04262693 is referenced by 99 patents and cites 6 patents.

A valve adapted for installation at the lower end of a drilling kelly for closing the bore of the kelly when adding a section of drill pipe so that the mud content of the kelly is not discharged onto the derrick floor; the valve also being adapted with minimum change in parts, to be inverted and installed at the upper end of the kelly to serve as a safety valve, providing blow out protection.

Title
Kelly valve
Application Number
6/53854
Publication Number
4262693
Application Date
July 2, 1979
Publication Date
April 21, 1981
Inventor
Bernhardt F Giebeler
San Bernardino
CA, US
Agent
Lyon & Lyon
Assignee
Bernhardt & Frederick Co
CA, US
IPC
E21B 43/12
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