Abstract:
A method of making a portion of a bicycle frame including positioning a low-friction mandrel adjacent a flexible mandrel with a first fibrous material in between. The mandrels are wrapped with second fibrous material, and the mandrels are inserted into a mold. The second fibrous material is cured to produce a cured assembly, the cured assembly is withdrawn from the mold, and the low-friction mandrel is removed from the cured assembly to produce an internal passageway. The flexible mandrel can includes a recess, and the step of positioning can include inserting the low-friction mandrel into the recess of the flexible mandrel. Preferably, the low-friction mandrel has a cross sectional shape that substantially matches a cross-sectional shape of the recess. The invention is also embodied in a portion of a bicycle frame, such as a portion of the frame during the manufacturing process, and having similar features as recited above.

Description:
BACKGROUND 
     The present invention relates generally to the field of bicycles and specifically to bicycle frames having actuating cables positioned inside frame members. 
     Many bicycles have brakes for slowing the vehicle speed and shifters for changing gears. The brakes and shifters are commonly actuated by the user via brake levers and shift levers, respectively. Movement of the levers is transmitted to the brakes and shifters via a transmission member, such as wires, cables, rods, hydraulic fluid, or other suitable mechanism (hereinafter referring to as “transmission member”). These transmission members can include a movable member (e.g., a braided cable) positioned inside and movable relative to a stationary housing that guides the movable member. 
     In order to improve the aesthetics and aerodynamics of the bicycle, the transmission members are often routed through the interior of the bicycle frame. To facilitate this, frames can be provided with entry and exit openings that allow the transmission member to enter and exit the interior of the frame, respectively. In existing bicycles, the cables must be “fished” out of the interior, and because the interior of the frame is relatively large compared to the size of the cables, this process can be time consuming and complicated. 
     SUMMARY 
     The present invention provides a method of making a portion of a bicycle frame. The method includes positioning a low-friction mandrel (e.g., made from polytetrafluoroethylene) adjacent a flexible mandrel (e.g., made from silicone) with a first fibrous material (e.g., fibers pre-impregnated with an uncured matrix) in between the low-friction mandrel and the flexible mandrel. The flexible mandrel and low-friction mandrel are then wrapped with second fibrous material (e.g., fibers pre-impregnated with an uncured matrix), and the flexible mandrel and low-friction mandrel are then inserted into a mold. The second fibrous material is then cured to produce a cured assembly, the cured assembly is withdrawn from the mold, and the low-friction mandrel is removed from the cured assembly to produce an internal passageway. 
     The flexible mandrel can include a recess, and the step of positioning can include inserting the low-friction mandrel into the recess of the flexible mandrel. Preferably, the low-friction mandrel has a cross sectional shape that substantially matches a cross-sectional shape of the recess. Preferably, the flexible mandrel comprises a hollow interior, and the method further includes inserting an inflatable bladder into the hollow interior and, prior to the curing step, inflating the bladder to press the second fibrous material outward toward the mold. 
     The present invention is also embodied in a portion of a bicycle frame, such as a portion of the frame during the manufacturing process. The portion of the bicycle frame includes a flexible mandrel (e.g., made from silicone), a low-friction mandrel positioned adjacent the flexible mandrel, a first fibrous material (e.g., a fiber-matrix composite) positioned between the low-friction mandrel and the flexible mandrel, and a second fibrous material (e.g., a fiber-matrix composite) wrapped around the flexible mandrel and the low-friction mandrel. Preferably, the flexible mandrel comprises a recess and the low-friction mandrel is positioned in the recess. For example, the low-friction mandrel can have a cross sectional shape that substantially matches a cross-sectional shape of the recess. In one embodiment, the low-friction mandrel has a mandrel head protruding out of the recess to thereby facilitate removal of the low-friction mandrel. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a bicycle including a frame embodying the present invention. 
         FIG. 2  is a perspective section view of a portion of the frame taken along line  2 - 2  in  FIG. 1  and including the head tube, a portion of a top tube, and a portion of a down tube with cables routed into the down tube. 
         FIG. 3  is a perspective section view of a portion of the head tube and the down tube illustrating cable routing channels in the down tube. 
         FIG. 4A  is a perspective view of cable routing mandrels wrapped with fibrous material. 
         FIG. 4B  is an exploded perspective view of the cable routing mandrels, a head tube mandrel, a top tube mandrel, and a down tube mandrel for forming a portion of the frame. 
