GB2030236A

GB2030236A - Rotary seal

Info

Publication number: GB2030236A
Application number: GB7920683A
Authority: GB
Original assignee: IAO Industrie Riunite SpA
Current assignee: IAO Industrie Riunite SpA
Priority date: 1978-07-07
Filing date: 1979-06-14
Publication date: 1980-04-02
Also published as: FR2430555B1; DE2926207A1; IT7868611A0; ES244383U; FR2430555A1; ES244382U; ES244381U; ES244381Y; ES244382Y; IT1108623B; ES244383Y

Abstract

A sealing device comprising a diaphragm 18 (A-A''), carrying a lipped sealing ring 20 and having a skirt 18A, and a cap 26 which is rotatable with a shaft 10. The lips 22 and 24 of ring 20 seal against hub portion 26B of cap 26 to prevent leakage of lubricant and ingress of moisture and dirt, respectively. Stop means, such as lugs 18A'', are provided to prevent separation of the cap 26 from the diaphragm 18. Clearances 28, 30 and 32 between the cap and the diaphragm are such as to restrict relative movement therebetween in order to prevent damage to the lips 22 and 24. The stop means may alternatively comprise a ring (Fig. 6) fitted into a groove. In other embodiments one or both seal lips may bear on the face of an annular disc part 26A of the cap. <IMAGE>

Description

SPECIFICATION Rotary seal This invention relates to a sealing device for rotary shafts, comprising a rigid annular diaphragm, an external peripheral face of which forms a cylindrical skirt which extends in one axial direction, and a lipped sealing ring of flexible material arranged on an internal peripheral edge of the diagram.

By the term "rotary shaft" herein is meant not only a true shaft, but also any member which is capable of revolving in an opening of a fixed member, into which such a sealing device is fitted. Thus, forthe purposes of the present invention, the term "rotary shaft" also includes, for example, the internal ring of a roller bearing, the external ring of which then represents the above mentioned fixed member.

The lipped sealing ring, forming part of the sealing device, may have one ortwo peripheral lips. Rings with two lips are preferred, one of which projects towards the inside of the mechanical unit housing the rotary shaft (for example towards the ball housing in the case of the ball bearing) to prevent the lubricant from leaving said unit,whilstthe other lip projects towards the outside to prevent the entry of foreign material, such as water, dust or mud. In the currently known devices, the lip (or each lip) has a sharp edge, which is in continuous linear contact with the circumference of the rotary shaft under the effect of a well determined radial pressure produced by the elastic force of the lip. Therefore, the lip with its contact edge forms an extremely delicate part.In fact, even the slightest interruption of the said continuous linear contact seriously prejudices the effectiveness of the device. Moreover, very often in the initial assembly or during repair of the device, the lip may undergo a local turning up, or a turning up over the whole circumference, when the device is inserted onto the shaft, with a resulting loss of sealing.

According to the present invention there is provided a sealing device, for a rotary shaft, comprising a rigid annular diaphragm having an external peripheral face forming a cylindrical skirt which extends in one axial direction and an internal peripheral edge on which a lipped sealing ring of flexible material is arranged, and an annular cap in sealing contact with the lipped sealing ring, said cap having an annular disc part whose external peripheral edge penetrates with radial clearance the space surrounded by the skirt and a cylindrical hub part which extends axially from the internal circumference of said disc part in the opposite axial direction to said skirt, and wherein stop means are provided for preventing separation of the cap from the diaphragm.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 shows, in partial section, a first embodiment of sealing device mounted in position on an associated shaft; Fig. 2 shows, in partial section, a second embodiment unmounted; Fig. 3 shows the embodiment of Fig. 2 mounted in position on a shaft; Fig. 4 shows, in partial section, a third embodiment unmounted; Fig. 5 shows the embodiment of Fig. 4 mounted in position on a shaft, and Fig. 6 shows a fifth embodiment.

In Fig. 1, 10 indicates a rotary shaft, mounted in a fixed support 12 by means of a ball bearing 14. The support 12 may be formed, for example, by a casing of a gear box, whose face 12' is exposed to the external environment, and which contains lubricating oil which bathes the bearing 14.

The sealing device, is shown, as a whole, at 16. It has a rigid annular diaphragm 18 stamped from sheet metal in one piece with a cylindrical, peripheral skirt 18A. When in use, the skirt 18A is force-fitted into bore 12" in support 12 in such a way that free edge 18A' of the skirt is turned towards the outside and, for preference, it should be approximately flush with the face 12' of the support 12. On the internal peripheral edge of diagram 18 a flexible rubber or polymeric sealing ring 20 is arranged in known manner, ring 20 having a sealing lip 22 turned obliquely in the opposite direction to that of skirt 18A and a sealing lip 24 turned obliquely in the same direction as the skirt 18A.

