GB2216228A

GB2216228A - A piston ring

Info

Publication number: GB2216228A
Application number: GB8902607A
Authority: GB
Inventors: Gunther Lochner; Helmut Konicke; Hans Sackenreuter
Original assignee: Diehl GmbH and Co
Current assignee: Diehl Verwaltungs Stiftung
Priority date: 1988-02-27
Filing date: 1989-02-06
Publication date: 1989-10-04
Anticipated expiration: 2009-02-06
Also published as: GB8902607D0; GB2216228B; DE3806348A1; FR2627834A1

Description

nr 2 16,2 2 8 A PISTON RING The invention relates to piston r _4 ngs and

like sealing rings (hereinafter generally referred to as "piston rings"), for example, for pistons or piston-rods, which operate at high speeds, have large sealing gaps which vary under pressure, and/or are subjected to large differences in pressure.

Piston rings are known "per se" in a multiplicity of different materials and designs. They are as a rule inserted in ring grooves of a piston or of a piston rod and, by reason of a radially outwardly directed spring force, butt in a sealing manner against the inner wall of a cvlinder. The spring force is limited by the maximum permissible stress of the piston ring upon the fittling, which in turn results from the elasz--c limir of the material. The known piston rings are altogether suitable _C for use under normal operating conditions. In the verv O low pressure region, the tightness of the piston ring is determined only by its bias (initial tension). However, with small ratios of the nominal diameter to the radial height of the piston ring, the surface pressure resulting from the initial stress is limited. If very high piston or respectively piston-rod speeds of between 15 m/sec and 75 m/sec are required and into the bargain a sealing with relatively large sealing gaps, constantly varying under pressure, between the piston and the cylinder wall is to be provided, then the choice from the known piston rings is already problematical. If, furthermore, additionally great differences in pressure occur and the piston ring is to have a relatively large diameter, then demands exist for a piston ring which exceeds the capabilities of the orior art rinas known to date.

The problem of the invention is, therefore, to Ment4 provide a piston ring, of the type oned a, the 1) 2 beginning hereof, which in the described operating conditions affords an improvement in or respectively a reduction of the wear behaviour, more especially of the counter working surface in the cylinder, and preferably an improvement in the sealing action of the biased piston ring without pressure loading.

In accordance with the invention there is provided a piston ring, such as a piston ring for pistons or piston- rods which operate at high speeds, have large sealing -ed to gaps which vary under pressure, and/or are subject large differences in pressure, characterised in that the piston ring is of radially resilient form and has in its working surface a ring groove, into which is inserted an insert band which protrudes radially beyond the pistonring working surface and is formed from a material which is the same as or different from the material of the piston ring.

-s rad-4al-"-- The piston ring as a result of it 7- resilient design, has a basic resilience to press againsz the piston and/or cylinder; and the band is preferably formed from a low-friction material, which is the same as or different from the material of the piston ring. This insert band can, for example, be formed from a plastics material which is optionally provided with fillers, from a composite material or from a nonferrous alloy. The ring groove in the piston ring can have axial side walls having a conically extending contour.

The insert band can have a working surface, protruding from the piston ring, of optionally flat or else also crowned cross-sectional contour. The inser-t band can be held to the bottom surface of the ring groove optionally in a form determined or force determined manner, and be comblike in cross-sectional shape, in which respect radially shorter webs are inserzed inzo the comb-interstices and these webs may consist of optionally the same material as or of a different material from the insert band.

The ends of the piston ring can, furthermore, intermesh at the point of separation thereof in a longitudinally displaceable manner, e.g. with groove and tongue, in which respect, the radially outer end regions of the ends can each be shaped in such a way that mutually opposing shorter groove edges overlap upon the longitudinal displacement of the ends.

As a result of the invention, a piston ring having an inserted sealing band made of a plastics material, a composite material or else a nonferrous alloy, is provided which is distinguished by an improved wear behaviour with respect to the counter working surface e.g. of the cylinder, and by an improvement in the sea'Ling action of the stressed piston ring without pressure loading. This Diston ring has a technically -ory tightness in the static region under and satisfact without load and is insensitive to high brief pressure peaks with the least possible friction. As a result of the great spring action in the radial direction, the piston ring is given altogether a good basic inherent thrust against the cylinder wall, and a squeezing in the radial direction which is additionally brought about by the respective operating pressure. As a result of the good sealing of this piston ring which is achieved, a.

leakage which is only slight and which occurs only to an acceptable extent takes place.

The pis-con ring may of internal or external form; and may be provided in a device to seal4nalv engage a piston or piston rod instead of being mounted on the piston or rod.

