Patent GB-503931-A (GB)
Title: Improvements in or relating to levelling devices
IPC: E02F9/02
Filed: 1937-10-16
Abstract: 503,931. Automatic control systems. RUSTON-BUCYRUS, Ltd. Oct. 16, 1937, No. 28215. Convention date, Oct. 16, 1936. [Class 38 (iv)] Attitude.-The base 11 of an excavator or other machine, Fig. 1, is supported on four hydraulic jacks 12, with each of which is associated a pump driven by an electric motor and a bleeder valve. Electric switches, responsive to tilting of a diagonal are adapted to cause the operation of appropriate pumps and valves to adjust the jacks to restore the base to a level condition. Other switches responsive to the condition of the jacks are adapted to override this operation to equalize the action of the jacks and also to prevent any corner from being unsupported. Manual control of all pumps and valves may be applied at any time and the action of the automatic control may be suspended automatically when the excavator is travelling. The invention may be applied also to jacks actuated electrically or mechanically. Fig. 2 shows the arrangement of a jack and its associated switches. A sliding weight 40 operated by a connection from the jack is adapted to open normally closed switches. 43, 44 at the limits of its travel and to close a normally open switch 42 on approaching full .extension. The jack is housed in the base 11 so as to permit relative vertical movement defined by abutments 20, 26 and a switch 29 is closed should the gap 28 close due to dangling of a jack. Fig. 5 shows the control circuits, the elements appropriate to each corner being arranged in separate vertical series and pairs of opposite corners being represented respectively in the first and third, and second and fourth series; corresponding elements are aligned horizontally. Thus the first series includes switch 44 which opens when the jack is fully collapsed, switch 42 which closes when the jack is almost fully extended and switch 43 which opens when the jack is fully extended. Elements on the line C represent solenoids each operating a valve adapted to bleed a jack cylinder at approximately the same rate as a pump P would fill it; on line D are starting switches for the motors driving the pumps; and on line E push buttons for operating pumping and bleeding elements at will. When the level along one diagonal of the base is disturbed one of a pair of switches J1 J3 or J2 J4 is closed; preferably these are actuated as described in Specification 503,932 [Group XXXVII], by means which magnify the movement. One of the switches H is thus closed whereby are energized: (1) a pumpstarting switch D through a switch 43, (2) a bleeding valve solenoid appropriate to the opposite carrier of the base and (3) a lead to the open switch 42. When the jack being pumped approaches its maximum extension this switch closes and a bleeder valve appro. priate to a jack on the other diagonal is opened to enable the levelling to proceed after automatic lowering of the level of that diagonal. Should the raising of the base at one corner cause either of the jacks on the other diagonal to dangle a switch 29 will close and operate a switch (line G) to start both pumps operating on that diagonal. A switch 54 isolates all automatic control circuits and may be opened by current in any circuit 73 operative whn the excavator is travelling. Valves in pipes interconnecting the jack cylinders may also be opened automatically at such times, so that the jacks may accommodate themselves to unevenness in the ground.