A system and method for the controlled lowering and lifting of a load are disclosed. The system and method may include operating a work machine having a hydraulic system including a hydraulic actuator for supporting a load, a first control valve in fluid communication with the actuator, and a controller for operating the first control valve. In one embodiment, the controller includes a first algorithm for operating the first control valve in a load lowering operation. When an operational fault within the hydraulic system is detected, the controller can be configured to enter into a safe lowering mode. In the safe lowering mode, the first algorithm is disabled and a pulse width modulation (PWM) current is sent from the controller to the first control valve. A user interface is provided to allow an operator to control the PWM current duty ratio to allow the load supported by the actuator to be lowered.

In a hydraulic drive system for an electrically driven hydraulic work machine that executes flow rate control of a hydraulic pump by controlling a rotation speed of an electric motor to drive a hydraulic pump to supply a hydraulic fluid to a plurality of actuators, and power consumed by the electric motor reliably limited within a range of preset maximum allowable power without unnecessary degradation of responsiveness of the electric motor. To this end, a controller includes a maximum angular acceleration limitation section (allowable rate computation section and rate limitation section), computes hydraulic power consumed by a main pump, computes a maximum angular acceleration allowed for an electric motor on the basis of a magnitude of the hydraulic power and a preset maximum allowable power consumable by the electric motor, and limits an angular acceleration of the electric motor not to exceed the maximum angular acceleration.

A clamp implement and a control system for controlling the clamp implement such that the clamp implement can be caused to follow motion of a bucket or other primary implement in a selected mode of operation. In another mode of operation, the claim implement can be caused to move independently of the primary implement.

A working machine includes a branched tube connected to a branched portion branching from an operation fluid tube, a plurality of input tubes connected to the second actuator valves, a plurality of output tubes connected to a pressure receiver portion of the second hydraulic device, a main tube connected to the third actuator valve, and a relay device, and the relay device includes a plurality of input ports connected to the plurality of input tubes, a plurality of output ports connected to the plurality of output tubes, a plurality of first flow lines connecting between the plurality of input ports and the plurality of input ports, a main port connected to the main tube, a branched port connected to the branched tube, and a second flow line arranged between the plurality of first fluid lines to connect between the main port and the branched port.

To be capable of dealing with a machine body lifting operation or a sudden operation, while improving energy efficiency, during a boom-lowering operation, and achieving the reduction of the number of parts, in a construction machine equipped with a boom. It is configured such that a first region Y1 at which a recovery valve passage 16e is opened and a supply valve passage 16f is closed and a second region Y2 at which the recovery valve passage 16e and the supply valve passage 16f are opened, are provided at an operating position of a first boom control valve 16 during the boom lowering operation, and the first boom control valve 16 is positioned at the first region Y1 when neither a machine body lifting operation nor the sudden operation is performed during the boom-lowering operation, and at the region Y2 when the machine body lifting operation or the sudden operation is performed.

To achieve the improvement of recovery efficiency from a rod end oil chamber to a head end oil chamber during extending operation of a stick cylinder, and at the same time, to prevent an operation speed of the stick cylinder from being impaired when recovery is impossible., as well as to achieve the reduction of the number of parts, in a construction machine equipped with a stick. It is configured such that a first region Y1 at which a discharge valve passage 14g is opened while being throttled and a second region Y2 at which the discharge valve passage 14g is wider opened than at the first region Y1 are provided, in an operating position of a stick control valve 14 during extending operation of the stick cylinder, and if recovery from the rod end oil chamber 9b to the head end oil chamber 9a during extending operation of the stick cylinder 9 is possible, the stick control valve 14 is caused to be positioned at the first region Y1, and if the recovery is impossible, positioned at the region Y2.

A system for controlling a winch assembly having a hydraulic motor, a drum, a cable, and a cable tension sensor. A controller is configured to access a winch load threshold defining a hold zone and a reel zone, and one of the hold zone and the reel zone including loads greater than the winch load threshold and another of the hold zone and the reel zone including loads less than the winch load threshold. The controller is further configured to determine whether the winch assembly is operating within the hold zone or the reel zone, and generate a zero flow command while the winch assembly is operating within the hold zone to prevent rotation of the hydraulic winch motor, and generate a pressure differential command while the rotatable winch drum is operating within the reel zone to permit rotation of the hydraulic winch motor.

The present disclosure relates to a safety system for a construction machine, and the safety system for a construction machine according to the exemplary embodiment of the present disclosure includes: a pilot pump which supplies a pilot working fluid; multiple spools which are operated by the pilot working fluid to control a supply of a main working fluid and each have a signal unit formed in one region thereof; a signal line which sequentially connects the pilot pump and the signal units of the multiple spools and discharges the pilot working fluid, which is supplied by the pilot pump, to a hydraulic tank; and a pressure sensor which measures pressure in the signal line.

There is provided a hydraulic driving device for working machine having operability handling a change in burden weight in a front working device due to a loaded burden and the like when the working machine that accumulates energy in an accumulator and recovers and regenerates the energy performs an operation of lowering the front working device. A hydraulic driving device 5 includes a main pump 101, a boom cylinder 3, a tank 20, a flow rate control valve 6, an accumulator 300, a first differential pressure control valve 201, and a second differential pressure control valve 202. The first differential pressure control valve 201 is located between the boom cylinder 3 and the accumulator 300. The first differential pressure control valve 201 performs control on discharge oil from the boom cylinder 3 such that a differential pressure between before and after the flow rate control valve 6 becomes a target differential pressure. The second differential pressure control valve 202 is located between the accumulator 300 and the tank 20. The second differential pressure control valve 202 performs control on the discharge oil such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve 6 and the first differential pressure control valve 201 becomes the target differential pressure. The first and the second differential pressure control valves 201 and 202 are configured such that the target differential pressure increases according to an increase in pressure of the discharge oil.

A hydraulic system includes a hydraulic actuator to be operated by an operation fluid, a first hydraulic pump to output the operation fluid, a second hydraulic pump to output the operation fluid, a control valve to which the operation fluid outputted from the first hydraulic pump is supplied, the control valve being configured to control the operation fluid that is to be supplied to the hydraulic actuator, a first fluid tube connecting the control valve to the hydraulic actuator, a second fluid tube to which the operation fluid outputted from the second hydraulic pump is supplied, the second fluid tube being connected to the first fluid tube, and a first switching valve disposed on the second fluid tube. The spool includes a communicating fluid passage being configured to supply the operation fluid to the first inner fluid passage, the operation fluid being received by the pressure-receiving port.