GB1583618A

GB1583618A - Rotary shaft seal

Info

Publication number: GB1583618A
Application number: GB19022/78A
Authority: GB
Original assignee: Paulstra SNC
Current assignee: Paulstra SNC
Priority date: 1977-05-11
Filing date: 1978-05-11
Publication date: 1981-01-28
Also published as: IT7849272A0; FR2390647A2; FR2390647B2; DE2820401A1; DE2820401C2; IT1156729B

Description

(54) ROTARY SHAFT SEAL (71) We, PAULSTRA, a French body corporate, of 61 rue Marius Aufan, 92305 Levallois Perret, France, 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 seals which are mounted between two relatively rotatable machine parts, for example, a shaft and housing. Such seals usually comprise a sleeve of elastomeric material disposed between the two parts and non-rotatably mounted on one of them, the sleeve being shaped to form a lip which is in close sealing contact with the other part.Between the sleeve and the part against which the lip bears, a rigid collar may be provided which supports the sleeve in a region close to the lip and which lessens the effect of any motion which may cause distortion of the lip from its circular shape, and break the contact between the lip and the machine part against which it bears. This collar is particularly effective where there is an appreciable pressure difference between the two environments separated by the seal.

Such a pressure difference may cause axial movement of the collar and sleeve resulting in frictional damage to the sealing lip and reducing the stability of the whole assembly.

It is now proposed that a fixed stop should be included in the assembly so as to limit such movement and lessen any damage resulting from it. The collar is in contact with the stop which is axially fixed and which limits the axial movement of the collar and of the sealing lip.

In accordance with the invention there is provided a seal assembly for providing a seal between two relatively rotatable machine parts, one of which lies radially inside the other, such as a shaft and housing, comprising a sleeve of elastomeric material disposed between the two parts and non-rotatably mounted on one of them, one end of the sleeve forming a lip which lies in close sealing contact with the other part; there being provided between the sleeve and the part in contact with the lip, a collar which supports the sleeve in a region adjacent to the lip and which lessens distortion of the lip from its original circular shape, the end of the collar furthest from the lip being in contact with a stop whose axial position is fixed, thus limiting axial motion of the collar and sleeve.

In addition to preventing axial motion of the assembly the contact between the fixed stop and the collar, if both are of metal, enables any electrical current which may arise in a shaft to be conducted away into a housing by the seal assembly thus avoiding damage to bearings which support the shaft.

The permanence of the contact between the collar and the stop can be ensured by including a resilient means to urge the collar against the stop. This may be achieved by moulding the sleeve in such a way that when the assembly is mounted, the sleeve urges the collar towards the stop. The contact is then maintained despite vibrations or other disturbances.

The shaft may also move in such a way that its axis is no longer parallel to that of the sleeve of the seal assembly. When this occurs a great deal of stress is inflicted on the ends of a rigid collar which may eventually be damaged. This can be avoided if the generatrix of the collar's inner surface is a convex curve rather than a straightline so that a certain degree of angular movement is permitted. Two embodiments of the invention will now be described in detail with reference to the drawings, of which Figure 1 is a half-section of an embodiment of a rotary shaft seal assembly in accordance with the invention, and Figure 2 is a similar half-section of a second embodiment of such an assembly in accordance with the invention.

The seal assembly is mounted (see Figure 1) between a housing 1 and a relatively rotatable shaft 2 which is supported by bearings (not shown) which often take the form of ball bearings.

The seal assembly comprises a conical or part cylindrical, part conical sleeve 3 of elastomeric material which surrounds the shaft 2. This sleeve 3 is integral with a frame 4 which is located within an opening in the housing 1. The sleeve 3 is extended at one end to form a lip 5 which is in close sealing contact with the shaft 2 along a sealing edge 6 under resilient pressure exerted by an annular spring 10 which is located in a groove formed in the sleeve 3.

Between the sleeve 3 and the shaft 2 is provided a collar 13 which supports the sleeve 3. Contact between the sleeve 3 and the collar 13 is made by means of a rib 15 formed on the inside of the sleeve 3 which locates in a groove 16 formed in the collar 13. The collar 13 acts in conjunction with a ring 7, which is located in a groove formed in the outer surface of the sleeve 3, to keep the lip 5 rigid and circular so that the sealing edge 6 cannot easily be deformed and displaced from the shaft 2.