4 The piston ring is particularly suitable for use in guns having liquid propellant systems. cl The invention includes such devices or guns provided 5 with one or more of the piston rings.

Examples of the invention are shown in the accompanying diagrammatic drawings, in which:- FIGURE 1 shows in section a piston ring with insert band in the installed state in a device; FIGURE 2 shows in section a piston ring of a different design; FIGURE 3 shows in section a piston ring having a design which is modified vis-a-vis the piston ring in FIGURE 2; FIGURE 4 shows in section in piston ring of a further design; FIGURE 6 shows in section a piston ring having a comblike insert; FIGURE 7 shows in perspective view the point of separation of the piston ring without insert band; FIGURE 8 shows a section through the piston ring with insert band along the line VIII-VIII in FIGURE 7; FIGURE 9 shows piston rings in an example of installation on a piston rod.

The piston ring 1 has a relatively large outside diameter 2 and an inside diameter 3, and is disposed in a groove in a piston or piston rod 5 to face the internal working surface 10 of a cylinder 4 of a device no-c otherwise shown.

The piston ring 1 has centrally in its working surface 6 an encircling ring groove 7, into which is inserted an insert band 8,12 etc, as hereinafter described. The insert band 8 protrudes with its outer end face 9 beyond the working surface 6 of the piston ring 1, and butts in operation against the surface 10 of the cylinder 4. In this respect the abutment of the insert band 8 is effected in such a way that a sealing is effected between the piston ring 1 and the cylinder 4. The insert band 8 preferably consists of plastics material, a composite material, a nonferrous alloy or a metallic alloy, in order thereby to achieve an improvement in and a reduction of the wear behaviour, more especially at the cylinder working surface 10. As a result of the resilient bias of the piston ring 1 an imDrovement in the sealing action is also achieved without pressure loading. A piston ring constructed with 2b these features is particularly useful for maximum pressure seals in the megagramme force region and where high piston and piston-rod speeds of about 115 m/sec to 75 m/sec are required. With this piston ring 1 the sealing with very large sealing gaps which vary under pressure is possible. In order to ensure both good sealing properties and good running properties, for example dry running, the insert band 8 can in accordance with the invention be produced from a high-pressure-resistant plastics material, which is reinforced by glass fibres and is possibly equipped with or incorporates additional lubricating means. As a result of the achieved reduction in the sealing friction at high piston speeds, hot running, which can possibly lead as far as the ignit-:cn of correspondingly used media, is avoided.

In the embodiment shown in FIGURE 1 the band 8 is c- substantially rectangular cross-section.

6 FIGURES 2 to 6 show further possible constructions of piston rings 1 with insert bands.

FIGURE 2 shows an insert band 12 which has a part- spherically curved ring-outer surface 13. At the sides the insert band 12 projects beyond and overlaps the piston-ring working surface 6.

The insert band 25 shown in FIGURE 3 is a modification of the insert band 12 of FIGURE 2. The ring-outer surface 26 is cylindrical to lie flat against th cylinder 4. Both of the sides the insert band 25 extend beyond the groove 7 to form collars 27 or 28 around the surface 6. The collars can either be short in is design as the collar 27 or terminate as collar 28 flush with the side wall 29 of the piston ring 1. Both versions are for the sake of simplicity shown in FIGURE 3, namely to the left and right of the central line 30. This design is particularly suitable for piston rings having a gas-tight ring gap.

Shown in FIGURE 4 is an insert band 14 with an crowned outer ring surface 15, in which respect the lateral limitation is bounded by conically shaped surfaces 16.

Instead of diverging outwardly between these radially diverging conical side surfaces 16, the insert band 18 shown in FIGURE 5 has a radially outwardly convergently tapering shape between conically shaped side surfaces 17, the groove 7 being undercut so that the shapes of the ring and groove cooperate to hold the ring in the groove.

In FIGURE 6 the insert band 19 consists of a structure which is comb-like in the radial direction, and in the comb-interstices of which are inserted webs 20 7 L made of the same material as or optionally a different material from the insert band 19. These ring webs 20 are in their radial extent shorter than the teeth 21 of the comb-like insert band 19. In this way only the teeth 21 of the comb-like insert band 19 butt with their end surface in a sealing manner against the cylindrical working surface 10 of the cylinder.

