ARTICULATED VEHICLE STEERING

1,132,615. Articulated vehicles; power steering. EATON YALE & TOWNE Inc. 30 June, 1966 [4 May, 1966], No. 29398/66. Addition to 1,131,651. Heading B7H. [Also in Division E1] In a double-articulated vehicle comprising a central control unit 10 pivoted about vertical axes to front and rear ground-engaging traction units 11, 12, a transmission means on the control unit, driven through a drive-shaft by a prime mover on the rear unit and driving through drive-shafts the front and rear units, the driveshafts and pivot axes lying in the central longitudinal vertical plane of the vehicle in the straight-ahead position, steering means 22 to 25 are provided to pivot the front and rear units relatively to the central unit and a link 42 is provided connecting the rear unit on one side of said longitudinal vertical plane to the front unit on the other side of the plane, the arrangement constraining the front and rear units to pivot in opposite senses relative to the central unit. Movement of a steering wheel S actuates a closed-centre spool valve 32, which is pivoted at one end to the front unit 11 to connect a highpressure line 35 to one of lines 36 and 37, which are respectively connected to the opposite ends of four steering rams 22, 23, 24 and 25, and the other of the lines 36 and 37 to a low-pressure line 38 to pivot the units 11, 12 in opposite senses relative to the central unit. The units 11, 12 may be pivoted in the same relative sense to provide crabwise movement of the vehicle by adjusting the length of the link 42 which comprises an hydraulic cylinder 43. To do this a valve 47 is actuated to connect the low-pressure line 38 to one end of the cylinder 43 and the other end of the cylinder 43 to a reservoir 50. Simultaneously a dump valve 48 is actuated by a solenoid 55 to interconnect the lines 36 and 37 and hence the opposite ends of the steering rams 22 to 25.