Abstract: In many hydraulic systems, fluid-borne noise is generated during operation due to the effects of the hydraulic pump. This fluid-borne noise is then transmitted to the hydraulic valves, hydraulic lines, and other structure that valves and lines are mounted on. These structures then emit vibrations that create the largest portion of the system air-borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid-borne noise in a hydraulic system. The apparatus includes a mechanism for effectively sensing the flow ripple produced by the pump and a mechanism for transmitting a signal (C) representative of the flow ripple to a negative ripple generator which provides a corrective flow to the hydraulic system to cancel the flow ripple. By eliminating the flow ripple in the hydraulic system, the associated air-borne noise that is created by various components that are associated with the hydraulic system is attenuated.

Abstract: Large earthmoving vehicles require complex mechanisms for mechanically driving the auxiliary power units. The subject drive mechanism includes an elevating transfer gear train at the rear frame portion of the vehicle that drives a rear auxiliary power unit via an upper transfer gear, and that drives a front auxiliary power unit on the front frame portion of the vehicle through a relatively long drive shaft system extending from the upper transfer gear. A torsionally tuned spring coupling having a plurality of compression spring sets arranged in at least two circular arrays is incorporated between the engine and an input gear of the transfer gear train for providing two stiffness rates and effectively isolating the drive mechanism from the torsional excitation pulses of the engine and the effects of gear shifting of an associated transmission for powerably driving the vehicle.