Patent Document

REFERENCE TO RELATED APPLICATIONS  
         [0001]    This divisional application claims priority from U.S. non-provisional application Ser. No. 09/549,258.  
         FIELD OF THE INVENTION  
         [0002]    The invention relates to tensioners, more particularly to tensioners that are spring biased, wedge actuated belt tensioning devices having damping and used with belts for vehicle accessory drives.  
         BACKGROUND OF THE INVENTION  
         [0003]    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.  
           [0004]    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.  
           [0005]    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.  
           [0006]    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.  
           [0007]    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 using a series of interacting springs.  
           [0008]    Representative of the art is U.S. Pat. No. 4,402,677(1983) to Radocaj which discloses a tensioner having an L-shaped housing. A pair of cam plates having camming surfaces are slideably mounted in the L-shaped housing. A compression spring biases the camming plates into sliding engagement with each other. The included angle of the camming surfaces equal 90° with the angle of a first camming surface being greater than the angle of a second camming surface.  
           [0009]    Also representative of the art is U.S. Pat. No. 5,951,423(1999) to Simpson which discloses a mechanical friction tensioner having spring loaded wedge-shaped blocks and friction damping. The tensioner has a wedge-shaped piston that interacts with spring biased wedge-shaped blocks. As the piston moves inward the wedge-shaped blocks are pushed outward to provide friction damping.  
           [0010]    The prior art devices rely on springs or other components, each oriented on axes that are set at a pre-determined angle to each other. They also rely on a plurality of springs to properly operate the damping components and to urge the belt pulley into contact with a belt. The prior art does not teach a damping components that operate coaxially. Further, the prior art does not teach use of an expandable camming body. Nor does it teach the use of an expandable camming body that expands radially. Nor does it teach the use of an expandable camming body that expands radially in response to movement against a piston. Nor does it teach the use of an expandable camming body that expands radially in response to movement against a tapered piston.  
           [0011]    What is needed is a tensioner having a coaxial piston and camming body operating coaxially. What is needed is a tensioner having an expandable camming body. What is needed is a tensioner having an expandable camming body that is radially expandable. What is needed is a tensioner having an expandable camming body that is radially expandable in response to movement against a piston. What is needed is a tensioner having an expandable camming body that expands radially in response to movement against a tapered piston. The present invention meets these needs.  
         SUMMARY OF THE INVENTION  
         [0012]    The primary aspect of the invention is to provide a tensioner having a coaxial tapered piston and camming body.  
           [0013]    Another aspect of the invention is to provide a tensioner having an expandable camming body.  
           [0014]    Another aspect of the invention is to provide a tensioner having an expandable camming body that is radially expandable.  
           [0015]    Another aspect of the invention is to provide a tensioner having an expandable camming body that is radially expandable in response to movement against a piston.  
           [0016]    Another aspect of the invention is to provide a linear tensioner having an expandable camming body that expands radially in response to movement against a tapered piston.  
           [0017]    Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.  
           [0018]    The invention comprises a self-contained mechanical belt tensioner that produces damping which is a function of applied hubload through the effect of frictional forces derived from the sliding action of mutually opposing wedges. A conical piston is contained within a housing. The conical piston cooperates with a conical wedge or camming body. The conical wedge slides on the inner surface of the housing. The conical wedge is radially expandable in a direction normal to the housing. A spring urges the conical wedge into engagement with the conical piston. As the pulley is loaded, as with an impulse load, the piston will move into the conical wedge. This, in turn, will cause the conical wedge to radially expand against the inner surface of the housing. The expansion of the conical wedge in the housing will increase the frictional force between the conical wedge and the housing. This will have the effect of damping movements of the wedge and conical piston. The greater the impulse, then the greater the expansion of the conical wedge. Hence, this increases the resultant frictional force resisting movement between the conical wedge and the housing. As the load moves toward a minimum, the camming body radially contracts and the frictional force is abated to a low level allowing ease of retraction of the piston. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    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.  
         [0020]    [0020]FIG. 1 is a cross-sectional view of the invention.  
         [0021]    [0021]FIG. 2( a ) is a top plan view of the wedge through section  2   a - 2   a  in FIG. 3.  
         [0022]    [0022]FIG. 2( b ) is a side elevation view of the wedge through section  2   b - 2   b  in FIG. 3.  
         [0023]    [0023]FIG. 3 is a side cross-section view of the damping section of the invention:  
         [0024]    [0024]FIG. 4 is a perspective view of the wedge.  
