Abstract: A digital height encoder on a turret stockpicker is used to determine platform height. A pair of fixed reference switches are provided, one to reset a digital height memory to a predetermined height value each time the switch transitions either on or off, the other at a predetermined height near the staging point of telescoping masts for initial calibration of the encoder and for verification of proper operation during normal operations. If the height measurement indicated by the encoder upon the transition of the second or verificaiton switch is not within predetermined limits, an error signal is generated and recalibration will be required. Motion of the platform is also required if the control handle is in the upward direction and the platform has not reached its predetermined upper limits.

Abstract: A wire guidance system for a materials handling vehicle, such as a turret stockpicker, detects an alternating signal carried by a buried wire. Two sets of four sensors each are carried at either end of the vehicle. These sensors define regions, and a procedure is provided to determine in which region the wire is located. The distance and angle of the vehicle is determined by reference to the distance measurements of each sensor set, as calculated by a microcomputer. A self testing circuit is provided to insure proper operation of the sensors and associated circuitry.

Abstract: A wire guidance system for a materials handling vehicle, such as a turret stockpicker, detects an alternating signal carried by a buried wire. Two sets of four sensors each are carried at either end of the vehicle. The distance and angle of the vehicle is determined by reference to the distance measurements of each sensor set, as calculated by a microcomputer. Deviations in the angle or speed from predetermined limits will cause brakes to be applied and require operator intervention before the vehicle can be restarted.

Abstract: A wire guidance system for a materials handling vehicle, such as a turret stockpicker, detects an alternating signal carried by a buried wire by means of two sets of four sensors each carried at either end of the vehicle. An alarm, including both audio and visual means, having a first characteristic is generated if the vehicle is equipped with a functioning wire guidance system; an alarm having a second characteristic is generated when an active wire is detected and wire guidance has not been activated.

Abstract: A materials handling vehicle, such as a turret stockpicker, includes a telescoping mast comprising inner and outer sections. The staging of these sections, and the stopping of the platform assembly is smoothed by monitoring the actual height of the platform and restricting the speed of the platform as it approaches these transition points. The height of these transition points are stored in a digital memory. The platofrm speed is normally determined by a control handle, but as the platform reaches a transition point, the maximum speed of the platform is restricted by a micro-computer which controls a servo controlled hydraulic valve and the hydraulic pump motor supplying hydraulic fluid to the platform lifting cylinders. The maximum rate of platform movement after a transition is returned to the control of the operator.