         FIG. 4C  is a perspective view illustrating the mandrels of  FIGS. 4A and 4B  assembled together with fibrous material partially wrapped around the assembled mandrels to define a preform layup. 
         FIG. 4D  is a section view of the preform layup of  FIG. 4C  taken along line  4 D- 4 D. 
         FIG. 4E  is an exploded perspective view of two halves of a curing tool and the preform layup disposed in one half of the curing tool. 
         FIG. 5  is a perspective view of the frame portion after curing the fibrous material and illustrating the cable routing mandrels partially removed. 
         FIG. 6  is a perspective view of the frame portion after curing the fibrous material and illustrating the top tube and down tube mandrels partially removed. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 1  illustrates a bicycle  10  that includes a front wheel  15 , a rear wheel  20 , and a frame  25 . The frame  25  has a head tube  30  and a front fork  35  that is rotationally supported by the head tube  30  and that secures the front wheel  15  to the frame  10 . The frame  25  also has a top tube  40  that is connected to and extends rearward from the head tube  30 , and a down tube  45  that is connected to the head tube  30  below the top tube  40  and extends generally downward toward a bottom bracket of the frame  25 . A seat tube  55  extends upward from the bottom bracket and is connected to the top tube  40 , and a seat  60  is supported by the seat tube  55 . 
     The bicycle  10  also includes a handlebar  65 , a front derailleur  70 , a rear derailleur  75 , and a drivetrain  80  including a crankset  85  supported by the bottom bracket. The handlebar  65  is secured to the front fork  35  by a stem  90  such that movement of the handlebar  65  results in movement of the stem  90  and the fork  35 . With reference to  FIGS. 1 and 2 , the front derailleur  70  and the rear derailleur  75  are connected to respective shift actuators  95   a ,  95   b  (e.g., shift levers) located on the handlebar  65  by respective front and rear shift cables  100   a ,  100   b  that are routed along the interior of the down tube  45 . Also, a front brake  105  and a rear brake  110  are connected to respective brake actuators  115   a ,  115   b  (e.g., brake levers) located on the handlebar  65  by front and rear brake cables  120   a ,  120   b , respectively. The brake cable  120   b  associated with the rear brake  110  is routed along the interior of the down tube  45  from one of the brake actuators  115   a ,  115   b  on the handlebar  65 . 
     With reference to  FIGS. 2 and 3 , the illustrated down tube  45  is manufactured to be hollow and to include cable passageways  125  that are disposed on the inside of the down tube  45 . More specifically, the down tube  45  is defined by an outer frame wall  130  that substantially defines the hollow interior. The cable passageways  125  extend on the inside of the outer frame wall  130  longitudinally along the down tube  45  toward the bottom bracket. Each cable passageway  125  is separated from the hollow interior of the down tube  45  by an inner wall  135 . As illustrated, the frame  25  has access openings  140  that are located adjacent the front end of the down tube  45  on opposite sides of the frame  25  where the down tube  45  connects with the head tube  30  so that the cables  100   b ,  120   a ,  120   b  can be routed into the down tube  45 . 
     With reference to  FIGS. 4A-4E , the frame  25  is at least partially formed of fibrous material (e.g., carbon fiber-epoxy prepreg, uncured fiber matrix composite, etc.) using a mold or curing tool  145  and mandrels that cooperatively shape the frame  25 . As illustrated, the portion of the frame  25  (i.e. frame assembly  25   a ) defined by the head tube  30  and portions of the top tube  40  and the down tube  45  are formed using a head tube mandrel  150 , a top tube mandrel  155 , a down tube mandrel  160 , and cable routing mandrels  165 . Referring to  FIGS. 4B and 4C , the head tube mandrel  150  can take the form of a single mandrel or two mandrel halves. The head tube mandrel  150  has blind recesses  170  (one shown) that are disposed on both sides of the head tube mandrel  150  and that extend from a rear end of the mandrel  150  toward the front of the mandrel  150 . The illustrated blind recesses  170  are symmetrical about a central plane defined by the rear wheel  20 , although the blind recesses  170  can be asymmetrical relative to the central plane. The top tube mandrel  155  is coupled to a first mandrel post  175  extending rearward from adjacent a top of the head tube mandrel  150 . Also, each of the head tube mandrel  150  (or mandrel halves) and the top tube mandrel  155  is comprised of a flexible or resilient material (e.g., silicone) that can expand and contract in response to either or both pressure and heat. 
