GB789863A - Power steering mechanism - Google Patents

Abstract

789,863. Vehicle power steering. FORD MOTOR CO., Ltd. June 15, 1956 [June 15, 1955], No. 18620/56. Class 79(5) In a steering gear mechanism having a worm 16 rotatably mounted in housing 11 a torsion rod 36 passes through a bore in the worm 16, is anchored at one end thereto and is rotatably connected to a threaded sleeve 47 which is engaged by a nut 52 axially slidable but non-rotatably connected to the worm 16, whereby torsional deflection of the bar 36 causes axial movement of the nut 52 and a valve spool 63 associated therewith, the spool interconnecting a pump 74 and a hydraulic piston and cylinder unit 18. As shown a shaft 58 carrying the steering wheel (not shown) is connected by a rivet 65 and a rubber sleeve 62 to the sleeve 47 which is splined and brazed at 46 to the torsion rod 36 extending through the worm 16. The worm 16 meshes with a worm wheel carried by a shaft 12 connected to the steering linkage (not shown). The rod 36 has an axially adjustable splined connection 37 to the worm 16 which has an extension 29 having a lost motion splined connection 49 with the sleeve 47. The sleeve 47 carries external threads 51 having a helix angle of about 61 degrees and engaging the nut 52 which carries a washer 54 splined to the worm extension 29. The nut 52 is connected by a flange 64, a spacer 66 and a retaining ring 67 to the valve spool 63 co-operating with a fixed ported sleeve 68. In operation manual rotation of the shaft 58. causes torsional deflection of the rod 36 owing to the steering load, such deflection causing relative rotation between the worm 16 and sleeve 47. Due to the connections of the nut 52 to the worm 16 and sleeve 47 such relative rotation causes axial movement of the nut 52 and hence of the spool 63 relative to the sleeve 68. The axial movement of the spool 63 causes one piston 19 to be subject to the outlet pressure of the pump 74 and the pressure against another piston 19 to be connected to a tank 78 whereby the pistons 19 are moved in unison, the pistons being connected to the shaft 12 to give power assistance to the steering. In the event of hydraulic failure the lost motion in the connection 49 is taken up and manual steering is effected.