Door interlock for an open-head power tong

Details Door interlock for an open-head power tong Door interlock for an open-head power tong

1978-05-01

1979-10-16

Jones, Jr., James L.

Tools

Wrench, screwdriver, or driver therefor

Machine

81 5715, B25B 1700

Patent

active

041709071

ABSTRACT:
An open-head power tong having an access door is provided with an improved door-interlock mechanism which ensures that the door is closed before the power tong can be operated. The interlock mechanism includes a pneumatically actuated contact valve connected to a pneumatically piloted hydraulic diverter valve which is operably associated with the hydraulic motor that drives the tong. The contact valve is so positioned on the tong such that the door when moved to its closed position engages the contact valve causing the flow of pneumatic pressure to the diverter valve to position the same so as to permit hydraulic fluid to flow to the hydraulic motor for operation of the power tong. When the door is in its open position, out of engagement with the contact valve, the contact valve relieves the pressure on the diverter valve thus positioning the diverter valve to divert the flow of hydraulic fluid around the hydraulic motor whereby the operation of the power tong is stopped.

REFERENCES:
patent: 2705614 (1955-04-01), McKibben et al.
patent: 3829703 (1974-08-01), Wilkie
patent: 4060014 (1977-11-01), Turner
patent: 4095493 (1978-06-01), Haynes

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