GB1568682A

GB1568682A - Seal assembly

Info

Publication number: GB1568682A
Application number: GB2782/76A
Authority: GB
Original assignee: POLYPAC Ltd
Current assignee: POLYPAC Ltd
Priority date: 1976-01-24
Filing date: 1976-01-24
Publication date: 1980-06-04
Also published as: SE7700188L; DE2700550A1; IT1077552B; SE418527B

Description

(54) SEAL ASSEMBLY (71) We, POLYPAC (HARTLEPOOL) LLMITED, a British Company, of Brenda Road, Hartlepool, Cleveland, 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 in and by the following statement: This invention relates to a seal assem bly of the kind intended in use to be loca ted within a groove defined in one of a pair of relatively movable members and to make sealing engagement with a surface on the other of the pair of members.

The object of the invention is to provide a seal assembly for the purpose specified in a simple and convenient form.

According to the invention a seal assem bly for the purpose specified comprises a backing member formed from a relatively soft resilient material, such as a nitrile rub ber the backing member being arranged to be received in use, within the groove in sealing engagement with the walls of the groove, the seal assembly further including a seal member which is partly embedded in the backing member and which defines a ir of spaced sealing lips which project beyond the backing member and which are arranged in use to extend into sealing en gagement with said surface, said seal mem ber being formed from a relatively rigid material, the arrangement being such that, in use any movement of said surface towards the groove is accommodated by deformation of the backing member.

One example of a seal assembly in accord- ance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows in cross-section a linkage mechanism, and Figure 2 shows to an enlarged scale a portion of the mechanism of Figure 1, illu stlating-a seal assembly according to the present invention.

With reference to Figure 1 of the drawings, there is shown a section through a bearing pin connecting two sections of track of a track laying vehicle. One track section comprises two links 10 mounted on a sleeve 11 and the other track section comprises two links 12 secured on a pin 13.

The sleeve 11 is pivotally mounted about the pin 13 and annular spacer elements 14 are provided between the ends of the sleeve 11 and links 12. The spacer elements 14 define, with overhanging portions of the links 12, a pair of recesses 15.

As the vehicle is driven in use, the track sections pivot relative to each other: in the particular example the range of angular movement is about 40 . The bearing surface between the sleeve 11 and the pin 13 is lubricated by a suitable oil or grease and conveniently the pin 13 is drilled to provide a central reservoir for the lubricant, the ends of the drilling being closed by suitable plugs. The reservoir connects with the bearing surfaces by suitably positioned radial drilling indicated at 16. It is essential to prevent loss of lubricant from the assembly and it is also essential to prevent, so far as possible, the possibility of foreign matter such as dirt or water reaching the bearing surfaces by the sleeve 11 and pin 13. In designing a seal it is also essential to take into account wear which will occur during the life of the assembly, such wear causing an increase in the end float of the bearing and also wear of the bearing surface of the pin 13 and sleeve 11 which can allow the end faces of the -sleeve 11 to move from a true radial position relative to the axis of the bearing.

The seal assembly is seen in 'Figure 2, it being understood that in this example the seal assembly is of annular form.

The seal assembly comprises an annular backing member 17 which is pressed' into the groove constituted 'by the recess 15.

The side walls and the base wall of the backing member 17 are provided with 'ribs and it will be understood that in Figure 2 the outline of the backing member is shown as though the backing member were re- moved from the recess: in other words the natural shape is shown.

The cross-sectional area of the backing member 17 is such that, when it is pressed into the recess, some free space will still exist particularly between the base wall of the recess and the backing member 17. In addition, the side walls of the backing member 17 are recessed adjacent the base wall so that again there will be some free space.

When the backing member 17 is inserted into the recess, the interference is such that the backing member 17 is held against angular movement about the axis of the pin 13.

Moreover, the backing member 17 forms a seal with the walls of the recess.

The backing member 17 is formed from a relatively soft, i.e. easily deformable, resilient material. In the particular example a nitrile rubber is utilised having a Shore A Durometer Hardness value of about 75 .

Moreover, the seal assembly also includes a seal member 18 which is embedded in the hacking member 17. The seal member 18 defines a pair of sealing lips 19 which are radially spaced and which engage the end face of the sleeve 11. The lips 19 project beyond the front surface of the backing member 17 and define between them an ananular recess 20 which may in use be filled with a suitable grease. The lips 19 provide sealing engagement with the end face of the sleeve 11 and thereby the lubricant is retained in its correct place and dirt and water are denied access to the bearing surfaces.

As will be seen, the seal member 18 is of generally triangular section but the side walls converge to the sealing lips 19 and the material of the backing member 17 extends partly along the aforesaid converging portions of the side walls. The spacing of the sealing lips 19 and the fact that the material from which the sealing member 18 is formed is a relatively rigid material, as will be described, means that the sealing member 18 will tend to follow any m6Ve- ment of the end face of the sleeve 11 out of the radial plane. The sealing member 18 is nevertheless provided with a sufficient degree of support by the backing member 17. Furthermore, the dimensions of the various components of the seal assembly and the bearing and track assembly are such that the sealing lips 19 are resiliently urged into engagement with the end face of the sleeve 11. As a result the sealing member 18 can move axially with the sleeve 11 as end float occurs. Movement of the sealing member 18 towards the base of the recess of groove is allowed by the resilience of the backing member 17 and by the aforesaid free space, the preloading of backing member 17 generating the force acting to urte the sealing lips 19 into contact with the sleeve 11.

