Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Guide roll mounted for movement of its axis along arcuate...
Reexamination Certificate
2001-10-22
2003-07-15
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Guide roll mounted for movement of its axis along arcuate...
C192S048920, C192S048300, C192S045000
Reexamination Certificate
active
06592482
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to tensioners, more particularly to tensioners having asymmetric damping achieved by use of a one-way clutch coupled with a friction clutch.
BACKGROUND OF THE INVENTION
Most engines used for automobiles and the like include a number of belt driven accessory systems which are necessary for the proper operation of the vehicle. The accessory systems may include an alternator, air conditioner compressor and a power steering pump.
The accessory systems are generally mounted on a front surface of the engine. Each accessory would have a pulley mounted on a shaft for receiving power from some form of belt drive. In early systems, each accessory was driven by a separate belt that ran between the accessory and the crankshaft. With improvements in belt technology, single serpentine belts are -now used in most applications. Accessories are driven by a single serpentine belt routed among the various accessory components. The serpentine belt is driven by the engine crankshaft.
Since the serpentine belt must be routed to all accessories, it has generally become longer than its predecessors. To operate properly, the belt is installed with a pre-determined tension. As it operates, it stretches slightly. This results in a decrease in belt tension, which may cause the belt to slip. Consequently, a belt tensioner is used to maintain the proper belt tension as the belt stretches during use.
As a belt tensioner operates, the running belt may excite oscillations in the tensioner spring. These oscillations are undesirable, as they cause premature wear of the belt and tensioner. Therefore, a damping mechanism is added to the tensioner to damp the oscillations.
Various damping mechanisms have been developed. They include viscous fluid based dampers, mechanisms based on frictional surfaces sliding or interaction with each other, and dampers having interacting springs. The art also comprises lock center devices that allow a pivot arm to move only in a single direction.
Representative of the art is JP07113446A to Bando which discloses a tensioner having a one-way clutch on an immoveable portion which regulates a movement of a moveable portion.
Also representative of the art is U.S. Pat. No. 4,583,962 (1986) to Bytzek et al. which discloses a tensioning device having a damping system for damping the operating movements by a one-way clutch mechanism.
What is needed is a tensioner having asymmetric damping using a one-way clutch coupled with a friction clutch. What is needed is a tensioner having a one-way clutch coupled with a friction clutch having radially extending surfaces. The present invention meets these needs.
SUMMARY OF THE INVENTION
The primary aspect of the invention is to provide a tensioner having asymmetric damping using a one-way clutch coupled with a friction clutch.
Another aspect of the invention is to provide a tensioner having a one-way clutch coupled with a friction clutch having radially extending surfaces.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a belt tensioner having a pivot arm biased toward a belt by a torsion spring. The tensioner also comprises a one-way clutch coupled with a friction clutch. The pivot arm of the tensioner is connected to a one-way clutch. The one-way clutch is cooperatively connected to a friction clutch having a predetermined friction torque caused by frictionally engaged radially extending surfaces. The pivot arm may move relatively freely toward a belt by operation of the one-way clutch. At the limit of arm movement the one-way clutch engages, preventing travel away from the belt in an opposite direction. The arm may only travel away from the belt when a belt tension torque exceeds the spring force plus a friction torque of the friction clutch.
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Austin, Esq. S. G.
Castleman, Esq. C. H.
Hannon Thomas R.
The Gates Corporation
Thurnau, Esq. J. A.
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