GB1566584A

GB1566584A - Slide ring seal

Info

Publication number: GB1566584A
Application number: GB4217377A
Authority: GB
Original assignee: Kupfer Asbest Co
Current assignee: Kupfer Asbest Co
Priority date: 1976-10-26
Filing date: 1977-10-11
Publication date: 1980-05-08
Also published as: DE2648323A1; FR2369474A1; DE2648323B2; DE2648323C3; FR2369474B1

Description

(54) A SLIDE RING SEAL (71) We, KUPFER-ASBEST-CO. GUS- TAV BACH, an Offene Handelsgesellschaft of the Federal Republic of Germany, of 22 Rosenbergstrasse, 7100 Heilbronn, a.N., Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: The invention relates to a slide ring seal for sealing machine parts which are rotatable about an axis, more especially for sealing pump shafts, comprising an approximately rotationally symmetrical housing, which has at one front end a base extending transversely to the sealing axis, and comprising a primary seal, which is located in the interior of the housing and is designed as a sliding ring, and comprising a secondary seal, which is designed like a bellows and is also ring-shaped, as well as comprising a spring, which is arranged between the sliding ring and the base, and comprising an axial stop limitation for the sliding ring In order to ensure that the secondary seal which is in the form of a bellows and which usually is of an elastomeric material, has a sufficiently long service life, the secondary seal has to be kept in a substantially stress-free condition both in its installed position and during its storage time, which may be relatively long. The service life of the elastomeric seal can be considerably reduced by tensile and compressive stresses, since cracks are lible to form in places where internal mechanical stresses occur due to the action of ozone or aging during storage or in operation.

There are known slide ring seals of the kind mentioned at the beginning where the stop limiter is formed by a rubber lip encirculing the front end of the seal housing, axially closed grooves, bayonet-like grooves or closed window-like recesses in the housing, with the sliding ring striking against the rubber lip or cams of the slide ring engaging in the grooves or recesses. Slide ring seals where the stop limiters form a housing part are also known.

These known slide ring seals have the disadvantage that the stop limiter has to be placed to the front in the spring pressure direction to such an extent that the secondary seal can still be stretched by a specific amount in the axial direction during storage, so that it is constantly subjected to mechanical stresses during the relatively long storage time. Due to the formation of cracks, the service life of this seal is thus substantially reduced.The dimension by which the secondary seal can be stretched by the spring is composed of the provision for wear in the slide ring (at least 1 mm), the plus tolerance of the installation length (approximately 0,8 mm) and the part and fitting tolerances inherent in the slide ring seal (at least 0,5 mm) so that the stop is at least approximately 2,5 mm forward of the plane in which the secondary seal would be free from stresses in its installed position.

The task underlying the invention therefore is to design a slide ring seal of this kind in such a way that the secondary seal can be kept substantially free from stresses both in its installed position and during the storage time, i.e. the noninstalled configuration of the slide ring seal.

According to the invention, this task is solved in that a secondary seal is vulcanised in a position corresponding to its installed position and is held in this position by said stop limiter in the non-installed configuration of the slide ring seal, and in that said stop limiter is detachable from said slide ring seal.

Due to the releasable fastening of the stop limiter, this latter is located closer to the plane in which the secondary seal is vulcanised in its installed position by the amount of the provision for wear and the plus tolerance of the installation length of the slide ring seal. By this means, the secondary seal is alIowed to stretch relative to its stress-free position only by the small amount resulting from the tolerances inherent in the axial slide ring seal. However, this amount is so small that the secondary seal can be stored in a substantially stressfree manner and is thus subjected to a minimal amount of premature damage.

The stop limiter is advantageously automatically released by the pump shaft or the pressing-in tool prior to the slide ring seal being put into operation and can then be removed from the slide ring seal in a simple manner, for example by hand or by means of compressed air. By this means, no special constructional design of the stop limiter, for example for passing the slide ring through, is necessary so that this limiter can be produced in a simple and cheap manner. A substantial advantage consists in the fact that the stop limiter according to the invention can be arranged in a simple manner on already existing slide ring seals. Furthermore, the sliding surface of the slide ring is largely protected from damage or contamination by the stop limiter, so that no special precautions are necessary during transportation of storage.Furthermore, after having been removed from the slide ring seal the stop limiter can be fitted to other slide ring seals, thus allowing it to be used several times, which has considerable economic advantages, particularly when the stop limiter consists of a thermoplastic material.

