Radio-controlled machine power cut-off

• US 4,057,805 A
• Filed: 03/30/1976
• Issued: 11/08/1977
• Est. Priority Date: 03/30/1976
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Dowling, Donald Hugh
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US05/672,030
• Time in Patent Office: 588 Days
• Field of Search: 343/225, 340/147 MT, 340/224, 340/119, 340/267 R, 340/279, 192/131 R, 192/129 A, 318/16, 325/37, 325/51, 325/118
• US Class Current: 340/687
• CPC Class Codes: F16P 3/147 using electro-magnetic technology, e.g. tags or radar
• CPC Class Codes: G08B 21/187 Machine fault alarms
• CPC Class Codes: G08C 2201/63 Redundant transmissions
• CPC Class Codes: H04B 1/0343 to be carried on the body
• CPC Class Codes: H04B 1/04 Circuits

Abstract

A pair of battery-powered radio transmitters are individually worn on the wrists of a machine operator, and two radio receivers are tuned to receive the signals broadcast by the radio transmitters, the first radio receiver being a proximity-sensitive device switching off the driving power to the machine whenever either radio transmitter comes within a preselected safe distance limit from the work-accomplishing region of the machine whereas the second radio receiver is a radio transmitter operating state-verifying device switching off the driving power to the machine whenever either or both of the radio transmitters fails to transmit its characteristic broadcast signal.

Claims

1. A radio-controlled machine power safety cut-off comprising

a pair of battery-powered radio transmitters adapted for individual wear on the wrists of the machine operator,

a first radio receiver means having its antenna disposed at a danger zone of said machine responsive to the predetermined magnitude of a broadcast signal emitted by either or both of said radio transmitters signalling intrusion of said radio transmitters closer than a preselected safe distance, said first radio receiver being provided with associated switching means cutting off the operating power of said machine, upon occurrence of said intrusion, and

a second radio receiver means having its antenna disposed adjacent said machine responsive to the broadcast signals of said pair of radio transmitters, said second radio receiver being provided with associated switching means cutting off the operating power to said machine whenever either or both of said radio transmitters fails to emit said broadcast signals.

2. A radio-controlled machine safety power cut-off according to claim 1 wherein at least said first radio receiver means is provided with gain control means.

3. A radio-controlled machine safety power cut-off according to claim 1 wherein said radio receiver means are provided with means indicating the closed circuit and open circuit conditions of said associated switching means effecting said cutting off of the operating power of said machine.

4. A radio-controlled machine safety power cut-off according to claim 1 wherein said pair of radio transmitters each broadcasts a different preselected radio frequency signal, the difference in frequency between which constitutes the distinctive operating frequency signal for said second radio receiver means.

5. A radio-controlled machine safety power cut-off according to claim 4 wherein said pair of radio transmitters comprise quartz crystal-stablized oscillators.

6. A radio-controlled machine safety power cut-off according to claim 5 wherein said first and said second radio receiver means are each provided with its own oscillator and mixer generating, upon receipt of broadcast signals from said radio transmitters, a preselected heterodyne frequency signal determining said cut-off of operating power to said machine.