EP0293431A1

EP0293431A1 - Rotary seal

Info

Publication number: EP0293431A1
Application number: EP88900003A
Authority: EP
Inventors: Rowland Thomas Dixon
Original assignee: SEALING DEVICES Pty Ltd
Current assignee: SEALING DEVICES Pty Ltd
Priority date: 1986-12-03
Filing date: 1987-12-01
Publication date: 1988-12-07
Also published as: FI883595A; NZ222763A; FI883595A0; WO1988004379A1; DK430688A; DK430688D0; EP0293431A4

Abstract

Un assemblage de joint d'étanchéité, destiné à former un joint rotatif entre un élément d'arbre et une ouverture ménagée dans la paroi d'un récipient sur les côtés de laquelle s'exercent des pressions de fluide différentes, comprend un logement annulaire en forme de plaque (1) et un manchon (2) inséré dans ledit logement et pouvant tourner autour de son axe. Le logement (1) peut être fixé à une paroi dans le récipient. Le manchon comporte une rainure (4) dans laquelle peut s'adapter la base (5) d'un élément de joint annulaire (6), empêchant ainsi la partie de base de l'élément de joint d'effectuer un mouvement axial en direction d'une partie de face plane lisse (8) d'une bague amovible (9) en matériau poli dur, qui est scellée dans le logement par un joint torique (10) de façon à empêcher toute fuite, mouvement qui se produirait sans cela sous l'effet de la pression de fluide s'exerçant sur l'élément de joint (6). Une partie marginale (7) du joint d'étanchéité (6) appuie de façon étanche contre la partie de face plane lisse (8) et est destinée à être pressée contre la face lisse de ladite partie sous l'action de la pression de fluide, de façon à former ledit joint d'étanchéité rotatif. Dans la paroi intérieure du manchon (2) sont disposés une rainure (11) et un joint torique (12) qui coopèrent afin de former un joint d'étanchéité entre le manchon (2) et un arbre qui peut être inséré dans ledit manchon.A seal assembly, intended to form a rotary seal between a shaft element and an opening formed in the wall of a container on the sides of which different fluid pressures are exerted, comprises an annular housing in form of plate (1) and a sleeve (2) inserted in said housing and able to rotate about its axis. The housing (1) can be fixed to a wall in the container. The sleeve has a groove (4) in which the base (5) of an annular seal element (6) can be fitted, thereby preventing the base part of the seal element from making an axial movement in the direction a smooth flat face part (8) of a removable ring (9) of hard polished material, which is sealed in the housing by an O-ring (10) so as to prevent any leakage, movement which would otherwise occur under the effect of the fluid pressure exerted on the seal element (6). A marginal part (7) of the seal (6) presses tightly against the smooth flat face part (8) and is intended to be pressed against the smooth face of said part under the action of the fluid pressure , so as to form said rotary seal. In the inner wall of the sleeve (2) are arranged a groove (11) and an O-ring (12) which cooperate to form a seal between the sleeve (2) and a shaft which can be inserted into said sleeve.

Description

ROTARY SEAL

This invention relates to rotary seals and in particular seals between a rotating shaft member and a housing of a pressure vessel or pump or the like or a vaccum pump, in which there are different fluid pressures on opposite sides of the wall of the vessel. Such fluids may include, as well as liquids and gases, slurries such as concrete mixes and those incorporating various process chemicals. Stuffing box arrangements are used to prevent leakage along a piston rod, propeller shaft, or other moving part passing through a hole in a cylinder or other vessel containing steam, water or oil. A stuffing box consists of a box or chamber and a gland arranged to compress packing material which seals around the moving part. Alternatively, a simple circular seal has been applied around a rotating shaft, the pressure of the fluid inside the vessel urging the seal to establish a sealing effect between the rotating shaft and the internal face around the hole through which the shaft passes.

