SEALING UNIT WITH A TWIN SEALING SHIELD

Abstract: A sealing unit consisting of two rigid, face-fo-face shields, one of which is fitted with an annular elastomeric sealing mem­ ber exerting sliding axial sealing action on a track of the other shield; the latter being provided with a flange portion having an annular boss and bearing the aforementioned track, whereas the other shield is provided, integral with the sealing member, with an axial annular rib extending perpendicular to the afore­ mentioned track, towards the aforementioned flange portion and between the aforementioned boss and a projecting lip on the aforementioned elastomeric member.

Description: SEALING UNIT WITH A TWIN SEALING SHIELD The present invention relates to a perfected sealing unit with a twin sealing. shield. The aim of the present invention is to provide a sealing unit with a twin sealing shield, the said unit having at least one sealing lip designed to exert sliding axial seal ing action on one of the said shields, and providing for greater sealing efficiency than that afforded by similar known sealing sl-liel tls currently employed, while at the same tbne enabling reasonably low-cost production. With this aim in view, according to the present invention, there is provided a sealing unit designed for insertion between two mutually-rotating members, particularly roll ing bearings, and comprising a first rigid shield designed to fit onto one of the said members, and a second rigid shield designed to fit onto the other of the said members and provided, in integral manner, with an annular sealing member niatle of elastomeric material and designed to cooperate, in sliding manner, with at least one respective slid ing track on the said first shield, for exerting axial sealing action on the said first shield; characterised by tulle fact that the said first shield comprises a radial flange portion bearing the said track and provided peri plierally outwards with an annular boss defining an annular concavity, on a front outer surface of the said first shield, and a corresponding annular convexity, on an inner surface of the said first shield defining the said track, the said sealing menvber being arranged facing the said flange portion and comprising an axial annular rib extending towards and perpendicular in relation to the said inner surface of the said first shield, but without touching the said inner surface, in such a manner as to define a supplementary axial labyrinth seal, the said rib being formed integral with the said sealing member between a projecting oblique radial annular lilts on the said sealing member, said lip being designed to interfere with the said first shield for achieving the said sliding axial sealing action, and the said annular boss on the said first shield. The present invention will be described by way of examples with reference to the accompanying drawings in which: Fig.l shows a schematic cross section of a rolling bearing with a sealing unit according to the teachings of the are sent invention; Fig.2 shows the Fig.I bearing with a modified version of the sealing unit according to the present invention. Number 1 in Fig.1 indicates a rolling bearing of any known type, e.g. a ball bearing, comprising an inner ring 2, an outer ring 3, respective face-to-face tracks 4 formed on rings 2 and 3, and rolling bodies 5 rolling betewwen tracks 4 in sucii a manner as to enable mutual rotation of rings 2 and 3. Rings 2 and 3 -define an annular chamber 6 housing rolling bodies 5 and closed at its oppo site ends (only one of which is shown for simplicity, bearing 1 being symmetrical) by respective sealing units 7 housed inside respective seats 8. Each sealing unit 7 com- prises an outer sliiel 10 designed to fit integral with an operatively-rotating member, e.g. inner ring 2, and an inner shield 11 designed to fit integral with the other mutually-rotating member, e.g. outer ring 3, and fitted facing and beside the said outer shield 10. i3oth shields 10 and 11 are substantially rigid and preferably formed from pressed sheet metal. One of the said shields (shield 11 in the embodiment shown) is provided. in integral manner, with an annular sealing niember 12 made of elastically-deformable elastomeric material, such as rubber, preferably secured o respective shield 11 by means of a known bonding process during curing. Sealing member 12 is design ed to cooperate in sliding manner with a respective track 13 on shield 10, in such a way as to provide for sliding axial sealing between shields 10 and 11. For this purpose, tlie said sealing member 12 is provided, at t}ie radiallyinner edge of shield 11, with a projecting oblique radial annular lip 14 designed to interfere with shield 10, when unit 7 is operative, in such a way as to flex and exert on track 13 sufficient prearranged pressure for ensuring axial sealing. In accordance with the present invention, track 13 is carried on a flange portion 15 of shield 10, said portion 15 being arranged facing sealing member 12 and extending perpendicularly in relation to a corresponding sleeve portion 16 of shield 10, by means of which portion 1G shield 10 is fitted onto ring 2. Flange portion 15 is provided peripherally outwards with an annular boss 18 defining a concavity 19 on a front outer surface 20 of shield 10, and a corresponding convexity 21 on an inner surface 22 of shield 10, opposite surface 20 and defining track 13. Facing surface 22, shield 11 presents a front face 23 entirely covered by elastomeric member 12 which, starting from lip 14, extends over the whole of face 23 up to the outer edge of shield 11. The said elastomeric member 12 comprises a peripherally-outer annular appendix 24, opposite lip 14 and designed to click into seat 8 for securing shield 11 to ring 3, and an axial annular rib 25 projecting towards and perpendicularly in relation to surface 22, but without touching it. The said rib 25 is formed integral with jneiiiber 12 between lip 14 and boss 18 of shield 10, and defines, together with surface 22, a supplementary axial labyrinth seal designed to protect sliding sealing lip 14. Shield 11 is preferably provided, along the centre line, with an annular strengthening boss 28 forming the convexity towards face 23 and having a radially-inner end 29 at which is formed rib 25. In accordance with tlie present invention, tlie free end of rib 25 lies substantially in tlie same plane passing through the top of convexity 21, as siiown.clearly in Fig.1, in such a manner as to further improve the labyrinth sealing action exerted by rib 25. Clearly, 1)y virtue of shield 10 being fitted onto a rotat ing member and being the outermost shield on sealing unit 7, flange portion 15 acts as a centrifugal member for hurling away from chamber 6 any external contaminants coming into contact with shield 10. Tests conducted by tlie present Applicant have shown, however, that such centrifugal action is considerably improved, as compared with known sealing units, by tlie presence of boss 18, in that, concavity 19 sucks in and hurls tile said contaminants centrifugally and obliquely away from shield 10 along a path enabling easy disposal, whereas corresponding convexity 21 prevents any remaining external contaminats from entering between shields 10 and 11, tlie said contaminants being collected in drops which are spun off and back onto outer surface 20 wliere they may be spun off by concavity 19. Finally, by virtue of rib 25 and its location flush with tile top of convexity 21 defined by boss 18, any contaminant managing to get past boss 18 is arrested by mem- ber 12 and sucked, by virtue of mutual rotation, onto shield 10, whereas leakage of any grease lubricating lip 14 is prevented . In like manner, providing a sealing unit of known general structure with simple, lolf-cost features, such as boss 18 and rib 25, enables a surprisingly big im provement in sealing efficiency, in addition to prolonged working life of the sliding lip which is thus substantial- ly untouched and unaffected by external contaminants. The bearing 1 sllown in cross section in Fig. 2, and identical to that of Fig. i, is provided witlI a sealing unit 30 constituting a possible variation of unit 7 as described above. For tlie sake of simplicity, details similar or iden tical to those already described are indicated using tile same numbering system. The only difference between sealing units 7 and 30 consists in the fact that radially-inner sealing lip 14 on unit 30 presents a substantially Y-sliaped radial section and comprises a first end 31 extending obliquely and substantially axially towards shield 10 and cooperating, in use, with track 13 so as to define the required sliding axial seal, and a second end 32 extending obliquely and substantially radially towards sleeve 16 so as to cooperate, without sliding, with the said sleeve 16 and so define, together with shield 10, a supplementary radial labyrinth seal. In like manner, the sliding axial seal is enclosed between a double labyrinth seal define by rib 25 with respective boss 18 and by end 32, with maximum protection of the sliding part of lip 14 and the formation of a chamber 33, between rib 25 and end 32, for housing a store of grease for lubricating tie sliding parts. As for the rest, operation of sealing unit 30 is the same as for sealing unit 7, but with even better sealing performance by virtue of grease-filled chamber 33. The advantages of the sealing unit according to the present invention will be clear from the foregoing description. To those skilled in the art it will also be clear that changes may be made to the invention as described herein witiout, however, departing from the scope of the sanie.

