Abstract:
A handlebar for a vehicle made of a tubing. The tubing includes a central region, bent regions extending from opposing ends of the central region, and handgrip regions extending from the distal ends of the bent regions. The central region is configured to permit attachment to the vehicle by a securing member. Each bent region includes a bent portion at each of the two opposing ends of the bent region. A rod disposed within the tubing contacts an inner wall of the tubing at the four bent portions.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the U.S. Provisional Application No. 60/291,748 filed May 16, 2001, and whose entire contents are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention is directed to handlebars and, more particularly, to handlebars with an adjustable dampening mechanism for motorcycles, bicycles, all terrain vehicles, and personal watercrafts. 
     BACKGROUND OF THE INVENTION 
     Handlebars for motorcycles generally comprise a single length of low carbon alloy steel tube appropriately bent to provide a central region, bent regions, and respective handgrip regions, the former being clamped at one or two positions to form a connection to the main cycle frame via an intermediate top yoke or stem. To reduce weight, aftermarket handlebars are typically formed from aluminum. For additional strength, it has been conventional to provide a crossbar spanning the central region of the aluminum tube. Alternatively, the handlebar may be strengthened by providing an aluminum tube with a greater external diameter at the central region, wherein the diameter of the aluminum tube is gradually reduced towards the distal ends. 
     U.S. Pat. No. 4,635,499 discloses a conventional handlebar  10  of the first type. This type of handlebar  10  is commonly used for offroad motorcycles, all terrain vehicles and personal watercrafts. Referring to FIG. 1, the handlebar  10  has a central region  12 , two bent regions  14 ,  16 , and two handgrip regions  18 ,  20 . The diameter of the handlebar  10  is uniform throughout the entire lengthwise dimension. In general, the preferred diameter of conventional handlebars is ⅞ inch because this provides the handgrip regions  18 ,  20  with the proper amount of thickness so that a handgrip with a thickness of approximately ⅛ to ¼ inch can be fitted over a portion of each handgrip region  18 ,  20 . Although a ⅞ inch diameter tubing  22  is ideal for facilitating a properly sized handgrip for the rider, the tubing  22  does not have sufficient strength to withstand the impact of heavy loads. As such, a crossbar  24  is used to reinforce the tubing  22  and to prevent the tubing  22  from buckling. The crossbar  24  is attached between the two bent regions  14 ,  16  and is oriented generally parallel to the central region  12 . When the crossbar  24  is used, a permanent compression set occurs in the bent regions  14 ,  16  in the event of an impact. Furthermore, the crossbar  24  provides no added benefit when steering the vehicle because the crossbar  24  reinforces the handlebar  10  in only the vertical direction while providing no reinforcement in the horizontal direction. Another problem with the crossbar  24  is that a permanent compression set may occur in the event of an impact because the attachment points  26 ,  28  of the crossbar  24  at the bent regions  14 ,  16  act as a stress concentration site. In addition, the crossbar  24  constrains any movement of the tubing  22  that would soften shock loads to the handgrip regions  18 ,  20 . The crossbar  24  may further be a safety hazard. In particular, the rider may impact the crossbar during a crash. 
     In order to resolve some of the problems associated with crossbars, U.S. Pat. No. 5,257,552 discloses an integrally formed unitary hollow tubular handlebar  50  of the latter type wherein the wall thickness is greatest and constant in the central region  52 , smallest and constant at the handgrip regions  54 ,  56 , and tapering in the bent regions  58 ,  60  as shown in FIG.  2 . This improved handlebar  50  eliminates the need for a crossbar by increasing the diameter and sidewall thickness of the central region  52  of the handlebar  50 , while the reduction in diameter along the bent regions  58 ,  60  and handgrip regions  54 ,  56  allows the use of standard handgrips. Without the crossbar, the handlebars  50  has a longer unsupported span, thereby providing more cushioning strength and greater steering control. However, the problem with such a configuration is that a custom triple clamp assembly must be used to secure the handlebar  10  to the main frame of the vehicle because the diameter of the central region  52  is greater than the standardized ⅞ inch diameter. As a result, the available selection of triple clamp assemblies is relatively limited and custom units, which are generally costly, may be required. Furthermore, it is substantially more costly to fabricate tapered handlebars than handlebars with uniform tubes. 
