Chassis cylinder for an industrial truck with a drive wheel pretensioned against the ground

Patent metadata

Field	Value
Publication number	US-12195071-B2
Application number	US-202217828180-A
Country	US
Kind code	B2
Filing date	May 31, 2022
Priority date	May 31, 2021
Publication date	Jan 14, 2025
Grant date	Jan 14, 2025

Abstract

An industrial truck includes a vehicle frame and a drive unit. The drive unit includes a drive wheel movably mounted to the vehicle frame and a spring unit. The spring unit includes a hydraulic cylinder positioned between the vehicle frame and the drive unit and a switchable valve configured to define a blocked state. The spring unit is configured to pretension the drive wheel against a ground surface. When the switchable valve is in the blocked state, a one-sided movement of the hydraulic cylinder is blocked.

First claim

The invention claimed is:

1. An industrial truck comprising:
a vehicle frame; and
a drive unit comprising,
a drive wheel movably mounted to the vehicle frame, and
a spring unit comprising,
a hydraulic cylinder positioned between the vehicle frame and the drive unit, and
a switchable valve configured to define a blocked state,

wherein the spring unit is configured to pretension the drive wheel against a ground surface, and wherein when the switchable valve is in the blocked state, a one-sided movement of the hydraulic cylinder is blocked,
wherein the hydraulic cylinder is configured as a dual-acting hydraulic cylinder defining a first piston chamber and a second piston chamber, and
wherein when the switchable valve is in the blocked state, a reduction of a volume in a blocked piston chamber is prevented and an enlargement of the volume in the blocked piston chamber is enabled.

2. An industrial truck comprising:
a vehicle frame; and
a drive unit comprising,
a drive wheel movably mounted to the vehicle frame, and
a spring unit comprising,
a hydraulic cylinder positioned between the vehicle frame and the drive unit, and
a switchable valve configured to define a blocked state,

wherein the spring unit is configured to pretension the drive wheel against a ground surface, and wherein when the switchable valve is in the blocked state, a one-sided movement of the hydraulic cylinder is blocked,
wherein the hydraulic cylinder is configured as a dual-acting hydraulic cylinder defining a first piston chamber and a second piston chamber, and
wherein a load-dependent system pressure is applied to at least one of the first and second piston chambers in at least a first operating state of the industrial truck.

3. The industrial truck according to claim 2 , further comprising a throttle unit configured to control a flow of fluid into or out of one of the first and second piston chambers to dampen movement of a corresponding hydraulic cylinder piston.

4. The industrial truck according to claim 3 , wherein the second piston chamber is connected to the first piston chamber by a connecting line, wherein the connecting line includes the throttle unit and the switchable valve.

5. The industrial truck according to claim 4 , further comprising a lift cylinder configured to lift a load lifting means, wherein a system pressure is applied to the first piston chamber.

6. The industrial truck according to claim 2 , wherein when the switchable valve is in the blocked state, a reduction of a volume in a blocked piston chamber is prevented and an enlargement of the volume in the blocked piston chamber is enabled.

7. The industrial truck according to claim 2 , wherein the blocked state of the switchable valve is opened in at least a second operating state of the vehicle.

8. The industrial truck according to claim 2 , wherein the first and second piston chambers define an area differential configured to generate a piston ejection force, wherein the piston ejection force generates a drive wheel load.

9. The industrial truck according to claim 2 , wherein the hydraulic cylinder further comprises a mechanically pretensioned spring element, wherein an initial stress of the mechanically pretensioned spring element contributes to a drive load, and wherein the mechanically pretensioned spring element is parallel-connected to the hydraulic cylinder.

10. The industrial truck according to claim 2 , further comprising at least one support roller operatively coupled to a support wheel spring, wherein a spring travel is determined by at least one of:
(1) a dip depth that can be traveled by the industrial truck, and
(2) a drive wheel pressure when navigating a curve.

11. The industrial truck according to claim 2 , further comprising at least two support rollers mounted on a common torsion bar, wherein the common torsion bar is configured to be connected to the vehicle frame in a pivotable and vertically sprung manner.

12. An industrial truck comprising:
a vehicle control;
a drive wheel; and
a spring unit operatively coupled to the drive wheel and comprising,
a hydraulic cylinder positioned between a vehicle frame and a drive unit, and
a switchable valve configured to be actuated by the vehicle control to define a blocked state,

wherein the hydraulic cylinder is configured as a dual-acting hydraulic cylinder defining a first piston chamber and a second piston chamber,
wherein a load-dependent system pressure is applied to at least one of the first and second piston chambers in at least a first operating state of the industrial truck, and
wherein the vehicle control is configured to open the switchable valve when the vehicle control recognizes a safe operating state,
wherein the safe operating state is recognized by at least one of a below conditions: (1) a steering angle of the industrial truck does not exceed a predetermined value for straight-ahead driving; and
(2) a lifting height of a load carrying means of the vehicle does not exceed a predetermined value of a transport height.

13. The industrial truck according to claim 12 , wherein the vehicle control is configured to open the switchable valve when at least one of a below conditions exist:
(1) the safe operating state lasts for a predetermined minimum period;
(2) a predetermined minimum distance has been traveled;
(3) a predetermined number of drive wheel rotations has been sensed by the vehicle control; and
(4) a predetermined speed has been undershot.

14. The industrial truck according to claim 12 , wherein the blocked state of the switchable valve is opened in at least a second operating state of the vehicle.

15. The industrial truck according to claim 12 , wherein the spring unit comprises a hydraulic cylinder configured as a dual-acting hydraulic cylinder and defining a first piston chamber and a second piston chamber.

16. The industrial truck according to claim 15 , wherein the first and second piston chambers of the hydraulic cylinder are connected to each other by the switchable valve.

Assignees

• Jungheinrich Ag

Inventors

• Schüler Michael
• Schwarz Richard
• Schefner Melanie
• Krenzin Marcel

Classifications

• B62B2301/23

  the pressure of the wheel on the ground being controlled, e.g. by the load or the wheel slip · CPC title

• B62B2301/08

  comprising additional wheels to increase stability · CPC title

• B62B2301/04

  comprising a wheel pivotable about a substantially vertical axis, e.g. swivelling castors · CPC title

• B66F9/22

  Hydraulic devices or systems · CPC title

• B60G2300/022

  Fork lift trucks, Clark · CPC title