Patent Application
20060042460
1. Field of the Invention
The present invention relates to a piston for a setting tool driven by expanding gases and including a piston head, and a piston body connectable with the piston head along an interface, with the piston head and the piston body having, respectively, in an interface region, at least one stop surface and at least one counter-stop surface.
2. Description of the Prior Art
In the setting tools driven by expanding gases, a piston is displaceably arranged in a piston guide and is driven by expanding gases such as, e.g., combustion gases. The piston head defines a piston area.
In setting tools with a comparatively small drive pressure, the piston area should be significantly increased in order to provide a sufficiently large driving force. In order to prevent the increase of weight by the same amount, the piston body and the piston plate or head are formed as separate parts of different materials and are then assembled. The piston body is formed, preferably, of a high-strength material because it directly contacts the set-in fastening element and should transmit, at a small diameter, large forces.
U.S. Pat. No. 5,860,580 discloses such a two-part piston in which threaded connection provides for a fixed connection of the piston head with the piston body. The necessary centering of the piston head with the piston body is carried out by the thread, whereas the transverse alignment of the piston head with the piston body is carried out by opposite flat or planar surfaces of the piston head and the piston body.
The drawbacks of such a piston consist in that the thread adversely influences the orthogonality because it is subjected to distortion upon hardening of the piston body by heat treatment. The manufacturing of such piston is very expensive.
Accordingly, an object of the invention to provide a piston for a setting tool driven by expanding gases in which the above-discussed drawbacks are eliminated.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a piston in which the stop surface and the counter-stop surface are formed by surfaces defining essentially complementary tapering regions.
The substantially complementary tapering regions insure an orthogonal alignment of the piston body with the piston head. A secondary adjustment or even bending of the piston into a correct position is not any more necessary.
It is beneficial when the complementary tapering regions are formed as cone-shaped regions. The cone-shaped insure a backlash-free connection.
Advantageously, the stop surface, which is provided on the piston head, is formed as an inner cone, and the counter-stop surface, which is provided on the piston body, is formed as a substantially complementary outer cone. Thereby, a geometry, which is easy to produce, is obtained.
Advantageously, the stop surface and the counter-stop surface are inclined to a surface extending parallel to the piston head at an angle α from 10° to 80°.
According to another advantageous embodiment, the complementary tapering regions are formed as spherical regions. The spherical regions likewise insure a backlash-free connection.
Advantageously, the stop surface, which is provided on the piston head is formed as an inner sphere, and the counter-stop surface, which is provided on the piston body, is formed as a substantially complementary outer sphere. Thereby, a geometry, which is likewise easy to produce, is obtained.
It is advantageous when the interface has thread connection elements. The thread connection elements insure that a fixed connection can be easily obtained, which provides for alignment of the piston body when the piston head and the piston body are screwed together.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when ready with reference to the accompanying drawings.
The drawings show:
During the assembly of the piston 10, the alignment of the piston body 12 relative to the piston head 11 takes place over the conical stop surface 14 and the complementary thereto, conical counter-stop surface 15, without a need in any further adjustment. It should be understood that both the stop surface 14 and the counter-stop surface 15 can be formed as interrupted surfaces.
Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof, and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 041 079.8 | Aug 2004 | DE | national |