     U.S. Pat. No. 6,182,528 discloses another handlebar configuration which eliminates the need of a crossbar by having a unitary handlebar  100  comprising an inner tubular member  102  of constant diameter and constant wall thickness and an outer tubular sleeve  104  surrounding the inner tubular member  102  as shown in FIG.  3 . Both the inner tubular member  102  and the outer tubular sleeve  104  have a central region  106 , bent regions  108 ,  110 , and handgrip regions  112 ,  114 . The handgrip regions  112 ,  114  of the inner tubular member  102  extend beyond the handgrip regions  112 ,  114  of the outer tubular sleeve  104 . The two-layer configuration allows the use of two different materials to provide a stronger, but more notch sensitive material for the inner tubular member  102  and a more ductile but less notch sensitive material with greater fatigue resistant properties for the outer tubular sleeve  104 . This configuration is advantageous in minimizing stress and impact damage at the locations where the handlebar  100  is clamped to the triple clamp assembly. In the manufacturing process, the inner tubular member  102  and the outer tubular sleeve  104  are formed separately from metal tubes. The thickness of the outer tubular sleeve  104  is reduced prior to insertion of the inner tubular member  102 . Thereafter, the outer tubular sleeve  104  and inner tubular member  102  are shaped together by bending in a conventional manner. Although the outer tubular sleeve  104  comprises a ⅞ outer diameter which is compatible with standard triple clamp assemblies, the fabrication costs are relatively high due to the two-layer construction. 
     In view of the above, it is apparent that there is a need to provide a handlebar which is capable of withstanding large impact loads while being sufficiently flexible to dampen some of the impact loads. However, the preferred dampening characteristics of the handlebar may depend on the particular riding application (i.e. moto-cross, super cross, desert riding, etc.), physical characteristics of the rider (i.e. size, weight, strength, etc.), suspension system of the vehicle (i.e. spring rate of the fork tubes, xxx, etc.), and the personal preference of the rider. This is particularly important for racing purposes where a slight improvement in the performance of the vehicle provides the rider with a competitive advantage. An operator may incur substantial costs to meet these requirements, wherein a number of prototype handlebars may be needed to first determine the appropriate handlebar configuration for a particular rider and track. Since a rider usually operates the vehicle at several tracks, an inventory of handlebars tailored for each or at least some of the tracks may be needed. In addition to the development and inventory costs, preparation of the vehicle for a particular track may include removal and installation of the handlebar. Thus, there is a need to provide a handlebar which is adaptable to various track and rider conditions. There is also a need to provide a handlebar which is lightweight, durable, easy to manufacture, compatible with existing vehicles, and relatively inexpensive. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a handlebar is provided with a titanium tubing capable of absorbing impact loads to reduce rider fatigue and enhance control of a vehicle. In particular, the handlebar is configured with a relatively long unsupported span which allows the tubing to react more readily to impact loads by flexing. The handlebar includes a central region having a first end and a second end, a first bent region extending from the first end of the central region, a second bent region extending from the second end of the central region, a first handgrip region extending from a distal end of the first bent region, and a second handgrip region extending from a distal end of the second bent region. Bent portions adjoin each of the regions. The handlebar is formed by extruding the tubing, cutting the tubing to the desired length, and bending the tubing in the extruded state. 
     The handlebar further includes an adjustable dampening mechanism which allows an operator to vary the stiffness of the handlebar. The adjustable dampening mechanism includes a rod disposed within the tubing, wherein the rod contacts the internal wall of the tubing at the bent portions. The bending resistance of the rod at the bent portions increases the stiffness of the handlebar. Stiffness of the handlebar can be increased or decreased by respectively increasing or decreasing rod tension. 
