EP0158456A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Industrial lift truck with travel/lift inhibit control
Assignee: Doosan Bobcat North America Inc
•
Filing: 1985-03-15
•
Granted: —
•
Expires: 2005-03-15
Abstract
Abstract A lift truck of the order-picker type is provided with an automatic control system for safe-guarding the operation against certain conditions. The electronic control system is responsive to an electrical height signal corresponding to the height of the lift fork (32) to regulate or limit the other operational functions of the truck. A speed control channel (152) compares a speed signal with a speed command signal and produces a speed control signal of limiting value. A travel interrupt channel (212) compares the height signal with the steering angle and interrupts the vehicle travel if the steering angle is excessive. Usually, the high speed lift is cut-off when a predetermined height is reached; the lowering of the upright (26) is disabled at a predetermined lower limit subject to manual override.
Inventors
- 👤 Donald Lew Schultz
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 15:29
CPC Classifications
B; B66; B66F; B66F17/00; B66F17/003
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
142 words
A lift truck of the type comprising an electric traction motor (24) manually controlled signal generating means (138) for generating a speed command signal voltage corresponding to a desired speed, an extendible upright (26), and control means (88) for said motor responsive to the speed control voltage for controlling the speed of said motor, characterised in comprising: signal generating means (52) operatively coupled with said upright (26) for generating a height signal voltage corresponding to the amount of extension of said upright, logic means (152) responsive to said speed command signal voltage and to said height signal voltage for producing a speed control voltage corresponding to the value of the larger of said signal voltages, and means for applying said speed control voltage to said control means whereby the speed of said motor is governed by only one of said signal voltages.
Claim 2
Dependent Claim
142 words
A lift truck of the type comprising an electric traction motor (24) manually controlled signal generating means (138) for generating a speed command signal voltage corresponding to a desired speed, an extendible upright (26), and control means (88) for said motor responsive to the speed control voltage for controlling the speed of said motor, characterised in comprising: signal generating means (52) operatively coupled with said upright (26) for generating a height signal voltage corresponding to the amount of extension of said upright, logic means (152) responsive to said speed command signal voltage and to said height signal voltage for producing a speed control voltage corresponding to the value of the larger of said signal voltages, and means for applying said speed control voltage to said control means whereby the speed of said motor is governed by only one of said signal voltages.
Claim 3
Dependent Claim
47 words
A lift truck according to claim 1 wherein, said height signal generating means (52) generates a signal voltage which varies directly with extension of said upright (26), and said speed signal generating means (138) generates a speed command signal voltage which varies inversely with the desired speed.
Claim 4
Dependent Claim
75 words
A lift truck according to claim 1 or 2, wherein said lift truck includes a manually controlled dirigible wheel (14) lift means (28) for extending said upright, steering signal generating means (62) for generating a signal voltage corresponding to a steering angle of said dirigible wheel, and travel interrupt control means (212) responsive to said steering signal for deenergizing said motor (24) to stop said lift truck when the steering signal exceeds a predetermined value.
Claim 5
Dependent Claim
87 words
A lift truck according to claim 1, 2 or 3, wherein said lift truck also includes a manually controlled low speed lowering means (74) for said upright (26), reference voltage generating means (318) for generating an adjustable reference voltage corresponding to the lower limit of height for said upright, comparing means (326) for comparing said adjustable reference voltage with said height signal voltage, and logic means coupled with said comparing means for disabling said lowering means when the height of the upright corresponds to said lower limit.
Claim 6
Dependent Claim
28 words
A lift truck according to claim 4, including a manual override switch (352) coupled with said logic means for preventing said logic means from disabling said lowering means.
Claim 7
Dependent Claim
93 words
A lift truck according to claim 4 or 5, wherein said lift truck also includes a manually controlled high speed lowering means (76) for said upright, said reference signal generating means (318) for generating a signal voltage corresponding to the lower limit of said upright, comparing means (396) for comparing said second lower limit signal voltage with said height signal voltage for producing a disabling signal voltage when said height signal voltage corresponds to said second limiting reference voltage, and switching means (398) responsive to said disabling signal for disabling said lowering means.
Claim 8
Dependent Claim
51 words
A lift truck according to claim 4, 5 or 6, wherein said lift truck also includes a sensing means (414) for sensing an obstruction in the lowering of said extendible upright and means (418) for coupling said sensing means with switching means (316) to disable said low speed lowering means (74).
Claim 9
Dependent Claim
70 words
A lift truck according to any one of the preceding claims, wherein said lift truck also includes a manually controlled low speed lift means (96) for said upright, reference means (456) for generating a lift interrupt height signal, comparing means (458) for comparing the lift interrupt height signal and said height signal and for disabling said low speed lift means when the height signal exceeds said lift interrupt height signal.
Claim 10
Dependent Claim
76 words
A lift truck according to any one of the preceding claims, wherein said lift truck also includes a manually controlled high speed lift means (102) for said upright, reference means (512) for generating a high speed lift interrupt height signal, comparing means (506) for comparing the high speed lift interrupt height signal and said height signal and for disabling said high speed lift means when said height signal exceeds said high speed lift interrupt height signal.
Claim 11
Dependent Claim
87 words
A lift truck according to any one of the preceding claims, wherein said lift truck includes manually controlled low speed lift means (96) and manually controlled high speed lift means (102) for said upright, first electronic switching means (454) for controlling said low speed lift means and second electronic switching means (508) for controlling said high speed lift means, and battery voltage responsive means (532) for preventing the turn-on of said first and -second electronic switching means when said battery voltage is less than a predetermined value.
Claim 12
Dependent Claim
88 words
A lift truck according to any one of the preceding claims, said lift truck including a hydraulic lift circuit for extending said upright, pressure sensing means (564) coupled with said hydraulic circuit for producing an overload signal when the hydraulic pressure exceeds a predetermined value, alarm means (64) for warning the operator of an overload, switching means responsive to said overload signal for energizing said alarm means, and logic means responsive to said low speed lift signal and said low speed lower signal for disabling said switching means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.