It is particularly advantageous if the holding cap comprises on its base an axially extending plug-in projection, thus allowing the slide ring seals to be stacked in a simple manner in rolls by being inserted within one another.

Further features of the invention will emerge from the Sub-Claims, the description and the drawing.

The invention will be described in more detail with reference to several exemplified embodiments shown in the drawing, in which: - Fig. 1 shows a stop limiter of a slide ring seal according to the invention in an axial section, Fig. 2 shows a second constructional form of a stop limiter in a representation as in Fig. 1, Fig. 3 shows on the right-hand half a known slide ring seal and in the other half a slide ring seal according to the invention and comprising a stop limiter as shown in Fig. 1, but without a plug-in projection, in the fitted position and in an axial section.

Fig. 4 shows, in an axial section, in the right-hand half the slide ring seal which is shown in the left-hand half of Fig. 3 and is arranged in a pump housing, and in the left-hand half the slide ring seal shown in the right-hand half of Fig. 4 with the stop limiter detached from the housing, Fig. 5 shows, in an axial section, a third constructional form of a stop limiter according to the invention, Figs. 6 and 7 show, in axial sections, two further constructional forms of a stop limiter according to the invention, Fig. 8 shows, in an axial section, in the right-hand half a representation as shown in the right-hand half of Fig. 3 and in the lefthand half a slide ring seal according to the invention and comprising the stop limiter as shown in Fig. 7 in its fitted state, and Fig. 9 shows, in an axial section, the slide ring seal arranged in a pump housing and according to the left-hand half of Fig. 8 during the pressing-in operation by means of a pressing-in tool; in the left-hand half the slide ring seal according to the righthand half of Fig. 8 with the stop limiter separated from the housing.

The stop limiter shown in Figs. 1 to 9 are designed as holding caps and each comprise an upper stop and a lower stop for a slide ring located in a housing of the slide ring seal or for the housing itself. The holding cap shown in Fig. 1 consists of a jacket part 4 which is designed as a hollow cylinder and has a ring collar 3, encircling the area of its base 1 and forming an upper stop, and on which a lower stop for the housing of the slide ring seal is formed by a radially outwardly bent edge 5 of the opening 6 of the holding cap. In its fitted state, the holding cap lies with its jacket part 4 in an internal opening 24 or 44 of the housing 32 or 45 (Figs. 3 and 4).

In order to facilitate the introduction of the holding cap into the internal opening axially extending slots 8, which are separated by resiliently designed tongues 7, are provided in the lower area of the jacket part 4. As Fig. 1 shows, preferably four slots are provided. The edge 5 of the holding cap extends in its fitted state as far as the area of the base 33 of the housing 32 of the slide ring seal, its diameter being however only slightly larger than the clear width of the internal opening 24 or 44 of the housing 32 or 45.In this manner, it is ensured that the holding cap can be simply and automatically pressed from the internal opening 44 of the housing 45 by a shaft of a pump housing 43 before the slide ring seal is put into operation and can subsequently be removed from the pump shaft 42, for example by hand or by blowing with compressed air, as is shown particularly clearly in the left-hand half of Fig. 4. As Fig. 1 furthermore shows, the holding cap comprises an axially extending plug-in projection 2 which extends vertically to the base and to the ring collar located in one plane with the base. The plug-in projection passes over the entire width of the base of the holding cap and forms a stacking projection, so that a plurality of identically designed holding caps can be stacked in rolls for storage.

This allows the storage of the holding caps or the slide ring seals connected to the holding caps to be considerably simplified.

The ring collar 3 of the holding cap extends in the radial direction over more than the entire width of the slide ring 28 or 40, so that the sliding surface of the slide ring is protected from damage and contamination to a high degree during the storage of the slide ring seal.

In the constructional form of a holding cap according to the invention shown in Fig. 2, the base 11 is located at a distance from the ring collar 13 and the edge 15, its distance from the edge 15 being shorter than that from the ring collar 13. By this means, when the holding cap is removed by the pump shaft, it sits only over a rela tively small proportion of its length on this latter, allowing it to be removed or blown from the shaft in a particularly easy man ner. In this constructional form, the slots 18 extend between the spring tongues 17 as far as the area of the base 11. In contrast to the constructional form shown in Fig. 1, the holding cap shown in Fig. 2 does not comprise any plug-in projection.