More complicated seal arrangements are described in U.S. Patents 4465285, 4437673 and 2990220, and also in GB Patent 1559267. These have the disadvantage of being unduly complicated. According to the present invention there is provided a seal assembly comprising first and second seal members and a shaft member, wherein one of said seal members is adapted to be sealingly mounted on the shaft member and the other of said seal members is adapted to be sealingly mounted around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of said vessel, the shaft passing through said opening, wherein the first and second seal members co-operate to establish a rotary seal between the shaft member and the wall of the said vessel, one of the seal members providing a seat having a smooth flat face region, the other seal member comprising a lip portion which sealingly abuts the smooth face region of the seat and is adapted to be urged against said smooth face under the differential fluid pressure so as to establish said rotary seal, the seal assembly further comprising restraining means for engaging a base portion of the seal member having said lip portion to restrain it from axial movement towards said face region of the seat which movement would otherwise occur by virtue of fluid pressure on^' the seal member having said lip portion.

According to a further aspect of the present invention, there is provided a seal assembly comprising a housing seat, a shaft member and a seal member adapted to be mounted on the shaft member and to establish a rotary seal between the shaft member and the housing seat, wherein the housing seat is removably and sealingly attachable around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of said vessel, the housing seat having a hole therethrough which accommodates the shaft member rotatably therein, the housing seat having a smooth flat face region extending away from and around the hole on the side of the housing seat facing the higher pressure, the shaft member having restraining means for engaging a base portion of the seal member and restraining_^ it from axial movement towards said face region which movement would otherwise occur by virtue of fluid pressure on the seal member, the seal member further comprising a lip portion which sealingly abuts the smooth face region of the housing seat and is adapted to be urged against said smooth face thereof under fluid pressure so as to establish said rotary seal.

Preferably the housing seat is fitted and sealed directly about an opening in the wall of the vessel by means of a static rubber seal. This embodiment is particularly suitable for use in new equipment where the seat can be installed directly in the vessel wall.

Alternatively the housing seat may be fitted and sealed in a housing, wherein the housing is removably and sealingly attachable around an opening in the vessel wall. This particular embodiment is particularly suitable for use in existing equipment as a replacement for a worn seal arrangement or stuffing box. Preferably, the shaft member will have shoulder means which act as the restraining means for the base portion of the seal member. Such shoulder means are preferably provided in the form of a groove around the periphery of the shaft. Alternatively, the shoulder may be provided by a collar mounted on the shaft.

With advantage the shaft member may consist of a sleeve with shoulder means, through which a shaft may be inserted. In conjunction with a housing as described above, the use of a sleeve has the advantage of providing a sealing arrangement for any rotatable shaft, such arrangement being used as a substitute for a stuffing box on existing equipment.

Such a sleeve may have a threaded bore therethrough so that a suitable grub screw can be used for securing the sleeve to a shaft. In this instance a seal between the sleeve and the shaft proper may be accomplished by use of a conventional O-ring seal.

Alternatively the restraining means may be provided by the seal member being glued or bonded directly to the shaft or glued or bonded to a sleeve which is attached by means of a grub screw to the shaft and sealed with an O-ring as described above.

Alternatively the restraining means may be provided by a collar which has a lip extending into a groove provided in the base portion of the seal, the collar being screwed to the shaft by means of suitable grub screws thereby restraining the seal from axial movement towards the flat surface of the seat. According to another aspect of the present invention there is provided a seal assembly comprising a seal member, a shaft member and a seal seat member adapted to be mounted on the shaft member and to establish a rotary seal between the shaft member and the seal member, wherein the seat member is removably and sealingly attachable around the shaft member, the seat member having a smooth flat face region extending away from and around the shaft, and the seal member is sealingly attachable around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of the vessel, the seal member having a hole therethrough which accommodates the shaft member rotatably therein, the wall of the pressure vessel having restraining means for engaging a base portion of the seal member and restraining it from axial movement towards said face region which movement would otherwise occur by virtue of fluid pressure on the seal member, the seal member further comprising a lip portion which sealingly abuts the smooth face region of the seat member and is adapted to be urged against said smooth face thereof under fluid pressure so as to establish said rotary seal.

