a pulsed, square wave DC with regulated peak. The track input is applied through a noise rejection filter, tuned to track circuit frequency, to a coupling transformer. A series loop registry circuit includes the secondary of each transformer, a DC relay, and a varistor element. The sum of the transformer output signals, due to the Zener diode rectification, has a DC component. When local and track signals are both present and substantially in phase, the varistor switches to its high current condition to pick up the DC relay to indicate an unoccupied track section. Absence of the track input, out of phase conditions, or unmatched frequencies retains the varistor in its low current state and the DC relay releases to register an occupied section.

Claims7

Dependent claims

A vital solid state relay arrangement comprising,

(a) first input means coupled for receiving a first alternating current signal from a first source having a selected signal frequency,
(b) a second input means coupled for at times receiving a second alternating current signal from a second source, said second signal having said selected frequency and a predetermined phase relationship with said first signal,
(c) a varistor element,
(d) a register means normally occupying a first position and operable to a second position,
(e) a register network coupling said first and second input means, said varistor element, and said register means for operating said register means to its second position to register the presence of said second signal only when both signals are present and within said predetermind phase relationship,
(f) a first transformer coupled to said first source for producing a selected level first signal at its secondary winding output, and
(g) a Zener diode having a preselected regulating level connected across said first transformer secondary winding, and
(h) the multiple path circuit through said secondary winding and said diode coupled for supplying rectified square wave pulses with peaks at said preselected regulating level into said register network.

5 more elements

A track circuit arrangement for an insulated railroad track section, with propulsion power currents having varying characteristics flowing in the rails, comprising,

(a) a source of alternating current energy of preselected frequency coupled to said rails at one end of said section,
(b) a register relay normally occupying a first position and operable to a second position to indicate said section unoccupied by a train,
(c) a control circuit network, including a varistor switch element, coupled for energizing said register relay,
(d) a first input means coupled to said source for supplying a pulsed direct current square wave signal with a regulated peak voltage to said control circuit network,
(e) a second input means coupled to said rails at the other end of said section for supplying an alternating current signal from said source to said control circuit network when the section is unoccupied by a train,
(f) said control circuit network responsive to both input signals for energizing said register relay to operate to its second position only when both signals are present and in phase.

3 more elements

Dependencies are inferred from the claim text.