Numeral 26 shows, as a unit, a cap pressed in sheet metal and having an annular disc part 26A and a cylindrical tubular hub part 26B. The external and internal cylindrical surfaces of the hub 26B are perfectly circular and smooth and the axial length of the hub is, with advantage, equal to the axial length of the skirt 18A. In the illustrated position for use, the hub 26B is force-fitted to seal on shaft 10 in such a way that the external front face of disc 26A is flush with face 12' of support 12. In order to obtain this positioning it is sufficient to arrange a thrusting member (not illustrated) having a flat front face to apply the axial thrust at the same time to the disc 26A and to the free edge 18A' of the skirt 18A until the said flat face is stopped by face 12' of support 12.

An external peripheral zone 26C of disc 26A is re-entrant and connects with a cylindrical crown 26D, directed towards diaphragm 18 and forming a radial clearance 28 with skirt 18A. As is seen in Fig. 1, lips 22, 24 are both in a sealing relationship with the external cylindrical surface of the hub 26B. It is also seen that in the absence of shaft 10, cap 26 may be in floating position in relation to diaphragm 18, with the apparent risk of damaging lips 22,24 if the radial displacement of the cap is not conveniently limited.

In effect, the said radial clearance 28 is sufficiently small to prevent excessive deforming of lips 22, 24 through the said radial displacement of the cap.

From the free edge 18A' of the skirt 18A retaining lugs 18A" are punched radially inwards to a depth above that of the radial clearance 28, and these lugs are distributed uniformly (these may be, for exam ple, 6) on the circumference of said edge. Thus, even in free conditions of the device, the separation of the cap 26 from the remaining parts of the device is prevented because the lugs 18A" form the axial stops for crown 26D. It is seen in the Fig. 1 that, in the conditions of use that are illustrated, crown 26D is in an intermediate position between diaphragm 18 and the retaining lugs 18A", with the formation of axial clearances 30 and 32 in relation to these members, said clearances being necessary to allow the rotation of cap 26 together with shaft 10. However, the size of these clearances is limited.In particular, when considering the device in the unmounted or free condition, clearance 30 is small in comparison with the distance which separates lip 24 from the disc part 26A, in such a way that the free edge of the crown 26D may stop axially against diaphragm 18 before lip 24 is near enough to disc 26Ato be able to be damaged by this. On the other hand, clearance 32 is small in comparison with the distance which separates lip 22 from the free edge of hub 26B, in such a way that lip 22 is in contact with the external cylindrical surface of the hub even when (in the unmounted condition of the device) the crown 26D stops axially against lugs 18A".

In other words, the sum of the clearances 30 and 32 is so small that lips 22 and 24 are always within the axial range of hub 26B.

In operation, lubricant is prevent from leaving the inside of support 12 by the sealing contact of lip 22 ("internal sealing lip") with hub 26B, whilst the penetration of water or other liquid from outside is prevented by the sealed contact of lip 24 ("external sealing lip") with the same hub 26B. The penetration of foreign material from outside is also rendered difficult by the narrow labyrinth run formed by crown 26D in relation to skirt 18A and to diaphragm 18.

Finally, during the rotation of shaft 10, foreign material which might adhere to cap 26 is thrown off by centrifugal force.

In Figs. 2 and 3, the parts corresponding to those already described with reference to Fig. 1 are shown with the same reference numbers increased by 200.

In this embodiment, internal sealing ring 222 is in sealing contact with the external cylindrical surface of hub 26B, as in Fig. 1, whilst, however, external sealing lip 224 is pressed into a cup-shaped profile to establish a front sealing contact with the internal front face (flat and smooth) of disc part 226A of cap 226. In this case, moreover, the proportioning of clearances 228 and 232 corresponds still to those of clearances 28 and 32 of Fig. 1, whilst, however, clearance 230 is proportioned in such a way as to ensure stopping of crown 226D by diaphragm 218 before lip 224 undergoes excessive deformation against the front face of disc 226A when the device is manipulated in its unmounted condition as illustrated in Fig. 2.

In Figs. 4 and 5, the parts corresponding to those already described with reference to Fig. 1 are shown with the same reference numbers increased by 400.

In this embodiment both lips 422,424 are arranged to form a sealing against the internal front face of the disc part 426A of cap 426. Clearance 428 is suffi ciently small to prevent contact between the internal sealing lip 422 and the hub 426B. Clearance 430 is sufficiently small to ensure the stopping of crown 426D against diaphragm 418 before the lips undergo excessive deformation on the part of disc 426A when the device is manipulated in its unmounted conditions illustrated in Fig. 4. There is no critical limit for clearance 432; however, for preference, when crown 426D touches lugs 418A", disc 426A is still in light contact with lips 422,424, or it is only lightly pushed away by these.

