DAMPER

Subject of Invention

The subject of the present invention is a one-way hydraulic or pneumatic damper of motion of items, preferably furniture items, especially door wings, said damper comprising a cylindrical housing closed at one end, in which a piston rod with a piston and a valve portion for the control of a medium flow within a damper, and a compression spring are arranged.

Technical Problem

The technical problem of the present invention is how to conceive such motion damper that would have a simple and economical design and would be adequate for mass and automated production by simultaneously meeting the requirements for a quality two-way motion damping.

Prior Art

FR 63.679 (Peignen) discloses a door damper having a two-stage piston rod arranged within a hydraulic cylinder. A piston is fastened by a nut and discs to said piston rod, said piston separating the interior of the hydraulic cylinder into two closed chambers, comprising an active medium, like oil. The external diameter of the piston is somewhat smaller than the interior diameter of the cylinder in order to allow outflow of oil from one chamber into another while the piston moves due to an external force exerted on the piston rod. The piston is centred on the piston rod, which reaches into the central recess of the piston with its free threaded end. A valve portion for the regulation of damping is embedded within the piston. To meet this purpose, conduits are arranged in radial direction within said piston. Each conduit leads with one end to a shaped groove arranged on the external circumference of the piston and with the other end to the central recess of the piston. An O-ring is located within the groove. The width of the groove is larger than the width/thickness of the O-ring, so the O-ring may

move within the groove in direction parallel to the main axis of the cylinder. The direction of movement of the O-ring depends on the direction of force exerted on the piston rod. Due to an increased pressure within an individual chamber, the O-ring within the groove gets displaced to a certain side, thus opening or closing the openings j of radial .conduits. When the openings of conduits are open, the oil flow is more significant and consequently damping less significant.

JP 3-125043 describes a pneumatic damper, wherein the action of the valve embedded within a piston of the damper is controlled by an O-ring. The piston rod and the piston are uniform, wherein said piston is formed into a hollow cylindrical element provided with two mutually spaced circumferentially extending attachments forming type of groove. In direction rectengularly to this groove the piston comprises in direction of the main axis a specially shaped groove of a changing width and opened at one side to the cylinder chamber. Within the piston groove there is a movable O-ring arranged. The O-ring moves within said groove in axial direction as a function of direction from which external force is exerted. It partially closes a specially shaped groove, herewith increasing / decreasing the flow of a medium past the piston and thus determining the scope of damping in the operating / return movement.

A disadvantage of the solutions described hereinbefore lies in that numerous high precision work operations are needed in the production of such product, especially in the manufacturing of grooves and conduits, which is very difficult to achieve in mass production and is not acceptable from the economical point of view. By using standard O-rings having a quite wide measuring tolerance field it is very difficult to ensure a certain clearance for the outflow of the medium in order to provide for a certain level of damping. The increase in the reliability of operation within a narrow field calls for O-rings manufactured in a narrower tolerance field or for an introduction of an additional control as to dimensions, which is, however, not acceptable for the products

of this type. Further, the implementation of a two-stage piston rod is also problematic, especially because the end with the piston must be even threaded. The requirements for tolerance of the valve and piston part are very high due to the mode of operation, which is extremely difficult to be achieved in case of a large number of constituent parts.

The disadvantages of imprecise operation as a consequence of the valve being controlled by O-rings are done away with in DE 1 809 854, where damping is achieved by way of longitudinal grooves having a changing cross-section arranged on the internal circumference of the cylinder. Some damping during return movement is achieved by a valve part having a valve disk adapted in its form to the piston rod and a ring valve seat arranged on the piston and with a conduit arranged near the piston rod. During a work stroke a valve disk abuts with a ring seal upon the valve seat thus closing the conduit at the piston rod. A compression spring that returns the piston rod to its initial position is arranged on the piston rod in a way to abut with its piston-side end upon special attachments spaced from the piston. During a return stroke first the piston rod with the valve disk and the ring seal move away from the valve seat on the piston. The conduit at the piston rod thus opens and the medium can flow therethrough into the adjacent space having a lower pressure. Only when the plugs with the compression spring abut upon the piston, the latter moves as well. Damping in return i stroke is less considerable. The damper of the described type comprises demanding constituent parts that need to be manufactured with high precision on high precision machines. The manufacturing of the piston rod is utterly problematic, it is namely a multi-stage piston rod with additional elements arranged thereon that enable the valve to move away.

Solution to the Technical Problem

I i

The described technical problem is solved by a hydraulic or pneumatic damper of the invention, preferably a one-sided damper formed in a cylindrical housing closed at one

end, wherein the requirement for damping from two sides is solved by a piston rod, a piston with, a valve part and a ring seal arranged thereon within a circumferential groove, all elements being axially arranged. The piston rod formed as a straight rod of a constant cross-section engages with a centrally arranged blind hole on the valve part of, the piston and therewith forms a separable engagement, wherein the front side of the piston rod abuts upon the bottom of the blind hole. The cross-section of the blind hole of the piston exceeds the surface of the cross-section of the piston rod in a way that a formed conduit is formed between the piston and the piston rod serving for the work medium to flow from one chamber into another. The size of difference of cross- sections is determined by the size of the external force exerted on the damper and the required level of damping connected therewith.

