Abstract: PCT No. PCT/US79/01033 Sec. 371 Date Nov. 29, 1979 Sec. 102(e) Date Nov. 29, 1979 PCT Filed Nov. 29, 1979Heretofore the capability of operating a system (10), which supplies fluid to a hydraulic circuit (12), selectively at either a high or a low flow rate with only a single pressurized fluid source (14) has not existed. Such a system (10) includes a control valve structure (16) for controlling delivery of fluid from the source (14) to drive the circuit (12) and a flow control (22) for metering a portion of the fluid to the circuit (12). The capability of operating such a system (10) selectively at either a high or a low flow rate is advantageous in some modes of operation of the circuit (12). Herein, hydraulic circuitry (86) serves for controlling the magnitude of the portion in response to application of a signal thereto and a device (78) is provided for selectively applying the signal to the circuitry (86) for selectively directly controlling the magnitude of the portion.

Abstract: A control valve arrangement is disclosed for regulating fluid communication between a source of fluid under pressure and a double-acting hydraulic motor, including a housing defining a bore, an inlet chamber in communication with the bore and the pressure source, a pair of service chambers in communication with the bore and the hydraulic motor for actuation thereof, and a plurality of drain passages in communication with the bore, a pressure transmitting circuit defined in the housing and in communication with the bore, a relief valve which is in responsive communication with the pressure transmitting circuit for variably controlling the pressure in the inlet chamber, and a spool reciprocably disposed in the bore of the housing and having a plurality of lands for blocking communication between the inlet chamber and the service chambers in a neutral position, with the spool having metering slots for communicating fluid from the inlet chamber radially outwardly to a selected one of the service chambers and to t

Abstract: A supplementary hydrostatic front wheel drive for a motor grader or the like utilizes pump flow from an already existing implement system as the source of supply to operate the drive wheel motors. The drive wheel motors are of the variable displacement over center type, and the system provides equal flow to both drive wheel motors to establish a synchronized rotational speed of both drive wheel motors. The displacements of the drive wheel motors are responsive to vehicle ground speed. The drive wheel components may include friction driving means which are responsive to the primary vehicle drive system.

Abstract: A closed center control valve for double acting motors having an inlet passage and a pair of control passages is provided with pre-sized restrictions in the control passages to control the flow rate to the motor so that a pre-selected velocity of movement of the motor is achieved.

Abstract: A hydraulic control system is disclosed for selectively directing fluid to a pair of reciprocable jacks connectably disposed intermediate a frame and an implement such as a bulldozer blade for tilting and tipping the blade relative to the frame. The control system includes a fluid supply source, a flow divider valve which is in fluid communication with the supply source for providing equal flow to a pair of outlet paths, a first control valve arrangement for selectively communicating fluid from one of the outlet paths to either end of one of the jacks, and a second control valve arrangement for selectively communicating fluid from the other one of the outlet paths to either end of the other one of the jacks.

Abstract: A fluid control circuit for regulating flow from a source of fluid under pressure to a hydraulic motor, including a control valve having a movable spool for communicating fluid entering an inlet chamber from the source with service chambers in communication with the motor, an inlet relief valve selectively pressurizing the inlet chamber in response to spring means and signal fluid received from the service chambers through signal passages. The control valve and its spool are configured to insure that the signal passages are always in positive communication either with one of the service chambers or a drain in order to facilitate manipulation of the spool. The control valve is also adapted to communicate signal fluid to the relief valve prior to communication of either service chamber with the inlet chamber in order to precondition the relief valve and improve response of the motor to manipulation of the control valve.