In the perspective representation.of the piston ring 1 shown in FIGURE 7, the ring groove 7 for the insert band 8, 12, 25, 14, 18, 19, not shown here, can be seen. The ring groove 7 has a bottom surface 32 and side walls 33 running (e.g., tapering conically to suit the band 14) towards the bottom surface 32 side walls 33. The front ends 34 and 35 of the piston ring 1 are at its point of separation designed in the type of construction of a longitudinally displaceable tongue 36 in a groove 37. Whereas, on the one hand, t-he groove edges 38 opposing one another in the end region are of constant height, on the other hand the two further groove edges 39 opposing one another in the end region, have shortened height regions 40, 41 close to the front ends 34, 35. This special shaping ensures an adequate fluid tightness also at the point of separation of the piston ring 1 and at the same time prevents the deformation of the insert band at this point during the longitudinal displacement of the front ends 34, 35 of the piston ring 1, which accompanies radial movement in the direction of the cylinder wall.

Shown in FIGURE 9 is the use of several piston rings 1, in accordance with the invention, in a liquid propellant system of a tank gun. Disposed in the weapon housing 22 in an annular chamber 23 is a piston 55 which is movable axially in the direction of the arrow 24. The piston 5 and the piston shaft 31 are both annular in shape, whereby the chamber 23 is split up into an outer 8 annular chamber 23.1 and into an inner annular chamber 23.2. Since different media can be disposed in the two annular chambers, for example the fuel and oxidizer known as liquid propellants for weapons, an absolute separation of the two media is necessary until these are forced into a corresponding combustion chamber by the piston 5. In the case of tank guns for liquid propellants with a regenerative injection process very high injection piston speeds of up to 75 m/sec are required, added to which are very high pressures, in order to inject the components completely into the combustion chamber within a very short time. In this example of use the piston 1, in accordance with the invention, insert bands 8 are utilised in both internal and external piston ring forms, and bands 14 are employed similarly in both internal and external piston ring forms. Of course, in the case of -on, the insert bands in this example of use of the pist accordance with any of FIGURES 1 to 6 are also usable instead of the bands 8 or 14. 20 The bands may be continuous or interrupted, e.g. at the ring gap or elsewhere, according to the nature of the band material and design of the rings.

11 9 1

Claims

1. A piston ring, such as a piston ring for pistons or piston-rods which operate at high speeds, have large sealing gaps which vary under pressure and/or are subjected to large differences in pressure, characterised in that the piston ring is of radially resilient form and has in its working surface a ring groove, into which is inserted an insert band which protrudes radially beyond the piston-ring working surface and is formed from a material which is the same as or different from the material of the piston ring.

2. A piston ring as claimed in Claim 1, characterised in that the insert band is formed from a plastics material which is optionally provided with fillers.

3. A piston ring as claimed in Claim 1, characterised in that the insert band is formed from a composite material.

4. A piston ring as claimed in Claim 1, characterised in that the insert band is formed from a nonferrous alloy.

5. A piston ring as claimed in any preceding claim, characterised in that the ring groove has axial side walls having a conically extending contour.

6. A piston ring as claimed in any preceding claim, characterised in that the insert band has a working surface of flat or crowned cross-sectional contour protruding from the piston ring.

7. A piston ring as claimed in any preceding claim, characterised in that the insert band is held to the bottom surface of the ring groove in formdetermined or force-determined manner.

8. A piston ring as claimed in any one of Claims 1 to 4, characterised in that the insert band in cross-section is of comb-like form and has radially shorter webs inserted into the comb- teeth interstices and made of the same material as or a different material from the insert band.

9. A piston ring as claimed in any one of the preceding claims, characterised in that the ends of the piston ring at the point of separation thereof intermesh in a longitudinally displaceable in groove and tongue manner, and in that the radially outer end regions of the ends are shaped in such a way that respectively mutually opposing shorter groove edges overlap upon the longitudinal of the ends.

10. A piston ring, more especially a piston ring for high piston or respectively piston-rod speeds and large sealing gaps which vary under pressure, as well as for large differences in pressure, characterised in in that the piston ring as a result of a radially resilient design has a basic squeezing and has in its working surface a ring groove, into which is inserted an insert band which protrudes radially beyond the piston-ring working surface and is formed from a material having a low coefficient of friction, which is the same as or different from the material of the piston ring.

11. A piston ring substantially as hereinbefore described with reference to any one of FIGURES 1 to 6 or FIGURES 7 and 8 of the accompanying drawings.

12. A device comprising piston or piston rod fitted with or sealingly engaged by a piston ring as claimed in any preceding claim.

11

13. A device provided with piston rings as claimed in any one of Claims 1 to 11 and substantially as hereinbefore described with reference to FIGURE 9 of the accompanying drawings. 5

14. A gun having a-liquid propellant system in which the piston or piston rod is provided with or is sealed by one or more piston rings as claimed in any one of Claims 1 to 11. 10 Published 1989 a, The PatentOffice, State House, 6671 Ri& HolbornLondonWC1R 4TP. Purther copies maybe obtained from The Patent Office Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex tachniques WL St Mary Cray, Kent, Con. 1/87