In a typical embodiment utilizing a housing and sleeve, with a seal size for example about 38mm diameter, a preload or compression of about 1.5mm deflection of the seal lip in the axial direction is provided. With advantage two or more grub screws may then be employed to secure the sleeve to the shaft. Other suitable means of securing the sleeve may be used. Before fitting, the grub screws will be located in the upper portion of their respective threaded bores and "the heads of the screws will extend into access holes in the housing. In this position the heads of the grub screws will restrain the sleeve from axial movement thereby maintaining the preload or compression. On fitting the sleeve to a shaft, each grub screw will be tightened down onto the shaft in turn so that the preload can be maintained. In other words tightening the first screw will secure the sleeve to the shaft, whilst the second and any other screws will maintain the sleeve in the correct position relative to the housing. When securement to the shaft has been effected the second and any subsequent screws can be tightened thereby releasing the sleeve from its retained position within the housing, so that it will be free to rotate within the housing. The sleeve will however still be restrained from axial movement by virtue of its securement to the shaft.

With advantage a double seal arrangement may be employed wherein the second seal acts against a second face surface located rearwards of the first face. For illustrative purposes only, embodiments of the invention will now be described with reference to the accompanying drawings of which:

Figure 1 is a section through a seal assembly utilizing a housing, according to the present invention; Figure 2 is a section through an embodiment of the invention utilizing a housing and comprising a double seal;

Figure 3 is a section through an embodiment of a seal assembly according to the present invention without a housing or sleeve;

Figure 4 is a section through another embodiment employing a collar;

Figure 5 is a section through a further embodiment employing a seal glued to a sleeve; Figure 6 is a section through yet another embodiment employing a different collar; and

Figure 7 is a section through an embodiment employing the seal and seat in opposite relationship to those embodiments in Fig. 1 to 6, namely with the seal mounted in the wall and the seat mounted^' on the shaft.

The seal assembly shown in the Fig. 1 comprises an annular plate-like housing 1, and a sleeve 2 inserted therethrough, the sleeve 2 being rotatable about its axis 3. The housing is attachable to a wall in a pump or like vessel by means of bolts which may be inserted through holes (not shown) in the area adjacent the periphery of housing. A gasket may be employed to seal against leakage. The sleeve has a groove 4 which accommodates the base 5 of an annular seal member 6 of impregnated synthetic rubber material. Preferably the axial dimension of the groove 4 will be narrower by about- a 10% than the width of the base 5 of the seal 6, in its relaxed state. Preferably the internal radius of the seal 6 will be less than the radius of the base of the groove 4. When the seal member 6 is expanded radially to fit the groove a certain narrowing of the base portion will occur, and when fitted to the groove 4, the base portion 5 will expand axially thereby causing axial pressure with consequent improvement of fit and seal. A lip portion 7 of the seal 6 sealingly abuts a smooth flat face portion 8 in the housing 1, a preload or compression caused by deflection of the seal lip in the axial direction being provided. The smooth flat face portion 8 is conveniently the outer face of a removable ring 9 of a hard polished material, which is sealed against leakage by the use of O-ring 10.

In the internal wall of the sleeve 2 there is provided a groove 11 and O-ring 12 which co-operate to provide a seal between the sleeve 2 and a shaft which may be inserted therethrough.

A threaded bore 13 is provided through the sleeve 2 in which a grub screw (not shown) is engaged to hold the sleeve 2 on the shaft. Before fitting, the grub screw will be located in the upper portion of the threaded bore 13 and the head of the screw will extend into the access hole 19 in the housing 1 (when bore 13 and hole 19 are brought into radial alignment) . In this position the head of the grub screw will, restrain the sleeve 2 from axial movement^' hereby maintaining the preload or compression.

On fitting the sleeve 2 to a shaft, the grub screw will be tightened down onto the shaft, whilst the second and any other screws (located radially around the sleeve 2) will maintain the sleeve in the correct position relative to the housing 1.

When securement to the shaft has been effected the second and any subsequent screws can be tightened thereby releasing the sleeve 2 from its retained position within the housing 1, so that it will be free to rotate. The sleeve 2 will however still be restrained from axial movement by virtue of its securement to the shaft. Access to the access hole 19 is achieved by a cutaway portion 20 in the body of the housing 19.

