Power take-off: Difference between revisions
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[[Image:TractorPTOshaftMay04.jpg|right|thumb|A shaft attached to the PTO.]] |
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A '''power take-off''' (PTO) is a [[spline (device)|spline]]d [[driveshaft]], usually on a [[tractor]] or [[truck]] that can be used to provide power to an attachment or separate machine. It is designed to be easily connected and disconnected. The power take-off allows implements to draw energy from the tractor's engine. |
A '''power take-off''' (PTO) is a [[spline (device)|spline]]d [[driveshaft]], usually on a [[tractor]] or [[truck]] that can be used to provide power to an attachment or separate machine. It is designed to be easily connected and disconnected. The power take-off allows implements to draw energy from the tractor's engine. |
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==Safety== |
==Safety== |
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[[Image:TractorPTOshaftMay04.jpg|right|thumb|180 px|A shaft attached to the PTO.]] |
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The PTO and its associated shafts and [[universal joint]]s are a common cause of [[accident]]s and [[injury]] in [[farming]] and industry. The according to the [[National Safety Council]], 6 percent of tractor related fatalities in [[1997]] in the [[USA]] involved the PTO. When a piece of clothing, which can be as small as a single thread, touches a spinning part it can be pulled around the part. The clothing and the person wearing it are pulled into the shaft often resulting in loss of limb or death. Some implements do use plastic guards to try to keep a person from becoming entangled in a PTO shaft, but even with guards people need to exercise caution around PTO shafts when they are plugged into a tractor. In some countries it is illegal to operate a PTO without the shaft guard correctly fastened. <ref> |
The PTO and its associated shafts and [[universal joint]]s are a common cause of [[accident]]s and [[injury]] in [[farming]] and industry. The according to the [[National Safety Council]], 6 percent of tractor related fatalities in [[1997]] in the [[USA]] involved the PTO. When a piece of clothing, which can be as small as a single thread, touches a spinning part it can be pulled around the part. The clothing and the person wearing it are pulled into the shaft often resulting in loss of limb or death. Some implements do use plastic guards to try to keep a person from becoming entangled in a PTO shaft, but even with guards people need to exercise caution around PTO shafts when they are plugged into a tractor. In some countries it is illegal to operate a PTO without the shaft guard correctly fastened. <ref> |
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==Technical Standardization== |
==Technical Standardization== |
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[[Image:TractorPTOplugInMay04.jpg|thumb|left|A tractor PTO]] |
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Agricultural PTOs are [[Standardization|standardized]] in dimensions and speed. The original specification calls for operation at 540 [[revolutions per minute]] (RPM). A shaft that rotates at 540 rpm has 6 splines on it, and a diameter of 1⅜". Two newer specifications, supporting higher power applications, operate at 1000 RPM and differ in shaft size. The larger shaft has 20 splines (1¾" diameter), while the smaller has 21 (1⅜" diameter). All three types rotate counterclockwise when viewed from the tractor. It is customary for agricultural machines manufacturers to provide the nominal PTO [[power]] specification, an indication of the available instantaneous power at the shaft. |
Agricultural PTOs are [[Standardization|standardized]] in dimensions and speed. The original specification calls for operation at 540 [[revolutions per minute]] (RPM). A shaft that rotates at 540 rpm has 6 splines on it, and a diameter of 1⅜". Two newer specifications, supporting higher power applications, operate at 1000 RPM and differ in shaft size. The larger shaft has 20 splines (1¾" diameter), while the smaller has 21 (1⅜" diameter). All three types rotate counterclockwise when viewed from the tractor. It is customary for agricultural machines manufacturers to provide the nominal PTO [[power]] specification, an indication of the available instantaneous power at the shaft. |
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Revision as of 11:49, 19 April 2007
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A power take-off (PTO) is a splined driveshaft, usually on a tractor or truck that can be used to provide power to an attachment or separate machine. It is designed to be easily connected and disconnected. The power take-off allows implements to draw energy from the tractor's engine.
Safety
The PTO and its associated shafts and universal joints are a common cause of accidents and injury in farming and industry. The according to the National Safety Council, 6 percent of tractor related fatalities in 1997 in the USA involved the PTO. When a piece of clothing, which can be as small as a single thread, touches a spinning part it can be pulled around the part. The clothing and the person wearing it are pulled into the shaft often resulting in loss of limb or death. Some implements do use plastic guards to try to keep a person from becoming entangled in a PTO shaft, but even with guards people need to exercise caution around PTO shafts when they are plugged into a tractor. In some countries it is illegal to operate a PTO without the shaft guard correctly fastened. [1][2]
Technical Standardization
Agricultural PTOs are standardized in dimensions and speed. The original specification calls for operation at 540 revolutions per minute (RPM). A shaft that rotates at 540 rpm has 6 splines on it, and a diameter of 1⅜". Two newer specifications, supporting higher power applications, operate at 1000 RPM and differ in shaft size. The larger shaft has 20 splines (1¾" diameter), while the smaller has 21 (1⅜" diameter). All three types rotate counterclockwise when viewed from the tractor. It is customary for agricultural machines manufacturers to provide the nominal PTO power specification, an indication of the available instantaneous power at the shaft.
Configuration
The manner in which the power it transmitted to the PTO varies, which affects the operation.
In a tractor with a transmission PTO, the PTO is driven directly of the transmission, and the PTO is disengaged by the tractors clutch. This configuration is the simplest, but it has the disadvantage that if the tractor needs to be slowed, the PTO will stop. This configuration often requires an overrunning clutch which disengages the PTO if the PTO is rotating faster than the transmission. This prevents PTO driven attachments with high inertia from driving the tractor once the clutch has been disengaged on the tractor.
In a tractor with a live PTO, there is a two-stage clutch. Pressing the clutch half-way will disengage the transmission while pressing it fully will disengage the transmission and the PTO. This configuration allows the operator to slow down or change gears while the PTO is still operating.
In a tractor with an independent PTO, there is a separate clutch for the PTO. As with a live PTO, this allows for full control over the tractor while separately controlling the PTO. Independent PTO's may be controlled mechanical or hydraulic. [3]
References
- ^
Power-Take-Off (PTO) Safety, National Safety Concil, 2004-03-30, retrieved 2007-04-19
{{citation}}: Check date values in:|date=(help) - ^
Privette, Charles (2002-03-01), Farm Safety & Health - PTO Safety, Department of Agricultural and Biological Engineering, Clemson University, retrieved 2007-04-19
{{citation}}: Check date values in:|date=(help) - ^ Power Take-Off (PTO) Types, TractorData.com, retrieved 2007-04-19