The right-hand half of Fig. 3 shows a slide ring seal where a secondary seal 31, which is arranged between the slide ring 28 and the housing base 33 is vulcanised in its installed form and is designed as a bellows, is held in its mounted position by the force of a spring 30 which is also arranged in the housing. In this position, the bellows 31 is subjected to mechanical stresses, so that it is possible for cracks to form in the bellows, whereby its service life is considerably reduced. In this mounted position, an equilibrium of forces exists between the bellows 31 and the spring 30. In the left-hand half of Fig. 3, the afore-described slide ring seal is connected to a holding cap according to Fig.

1 but without any plug-in projection. In this position, the holding cap rests, with its edge 25, against the external surface of the base 33 of the housing 32. At the same time, the sliding surface 29 of the slide ring 28 is supported on the ring collar 23 of the holding cap. The distance be tween the edge and the ring collar of the holding cap corresponds to the length of the slide ring seal in its installed state. By this means, the bellows 31 is kept substantially free from stresses even during the storage of the slide ring seal, so that it does not become unusable prematurely due to mechanical stresses.

The right-hand half in Fig. 4 shows the slide ring seal with the holding cap according to the left-hand half in Fig. 3, the seal being pressed into a housing 43 of a pump not shown.

The left-hand half of Fig. 4 shows how the holding cap is released by means of the pump shaft 42 from the slide ring seal before the latter is put into operation.

The holding cap is pulled from the slide ring seal by the pump shaft in the axial direction and then lies loosely on the pump shaft, so that it can be easily removed by hand or by blowing by means of compressed air. Until being put into operation i.e. until an impeller (not shown) is pressed on the pump shaft 42, the bellows 41 is stretched for a short time by a spring 46 located in the housing 45, but is then compressed again to its installation length and thus kept free from stresses, when an impeller (not shown) is pressed on the pump shaft. As a result, the bellows 41 is subjected for a negligible short time, between the fitting of the pump shaft and the fitting of the impeller, to mechanical stresses which cannot cause any damage to the bellows.

Unlike the holding caps shown in Figs.

1 to 4, the holding caps according to the constructions shown in Figs. 5 to 9 overlap the slide ring seal only from the exterior and in so doing seal the slide ring seal front end that is opposite to the base of the housing. In these constructional forms, the sliding surface 99 of the slide ring 98 is supported on the base 51, 71, 81 and 91 respectively of the holding cap and the edge 102 or 111 of the slide ring housing 103 or 116 on a holding cap edge 56 or 76 or 119 bounding the cap opening.

As Fig. 5 shows, a holding cap comprises an axially extending plug-in projection 52, which is arranged coaxially to the holding cap axis, for the stacking of the slide ring seals. As Fig. 5 furthermore shows, the bottom 51 forms, with a shoulder 54 stepped at right angles, a jacket part of the holding cap. The jacket part has a conically outwardly directed shoulder surface 55, with which the jacket part merges, via an encircling detent recess 59, in a holding cap edge 56 designed as a lip. The edge 56 extends more steeply relative to the axis of the holding cap than the shoulder surface 55 does. The wall 60 of the detent recess 59 forms with the internal surface 57 of the edge 56 a contact surface for the edge 102 or 111 of the housing 103 or 116 of the slide ring seal (Figs. 8 and 9).Due to the conical design of the edge 56, the mounting of the holding cap on the housing 103 or 116 of the slide ring seal is substantially facilitated.

The exemplified embodiment of a holding cap according to the invention shown in Fig. 6 comprises a plug-in projection 72 which, unlike that of the constructional form shown in Fig. 5, is open in the area of the base, so that a passage is formed.

This allows the slide ring seal according to the invention to be installed in the pump housing even when the pump shaft is already fitted. Furthermore, there are provided four axially extending slots 73 extending over the edge 76 and the detent recess 79 of the holding cap, so that the fitting and dismantling of the holding cap is substantially facilitated, due to the greater movability of the edge 76.

In Fig. 7, another constructional form of a holding cap is shown, whose base 81 is continuously closed over its entire width and is designed without a plug-in projection.

In the left-hand half of Fig. 8, the slide ring seal is shown according to the righthand half of Fig. 8 and the right-hand half of Fig. 3, with the holding cap fitted. The edge 102 of the housing 103 of the slide ring seal has a very secure fit in the detent recess 109 of the holding cap. The distance of the holding surface 108 of the detent recess 109 from the opposite inside of the base 91 of the holding cap is such that the bellows 101 is kept substantially free from stresses in the later installed position of the slide ring seal.

The right-hand half of Fig. 9 shows the dismantling of the holding cap of the slide ring seal shown in the left-hand half of Fig. 8 by means of a pressing-in tool 115.