     Other aspects, features and techniques of the invention will become apparent to one skilled in the relevant art in view of the following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a prior art handlebar having a crossbar; 
     FIG. 2 is a perspective view of another prior art handlebar having a large diameter central region, tapered bent regions, and handgrip regions; 
     FIG. 3 is a perspective view of another prior art handlebar having a dual-layer tube construction; 
     FIG. 4 is a top plan view of an exemplary handlebar of the present invention; 
     FIG. 5 is a front plan view of the handlebar of FIG. 4 illustrating an adjustable dampening mechanism; 
     FIG. 6 is a top plan view of another exemplary handlebar of the present invention; 
     FIG. 7 is a front plan view of the handlebar of FIG. 6 illustrating an adjustable dampening mechanism; and 
     FIG. 8 is a flow diagram for the process of making the handlebars shown in FIGS. 4 through 7. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     A handlebar  200  of the present invention for motorcycles, bicycles, all terrain vehicles, personal watercrafts and other forms of handlebar steered vehicles is shown in FIGS. 4 and 5. The handlebar  200  may be formed from a single length of tubing  202  such as chrome molybdenum, aluminum, titanium, or the like. In this particular embodiment, Ti-3Al-2.5V is used. However, any titanium alloy having a tensile strength of at least 120 ksi may be used. The handlebar  200  is shown having a conventional steerhorn shape but any other shape may be used. The handlebar  200  includes a central region  204 , bent regions  206 ,  208  extending distally from the ends of each central region  204 , and handgrip regions  210 ,  212  extending distally from the ends of each central region  204 . Bent portions  214 ,  216 ,  218 ,  220  adjoin each of the regions  204 ,  206 ,  208 ,  210 ,  212 . The lengths of these regions  204 ,  206 ,  208 ,  210 ,  212  and the relative angles of the bent portions  214 ,  216 ,  218 ,  220  may vary depending on the type of vehicle. 
     The tubing  202  has a constant outer diameter and wall thickness throughout its entire length. In the particular embodiment shown in FIGS. 4 and 5, the handlebar  200  has an outer diameter of ⅞ inch and a wall thickness of 0.061 inch. A ⅞ inch outer diameter is selected because it is compatible with factory triple clamp assemblies for off road motorcycles configured for Moto-Cross, Super Cross and Desert Riding. It is contemplated that the wall thickness may range from 0.061 inches to 0.250 inches for most applications. 
     Referring to FIG. 5, the handlebar  200  has an adjustable dampening mechanism  222  to further strengthen the handlebar  200  and to enable an operator to selectively adjust the stiffness of the handlebar  200 . In lieu of a crossbar, the adjustable dampening mechanism  222  provides additional structural support such that the tubing  202  is not limited to titanium. As discussed previously, the tubing  202  may be made from conventional alloys other than titanium such as chrome molybdenum, aluminum, magnesium and the like. 
     Referring back to FIG. 5, the adjustable dampening mechanism  222  has a rod  224  with ends respectively secured to the handgrip regions  206 ,  208  by a first rod restraint  226  and a second rod restraint  228 . In the exemplary embodiment, the outer diameter of the rod  224  may range from about ¼ inch to about {fraction (3/16)} inch and may be formed from a high strength material which is resistant to bending such as 15-5 heat treated stainless steel, 6-4 heat treated titanium, 4130 heat treated carbon steel, and the like. Preferably, the tensile strength of the rod  224  is greater than the tensile strength of the tubing  202  such that the rod  224  is able to further stiffen the handlebar  200 . The first  226  and second rod restraint  228  have an outer tubular surface which abuts the interior wall of the tubing  202 . Rings  230 ,  232  extends radially outwardly from the distal ends of the outer tubular surfaces such that the first  226  and second rod restraint  228  are inserted into the tubing  202  and are lockingly secured to the tubing  202  as the rings  230 ,  232  abut the distal ends of the tubing  202 . One end of the rod  224  is secured to the first rod restraint  226  by a groove  234  and flange  236  arrangement. The other end of the rod  224  is secured to an adapter  238  by another groove  240  and flange  242  arrangement. The adapter  238  is appropriately sized to allow distal/proximal movement within the tubing  202 . The adapter  238  is coupled to the second rod restraint  228  by a bias member. In the exemplary handlebar  200 , the bias member is an Allen head screw  244  which engages threads  246  of the adapter  238 , wherein rotation of the Allen head screw  244  moves the adapter  238  in a proximal or distal direction. More specifically, clockwise rotation of the Allen head screw  244  causes the adapter  238  to move distally such that rod tension is increased, while counterclockwise rotation of the Allen head screw  244  causes the adapter  238  to move proximally such that rod tension is decreased. It is contemplated that the Allen head screw  244  may have an adjustment range of ten (10) clicks. However, the range may be increased or decreased if necessary. 
