Swing valve circuit

In swing apparatus having a swing bracket support member, a swing bracket mounted on said swing bracket support member for side-to-side swing movement with respect thereto, power means connected with said swing bracket for causing said swing bracket to swing in opposite directions with respect to said swing bracket support member in response to flow of fluid in opposite directions to and from said power means, a control system for controlling flow to and from said power means comprising:

• a first and second pair of lines for conducting fluid to and from said power means, one of said lines directing flow to said power means to swing said swing bracket in one direction and the other of said lines directing flow to said power means to swing said swing bracket in the opposite direction, a first pressure reducing valve controlling said first one line and a second pressure reducing valve controlling said second one line, pilot lines connected to said one lines and to said reducing valves to pressurize said reducing valves toward a closed position to limit pressure to said power means through said one lines to a predetermined maximum pressure, first and second metering valves operable to permit flow of fluid from said power means through said first and second other lines, respectively, during swing movement of said swing bracket, pilot lines connected to said metering valves, said first and second one lines including as portions thereof first and second supply and intake and exhaust lines, respectively, said supply lines connected to said one lines through said reducing valves and to said intake and exhaust lines, check valves connecting said supply lines with said intake and exhaust lines, said metering valve pilot lines being connected to said intake and exhaust lines, respectively, to move said metering valves toward an open position only when a predetermined minimum pressure exists in said intake and exhaust lines, respectively, interconnecting lines and check valves in said interconnecting lines, said interconnecting lines interconnecting said first and second said one and other lines, respectively, to permit flow from said one lines to said other lines and prevent reverse flow, and cross lines connecting said intake and exhaust lines, respectively, exhaust check valves therein permitting flow from said cross lines to said intake and exhaust lines, respectively, but preventing flow to said cross line from said intake and exhaust lines, respectively, and drain lines connecting said other lines, respectively, to said cross lines between said exhaust check valves.

Swing apparatus having a swing member pivotally mounted for side-to side swinging movement, a pair of extensible and contractable fluid actuators, each of said actuators including a cylinder, a piston slidably received in said cylinder, and a rod projecting from said piston through one end of said cylinder, said one end of said cylinder defining the rod end of said cylinder and the other end of said cylinder defining the head end of said cylinder such that flow of fluid to the head end of each cylinder causes extension thereof and flow of fluid to the rod end of each cylinder causes retraction thereof, a fluid power source for supplying fluid to and from the cylinders, and including a control system comprising:

• at least one pair of lines for conducting fluid to and from the cylinders, one of said lines connected to the head end of one of said cylinders and the other of said lines connected to the rod end of the other of said cylinders;
• a pressure reducing metering valve located in and controlling one line, said pressure reducing metering valve being operable to limit pressure through said one line to said head end of said one cylinder to a predetermined maximum pressure and to permit flow from said head end of said one cylinder through said pressure reducing metering valve upon obtaining a predetermined minimum pressure in said one line, and a metering valve operable to permit flow of fluid from said rod end of said other cylinder through said other line during said swinging movement of said swing bracket only when a predetermined minimum pressure exists in one of said lines;
• an interconnecting line between said one and said other lines and a check valve in said interconnecting line preventing flow from the rod end of said other cylinder to the head end of said one cylinder, while permitting flow from said hydraulic power source and the head end of said one cylinder to said rod end of said other cylinder through said other line.