         [0025]    [0025]FIG. 5 is a perspective view of the piston  14 .  
         [0026]    [0026]FIG. 6 is a perspective view of the housing  1 .  
         [0027]    [0027]FIG. 7( a ) is a schematic free body diagram of the damping mechanism during a compression stroke.  
         [0028]    [0028]FIG. 7( b ) is a schematic free body diagram of the damping mechanism during a return stroke.  
         [0029]    [0029]FIG. 8 is a cross-sectional view of a first alternate embodiment of the invention.  
         [0030]    [0030]FIG. 9 is a plan view of the wedge for the alternate embodiment.  
         [0031]    [0031]FIG. 10 is a cross-sectional view of the housing for the alternate embodiment:  
         [0032]    [0032]FIG. 11 is a cross-sectional view of a second alternate embodiment of the invention.  
         [0033]    [0033]FIG. 12 is a cross-sectional view of a third alternate embodiment of the invention.  
         [0034]    [0034]FIG. 13 is a cross-sectional view along axis A-A of a fourth alternate embodiment of the invention.  
         [0035]    [0035]FIG. 14 is a cross-sectional view along axis A-A of a fifth alternate embodiment of the invention.  
         [0036]    [0036]FIG. 15 is a plan view of a tensioner.  
         [0037]    [0037]FIG. 16 is a perspective exploded view of the damping mechanism for an alternate embodiment.  
         [0038]    [0038]FIG. 17 is an end plan view of the wedge for an alternate embodiment.  
         [0039]    [0039]FIG. 18 is an end plan view of the tube of an alternate embodiment.  
         [0040]    [0040]FIG. 19 is an end plan view of the wedge for an alternate embodiment.  
         [0041]    [0041]FIG. 20 is an end plan view of the tube of an alternate embodiment.  
         [0042]    [0042]FIG. 21 is an exploded view of the wedge and tube for an alternate embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0043]    [0043]FIG. 1 is a cross-sectional view of the invention. A linear tensioner is shown having a damping section that is distinct from the pivot/pulley section. Housing  1  contains the damping components for the tensioner. Housing  1  in the preferred embodiment is cylindrical. However, housing  1  may have any shape generally compatible with the operation described herein. Pivot arm  3  is pivotably connected to housing  1 . Pulley  8  is journaled to pivot arm  3 . Pulley  8  engages a belt B to be tensioned. Adjuster or adjusting screw  7  having a flange is threaded into an end of housing  1  and is used to adjust or fine tune the spring preload force and hence the damping force by turning clockwise or counterclockwise as required by a user.  
         [0044]    Compressible member or spring  6  bears on wedge  13 . Wedge or camming body  13  comprises a tapered or conical hole  15 . Wedge outer surface  16  is slidingly engaged with housing inner surface  17 . Wedge outer surface  16  may comprise a nonmetallic material, such as plastic or phenolic. Piston  14  comprises a cylindrical shape. End  19  of piston  14  has a tapered or frustoconical shape that cooperates with hole  15  in wedge  13 . End  20  of piston  14  opposite the conical end cooperates with bearing point  18 . Bearing point  18  allows pivot arm  3  to press upon the end  20  of piston  14  without undue binding.  
         [0045]    [0045]FIG. 2( a ) is a top plan view of the wedge through section  2   a - 2   a  in FIG. 3. Wedge or camming body  13  comprises slots  40 ,  41 . Slots  40  project from an outer surface of the wedge toward the hole  15 . Slots  41  project from hole  15  toward an outer surface of the wedge. Slots  40 ,  41  allow wedge  13  to radially expand and contract, shown as bi-directional arrow E, as the tensioner operates according to the following descriptions. One should note that although the surface  16  is shown as smooth and of circular shape in this FIG. 2 a , surface  16  may have other shapes or profiles as described in the other figures described in this specification.  
         [0046]    [0046]FIG. 2( b ) is a side elevation view of the wedge through section  2   b - 2   b  in FIG. 3. Slots  40  extend from a first surface  44  of the wedge and slots  41  extend from an opposing surface  45  of the wedge as compared to the first surface. Slots  40 ,  41  further comprise holes  42 ,  43  respectively, which allow the wedge sides to expand and contract without causing cracking or failure of the wedge at each slot end.  