Claims: C LAIS 1) - A sealing unit designed for insertion between two mutually-rotating members, particularly rolling bearings, and comprising a first rigid shield designed to fit onto one of tlle said members, and a second rigid shield designed to fit onto the other of the said members and provided, in integral manner, with an annular sealing nember made of elastomeric nlateriai and designed to cooperate, in sliding manner, with at least one respective sliding track on the said first shield, for exerting axial sealing action on the said first shield; characterised by the fact tIsat tulle said first shield comprises a radial flange portion bearing tulle said track and provided peripherally outwards with an annular boss defining an annular concavity, on a front outer surface of the said first shield, and a corresponding annular convexity, on an inner surface of the said first shield defining tlie said track, the said sealing member being arranged facing the said flange portion and comprising a axial annular rib extending towards and perpendicular in relation to the said inner surface of the said first shield, but without touching the said inner surface, in such a manner as to define a supplementary axial labyrinth seal, tile said rib being formed integral with the said sealing member between a projecting oblique radial annular lip on the said sealing member, said lip being designed to interfere with the said first shield for aciiieving the said sliding axial sealing action, and t!ie said annular boss on tlie said first shield. 2) - A scaling unit as claimed in Claim 1, characterised by the fact that tlie said elastomeric sealing member extends over an entire front face of the said second shield, facing tlie said inner surface of the said first shield, and comprises a peripiierally-outer annular appendix, opposite tlie said lip, designed to click inside a seat on one of the said members, for securing to the said member the said second shield. 3) - A sealing unit as claimed in Claim 1 or 2, character- ised by tlie fact tliat tile said second shield is provided along its centre line with an annular strengthening boss at a radially-inner end of which is formed the said axial annular rib. 4) - A sealing unit as claimed in one of tlie foregoing Claims, characterised by the fact that tile said oblique radial annular lip presents a substantially Y-sltaped radial section, a first end of tile said lip cooperating, in sliding manner, with the said track so as to define the said axial seal, and a second end of tile said lip cooper- ating witll a sleeve portion of tlte said first shield so as to define, with the same, a non-sliding radial seal designed to enclose tlie said sliding axial seal, formed by the said first end, between a double labyrinth seal defined by the said annular rib and by the said second end of the said oblique lip. 5) - A sealing ujjit as claimed in one of tlie foregoing Claims, characterised by the fact that the free end of the said axial annular rib lies substantially in tlie same plane passing through the top of the said convexity defined by the saict annular boss OII tile saitl inner surface of tlie said first shield.

Inventors: COLANZI, FRANCO, VIGNOTTO, ANGELO
Applicants: RIV-SKF OFFICINE DI VILLAR PEROSA S.P.A
Application year: 1986
Main classification: F16C33
IPC codes: F16C33