True crab steering apparatus

• US 6,371,243 B1
• Filed: 02/13/2001
• Issued: 04/16/2002
• Est. Priority Date: 02/13/2001
• Status: Expired due to Term

• Current Assignee: Terex South Dakota, Inc. (Terex Corporation)
• Original Assignee: Genie Industries Incorporated (Terex Corporation)
• Inventors: Donaldson, James, Wong, Nelson
• Primary Examiner(s): Stodola, Daniel P.
• Assistant Examiner(s): Thompson, Hugh B.
• Application Number:
  US09/782,922
• Time in Patent Office: 427 Days
• Field of Search: 182/69.4, 182/63.1, 182/148, 182/141, 180/411, 180/414, 180/415, 180/326, 180/327
• US Class Current: 182/69.4
• CPC Class Codes: B62D 7/1509 with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle
• CPC Class Codes: B66F 11/04 for movable platforms or cabins, e.g. on vehicles, permitting workmen to place themselves in any desired position for carrying out required operations Working platforms on fork-lift trucks B66F9/127; vehicle aspects of service vehicles B60P3/14; platforms for cleaning windows A47L3/02; devices for rescuing persons from buildings A62B1/02; liftable or lowerable platforms for use on ladders E06C7/16; maintenance travellers for bridges E01D19/10; scaffolds on an extensible sub-structure E04G1/22

Abstract

A mobile lift having extendable axes that is capable of switching between front-wheel steer, rear-wheel steer, all-wheel steer, and crab steer without resulting in undesirable tire scrubbing or unfavorable steering geometry. One embodiment provides a mobile personnel lift having a chassis supported by steerable front and rear wheel sets. The steerable wheel sets are mounted on axles that are extendable and retractable. A double-acting hydraulic cylinder is pivotally coupled between each steerable wheel and its corresponding axle for turning the wheel. A microprocessor controls the flow of hydraulic fluid to the hydraulic cylinders. Sensors positioned adjacent to each wheel measure the angular position of each wheel relative to the chassis, and transmit this information to the microprocessor to synchronize the wheels as required to provide the optimum steering geometry for the selected mode.

Claims

1. A mobile lift having a true crab steering apparatus, the mobile lift comprising:

a lift assembly;

a chassis having a longitudinal axis and a left front portion, a right front portion, a left rear portion, and a right rear portion, the lift assembly being mounted to the chassis;

a left front axle extensibly mounted to the left front portion of the chassis and being moveable relative to the chassis between extended and retracted positions;

a right front axle extensibly mounted to the right front portion of the chassis in axial alignment with the left front axle and being moveable relative to the chassis between extended and retracted positions;

a left rear axle extensibly mounted to the left rear portion of the chassis and being moveable relative to the chassis between extended and retracted positions;

a right rear axle extensibly mounted to the right rear portion of the chassis in axial alignment with the left rear axle and being moveable relative to the chassis between extended and retracted positions;

a front wheel set having a left front wheel and a right front wheel, the left front wheel being rotatably mounted to the left front axle, the right front wheel being rotatably mounted to the right front axle, the left and right front wheels being turnable relative to the longitudinal axis of the chassis;

a rear wheel set having a left rear wheel and a right rear wheel, the left rear wheel being rotatably mounted to the left rear axle, the right rear wheel being rotatably mounted to the right rear axle, the left and right rear wheels being turnable relative to the longitudinal axis of the chassis;

a left front actuator operably coupled between the left front wheel and the left front axle, the left front actuator being extendable and retractable relative to the chasis causing the left front wheel to turn relative to the longitudinal axis of the chassis;

a right front actuator operably coupled between the right front wheel and the right front axle, the right front actuator being extendable and retractable relative to the chasis causing the right front wheel to turn relative to the longitudinal axis of the chassis, the right front actuator being operably independent from the left front actuator;

a left rear actuator operably coupled between the left rear wheel and the left rear axle, the left rear actuator being extendable and retractable relative to the chasis causing the left rear wheel to turn relative to the longitudinal axis of the chassis;

