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A shelf height selector system for a lift truck provides signals to an operator as he raises or lowers a load carriage relative to a storage shelf level selected by a keyboard in order to perform a store or retrieve operation, and automatically stops carriage movement with load forks at the proper e

A shelf height selector system for a lift truck provides signals to an operator as he raises or lowers a load carriage relative to a storage shelf level selected by a keyboard in order to perform a store or retrieve operation, and automatically stops carriage movement with load forks at the proper elevation. Pulses from an incremental shaft encoder operated by carriage movement are counted to provide an instantaneous elevation signal upon which indications to the operator and control functions depend. A switch on the truck mast is operated by carriage movement to repeatedly recalibrate a register containing the instantaneous elevation signal, obviating any errors should noise affect tallying of encoder counts. An optical sensor carried on the load carriage to sense reflective markers adjacent some shelves also recalibrates the register, obviating positioning errors due to mast deflection and tire wear. Provision of a simple programming arrangement allows storage of shelf heights in a non-volatile random-access memory, affording the advantages of a field-programmable system.

대표청구항 ▼

1. In a lift truck having means for vertically moving a load carriage up and down a mast, the combination of a rotary shaft encoder means connected to be operated by vertical movement of said carriage and operable to provide signals representing incremental vertical movement of said carriage; a proc

1. In a lift truck having means for vertically moving a load carriage up and down a mast, the combination of a rotary shaft encoder means connected to be operated by vertical movement of said carriage and operable to provide signals representing incremental vertical movement of said carriage; a processor having an arithmetic unit, a read-only memory containing program instructions and data, random-access memory means including a non-volatile random-access memory unit, and means for transmitting and receiving data, said processor being connected to receive said signals representing incremental vertical movement of said carriage and operable by a portion of said instructions to increment and decrement a first register means in said memory means to provide data representing the current elevation of said carriage; a manually-operable keyboard means carried on said truck for selecting shelves at which loads are to be stored or retrieved, a first group of said instructions being operable in response to an entry on said manually-operable keyboard means to read elevation data from an address in said non-volatile memory unit computed from said entry and to control said means for moving said load carriage in accordance with a function of the difference between said elevation data and the contents of said first register means; a manually-controlled switch operable to provide a programming mode of operation, a second group of said instructions being operable in response to an entry on said manually-operable keyboard during said programming mode of operation to transfer the data from said first register means to an address in said memory unit computed from said entry during said programming mode of operation. 2. The truck according to claim 1 having an operator-controlled switch for selecting a store or a retrieve mode of operation, said first group of said instructions being operable in controlling said means for moving said load carriage to add a first predetermined value to said elevation data during a store mode of operation and to add a second predetermined value to said elevation data during a retrieve mode of operation. 3. The truck according to claim 1 wherein said encoder means includes means for producing pulse signals during increments of vertical movement of said load carriage and means for producing a logic signal having a state which indicates the direction of said vertical movement at the time of occurrence of each of said pulse signals, said pulse signals being connected to interrupt said processor, said instructions including an interrupt routine operable upon occurrence of any of said pulse signals to increment or decrement said first register means depending upon the state of said logic signal. 4. The lift truck according to claim 1 which includes first switch means positioned on said mast to be operated when said load carriage reaches a predetermined vertical position on said mast, a third group of said instructions being operable upon each operation of said first switch means to store a predetermined value in said first register means. 5. The truck according to claim 2 wherein said first and second predetermined values are stored in said read-only memory. 6. The truck according to claim 2 wherein said truck has a plurality of selectively-energized conductors forming third and forth registers to store said first and second predetermined values. 7. The truck according to claim 2 wherein said program instructions include a third group of instructions for computing said first and second predetermined values. 8. The truck according to claim 4 wherein said predetermined value is stored in said read-only memory. 9. The truck according to claim 4 having a plurality of selectively-energized conductors forming a register storing said predetermined value. 10. The truck according to claim 4 wherein said program instructions include a fourth group of instructions for computing said predetermined value. 11. The truck according to claim 4 wherein said program instructions include a start-up routine operable to set a flag upon start-up of said processor, operation of said first switch means being operable to clear said flag. 12. The lift truck according to claim 11 wherein said read-only memory includes an instruction which prevents completion of said second group of instructions if said flag is set. 13. A material handling vehicle having hoist means for vertically moving a load carriage up and down a mast, rotary shaft encoder means mechanically connected to be operated by vertical movement of said carriage and operable to provide successive electrical signals representing incremental movement of said carriage; counting means for tallying said electrical signals to provide a first data signal in a first register representing the current elevation of a portion of said carriage; an operator-controllable keyboard digit entry means aboard said vehicle for providing a second data signal representing a desired shelf; processor means responsive to said first and second data signals for either controlling said hoist means or for storing said first data signal at a memory location of said processor means dependent upon said second data signal; and manually-controllable switch means aboard said vehicle for selecting the response of said processor to said first and second data signals. 14. The vehicle according to claim 13 having sensor means vertically movable with said load carriage for sensing objects carried on storage racks at predetermined elevations to provide sensor signals; and means responsive to one of said sensor signals for storing a value commensurate with said second data signal in said first register. 15. The vehicle according to claim 13 having a photosensor movable vertically with said carriage and operable to provide flag signals upon sensing objects carried on storage racks adjacent to which said vehicle may be positioned, and means for updating said first data signal to a value computed from said second data signal upon the occurrence of one of said flag signals. 16. The vehicle according to claim 14 wherein said sensor means comprises an optical sensor and said objects carried on storage racks comprise reflective targets. 17. A vehicle according to claim 15 wherein the last-recited means is operable to combine said second data signal with a predetermined value to provide the updated value of said first data signal. 18. A vehicle according to claim 15 wherein the last-recited means is operable to ignore said flag signals unless the difference between said second and first data signals is less than a predetermined value. 19. A vehicle according to claim 15 having means for preventing said updating of said first data signal unless said carriage is moving in a predetermined direction at the time of occurrence of said one of said flag signals. 20. A controller for an auxiliary mechanism of an industrial truck, comprising: sensing means coupled to detect movement of said mechanism and provide signals denoting increments of that movement; means for receiving and accumulating said signals to provide a count in a first register denoting the position of the mechanism along its range of movement; a memory which is addressable to provide a designated one of a plurality of stored representations for comparison with said count in said first register; means cooperating with said memory for designating one of said stored representations; means for comparing the count with said designated representation made available from the memory to provide a signal for controlling the movement of the mechanism; means for effecting storage in the memory of signals denoting different positions along the range of movement; and means for transferring a count in said first register to the memory for storage as one of said plurality of representations. 21. A controller for an auxiliary mechanism of an industrial truck, comprising: a sensor which is coupled to detect movement of the said mechanism and provides signals denoting increments of that movement; a counter which receives said signals and thereby provides a count denoting the position of the mechanism along its range of movement; a memory which is controllable to provide one of a plurality of stored representations for comparison with said count; means for comparing the count with a representation made available from the memory to provide a signal for controlling the movement of the mechanism; means for effecting storage in the memory of signals denoting different positions along the range of movement; a keyboard means, operable by a human operator, for effecting storage of said count by said memory in a storage location of which the address is determined by the operation of a particular selection from said keys; and means responsive to operation of the keyboard to address the memory to make the stored count available for comparison.