Control device for loading and unloading mechanism
First Claim
1. A control device for a loading and unloading mechanism adapted to a fork lift truck comprising:
- (a) a sensor unit including a lifting height sensor for measuring lifting height of a fork and producing output signals indicative thereof,(b) a control unit including(i) an interface circuit having a lifting height counter for counting the output signals from the sensor unit,(ii) a memory for storing data indicative of lifting height, said memory storing a data pattern shown target lifting height speeds with respect to an absolute value of a difference between a target lifting height and the present lifting height,(iii) data input means for inputting control data indicative of lifting height into the memory, and(iv) a control command producing circuit for performing a comparison calculation between the output signals of the sensor unit and the data stored in the memory, and for producing a valve opening command based on the comparison, said control command producing circuit operable for producing a control command for a target lifting speed in accordance with the difference read from said data pattern and in accordance with a current lifting height speed,(c) a servomotor driving circuit for producing a control signal responsive to the valve opening command signal from the control unit,(d) hydraulic pressure driving circuit producing a further control signal for hydraulically controlling a lift cylinder to vary the lifting height of the fork in accordance with the control signal fed from the servomotor driving circuit, and(e) inhibiting means in said control device for inhibiting storage in said memory of lifting height control data when the sensed lifting height is above a preselected upper limit or below a preselected lower limit, thereby to prevent erroneous operations and to smoothly effect an automatic lifting height control.
1 Assignment
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Accused Products
Abstract
A control device for loading and unloading mechanism adapted to be incorporated in a fork lift truck comprises a sensor unit 100 including a lifting height sensor 102, a control unit 200 comprising a control command producing circuit 240 constituted by a microcomputer 230 producing a control command on the basis of comparing calculation between the output of the sensor unit 100 and the concerned data stored in the microcomputer 230, and a driving unit 300 producing a driving output signal so as to the lifting height of the fork 18 in accordance with the control command fed from the control unit 200. The control device includes a component operable for inhibiting storage of sampled lifting height data when the actual lifting height data are not within an allowed range, thereby to prevent erroneous operation based on erroneous data and to effect smooth follow-up speed control to the target height when automatic lifting height control is effected. The control device further comprises structure for slowly stopping the fork at the time of the automatic lifting height control. Prior to the automatic lifting height control, when lifting height data is stored in the microcomputer 230, the control device is designed so that lifting height data within a predetermined range can be sampled. Furthermore, the valve opening angle of the control valve for actuating a lift cylinder 346 is limited to a predetermined range, thereby stabilizing a lifting height speed.
55 Citations
19 Claims
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1. A control device for a loading and unloading mechanism adapted to a fork lift truck comprising:
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(a) a sensor unit including a lifting height sensor for measuring lifting height of a fork and producing output signals indicative thereof, (b) a control unit including (i) an interface circuit having a lifting height counter for counting the output signals from the sensor unit, (ii) a memory for storing data indicative of lifting height, said memory storing a data pattern shown target lifting height speeds with respect to an absolute value of a difference between a target lifting height and the present lifting height, (iii) data input means for inputting control data indicative of lifting height into the memory, and (iv) a control command producing circuit for performing a comparison calculation between the output signals of the sensor unit and the data stored in the memory, and for producing a valve opening command based on the comparison, said control command producing circuit operable for producing a control command for a target lifting speed in accordance with the difference read from said data pattern and in accordance with a current lifting height speed, (c) a servomotor driving circuit for producing a control signal responsive to the valve opening command signal from the control unit, (d) hydraulic pressure driving circuit producing a further control signal for hydraulically controlling a lift cylinder to vary the lifting height of the fork in accordance with the control signal fed from the servomotor driving circuit, and (e) inhibiting means in said control device for inhibiting storage in said memory of lifting height control data when the sensed lifting height is above a preselected upper limit or below a preselected lower limit, thereby to prevent erroneous operations and to smoothly effect an automatic lifting height control. - View Dependent Claims (2, 3, 4)
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5. A control device for a loading and unloading mechanism adapted to a fork lift truck comprising:
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(a) a sensor unit including a lifting height sensor for measuring lifting height of a fork and producing output signals indicative thereof, (b) a control unit including (i) an interface circuit having a lifting height counter for counting the output signals from the sensor unit, (ii) a memory for storing data indicative of lifting height, said memory storing a data pattern showing target lifting height speeds with respect to an absolute value of a difference between a target lifting height and the present lifting height, (iii) data input means for inputting control data indicative of lifting height into the memory, and (iv) a control command producing circuit for performing a comparison calculation between the output signals of the sensor unit and the data stored in the memory, and for producing a valve opening command based on the comparison, said control command producing circuit operable for producing a control command for a target lifting speed in accordance with the difference read from said data pattern and in accordance with a current lifting height speed, (c) a servomotor driving circuit for producing a control signal responsive to the valve opening command signal from the control unit, (d) a hydraulic pressure driving circuit producing a further control signal for hydraulically controlling a lift cylinder to vary the lifting height of the fork in accordance with the control signal fed from the servomotor driving circuit, (e) feedback control means responsive to said command signal for performing a predetermined lifting height operation when said command signal is generated so that the fork-lift response to said command signal is properly produced when the lifting height control operation is effected, and (f) inhibiting means in said control device for inhibiting storage in said memory of lifting height control data when the sensed lifting height is above a preselected upper limit or below a preselected lower limit, thereby to prevent erroneous operations and to smoothly effect an automatic lifting height control. