Height sensor for turret stockpicker

• US 5,103,226 A
• Filed: 12/05/1989
• Issued: 04/07/1992
• Est. Priority Date: 12/05/1989
• Status: Expired due to Term

• Current Assignee: Crown Controls Corporation
• Original Assignee: Crown Equipment Corporation
• Inventors: Wellman, Tim A., Dammeyer, Ned E.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Kim, Helen
• Application Number:
  US07/446,223
• Time in Patent Office: 854 Days
• Field of Search: 341/5, 341/6, 341/11, 341/13, 341/14, 341/116, 414/14, 414/15, 414/16
• US Class Current: 341/14
• CPC Class Codes: B66F 17/003 for fork-lift trucks
• CPC Class Codes: H03M 1/1014 at one point of the transfer characteristic, i.e. by adjusting a single reference value, e.g. bias or gain error gain setting for range control H03M1/18
• CPC Class Codes: H03M 1/308 with additional pattern means for determining the absolute position, e.g. reference marks

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.

Claims

1. A method of measuring the height of a platform assembly of a turret stockpicker comprising the steps of

sensing the position of a first switch placed at a first known height,

sensing the position of a second switch placed at a second known height,

rotating a digital encoder in response to the vertical movement of the platform,

comparing the output of the digital encoder to the first and second known heights and generating an encoder scale factor,

storing the encoder scale factor in a memory, height measurements by reference to the encoder scale factor,

storing a fixed value in an encoder height memory each time said first switch is actuated,

storing a fixed value representing the height of said second switch in a verification height memory,

comparing the absolute encoder generated height measurements with the verification height memory each time said second switch is actuated,

generating an error signal if said absolute encoder generated height measurement differs from said verification height by more than a predetermined amount.

2. An apparatus for measuring the height of a platform assembly of a turret stockpicker, said apparatus including

control handle means for indicating the direction and speed of platform movement,

means responsive to the position of said control handle means for moving the platform assembly,

reset switch means positioned at a first predetermined height,

height memory means responsive to a transition in said reset switch for recording the first predetermined height measurement,

verification switch means positioned at a second predetermined height,

verification memory means for storing the height of said second switch means,

digital encoder means for indicating the height of the platform assembly and for providing said height memory means with the current height measurement,

means for comparing the transition of said verification switch means with said height memory means and for providing an error signal if said height measurements differ by more than a predetermined amount.