| 摘要 |
A rack and pinion assembly in which a rack bar (1) is longitudinally displaceable through a housing (2) by rotation of a pinion (4) engaging with the rack (3). The rack bar (1) is supported in engagement with the pinion (4) by a plastics moulded bearing member (7) having a saddle-shaped bearing part (9) and a tubular retaining part (8) which is displaced longitudinally from the part (9). The bearing part (9) is of saddle-shape to straddle the rack bar (1) opposite to the region of engagement between the rack and pinion teeth and has a resilient bearing surface which biases the rack bar laterally into engagement with the pinion. The straddling portions of the saddle-shape restrain the rack bar from displacement in the direction of the pinion axis (4a). The retaining part (8) locates the bearing member (7) in the housing (2) and restrains that member from rotation (by keying engagement between rib (11) and channel (12)) and from longitudinal displacement by its co-operation in an annular recess (15). The bearing member (7) can co-operate with the recess (15) by snap engagement during initial location of the bearing member. Preferably the saddle-shaped bearing part (9) has three discrete circumferentially spaced bearing surfaces each of part cylindrical profile which slidably engage with a complementary cylindrical profile on the rack bar (1). The bearing member (7) can be a one piece moulding in resilient plastics and the bearing part (9) can be pre-loaded by its assembly with the rack bar to constantly bias the rack bar into engagement with the pinion.
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