Harnischfeger Corporation

Michael D James

Neal Charles Eriksson

Robert H Reuss

Peter A Kerrick

Jan B Loebel

A support apparatus for the operator's cab of an overhead crane. The crane has a rigid depending mast and an intermediate mast and carriage vertically movable on the rigid mast for lifting and carrying a load. A hoist is mounted on the crane and attached to the carriage for raising and lowering the carriage, the intermediate mast and the load at normal operating speeds. The support apparatus includes a first support affixed to the cab and the intermediate mast for supporting the cab on the intermediate mast during normal operating speeds of the intermediate mast. The first support permits detaching the cab from the intermediate mast upon the occurrence of an excessive lowering operating speed of the intermediate mast. A second support affixed to the cab and to an overhead support of the crane then supports the cab in a suspended manner and the intermediate mast drops toward the floor below the crane without the cab. A sensing mechanism may also be provided for detecting excessive lowering overspeed of the intermediate mast and producing an indication of the overspeed to the second support. The second support is responsive to the excessive lowering speed indication of the sensing mechanism to support the cab.

Suspending support for a crane cab

A hoist drive for a double hoist carrying member having a hold hoist drum, a hold rope connected to the hold hoist drum and from which the carrying member is suspended, and a hold motor for rotating the hold hoist drum to raise and lower the carrying member. The hoist drive further includes a close hoist drum, a close rope connected to the close hoist drum and from which the carrying member is suspended, and a close motor for rotating the close hoist drum to raise and lower the carrying member. During raising of the carrying member, the hold and close motors are each supplied with a.c. power at different preselected frequencies. The hold and close motors each operate along a first pair of intersecting frequency to torque curves during a raising operation in which the hold motor curve is steeper than the close motor curve. During a lowering operation the hold and close motors operate along a second pair of intersecting frequency to torque curves in which the hold motor curve is also steeper than the close motor curve. Due to the intersection and relative slopes of the first pair and the second pair of curves, the speed of the hold motor follows the speed of the close motor during both raising and lowering operation and the motors operate at the intersection points of the pairs of curves and share the load during both raising and lowering operation.

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Franklin, WI, United States of America

Michael D James