The winch assembly consists of six basic component groups:
- 1. Winch case
- 2. Hydraulic motor and piping
- 3. Brake housing assembly
- 4. Cable drum
- 5. Planetary reduction group
- 6. Carrier clutch group
- 2. Hydraulic motor and piping
The winch case is a structural member of welded construction designed specifically for use in tractor winch applications. The case supports the output ring gear and the brake housing assembly. The cable drum rotates on two large tapered roller bearings. The hydraulic motor is bolted to the brake housing, which also supports the right hand cable drum bearings. The output ring gear supports the left hand cable drum bearings.
The planetary reduction group contains three planetary gear sets driven by the primary sun gear shaft, which is coupled to the motor shaft by the inner race of the overrunning brake clutch assembly. With a total reduction of 212:1 or 255:1, the planetary reduction group greatly multiplies the motor torque for high line pulls at maximum efficiency and precise load control.
The CARCO H90VS winch contains a hydraulic motor and gear ratio specifically selected to match the winch to the hydraulic power of the specific tractor. This allows the winch to maximize the available hydraulic horsepower.
The winch motor is operated utilizing the full flow of the tractor implement pump via the implement valve, which also controls both the blade and ripper. The ripper section of the implement valve may be used to operate the winch, or in some instances, it may be replaced with a special winch valve to enhance the winch performance capabilities. In any case, the valve used will be a four way, three position valve.
Typically, the winch control valve is connected to the operator's joystick control lever by a series hydraulic hoses. Movement of the control lever directs the oil flow to the winch motor through hydraulic lines. The hydraulic motor converts the flow and pressure of the hydraulic system into the mechanical energy needed to drive the winch gear train.
The tractor can walk away from a winch load to reposition for another pull by releasing the drum clutch. The spring applied, hydraulically released multi-disc clutch locks the clutch carrier to the secondary sun gear through the gear adapter. When released, clearance between the clutch plates allows the secondary sun gear to rotate free of the clutch carrier, so the winch drum is disengaged from the winch static brake. The cable drum drag observed during brake-off (drum clutch release) is caused by the rotating output and secondary planetary gear sets and viscous drag of the friction discs. The brake-off drag force increases as the tractor ground speed increases.
The dual brake system consists of a dynamic brake system and a static brake system. The dynamic brake system has two operating components:
- 1. Hydraulic Brake valve assembly
- 2. Hydraulic motor
The brake valve is similar to a counter-balance valve. It contains a check valve to allow free flow of oil to the motor in the Reel-In direction and a pilot-operated, spring-load spool valve which blocks the flow of oil out of the motor when the control valve is placed in neutral. When the control valve is moved into the Reel-Out position, the spool in the brake valve remains closed until sufficient pilot pressure is applied to the end of the spool to shift it against the spring pressure and open a passage. After the spool valve cracks open, the pilot pressure becomes flow dependentand modulates the spool valve opening which controls the Reel-Out speed.
The static brake system has three operating components:
- 1. Spring applied, multiple friction disc static brake
- 2. Sprag-type overrunning brake clutch assembly
- 3. Hydraulic piston and cylinder
- 2. Sprag-type overrunning brake clutch assembly
The static brake is released by the brake valve pilot pressure at a pressure lower than that required to open the pilot operated spool valve in the brake valve assembly. This sequence assures that dynamic braking takes place in the brake valve and that little, if any, heating is absorbed by the friction discs.
The friction brake is a load holding brake only and has nothing to do with dynamic braking or the rate of release of a heavy or suspended load.
The overrunning brake clutch is splined to the primary sun gear shaft between the motor and the primary sun gear. It will allow this shaft to turn freely in the direction of Reel-In, and lock up to force the brake discs to turn with the shaft in the direction of Reel-Out.
The hydraulic cylinder, when pressurized, will release the spring pressure on the brake discs, allowing the brake discs to turn freely.
When pulling in a load (Reel-In), the overrunning brake clutch, which connects the motor shaft to the primary sun gear, allows free rotation through the gear train to the cable drum. The sprag cams lays over and permit the inner race to turn free of the outer race. The friction brake remains fully applied. The winch, while reeling in a load, is not affected by any braking action.
When the Reel-In operation is stopped, the load attempts to turn the primary sun gear in the opposite direction. This reversed input causes the sprag cams to instantly roll upward and firmly lock the shaft to the fully applied friction brake.
When the winch is powered in reverse, to Reel-Out the load, the motor can not rotate until sufficient pilot pressure is present to open the brake valve. The friction brake within the winch will completely release at a pressure lower than that required to open the brake valve, typically 350 PSI (2,413 kPa) and 600 PSI (4,137 kPa), respectively. The extent to which the brake valve opens will determine the amount of oil that can flow through it and the speed at which the load will Reel-Out. Increasing the flow of oil to the winch motor will cause the pressure to rise and the opening in the brake valve to enlarge, speeding up the release of the load. Decreasing this flow causes the pressure to lower and the opening in the brake valve to decrease, thus slowing the release of the load.
With the control valve shifted to neutral, the pressure will drop and the brake valve will close, stopping the load. The friction brake will reapply and hold the load after the brake has closed.
The friction brake receives very little wear during the Reel-Out operation. Most of the heat generated by the releasing and stopping of the load is absorbed into the hydraulic oil where it can be readily dissipated.