RADIAL LIP SEALS

Abstract: In a radial lip seal, a peripheral portion (26) of an annular sealing element (22) of a flexible resilient sheet material is clamped between opposing portions (14, 20) of a shell (10, 16) to deform the sheet and create a frusto-conical lip-forming portion (34). The sealing element is clamped together with a peripheral portion (28) of a resiliently flexible sheet-form supporting element (24) which overlies the sealing element to give support to the lip-forming portion in use of the seal.

Description: RADIAL LIP SEALS This invention is concerned with improvements in or relating to radial lip seals for sealing between, for example, a machine shaft (or roll, or other cylindrical element) and a cylindrical housing around the shaft. In a well known conventional oil seal construction, a coil spring is arranged to support a flexible and resilient sealing element (e.g. of rubber) of the seal, the coil spring extending in a closed loop around the seal to bear radially against a lip-forming portion of the sealing element in use of the seal. Particularly with larger seals, such as may be used in association with the rolls of paper and other rolling mills, buffeting of the seal (e.g. from eccentric running of a shaft) can cause the supporting spring to become dislodged from its required operating position. As a guard against that problem it is known to introduce a spring retainer which is secured to a shell of the seal and is hooked over the coil spring, at intervals along its continuous length, to hold the spring in position. One way in which it is known to effect this is described in GB-A-2 213 878 in which wire hooking elements are provided. A well-known alternative is to utilise a thin stainless steel strip of a zig-zag form, the peaks of the strip along one side edge being secured to the shell and the peaks along the other side edge being folded over the spring to hook onto the spring. However, it occasionally happens that a metal element of such spring retainers breaks off through repeated stressing in use. This can have extremely serious consequences, for example should the loose metal element find its way into an adjacent gearbox. Commonly, a suitably shaped sealing element of a radial lip seal may be provided by a pre-formed moulded component. However, it is also known to create a suitably formed sealing element by clamping a peripheral portion of a planar annular element (e.g. cut from sheet rubber) between suitably arranged interacting shell components of the seal which deform the element between them to provide a frusto-conical peripheral portion forming the lip. The present invention relates especially to the manufacture of seals of this latter kind, and to seals so produced. In one of its aspects the invention provides a radial lip seal of the kind in which an annular sealing element is held clamped by a shell of the seal and forms in a relaxed condition of the seal a generally frusto-conical lip-forming portion extending radially beyond the shell, characterised in that an annular supporting element is also held clamped by the shell to overlie the lip-forming portion to give resilient radial support to the lip-forming portion in use of the seal. The supporting element needs to be sufficiently stiff in a portion overlying the lip-forming portion of the sealing element to give good support to the lip region, yet sufficiently flexible at a distance from the lip to permit radial deflection of the lip. The supporting element may be formed from a sheet of similar material to the sealing element where such material is found to have suitable qualities. The supporting element may be slit or notched, or formed with a suitable array of openings, to improve its performance over an element of continuous, uncut, sheet material. As compared with traditional use of a spring, the seal lip in such a construction may be better able to follow the shaft surface without heavy, friction-producing, loadings. Alternatively, the supporting element may be constructed by securing portions of resilient flexible material (e.g. from sheet stock) to a mounting ring which may itself be relatively inflexible. There now follows a detailed description, to be read with reference to the accompanying drawings, of a radial lip seal and its manufacture which illustrate the invention by way of example. In the accompanying drawings: Figure 1 shows an axial cross-section through an annular seal; and Figures 2A, 2B, 2C and 2D show alternative forms of blank for use in formation of a supporting element of the seal in its manufacture. A radial lip seal (Figure 1) comprises an angle-form steel outer shell 10 forming a cylindrical wall 12 and a disk-form annular end wall 14; the cylindrical wall, which determines the outer diameter of the seal, extends perpendicularly from the outer periphery of the annular end wall. An inner steel shell 16, also of angle form, comprises a cylindrical wall 18 of an outer diameter corresponding to the inner diameter of the cylindrical wall 12 of the outer shell, in order to fit within the outer shell. The cylindrical wall 18 extends perpendicularly from the outer periphery of a disk-form annular end wall 20 of the inner shell. The inner and outer shells (16 and 10) can collectively be referred to as the shell of the seal. The seal comprises also a sealing element 22 and a lip-supporting element 24, each formed from sheet material as hereinafter described. The sealing and supporting elements are of similarly dimensioned annular form and overlie one another. Outer margins 26 and 28 of the two elements are held trapped between the end walls 20 and 14 of the inner and outer shells. The inner shell 16 is retained in position, clamping the element margins, by means of a turned-in end portion 30 of the outer shell 10 at the free end of the cylindrical wall 12. The sealing and supporting elements 22 and 24 are each formed from a flat annular blank cut from sheet stock of suitable material. The element must in each case be sufficiently flexible to be deformable during construction of the seal, to assume a required disposition (as hereinafter described) , and must also offer resilience in performance. The material of the sealing element should furthermore be abrasion-resistant and suitable for its sealing function against a moving shaft. In manufacture of the seal, an inner margin 32 of the annular end wall 14 of the outer shell is inturned. The margin 32 so bears against the sealing element 22, with the result that the initially-flat sealing and supporting elements 22 and 24 together become deflected axially of the seal to form frusto-conical inner portions 34 and 36 extending radially inwardly beyond the shell. The inner portion 34 of the sealing element 22 provides a sealing lip 38 at its tip. In use of the seal, the lip 38 bears against the surface of a rotating shaft to prevent the passage of oil or other materials along the shaft. Eccentricity in the running of the shaft within the seal can result in radially inward deflections of the inner portion 34 of the sealing element. The supporting element 24 serves to give resilient support to the inner portion of the sealing element, so ensuring that the lip 38 follows the shaft and at all times remains in proper sealing engagement with its surface at all positions around the seal. Figures 2A to 2D illustrate examples of suitable forms for supporting element blanks. In the example shown in Figure 2A, the blank is cut radially from the inner periphery to provide slits 40. The slits are circumferentially uniformly spaced, and all extend approximately halfway to the outer periphery. A chain-dot line indicates the extent to which the end wall 20 of the inner shell 16 overlaps the supporting element in the assembled seal. The slits 40 divide the inner portion 36 of the element into a plurality of discrete, individually flexible, resilient fingers 42. In the blank construction shown in Figure 2B, portions are cut out from the outer periphery of the blank to leave a plurality of circumferentially uniformly spaced fingers 44 which extend to the inner portion 36 of the element. In the construction shown in Figure 2C, large circular apertures 46 are cut out, and in Figure 2D there are shown circumferentially-extending apertures in the form of slots 48 which may be positioned at or closely adjacent to the inner edge of the end wall 20 (represented by the chain-dot line) , the apertures in each case serving to give greater flexibility to the supporting element in use. The particular material of the blank, its thickness, and the form of any slits and cut-outs etc can be selected to give a suitable performance to the supporting element in supporting the sealing element in use of the seal. Alternatively, the supporting element can be of a composite construction comprising an annular mounting ring and discrete portions of resilient flexible material secured (e.g. bonded) to the ring to extend radially inwards and support the inner portion 34 of the sealing element 22. The supporting ring, held clamped between the inner and outer shells, can be of relatively inflexible material and may be of metal. The portions of resilient material secured to the ring may be in the form of projecting fingers, and they may themselves be interlinked with one another around the ring.