a right rear actuator operably coupled between the right rear wheel and the right rear axle, the right rear actuator being extendable and retractable relative to the chasis causing the right rear wheel to turn relative to the longitudinal axis of the chassis, the right rear actuator being operably independent from the left rear actuator; and

a control system operably connected to the left and right front actuators and the left and right rear actuators, wherein the control system is adjustable between a front-wheel steer mode, a rear-wheel steer mode, an all-wheel steer mode, and a crab steer mode, in the front-wheel steer mode and the all-wheel steer mode, the left and right front wheels are non-parallel to each other when the front wheel set is turned relative to the longitudinal axis of the chassis, in the rear-wheel steer mode and the all-wheel steer mode, the left and right rear wheels are non-parallel to each other when the rear wheel set is turned relative to the longitudinal axis of the chassis, and in the crab steer mode, the left and right front wheels, and the left and right rear wheels, are at least substantially parallel to each other when the front and rear wheel sets are turned relative to the longitudinal axis of the chassis.

2. The mobile lift of claim 1 wherein:

the left and right front actuators are mounted exterior of the left and right front axles, respectively; and

the left and right rear actuators are mounted exterior of the left and right rear axles, respectively.

3. The mobile lift of claim 1 wherein the control system comprises:

a microprocessor operably connected to the left and right front actuators and the left and right rear actuators;

a directional switch operably connected to the microprocessor, the directional switch being movable between a full left position and a full right position; and

a steering mode selection box operably connected to the microprocessor and adjustable to select between the front-wheel steer mode, the rear-wheel steer mode, the all-wheel steer mode, and the crab steer mode, in the front-wheel steer mode the microprocessor causes the left and right front wheels to turn non-parallel to each other in response to movement of the directional switch to the full left or full right positions, in the rear-wheel steer mode the microprocessor causes the left and right rear wheels to turn non-parallel to each other in response to movement of the directional switch to the full left or full right positions, in the all-wheel steer mode the microprocessor causes the left and right front wheels to turn in a first direction non-parallel to each other, and causes the left and right rear wheels to turn in a second direction opposite the first direction non-parallel to each other in response to movement of the directional switch to the full left or full right positions, and in the crab steer mode the microprocessor causes the left and right front wheels, and the left and right rear wheels, to turn in the same direction at least substantially parallel to each other in response to movement of the directional switch to the full left or full right positions.

4. The mobile lift of claim 1 further comprising:

a left front sensor positioned adjacent to the left front wheel, the left front sensor being operably connected to the control system and configured to measure a turn angle of the left front wheel relative to the longitudinal axis of the chassis; and

a right front sensor operably independent of the left front sensor and positioned adjacent to the right front wheel, the right front sensor being operably connected to the control system and configured to measure a turn angle of the right front wheel relative to the longitudinal axis of the chassis.

5. The mobile lift of claim 1 wherein the left and right front actuators and the left and right rear actuators are double-acting hydraulic cylinders.

6. The mobile lift of claim 1 wherein the left and right front actuators and the left and right rear actuators are double-acting hydraulic cylinders configured to receive and return a flow of hydraulic fluid, the mobile lift further comprising:

a first valve operably connected to the control system for controlling the flow of hydraulic fluid to the left front actuator;

a second valve operably connected to the control system for controlling the flow of hydraulic fluid to the right front actuator;

a third valve operably connected to the control system for controlling the flow of hydraulic fluid to the left rear actuator; and

a fourth valve operably connected to the control system for controlling the flow of hydraulic fluid to the right rear actuator.

7. The mobile lift of claim 6 wherein the first, second, third, and fourth valves are closed-center three-position four-way valves.