         [0047]    [0047]FIG. 3 is a side cross-section view of the damping section of the invention as described in FIG. 1. Movement of the pivot arm  3  drives piston  14  into the wedge  13 . Spring  6  biases wedge  13  into piston  14 . In operation, piston  14  is driven into wedge  13 , thereby expanding wedge  13  against surface  17 . The frictional force between wedge surface  16  and surface  17  damps the motion of the wedge and thereby the motion of the piston  14 . Note that although surface  17  is shown as cylindrical in this FIG. 3, surface  17  may have other shapes or profiles as shown in the other figures described in this specification.  
         [0048]    [0048]FIG. 4 is a perspective view of the wedge. Camming body or wedge  13  comprises surface  16  that slidingly engages inner surface  17  of housing  1 . Wedge  13 , and more particularly, surface  16  may have a pleated or star shape. This shape serves to increase the frictional forces, between surface  16  and inner surface  17 . Inner surface  17  and surface  16  may have any shape, so long as they are able to be properly mated to maximize surface contact between them and are able to slide relative to each other along a common axis, A, without binding.  
         [0049]    [0049]FIG. 5 is a perspective view of the piston  14 . Piston  14  comprises tapered end  19  and end  20 . Tapered end  19  cooperates with tapered hole  15  in wedge  13 . Bearing point  18  bears upon end  20 . Although surface  16  is star shaped, tapered end  19  and tapered hole  20  each have a conical or frustoconcical shape. In the preferred embodiment, piston  14  comprises steel, although any durable material having similar frictional and compressive properties would be acceptable.  
         [0050]    [0050]FIG. 6 is a perspective view of the housing  1 . Housing  1  comprises inner surface  17 . Inner surface describes a pleated or star profile in order to cooperate with surface  16  of wedge  13 . In the preferred embodiment, housing  1  is constructed of aluminum, although any durable material having similar frictional and strength bearing properties would be acceptable. Housing  1  may b attached to a base (not shown) as part of a tensioner assembly as shown in FIG. 1.  
         [0051]    The operation of the tensioner is as follows. Reference is made to FIG. 7( a ), a schematic free body diagram of the damping mechanism during a compression stroke. During the compression stroke, the hubload HC bears upon piston  14 , which acts upon wedge  14 , shown as R. The movement of the tapered end  19  into hole  15  causes an outer circumference of wedge  13  to increase and press surface  16  against the inner surface  17 . Due to friction between the sides of the tapered end  19  and the sides of the tapered hole  15 , movement of piston  14  in direction C acts to move wedge  13  also in direction C. However, the movement of wedge  13  in direction C is resisted by spring  6 , the spring force being depicted as F s . A normal force is formed between the sides of the tapered end  19  and the sides of the tapered hole  15 , and is resolved into normal forces between them, N 1C  and N 2C . A frictional force acts between the sides of the tapered end  19  and the sides of the tapered hole  15  as well as between the sides of the wedge and the inner surface of the housing. A frictional force resisting the motion of the wedge in the housing is formed. These forces are μN 1C  and μN 2C . This force is additive with the spring force, F s , as each acts in the same direction. As the hubload increases, so increases HC. An increase in HC increases N 1C  and N 2C  until wedge  13  starts moving, which in turn increases the friction forces μN 1C  and μN 2C  resisting movement of the wedge in the housing. It should be noted that there is no further substantive increase in N 1C  and N 2C  when wedge  13  moves.  
         [0052]    On the return stroke, depicted in FIG. 7( b ) a free body diagram of the damping mechanism during the return stroke, the hubload is diminished. Once the hubload HR becomes less than the spring force F s  minus friction μN 1R , the wedge will be pushed in direction B. The normal forces, N 1R  and N 2R  are less than N 1C  and N 2C . Further, the friction force vector is in the opposite direction as compared to the compression stroke, μN 1R  and μN 2R . This frictional force resists the effort of the spring to move the wedge in direction B. The hubload HR required to keep the blocks in static equilibrium is reduced. Since the hubload is reduced, the frictional forces between the wedge and the inner surface of the housing are correspondingly reduced. Hence, the damping, or frictional force, is greater during the compression stroke than during the return stroke. Therefore, the tensioner exhibits asymmetric damping.  
         [0053]    An alternate embodiment is depicted in FIG. 8. Damper  100  comprises a cylinder slidingly engaged with another cylinder. Outer tube or housing  101  slidingly engages tube  108 . Cap  105  is attached to tube  101 . Cap  110  is attached to tube  108 . Spring  102  extends between cap  105  and end of tube  108 , thereby urging the tubes apart. Plastic liner  106  facilitates movement between outer tube  101  and tube  108 . Piston  111  is affixed to cap  110  and is parallel to a major axis of the tubes  101 ,  108 . Wedge  109  slidingly engages an inner surface  112  of tube  108 . Piston tapered end  104  engages tapered hole  113  in wedge  109 . Wedge  109  is urged into contact with piston  111  by spring  107 . Biasing member or spring  107  bears upon cap  110  and wedge  109 . Cap  110  may be affixed to a mounting surface, such as on a tensioner body as described in FIG. 1.  
