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| Illustration 1 | g00470901 |
This machine is equipped with an independent 1000 rpm power take-off (PTO). The PTO is driven by the engine. The shaft turns in the clockwise direction when the shaft is viewed from the rear of the machine.
The PTO is activated by an electrohydraulic system which provides smooth engagement. The smooth engagement reduces shock to the driveline of the implement and the machine.
The PTO is constructed with large bearings that are intended to handle high torque from the following implements: hay balers, forage harvesters and pull type combines. The PTO operates at 1000 rpm when the engine rpm speed is at 1900 rpm. The PTO shaft has a 20 tooth spline. Also, the PTO shaft has a diameter of 44.5 mm (1.75 inch).
The power that is needed to turn the PTO originates at the engine. When the engine is running, the flywheel torque limiter turns the transmission shaft at engine speed.
The input shaft for the PTO is splined to the transmission shaft through the hydraulic pump drive gear. The rear of the shaft is splined to the input hub for the PTO.
When the engine is running, the input hub rotates at engine speed. When the PTO is not engaged, power is not transferred to the PTO shaft because the PTO clutch is not engaged.
The brake band prevents the input hub and the output shaft from turning, when the PTO is not activated. When the PTO clutch is activated, the internal spline and the external spline of the clutch discs are hydraulically compressed.
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| Illustration 2 | g00470902 |
The input hub (1) turns gear (2) which turns gear (3). Gear (3) turns output shaft (4). The PTO output shaft rotates at 1000 rpm when engine speed is set at 1900 rpm.
Note: The brake band is not designed in order to stop high internal loads. The brake band provides 68 N·m (50 lb ft) of braking torque to the PTO output shaft while the engine is running and the PTO clutch is disengaged. Also, the brake band provides 11 N·m (8 lb ft) of drag at the PTO shaft when the engine is not running. This allows full 360 degrees of shaft rotation in order to hook up the PTO implements.
Major PTO Components
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| Illustration 3 | g00575018 |
The PTO valve (5) and clutch housing (12) are fastened to retainer (6). The retainer is fastened to the upper rear portion of the center housing. All three components are removed as a unit.
The retainer contains the inlet port for the lubrication oil. This inlet port is not shown in Illustration 3. The retainer also contains the inlet port for supply oil (7). Pressure tap (8) is for checking the pressure of the spool that is used for brake engagement. Pressure tap (9) is used for checking the pressure of the engagement of the PTO clutch. Other components that are shown are solenoid (10) and brake band assembly (11) that is around the clutch housing.
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| Illustration 4 | g00472394 |
The PTO clutch includes a single end plate (17) and seven separator plates (18). Separator plates (18) are splined to clutch housing (12). The seven friction discs (16) are splined to input hub (1). The PTO clutch also includes the following items: piston (14), spring seat (15) and thrust washer (13).
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| Illustration 5 | g00472398 |
The PTO valve includes valve body (20) which bolts to retainer (6). Passages on the right front of the valve route the supply oil to the valve spool and from valve spool (21). Valve spool (21) has an internal orifice. The components on the left make up accumulator (19). Accumulator (19) provides slow engagement of the PTO clutch. Orifice (23) and plug (22) control the rate of clutch engagement. The components on the bottom make up the brake piston. The brake piston engages brake band (11).
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| Illustration 6 | g00640774 |
The brake band assembly consists of piston (26) which is hydraulically forced out of the valve body and against arm (25). Brake band (24) is secured to the top of arm (25). When arm (25) is extended at the bottom, the brake band is drawn tightly around the clutch housing.
Display for the Power Take-Off
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| Illustration 7 | g00470904 |
The Electronic Monitoring Center can display the PTO speed in two areas.
The PTO speed can be displayed by pressing symbol (27) on the Machine Performance Monitor (28) .
The PTO speed can also be displayed on Central Display (29). Press the "SETUP/SELECT" switch (30) until the display for the PTO appears. The word "1000 PTO" will be displayed. Press the "SETUP/SELECT" switch (30) in order to cycle through the remaining displays. The bottom display of Central Display indicates the following information:
- Accumulated engine hours (actual time)
- Machine ground speed (MPH or km/h)
- PTO speed (rpm)
- Service indicator
The displays allow the operator to choose between the multiple displays that are offered by both the Machine Performance Monitor and the Central Display.
PTO Hydraulic System
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| Illustration 8 | g00470954 |
Low pressure hydraulic system (1) Brakes (2) PTO clutch (3) PTO valve (4) Brake valve (5) Solenoid for PTO (6) Transmission oil filter (7) Filter bypass valve (8) Passage to the charge circuits for implement and steering (9) Tandem charge pump (10) Common sump (11) Oil suction screen (12) Regulator valve (13) Steering pump (14) Pump drive housing (15) Implement hydraulic pump (16) Transmission cooler (17) Cooler bypass valve (18) Lube relief valve (19) Creeper valve (20) Pressure regulating valve (21) Passage to transmission solenoids (22) Passage to clutch lube (23) Transmission hydraulic control (24) Orifice (25) Passage for lube oil to PTO (CC) Second pressure reduction (EE) Pilot oil (FF) Reduced pilot oil (KK) Sump oil | |
The hydraulic system for the PTO is a low pressure circuit. Oil is drawn out of common sump (10) and through oil suction screen (11) to the intake of tandem charge pump (9). Oil then passes through the small section of the tandem charge pump. Oil from the tandem charge pump is then routed through transmission oil filter (6). The filtered oil either flows to oil cooler (16) or the filtered oil flows across cooler bypass valve (17). Next, the oil flows to transmission hydraulic control (23) that is located on the center housing of the transmission. Pressure regulating valve (20) is located in the transmission hydraulic control. Pressure regulating valve (20) maintains a constant pressure of 1825 ± 70 kPa (265 ± 10 psi) in the following low pressure circuits: transmission circuit for clutch operation, service brake circuit and circuit for clutch solenoids. The remaining flow that is not required by the above circuits is directed into the following circuits: PTO, lube oil for the PTO and transmission lube.