     Preferably, the rod  224  is substantially straight when unloaded (i.e. when the rod  224  is not disposed within the tubing  202 ). As shown in FIG. 5, the rod  224  is forced to partially conform with the shape of the tubing  202 . The rod  224  abuts the interior wall of the tubing  202  at the first bent portion  214 , the second bent portion  216 , the central region  204 , the third bent portion  218 , and the fourth bent portion  220 . As the Allen head screw  244  is rotated clockwise, the rod  224  is further tensioned such that the contact forces at the first  24 , second  216 , third  218 , and fourth bent portion  220  are increased. 
     When a rider imposes a downward force on the handgrip regions  210 ,  212 , the handlebar  200  deflects downwardly. During the downward deflection of the handlebar  200 , the rod  224  is forced to further bend at the first  214  and fourth bent portion  220  because the contact forces at these regions are further increased, while bending of the rod  224  is reduced at the second  216  and third bent portion  218  because the contact forces at these regions are decreased. Thus, the rod  224  provides the handlebar  200  with additional resistance to bending in the downward direction due to the rod  224  providing a bending resistance at the first  214  and fourth bent portion  220 . In a similar fashion, a rider imposing an upward force on the handgrip regions  210 ,  212  causes the handlebar  200  to deflect upwardly. During the upward deflection of the handlebar  200 , the rod  224  is forced to further bend at the second  216  and third bent portion  218  because the contact forces at these regions are further increased, while bending of the rod  224  is reduced at the first  214  and fourth bent portion  220  because the contact forces at these regions are decreased. Thus, the rod  224  provides the handlebar  200  with additional resistance to bending in the upward direction due to the rod  224  providing a bending resistance at the second  216  and third bent portion  218 . 
     In order to further stiffen the handlebar  200 , the Allen head screw  244  may be rotated in the clockwise direction to further tension the rod  224 . As rod tension is increased, the rod  224  exhibits an increased resistance to bending, and the handlebar  200  is further stiffened. The stiffness of the handlebar  200  may be reduced by simply, rotating the Allen head screw  244  in the counterclockwise direction. 
     Referring to FIGS. 6, and  7 , another exemplary handlebar  200 ′ of the present invention is shown. The handlebar  200 ′ is similar to the embodiment shown in FIGS. 4 and 5 with the exception that the tubing  202 ′ is not bent in the horizontal direction. As such, the tubing  202 ′ appears straight when viewed from the top as shown in FIG.  6 . Like components are numbered with the same number and with a prime. 
     FIG. 8 is a flow diagram illustrating the process of fabricating the handlebars  200 ,  200 ′ shown in FIGS. 4 through 7. For the sake of brevity, the following description refers to the handlebar  200  shown in FIGS. 4 and 5. However, it is noted that the following description is similarly applicable to the handlebar  200 ′ shown in FIGS. 6 and 7. The handlebar  200  may be formed by cold extruding the titanium alloy tubing  202 . The extruded tubing  202  is then cut to the desired length. The tubing  202  is then bent from the cold extruded “as drawn” state to form the bent portions  214 ,  216 ,  218 ,  220  and to define the central region  204 , the pair of bent regions  206 ,  208 , and the pair of handgrip regions  210 ,  212 . 
