DE29717654U1 - Piston for a piston compressor - Google Patents

Description

STREET:.-&

Patent attorneys
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Patent attorneys

European Patent ^Attorney

European trademark attorney

Dipl.-lng. JOACHIM STRASSE "' Dr.rer.nat. ALFONS J. HOFSTETTER "

Authorized representatives at

" European Patent Office
* European Office for Harmonization in the Internal Market (Trade Marks and Designs)

Attorney file: 24366 ALUSUISSE BAYRISCHES DRUCKGUSS-WERK GMBH & CO. KG

In Wiegenfeld 10
D-85570 Markt Schwaben

New German utility model application

Piston for a piston compressor

BALANSTRASSE 57 · D-81541 MUNICH

Telephone +49/(0)89 - 45 09 18 ■ Fax +49/(0)89 - 45 09 18 12 · Voice +49/(0)89 - 45 09 18 20

EMAIL Strasse-Hofstetter@T-Online.de

ALUSUISSE BAYRISCHES DRUCKGUSS-WERK GMBH & CO. KG 24366 New German utility model registration

Piston for a piston compressor

The present invention relates to a piston for a piston compressor for gaseous media, preferably air. This piston has an inner piston body and a plastic jacket ring on its outer circumference, with which the piston is to rest against an inner cylinder wall. The piston can be connected to its connecting rod in a fixed or articulated manner. Furthermore, an intake valve can be located in the valve body or arranged separately. It is a piston compressor that runs essentially dry. From EP 725 898 (= EP 95 929 853 = WO 96/0543 0) it is known to insert an endless coil spring into the plastic jacket ring in an annular groove that is open in the compression direction in order to ensure that the plastic ring jacket surface rests against the inner piston wall. If the plastic jacket ring expands during operation due to heating, the tight contact with the inner piston wall is maintained due to the effect of the spring.

The piston compressor is usually carried as an accessory in the vehicle for inflating the tires. Especially in cold outside temperatures, it may be necessary to use the compressor to increase the pressure that has dropped in the tire. However, the compressor is also exposed to this cold temperature. When the compressor is started in cold temperatures, the plastic casing ring has contracted radially together with the inserted spring and no longer lies tightly against the inner wall of the piston. The endless coil spring cannot prevent this contraction as it shortens even at low temperatures. The result is that the medium is not compressed or is only insufficiently compressed. Only after a period of idling, when heat is released in the compressor by idling

has been wound, the sealing effect between piston and cylinder can slowly build up again. The object of the invention is to improve the type of piston described at the beginning to such an extent that even in very cold temperatures, a compressed flow rate of medium is available from the start of switching on.

According to the invention, the object is achieved in that the spring consists of an open steel ring, the open ends of which, lying opposite one another in the circumferential direction, lie on top of one another at normal room temperature.

The steel ring advantageously blocks itself against contraction in cold weather because it cannot shorten beyond its initial size at room temperature. Nevertheless, it develops sufficient spring action, especially when the outer wall of the piston expands as the operating temperature increases. Then the spring also opens and ensures a tight fit even when the temperature rises.

In a further embodiment, the groove in which the steel ring is inserted is open radially inwards.

Further details, features and advantages emerge from the following description of an exemplary embodiment shown in the drawings.

Show it:

Fig. 1 is a schematic elevation and

Fig. 2 is a plan view, partly in section, taken along the line II-II in Fig. 1.

A piston 10 is movable up and down in a cylinder 12. A piston body 14 sits on a connecting rod 16, supported by a plate 18. The piston body 14 is radially outwardly surrounded by a plastic

surrounded by a plastic ring 20, which rests with its spherical section surface 22 on the inner wall of the cylinder 12. The plastic ring 20 is pushed into this position by a steel spring ring 24. This ring 24 is located in a radially inward-facing groove 25 and has a gap 26 in the direction of its circumference, which is selected so that the open ends of the gap 26 lie on top of one another during assembly at normal room temperature. This ensures that at cold temperatures the spring ring cannot contract beyond the preset amount and thus a tight fit of the piston against the inner wall of the cylinder is always guaranteed even at cold temperatures.

Claims (2)

t · ALUSUISSE BAYRISCHES DRUCKGUSS-WERK GMBH & CO. KG 24366 German utility model application Piston for a piston compressor Claims: 1. Piston for use in a piston compressor for gaseous media, preferably air, with a piston body, which has a plastic casing ring on its outer circumference, which is pushed radially outwards against the inner cylinder wall by a spring inserted in the plastic casing ring, characterized, that the spring consists of an open steel ring (24) whose open ends (26) lying opposite one another in the circumferential direction lie on top of one another at normal temperature. 2. Piston according to claim 1,
characterized, that the steel ring spring (24) is inserted into a radially inwardly open groove in the plastic casing ring.