Elevator – industrial lift truck – or stationary lift for vehicle – Industrial lift truck or required component thereof – Having safety cutoff control
Patent
1994-03-03
1995-10-31
Noland, Kenneth
Elevator, industrial lift truck, or stationary lift for vehicle
Industrial lift truck or required component thereof
Having safety cutoff control
187229, B66B 920
Patent
active
054621364
ABSTRACT:
The present invention features a method and an apparatus for preventing lift chains from becoming slack in a lift truck with a "man-up" feature installed. Lift trucks are generally those vehicles that feature hydraulically controlled lift masts with a chain supported fork carriage. Operators of these lift vehicles with the remote lift and lower feature are generally lifted and lowered by these masts, known in the trade as a "man-up" condition. It is quite desirable to prevent a slack chain condition in the man-up mast position. The invention features a pressure transducer for monitoring a drop in hydraulic fluid pressure established by the flow control valve that regulates the lowering speed of the mast during the remote mode, i.e., when the fork carriage is being lowered by the operator in the platform attached to the fork carriage. The invention turns off the normally closed load-holding valve when the hydraulic pressure drops below a predetermined value, which stops the flow of hydraulic fluid back into the reservoir. This, in turn, stops the cylinder(s) from lowering and keeps the fork carriage lift chains from becoming slack.
REFERENCES:
patent: 4252491 (1981-02-01), Hock
patent: 4499971 (1985-02-01), Luebrecht et al.
patent: 5238086 (1993-08-01), Aoki et al.
Mathes Gene R.
Schoenmaker John
Noland Kenneth
The Raymond Corporation
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