As shown in Fig. 9, the holding cap rests with its edge 119 on the associated front face 114 of a pump housing 113, the pressing in tool resting on the holding cap in the area of the shoulder surface 125 thereof. As the pressing-in tool advances, the edge 119 of the holding cap performs a swivel movement about a tangent to the edge 111 of the housing 116. The edge 119 swings outwards to such an extent until it rests flatly against the front surface 114 of the pump housing 113. In this position, the holding cap releases the housing 116 of the slide ring seal, its edge 111 sliding from the detent recess 139.The detachment of the holding cap from the slide ring seal housing is facilitated by the conical design of the holding cap edge, since the shoulder surface 125 flatly abuts the edge 111 of the housing 116 of the slide ring seal when the slide ring seal is pressed in, causing the diameter of the detent recess 139 to be enlarged.

When the pressing-in tool 115 is withdrawn from the slide ring seal, the edge 119 resumes its original conical form, if the holding cap consists of an elastic material, the' edge being supported on the associated front surface 114 of the pump housing.

Furthermore, the lifting of the holding cap is supported by the slide ring seal spring 110 which is now released. The holding cap can now be lifted from the slide ring seal in a simple manner. The holding cap may consist of a metallic material or else a nonmetallic material. However, it preferably consists of a material which has a certain elasticity.

WHAT WE CLAIM IS: 1. A slide ring seal for sealing machine parts which are rotatable about an axis, comprising an approximately rotationally symmetrical housing, which has at one front end a base extending transversely to the sealing axis, and comprising a primary seal, which is located in the housing interior and is in the form of a slide ring, and a secondary seal, which is in the form of a bellows and is also ring-shaped, as well as comprising a spring arranged between the slide ring and the base and comprising an axial stop limiter for the slide ring, characterised in that the secondary seal (31, 41, 101) is vulcanised in a position corresponding to its installed position and is held in this position by said stop limiter in the non-installed configuration of said slide ring seal, and in that said stop limiter is detachable from said slide ring seal.

2. A slide ring seal as claimed in claim 1, characterised in that the stop limiter is designed as a holding cap having a base and which overlaps the housing 32, 45, 103, 116) at least partially and is preferably rotationally symmetrical and consists of a resilient material.

3. A slide ring seal as claimed in claim 2, characterised in that the housing (32, 45) is penetrated by a jacket part (4) of the holding cap.

4. A slide ring seal as claimed in Claim 2 or Claim 3, characterised in that the holding cap overlaps the housing (103, 116) only externally.

5. A slide ring seal as claimed in any one of Claims 2 to 4, characterised in that the holding cap comprises an upper stop (3, 13, 24, 51, 71, 81, 91) and a lower stop (5, 15, 56, 76, 119).

6. A slide ring seal as claimed in Claim 5, characterised in that the upper stop (3, 13, 23) is formed by a ring collar which is approximately perpendicular to the holding cap axis and is preferably located in a plane with the base (1) of the holding cap or at a distance above the base of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. surface for the edge 102 or 111 of the housing 103 or 116 of the slide ring seal (Figs. 8 and 9). Due to the conical design of the edge 56, the mounting of the holding cap on the housing 103 or 116 of the slide ring seal is substantially facilitated. The exemplified embodiment of a holding cap according to the invention shown in Fig. 6 comprises a plug-in projection 72 which, unlike that of the constructional form shown in Fig. 5, is open in the area of the base, so that a passage is formed. This allows the slide ring seal according to the invention to be installed in the pump housing even when the pump shaft is already fitted. Furthermore, there are provided four axially extending slots 73 extending over the edge 76 and the detent recess 79 of the holding cap, so that the fitting and dismantling of the holding cap is substantially facilitated, due to the greater movability of the edge 76. In Fig. 7, another constructional form of a holding cap is shown, whose base 81 is continuously closed over its entire width and is designed without a plug-in projection. In the left-hand half of Fig. 8, the slide ring seal is shown according to the righthand half of Fig. 8 and the right-hand half of Fig. 3, with the holding cap fitted. The edge 102 of the housing 103 of the slide ring seal has a very secure fit in the detent recess 109 of the holding cap. The distance of the holding surface 108 of the detent recess 109 from the opposite inside of the base 91 of the holding cap is such that the bellows 101 is kept substantially free from stresses in the later installed position of the slide ring seal. The right-hand half of Fig. 9 shows the dismantling of the holding cap of the slide ring seal shown in the left-hand half of Fig. 8 by means of a pressing-in tool 115. As shown in Fig. 9, the holding cap rests with its edge 119 on the associated front face 114 of a pump housing 113, the pressing in tool resting on the holding cap in the area of the shoulder surface 125 thereof. As the pressing-in tool advances, the edge 119 of the holding cap performs a swivel movement about a tangent to the edge 111 of the housing 116. The edge 119 swings outwards to such an extent until it rests flatly against the front surface 114 of the pump housing 113. In this position, the holding cap releases the housing 116 of the slide ring seal, its edge 111 sliding from the detent recess 139.The detachment of the holding cap from the slide ring seal housing is facilitated by the conical design of the holding cap edge, since the shoulder surface 125 flatly abuts the edge 111 of the housing 116 of the slide ring seal when the slide ring seal is pressed in, causing the diameter of the detent recess 139 to be enlarged. When the pressing-in tool 115 is withdrawn from the slide ring seal, the edge 119 resumes its original conical form, if the holding cap consists of an elastic material, the' edge being supported on the associated front surface 114 of the pump housing. Furthermore, the lifting of the holding cap is supported by the slide ring seal spring 110 which is now released. The holding cap can now be lifted from the slide ring seal in a simple manner. The holding cap may consist of a metallic material or else a nonmetallic material. However, it preferably consists of a material which has a certain elasticity. WHAT WE CLAIM IS:

1. A slide ring seal for sealing machine parts which are rotatable about an axis, comprising an approximately rotationally symmetrical housing, which has at one front end a base extending transversely to the sealing axis, and comprising a primary seal, which is located in the housing interior and is in the form of a slide ring, and a secondary seal, which is in the form of a bellows and is also ring-shaped, as well as comprising a spring arranged between the slide ring and the base and comprising an axial stop limiter for the slide ring, characterised in that the secondary seal (31, 41, 101) is vulcanised in a position corresponding to its installed position and is held in this position by said stop limiter in the non-installed configuration of said slide ring seal, and in that said stop limiter is detachable from said slide ring seal.

holding cap (Fig. 2).

7. A slide ring seal as claimed in Claim 5, characterised in that the upper stop (51) is formed by the base of the holding cap.

8. A slide ring seal as claimed in any one of Claims 5 to 7, characterised in that the lower stop (5, 15, 25, 56, 76, 119) is formed by an edge of the holding cap opening (6) which is directed towards the exterior transversely to the holding cap axis.

9. A slide ring seal as claimed in Claim 8, when dependent upon Claim 6 characterised in that the edge (5, 15, 25) extends approximately parallel to the ring collar (3, 13, 23), and in that the holding cap extends with its edge as far as the area of the housing base (33) and in that the distance between the ring collar (3, 13, 23) and the edge (5, 15, 25) of the holding cap is equal to the installation length of the slide ring seal.

10. A slide ring seal as claimed in Claim 8, when dependent upon Claim 6 characterised in that the ring collar (3, 13, 23) radially projects from the edge (5, 15, 25) of the holding cap and in that the ring collar (3, 13, 23) preferably extends over at least the entire width of the slide ring (28, 40).

11. A slide ring seal as claimed in any one of Claims 2 to 10, characterised in that the base (51, 71, 81, 91) of the holding cap comprises a stepped shoulder (54), one shoulder surface (55, 125) of which bounds, with the preferably conically designed edge of the cap opening (56, 76, 119), an en circling detect recess (59, 79, 109, 139) for an upper edge (102, 111) of the housing (103, 116) (Figs. 5 to 9), the inside width of the recess preferably being equal to the outside diameter of the edge (102, 111) of the housing (103, 116).

12. A slide ring seal as claimed in any one of Claims 2 to 11, characterised in that in the sealed position of the holding cap the base thereof (51, 71, 81, 91) has a distance from the housing base (112) that corresponds to the installed length of the slide ring seal.

13. A slide ring seal as claimed in Claim 3, characterised in that the packet part (4) comprises, at least in the area of the edge (5, 15, 25) of the holding cap, axially extending slots (8, 18) so that resilient tongues (7, 17, 27) are formed between the slots.

14. A slide ring seal as claimed in any one of Claims 2 to 13, characterised in that the holding cap comprises at its base (1, 51, 71) an axially extending plug in projection (2, 52, 72) which preferably forms, with a cap opening, a passage for a shaft or the like.

15. A slide ring seal substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.