Equipment Specs

Power Take-off

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Mechanical Features and Designs

Power take-off (PTO) is a feature often found on tractors and other construction and agricultural vehicles. It involves the transference of power from tractor to an implement or attachment. PTOs consist of a shaft that can be easily connected and disconnected. The PTO has a high number of hazards associated with it in the industry.


[edit] How it Works

PTOs transfer the mechanical power from the primary instrument, such as a tractor, to an implement or attachment. The power take-off can accomplish 540 revolutions per minute and consists of joints that connect the tractor to the attachment. There are many types of PTO on a farm tractor, but the most basic include the transmission, the live PTO, and the independent PTO.

[edit] Transmission

See also:  Transmission PTO

The transmission was one of the first forms to appear. It involves connecting the PTO shaft directly to the transmission of the equipment, whether it is a tractor or other piece of equipment. The main disadvantage to this type is that it ceases to operate if the tractor is not in gear or is slowing down, and only works when the clutch is released. This is said to cause problems for such applications as mowing. Furthermore, an overrunning clutch is sometimes required for this type of PTO to prevent the implemented equipment, such as a mower blade, from putting additional force on the PTO and the transmission. The overrunning clutch achieves this by allowing the shaft to spin in one direction. This feature may soon become obsolete as it is less frequently being incorporated into newer models of tractors.

[edit] Live

The live PTO operates in two stages with a clutch. By pressing the clutch halfway, the operator can cease the transmission. Pressing it all the way will cease both the transmission and the PTO. This is a beneficial feature as it allows the operator to change gears while continuing to operate the PTO.

[edit] Independent

The independent PTO consists of a separate clutch altogether for the PTO and the transmission. They can either be mechanical or hydraulic. The mechanical independent PTO can be changed with a simple on-and-off selector. The hydraulic PTO comprises a single selector.[1]

[edit] Attaching the PTO Shaft

When attaching the PTO shaft, the drawbar of the tractor should be adjusted specifically to match the implement being attached. If this is not done correctly, the driveline may separate or become compressed when the tractor makes a tight turn, damaging the protective master shield. The result may cause the shaft to spin wildly and either cause damage to the PTO or slip off and strike an operator.[2]

[edit] Safety Hazard

The PTO is one of the oldest and most common hazards associated with farm equipment. The National Safety Council has stated that as many as six percent of fatalities that occurred in 1997 were a result of the attaching or dismantling a PTO.[3]

Injuries such as amputations, lacerations, and fractures occur often occur with the PTO due to the frequent hazard of getting clothing caught in the shaft. The risk of this occurring is high and safety measures should be taken to ensure that the risk is reduced. Certain elements of the PTO are more dangerous than others. These include the PTO stub, which catches clothing and has a strong pull; the PTO driveline, which is the implement input driveline of the shaft. When the implement input shaft is connected to the tractor PTO stub, it can easily wrap around clothing and produce a pulling motion which is rapid enough to pull the operator’s arm forward and causing severe injuries.

Injuries can also occur when the PTO is connected to the implement input driveline (IID) shaft and it begins to swing in quick motions. The IID shaft can break free and sling one of its component parts, striking anyone standing nearby.[4]

To ensure that safety is observed and practiced, the master shield should always be firmly in place. The operator should take care to shield the PTO when changing an implement or removing it.[5]

Other safety tips include never crossing the driveline of a PTO that is rotating, avoiding tight turns, and wearing the appropriate clothing, namely boots without laces and snug clothing, as they are less likely to get caught in the PTO.[6]

[edit] References

  1. PTO. Tractordata. 2008-09-29.
  2. Power Takeoff. Farm Safety. 2008-09-29.
  3. PTO. Clemson. 2008-09-29.
  4. Power Takeoff. Farm Safety. 2008-09-29.
  5. PTO. Clemson. 2008-09-20.
  6. Powretakeoff. Farm Safety. 2008-09-29.