05340182 is referenced by 88 patents and cites 10 patents.

An elevator for supporting a string of pipe in a well rig is actuable between a closed condition for gripping of the pipe and an open condition, and includes a safety device for preventing opening of the elevator when a string of pipe is positioned in and supported by the elevator, to thus prevent accidental dropping of the string into a well. The elevator may be opened and closed by air pressure, with the safety device preferably including a sensing element positioned to respond to the presence of a well pipe in the elevator at a location to be supported thereby, and a valve actuable by the sensing element to control the delivery of pressure fluid to the elevator.

Title
Safety elevator
Application Number
7/941233
Publication Number
5340182
Application Date
September 4, 1992
Publication Date
August 23, 1994
Inventor
David B Mason
Eindhoven
NL
Johannes W H van Rijzingen
Oosterhout
NL
Cornelis L Busink
Breda
NL
Agent
William P Green
Assignee
Varco International
CA, US
IPC
E21B 19/06
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