GB2095348A - Sealing rings - Google Patents

Abstract

A valve-stem seal has a dynamic sealing lip 29 engaging the stem and a static sealing zone 28 which is pressed over the valve-stem guide 34. The zone 28 is reinforced externally by a ring 31 having openings 33 which are filled by the elastomeric material of the sealing zone 28. The peripheral spacing between the circular or oval openings 33 is the same as or smaller than the peripheral width of the openings so that when the seal is pushed onto the guide 34 surplus material is forced out through the openings to prevent undue resistance to fitting. The area of the openings is preferably approximately equal to the area of remaining material. The invention is also applicable to radial shaft seals and sliding-ring seals which fit into housings and have internal reinforcing rings (Figs 1,2, not shown). <IMAGE>

Description

SPECIFICATION Sealing ring The invention relates to a sealing ring, in particular a radial shaft seal, a sliding-ring seal or a valve-stem seal, with a static and a dynamic sealing section, the static sealing section being in the form of a gripping seat and consisting of an elastomeric material bearing against the corresponding opposed surface of a receiving part, and with a cylindrical reinforcing ring which is arranged in the region of that peripheral surface of the gripping seat which faces away from the opposed surface and is provided with openings.

The above sealing rings are precision parts which are introduced into receiving parts of the same kind or are forced onto them. The sealing rings, but in particular the valve-stem seals, are generally able to bridge gripping seat tolerances (minimum valvestem guide diameter to maximum internal seat diameter tolerance) of 0.2 mm without damage. Due to manufacturing conditions, however, largertolerances up to a maximum of 0.8 mm generally have to be compensated for, which has not been possible heretofore, however, by reason of too great springing-back of the elastomer material, too high fitting force being required and too low gripping power, or power of adhesion.

There is already known from German Utility Model 6933319 a sealing ring for sealing off the gap between a valve steam and a valve stem guide and consisting of a metal reinforcing ring, a dynamic sealing lip connected to this ring and an elastomeric layer vulcanized onto the inner perpherial surface of the ring, this elastomeric layer serving as a gripping seat. The reinforcing ring is provided with one or more slots in the axial direction or a direction extending obliquely thereto, the slots being open in an axial direction and filled with elastomer material.

With such an arrangement, it is true that primarily a relatively great radial expansion of the reinforcing ring is possible in the slotted peripheral zone, but not in the adjacent closed or continuous peripheral zone.

For the following reasons, compensation of tolerances is not, however, possible with a sealing ring of this kind: As a rule, valve-stem seals are forced onto the valve-stem guide by means of a tool, the elastomeric material of the gripping seat having to yield. The greater the tolerance which is to be bridged, the more elastomer material must yield. Due to the unilaterally open axial slots, this is possible only to a very limited extent, since when the seal is forced on only the elastomer material located in the immediate vicinity of the slots can expand into them with radial outward arching of the material present in the slots.

The far greater remainder is displaced towards the sealing lip by the valve-stem guide and, due to the angular portion of the reinforcing ring which is directed inward radially, the elastomer material piles up in this zone. In unfavourable cases, it may happen that as a result of the substantially axial compression of the rubber the retained energy in the elastomer material partly forces the valve-stem seal back again from the valve-stem guide after removal of the fitting tool. In less unfavourable cases, the valve-stem seal springs back only slightly, is consequently not seated in optimum manner on the valve-stem guide and, in the course of time, may slip off the guide due to the oscillating movement of the valve stem.Similar, although not so extreme, effects also exist in the region of the gripping seat of radial shaft seals and sliding-ring seals and it may also happen in this case that tolerances must be bridged, which, however, in contrast to valve-stem seals, become smaller and not greater, because the seals referred to are introduced into receiving bores and not forced onto guides. The important difference between the individual seals is to be seen in that in radial shaft seals and sliding-ring seals the gripping seat is provided as a rule at the outer periphery, and in valve-stem seals it is provided at the inner periphery, of therein- forcing ring.