         [0054]    In operation, cap  105  moves in direction C during a compression stroke. It moves in direction R during a return stroke. The detailed description of operation is set forth in FIG. 7( a ) and FIG. 7( b ). Further, during the compression stroke, the wedge  109  is pushed in direction C, thereby causing behavior as described in FIG. 7( b ) for the return stroke. The damping force in is increased during the return stroke in direction R since the inner surface  112  is moving in a manner so as to press wedge  109  into the tapered end  119  of piston  104 . This is described in FIG. 7( a ). One skilled in the art will appreciate that the mechanism described in this FIG. 8 depicts a damping mechanism that is operable in various applications including a belt tensioner with a pulley.  
         [0055]    [0055]FIG. 9 is a detail of the wedge in FIG. 8. Wedge  109  comprises splines or pleats  114 . Splines  114  cooperatively engage a like shape on the inner surface  112  of tube  101  as shown in FIG. 10. Wedge  109  may have radially extending slots  115  that facilitate expansion of the wedge against the inner surface  112 . Wedge splines  114  may comprise a nonmetallic material, such as plastic or phenolic.  
         [0056]    [0056]FIG. 10 is an end view of the outer tube. Tube  101  comprises inner surface  112 . Surface  112  describes a pleated or splined profile that cooperatively engages splines  114  on wedge  104 . Surface  112  and splines  114  each comprise materials that create a desired frictional coefficient. For example, the splines  114  may comprise a plastic, phenolic or non-metallic material while surface may comprise like materials. The preferred embodiment comprises a non-metallic material on splines  114  and a metallic material on surface  112 , as well as surface  112  (FIG. 10), surface  212  (FIG. 11, 18), surface  312  (FIG. 20).  
         [0057]    [0057]FIG. 11 is a cross-sectional view of a second alternate embodiment of the invention. In this alternate embodiment, spring  202  is contained within tube  201 . Damper  200  comprises a cylinder slidingly engaged within another cylinder. Outer tube  201  slidingly engages tube  208 . Cap  205  is attached to tube  208 . Cap  210  is attached to tube  201 . Biasing member or spring  202  extends between tube  208  and cap  210 , thereby urging them apart. Plastic liner  206  facilitates sliding movement between outer tube  201  and tube  208 . One end of piston  211  is affixed to cap  210  and is parallel to a major axis of the tubes  201 ,  208 . Wedge  209  slidingly engages an inner surface  212  of tube  208 . Piston tapered end  204  engages tapered hole  213  in wedge  209 . Wedge  209  is urged against tapered end  204  by compressible member or spring  207 . Spring  207  bears upon cap  210  and wedge  209 . Cap  210  is affixed to a mounting surface, such as on a tensioner body as described in FIG. 1. One skilled in the art will appreciate that the mechanism described in this FIG. 11 depicts a damping mechanism that is operable on other applications including a tensioner with a pulley.  
         [0058]    In operation, cap  205  moves in direction C during a compression stroke. Cap  205  moves in direction R during a return stroke. The detailed description of operation is set forth in FIGS.  7 ( a ),  7 ( b ) and FIG. 8.  
         [0059]    [0059]FIG. 12 depicts another alternate embodiment of the damper  300 . The elements are generally as described in FIG. 11 with the following differences; washer, ring or bearing surface  308  is affixed to piston  211  at a pre-determined point. Bearing surface  308  extends normally to the piston axis D. Compressible member or spring  307  bears on the bearing surface  308 . The other end of spring  307  bears on camming body or wedge  309 . Wedge  309  is of substantially the same form as wedge  209  in FIG. 11. One skilled in the art will appreciate that the mechanism described in this FIG. 12 depicts a damping mechanism that is operable on other applications including a tensioner with a pulley.  
         [0060]    Reference to FIG. 11 and FIG. 12 also illustrates the change in length L 1  and L 2  as the invention operates. Lengths increase during the return stroke R (L 2 ) and decrease during the compression stroke C (L 1 ).  
