JPH04258537A - Gas spring having thermally compensated holding force - Google Patents

Abstract

PURPOSE: To retain an always uniform retaining force in a gas spring having a seal unit with a piston dividing a working chamber into two by constructing a retaining device for engagement with the piston from a retaining clamp having an E-module that decreases with temperature. CONSTITUTION: A piston 3 integrated with a piston rod 2 is fitted into a working chamber 5 made of a pressure pipe 4 filled with a buffer medium, and a piston rod guide 6 through which the piston rod 2 extends and a piston rod seal 7 are provided at the end of the pressure pipe 4. In this case, an elastic retaining clamp 8 is assembled between the piston rod seal 7 and a support ring 12. The retaining clamp 8 has an annular web 9, and a locking element 11 for engagement with the hollow throat 13 of the piston rod 2 is provided at the end of an elastic finger 10 connected to the annular web 9. The retaining clamp 8 is designed to decrease its retaining force as its E-module drops with the rise of operating temperature.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION The invention consists of a pressure pipe and a sealing unit having a piston which is arranged in a piston rod guide and which seals an invading piston rod and divides a working chamber filled with a buffer medium into two parts. The present invention relates to a gas spring of the type in which a temperature-relevant retaining device of the pistons which engages one another in a positive manner is arranged in the working chamber.

0002

BACKGROUND OF THE INVENTION All gas springs have the common drawback that their evacuation force is strong and temperature related. The temperature range required to use a gas spring is -40℃
and +80°C. The holding force of the gas spring is set to ensure full functionality even at -40°C. If the ratio of maximum pressure to minimum pressure is approximately 1:4, the pressure in the working chamber fluctuates correspondingly strongly. The force consumed by the use of the gas spring to bring it into the retracted position is inversely proportional to said factor. When using gas springs as force supports for vehicle dampers, the driver has to generate a closing force. Slightly reduce gas pressure to reduce hand force at high temperatures;
It is also known to use additional retaining devices in the gas spring that ensure functional safety. DE 27 06 884 A1 shows a retaining device which is fixedly integrated in the piston and locks in an annular groove in the cylinder wall. The disadvantage of such a configuration is that when the operating temperature increases, the clamping action between the holding chamber and the cylinder wall increases, and this causes the spatial expansion of the holding chamber to be greater than the expansion of the cylinder wall. So the power consumed by the consumer is related to the operating temperature.

0003

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas spring which provides an extremely uniform holding force over the entire temperature range.

0004

SUMMARY OF THE INVENTION The measures of the invention taken to solve the aforementioned problem consist in that the holding device has a holding clamp with an E-module that decreases with increasing temperature. .

[0005]

The piston rod, which enters the working chamber filled with pressure medium, has a hollow throat on the upper side of the piston. A resilient retaining clamp is provided axially sealed between the piston rod seal and the support ring. The retaining clamp uses a plurality of finger-like protrusions with a stop that engages the hollow throat of the piston rod. At high operating temperatures, the holding clamp behaves such that the E-module of the material decreases. As a result, the holding force of the device can be adapted to the respective operating conditions and the gas pressure in the working chamber can be reduced compared to the gas pressure of conventional gas springs. Another functional advantage is that the retaining clamp expands under the influence of heat and this reduces the frictional forces on the piston rod. By selecting the plastic properties, the holding device is advantageously adapted to the holding force required when using the same gas spring.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a sectional view of a gas spring 1 without a fixing device for the gas spring. A piston rod 2 with a piston 3 can be moved in the axial direction in a working chamber 5 formed by a pressure tube 4, which is filled with a damping medium. The piston rod guide 6 allows for a centered position of the piston rod 2. A piston rod seal 7 closes the working chamber 5 in the piston rod guide 6. An elastic retaining clamp 8 is installed between the piston rod seal 7 and the support ring 12. The holding clamp 8 has an annular web 9 which takes care of centering and transmits the forces occurring during load bearing to the support ring 12. Connected to the annular web 9 is an elastic finger 10 which has a stop 11 at its end, which stops at the hollow throat 13 of the piston rod 2.
Combine shape with. During the stroke movement of the piston rod 2, the locking body 11 is located on the piston rod 2. The finger 10 is easily expanded at the finger projection. Upon reaching the starting position, a form-locking of the holding device is carried out and care is taken to securely hold the load.

The entire unit consisting of the piston rod guide 6, the piston rod seal 7, the retaining clamp 8 and the support ring has a flange 15 and a recess 1 in the pressure tube 4.
4.

[0008] When the operating temperature increases, the E-module of the elastic holding clamp 8 decreases, thereby reducing the holding force. As a result, the holding force of the gas spring is
The predetermined extreme positions of maximum push-in and maximum push-out are approximately the same, and compensation for the high gas forces is thereby obtained by the decreasing force of the holding device.

The use of different plastics for the retaining clamp 8 allows the retaining device to be adapted to the load without changing the overall structure of the gas spring.

Suitable materials are thermoplastics, such as POM, which, in addition to a reduced E-module, has a low coefficient of friction, which means that the locking body 1
This works advantageously when the piston rod 1 contacts the piston rod 2.

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of a gas spring of the present invention.

[Explanation of symbols]

Claims (7)

[Claims] 1. Consists of a pressure pipe and a sealing unit having a piston, which is arranged in a piston rod guide and seals the invading piston rod and divides a working chamber filled with a buffer medium into two parts, the piston Gas springs of the type in which a temperature-related holding device in positive engagement with one another is arranged in the working chamber, said holding device having an E-module that decreases with increasing temperature (8); Gas spring with thermally compensated holding force, characterized in that it has: 2. Gas spring according to claim 1, wherein the retaining clamp (8) is made of thermoplastic. 3. Gas spring according to claim 1, wherein the positive connection of the holding device consists of an elastic holding clamp (8) and a specially designed region of the piston rod (2). 4. Any one of claims 1 to 3, wherein the piston rod (2) has a hollow throat (13).
Gas springs listed. 5. Gas spring according to claim 1, wherein the holding clamp (8) has a radially inwardly directed stop (11). 6. Gas spring according to claim 1, wherein the retaining clamp (8) has a radially outwardly directed annular web (9). 7. Gas spring according to claim 1, characterized in that the holding clamp (8) is held between the piston rod seal (7) and the support ring (12).