Fmc Corporation

Roger D Mickelson

John Eric Doyle

David L Willard

A multiple speed hoisting system has a first fluid circuit, with a maximum effective cross-sectional area for hoisting heavy loads at low speed, and a second fluid circuit, with a smaller effective cross-sectional area for hoisting lighter loads at higher speed. These circuits are separately actuated by a valve that is responsive to a regulating means for selectively positioning the valve. A pressure operated control, that is in flow communication with the second fluid circuit, automatically cancels the influence of the valve regulating means, in response to a predetermined pressure level in the second fluid circuit, and allows the valve to revert to a position actuating the first fluid circuit. Undesirable oscillations within the system between the pressure operated control and the valve regulating means are avoided. In a preferred embodiment of the invention, a pressure switch is the pressure operated control, a solenoid that is actuated by a manual control switch forms the regulating means for selectively positioning the valve, and a relay is provided to stabilize the electrical control circuit, thereby prevent hunting between the pressure switch and the solenoid controlled valve.

Multiple speed hoisting system with pressure protection and load control

A drum rotation indicator enables a crane operator to sense rotation of a drum, and thereby determine linear movement of a cable, that has one end wound about the drum. This indicator has a cam, that rotates with the drum, and a cam follower, that translates rotation of the cam into linear movement. A readout plunger is located conveniently for the operator's hand, and linear motion that is induced by the cam follower is transferred to the readout plunger by a medium that can be a mechanical linkage, a push-pull cable, or a hydraulic system. In a preferred embodiment of the invention, the cam follower disengages automatically from the cam after linear motion has been transferred to the readout plunger. The linear motion transferring medium also transfers motion from the readout plunger to the cam follower, which pivots into engagement with the cam. The cam has a serrated periphery, to give an instantaneous response, upon rotation of the drum, to engagement of the cam follower with the cam.

Drum rotation indicator

There is disclosed a telescoping boom with first and second motors, each connected between adjacent boom sections to extend and retract one boom section with respect to the other. Each motor has a piston slidably received in a cylinder to define an extend chamber on one side of the piston and a retract chamber on the other side thereof. Each piston has a rod extending from the cylinder which has two passages therein, one communicating with the extend chamber and the other communicating with the retract chamber. A control valve has a first portion for control of the first motor and a second portion for control of the second motor. The hydraulic passage between the retract chamber of the second motor and the second valve portion includes the retract chamber of the first motor. The hydraulic passage between the extend chamber of the second motor and the second valve portion, and only that passage, passes over a reel between said members.

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Cedar Rapids, IA, United States of America

Roger D Mickelson