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US 4,012,804 AGranted
Electromechanically operated dockboard
AssigneeKelley Company, Inc.
InventorJohn C. Catlett
Life of this patent
Estimating the term…
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AssigneeKelley Company, Inc.
InventorJohn C. Catlett
Estimating the term…
An electromechanically operated dockboard. The dockboard includes a ramp hinged at its rear edge to a supporting frame and the ramp is adapted to be moved from a generally horizontal cross traffic position to an upwardly inclined position by operation of a recirculating ball screw unit, which is connected between the frame and the ramp and is driven by a permanent magnet motor. A lip is hinged to the front edge of the ramp and can be pivoted from a pendant, downwardly hanging position to an extended position where it forms an extension to the ramp. Deactivation of the ball screw unit, after the ramp is elevated, causes the ramp to fall by gravity, and as the ramp descends, the lip is lifted to the extended position where it will engage the bed of the truck. During the descent of the ramp the ball screw unit is driven in a reverse direction and the permanent magnet motor serves as a brake to control the speed of descent.
In a dockboard construction to be associated with a loading dock, a supporting structure mounted on the dock, a ramp structure hinged at its rear end to the supporting structure and disposed to pivot from a generally horizontal cross traffic position to an upwardly inclined position, a drive unit interconnecting the supporting structure and the ramp structure for pivoting the ramp from the cross traffic position to the upwardly inclined position, said drive unit including a screw member and a nut member connected with the screw member, a first of said members being connected to the supporting structure and the second of said members being connected to said ramp structure, and a motor operably connected to the drive unit and being capable of being driven in one direction by a power source to effect relative movement between said nut member and said screw member to thereby move the ramp from the horizontal position to the upwardly inclined position, and said motor being driven in the reverse direction as the ramp structure descends by gravity from the inclined position toward the horizontal position to provide a dynamic braking action to control the descent of the ramp structure.
In a dockboard construction, a supporting structure, a ramp structure hinged at its rear end to the supporting structure and movable between a generally horizontal cross traffic position and an upwardly inclined position, a drive unit interconnecting the supporting structure and the ramp structure, said drive unit including a screw member having an external helical groove and also including a nut member having an internal helical groove, said drive member including a plurality of balls disposed within registering grooves in said screw member and said nut member, a first of said members being connected to the supporting structure and a second of said members being connected to the ramp structure, and a DC motor operably connected to the drive unit, operation of said motor in a first direction effecting relative movement between said nut member and said screw member in a first direction to thereby move the ramp structure from the cross traffic position to the upwardly inclined position, gravity descent of said ramp from the upwardly inclined position causing relative movement between said nut member and the screw member in the opposite direction to thereby drive the motor in an opposite direction, driving of the motor in an opposite direction producing a controlled descent of the ramp structure.
In a dockboard construction, a supporting structure, a ramp hinged at its rear edge to the supporting structure and movable between a generally horizontal cross traffic position and an upwardly inclined position, a lip hinged to the forward edge of the ramp and movable between a downwardly hanging pendant position and an extended position, a recirculating ball screw drive unit interconnecting the supporting structure and the ramp and including a base pivotally connected to the supporting structure, said drive unit also having a screw journalled for rotation with respect to the base and a nut engageable with said screw and movable along the length of said screw, said nut being connected to the ramp, and a DC permanent magnet motor operably connected to the screw to rotate the same, operation of the motor causing rotation of the screw in one direction to move the nut axially of the screw to thereby pivot the ramp from the cross traffic position to the upwardly inclined position, discontinuance of the operation of the motor causing the ramp to descend by gravity to move the nut axially of the screw and rotate the screw in the opposite direction, rotation of the screw in said opposite direction being transmitted to said motor to drive the motor in an opposite direction and brake the descent of the ramp.
Dependencies are inferred from the claim text.