Massey-ferguson Services N.v.

Robert E Yapp

Derek J Smith

John D Smith

A tractor hydraulic control system of the kind comprising a power lift with a hydraulic actuator (12) and a main control valve (17) controlling the supply of fluid from a pump (19) to the actuator, the system including selector valve means (50) interconnected with the main control valve (17) and movable between a first position in which flow to and from the actuator (12) occurs via the selector valve means under the control of the main control valve and the associated system control mechanism (28) and a second position in which the actuator is hydraulically locked in a given position and an external services outlet (51) is placed in communication with the pump. Linkage means (60,61,62) operatively connects the selector valve means (50) and the system control mechanism (28) to condition the main control valve (17) to cause the pump (19) to supply fluid to the external service outlet (51) via the selector valve means on movement of the selector valve means to the second position. Preferably, the main control valve (17) is biased towards a position in which the pump delivery its maximum output flow to the selector valve means and movement of the selector valve means to its second position is arranged to disconnect the control mechanism from the main control valve.

Tractor hydraulic control systems

A control lever arrangement (10) for longitudinally moving an actuating member such as a Bowden cable (11) between first and second positions. The arrangement includes first (13) and second (14) mutually inclined cam slots and a control lever (15) which has a handle at one end and which is pivotally mounted (20) at the other end on a follower (16) for engagement with the first cam slot. The lever (15) carries guidance means (17) for engagement with the second cam slot and is connected (21) with the actuations member (11), so that, as the control lever is rotated (X1,X2) about its mounting (20) on the follower (16) to move the actuating member between its first and second positions, the follower moves along the first (13) cam slot as the guidance means (17) moves along the second cam slot (14) and the point of contact of the follower (16) with the first slot (13) moves across the line of action (33) of the actuating member (11) so that the lever goes over-center.

Control lever arrangements

A power steering system has a valve between the pump and steering unit. The valve maintains a constant pressure differential so that the pump is unable to deliver aerated fluid to the unit in the event of loss of fluid or fracture of a pipe.

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Chillington, United Kingdom

Robert E Yapp