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A control device for a loading and unloading mechanism adapted to a fork lift truck comprising:
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(a) a sensor unit including a lifting height sensor for measuring lifting height of a fork and producing output signals indicative thereof, (b) a control unit including (i) an interface circuit having a lifting height counter for counting the output signals from the sensor unit, (ii) a memory for storing data indicative of lifting height, said memory storing a data pattern showing target lifting height speeds with respect to an absolute value of a difference between a target lifting height and the present lifting height, (iii) data input means for inputting control data indicative of lifting height into the memory, and (iv) a control command producing circuit for performing a comparison calculation between the output signals of the sensor unit and the data stopped in the memory, and for producing a valve opening command based on the comparison, said control command producing circuit operable for producing a control command for a target lifting speed in accordance with the difference read from said data pattern and in accordance with a current lifting height speed, (c) a servomotor driving circuit for producing a control signal responsive to the valve opening command signal from the control unit, (d) a hydraulic pressure driving circuit producing a further control signal for hydraulically controlling a lift cylinder to vary the lifting height of the fork in accordance with the control signal fed from the servomotor driving circuit, (e) said hydraulic pressure driving circuit including means for providing speed control signals to control speed of operation of the lift cylinder including first and second feedback loops, (f) said first feedback loop providing said output signals of said height sensor to said control command producing unit for calculating therefrom a speed of fork lifting operation and for comparison of the calculated speed with a target speed, (g) said second feedback loop providing a signal representative of an actual valve opening corresponding to a rotating position of a valve driving motor driven by said servomotor driving circuit for comparing said control signal with a signal representative of actual valve opening, and (h) inhibiting means in said control device for inhibiting storage in said memory of lifting height control data when the sensed lifting height is above a preselected upper limit or below a preselected lower limit, thereby to prevent erroneous operations and to smoothly effect an automatic lifting height control. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A control device for a loading and unloading mechanism adapted to a fork lift truck comprising:
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(a) a sensor unit including a lifting height sensor for measuring lifting height of a fork and producing output signals indicative thereof, (b) a control unit including (i) an interface circuit having a lifting height counter for counting the output signals from the sensor unit, (ii) a memory for storing data indicative of lifting height, (iii) data input means for inputting control data indicative of lifting height into the memory, and (iv) a control command producing circuit for performing a comparison calculation between the output signals of the sensor unit and the data stored in the memory, and for producing a valve opening command based on the comparison, (c) a servomotor driving circuit for producing a control signal responsive to the valve opening command signal from the control unit, (d) a hydraulic pressure driving circuit producing a further control signal for hydraulically controlling a lift cylinder to vary the lifting height of the fork in accordance with the control signal fed from the servomotor driving circuit, (e) said hydraulic pressure driving circuit including means for providing speed control signals to control speed of operation of the lift cylinder including first and second feedback loops, (f) said first feedback loop providing said output signals of said height sensor to said control command producing unit for calculating therefrom a speed of fork lifting operation and for comparison of the calculated speed with a target speed, (g) said second feedback loop providing a signal representative of an actual valve opening corresponding to a rotating position of a valve driving motor driven by said servomotor driving circuit for comparing said control signal with a signal representative of actual valve opening, and (h) inhibiting means in said control device for inhibiting storage in said memory of lifting height control data when the sensed lifting height is above a preselected upper limit or below a preselected lower limit, thereby to prevent erroneous operations and to smoothly effect an automatic lifting height control, (i) said means for providing speed control signals including processing means programmed for providing follow-up height lift speed control by; determining whether a difference exists between a target height and a present height; when no difference is determined to exist, terminating the follow-up lift speed control; when a difference is determined to exist, setting a target speed as a function of the determined difference; determining present lift speed; calculating a relative difference between present and target speed; selecting one of a plurality of positive and a plurality of negative speed increment commands in accordance with the calculated relative difference; and incrementing the present speed by a number of steps determined in response to the selected speed increment command. - View Dependent Claims (19)
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Specification