Title: Backhoe swing cylinder hydraulic circuit

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Abstract: As the backhoe boom 19 swings into a swing stop, hydraulic fluid is trapped in the head end 28 of the swing side cylinder 24. This trapped fluid is discharged through a cylinder relief valve, thus absorbing the boom kinetic energy and providing a smooth deceleration of the boom. Fluid discharged from the relief valve 47 is routed to the rod end of the swing cylinder and the head end of the opposite cylinder. Because of the swing linkage geometry, the cylinder rod 30 of the other cylinder had passed over the pivot axis about which the backhoe boom was swinging and thus the piston 29 of the other cylinder was caused to move in the same direction as the swing side piston 29. The movement of this piston can be utilized to provide additional deceleration torque as long as no voiding is permitted to occur in the head end of this other cylinder. Voiding only occurs when the backhoe swing control lever 38 is released prior to the backhoe boom reaching the swing stop. Voiding does not occur when the control lever 38 is maintained in a full power-on or is stroked in the power-on mode until the swing stop is contacted. Fluid from the swing side cylinder relief valve is routed to provide the necessary fluid to prevent such voiding. The routing of the fluid from the swing cylinder to the other cylinder assures that the boom deceleration is independent of whether the control lever is stroked or released.


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