GB743117A - Improvements in the control of power-operated systems for tractor hitch linkages - Google Patents

Abstract

743,117. Agricultural implements. FERGUSON, Inc., H. Feb. 21, 1951, No. 4205/51. Class 6 (1). [Also in Group XXIX] In a tractor hydraulic-lift system a release valve 190 is provided for exhausting the hydraulic ram 36 when the draught-control linkage 26, 101 moves beyond its normal travel, the valve being adapted to open upon actuation by the linkage and to remain open subsequently, independently of the linkage, until the oil supply to the ram is terminated by the tractor operator. The system is similar to that described in Specifications 470,069 and 470,087 and comprises a ram acting on an arm 41 connected to a rock-shaft 42 from which the liftarms 43 extend rearwardly. The upper hitchlink is connected to the rocker 26, movement of which, in response to variations in draught load, actuates a control valve 50 connected between the oil-pump 46 and ram 36, as is described in Specification 743,118, [Group XXIX]. The rocker drives a plunger 101 connected by a link 109 to a pivoted arm 112 carrying a roller 114. Excessive movement of the rocker 26 causes the roller to strike a push-rod 210 and open the valve 190 through a further rocker (Fig. 4, not shown). The valve (see Group XXIX) comprises a spring-loaded double-piston sliding in a composite cylinder, the piston areas being so chosen that the valve is normally closed but when operated by the linkage 101, 109, 112, 210, it opens automatically and thereafter remains open until the fluid supply is interrupted by manual operation of the hand control 60. Specification 550,142 also is referred to.