Hydraulic digging machines

Claim 2

In a hydraulic digging machine for loading, carrying and unloading soil and other materials having a boom, a digging arm pivotally mounted at the outer end of said boom and supporting a bucket for loading, carrying and unloading said soil, a first hydraulic power means for providing a first actuation force on said digging arm to swing said digging arm against the resistance of said soil during loading, said first hydraulic power means including a hydraulic piston and cylinder assembly, the improvement comprising: a second hydraulic power means for selectively providing a second force to assist said first hydraulic power in swinging said digging arm to overcome the resistance of said soil during loading, said second hydraulic power means including a rotary hydraulic motor for driving a winch, said winch having a wire attached thereto and detachably connected to said digging arm for assisting said first hydraulic power means.

Claim 3

A machine according to claim 1, in which said first hydraulic power means is connected via a conduit connected to a pressure fluid pump, said conduit having a branch conduit connected to said second hydraulic power means through a valve, which in a first and effective position admits pressure fluid to said second hydraulic power means, and in a second and neutral position closes the supply of pressure fluid to said second hydraulic power means and connects the same to a return conduit leading to an oil reservoir for said pump, said pump being connectable with the first hydraulic power means through a control valve which permits fluid to return to said reservoir through said return conduit which includes an adjustable restriction to provide a desired raised pressure in the return conduit, and said return conduit from said second hydraulic power means is connected to said return conduit which includes the restriction and has said raised pressure, said valve in said branch conduit leading to said second hydraulic power means being automatically controlled by a fluid pressure responsive device adapted to shift said valve to its effective position when a prEdetermined fluid pressure is exceeded in the pressure fluid conduit to said first hydraulic power means and to shift said valve back to its neutral position when said fluid pressure is thereafter decreased below a predetermined value.

Claim 4

A machine according to claim 2, in which said fluid pressure responsive device includes an electromagnetic power device adapted to move said valve between its neutral and effective positions, and the electric current to the electromagnetic device is controlled by a microswitch adapted to be closed by a pressure responsive device influenced by the pressure fluid in said conduit to said first hydraulic power means.