US 4,756,494 AGranted

Vital switch control circuit

AssigneeAmerican Standard Inc.

InventorsRobert A. Kondratenko, Jack Cunningham

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Abstract

A vital switch control circuit for a railroad switch machine includes a permanent magnet motor which is immune to stray or induced a.c. currents, and which is operable to either of two directions depending on the polarity of energy applied thereto. Switch-normal and switch-reverse contacts of a switch request relay logic circuit establish alternate positive and negative-current paths which are connected over a minimum number of line wires to a motor control contact arrangement and to a mechanically-interlocked, dual-coil, reversing contactor. The reversing contact is operable only above a specific d.c. voltage, therefore providing low-level d.c. immunity in case of grounding or cross-over conditions arising in the line wires. A reverse motor contact and a normal motor contact are used to alternately establish negative-current paths to the permanent magnet motor. Other reverse and normal motor contacts allow energization of the coils of the reversing contactor which have associated normal and reverse contacts, and over which the positive-current paths are established to the permanent magnet motor.

A vital switch control circuit for controlling the movement of a railroad switch machine to one of mutually exclusive normal- and reverse-switch positions, said vital switch control circuit comprising:

(a) a first positive-current path having disposed therein at least one normal contact which, when actuated during a request to such normal-switch position, closes said first positive-current path;
(b) a first negative-current path having disposed therein another at least one normal contact which, when actuated during such normal-switch position request, closes said first negative-current path;
(c) a second positive-current path having disposed therein at least one reverse contact which, when actuated during a request to such reverse-switch position, closes said second positive-current path;
(d) a second negative-current path having disposed therein another at least one reverse contact which, when actuated during such reverse-switch position request, closes said second negative-current path;
(e) said first positive- and negative-current paths being closed at times mutually exclusive of when said second positive- and negative-current paths are closed;
(f) motor control means connected to said first and second positive-current paths and to said first and second negative-current paths for closing an electrical connection through at least one normal motor contact when the switch machine is in such normal position, and for closing another electrical connection through at least one reverse motor contact when the switch machine is in such reverse position;
(g) a permanent magnet motor connected to at least one of said at least one normal motor contact and to at least one of said at least one reverse motor contact such that, one of said first and second negative-current paths is connected to a first motor lead to said permanent magnet motor;
and
(h) interlocking contactor means disposed between said motor control means and said permanent magnet motor for sensing the polarity of the energy applied to said first and second positive current paths and connecting respectively one of said first and second positive current paths to a second motor lead of said permanent magnet motor.

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Abstract

Claims19