# US 5,347,420 A · Electrically operated control device and system for an appliance and method of operating the same

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- Number: US 5,347,420 A
- Document ID: US5347420A
- Status: Granted
- Kind: A
- Application number: 08/071,075
- Filed: 1993-06-02
- Granted: 1994-09-13
- Earliest claimed: 1986-05-30
- Assignees: Robertshaw Controls Company
- Inventors: Daniel L. Fowler
- Web page: https://patentgrep.com/patent/US5347420A

## CPC

- H05B 6/68: for monitoring or control
- H01H 1/605: {Cleaning of contact-making surfaces by relatively high voltage pulses}
- H01H 9/56: for ensuring operation of the switch at a predetermined point in the AC cycle
- H01H 47/043: {making use of an energy accumulator (for bistable relays H01H47/226)}
- H05B 6/666: {Safety circuits (emergency protective circuits in general H02H)}
- H01H 2009/566: {with self learning, e.g. measured delay is used in later actuations}
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00)

## Abstract

An electrically operated control device and system for an appliance and method of operating the same are provided, the system comprising a power source of alternating electrical current that has a repeating voltage wave cycle and a repeating current wave cycle, a load for using the electrical current to provide an output of the load for the appliance, a relay having normally open contacts and a coil for closing the contacts only when the coil is energized, an electrical circuit for interconnecting the power source to the load through the contacts only when the contacts are closed, and a control unit for causing the coil to close the contacts substantially at a certain point on the voltage wave cycle each time the relay coil closes the contacts from the open condition thereof whereby the current flow through the contacts at each closing thereof is at substantially a desired level thereof.

## Claims

### Claim 1

In a method of operating a control system for an appliance, said system comprising a power source of alternating electrical current that has a repeating voltage wave cycle and a repeating current wave cycle, load means for using said electrical current to provide an output of said load means for said appliance, relay means having normally open contact means and coil means for closing said contact means only when said coil means is energized, electrical circuit means for interconnecting said power source to said load means only through said contact means to provide said output and only when said contact means are closed by said coil means, said coil means having a normal voltage rating that will cause said contact means to close in a certain time period after said normal voltage is initially applied across said coil means, and control means for causing said coil means to close said contact means, the improvement comprising the step of operating said coil means initially with a high voltage that is substantially larger than said normal voltage across said coil means to close said contact means each time said relay coil means closes said contact means from said open condition thereof and then reducing the voltage across said coil means to substantially the normal voltage therefor or a voltage lower than said normal voltage for holding said contact means in said closed condition thereof, the step of operating said coil means comprising the step of interconnecting said coil means across a positive or negative going D.C. signal with a capacitor and a resistance that are disposed in parallel between one side of said coil means and one side of said D.C. signal with said D.C. signal having said high voltage.

### Claim 2 (depends on 1)

A method as set forth in claim 1 wherein said normal voltage of said coil means is approximately 18 volts and said D.C. signal is approximately 27 volts.

### Claim 3 (depends on 1)

A method as set forth in claim 1 wherein said D.C. signal will create a certain voltage across said resistance when said D.C. signal has fully charged said capacitor so that said normal voltage or said lower voltage will exist across said coil means.

### Claim 4 (depends on 3)

A method as set forth in claim 3 wherein said normal voltage or said lower voltage substantially equals the difference between the voltage of said D.C. signal and said certain voltage.