In order to prevent axial movement of the collar 13 away from the sleeve 3, the assembly is fitted with a frame 17, which fits between the housing 1 and the frame 4. The frame 17 is integral with an annular flange 18 which is in contact with an end 19 of the collar 13 to form a stop limiting the axial movement of the collar. The frame 17 is held in place by a ring 21 which is located in a groove in the housing 1 and which holds the frame 17 in place against an end of the sleeve 3. Vibrations or other similar disturbances may cause the contact between the collar 13 and the flange 18 to be broken but permanent contact can be maintained by providing a resilient means for urging the two parts toward one another.This can be done by shaping the sleeve 3 as shown by the lines at 20 so that when the sleeve 3 is mounted it is elastically deformed and its resilience causes it to exert a force on the collar 13 urging it towards the flange 18.

If the components 13 and 17 are metallic, the seal assembly will also conduct away any electrical currents arising in the shaft 2. thus avoiding possible damage to the bearings which support it. Such currents might arise, for example. in the axle-bores of railway vehicles.

In order to make sure that the electrical contact between the collar 13 and the shaft 2 remains unbroken, the axis XX' of the sleeve 3 is displaced relative to the axis YY' of the shaft 2 so that the sleeve 3 holds the collar 13 against the shaft 2.

The shaft 2 may also move in such a way that the axes XX' and YY' become inclined at an angle a to one another as shown in figure 2. When this occurs, considerable stress can be inflicted on the ends a and b of the collar 13 which may eventually result in mechanical damage to the collar 13.

An embodiment of the seal assembly adapted to avoid deterioration of the collar 13 under such conditions is shown in Figure 2. The seal assembly shown is identical to that of Figure 1 in all respects except in the shape of the collar 13. The generatrix of the inner surface of the collar 13 is in this case a convex curve 22 rather than a straight line parallel to the axis of the collar. This curvature of the inner surface of the collar 13 permits a certain degree of inclination between the axes XX' and YY'; the shape of the curve 22 being determined by the values of the angle X which are to be permitted.

WHAT WE CLAIMS IS: 1. A seal assembly for providing a seal between two relatively rotatable machine parts, one of which lies radially inside the other, such as a shaft and housing, comprising a sleeve of elastomeric material disposed between the two parts and non-rotatably mounted on one of them, one end of the sleeve forming a lip which lies in close sealing contact with the other part; there being provided between the sleeve and the part in contact with the lip, a collar which supports the sleeve in a region adjacent to the lip and which lessens distortion of the lip from its original circular shape, the end of the collar furthest from the lip being in contact with a stop whose axial position is fixed, thus limiting axial motion of the collar and sleeve.

2. An assembly as claimed in claim 1 comprising resilient means for urging the collar towards the stop so that contact between the collar and stop is maintained.

3. An assembly as claimed in claim 2 in which the resilient means is provided by shaping the elastomeric sleeve so that when the assembly is mounted, the sleeve is elastically deformed and exerts an axial force on the collar, urging it towards the stop.

4. An assembly as claimed in any of the preceding claims in which the stop and the collar are both metallic and provide a conducting path between the two relatively rotatable parts through which electrical currents are conducted away from bearing which may be damaged by such currents.

5. An assembly as claimed in claim 4 which comprises a resilient means for maintaining contact between the collar and the machine part against which the sealing lip bears.

7. An assembly as claimed in any of the

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Claims

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second embodiment of such an assembly in accordance with the invention.

The seal assembly is mounted (see Figure 1) between a housing 1 and a relatively rotatable shaft 2 which is supported by bearings (not shown) which often take the form of ball bearings.

The seal assembly comprises a conical or part cylindrical, part conical sleeve 3 of elastomeric material which surrounds the shaft 2. This sleeve 3 is integral with a frame 4 which is located within an opening in the housing 1. The sleeve 3 is extended at one end to form a lip 5 which is in close sealing contact with the shaft 2 along a sealing edge 6 under resilient pressure exerted by an annular spring 10 which is located in a groove formed in the sleeve 3.