8. A mobile lift having a true crab steering apparatus, the true crab steering apparatus being useable for steering the mobile lift in a first steer mode wherein corresponding left and right wheels are turned non-parallel to each other, and useable for steering the mobile lift in a second steer mode wherein corresponding left and right wheels are turned at least substantially parallel to each other, the mobile lift comprising:

a lift assembly;

a chassis having a longitudinal axis and a left front portion, a right front portion, a left rear portion, and a right rear portion, the lift assembly being mounted to the chassis;

a left front axle extensibly mounted to the left front portion of the chassis and being moveable relative to the chassis between extended and retracted positions;

a right front axle extensibly mounted to the right front portion of the chassis in axial alignment with the left front axle and being moveable relative to the chassis between extended and retracted positions;

a left rear axle extensibly mounted to the left rear portion of the chassis and being moveable relative to the chassis between extended and retracted positions;

a right rear axle extensibly mounted to the right rear portion of the chassis in axial alignment with the left rear axle and being moveable relative to the chassis between extended and retracted positions;

a front wheel set having a left front wheel and a right front wheel, the left front wheel being rotatably mounted to the left front axle, the right front wheel being rotatably mounted to the right front axle, the left and right front wheels being turnable relative to the longitudinal axis of the chassis;

a rear wheel set having a left rear wheel and a right rear wheel, the left rear wheel being rotatably mounted to the left rear axle, the right rear wheel being rotatably mounted to the right rear axle, the left and right rear wheels being turnable relative to the longitudinal axis of the chassis;

a left front actuator operably coupled between the left front wheel and the left front axle exterior of the left front axle, the left front actuator being extendable and retractable relative to the chasis causing the left front wheel to turn relative to the longitudinal axis of the chassis;

a right front actuator operably coupled between the right front wheel and the right front axle exterior of the right front axle, the right front actuator being extendable and retractable relative to the chasis causing the right front wheel to turn relative to the longitudinal axis of the chassis;

a left rear actuator operably coupled between the left rear wheel and the left rear axle exterior of the left rear axle, the left rear actuator being extendable and retractable relative to the chasis causing the left rear wheel to turn relative to the longitudinal axis of the chassis; and

a right rear actuator operably coupled between the right rear wheel and the right rear axle exterior of the right rear axle, the right rear actuator being extendable and retractable relative to the chasis causing the right rear wheel to turn relative to the longitudinal axis of the chassis.

9. The mobile lift of claim 8 wherein:

the right front actuator is operably independent from the left front actuator; and

the right rear actuator is operably independent from the left rear actuator.

10. The mobile lift of claim 8 wherein:

extension of the left front actuator causes the left front wheel to turn in a first direction relative to the longitudinal axis of the chassis, and retraction of the left front actuator causes the left front wheel to turn in a second direction relative to the longitudinal axis of the chassis;

extension of the right front actuator causes the right front wheel to turn in the second direction relative to the longitudinal axis of the chassis, and retraction of the right front actuator causes the right front wheel to turn in the first direction relative to the longitudinal axis of the chassis;

extension of the left rear actuator causes the left rear wheel to turn in the second direction relative to the longitudinal axis of the chassis, and retraction of the left rear actuator causes the left rear wheel to turn in the first direction relative to the longitudinal axis of the chassis; and

extension of the right rear actuator causes the right rear wheel to turn in the first direction relative to the longitudinal axis of the chassis, and retraction of the right rear actuator causes the right rear wheel to turn in the second direction relative to the longitudinal axis of the chassis.

11. The mobile lift of claim 8 further comprising a microprocessor operably connected to the left front actuator and the right front actuator, the microprocessor being configured to cause the left and right front actuators to turn the left and right front wheels, respectively, non-parallel to each other when the front and rear wheels are turned in opposite directions relative to the longitudinal axis of the chassis.

12. The mobile lift of claim 8 further comprising a microprocessor operably connected to the left front actuator and the right front actuator, the microprocessor being configured to cause the left and right front actuators to turn the left and right front wheels, respectively, non-parallel to each other when the front wheels are turned relative to the longitudinal axis of the chassis and the rear wheels remain substantially parallel to the longitudinal axis of the chassis.

