|Tol’s HD1400 self-propelled topper hedger uses hydraulics to power its variable-speed, four-wheel drive propulsion system, multiple hydraulic cylinders and motors to position and rotate six cutting blades, plus additional critical functions, such as steering, braking, and power to the cooling system. |
Tol Inc., Tulare, Calif, offers a complete line of self-propelled tree-topping and hedging machines. Manufactured in Israel, the machines typically are used when trees are dormant — after the previous season’s crop has been picked, but before blossoms for the new crop have appeared. Periodic pruning of trees and bushes maximizes crop yield, stimulates growth for healthy plants, shapes the trees faster, and makes harvesting easier.
The machines take full advantage of the versatility of hydraulics by using hydraulic cylinders for multi-axial boom articulation, hydraulic motors for powering saw blades, a hydrostatic drive for propulsion, and other functions, such as steering, braking, and engine cooling via a variable-speed hydraulic fan drive. The hydraulic fan drive keeps the engine running at optimum temperature for maximum fuel efficiency and minimum emissions.
A case in point is Tol’s HD-1400 self-propelled topper hedger. It relies on four hydraulic circuits to accomplish its multiple functions. It’s powered by a John Deere 6068T turbocharged diesel engine, which is capable of transmitting 140 hp at 2500 rpm. The engine drives a John Deere 590 0 0 Funk brand pump drive, which has two pump flanges. One pump station drives a hydrostatic drive system that powers a John Deere Model HMD188 Funk brand 2-speed transmission. The drive train is capable of speeds to 5 mph in its low-speed mode and 12.5 mph in its highspeed mode.
The other pump station powers a variable-speed piston pump that drives six hydraulic motors, each of which drives a 32-in. diameter saw blade. A gear pump tandem mounted to the hydrostatic pump supplies fluid to three sets of cylinders for positioning saw blades and an engine hood lift cylinder. A gear pump tandem mounted off the main pump drives the hydraulic cooling system. The cooling system maintains tight temperature control of engine oil, hydraulic oil, and engine coolant. The fan motor is also reversible, which blows out any debris that may accumulate in fins of heat exchangers.