     Generally, tubing formed from high strength titanium alloys require annealing prior to forming the small radii bends for handlebars. It has been discovered that the annealing procedure is not required by using a high speed, Computer Numerical Control (CNC) bending apparatus which maintains the “as drawn” tubing  202  in the plastic state during bending. In particular, the “as drawn” tubing  202  is bent at a relatively high and continuous rate to form the bent portions  214 ,  216 ,  218 ,  220  without buckling and to minimize spring back of the tubing  202 . The CNC bending apparatus has a programmed bend rate velocity ranging from 10% to 100%, wherein 100% bend rate velocity correlates to a bending rate of 30 revolutions per minute. The correlation is linear such that a 10% bend rate velocity correlates to a bending rate of 3 revolutions per minute. It is noted that other types of bending apparatuses capable of bending non annealed titanium tubes at a relatively high and continuous rate may be used. After the tubing  202  is formed to shape, the handlebar  200  may be cosmetically finished with a coating such as paint, plated, textured by bead blasting, shot peened, polished, or left untreated with the extruded surface finish. 
     By forming the handlebar  200  from a single length of “as drawn” titanium tubing  202 , the handlebar  200  is lightweight, strong, flexible, and durable. Due to the significant strength of the “as drawn” titanium tubing  202 , a crossbar is not required and the standardized ⅞ inch outer diameter may be used. The ⅞ inch outer diameter tubing  202  is compatible with most existing triple clamp assemblies and is the preferred diameter for overlapping handgrips (not shown) having a thickness of about ¼ inch, which is best suited for the hands of a typical rider. The elimination of the crossbar not only reduces the weight of the handlebar  200 , but also enables the handlebar  200  to absorb more impact energy and thus transmit less shock to the rider&#39;s hand, reduce rider fatigue, and provide improved control of the vehicle. In particular, the unsupported span is increased from a length l of a typical handlebar  10  with a crossbar to a length l′ of the handlebar  200  of the present invention, wherein the increase in unsupported length allows the tube  202  to react more readily to impact loads by flexing. In addition, with prior art handlebars with crossbars, shock and vibration from one side of a handlebar is transmitted to the other side of the handlebar via the crossbar. The elimination of the crossbar permits each side of the handlebar to function independently. 
     It is noted that one of the unique features resulting from eliminating the annealing process prior to bending is that a post heat treatment process is not required to strengthen the handlebar  200 . As a result, the tensile strength of the bent portions  214 ,  216 ,  218 ,  220  is great than the central region  204 , the bent regions  206 ,  208 , and the handgrip regions  210 ,  212 , and the likelihood of breakage at these cites due to fatigue and/or large impact loads is reduced. In other words, the work hardening resulting from the bending process is not negatively affected by a post heat treatment process. Furthermore, processing costs are reduced by eliminating the annealing process for softening the tubing and the heat treatment process for strengthening. 
     The adjustable dampening mechanism  222  may be installed by attaching the first rod restraint  226  to one end of the rod  224  and attaching the adapter  238  to the other end of the rod  224 . The arrangement is forced into the tubing  202  until the ring  230  of the first rod restraint  226  abuts the distal end of the tubing  202 . The second rod restraint  228 , is inserted into the other end of the tubing  202 , and the Allen head screw  244  is rotated in the clockwise direction to engage with the threads  246  of the adapter  238 . The Allen head screw  244  is rotated in the clockwise direction until the rod  244  is tensioned to a predetermined preload. An operator may later fine tune the handlebar  200  by rotating the Allen head screw  244  in the appropriate direction. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. For example, there are a number of alternate configurations in which the rod may be adjustably tensioned. The adjustable dampening mechanism may include a pair of rod restraints and a corresponding pair of adapters with Allen head screws so that the dampening of the handlebar may be adjusted by rotating both Allen head screws. Furthermore, the Allen head screw may be replaced by a bolt, ratchet mechanism, or other mechanism which distally/proximally moves the adapter. In another possible configuration, the rod restraints may not be required by providing the adapter with a threaded outer surface which engages with a threaded inner wall of the tubing. With such a configuration, the rod may be further tensioned by rotating the adapter relative to the tubing.