GB2239060A

GB2239060A - A shaft sealing arrangement

Info

Publication number: GB2239060A
Application number: GB8928057A
Authority: GB
Inventors: Gay Frank Du
Original assignee: Forsheda AB
Current assignee: Forsheda AB
Priority date: 1989-12-12
Filing date: 1989-12-12
Publication date: 1991-06-19
Anticipated expiration: 2009-12-12
Also published as: GB2239060B; GB8928057D0; FR2656058B3; FR2656058A3

Abstract

The sealing arrangement seals a space between a rotatable shaft 2 and wall 6 substantially perpendicular to the shaft. A sealing ring 10 has a body 14 and a sealing lip 16 unitary therewith. A retainer 12 keeps the sealing ring 10 in a correct position on the shaft 2. The body 14 of the sealing ring 12 has recesses 28 and the retainer 12 comprises projections 26 engaging the recesses 28. <IMAGE>

Description

A shaft sealing arrangement The present invention relates to a shaft sealing arrangement for sealing a space between a rotatable shaft and a surface extending substantially perpendicular to the shaft, for example for sealing a space between a shaft and a surface of a bearing housing extending perpendicular to the axis of the shaft.

Many different types of shaft sealing arrangements are previously known.

For example there are gap seals and labyrinth seals as well as elastic material frictional seals.

It is a special problem to provide a shaft sealing arrangement which is of a simple, cheap and reliable construction and in spite thereof provides for a good sealing action at high rotational speeds as well as low rotational speeds of the shaft. These requirements are not fullfilled by a gap seal or a labyrinth seal, as seals of this type have extremely restricted sealing action at low rotational speeds. A previously known elastic material frictional sealing ring is formed by a rubber ring which is elastically tensioned on the shaft and includes a lip axially engaging said surface extending perpendicular to the shaft. The rubber ring rotates together with the rotational movement of the shaft while the lip under friction slides against the surface extending perpendicular to the shaft when the shaft is rotated. A sealing ring of this kind presents a number of advantages.The design of the ring is simple and cheap and the ring is easy to mount. In addition thereto a sealing ring of this kind presents a good sealing action when the shaft is stationary as well as when the shaft rotates at high and low rotational speeds. Thereby it is possible to adapt the pressure of the lip against the engagement surface when the ring is mounted so that the lip engages the engagement surface only when the shaft is stationary or at low rotational speeds of the shaft while the lip lifts from the engagement surface at high rotational speeds so as to form a frictionless gap seal. Thus, it is of great importance that a sealing ring of this kind is retained in the correct position on the shaft so as to provide for a correct operation of the sealing ring.In order to provide the retaining of a sealing ring of the kind consisting of a body portion tensionable on to the shaft and an annular sealing lip unitary therewith and adapted to engage the radially extending engagement surface it is previously known to provide the body portion with a metal reinforcing ring providing that the body portion maintains its pressure against the shaft. Thereby the sealing ring is prevented from loSingits engagement with the shaft because of the influence of the centrifugal force also at high rotational speeds of the shaft. However, it represents a disadvantage of this type of sealing ring that the reinforcing ring has to press the body portion with a relatively great force against the shaft for maintaining the correct position of the sealing ring.The drawback arising in connection therewith is caused by the fact that the pressing of the body portion against the shaft provides for an influence on the operation of the sealing lip because of a deformation thereof which in turn has an influence on the engagement of the sealing lip with the surface extending perpendicular to the shaft.

The object of the invention is to provide a shaft sealing arrangement of said kind, In which a sealing ring comprising a body portion and a sealing lip are retained in a correct position on a shaft without positively forcing the body portion of the sealing ring against the shaft so as only by means of the friction against the shaft be maintained in the correct position. In order to comply with this object the shaft sealing arrangement according to the invention is characterized in that the body portion of the sealing ring is formed with recesses and that the sealing arrangement comprises a retainer device which is fixable in relation to the shaft and is provided with projections extending into said recesses of the body portion.

In a preferred embodiment of the shaft sealing arrangement according to the invention the projections extend into the recesses with a loose fit. It is suitable that the retainer device comprises a portion peripherally enclosing the body portion of the sealing ring, the projections being positioned at the inner surface of said portion of the retainer device. It also preferred that the retainer device comprises a fixing surface engaging a radial surface of the body portion of the sealing ring.

In a shaft sealing arrangement according to the invention the retaining of the sealing ring providing for the correct operation thereof without any influence on the elastic material of the sealing ring which may cause problems from the operation of point of view.

The invention is described in the following with reference to the accompanying drawings.

Fig. 1 is an axial section of a shaft sealing arrangement according to the invention.

Fig. 2 is a cross-sectional view on line I - I in fig. 1.

Fig. 3 is a plan view of a sealing ring included in the sealing arrangement of figs. 1 and 2.

