Support assembly for moveable shafts
A support assembly includes a casing having an internal mounting seat, a bearing unit mounted on the internal mounting seat of the casing, and a first sealing device. The bearing unit includes a radially inner ring, a radially outer ring, and a plurality of rolling elements interposed between them. The first sealing device includes a first shield fixed to the radially outer ring, a second shield fixed to the radially inner ring and positioned axially internal with respect to the first shield, and a protective shield interference fit on a cylindrical seat of the casing and positioned axially internal relative to the second shield. The first and second shield define a first labyrinth seal between them. The protective shield and the second shield define a second labyrinth seal between them. The protective shield extends axially inward to an axial boundary of the casing at the cylindrical seat.
1 . A support assembly comprising:
a casing comprising an internal mounting seat;
a bearing unit mounted on the internal mounting seat of the casing and having an axis of rotation, the bearing unit comprising:
a radially inner ring;
a radially outer ring;
a plurality of rolling elements between the radially outer ring and radially inner ring;
wherein the casing has an axially inner end and an opposite axially outer end spaced apart along the axis of rotation; and
a first sealing device comprising:
a first shield fixed to the radially outer ring;
a second shield fixed to the radially inner ring and positioned axially internal with respect to the first shield, wherein the first shield and the second shield define between them a first labyrinth seal; and
a protective shield interference fit on a cylindrical seat of the casing and positioned axially internal relative to the second shield;
wherein the protective shield and the second shield define between them a second labyrinth seal; and
the protective shield extends axially inward within an axial boundary of the casing defined at the cylindrical seat of the casing.
2 . The support assembly of claim 1 , wherein the protective shield comprises:
a radially outer first cylindrical portion that is interference fit on the cylindrical seat of the casing; and
a first flange portion integrally connected to an axially outer end of the cylindrical portion and extending radially inward therefrom.
3 . The support assembly of claim 2 , wherein the second labyrinth seal comprises:
a first section defined between an inner radial end of the first flange portion and a second cylindrical portion of the second shield fixed to the radially inner ring;
a second section defined between the first flange portion and a second flange portion of the second shield; and
a third section defined between a radially inner surface of the radially outer ring and a radially outer end of the second flange portion.
4 . The support assembly of claim 3 , further comprising a radially outer volume adjacent the second section of the second labyrinth seal and defined between the first flange portion and an axially inner surface of the radially outer ring, wherein the radially outer volume is filed with lubricating grease.
5 . The support assembly of claim 4 , further comprising an axial distance between an axially outer annular surface of the first flange portion and the axially inner surface of the radially outer ring of between 1.9 mm and 2.1 mm.
6 . The support assembly of claim 5 , further comprising an axial distance between the axially outer annular surface of the first flange portion and an axially inner surface of the second flange portion of between 1.5 mm and 1.7 mm.
7 . The support assembly of claim 6 , wherein the first shield further comprises an elastomeric element formed on a radially outer surface of the first shield, the elastomeric element comprising a sealing lip in contact with a radially outer surface of the radially inner ring.
8 . The support assembly of claim 3 , wherein:
the first flange portion comprises a first frustoconical portion between the radially outer end and a radially inner end of the first flange portion;
the second flange portion comprises a second frustoconical portion between the radially inner end and a radially outer end of the second flange portion; and
an inclination of the first frustoconical portion is equal to an inclination of the second frustoconical portion.
9 . The support assembly of claim 8 , wherein the protective shield comprises a thickness between 0.75 mm and 0.85 mm.
10 . The support assembly of claim 9 , further comprising an interference between the protective shield and the cylindrical seat of the casing between 0.05 mm and 0.15 mm.
11 . The support assembly of claim 3 , further comprising a radial distance between the radially inner end of the first flange portion and the cylindrical portion of the second shield of between 0.4 mm and 0.6 mm.
12 . The support assembly of claim 1 , wherein the radially outer ring comprises a convex radially outer surface, wherein the internal mounting seat comprises a shape substantially similar to the convex radially outer surface of the radially outer ring.