This is a U.S. national stage of application No. PCT/EP2008/060609, filed on Aug. 13, 2008, which claims priority to the German Application No.: 10 2007 040 455.9, filed: Aug. 28, 2007; and German Application No. 10 2008 040 984.7 filed Aug. 5, 2008 the contents which are incorporated herein by reference.
1. Field of the Invention
The invention is directed to a protective pipe for a piston-cylinder unit.
2. Prior Art
A piston rod of a piston-cylinder unit is a component whose surface must be shielded from dirt so that a seal closing the cylinder is not destroyed by fine particles in the dirt.
Protective pipes made of plastic have become popular for reasons having to do with weight. The protective pipe has a base that is often supported on a shoulder of the piston rod. The base is frequently produced as an annular metal disk which is connected by positive engagement to a plastic pipe. The metal base provides for good dimensional stability of the plastic pipe but adds considerably to the cost of the protective pipe. In this connection, reference is had to DE 28 50 051 A1; DE 19 51 753 U, or DE 19 51 754 U.
DE 37 35 058 A1 discloses a one-piece protective pipe made of plastic in the construction shown in
DE 82 28 262 U1 discloses in
It is an object of the present invention to realize a protective pipe for a piston-cylinder unit made entirely of plastic and optimized with respect to dimensional stability.
According to one embodiment of the invention, this object is met by a conical surface region of a bottleneck-shaped base having an accumulation of material which increases radially inward from its outer edge.
The base is reinforced against bending loads to prevent a critical shape deviation when the protective pipe is radially loaded. This operating characteristic facilitates the use of a one-piece protective pipe which, as was already mentioned, has a considerable cost advantage over a solution comprising multiple parts.
In one embodiment of the invention, the wall thickness of the base increases toward the radial inner side. The inner side extends at right angles to the longitudinal axis of the piston rod.
Further, the wall thickness of the pipe body increases towards the base. This provides an appreciable stabilization of the protective pipe against bending forces precisely at the transitional area between the base and the pipe body.
Depending on the installation space provided for the piston-cylinder unit, the inner diameter of the pipe body decreases towards the base and/or the outer diameter of the pipe body increases towards of the base.
In one embodiment of the invention, the surface region of the base has a rib structure. In spite of a comparatively economical use of material and a small mass, good dimensional stability is achieved.
The outer diameter of the pipe body can also have ribs extend towards the base. The ribs in the pipe body need not be formed along the entire length of the pipe body. A region directly adjoining the base is of particular importance.
To facilitate removal of the protective pipe from the mold, the ribs at the outer diameter of the pipe body merge with the rib structure of the base.
In one embodiment of the invention, the pipe body has a greater and constant nominal material thickness in the supporting region merging with the base. This variant can be provided with a rib structure at the base and at the pipe body.
The invention will be described in more detail with reference to the following description of the figures.
The protective pipe 7 according to
The bottleneck-shaped base 9 has a guide portion 15 that directly contacts the outer surface of the piston rod 5 and provides for radial positioning. (
To prevent contact between the protective pipe 7 and an outer cylinder 19 when the protective pipe 7 is radially loaded at its open end, the base 9 has an increasing accumulation of material in radial inward direction starting from its outer edge. In the variant according to
Viewed in conjunction,
A variant of a protective pipe 7 which is optimized particularly with respect to weight is shown in
The embodiments according to
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
Number | Date | Country | Kind |
---|---|---|---|
10 2007 040 455 | Aug 2007 | DE | national |
10 2008 040 984 | Aug 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2008/060609 | 8/13/2008 | WO | 00 | 2/26/2010 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2009/027228 | 3/5/2009 | WO | A |
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Number | Date | Country | |
---|---|---|---|
20100213655 A1 | Aug 2010 | US |