Furthermore, a liquid seal in the form of a radial shaft seal is known from U.S. Patent Specification 2,249,141. This consists essentially of an angular reinforcing ring which is completely surrounded by elastomeric material, the gripping seat being formed in the region of its axial arm or side and the dynamic sealing lip being formed on its radial arm or side. In one or both of the arms, the reinforcing ring, as seen in the peripheral direction, has profilings in the form of holes, bent portions or the like, which serve for better clamping the elastomer material to the reinforcing ring, without nevertheless being suitable for bridging fairly large tolerances.

The problem underlying the invention is so to improve a sealing ring by simple design means that it is capable of better adaptation to differenttoler- ances in conjunction with a constantly high gripping or adhering capacity and pressure or contact forces between the receiving part and the gripping seat which are as low as possible.

According to the invention, this problem is solved in that the webs left between the openings i.e. the peripheral spacings between the openings are of the same dimensions as, or of smaller dimensions than, the openings as seen in the peripheral direction. As a result of this change in the reinforcing ring, it is possible for not much elastomer material to be present in the zone between the openings and, when the sealing ring is fitted, this material can consequently extend away from the opposed surface into the openings with outward bulging of the material in them and, accordingly, also ensures better adaptation to different tolerances. The forces required for fitting are not increased thereby and, depending on the type of seal, are even kept lower, without the sealing ring springing back.With at the same time a high gripping capacity or power during operation, it is ensured that the seal, more particularly the valvestem seal, is not pulled off by the valve stem in the course of time. This advantage may be further enhanced if the minimum axial width of the remaining peripheral zones left by the openings is the same as, or smaller than, the overall dimension of the openings. Depending on the construction space available and the radial wall thickness of the reinforcing ring, it is furthermore proposed that the ratio of the area of the openings to the remaining material be made approximately equal and, in this case, too marked a weakening of the reinforcing ring can be avoided by altering the radial wall thickness.

For reasons of fitting, angular reinforcing rings are frequently employed. The features of the invention are also effective in this case. Preferably, in such reinforcing rings, the peripheral zone adjoining the bent-over side is smaller as seen in the axial direction than the zone remote from the bent-over side.

Consequently, on the one hand the peripheral zone remote from the bent-over side is not weakened unnecessarily and on the other hand X - elastomer material is not afforded any possibility of piling up in the region of the bent-over or angular portion and, therefore, of leading to the disadvantages already described.

Circular or slightly oval openings are regarded as preferred cross-sectional profiles, it being naturally also possible to employ angular profiles, which act similarly to circular openings, but compared with circular openings have the disadvantage that they are more difficult to produce and the notch effect in the shaping zone of the reinforcing ring and elastomer material is greater. Depending on the application, it may be appropriate for the openings to be arranged alternately staggered axially with respect to one another, in order in this way not to weaken only a certain peripheral zone, but be able to utilize the entire peripheral surface in optimum manner.

Tho invention is illustrated in the drawing and is deocsibsd in detail hereinafter. In the drawing: figures 1 and Ia show a radial shaft seal and a reinforcing ring illustrated on a larger scale; Figures 2 and 2a show a sliding-ring seal and a reinforcing ring illustrated on a larger scale; Figure 3 shows a valve-stem seal.

Figures 1 and la show a radial shaft seal 1 which is arranged in the receiving bore 2 of a machine part 3.

The shaft sealing ring 1 consists essentially of an elastomeric static sealing section 4, which is in the form of a gripping seat, and an elastomeric dynamic sealing section 5 in the form of a sealing lip loaded by a spring 6 and bearing against a rotating shaft 7; furthermore, an angular reinforcing ring 8 which is vulcanized onto the inner peripheral surface 9 of the static sealing section 4. As shown on a larger scale in Figure la, the reinforcing ring 8 is provided with circular or slightly oval openings 11 distributed uniformly at the periphery 10. The openings 11 are so distributed atthe periphery 10 that the dimensions of the webs 12 left between the openings 11 are smaller than the openings 11 themselves.The ratio of the two peripheral zones 13, 14 to the openings 11 is to be regarded in the same way, the openings 11, as seen in the axial direction, being displaced towards the bent-over side 15, so that the peripheral zone 13 is not excessively weakened. For the purpose of simpler production, the openings 11 are filled with the elastomeric material of the static sealing section 4.If the range of tolerance to be bridged between the receiving bore 2 and the static sealing section 4 has proved to be smaller than previously planned, there are no difficulties to neverthe less being able to fit the shaft sealing ring, since the elastomer material vulcanized onto the remaining webs 12 and the peripheral zones 13,14 is forced into the openings and the elastomer material present therein is forced out radially from the openings towards the inside and, consequently, gently arched projections or convexities 16 are formed.