Fig. 1 shows a rotatable shaft 2 extending through an opening 4 of a wall 6 extending perpendicular to the axis of the shaft 2. The wall 6 can be the wall of a bearing housing. In order to seal the space or gap between the shaft 2 and the surface defining the opening 4 of the wall 6 there is used a sealing arrangement 8 according to the invention. The main components of the sealing arrangement 8 consist of a sealing ring 10 and a retainer device 12 for the sealing ring.

The sealing ring 10 consists of a body portion 14 and a sealing lip 16 unitary therewith. Between the body portion 14 and the sealing lip 16 there is formed an outwardly open, annular groove 18 having a V-shaped cross section. Thereby the lip 16 has substantially less mass than the body portion 14 of the sealing ring. The sealing ring, i.e. the body portion 14 as well as the sealing lip 16, consists of a highly elastic material, preferably rubber.

Before the sealing ring 10 is positioned on the shaft 2 it has a diameter which is slightly less than the outer diameter of the shaft. Thus, the sealing ring 10 is positioned on the shaft 2 with a slight tensioning assisting to the retaining of the sealing ring 10 on the shaft 2. The sealing lip 16 engages the wall 6 with a predetermined engagement pressure. Thereby it can be suitable to adapt the engagement pressure so that the lip 16 engages the wall when the shaft 2 is stationary or is rotating at low rotational speeds but so that the engagement is interrupted at higher rotational speeds of the shaft because of the influence of the centrifugal force. Thereby the sealing ring 16 will constitute a gap seal at higher rotational speeds which of course reduces the wearing of the lip 16.

In order to prevent the sealing ring from leaving its correct position on the shaft the sealing arrangement according to the invention includes a retainer device 12. In the embodiment shown in the drawings the retainer device 12 is unitary with the shaft. However, the retainer device can also be constituted by a separate arrangement fixable to the shaft. The retainer device 12 comprises a main portion 20 radially projecting from the shaft and forming at its section adjacent the shaft a radially directed shoulder surface 22 engaged by the body portion 14 of the sealing ring for defining the axial position of the sealing ring 10 on the shaft 2. At its radially outer portion the main portion 20 has an annular portion 24 projecting in the direction of the wall 6 and enclosing the outer peripheral surface of the body portion 14 of the sealing ring 10 with a loose fit. At its inner surface the peripheral portion 24 has a number of radially inwardly directed projections 26 which in the embodiment shown amounts to a number of 3. The projections 26 are of half-circular cross-sectional shape and engages recesses 28 in the body portion 14 of the sealing ring 10.

The projections 26 provide a locking of the sealing ring 10 with regard to relative rotation between the sealing ring 10 and the shaft 2. In the sealing arrangement according to the Invention the retaining device 12 provides a locking of the sealing ring 10 to the shaft 2 without such an influence on the sealing ring that can jeopardize or deteriorate the function of the sealing ring. Thus, the retainer device 12 does not exert such a force on the sealing ring 10 that may cause an elastic deformation thereof, but the sealing ring is not influenced by the retainer device until it strives to leave its correct position.

Thus, it is recognized that the sealing ring of the sealing arrangement according to the invention is of simple and cheap construction, Is easy to mount in a correct position on the shaft and retains its correct sealing position during all operational conditions.

Claims

1. A sealing arrangement for sealing a space between a rotatable shaft and a surface extending substantially perpendicular to the axis of the shaft, comprising a sealing ring of elastic material that is to be positioned on the shaft and comprising a body portion and a sealing lip unitary therewith adapted to engage the surface extending perpendicular to the shaft, C h á r a c t e r i z e d in that the body portion of the sealing ring is provided with recesses and that the sealing arrangement includes a retainer device which is stationary in relation to the shaft and is provided with projections extending into the recesses.

2. A sealing arrangement as claimed in claim 1, c h a r a c t e r i z e d in that the projections engage the recesses with a loose fit.

3. A sealing arrangement as claimed in claims 1 or 2, c h a r a c t e r i z e d in that the retainer device comprises a portion peripherally enclosing the body portion of the sealing ring.

4. A sealing arrangement as claimed in claim 3, c h a r a c t e r i z e d in that the projections are positioned at the inner surface of the portion of the retainer device peripherally enclosing the body portion of the sealing ring and extend radially inwards into the recesses, the recesses being provided at the peripherally outer surface of the body portion of the sealing ring.

5. A sealing arrangement as claimed in any of the preceding claims, c ha r act e r i z e d in that the retainer device comprises a shoulder surface adapted to be engaged by an opposite surface of the body portion of the sealing ring for defining the axial position of the sealing ring on the shaft.

6. A sealing arrangement substantially as described with reference to, and as shown in, the accompanying drawings.