Forestry machine with hydraulic system and method for rotor braking
Embodiments relate to braking high-speed rotational cutting equipment. In particular, some embodiments relate to forestry machinery having a cutting or mower apparatus, and further having a hydraulic brake. The brake includes a counterbalance valve which pressurizes fluid at the motor outlet to a predetermined level when flow of hydraulic fluid from a pump to a motor is discontinued. The hydraulic brake may include a restrictor orifice to reduce sudden pressure increases on the motor. The predetermined pressure level may be between about 2000 psi and about 4000 psi and the orifice may have a diameter of between about 0.025 and 0.040 inches. The counterbalance vent port can hydraulically connect to the motor case line. An anti-cavitation valve can be at the counterbalance valve port and can supply fluid to the motor inlet after the flow from the pump discontinues. Additional embodiments include related hydraulic control systems and methods.
1. A hydraulic rotary forestry machine, comprising
a forestry vehicle including a hydraulic pump and hydraulic controls;
a cutting apparatus hydraulically operated via hydraulic fluid from the hydraulic pump of the vehicle and including:
a hydraulic motor operable to drive a rotor in a first direction and including a motor inlet and motor outlet;
a cutting tool mounted on the rotor;
a fluid circuit comprising at least one fluid supply line operable to supply hydraulic fluid to the hydraulic motor, and at least one fluid return line operable to return fluid from the hydraulic motor to a tank; and
a hydraulic brake comprising:
a counterbalance valve arranged in the fluid return line, wherein the counterbalance valve is operable to pressurize fluid at the motor outlet to a predetermined pressure level of between about 2000 psi and about 4000 psi when a flow of hydraulic fluid from the pump to the motor is discontinued, and wherein the counterbalance valve includes a pilot port hydraulically connected to the motor inlet, a valve port hydraulically connected to the tank and configured for supply of hydraulic fluid to the tank during operation of the motor, and a load port hydraulically connected to the motor outlet; and
at least one valve hydraulically connected to the valve port and operable to direct the flow of fluid from the fluid return line to the at least one fluid supply line when the supply of hydraulic fluid from the pump to the motor is discontinued;
wherein the hydraulic controls are operable to selectively supply hydraulic fluid to the at least one fluid supply line from the pump.
2. The machine as recited in claim 1 , wherein the hydraulic brake resides in a metal manifold block detachable from the motor, and the counterbalance valve further includes a vent port routed to the tank via the motor casing.
3. The machine as recited in claim 1 , wherein the hydraulic brake includes a restrictor orifice arranged between the motor inlet and the motor outlet and operable to reduce sudden pressure increases on the motor when a supply of hydraulic fluid from the pump to the motor is discontinued.
4. The machine as recited in claim 3 , wherein the orifice has a maximum cross-sectional dimension of between about 0.025 and about 0.04 inches.
5. The machine as recited in claim 1 , further comprising:
a pressure relief valve configured to relieve pressure at the motor inlet when the cutting tool engages an obstruction to create high pressure at the motor.
6. The machine as recited in claim 1 , further comprising:
at least one valve positioned between the fluid return line and the motor casing and operable to provide a cooling supply of fluid to a casing of the motor.