Traversing hoists – Overhead – Surface vehicle
Reexamination Certificate
2000-01-07
2001-09-11
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Overhead
Surface vehicle
C212S344000
Reexamination Certificate
active
06286696
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the art of gantry cranes and more particularly to a gantry crane having a hydraulically actuated hoist system.
Gantry cranes are conventionally used in railyards, shipping yards, and other places for loading and unloading containers and loads to and from railcars, trailers, pallets, etc. Such a crane typically has a rigid steel frame that holds a grappler in an elevated manner. More particularly, the frame defines a wide central opening to span across or straddle a truck or railcar while suspending the movable grappler overhead. Typically, the frame includes a plurality of vertical beams mounted to a plurality of horizontal overhead beams. Such cranes are mobile, having a plurality of wheels on which the crane can be driven around a loading yard.
To movably support a grappler, a common crane design includes a pair of movable horizontal stabilizer beams. Each of these stabilizer beams extends between two of the vertical beams of the frame, the stabilizer beams being mounted for vertically slidable movement. The grappler is mounted to the stabilizer beam for lifting containers or other loads.
The crane includes a hoist system for vertically moving the stabilizer. In particular, the hoist system includes a hoist actuator operable to drive chains, cables or other hoist lines for vertically moving the stabilizer beams and the grappler. Through controlling the hoist actuator, the grappler can be raised or lowered to engage container. For example, the hoist actuator may be linear actuator such as a cylinder or a ball screw mechanism, which may be hydraulic, pneumatic, electric, etc.
Unfortunately, hoist actuators have been known to “drift” or slowly move under the load of the grappler over a period of time when the crane is parked. For example, in an embodiment wherein the hoist actuator is a hydraulic cylinder or motor, some degree of internal or external leakage can occur, particularly after seals become worn during service. If the hydraulic cylinder “drifts” due to internal leakage, the grappler slowly lowers toward the ground. The drifting movement is usually so slow as to be imperceptible over a short period to a human observer. This drifting can, however, be problematic.
In particular, the drifting of a grappler is dangerous if the crane has been parked to straddle a live railroad track or road. Cranes are often parked in this manner in a loading yard due to convenience or lack of space. Although an operator may have initially parked the crane with the grappler at a raised position to clear the travel path below, the hoist system may drift over time, causing the grappler to lower. An accident can occur if the grappler undesirably lowers into the pathway of a train or truck passing through the frame of the crane.
Accordingly, a need exists for a means to prevent drifting of the hoist system. More particularly, a need exists for locking the grappler in a raised position indefinitely.
SUMMARY OF THE INVENTION
The present invention overcomes problems in the prior art by providing a hoist locking device which can selectively secure the grappler in a raised position. For example, in an embodiment, the invention provides a gantry crane having frame and a hoist system. The hoist system includes a hoist actuator mounted to the frame, a hoist line (e.g., a cable, chain or other line) operably connected to the actuator for extending and retracting movement therewith, a grappler supported by the hoist line, and a hoist locking device. The hoist locking device is operable to selectively secure the hoist line in a predetermined position and thereby prevent downward movement of said grappler.
More particularly, in an embodiment, the hoist locking device includes a latch member movably mounted to the frame and a catch member fixed relative to the hoist line. The latch member is movable between a first position disengaged from catch member and a second position wherein the latch member engages the catch member to secure the hoist line in a predetermined position. The predetermined position is substantially fully raised, in order to provide maximum clearance under the grappler when the crane is parked.
In an embodiment, the latch member is a generally J-shaped hook having a contact surface for receiving the catch member and a pivot mounted to the frame. For example, in an embodiment, the contact surface is concave. This shape advantageously keeps the catch member gripped by the hook, causing an appropriate moment arm on the hook to maintain a secure engagement.
In an embodiment, the hoist locking device further includes a latching actuator for selectively driving the hook between the disengaged position and the engaged position. This latching actuator may, for example, be a hydraulic cylinder having one end mounted to the frame, and an opposite end mounted to the hook at a distance from the pivot. The latching actuator may be some other type of fluid driven or electromechanical actuator also. In an embodiment, the latching actuator is mounted to the hook at a position between the contact surface and the pivot. In another embodiment, the latching actuator is mounted to the hook at a position a distance from the pivot opposite the contact surface.
In an embodiment including a clevis for mounting the hoist lines to an end of the actuator, the catch member projects from the clevis.
An advantage of the present invention is that it provides an improved hoist system for a gantry crane.
Another advantage of the present invention is that it prevents a grappler from drifting while in a stored or parked state.
Additionally, the present invention enhances safety by keeping a safe clearance below the grappler.
Additional features and advantages of the present invention are described in, and will be apparent from, the description of the invention herein, the claims, and the drawings.
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Baty James
Glickman Myron
Van Gorp Eric Brian
Zakula, Sr. Daniel Brian
Brahan Thomas J.
Leydig , Voit & Mayer, Ltd.
Mi-Jack Products Inc.
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