     With continued reference to  FIGS. 4B and 4C , the down tube mandrel  160  is coupled to a second mandrel post  180  extending rearward from adjacent a lower portion of the head tube mandrel  150 . The down tube mandrel  160  has recesses  185  disposed on opposite sides of the down tube mandrel  160  and is comprised of a flexible or resilient material (e.g., silicone) that can expand and contract in response to either or both pressure and heat. As illustrated, the recesses  185  align with the blind recesses  170  in the head tube mandrel  150  when the mandrels  150 ,  160  are attached to each other. Although the recesses  185  are illustrated as being symmetrical about the central plane, the recesses  185  can be positioned asymmetrically about the central plane. Also, one recess can be provided in lieu of two recesses (e.g., one recess along the inner bottom of the down tube  45 . 
     As illustrated in  FIGS. 4A, 4B, and 4D , each cable routing mandrel  165  is defined by an elongated body that has a cross-sectional shape that matches the cross-sectional shape of the blind recesses  170  in the head tube mandrel  150  and the recesses  185  in the down tube mandrel  160 . The cable routing mandrels  165  are comprised of a low-friction material (e.g., polytetrafluoroethylene (PTFE) or Teflon) that resists expansion and contraction. That is, the cable routing mandrels  165  generally maintain their size and shape when heat or pressure (or both) is applied to the mandrel, or at least maintain their size and shape better than the silicone mandrels. 
     As illustrated in  FIGS. 4A-4C , one end of each cable routing mandrel  165  (the end disposed adjacent the head tube  30 ) has a raised portion or mandrel head  190 . With reference to  FIGS. 1-3 and 4C , the mandrel head  190  protrudes outward from the outer surface of the head tube mandrel  150  when the cable routing mandrels  165  are coupled to the head tube and down tube mandrels  150 ,  160 . The mandrel head  190  on each side of the head tube mandrel  150  is left uncovered so that, after the frame  25  is cured, each mandrel head  190  defines one access opening  140 . 
     The head tube, top tube, and down tube mandrels  150 ,  155 ,  160  are assembled by connecting the top tube mandrel  155  to the first mandrel post  175  and connecting the down tube mandrel  160  to the second mandrel post  180 . The assembled head tube, top tube, and down tube mandrels  150 ,  155 ,  160  cooperate to define a flexible mandrel assembly to which the cable routing mandrels  165  are attached. 
     With reference to  FIG. 4A , the cable routing mandrels  165  are wrapped with one or more layers of first fibrous material  195  (e.g., carbon fiber-epoxy prepreg, uncured fiber matrix composite, etc.) until a desired thickness of material is achieved. During this process, the first fibrous material  195  is not wrapped around the mandrel heads  190 ; instead, at least a portion of the mandrel heads  190  is left exposed. 
     With reference to  FIGS. 4B and 4C , the wrapped cable routing mandrels  165  are positioned in the recesses  185  in the assembled head tube and down tube mandrels  150 ,  160 . In this position, the first fibrous material  195  is positioned between the head tube and down tube mandrels  150 ,  160  and the cable routing mandrel  165 . Next, the flexible mandrel assembly and the cable routing mandrels  165  are wrapped with one or more layers of second fibrous material  200  (e.g., carbon fiber-epoxy prepreg, uncured fiber matrix composite, etc.) until a desired thickness of second fibrous material  200  is achieved. The first and second fibrous materials  195 ,  200  are uncured prior to placement in the curing tool  145 . As used herein, the term “uncured” means that the material is not fully cured (i.e. the material could be uncured or partially cured). The wrapped mandrel assembly defines a pre-form layup that can be placed in the curing tool  145  to form the frame assembly  25   a . It will be appreciated that  FIG. 4C  illustrates the mandrel assembly during the wrapping process (i.e. before the wrapping process is completed). 
     With reference to  FIG. 4D , the second fibrous material  200  substantially defines the outer frame wall  130  when the frame assembly  25   a  is cured, and the first fibrous material  195  and the second fibrous material  200  cooperatively define the portion of the outer frame wall  130  where the fibrous materials overlay each other. That is, the first fibrous material  195  and the second fibrous material  200  partially overlap each other along portions of the down tube  45 . As illustrated, the first fibrous material  195  that is positioned or sandwiched between the down tube mandrel  160  and the cable routing mandrels  165  defines the inner wall  135  of the cable passageways  125  when the frame assembly  25   a  is cured. 
