US 11,851,837 B2
Hydraulic power shovel with tamping function
Gilles Florean, Lyons (FR)
Assigned to Robert Bosch GmbH, Stuttgart (DE)
Filed by Robert Bosch GmbH, Stuttgart (DE)
Filed on Dec. 8, 2020, as Appl. No. 17/115,419.
Claims priority of application No. 1913948 (FR), filed on Dec. 9, 2019.
Prior Publication US 2021/0172141 A1, Jun. 10, 2021
Int. Cl. E02D 3/046 (2006.01); E02F 3/36 (2006.01); E02F 3/65 (2006.01); E02F 3/96 (2006.01)
CPC E02D 3/046 (2013.01) [E02F 3/3663 (2013.01); E02F 3/651 (2013.01); E02F 3/962 (2013.01)] 4 Claims
OG exemplary drawing
 
1. A hydraulic power shovel comprising:
a frame supporting a turret equipped with an arm;
a power cylinder linked to the arm and configured to press on the turret;
a hydraulic installation including an adjustable flow pump configured to supply the power cylinder via a slide valve and a hydraulic liquid tank;
a control unit operably connected to a first control member and a sensor, the first control member actuated by an operator and configured to generate a first operator control signal, the sensor configured to generate a sensor signal corresponding to pressure and temperature of hydraulic liquid in the power cylinder, wherein a vapour pressure diagram of the hydraulic liquid is available in the control unit;
a comparator configured to receive the sensor signal, to compare the sensor signal to a vapour pressure curve, and to generate a pump control signal for the adjustable flow pump; and
a second control member activated by the operator and configured to generate a second operator control signal for controlling an operating mode of the control unit,
wherein the control unit is configured to control operation of the hydraulic power shovel:
in a normal operating mode according to which the slide valve and a flow rate of the adjustable flow pump are set as a function of the first operator control signal from the first control member; and
in a tamping mode according to which the arm is configured for a free descent under effect of its weight as requested by the first control member,
wherein the slide valve fully opens an output of the power cylinder to the hydraulic liquid tank, and
wherein the adjustable flow pump is configured to supply an input of the power cylinder to maintain a pressure therein above a vapour pressure of the hydraulic liquid but below atmospheric pressure, at the temperature of the hydraulic liquid in the power cylinder.