US20030024382A1

US20030024382A1 - Lock-up device

Info

Publication number: US20030024382A1
Application number: US10/201,539
Authority: US
Inventors: Martin Gram
Original assignee: MTS Systems Corp
Current assignee: MTS Systems Corp
Priority date: 2001-07-25
Filing date: 2002-07-23
Publication date: 2003-02-06

Abstract

A device, preferably hydraulic, is connectable to a first body and a second body selectively forming a rigid connection therebetween or allowing relative motion. The device includes a cylinder having a chamber. The cylinder is connectable to one of the bodies. A piston rod is connectable to the other body. A tension rod has a piston slidable in the chamber and is coupled to the piston rod for slidable movement relative thereto. A second piston is slidable in the chamber and slidable relative to the tension rod.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 60/307,802, filed Jul. 25, 2001, the content of which is hereby incorporated by reference in its entirety.[0001]

BACKGROUND OF THE INVENTION

The present invention relates to fluid devices. More particularly, the present invention relates to a device that can selectively form a rigid connection between two bodies, or be operated such that movement of the bodies can freely take place.

SUMMARY OF THE INVENTION

One aspect of the present invention is a device, preferably hydraulic, that is connectable to a first body and a second body selectively forming a rigid connection therebetween or allowing relative motion. The device includes a cylinder having a chamber. The cylinder is connectable to one of the bodies. A piston rod is connectable to the other body. A tension rod has a piston slidable in the chamber and is coupled to the piston rod for slidable movement relative thereto. A second piston is slidable in the chamber and slidable relative to the tension rod. Additional aspects include features like a port formed in the piston rod and passageway in the tension rod fluidly coupling the chamber to the port, and means for adjusting the length to achieve a desired lock-up force in combination with some or all of the aforementioned elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a lock-up device of the present invention. [0004]
FIG. 2 is a side elevational view of the lock-up device. [0005]
FIG. 3 is a side elevational view of an exemplary swivel assembly.[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a lock-up [0007] device 10 includes a first end 12 (e.g. herein a rod and swivel assembly 14) connectable to a first body (not shown) and a second end 16 (e.g. herein also embodied as a swivel assembly 14) connectable to a second body (not shown). As illustrated, the lock-up device 10 includes a piston rod 20 connected to the first end 12 and a cylinder 22 connected to the second end 16. An end 24 of the piston rod 20 remote from the first end 12 is slidably coupled to a tension rod 26 having a tension piston 28 slidable in the cylinder 22. A floating piston 30 is also present in the cylinder 22 and slides relative to the tension rod 26.
Generally, fluid pressure provided in the [0008] cylinder 22 between the tension piston 28 and the floating piston 30 maintains the device 10 in a “lock-up” state such that the device 10 can accept and transmit tension and compression forces between the first end 12 and the second end 16. In the embodiment illustrated, a port 34 is fluidly coupled to an inner chamber 36 of the piston rod 20, that in turn, is coupled to a fluid passage 38 in the tension rod 26, which opens to the chamber of the cylinder 22 between the floating piston 30 and the tension piston 28. A valve 44 is coupled to the port 34 to selectively provide fluid thereto from a source 46. A reservoir 48 receives fluid from the valve 44. To release pressure, the valve 44 can be a relief valve in order to provide a controlled force. In another embodiment, valve 44 can comprise a solenoid valve to provide immediate pressure release. A vent 50 is also provided. In an alternative embodiment, the valve 44 can be fluidly coupled both to the port 34 illustrated and an additional port opening to the chamber formed in the cylinder 22 between the floating piston 30 and the tension piston 28.
Operation of the [0009] device 10 is provided below. When pressure is released and fluid is allowed out through the port(s) 34, the first end 12 can move relative to the second end 16. In particular, FIG. 1 illustrates a “middle” position, which corresponds to the “lock-up” position when fluid pressure is applied. Without fluid pressure, the tension piston 28 of the tension rod 26 can move relative to the cylinder 22, which in turn, allows the first end 12 to extend away from the second end 16. In contrast, under certain loading, the second end 16 may want to reposition itself closer to the first end 12. In this manner, forces upon the piston rod 20 will allow the piston rod 20 and the floating piston 30 to move relative to the cylinder 22.
In the locked position, high stiffness can be critical. In order to achieve high stiffness, it is necessary to develop a high contact force on the floating [0010] piston 30 to the piston rod 20 and to the inner shoulder 31 of cylinder 22. To achieve the high contact force on both surfaces, a high contact force between the tension rod 26, 28 and the lower end cap 33 is helpful. This can be accomplished and a proper preload can be obtained by holding tight tolerances on the lengths of the components. Alternately, an adjustment mechanism of the preload is possible. For instance, the end cap 33 could be rotated on the screw threads of the cylinder 22 and then locked in position when the proper adjustment is achieved. This can eliminate any gap between inner shoulder 31 and floating piston 30.
FIG. 3 is an enlarged view of an [0011] exemplary swivel assembly 14. The swivel assembly 14 includes a swivel pin 60 held in position with a cap 62. Fasteners connect the swivel pin 60 to each of the bodies. The fastener 64 includes an anchor 66, spiral washers 68 and shim washers 70, as required in order to achieve the desired lock-up force. This means for adjusting the length could be located on either or both ends of the device 10.
The description provided above is but one example of the hydraulic lock-up device of the present invention. It should be noted that various changes such as different dimensions, operating pressures and elements can be made to the device without departing from the invention concept. [0012]
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. [0013]

Claims

What is claimed is:

1. A lock-up device comprising:

a cylinder having a chamber, the cylinder being connectable to one of the bodies;

a piston rod connectable to the other body; a tension rod having a piston slidable in the chamber and coupled to the piston rod for slidable movement relative thereto; and

a piston slidable in the chamber and slidable relative to the tension rod. Additional aspects include features like a port formed in the piston rod and passageway in the tension rod fluidly coupling the chamber to the port, and means for adjusting the length to achieve a desired lock-up force in combination with some or all of the aforementioned elements.