In Fig. 6 the parts corresponding to those already described with reference to Fig. 1 are indicated with the same reference numbers increased by 600. In this variant, the "shaft" component is shown by internal ring 610 of a ball bearing, whilst the fixed member is shown by external ring 612 of the same bearing, and the sealing device is to ensure sealing between the two rings. Lips 622 and 624 are in frontal sealing configuration, as in Figs. 4 and 5. Differing from the preceding embodiments, however, the re-entrant part 626C of cap 626 ends with a radiallyoutward directed peripheral edge 626C'. Moreover, in place of the stop lugs 18A" in Fig. 1 a stop ring 40 is used, positioned in an internal peripheral groove of skirt 618A of diaphragm 618.

In the sealing devices described above, the cap member (26 of Fig. 1) which is permanently incorporated in the device, has a duplicate function: that is, for preventing damage orturning up of the lip (or of the lips) during assembly with a rotary shaft, and of preventing (during its use) the penetration of foreign particles which may damage the contact edge.

Preferably, the cap and the diaphragm are made from sheet metal. In such a case, the stop means may be formed by lugs punched in the free edge of the skirt and distributed uniformly on its circumference, or by a continuous turning of said free edge produced for example by means of rolling. The peripheral face of the skirt has a cylindrical crown directed axially towards the diaphragm to form a limit to the movement of the cap towards the diaphragm when the device has not been mounted on a rotary shaft. When the device is mounted in the operating position, the peripheral face of the cap is in an axially intermediate position between the diaphragm and the said stop means which belong to the free edge of the skirt, thus creating a labyrinth. In such position, the cap hub is force-fitted onto the shaft, so that the cap rotates together with the shaft in relation to the diaphragm, and in such a position the cap is on the side of the external environment and is thus able to throw off by centrifugal forces foreign particles which otherwise would tend to reach the lipped sealing ring through said labyrinth.

The lipped sealing ring may co-operate in sealed contact both with the hub part, or with the disc part, of the cap. For preferance, the sealing ring has two lips turned in opposite directions. Both these lips may co-operate with the hub part, or with the disc part, or one of these may co-operate with the hub part whilst the other co-operates with the disc part.

Claims

1. A sealing device, for a rotary shaft, comprising a rigid annular diaphragm having an external peripheral face forming a cylindrical skirt which extends in one axial direction and an internal peripheral edge on which a lipped sealing ring of flexible material is arranged, and an annular cap in sealing contact with the lipped sealing ring, said cap having an annular disc part whose external peripheral edge penetrates with radial clearance the space surrounded by the skirt and a cylindrical hub part which extends axially from the internal circumference of said disc part in the opposite axial direction to said skirt, and wherein stop means are provided for preventing separation of the cap from the diaphragm.

2. A device as claimed in claim 1, wherein the diaphragm and its skirt are made from sheet metal, and the stop means are formed by lugs punched in the free edge of the skirt and distributed uniformly about its circumference.

3. A device as claimed in claim 1, wherein the diaphragm and its skirt are made from sheet metal, and the said stop means are formed by a continuous radially-inwards turning of the free edge of the skirt.

4. A device as claimed in any one of the preceding claims, wherein the external peripheral edge of the cap comprises a cylindrical crown directed axially towards the diaphragm to form a limit stop for the cap towards the diaphragm.

5. Adevice as claimed in any one of the preceding claims, wherein the lipped sealing ring has an internal sealing lip and an external sealing lip.

6. A device as claimed in claim 5, wherein both lips of the sealing ring are arranged to seal with the hub.

7. A device as claimed in claim 6 and substantially as herein described with reference to and as illustrated in Fig. 1 of the accompanying drawings.

8. A device as claimed in claim 5, wherein the internal sealing lip is arranged to seal with the hub, and the external sealing lip is arranged to seal with an internal face of the disc part of the cap.

9. A sealing device as claimed in claim 8 and substantially as herein described with reference to and as illustrated in Figs. 2 and 3 of the accompanying drawings.

10. A device as claimed in claim 5, wherein both lips of the sealing ring are arranged to seal with an internal face of the disc part of the cap.

11. A sealing device as claimed in claim 10 and substantially as herein described with reference to and as illustrated in Figs. 4 and 5 of the accompanying drawings.

12. A sealing device substantially as herein described with reference to and as illustrated in Fig.

1, Figs. 2 and 3, Figs. 4 and 5, or Fig. 6 of the accompanying drawings.

13. A unit having a rotary shaft in a support and sealed by a sealing device as claimed in any one of the preceding claims.