     Each of the head tube mandrel  150 , the top tube mandrel  155 , and the down tube mandrel  160  is hollow. When the mandrels  150 ,  155 ,  160 ,  165  are assembled, an inflatable bladder  205  (e.g., nylon bag) is inserted and fed into the hollow of each mandrel  150 ,  155 ,  160  to assist with forming the frame  25 . The illustrated bladder  205  is inserted into the mandrels  150 ,  155 ,  160  via an opening  210  in the down tube mandrel  160  before the layup or wrapping process begins. That said, the bladder  205  can be inserted into the mandrels  150 ,  155 ,  160  at any time prior to curing the first and second fibrous materials  195 ,  200  (e.g., before or after wrapping the mandrels, after the wrapped mandrel assembly is placed in the curing tool  145  and before curing the first and second fibrous materials  195 ,  200 ). Also, more than one bladder can be used to assist with forming the frame  25 . For example, a first bladder can extend through the down tube mandrel  160  and the bottom half of the head tube mandrel  150 , and a second bladder can extend through the top tube mandrel  155  and the top half of the head tube mandrel  150 . Other variations of bladder positioning can also be used. 
     Referring to  FIG. 4E , curing tool  145  includes two mold halves  215  each defining a frame pocket  220 . The frame pockets  220  cooperatively define the outer surfaces of the frame  25  after the frame  25  is cured. The mold halves  215  also include a plurality of holes  225  that are used to align and/or secure the mold halves  215  to each other after the wrapped mandrel assembly is placed in the curing tool  145 .  FIG. 4E  illustrates the partially wrapped mandrel assembly of  FIG. 4C  positioned in one of the frame pockets  220 , although it should be understood that the mandrel assembly will be fully wrapped prior to placement in the curing tool  145  when forming the frame  25 . 
     After the wrapped mandrel assembly is positioned in the curing tool  145 , the mold halves  215  are secured to each other. The bladder  205  is accessible from outside the curing tool  145  so that the bladder  205  can be inflated to expand the head tube mandrel  150 , the top tube mandrel  155 , and the down tube mandrel  160  within the frame pockets  220 . The down tube mandrel  160  and the cable routing mandrels  165  cooperate with each other and have sufficient rigidity to maintain desired internal features of the down tube  45  during the curing process. With the bladder  205  inflated, heat is applied to the curing tool  145  to produce the cured frame assembly  25   a . After the curing process is complete, the cured frame assembly  25   a  is removed from the curing tool  145 . 
     To remove the mandrels  150 ,  155 ,  160 ,  165  from the frame assembly  25   a , the bladder  205  is deflated and removed from the head tube, top tube, and down tube mandrels  150 ,  155 ,  160 . When the bladder  205  is deflated, the flexible head tube, top tube, and down tube mandrels  150 ,  155 ,  160  contract from the cured outer frame wall  130  and the inner wall  135  so that a gap exists between the mandrels  150 ,  155 ,  160  and the walls  130 ,  135 , making it easier to remove the mandrels  150 ,  155 ,  160 . 
     The head tube, top tube, and down tube mandrels  150 ,  155 ,  160  can be removed from the frame assembly  25   a  before or after the cable routing mandrels  165  are removed. The head tube mandrel  150  (or mandrel halves) can be removed via the top or bottom opening in the head tube  30 . With reference to  FIG. 6 , the top tube mandrel  155  is removed by pulling the mandrel  155  rearward out of top tube portion of the frame assembly  25   a . Similarly, the down tube mandrel  160  is removed from the frame assembly  25   a  by pulling the mandrel  160  rearward out of the down tube  45 . As illustrated in  FIG. 5 , the cable routing mandrels  165  are removed from the frame assembly  25   a  by pulling on the exposed mandrel heads  190 . The mandrels  165  slide out of the formed cable passageways  125  in large part due to the low-friction material that comprises the mandrels  165 . 
     The cables can be routed through the cable passageways  125  via the access openings  140  after the frame  25  is formed. By routing the cables  100   a ,  100   b ,  120   b  internally within the down tube  45 , the cables  100   a ,  100   b ,  120   b  are protected from abrasion and wear. In addition, by integrating the cable passageways  125  into the down tube  45  and separating the passageways  125  from the interior of the down tube  45 , the cables  100   a ,  100   b ,  120   b  can be more easily routed within the frame  25  while minimizing noise that could be caused by cable movement during riding. 
     Various features of the invention are set forth in the following claims.