Hydraulic cylinder position sensing and locking system and corresponding method

Patent metadata

Field	Value
Publication number	US-9568029-B2
Application number	US-201113995198-A
Country	US
Kind code	B2
Filing date	Dec 20, 2011
Priority date	Dec 22, 2010
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

The invention provides for a hydraulic cylinder position sensing and locking system that automatically maintains the position of a lock nut ( 36 ) that engages a plunger ( 16 ) on a hydraulic actuator such that if hydraulic pressure is lost, the lock nut prevents retraction of the plunger into the hydraulic cylinder ( 14 ). The hydraulic cylinder position sensing and locking system also provides for a position sensing feature that allows for the calculation of the axial stroke position of the plunger based on rotary movement of the lock nut. In addition, the invention provides for a synchronous hydraulic cylinder position sensing and locking system and methods of using both the hydraulic cylinder position sensing and locking system as well as the synchronous hydraulic cylinder position sensing and locking system.

First claim

What is claimed is:

1. A hydraulic cylinder position sensing and locking system, comprising:
a hydraulic actuator including:
a hydraulic cylinder; and
a plunger including a piston in the hydraulic cylinder and a threaded rod that extends axially from so as to move with the piston, the plunger being moveable axially relative to the cylinder in an extension direction and a retraction direction by selective supply of hydraulic fluid under pressure to the hydraulic cylinder;
a lock nut that rotatably engages the threaded rod with a threaded connection therebetween;
a drive unit that can be operated to rotate the lock nut relative to the plunger;
a distance sensor that outputs a distance signal that is indicative of the axial spacing of the lock nut relative to the hydraulic cylinder;
a rotary position sensor that provides a signal indicative of rotary position of the drive unit; and wherein the system determines the axial position of the plunger at least in part from the rotary position sensor signal, and
a controller that receives as an input the distance signal and outputs a control signal to control the drive unit so as to turn the lock nut in correspondence with the axial movement of the plunger so as to maintain the spacing of the lock nut relative to the hydraulic cylinder within a desired range.

2. The hydraulic cylinder position sensing and locking system of claim 1 , wherein the system determines the axial position of the plunger at least in part from the distance signal.

3. The hydraulic cylinder position sensing and locking system of claim 1 , wherein the system determines the axial position of the piston at least in part from the distance signal.

4. The hydraulic cylinder position sensing and locking system of claim 1 , wherein there is at least an additional hydraulic actuator and corresponding lock nut, drive unit, and distance sensor as claimed in claim 1 , and wherein each hydraulic actuator, drive unit, and distance sensor is connected to the controller and the controller determines the axial position of the plunger of each hydraulic actuator at least in part from a rotary position sensor signal output by the rotary position sensor of the corresponding hydraulic actuator and wherein the hydraulic actuators are operated in synchronization by the controller.

5. The hydraulic cylinder position sensing and locking system of claim 1 , wherein the desired range of the spacing of the lock nut relative to the hydraulic cylinder is about one millimeter to about six millimeters.

6. A method of locking and sensing the position of a hydraulic cylinder comprising the steps of:
providing a hydraulic actuator that includes: a hydraulic cylinder, and
a plunger including a piston in the hydraulic cylinder and a threaded rod that extends axially from the piston so as to move with the piston, the plunger being moveable axially relative to the cylinder in an extension direction and a retraction direction by selective supply of hydraulic fluid under pressure to the hydraulic cylinder;
providing a lock nut that rotatably engages the threaded rod with a threaded connection therebetween;
providing a drive unit that can be operated to rotate the lock nut relative to the plunger;
providing a distance sensor that outputs a distance signal that is indicative of the axial spacing of the lock nut relative to the hydraulic cylinder;
providing a controller that receives as an input the distance signal and outputs a control signal to control the drive unit;
programming the controller to provide the signal to control the drive unit such that the drive unit turns the lock nut in correspondence with the axial movement of the plunger so as to maintain the spacing of the lock nut relative to the hydraulic cylinder within a desired range, and
programming the controller such that before rotating the lock nut to unseat the lock nut, hydraulic fluid under pressure is introduced to the hydraulic cylinder to relieve friction on the lock nut that may prohibit rotating of the lock nut.

7. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , the method further comprising the steps of:
providing a rotary position sensor configured to provide a signal to the controller indicative of rotary position of the drive unit; and
programming the controller to determine the axial position of the plunger at least in part from the rotary position sensor signal.

8. The method of locking and sensing the position of a hydraulic cylinder of claim 7 , further comprising the step of:
programming the controller to determine the axial position of the plunger at least in part from the distance signal.

9. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , further comprising the step of:
programming the controller to determine the axial position of the plunger at least in part from the distance signal.

10. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , wherein the desired range of the spacing of the lock nut relative to the hydraulic cylinder is about one millimeter to about six millimeters.

11. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , further comprising the step of:
programming the controller such that upon a stoppage of movement of the plunger, the controller provides a signal to the drive unit such that the drive unit continues to turn the lock nut such that the lock nut seats against retraction of the plunger.

12. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , further comprising the step of:
programming the controller such that upon a stoppage of movement of the plunger, the controller provides a signal to the drive unit such that the drive unit turns the lock nut such that the lock nut is spaced a distance from the hydraulic cylinder, and the controller selectively supplies hydraulic fluid under pressure to the hydraulic cylinder to lower the plunger such that the lock nut seats against retraction of the plunger.

13. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , further comprising the step of:
programming the controller such that prior to any movement of the plunger in the retraction direction, the controller provides a signal to the drive unit such that the drive unit turns the lock nut such that the lock nut moves out of being seated against retraction of the plunger.

14. The method of locking and sensing the position of a hydraulic cylinder of claim 6 , wherein the drive unit includes a motor, a gear reduction unit, and a drive gear with teeth, and gear teeth on the lock nut, wherein the teeth on the drive gear mesh with gear teeth on the lock nut.

15. A synchronous hydraulic cylinder position sensing and locking system, comprising:
at least two hydraulic actuators, each hydraulic actuator including:
a hydraulic cylinder, and
a plunger including a piston in the hydraulic cylinder and a threaded rod that extends axially from so as to move with the piston, the plunger being moveable axial ly relative to the cylinder in an extension direction and a retraction direction by selective supply of hydraulic fluid under pressure to the hydraulic cylinder;
a corresponding lock nut for each hydraulic actuator that rotatably engages the threaded rod with a threaded connection therebetween;
a corresponding drive unit for each hydraulic actuator that can be operated to rotate the lock nut relative to the plunger;
a corresponding distance sensor for each hydraulic actuator that outputs a distance signal that is indicative of the axia

Assignees

• Lemke Austin R
• Wille Nathan A
• Actuant Corp

Inventors

• Lemke Austin R
• Wille Nathan A

Classifications

• F15B15/26 Primary

  Locking mechanisms · CPC title

• F15B15/261 Primary

  using positive interengagement, e.g. balls and grooves, for locking in the end positions · CPC title

• B66F3/30

  with positive brakes or locks · CPC title

• B66F3/46

  Combinations of several jacks with means for interrelating lifting or lowering movements · CPC title

• F16H2025/2081

  Parallel arrangement of drive motor to screw axis · CPC title