figures 2 and 2a show a sliding-ring seal 17 which is likewise arranged in the receiving bore 18 of a machine part 19. The sliding-ring seal 17 consists of a static sealing section 20, which is in the form of a gripping seat, and a dynamic sealing section 21 in the form of an axially acting sliding ring which is held resiliently in the axial direction within the sliding-ring seal 17 by means of additional parts.

Similarly to the radial shaft seal in Figure 1, the sliding-ring seal 17 also has a reinforcing ring 22 which is vulcanized onto the inner peripheral surface 23 of the static sealing section. In the region of its peripheral surface 24, the reinforcing ring 22 is provided with circular or slightly oval openings 25 which are arranged staggered axially alternately with respect to one another. The ratio of the area of the openings 25 to the remaining material 26 is approximately equal in this case.

Figure 3 shows a valve-stem sealing ring 27 which, similarly to the preceding sealing rings, consists of a static sealing section 28 and a dynamic sealing section 29. The static sealing section 28 is reinforced in the region of its outer peripheral surface 30 by a cylindrical ring 31 which, as already described before, is provided in the region of its periphery 32 with openings 33 which are filled with the elastomeric or slightly plastic material of the static sealing section. The sealing ring 27 is forced axially onto the valve-stem guide 34 by means of follow-on tools (not shown). Without the openings 33 according to the invention in the reinforcing ring 31, it has been possible to bridge tolerances of 0.2 mm at the most, even with suitable profiling (e.g. wavy) of the static sealing section 28.With greater tolerances, for example 0.6 mm, the elastomer material would be displaced towards the sealing lip 29 when the seal 27 is forced axially onto the guide 34 and, depending upon the conformation of this zone (angular reinforcing ring), would pile up at that point and lead to the sealing ring 27 springing back axially and consequently not being seated correctly on the guide 34.

By introducing openings 33 into the reinforcing ring 31 in conjunction with giving suitable consideration to the area ratios, these disadvantages are avoided.

With a guide diameter of 11.86 mm and an inner sealing ring diameter of 11.24 mm (overlap 0.62 mm), a sealing ring ofthis kind may preferably be provided with eight circular openings with a diameter of about 4 mm in orderto be able to bridge the corresponding tolerance, the elastomeric or slightly plastic material of the static sealing section 28 being forced radially outwards with the formation of arched projections or convexities 35 when the seal 27 is forced on axially.

Claims (6)

1. Sealing ring, in particular a radial shaft seal, a sliding-ring seal or a valve-stem seal, with a static and a dynamic sealing section, the static sealing section being in the form of a gripping seat and consist ing of an elastomeric material bearing against the corresponding opposed surface of a receiving part, and with a cylindrical reinforcing ring which is arranged in the region of that peripheral surface of the gripping seat which faces away from the opposed surface and is provided with openings, characterised in that the webs (12) left between the openings (11,25,33) are of the same dimensions as, or of smaller dimensions than, the openings (11) as seen in the peripheral direction.

2. Sealing ring according to claim 1, characterised in that the axial width of the remaining peripheral zones (13, 14) is the same as, or smaller than, the openings (11).

3. Sealing ring according to claims 1 and 2, characterised in that the ratio of the area of the openings (25) to the remaining material (26) is approximately equal.

4. Sealing ring according to claims 1 to 3, having an angular reinforcing ring, characterised in that the peripheral zone (14) adjoining the bent-over side (15) is smaller in area as seen in the axial direction than the peripheral zone (13) remote from the bent-over side (15).

5. Sealing ring according to claims 1 to 4, characterised in that the openings (11, 25,33) have a circular cross-sectional profile.

6. Sealing ring according to claims 1 to 5, characterised in that the openings (25) are arranged staggered axially alternately with respect to one another.