DE20106700U1 - Piston for a piston compressor - Google Patents

Description

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Alusuisse Bayrisches Druckguß-Werk Attorney file: 25900

GmbH & Co. KG
D-85570 Markt Schwaben

German utility model

&iacgr;&ogr; Piston for a piston compressor

DESCRIPTION:

The present invention relates to a piston for a piston compressor for gaseous media with a connecting rod or a piston rod that can be moved back and forth within a cylinder, wherein the connecting rod is connected to the piston and the piston has a piston plate and an annular piston head resting on the piston plate and a valve plate with at least one passage for the gaseous medium to be sucked in from the underside of the piston.

Such pistons are known, for example, from European patent application EP 0 980 977 A2. To prevent leaks between a piston head of the known piston and an inner cylinder wall, the piston head has a closed support ring made of metal or a metal alloy on its inner ring side, the expansion coefficients of the support ring material and the cylinder material being approximately the same. The piston head can be moved up and down between a valve plate and a piston disk on which the piston head rests. This known piston has the advantage that it, or rather the ring-shaped piston head, is designed to be rotatable. This prevents one-sided wear of the piston, as is the case with other known pistons that cannot be rotated.

The disadvantage of the known pistons, however, is that they cannot be subjected to constant loads. Today's applications for such pistons require a high throughput volume in the shortest possible time at relatively high pressures. At the same time, however, the pistons or piston compressors should be as small as possible. Such requirements can therefore only be met by using a higher speed, which, however, leads to a significantly higher load on the pistons. Such high loads lead to the wear phenomena mentioned above and, as a result, to leaks between the piston head and the inner cylinder wall.

It is therefore an object of the present invention to provide a piston of the type mentioned at the outset which can withstand continuous loads and at the same time ensures a secure seal between the piston and the inner cylinder wall.

This problem is solved by a piston with the features of claim 1.

Advantageous embodiments are described in the subclaims.

In a piston according to the invention for a piston compressor for gaseous media, a piston head consists of a first and a second annular piston head element, wherein the first piston head element comes to rest on a piston plate and the second piston head element engages in the first piston head element in such a way that the first and the second piston head element form a common central ring opening for receiving a valve plate, wherein the second piston head element is designed to be relatively more rigid than the first piston head element. The division of the piston head according to the invention into a first and a second piston head element, wherein the two elements have different levels of stability, advantageously combines the advantages of the previously known pistons. The first piston head element, which is designed to be softer than the first piston head element, seals securely in the direction of the dead center of the cylinder. Due to the relatively soft consistency

of the first piston head element compared to the second piston head element, the first piston head element is movable, in particular rotatable. This prevents one-sided wear of this piston area. In contrast, the second piston head element, which sits on the first piston head element, is more rigid than the first element. The second piston head element therefore has no or only very little mobility. Due to its relatively rigid design, it can therefore withstand greater loads, in particular permanent loads, than the first piston head element. The combination of the two piston head elements ensures less wear overall

&iacgr;&ogr; with a higher continuous load capacity and a correspondingly reliable seal of the piston according to the invention. A significantly longer service life of the piston is also guaranteed.

In an advantageous embodiment of the invention, the second piston head element is designed with slots. The slots in the second piston head element ensure that there is a sufficient seal between the piston head and the inner cylinder wall even when the piston is actuated and the temperature rises accordingly, since the slotted second piston head element expands in the direction of the inner cylinder wall when heated.

In a further advantageous embodiment of the invention, the differences in stability between the first and second piston head elements are created by a different geometry, shape and support of the two piston head elements. For example, the first piston head element can have a smaller cross-sectional area than the second piston head element. This makes it possible for the first and second piston head elements to be made of the same material; in particular, the two elements can be made of plastic, namely polytetrafluoroethylene. By using only one material, the manufacturing costs of the piston are significantly reduced. However, it is also conceivable that the stability differences mentioned between the first and second piston head elements are created by using two different materials for the respective piston head elements.

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In a further advantageous embodiment of the piston according to the invention, the first piston head element has an annular groove for receiving a support ring. The support ring ensures that an outer ring surface of the first piston head element is reliably pressed against the inner cylinder wall so that the piston head seals against it.

In a further advantageous embodiment of the piston according to the invention, the second piston head element has, on the side remote from the first piston head element, on its inner ring side, an annular support surface for supporting a

&iacgr;&ogr; annular collar of the valve plate. In addition, the first piston head element can have an annular limiting flange on the inside of its ring on the side remote from the second piston head element. Such a design of the first and second piston head elements ensures a defined mobility of the piston head between the valve plate and the piston plate.

In a further advantageous embodiment of the piston according to the invention, the ring outer surfaces of the first piston head element and the second piston head element together form an outwardly curved surface. The outwardly curved surface presses against the inner cylinder wall and thus ensures an excellent sealing effect.

Further details, features and advantages of the invention emerge from the following description of two embodiments shown in the figures. They show:

Figure 1 is a perspective view of a piston according to the invention;

Figure 2 is a schematic, partially sectioned representation of a piston head of the piston according to the invention;

Figure 3 is an exploded view of the piston according to the invention according to a further embodiment.

Figure 1 shows a perspective view of a piston 10 for a piston compressor for gaseous media. The piston 10 is connected to a connecting rod 14 that can be moved back and forth within a cylinder (not shown), the connecting rod 14 having a connecting element 20, in particular a bearing, at the end opposite the piston 10, which is connected to a drive shaft of an electric motor (not shown). It can be seen that the piston 10 has a piston plate 16 and a piston ring 18 mounted on the piston plate 16.