Between the sleeve 3 and the shaft 2 is provided a collar 13 which supports the sleeve 3. Contact between the sleeve 3 and the collar 13 is made by means of a rib 15 formed on the inside of the sleeve 3 which locates in a groove 16 formed in the collar 13. The collar 13 acts in conjunction with a ring 7, which is located in a groove formed in the outer surface of the sleeve 3, to keep the lip 5 rigid and circular so that the sealing edge 6 cannot easily be deformed and displaced from the shaft 2.

In order to prevent axial movement of the collar 13 away from the sleeve 3, the assembly is fitted with a frame 17, which fits between the housing 1 and the frame 4. The frame 17 is integral with an annular flange 18 which is in contact with an end 19 of the collar 13 to form a stop limiting the axial movement of the collar. The frame 17 is held in place by a ring 21 which is located in a groove in the housing 1 and which holds the frame 17 in place against an end of the sleeve 3. Vibrations or other similar disturbances may cause the contact between the collar 13 and the flange 18 to be broken but permanent contact can be maintained by providing a resilient means for urging the two parts toward one another.This can be done by shaping the sleeve 3 as shown by the lines at 20 so that when the sleeve 3 is mounted it is elastically deformed and its resilience causes it to exert a force on the collar 13 urging it towards the flange 18.

If the components 13 and 17 are metallic, the seal assembly will also conduct away any electrical currents arising in the shaft 2. thus avoiding possible damage to the bearings which support it. Such currents might arise, for example. in the axle-bores of railway vehicles.

In order to make sure that the electrical contact between the collar 13 and the shaft 2 remains unbroken, the axis XX' of the sleeve 3 is displaced relative to the axis YY' of the shaft 2 so that the sleeve 3 holds the collar 13 against the shaft 2.

The shaft 2 may also move in such a way that the axes XX' and YY' become inclined at an angle a to one another as shown in figure 2. When this occurs, considerable stress can be inflicted on the ends a and b of the collar 13 which may eventually result in mechanical damage to the collar 13.

An embodiment of the seal assembly adapted to avoid deterioration of the collar 13 under such conditions is shown in Figure 2. The seal assembly shown is identical to that of Figure 1 in all respects except in the shape of the collar 13. The generatrix of the inner surface of the collar 13 is in this case a convex curve 22 rather than a straight line parallel to the axis of the collar. This curvature of the inner surface of the collar 13 permits a certain degree of inclination between the axes XX' and YY'; the shape of the curve 22 being determined by the values of the angle X which are to be permitted.

WHAT WE CLAIMS IS:

1. A seal assembly for providing a seal between two relatively rotatable machine parts, one of which lies radially inside the other, such as a shaft and housing, comprising a sleeve of elastomeric material disposed between the two parts and non-rotatably mounted on one of them, one end of the sleeve forming a lip which lies in close sealing contact with the other part; there being provided between the sleeve and the part in contact with the lip, a collar which supports the sleeve in a region adjacent to the lip and which lessens distortion of the lip from its original circular shape, the end of the collar furthest from the lip being in contact with a stop whose axial position is fixed, thus limiting axial motion of the collar and sleeve.

2. An assembly as claimed in claim 1 comprising resilient means for urging the collar towards the stop so that contact between the collar and stop is maintained.

3. An assembly as claimed in claim 2 in which the resilient means is provided by shaping the elastomeric sleeve so that when the assembly is mounted, the sleeve is elastically deformed and exerts an axial force on the collar, urging it towards the stop.

4. An assembly as claimed in any of the preceding claims in which the stop and the collar are both metallic and provide a conducting path between the two relatively rotatable parts through which electrical currents are conducted away from bearing which may be damaged by such currents.

5. An assembly as claimed in claim 4 which comprises a resilient means for maintaining contact between the collar and the machine part against which the sealing lip bears.

7. An assembly as claimed in any of the

preceding claims comprising a collar whose inner surface is generated by a convex curve so that angular movement of one part relative to the other is possible without inflicting stress on the ends of the collar.