         [0061]    [0061]FIG. 13 is a cross-sectional view along axis A-A of yet another alternate embodiment of the invention. First housing or cap  405  comprises first housing surface or side  408 . Second housing or tube  401  further comprises outer surface  412 . Side  408  describes a conical form having an angle α to the major axis A in the range of 0° to 30°. Side  408  may have any form required by a user, including pleated. Wedge  409  slides between side  408  and outer surface  412 . Spring  402  urges wedge  409  into contact with side  408  and outer surface  412 . As wedge  409  is urged against surface  412 , it is radially compressed. Radial compression of wedge  409  occurs due to the presence of the slots as described in FIG. 2 and FIG. 21. Spring  402  bears on base  410 , which is affixed to tube  410 . Cap  405  moves in direction C during a compression stroke and in direction R during a return stroke. A load L may be applied to the device at bearing point  418 . One skilled in the art will appreciate that the mechanism described in this FIG. 13 depicts a damping mechanism that is operable on other applications including a tensioner with a pulley.  
         [0062]    [0062]FIG. 14 is a cross-sectional view along axis A-A of yet another alternate embodiment of the invention. First housing or tube  501  comprises first housing surface or side  508  and end  510 . Side  508  describes a conical form having an angle β to the major axis A in the range of 0° to 30°. Side  508  may have any profile required by a user including pleated. Wedge  509  slides between first housing surface or side  508  and outer surface  516  of piston  514 . Wedge  509  has the same form as shown in FIG. 21 for wedge  409 . Body  519  and surfaces  516  have the same form as shown in FIG. 21 for surface  412 . Spring  502  bears on end  510  and piston  514 . Spring  502  resists an axial movement of piston  514 . Compressible member or spring  502  also bears on base  510  against piston  514 . Compressible member or spring  507  urges wedge  509  into contact with side  508  and outer surface  516  of piston  514 . As wedge  509  is urged against surface  516 , it is radially compressed. Radial compression of wedge  509  occurs due to the presence of the slots as described in FIG. 2 and FIG. 21. Piston  514  moves in direction C during a compression stroke and in direction R during a return stroke. An axial load L may be applied to the device at bearing point  518 . One skilled in the art will appreciate that the mechanism described in FIG. 14 depicts a damping mechanism that is operable on other applications including a tensioner with a pulley.  
         [0063]    [0063]FIG. 15 is a plan view of a tensioner damper assembly. Damper  600  as described in the foregoing FIGS.  8 ,  11 - 14  is shown connected to an idler pulley  610  by shaft  620 . Shaft  620  may be connected to a base (not shown) that connects the idler to tracks  615 . Idler  610  slides along parallel tracks  615 . Belt B is trained about idler  610 .  
         [0064]    [0064]FIG. 16 is a perspective exploded view of the damping mechanism for an alternate embodiment. FIG. 16 generally describes the arrangement of the damping mechanism for the embodiments depicted in FIGS. 8, 11 and  12 . The numbers in FIG. 16 relate to FIG. 8. Surfaces  114  slidingly engage surfaces  112 . Tapered end  104  engages hole  113 . Slots  115  allow wedge  109  to radially expand as tapered end  104  moves axially into wedge  109 . Wedge  109  may comprise a nonmetallic material, such as plastic or phenolic.  
         [0065]    [0065]FIG. 17 is an end plan view of the wedge for an alternate embodiment. The alternate embodiment is depicted in FIG. 11. Wedge splines  214  may comprise a nonmetallic material, such as plastic or phenolic.  
         [0066]    [0066]FIG. 18 is an end plan view of the tube of an alternate embodiment. The alternate embodiment is depicted in FIG. 11.  
         [0067]    [0067]FIG. 19 is an end plan view of the wedge for an alternate embodiment. The alternate embodiment is depicted in FIG. 12. Wedge splines  314  may comprise a nonmetallic material, such as plastic or phenolic.  
         [0068]    [0068]FIG. 20 is an end plan view of the tube of an alternate embodiment. The alternate embodiment is depicted in FIG. 12.  
         [0069]    [0069]FIG. 21 is an exploded view of the wedge and tube for an alternate embodiment. The embodiment is depicted in FIG. 13. FIG. 21 also generally depicts the arrangement of the wedge  509  and the piston surfaces  516  for the embodiment depicted in FIG. 14. Slots  415  allow wedge  409  to radially compress against surfaces  412 . Wedge  409  may comprise a nonmetallic material, such as plastic or phenolic.  
         [0070]    Although a single 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 without departing from the spirit and scope of the invention described herein.

Technology Category: f