&iacgr;&ogr; resting annular piston head 12. A valve plate 26 with several passages 32 for the gaseous medium to be sucked in from the underside of the piston is arranged within the annular piston head 12.

The valve plate 26 protrudes through the central ring opening of the piston head 12, the diameter of the protruding valve plate element 34 (see Figure 3) being smaller than the diameter of the central ring opening. The piston head 12 can be moved up and down between the valve plate 26, which is attached to the connecting rod 14, and the piston plate 16. It can also be seen that the piston head 12 consists of a first and a second annular piston head element 22, 24, the first piston head element 22 coming to rest on the piston plate 16 and the second piston head element 24 engaging in the first piston head element 22 such that the first and second piston head elements 22, 24 form the central ring opening of the piston head 12 for receiving the valve divider. The second piston head element 24 also has a slot 56.

Figure 2 shows the piston head 12 in a schematic sectional view. It can be seen that the piston head 12 consists of the first piston head element 22 and the second piston head element 24 resting on the first piston head element 22. The first piston head element 22 has an annular support surface 38 on the inside of the ring for receiving a corresponding annular support surface 40 of the second piston head element 24. Furthermore, the first piston head element has an annular

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Stop surface 42 for receiving an annular shoulder 44 of the second piston head element 24.

Furthermore, it can be seen that the second piston head element 24 has an annular support surface 46 on the inside of the ring on the side remote from the first piston head element 22 for supporting an annular collar 50 (see Figure 3) of the valve plate 16. The first piston head element 22 has an annular limiting flange 48 on the inside of the ring on the side remote from the second piston head element 24. In addition, an annular groove 36 for receiving a support ring 18 is formed in the first piston head element 22. It can also be seen that the annular outer surfaces 52, 54 of the first piston head element 22 and the second piston head element 24 together form an outwardly curved jacket surface.

The second piston head element 24 is relatively more rigid than the first piston head element 22. These differences in stability are created by a different geometry, shape and support of the elements, as can be clearly seen from Figure 2. It is also clear that in the embodiment shown, the first piston head element 22 has a smaller cross-sectional area than the second piston head element 24.

Typically, the first and second piston head elements 22, 24 are made of plastic, in particular polytetrafluoroethylene.

Figure 3 shows an exploded view of the piston 10 and the connecting rod 1.4 connected to it. It can be seen that the connecting element 20, which is arranged at the end of the connecting rod 14 opposite the piston 10, is designed as a bearing. A nose 28 is formed at the end of the connecting rod opposite the connecting element 20, which reaches through an opening 58 of the piston plate 16 and a corresponding opening 30 of the valve plate 26 and thus creates a connection between these elements. It can be seen that the first piston head element 22 rests on the valve plate 16. The second piston head element 24, which

according to this embodiment is not slotted, and thus forms the annular piston body with a central ring opening. The valve part element 34 projects into this central ring opening.

Claims (11)

1. Piston for a piston compressor for gaseous media with a connecting rod or a piston rod ( 14 ) that can be moved back and forth within a cylinder, the connecting rod ( 14 ) being connected to the piston ( 10 ) and the piston ( 10 ) having a piston plate ( 16 ) and an annular piston head ( 12 ) resting on the piston divider ( 16 ) as well as a valve plate ( 26 ) with at least one passage ( 32 ) for the gaseous medium to be sucked in from the underside of the piston, characterized in that the piston head ( 12 ) consists of a first and a second annular piston head element ( 22 , 24 ), the first piston head element ( 22 ) coming to rest on the piston plate ( 16 ) and the second piston head element ( 24 ) engaging in the first piston head element ( 22 ) in such a way that the first and the second piston head element ( 22 , 24 ) form a common central ring opening for receiving the valve plate ( 16 ), wherein the second piston head element ( 24 ) is relatively more rigid than the first piston head element ( 22 ). 2. Piston according to claim 1, characterized in that the second piston head element ( 24 ) is slotted. 3. Piston according to claim 1 or 2, characterized in that the stability differences between the first and the second piston head element ( 22 , 24 ) are created by a different geometry, shape and support of the elements. 4. Piston according to claim 3, characterized in that the first piston head element ( 22 ) has a smaller cross-sectional area than the second piston head element ( 24 ). 5. Piston according to one of the preceding claims, characterized in that the first and second piston head elements ( 22 , 24 ) consist of plastic. 6. Piston according to claim 5, characterized in that the plastic is polytetrafluoroethylene. 7. Piston according to one of the preceding claims, characterized in that the first piston head element ( 22 ) has an annular groove ( 36 ) for receiving a support ring ( 18 ). 8. Piston according to one of the preceding claims, characterized in that the first piston head element ( 22 ) is designed to be rotatable. 9. Piston according to one of the preceding claims, characterized in that the second piston head element ( 24 ) has, on the side remote from the first piston head element ( 22 ), on its inner ring side, an annular support surface ( 46 ) for supporting an annular collar ( 50 ) of the valve plate ( 16 ). 10. Piston according to one of the preceding claims, characterized in that the first piston head element ( 22 ) has an annular limiting flange ( 48 ) on its ring inner side on the side remote from the second piston head element ( 24 ). 11. Piston according to one of the preceding claims, characterized in that the annular outer surfaces ( 52 , 54 ) of the first piston head element ( 22 ) and of the second piston head element ( 24 ) together form an outwardly curved jacket surface.