MATERIALS HANDLING VEHICLE MONITORING A PRESSURE OF HYDRAULIC FLUID WITHIN A HYDRAULIC STRUCTURE

• US 20140330488A1
• Filed: 07/17/2014
• Published: 11/06/2014
• Est. Priority Date: 02/16/2011
• Status: Active Grant

• Current Assignee: Crown Equipment Corporation
• Original Assignee: Crown Equipment Corporation
• Inventors: Dammeyer, Karl L., Holbrook, Eric D., Ihle, Darrin R., McClain, Marc A., Waltz, Lucas B.
• Granted Patent: US 9,394,151 B2
• Time in Patent Office: Days
• US Class Current: 701/50
• CPC Class Codes: B66F 17/003 for fork-lift trucks
• CPC Class Codes: B66F 9/07 Floor-to-roof stacking devices, e.g. "stacker cranes", "retrievers"
• CPC Class Codes: B66F 9/08 Masts; Guides; Chains
• CPC Class Codes: B66F 9/087 Monomasts
• CPC Class Codes: B66F 9/20 Means for actuating or controlling masts, platforms, or forks power take-off from vehicle transmissions, combined with vehicle propulsion systems B60K
• CPC Class Codes: B66F 9/205 Arrangements for transmitting pneumatic, hydraulic or electric power to movable parts or devices for cranes B66C13/12
• CPC Class Codes: B66F 9/22 Hydraulic devices or systems
• CPC Class Codes: B66F 9/24 Electrical devices or systems

Abstract

A materials handling vehicle is provided comprising: a support structure including a fixed member; a movable assembly coupled to the support structure; a hydraulic system; and a control system. The support structure further comprises lift apparatus to effect movement of the movable assembly relative to the support structure fixed member. The lift apparatus includes at least one ram/cylinder assembly. The hydraulic system includes a motor, a pump coupled to the motor to supply a pressurized fluid to the at least one ram/cylinder assembly, and at least one electronically controlled valve associated with the at least one ram/cylinder assembly. The control structure may estimate a speed of the movable assembly from a speed of the motor and control the operation of the at least one valve using the estimated movable assembly speed.

Claims

1. A materials handling vehicle comprising:

a support structure including a fixed member;

a movable assembly coupled to said support structure;

said support structure further comprising lift apparatus to effect movement of said movable assembly relative to said support structure fixed member, said lift apparatus including hydraulic structure comprising at least one ram/cylinder assembly, at least one hydraulic fluid line in communication with said at least one ram/cylinder assembly, and a hydraulic system that supplies a pressurized fluid to said at least one ram/cylinder assembly via said at least one hydraulic fluid line; and

control structure to monitor a pressure of the pressurized fluid within said hydraulic structure and to implement a response routine if the monitored pressure of the pressurized fluid within said hydraulic structure falls below a threshold pressure.

2. The materials handling vehicle as set forth in claim 1, wherein the threshold pressure is dependent upon at least one of a maximum lift height of said movable assembly and a weight of a load supported by said support structure.

3. The materials handling vehicle as set forth in claim 2, wherein the threshold pressure is calculated by the following equation:

T_P (psi)=[A (psi/pound)*Load (pounds)]/100(unitless)+[(Height (inches)*100 (unitless)]/B (inches/psi)

wherein T_P is the threshold pressure, A is a constant, Load is the weight of a load supported on said support structure, 100 is a unitless scaling factor, Height is the maximum lift height of said movable assembly, 100 is a unitless scaling factor, and B is a constant.

4. The materials handling vehicle as set forth in claim 1, wherein said control structure only implements the response routine if said support structure is determined to be lowering at a speed equal to or above a predetermined speed.

5. The materials handling vehicle as set forth in claim 1, wherein the response routine comprises the control structure controlling operation of at least one electronically controlled valve associated with said at least one ram/cylinder assembly to control lowering of said support structure.

6. The materials handling vehicle as set forth in claim 5, wherein said control structure further:

estimates a speed of said movable assembly from a speed of a motor that is functional to supply the pressurized fluid to said at least one ram/cylinder assembly; and

controls the operation of said at least one valve using a comparison of the estimated movable assembly speed to a determined movable assembly speed.

7. The materials handling vehicle as set out in claim 6, wherein said control structure is capable of energizing said at least one valve so as to open said at least one valve to permit said movable assembly to be lowered in a controlled manner to a desired position relative to said support structure fixed member.

8. The materials handling vehicle as set forth in claim 7, wherein said control structure de-energizes said at least one valve in response to an operator-generated command to cease further descent of said movable assembly relative to said support structure fixed member.

