1. Field of the Invention
This invention relates to a plunger piston for an air spring, which plunger piston is formed as a hollow body and has a bottom to which a circumferential casing part is indirectly or directly coupled, and a plunger piston, in its cover region remote from a bottom, has a connecting edge for a bellows and at least one air passage opening.
2. Discussion of Related Art
A plunger piston of this kind is known from U.S. Pat. No. 6,386,524 B1, wherein a hollow body is formed by two circumferential walls. An inner circumferential wall is situated concentric to an outer circumferential wall. The two circumferential walls are supported in relation to each other by reinforcing ribs. The inner circumferential wall encompasses an air passage opening in the cover region of the plunger piston. The air passage opening is delimited by an edge to which a bellows can be fastened. The bottom region of the plunger piston can be sealed by a plate. The plate in this case is integrally joined, for example glued, to the lower edges of the circumferential wall. In order to provide the air spring with the greatest possible air volume, the inner circumferential wall has air passage openings that connect the individual volume regions of the hollow body to one another. When rapid load changes occur, undesirable air oscillations can occur in the region of these air passage openings. In addition, the inner circumference wall takes up space and thus limits the available air volume of the hollow body.
One object of this invention is to provide a plunger piston of the type mentioned above but which has a simple design and is easy to produce.
This object is achieved with a hollow body that has a cup-shaped lower part comprised of the bottom and the casing part. An upper part is placed onto the lower part and connected to the lower part in an airtight fashion, and the upper part has the connecting edge.
The cup-shaped lower part can be easily produced and forms the lower airtight closure of the hollow body. The upper part can be placed like a cover onto the lower part, thus delimiting the cavity defined by the hollow body. The upper part with its connecting edge forms the coupling point for the bellows. It is thus possible to control the introduction of force from the upper part to the lower part by the embodiment of the upper part. In particular, a load transfer can be carried out, if so desired, from the upper part directly into the circumferential casing part of the lower part. This permits a simpler and more stable design of the plunger piston.
According to one embodiment of this invention, it is possible for the casing part to have a cylindrical region that transitions into a circumferential, cylindrical side wall of the upper part having the same diameter. The cylindrical regions of the upper part and lower part that transition into each other can form the contact and rolling surface for the bellows. This embodiment also permits a kit-like design of the plunger piston. For example the upper part, embodied in the form of a universally usable component, can be placed onto various lower parts. Thus, it is possible for the various lower parts to enclose various air volumes.
The kit-like embodiment of the plunger piston can also be achieved within the scope of this invention if a standardized interface is provided between the lower part and the upper part.
An airtight connection of the lower part to the upper part can be achieved in a simple fashion if the lower part and the upper part each has a circumferential edge and the upper part with the lower part are joined to each other at the edges by a sealed connection.
In order to improve the load transfer, according to one embodiment of this invention, the lower part and/or the upper part each is reinforced by reinforcing elements. In this case, the reinforcing elements of the lower part can be embodied in the form of ribs that are formed integrally onto the casing part and extend in the radial direction.
The design of the upper part achieves a more stable structure because the reinforcing elements of the upper part are formed integrally onto the connecting edge and protrude into the air passage region enclosed by the connecting edge and because at least part of the reinforcing elements, in their region remote from the connecting edge, are connected to a reinforcing part. This design makes it possible to reliably absorb and transfer radially acting clamping forces of the bellows.
A further reinforcing of the plunger piston is achieved if at least part of the reinforcing elements of the cover part have a supporting part that is supported against a counterpart supporting part of the lower part.
In one embodiment of this invention, the reinforcing elements of the lower part and upper part are at least partially supported against one another. This promotes the shunting of force from the upper part to the lower part.
In one embodiment of this invention, the cover-like upper part encloses a partial cavity that combines with the partial cavity formed by the lower part to form a whole cavity, with the partial cavities communicating in an air-conveying fashion.
The lower part and upper part are preferably embodied in the form of injection-molded plastic parts.
If the upper part has a convex, rounded transition that adjoins the cylindrical, circumferential side wall and supports a transition section, the transition section is sloped toward the lower part, and the annular connecting edge adjoins the transition section by a concave rounded transition, then a transfer region between the side wall and the connecting edge deflects the bellows in an optimized fashion in terms of tension.
According to one embodiment of this invention, the bottom of the lower part has a reinforcing element coupled to the bottom or embedded into the bottom, for example during the plastic injection-molding process. The reinforcing element stiffens the bottom at least partially. The transmission of force to a connected axle or body component is thus improved. This is accompanied by advantages with regard to the distribution of force if the bottom is not resting with its entire surface area against the axle/body component.
The reinforcing element can advantageously be formed as a plate or ring, with the plane of the plate or ring oriented in the direction of the bottom plane.
If a plunger piston is embodied so that the reinforcing element has a greater hardness than the bottom and is comprised, for example, of metal, then the lower part can be produced in a cost-optimized way in the form of a composite component made of two different materials.
This invention is explained in view of an exemplary embodiment shown in the drawings, wherein:
The counterpart support part 14 encloses a receiving region. A fastening screw that is screwed into the nut of the fastening receptacle 13 is accommodated with its thread in the counterpart support part 14.
The circumferential, cylindrical casing part 11 has a circumferential edge 15. The edge 15 is formed by a step-like cross-sectional reduction of the casing part 11.
Reinforcing elements 16 are situated in the cavity enclosed by the lower part 10. The reinforcing elements 16 are embodied in the form of ribs and extend radially inward from the casing part 11. They are integrally connected to the fastening receptacle 13, the casing part 11, and the bottom 12. As shown in
The upper part 20 has a circumferential edge 21 and is embodied with a step-shaped shoulder like the edge 15 of the lower part 10. The edge 21 is adjoined by a cylindrical, circumferential side wall 22. The side wall transitions via a convex rounded transition 23 into a transition section 24. The transition section 24 is sloped toward the lower part 10. The transition section 24 ends in a concave rounded transition 25. The rounded transition 25 is adjoined by a connecting edge 26. The connecting edge 26 is embodied in an annular form. The connecting edge 26 ends with a bead 27 and encompasses an air passage region.
As shown in
Like the lower part 10, the upper part 20 is embodied in the form of an injection molded part. The demolding again occurs along the central longitudinal axis, along the dot-and-dash line shown in
The reinforcing elements 28 of the upper part 20 and the reinforcing elements 16 of the lower part 10 are matched to one another in their circumferential distribution and are spaced apart from one another by the same distances. It is thus possible for the reinforcing elements 28, 16 of the upper part 20 and lower part 10 to be aligned with one another. As shown in
During assembly, the upper part 20 is placed with its edge 21 onto the edge 15 of the lower part 10. As shown in
As also shown in
As shown in
A bellows 30 is shown in
Number | Date | Country | Kind |
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102007035640.6 | Jul 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2008/006083 | 7/24/2008 | WO | 00 | 1/27/2010 |