On the circumference of the piston there is a circumferential groove to receive a ring seal to delimit the flow of the medium between the piston and the housing and at least one groove arranged transversally to the circumferential groove in axial direction towards each piston end for the flow of the medium from one chamber into another. The internal diameter of the ring seal exceeds the internal diameter of the circumferential groove and the ring seal moves in axial direction due to the movement of the medium as a consequence of a different pressure within each chamber thus closing and opening each longitudinal conduit extending towards the cover-end of the piston.

Reliable and high-quality two-sided variable damping in the damper of the invention is achieved by merely using three component parts that do not need any additional connecting parts for mutual connection and operation. Moreover, no precise mechanical processing with expensive and demanding machines is needed for the manufacturing of each constituent part. To the contrary, two out of the three constituent parts, i.e. the piston rod and the ring seal, are standard elements and do not need any further processing.

Since axially designed, the damper of the invention is also adequate for automatic assembly on assembly lines, which still further contributes to the simplicity and economic efficiency of the damper.

The invention will now be described in more detail by way of an embodiment and enclosed drawings, showing in:

Fig. 1 longitudinal cross-section of the damper, first embodiment of the invention Fig. 2 longitudinal cross-section of the damper piston, second embodiment of the invention

A one-sided hydraulic or pneumatic damper 1 of the invention comprises a cylindrical housing 2 closed at one end, in which a piston rod 3 is arranged in direction of the main axis, said piston rod 3 protruding through a cover 5 closing the other end of said housing 1 and having on its other end that reaches into said housing a piston 4 with a valve part as a constituent part. Said cover 5 closes said cylindrical housing 2 and is provided with a central through hole 6 running through an integrally formed attachment 7 that reaches into the interior of the cylinder and functions as a guide for said piston rod 3. Said piston rod 3 is sealed at the cover by a seal 8 of the piston rod. Within said housing 2, between its closed end and said piston 4 there is further a compression spring 9 that returns said piston 4 with said piston rod 3 to initial position. Said attachment 7 has a built-in elastic element 20 that equalises the changes in volumes of both chambers by changing its own volume.

Said piston rod 3 is formed as a straight rod of a constant cross-section, wherein the shape of the cross-section of the piston rod is adapted to the needs of further installation of the damper, preferably of a round cross-section.

Said piston 4 divides the interior of the cylinder into two chambers linked by at least one conduit running in longitudinal substantially axial direction. Said uniform piston 4 has an opening 12 extending transversally to the longitudinal axis of the damper, in the embodiment a through hole, and separating said piston into a piston portion 13 and a valve portion 14. The valve portion 14 houses a central hole 15, into which said piston rod 3 engages, the latter abutting with its front side upon said piston portion 13. Said piston rod 3 engages with said hole 15 of said valve portion 14, in the embodiment loosely engages. The cross-section of said hole 15 of said valve portion 14 exceeds the cross-section of said piston rod 3 in a way that a formed piston rod-side conduit 16 is formed between said valve portion 14 and said piston rod 3, said conduit serving as a canal for the work medium, in the embodiment oil, to pass from one chamber into another. The size of the difference in cross-sections is determined by the size of the external force exerted on the damper and the required magnitude of damping linked therewith.

Said valve portion 14 has a circumferential groove 17 arranged radially on the circumference. At least one first groove 10 runs rectangularly to said circumferential groove 17 and in axial direction towards said piston portion 13, said first groove 10 continuing in said piston portion and allowing the oil to pass past said piston portion 13; and at least one second groove 11 runs in axial direction towards said cover 5 to allow outflow of oil to another chamber. Said grooves 10, 11 are mutually not directly connected.

Within said circumferential groove 17 there is an annular seal 18, preferably an O-ring, wherein its internal diameter exceeds the internal diameter of said circumferential groove 17, in order to allow free movement of said O-ring in axial direction. The direction of movement of said O-ring 18 is determined by the direction of oil flow or movement of said piston rod. During a work stroke, i.e. during damping,

the O-ring 18 moves in direction towards said cover 5 due to the pressure in the oil and its movement and thus closes the second longitudinal groove 11. The oil may flow into the adjacent chamber only through the piston rod-side conduit 16 and damping is considerable. In return stroke, the O-ring 18 gets displaced towards said piston portion 13, when the oil moves in opposite direction, wherein said O-ring 18 does not close the first groove 10 and the oil flows from the first chamber into the second one along the piston rod-side conduit 16 and the second longitudinal groove 11 and further through the first groove 10. The damping thus obtained is smaller and the movement of the piston 4 and the piston rod 3 in return stroke is therefore quicker.

Damping in a work stroke of the damper may be increased or rather changed by employing an additional elastic element 21, like in the second embodiment. The elastic element 21 having the size of a central through hole as a function of the level of required damping is set on said piston rod 3 and is located in the transversal through opening 12 of said piston 4. Under the action of the oil pressure the elastic element 21 fits the surface 22 of the valve portion 14 and thus partly closes the piston rod-side conduit 16 in dependence of the size of the internal diameter of the hole.

It is understood that a man skilled in the art may think of different embodiments based on the above description without circumventing the essence of the invention defined in the appended claims.