9. The materials handling vehicle as set forth in claim 8, wherein said at least one valve functions as a check valve when de-energized so as to block pressurized fluid from flowing out of said at least one ram/cylinder assembly, and allows pressurized fluid to flow into said at least one ram/cylinder assembly during a movable assembly lift operation.

10. The materials handling vehicle as set forth in claim 6, wherein

said support structure further comprises a power unit;

said support structure fixed member comprises a fixed first mast weldment coupled to said power unit;

said lift apparatus further comprises;

a second mast weldment movable relative to said first mast weldment; and

a third mast weldment movable relative to said first and second mast weldments;

said at least one ram/cylinder assembly further comprises;

at least one first ram/cylinder assembly coupled between said first and second mast weldments for effecting movement of said second and third mast weldments relative to said first mast weldment; and

a second ram/cylinder assembly coupled between said third mast weldment and said movable assembly so as to effect movement of said movable assembly relative to said third mast weldment; and

said at least one electronically controlled valve comprises;

at least one first solenoid-operated, normally closed, proportional valve associated with said at least one first ram/cylinder assembly; and

a second solenoid-operated, normally closed, proportional valve associated with said second ram/cylinder assembly.

11. The materials handling vehicle as set forth in claim 10, wherein said control structure comprises:

encoder apparatus associated with said movable assembly for generating encoder pulses as said movable assembly moves relative to said first mast weldment; and

a controller coupled to said encoder apparatus and said valves for receiving said encoder pulses generated by said encoder apparatus, and determining the determined movable assembly speed based on the encoder pulses.

12. The materials handling vehicle as set out in claim 11, wherein said control structure controls the operation of said at least one first valve and said second valve by comparing the determined movable assembly speed with at least one of:

a first threshold speed based on the estimated movable assembly speed; and

the first threshold speed and a fixed, second threshold speed.

13. The materials handling vehicle as set out in claim 12, wherein said controller functions to de-energize said at least one first valve and said second valve causing them to move from their powered open state to their closed state in the event said movable assembly moves downwardly at the determined movable assembly speed in excess of one of the first and second threshold speeds.

14. The materials handling vehicle as set forth in claim 13, wherein said controller slowly closes said at least one first valve and said second valve in the event said movable assembly moves downwardly at a speed in excess of said first or said second threshold speed.

15. The materials handling vehicle as set forth in claim 14, wherein said controller causes said at least one first valve and said second valve to move from their powered open position to their closed position over a time period of from about 0.3 second to about 1.0 second.

16. The materials handling vehicle as set forth in claim 6, wherein said control structure estimates the movable assembly speed from the motor speed by:

converting motor speed into a pump fluid flow rate, the pump being coupled to said motor, converting the pump fluid flow rate into a ram speed and converting the ram speed into the estimated movable assembly speed.

17. The materials handling vehicle as set forth in claim 5, wherein said at least one valve comprises a solenoid-operated, normally closed, proportional valve.

18. The materials handling vehicle as set forth in claim 5, wherein said at least one valve is positioned in a base of said at least one ram/cylinder assembly.

19. The materials handling vehicle as set forth in claim 6, wherein said motor receives power from a battery for driving a pump coupled to said motor for supplying the pressurized fluid to said at least one ram/cylinder assembly.

20. The materials handling vehicle as set forth in claim 1, wherein said fixed member comprises a fixed mast weldment coupled to a power unit.

21. The materials handling vehicle as set forth in claim 1, wherein said lift apparatus further comprises at least one movable mast weldment and said movable assembly comprises a fork carriage assembly which moves relative to said support structure fixed member.

22. The materials handling vehicle as set forth in claim 1, wherein said control structure further:

estimates a speed of said movable assembly from a speed of a motor that supplies the pressurized fluid to said at least one ram/cylinder assembly, the motor being coupled to a pump; and

calculates an updated pump volumetric efficiency using the estimated movable assembly speed and a determined movable assembly speed.

23. The materials handling vehicle as set forth in claim 22, wherein said control structure determines the updated pump volumetric efficiency using the following equation:

updated pump volumetric efficiency=(determined movable assembly speed*current pump volumetric efficiency)/estimated movable assembly speed.

24. The materials handling vehicle as set forth in claim 23, wherein the current pump volumetric efficiency is derived based on one or more of a speed of the materials handling vehicle, a direction of rotation of the pump, and a pressure, a temperature, and/or a viscosity of the pressurized fluid.

25. The materials handling vehicle as set forth in claim 1, wherein said control structure further measures an electric current flow into or out of a motor that supplies the pressurized fluid to said at least one ram/cylinder assembly and reduces an operating speed of said motor if the electric current flow into or out of said motor is greater than or equal to a predetermined threshold value.