Lube oil flow for the PTO clutch is 10 L/min (2.6 US gpm) at a pressure of 206 kPa (30 psi). The lube oil flow is maintained by a 3 mm (0.125 inch) orifice that is located in the transmission hydraulic control. The excess oil flow that is not required by the PTO is directed to the transmission oil cooler. The oil that has been routed through the transmission oil cooler is then routed as lube oil for the clutches in the transmission. The transmission oil cooler is located in front of the engine radiator. The lube oil may be checked by placing a fitting at the inlet port on the left side of the retainer plate for the PTO.
PTO Valve and Clutch Operation
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| Illustration 9 | g00470955 |
Hydraulic circuit for a disengaged PTO (1) Solenoid (2) Inlet for supply oil (3) Pilot pressure (4) Retainer (5) Orifice (6) Valve spool (7) Brake band (8) Passage for lube oil (9) Clutch pack (10) Input shaft (11) Input hub (12) Clutch housing (13) Lever (14) Brake band (15) Brake piston (CC) Second pressure reduction (EE) Pilot oil (FF) Reduced pilot oil | |
The oil in the hydraulic circuit for the PTO separates in two directions at a tee. One passage of oil flows to solenoid (1) that is mounted externally on retainer plate (4). The solenoid that is normally open allows the oil to flow through the retainer plate and into the internally mounted PTO valve. The oil enters the PTO valve and the oil pushes spool (6) to the right. Also, oil flows from the other side of the tee to the other side of the valve spool. This forces the valve spool back to the left. The opposing pressures with orifices (5) hold the valve spool in a fixed position. The passages that actuate the clutch piston are closed.
An internally drilled passage in the valve spool allows oil to flow through a passage to actuate brake piston (15). The increase in oil pressure pushes the piston forward. The piston pushes on a lever (13) that is connected to brake band (14). This will tighten the band.
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| Illustration 10 | g00470960 |
Hydraulic circuit for the PTO at initial engagement (1) Solenoid (4) Retainer (5) Orifice (6) Valve spool (9) Clutch pack (11) Input hub (12) Clutch housing (13) Lever (14) Brake band (15) Brake piston (16) Solenoid spool (17) Clutch piston (18) Accumulator spool (FF) Reduced pilot oil (GG) Lube oil (LL) Sump oil | |
This diagram shows the PTO valve and the PTO clutch at the initial engagement. The PTO control is in the ON position. Supply oil from the pressure regulating valve which is in the transmission hydraulic control enters retainer (4). Solenoid (1) is now energized. Solenoid spool (16) shifts to the right. This blocks the oil flow to the right end of valve spool (6) .
Supply oil flows through solenoid spool (16) to the chamber at the left end of the valve spool (6). Oil pressure in the chamber shifts the spool to the right. Pressure oil that is behind brake piston (15) drains across valve spool (6). Supply oil flows through valve spool (6) to the cavities behind accumulator spool (18) and clutch piston (17) .
The cavity below accumulator spool (18) has a bleed hole to the spring cavity for the accumulator. Part of the supply oil is able to go through the orifice that is in the passage to the sump. The size of the orifice regulates the speed of the increase in pressure that is behind accumulator spool (18) and clutch piston (17).
When the pressure increases, accumulator spool (18) moves to the left and clutch piston (17) begins to compress clutch pack (9). As clutch pack (9) is compressed, clutch housing (12) begins to rotate. This will drive the gears which cause the PTO output shaft to rotate. The smooth engagement reduces shock to the driveline of the implement and the machine.
When the PTO is disengaged, oil pressure behind accumulator spool (21) allows clutch piston (17) to slowly disengage. The rotation of the drive shaft is not abruptly stopped by the brake band.
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| Illustration 11 | g00470962 |
Hydraulic circuit for an engaged PTO (1) Solenoid (2) Inlet for supply oil (4) Retainer (6) Valve spool (8) Passage for lube oil (9) Clutch pack (10) Input shaft (11) Input hub (12) Clutch housing (18) Accumulator spool (19) Sleeve (20) Clutch engagement pressure test port (21) Clutch piston (CC) Second pressure reduction (EE) Pilot oil (KK) Sump oil | |
When the PTO is engaged, solenoid (1) closes. The oil flow to the left side of valve spool (6) is blocked. Oil from the tee enters the right side of the PTO valve. This forces valve spool (6) to the left. When the valve spool shifts to the left, the oil that is flowing through the internal passage in valve spool (6) releases the brake band on the clutch housing.
When valve spool (6) is shifted to the left side, the oil that is flowing through the internal passage in valve spool (6) is routed to both the chamber behind accumulator spool (18) and the chamber for clutch piston (21).
The oil from the left side of accumulator spool (18) flows to the sump through a hole in the retaining washer for the spring. The bleed orifices and the spring force provide the gradual shift of the spool. This prevents an instantaneous lockup of the PTO clutch.
When oil pressure that is in the chamber increases, the valve spool (6) gradually shifts to the right. This blocks the oil flow that goes through the orifices into the chamber. When the oil flow in the orifices is blocked, the pressure builds up in the chamber in order to completely compress the clutch piston. This locks up the friction discs and plates for a complete engagement of the PTO.
The modulated engagement of the PTO is 2.5 to 3.0 seconds. The oil pressure for the engagement of the PTO clutch is 690 kPa (100 psi) for the first 1.5 seconds. This changes to 1650 kPa (240 psi) to 1800 kPa (260 psi).