Abstract:
A tensioner comprising a cantilever spring having a first arm ( 13 ) and a second arm ( 14 ), the first arm and the second arm describing an included angle (α), a pulley ( 30 ) journalled to the first arm, a mounting portion ( 11 ), and a resilient damping member ( 20 ) disposed between the first arm and the second arm for damping an arm vibration.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a tensioner, and more particularly to a tensioner comprising a cantilever spring and a resilient damping member engaged with the cantilever spring. 
       BACKGROUND OF THE INVENTION 
       [0002]    The main purpose of a belt tensioner is to prolong the life of an engine or accessory drive belt. The most typical use for such automatic belt tensioners is on front-end accessory drives in an automobile engine. This drive includes pulley sheaves for each accessory the belt is required to power, such as the air conditioner, water pump, fan and alternator. Each of these accessories requires varying amounts of power at various times during operation. These power variations create a slackening and tightening situation of each span of the belt. The belt tensioner is utilized to absorb these power variations. 
         [0003]    Representative of the art is U.S. Pat. No. 6,224,028 to Tanaka which discloses a cantilever shaft assembly includes a steel pipe firmly secured at one end to a wall surface of a stationary support member, and a core shaft made from a synthetic resin and having a body portion removably fitted in the steel pipe and an end portion located outside the steel pipe. The end portion forms a free end of the cantilever shaft assembly and rotatably supports thereon a rotating member such as a driven sprocket. The core shaft and the steel pipe are locked and held together by a locking device such as a pin or a key. The cantilever shaft assembly is light in weight and can be easily repaired at a low cost when the end portion of the synthetic resin core shaft is damaged or worn out. 
         [0004]    What is needed is a tensioner having a cantilever spring and a resilient damping member engaged with the cantilever spring. The present invention meets this need. 
       SUMMARY OF THE INVENTION 
       [0005]    The primary aspect of the invention is to provide a tensioner having a cantilever spring and a resilient damping member engaged with the cantilever spring. 
         [0006]    Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings. 
         [0007]    The invention comprises a tensioner comprising a cantilever spring having a first arm ( 13 ) and a second arm ( 14 ), the first arm and the second arm describing an included angle (α), a pulley ( 30 ) journalled to the first arm, a mounting portion ( 11 ), and a resilient damping member ( 20 ) disposed between the first arm and the second arm for damping an arm vibration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention. 
           [0009]      FIG. 1  is a perspective view of the tensioner. 
           [0010]      FIG. 2  is a perspective view of an alternate embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0011]      FIG. 1  is a perspective view of the tensioner. Tensioner  100  comprises a cantilever spring  10 . Cantilever spring  10  has a mounting portion  11  disposed at one end for attaching the tensioner to a mounting surface, such as a vehicle engine (not shown). Mounting portion  11  may receive known fasteners such as bolts, screws or studs through holes  15 . 
         [0012]    Cantilever spring  10  is typically made from a flat metal strip bent in the form of a “V” as shown, or a “W” or other desired shapes. In the “V” configuration cantilever spring  10  comprises an elbow or bend  12 . Bend  12  is disposed between arm  13  and arm  14 . Arm  13  and arm  14  describe an included angle (α). Cantilever spring  10  may comprise any resilient material having a spring rate, including for example, metal or plastic. 
         [0013]    A resilient damping member  20  is disposed in bend  12  between arm  13  and arm  14 . Damping member  20  comprises known natural rubber or synthetic rubber or a combination of the two. For example, HNBR, EPDM, natural rubber, neoprene, VAMAC and SBR may be used with equal success. Damping member  20  may be sized to occupy all or a portion of the space bounded by arm  13  and arm  14 . Damping member  20  is typically sized to properly damp vibrations while not unduly affecting the spring rate of cantilever spring  10 . 
         [0014]    Damping member  20  is adhered to the surface of arm  13  and arm  14  using suitable adhesives known in the art. Damping member  20  may be molded separately and then applied to the cantilever spring, or, it can be “molded in place” in bend  12  upon the cantilever spring in its described location. The damping member may also be attached by mechanical means such as fasteners or adhesives. 
         [0015]    Pulley  30  is journalled to axle  40  at an end  16  of cantilever spring  10 . Axle  40  is connected to arm  13 . Pulley  30  rotates upon a bearing  31 , which bearing  31  is connected to axle  40 . Pulley  30  comprises a belt engaging surface  32  for engaging a multi-ribbed belt (not shown). Surface  32  may also be toothed, flat or v-shaped. 
         [0016]    The inventive tensioner is used to apply a load to a belt in a belt drive system. The belt load is realized through compression of the cantilever spring. The magnitude of the applied belt load is a function of the spring rate of the cantilever spring. By way of example, the spring rate of cantilever spring  10  is in the range of approximately 0.25 Nm/degree up to 50 Nm/degree. 
         [0017]    During operation of a belt drive system the belt will normally vibrate. The vibrations can be transmitted through the system unless they are damped. Damping member  20  damps vibrations transmitted from the belt to arm  13  and arm  14 . In particular, damping member  20  damps relative movements between arm  13  and arm  14 , and as may be characterized as periodic changes in angle (α). 
         [0018]      FIG. 2  is a perspective view of an alternate embodiment. The alternate embodiment is the same as the embodiment described in  FIG. 1  with the exception that instead of a single bend  12 , this embodiment comprises more than one bend with bends  12   a  and  12   b . Contained in each bend  12 ,  12   a ,  12   b  is a damping member  20 ,  20   a ,  20   b . Arm  140  is connected to bend  12   a  and  12   b . Arm  130  is connected to bend  12   b . Pulley  30  is attached to arm  130 . As is the case for the embodiment in  FIG. 1 , the spring rate of cantilever spring  10  is in the range of approximately 0.25 Nm/degree up to 50 Nm/degree. 
         [0019]    Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts and method without departing from the spirit and scope of the invention described herein.