Diesel engines have historically been loud, noisy machines. Because of this, some governments here in North America as well as in Europe are enacting laws to regulate the idling of diesel engines to keep the noise pollution under control.
The Chelsea Division of Parker has developed the 249 Series power takeoff to reduce overall noise emissions on vocational trucks.
Vocational truck PTOs essentially are mated directly to the engine via the transmission. As the crankshaft of the engine rotates, it drives the gears within the PTO to eventually spin the PTO shaft to drive a pump, compressor, or other piece of equipment.
The engine smoothness or torsional signature greatly impacts the gear train design due to the required backlash requirements of gearing. Most all components on today's trucks are affected by these sometimes severe vibrations. These torsional vibrations produce an erratic flow of power into the transmission, and subsequently the PTO. The new technologies required to address noise emissions, fuel economy, and exhaust emissions, engines and their torsional signature have steadily worsened.
The torsional signature of engines causes an acceleration and deceleration of the gear teeth in the transmission and the PTO. These accelerations and decelerations of the gear teeth can cause a gear rattle noise from the gear teeth hitting both the drive and the coast side of the gear tooth. Although the rattle is in some cases very objectionable and dissatisfying to the truck operators, it rarely causes any durability or life concerns.
Past measures to minimize noise have been controlling the gear mesh to a very high standard, selectively fitting the PTO to the transmission with shim gaskets to reduce the gear backlash, or adding friction components to create a drag in the system to keep the gears in a tight mesh. As the torsional vibrations of newer engines increase and the sound emission of these engines are reduced, past measures for keeping a PTO quiet are no longer adequate.
Chelsea's new design incorporates a patent-pending way to reduce spacing of the meshing gears to zero. A biasing force tightens the mesh of the gears, but not so much as to bind them together. With the gears in a near-zero mesh spacing, there is essentially no ability for the gears to chatter or rattle.
Visit www.parker.com/chelsea for more details.