The sealing member 18, as has been mentioned, is formed from a relatively rigid material as compared with the material from which the backing member 17 is formed. The material forming the sealing member 18 is conveniently an elastomeric material so that slight deformation of the sealing lips 19 can occur. In the particular example a material having a Shore A Durometer Hardness value of the order of 95" is employed, the material being polyurethane.

WHAT WE CLAIM IS: 1. A seal assembly for a pair of relatively movable members, comprising a backing member formed from a relatively soft resilient material, said backing member being arranged to be received in use within a groove defined in one of said relatively movable members so as to be in sealing en gagement with the walls of said groove, and a seal member partly embedded in the backing member and defining a pair of spaced sealing lips which project beyond the backing member and which are arranged in use to extend into sealing engagement with a surface on the other of said relatively movable members, said seal member being formed from a relatively rigid material, the arrangement being such that, in use, any movement of said surface towards said groove is accommodated by deformation of the backing member.

2. A seal assembly as claimed in claim 1, wherein the material from which the backing member is formed has a Shore A Durometer Hardness value of substantially 750 3. A seal assembly as claimed in claim 2, wherein the backing member is formed from a nitrile rubber.

4. A seal assembly as claimed in claim 1, 2 or 3, wherein the material from which the seal member is formed has a Shore A Durometer Hardness value of substantially 950 5. A seal assembly as claimed in claim 4, wherein the seal member is formed frbm polyurethane.

6. A seal assembly as claimed in any preceding claim, wherein the cross-sec- tional form of the backing member is such that, when it is received in said groove in use, a clearance is provided between portions of a base wall of the groove and the backing member.

7. A seal assembly as claimed in any preceding claim, wherein Surfaces óf the backing member which engage side walls of said groove in use are recessed adjacent a surface thereof which engages a base wall of said groove in use.

8. A seal assembly as claimed in any preceding claim, wherein the seal member

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. into the recess, some free space will still exist particularly between the base wall of the recess and the backing member 17. In addition, the side walls of the backing member 17 are recessed adjacent the base wall so that again there will be some free space. When the backing member 17 is inserted into the recess, the interference is such that the backing member 17 is held against angular movement about the axis of the pin 13. Moreover, the backing member 17 forms a seal with the walls of the recess. The backing member 17 is formed from a relatively soft, i.e. easily deformable, resilient material. In the particular example a nitrile rubber is utilised having a Shore A Durometer Hardness value of about 75 . Moreover, the seal assembly also includes a seal member 18 which is embedded in the hacking member 17. The seal member 18 defines a pair of sealing lips 19 which are radially spaced and which engage the end face of the sleeve 11. The lips 19 project beyond the front surface of the backing member 17 and define between them an ananular recess 20 which may in use be filled with a suitable grease. The lips 19 provide sealing engagement with the end face of the sleeve 11 and thereby the lubricant is retained in its correct place and dirt and water are denied access to the bearing surfaces. As will be seen, the seal member 18 is of generally triangular section but the side walls converge to the sealing lips 19 and the material of the backing member 17 extends partly along the aforesaid converging portions of the side walls. The spacing of the sealing lips 19 and the fact that the material from which the sealing member 18 is formed is a relatively rigid material, as will be described, means that the sealing member 18 will tend to follow any m6Ve- ment of the end face of the sleeve 11 out of the radial plane. The sealing member 18 is nevertheless provided with a sufficient degree of support by the backing member 17. Furthermore, the dimensions of the various components of the seal assembly and the bearing and track assembly are such that the sealing lips 19 are resiliently urged into engagement with the end face of the sleeve 11. As a result the sealing member 18 can move axially with the sleeve 11 as end float occurs. Movement of the sealing member 18 towards the base of the recess of groove is allowed by the resilience of the backing member 17 and by the aforesaid free space, the preloading of backing member 17 generating the force acting to urte the sealing lips 19 into contact with the sleeve 11. The sealing member 18, as has been mentioned, is formed from a relatively rigid material as compared with the material from which the backing member 17 is formed. The material forming the sealing member 18 is conveniently an elastomeric material so that slight deformation of the sealing lips 19 can occur. In the particular example a material having a Shore A Durometer Hardness value of the order of 95" is employed, the material being polyurethane. WHAT WE CLAIM IS:

1. A seal assembly for a pair of relatively movable members, comprising a backing member formed from a relatively soft resilient material, said backing member being arranged to be received in use within a groove defined in one of said relatively movable members so as to be in sealing en gagement with the walls of said groove, and a seal member partly embedded in the backing member and defining a pair of spaced sealing lips which project beyond the backing member and which are arranged in use to extend into sealing engagement with a surface on the other of said relatively movable members, said seal member being formed from a relatively rigid material, the arrangement being such that, in use, any movement of said surface towards said groove is accommodated by deformation of the backing member.

2. A seal assembly as claimed in claim 1, wherein the material from which the backing member is formed has a Shore A Durometer Hardness value of substantially 750

3. A seal assembly as claimed in claim 2, wherein the backing member is formed from a nitrile rubber.

4. A seal assembly as claimed in claim 1, 2 or 3, wherein the material from which the seal member is formed has a Shore A Durometer Hardness value of substantially 950

5. A seal assembly as claimed in claim 4, wherein the seal member is formed frbm polyurethane.

8. A seal assembly as claimed in any preceding claim, wherein the seal member

is of generally triangular section, said sealing lips being provided at two apices of said section.

9. A seal assembly as claimed in claim 8, wherein side walls of the seal member converge towards the sealing lips.

10. A seal assembly for a pair of rela tively movable members, substantially as hereinbefore described with reference to and as shown in the accompanying draw ings.