13. The mobile lift of claim 8 further comprising a microprocessor operably connected to the left front actuator and the right front actuator, the microprocessor being configured to cause the left and right front actuators to turn the left and right front wheels, respectively, at least substantially parallel to each other when the front and rear wheels are turned in the same direction relative to the longitudinal axis of the chassis.

14. The mobile lift of claim 8 further comprising:

a microprocessor operably connected to the left and right front actuators and the left and right rear actuators;

a directional switch operably connected to the microprocessor, the directional switch being movable to a full left position and to a full right position; and

a steering mode selection box operably connected to the microprocessor and adjustable to select between a front-wheel steer mode and a crab steer mode, selection of the front-wheel steer mode causing the microprocessor to turn the left and right front wheels non-parallel to each other in response to movement of the directional switch to the full left or full right positions, selection of the crab steer mode causing the microprocessor to turn the left and right front wheels at least substantially parallel to each other in response to movement of the joystick to the full left or full right positions.

15. A mobile lift having a true crab steering apparatus, the mobile lift comprising:

a lift assembly;

a chassis having a left portion and a right portion and a longitudinal axis, the lift assembly being mounted to the chassis;

a first left axle extensibly mounted to the left portion of the chassis and being moveable relative to the chassis between extended and retracted positions;

a first right axle extensibly mounted to the right portion of the chassis in axial alignment with the first left axle and being moveable relative to the chassis between extended and retracted positions;

a second left axle mounted to the left portion of the chassis;

a second right axle mounted to the right portion of the chassis in axial alignment with the second left axle;

a first wheel set having a first left wheel and a first right wheel, the first left wheel being rotatably mounted to the first left axle, the first right wheel being rotatably mounted to the first right axle, the first left and right wheels being turnable relative to the longitudinal axis of the chassis;

a second wheel set having a second left wheel and a second right wheel, the second left wheel being rotatably mounted to the second left axle, the second right wheel being rotatably mounted to the second right axle, the second left and right wheels being turnable relative to the longitudinal axis of the chassis;

a first left actuator operably coupled between the first left wheel and the first left axle, the first left actuator being extendable and retractable relative to the chasis causing the first left wheel to turn relative to the longitudinal axis of the chassis;

a first right actuator operably coupled between the first right wheel and the first right axle, the first right actuator being extendable and retractable relative to the chasis causing the first right wheel to turn relative to the longitudinal axis of the chassis, the first right actuator being operably independent from the first left actuator;

a second left actuator operably coupled between the second left wheel and the second left axle, the second left actuator being extendable and retractable relative to the chasis causing the second left wheel to turn relative to the longitudinal axis of the chassis;

a second right actuator operably coupled between the second right wheel and the second right axle, the second right actuator being extendable and retractable relative to the chasis causing the second right wheel to turn relative to the longitudinal axis of the chassis, the second right actuator being operably independent from the second left actuator; and

a control system operably connected to the first left and right actuators and the second left and right actuators, wherein the control system is adjustable between a two-wheel steer mode, an all-wheel steer mode, and a crab steer mode, in the two-wheel steer mode and the all-wheel steer mode, the first left and right wheels are non-parallel to each other when the first wheel set is turned relative to the longitudinal axis of the chassis, and in the crab steer mode, the first left and right wheels, and the second left and right wheels, are at least substantially parallel to each other when the first and second wheel sets are turned in the same direction relative to the longitudinal axis of the chassis.

16. The mobile lift of claim 15 further comprising:

a left sensor operably connected to the control system and positioned adjacent to the first left wheel, the left sensor being configured to measure a turn angle of the first left wheel relative to the longitudinal axis of the chassis; and

a right sensor operably connected to the control system and positioned adjacent to the first right wheel, the right sensor being configured to measure a turn angle of the first right wheel relative to the longitudinal axis of the chassis.

17. The mobile lift of claim 15 wherein:

the second left axle is extensibly mounted to the left portion of the chassis and moveable relative to the chassis between extended and retracted positions; and

the second right axle is extensibly mounted to the right portion of the chassis in axial alignment with the second left axle and moveable between extended and retracted positions.