Brakes – Internal-resistance motion retarder – Resistance alters relative to direction of thrust member
Reexamination Certificate
1998-07-29
2001-01-30
Oberleitner, Robert J. (Department: 3613)
Brakes
Internal-resistance motion retarder
Resistance alters relative to direction of thrust member
C188S322150, C267S064150
Reexamination Certificate
active
06179100
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention concerns a bidirectionally blockable piston-cylinder unit which includes a throttle arrangement to control fluid flow therethrough so as to minimize noise upon switching between opened and closed positions.
2. The Prior Art
A positional piston-cylinder unit to lock movable objects in relative positions to each other is known from DE 4,326,968 A1. Such positional locks are used, among others, in the case of vehicle doors or lids, which on the one hand, should be easily manipulated, but, on the other hand, should also safely carry the respective load. One of the advantages of a piston-cylinder lock according to DE 4,326,968 A1 is that it is possible to make the retaining function independent of the stroke. Other types of units allow the retaining function to occur only within a specific opening range of the vehicle door or lid, or else only in predetermined fixed resting steps.
One of the problems of a unit capable of being blocked in infinite steps is the noticeable switching noise. This type of noise did not occur in the case of earlier, defined blocking position types of piston-cylinder units, and is detrimental to comfort.
SUMMARY OF THE INVENTION
The object of the present invention is to further develop a piston-cylinder unit in a manner such that the noise problems known from prior art units are solved. Furthermore, the actuating force should be as constant as possible.
According to the invention, the foregoing objects are achieved by the provision of a throttle arrangement between two individual closing valves, which throttle arrangement produces a reduction in pressure between the valve outflow side of the first closing valve towards the valve inflow side of the following, second closing valve. The effect of the throttle arrangement decreases with the increasing degree of opening of the first closing valve, and to the same extent the pressurization of the second closing valve increases on the valve inflow side. The purpose is to produce a controlled coordination of the dynamic pressure between the individual valves, so that there will occur no pressure peaks which might lead to drastic motions of the valve, which motions in turn will be unpleasantly audible as noise.
In a further embodiment, the first closing valve includes a valve-closing body which abuts in the opening direction against a retaining surface of a slide, which slide in turn is operationally connected with a second valve-closing body in a manner such that an opening motion of the first valve-closing body is transferred to the second valve-closing body. In practice, the closing valves are also mechanically arranged in order, inasmuch as they all open in the same direction. Consequently, a somewhat extended sealing range can be provided for the second closing valve, so that the operating behavior of the entire valve arrangement will be less sensitive to tolerances in length.
One thus achieves the advantageous possibility of connecting a throttle arrangement after the outflow side of the second closing valve. There occurs a controlled pressure drop minimizing possible noise, since once again there is no sudden opening of the second closing valve with a 0/1 characteristic.
In a preferred embodiment, the first valve-closing body is made up of a valve ring arranged in a valve sleeve in an axially movable manner. The valve ring represents in its function a sliding valve. An ordinary O-ring may be used as a valve ring. Furthermore, the valve sleeve comprises the path-dependent effective throttle arrangement which is controlled by the valve-closing body. Here, the throttle arrangement is made between the first and the following closing valve by at least one groove in the valve sleeve. One can use several grooves of differing lengths, so that a continuous pressure drop can be achieved.
As concerns the universal usability of the piston-cylinder unit, the valve arrangement provides two flow-through directions and is designed so that each is blockable. For example, in the case of a vehicle whose trunk lid must always be open because of a protruding load, the bi-directional blocking function of the invention obviates the need for an additional securing measure. Here, the first closing valve is also used for both flow-through directions.
In order to limit assembly effort/expenses, the piston is designed as a tubular body in which there is arranged at least one slide. An end member is fixed to at least at one end of the tubular body so that the piston represents a previously assemblable component. The slide guided within the tubular body does not undergo any crosswise stress due to mechanical loads; consequently, a low-friction motion is possible.
It is advantageous to design the valve-closing body of the second closing valve as a radially elastic annular body which operates in conjunction with a cylindrical valve-seat surface. The valve-seating surface for the open switching position features a diameter which is different from that of the valve-seating surface for the blocked switching position. Thus, the valve-closing body is supported in an axially floating manner and is moved between the valve-seating surfaces as a function of forces acting on it.
In order to ensure an unimpeded motion of the slide, the slide is moved within the fluid connection between the first and the second closing valves, whereby the magnitude of the fluid connection changes. The fluid connection includes at least one pressure-equalizing connection which is controlled (switched) by a check valve.
Thus, the second valve-closing body forms the check valve for the fluid connection in that a flow connection between the adjacent working space and the fluid connection is controlled via the axial mobility of the valve-closing body. Consequently, no undesired suction may occur in the fluid connection.
In addition, the piston may include a piston ring which separates the two working chambers from each other. The piston ring is designed to be elastic and to be partially deformable in a crosswise direction, whereby one controls a dynamic-pressure connection between the fluid connection and the working space with the lower momentary pressure. In this manner, one can also lower in a controlled way any dynamic pressure in the fluid connection, so as not to impede the motion of the slide in the direction of entering the fluid connection.
In a preferred structural embodiment, the piston ring is guided within a piston-ring groove which includes pockets in the range of the dynamic-pressure connections, the piston ring being adapted to deform into the pockets under pressure. The piston ring is guided securely within the piston-ring groove. The pockets limit the deformation in the crosswise direction, so that sealing is achieved and fatigue of the material is minimized.
In the case of blockable piston-cylinder units, one must weigh what consequences may arise if the blockage cannot be overcome, say in the case of an accident. In the case of a vehicle trunk lid or hood, no special danger possibilities need to be considered. If, however, a lateral door is equipped with a piston-cylinder unit according to the invention, it is of particular advantage if the piston is fastened to the piston rod via at least one releasable retaining element. In the case of application of a force exceeding a normal actuating force, the retaining element may thereby be released and the blocking effect of the valve arrangement canceled. The retaining element thus represents a designated point of release.
It can be quite useful to fasten the piston to the piston rod by two such retaining elements, where one retaining element features a higher maximum retaining force than the other. Thus, one can provide that the retaining element which, in the opening direction of a door, absorbs the blocking forces of the piston is designed to be weaker than the other retaining element, so that in case of an accident, a vehicle door can be opened, albeit with significant effort.
In another advantageous embodiment, a damping arrangement acts on the s
Gehlen Marco
Mintgen Rolf
Rennecke Dirk
Ritter Andreas
Rothe Wolfgang
Baker & Botts L.L.P.
Oberleitner Robert J.
Stabilus GmbH
Williams Thomas J.
LandOfFree
Blockable piston-cylinder unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Blockable piston-cylinder unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Blockable piston-cylinder unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469313