A drainage cavity 14 is provided in the housing 1 to allow any fluid which does seep past the seal 6 to be removed.

Fig. 2 shows a second embodiment with a housing and sleeve, which embodiment incorporates a pair of seal members. The components which are common to those of Fig. 1 are labelled using the same identifying numerals. A base portion 5a of second seal 6a is fitted in a second groove 4a in sleeve 2. The lip portion 7a of seal 6a abuts a smooth face portion 8a which is the outer face of a second removable ring 9a of hard polished material. An O-ring 10a seals against leakage, the O-ring 10a and ring 9a being held in place by an annular plate 15 held onto the housing 1 by a bolt inserted through threaded hole 16. Drainage cavity 14 in this embodiment leads to an annular chamber 17 located between seals 6 and 6a. When used in conjuntion with a second drainage cavity on the opposite side of the shaft (not shown), the first drainage cavity may be conveniently used as a cavity for introducing flushing liquid to keep the chamber 17 clear of any unwanted fluid or debris. Cavity 14 is provided with a threaded portion 18 for attachment of a hose for drainage and flushing.

The seal assembly shown in Fig. 3 is without a housing or sleeve and comprises a shaft 19 inserted through a hole 20 in the wall 21 of a vessel, the shaft 19 being rotatable therein. The shaft has a groove 22 which accomodates the base of an annular seal member 23 as described in reference to seal member 6 in groove 4 of Fig. 1

A lip portion 24 of the seal member 23 sealingly abuts a smooth flat face portion 25 of a ceramic ring 26 which acts as a seat for seal 23. Ceramic ring 26 is sealingly mounted in a rebate 27 of the wall 21 of the vessel, by means of an annular rubber seal 28. In use a preload or compression caused by deflection of the seal lip in the axial direction is provided, the shaft 19 being itself restrained from axial movement by virtue of its location in bearings not shown. Figures 4, 5 and 6 each illustrate a variation on the way in which the seal member 23 can be restrained from axial movement towards the face 25 of the seat 26. For convenience the components which are common to Fig. 3 are labelled using the same identifying numerals. In Fig. 4 seal 23 is restrained from axial movement by means of a collar 29 fixed to shaft 19 by means of a grub screw through hole 30. In Fig. 5, seal 23 is bonded by glue to sleeve 31 which is likewise fixed to shaft 19 by a grub screw through hole 32. A seal in the form of an O-ring 33 in groove 34 provides against leakage.

In Fig. 6 the modified seal 23 has a groove in the rear portion of its base into which a lip 36 of a collar 37 is inserted. On fixing the collar 37 to shaft 19 the seal 23 is restrained from axial movement.

In Fig. 7 there is provided an assembly in which the seal 39 is fitted to the wall 40 of a vessel. The seal 39 is restrained by means of lip 41 provided in wall 40. A lip portion 42 sealingly abuts smooth flat face 43 of seat member 44, which is sealingly attached to the shaft 45 by means of static seal 46. The seat 44 and seal 46 are restrained from movement by impeller 47 mounted on shaft 45. Unlike the previous embodiments of Fig. 1 to 6, the seal and seat are transposed so that on rotation of shaft 45 it is seat 44 which rotates rather than seal 39.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A seal assembly comprising first and second seal members and a shaft member, wherein one of said seal members is adapted to be sealingly mounted on the shaft member and the other of said seal members is adapted to be sealingly mounted around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of said vessel, the shaft passing through said opening, wherein the first and second seal members co-operate to establish a rotary seal between the shaft member and- the wall of the said vessel, one of the seal members providing a seat having a smooth flat face region, the other seal member comprising a lip portion which sealingly abuts the smooth face region of the seat and is adapted to be urged against said smooth face under the differential fluid pressure so as to establish said rotary seal, the seal assembly further comprising restraining means for engaging a base portion o-f the seal member having said lip portion to restrain it from axial movement towards said face region of the seat which movement would otherwise occur by virtue of fluid pressure on the seal member having said lip portion.