Claims: CLAIMS 1. A radial lip seal of the kind in which an annular sealing element (22) is held clamped by a shell (10,16) of the seal and forms in a relaxed condition of the seal a generally frusto-conical lip-forming portion (34) extending radially beyond the shell, characterised in that an annular supporting element (24) is also held clamped by the shell to overlie the lip-forming portion to give resilient radial support to the lip-forming portion in use of the seal. 2. A radial lip seal according to claim 1 in which the supporting element comprises discrete radially-extending fingers (42) overlying the lip-forming portion (34) of the sealing element (22). 3. A radial lip seal according to claim 2 in which the fingers (42) are formed by radially-extending slits (40) in resiliently flexible material. 4. A radial lip seal according to claim 1 in which the supporting element (24) comprises an annular sheet of resiliently flexible material held clamped by the shell (10,16) . 5. A radial lip seal according to claim 4 in which the sheet is apertured (46,48) at intervals spaced circumferentially of the sheet to give greater flexibility to the supporting element in use. 6. A radial lip seal according to claim 1 in which the sealing element (22) comprises a sheet of material which is held deformed by the shell (10,16) to form the frusto-conical lip-forming portion.

Inventors: MCCOY RONALD GEOFFREY, MCCOY, RONALD, GEOFFREY
Applicants: AUTOSPIN OIL SEALS LTD, MCCOY RONALD GEOFFREY, AUTOSPIN (OIL SEALS) LIMITED, MCCOY, RONALD, GEOFFREY
Application year: 1996
Main classification: F16J15
IPC codes: F16J15