Extend and retract control for fork lifts

• US 5,011,363 A
• Filed: 12/05/1989
• Issued: 04/30/1991
• Est. Priority Date: 12/05/1989
• Status: Expired due to Term

• Current Assignee: Crown Controls Corporation
• Original Assignee: Crown Equipment Corporation
• Inventors: Klopfleisch, Kim A., Dammeyer, Ned E., Conley, Walter III
• Primary Examiner(s): Werner, Frank E.
• Application Number:
  US07/446,222
• Time in Patent Office: 511 Days
• Field of Search: 74/471, 74/471 R, 74/491, 414/635, 414/640, 414/663, 414/785, 414/667, 414/671, 414/283, 414/286, 414/909, 414/630, 414/467, 414/666, 414/4, 414/664, 414/628, 414/469, 414/629, 414/631, 414/470 , 414/665, 414/659, 414/668, 414/673, 414/642, 414/282, 244/480, 244/636.3, 180/333, 180/315, 212/162, 212/163, 212/164, 212/160, 212/159, 60/551, 187/9 R, 187/9 E
• US Class Current: 414/666
• CPC Class Codes: B66F 9/10 movable in a horizontal direction relative to truck
• CPC Class Codes: B66F 9/143 Movements of forks relative to each other - symmetric
• CPC Class Codes: B66F 9/20 Means for actuating or controlling masts, platforms, or forks power take-off from vehicle transmissions, combined with vehicle propulsion systems B60K
• CPC Class Codes: Y10T 74/20201 Control moves in two planes

Abstract

A fork extension and retraction system for use with stockpickers automatically extends and retracts hydraulically extendable forks of a stockpicker when the load handler carrying the forks has moved to its extended position on the load side of the vehicle, and it also automatically retracts the forks if they have drifted from a home position before performing other fork related activities. Switches in the fork carriage assembly sense when the extendable forks are in the home position and near the home position. Other switches sense when the load handler assembly has reached its extreme positions on either side of the operator'"'"'s platform. Still other switches are used to slow the traverse movement of the load handler assembly as it approaches its extreme positions, thus to cushion the shock of the load handler stopping. A control circuit senses the condition of these switches and controls the operation of both the load handle and the fork extension hydraulic system.

Claims

1. In a materials handling vehicle including a power unit for moving the vehicle, a platform assembly supported on and being vertically movable relative to the power unit including an operator'"'"'s station and controls for operating various functions of said vehicle, a load handler assembly mounted for traverse movement across the platform assembly from a home position to a limit position, a traverse motor for moving said load handler assembly across the platform assembly, fork carriage assembly mounted on and vertically moveable relative to the load handler assembly, extendable forks carried by said fork carriage assembly and movable by fork extension cylinders, and a control handle for controlling the traverse movement of the load handler assembly, the improvement comprising

means responsive to movement of the control handle for controlling a supply of hydraulic fluid to power the traverse motor and to extend and retract the forks,

means for sensing the direction of movement of the control handle,

means for indicating the direction the load handler assembly is facing,

limit switch means for sensing when the fork carriage assembly has moved to its limit position on either side of the platform assembly,

transfer valve means for transferring hydraulic fluid between the traverse motor and the fork extension cylinders,

circuit means responsive to said control handle sensing means, said limit switch means and said direction indicating means for controlling said transfer valve whereby the movement of the load handler assembly and the extendable forks will be automatic in response to movement of the control handle.

2. The materials handling vehicle of claim 1 further including slowdown switch means for sensing the approach of the load handler assembly to its limit position, and means responsive to said slowdown switch means for reducing the flow of hydraulic fluid to the traverse motor prior to the fork carriage assembly engaging mechanical stop means.

3. The materials handling vehicle of claim 1 further including fork sensing means for indicating when the extendable forks are not in their home position, and wherein said circuit means will cause said forks to retract automatically upon any movement of the control handle.