2. A seal assembly comprising a housing seat, a shaft member and a seal member adapted to be mounted on the shaft member and to establish a rotary seal between the shaft member and the housing seat, wherein the housing seat is removably and sealingly attachable around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of said vessel, the housing seat having a hole therethrough which accommodates the shaft member rotatably therein, the housing seat having a smooth flat face region extending away from and around the hole on the side of the housing seat facing the higher pressure, the shaft member having restraining means for engaging a base portion of the seal member and restraining it from axial movement towards said face region which movement would otherwise occur by virtue . of fluid pressure on the seal member, the seal member further comprising a lip portion which sealingly abuts the smooth face region of the housing seat and is adapted to be urged against said smooth face thereof under fluid pressure so as to establish said rotary seal.

3. A seal assembly according to claim 2 in which the housing seat is fitted and sealed directly about an opening in the wall of the vessel by means of a static rubber seal.

4. A seal assembly according to claim 2 in which the housing seat may be fitted and sealed in a housing, wherein the housing is removably and sealingly attachable around an opening in the vessel wall.

5. A seal assembly according to any one of claims 2 to 4 in which the shaft member has shoulder means which act as the restraining means for the base portion of the seal member.

6. A seal assembly according to claim 5 in which the shoulder means are provided in the form of a groove around the periphery of the shaft.

7. A seal assembly according to claim 5 in which the shoulder means are provided by a collar mounted on the shaft.

8. A seal assembly according to claim 5 in which the shaft member consists of a sleeve with the shoulder means provided therein, through which a shaft may be inserted.

9. A seal assembly according claim 8 in which the sleeve has a threaded bore therethrough so that a suitable grub screw can be used for securing the sleeve to the shaft.

10. A seal assembly according to any one of claims 2 to 4 in which the restraining means is provided by the seal member being glued or bonded directly to the shaft.

11. A seal assembly according to any one of claims 2 to 4 in which the restraining means is provided by the seal member being glued or bonded directly to a sleeve which is attached by means of a grub screw to the shaft. .

12. A seal assembly according to any one of claims 2 to 4 in which the restraining means is provided by a collar which has a lip extending into a groove provided in the base portion of the seal, the collar being secured to the shaft by means of a grub screw.

13. A seal assembly according to claim 4 in which the shaft member consists of a sleeve, the restraining means is provided by shoulder means in the form of a groove around the periphery of the sleeve, and there is provided a preload or compression of about 1.5mm deflection of the seal lip in the axial direction towards the smooth face region of the housing seat.

14. A seal assembly according to claim 13 in which two or more grub screws are employed to secure the sleeve to the shaft.

15. A seal assembly according to any one of claims 2 to 14 in which there is provided a double seal arrangement wherein a second seal member acts against a smooth face region of a second housing seat located rearwards of the face region of the first housing seat.

16-. A seal assembly comprising a seal member, a shaft member and a seal seat member adapted to be mounted on the shaft member and to establish a rotary seal between the shaft member and the seal member, wherein the seat member is removably and sealingly attachable around the shaft member, the seat member having a smooth flat face region extending away from and around the shaft, and the seal member is sealingly attachable around an opening in the wall of a vessel which in use has different fluid pressures on opposite sides of said wall of the vessel, the seal member having a hole therethrough which accommodates the shaft member rotatably therein, the wall of the pressure vessel having restraining means for engaging a base portion of the seal member and restraining it from axial movement towards said face region which movement would otherwise occur by virtue of fluid pressure on the seal member, the seal member further comprising a lip portion which sealingly abuts the smooth face region of the seat member and is adapted to be urged against said smooth face thereof under fluid pressure so as to establish said rotary seal.

17. A seal assembly according to claim 16 in which the housing seat is fitted and sealed directly about the shaft by means of a static rubber seal.

18. A seal assembly according to either claim 16 or 17 in which the opening in the wall of the vessel has shoulder means which act as the restraining means for the base portion of the seal member.

19. A seal assembly according to either claim 16 or 17 in which the restraining means is provided by the seal member being glued or bonded directly in the opening of the wall of the vessel.

20. A seal assembly substantially as described herein in conjunction with any one of the figures.