Abstract:
A method for building a bicycle wheel and the wheel. Inserting a threaded end ( 106 ) of a spoke ( 100 ) through a hole ( 126 ) in the rim ( 102 ), through a spacer ( 118 ), and engaging the threaded end ( 106 ) with an internally threaded connector ( 104 ). The rim ( 102 ) and the connector ( 104 ) cooperate to maintain the axis of the threaded end ( 106 ) of each spoke ( 100 ) in a given spoke hole ( 126 ) so that it is skewed relative to the axis of a first portion of each spoke ( 100 ) extending from the hub to the rim ( 102 ). While the connector ( 104 ) is turned to tension the spoke ( 100 ), the spoke ( 100 ) permanently bends at a point ( 128 ) remote from the spoke&#39;s thread end ( 106 ).

Description:
This application claims the benefit of provisional application No. 60/094,512 filed Jul. 29, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to bicycle type wheels and especially to such wheels including tensioned spokes connecting a rim to a hub. More specifically, the invention relates to front and rear, radially and tangentially laced, tensioned spoke wheels comprising a hub, a rim and a plurality of spokes connecting the rim to the hub, and a mechanism for attaching the spokes at the rim to reduce spoke stresses and breakage. 
     2. Description of the Prior Art 
     Spoked wheels, especially for bicycles, are laced generally in one of two spoking patterns. Radially spoked wheels, with spokes extending generally radially outwardly from hub flanges, are used as front wheels for bicycles. Tangentially spoked wheels, with spokes extending tangentially or nearly so, relative to the hub flanges, are used as rear bicycle wheels. In both cases, the longitudinal axis of a spoke deviates from a radial orientation relative to the intersection of the center plane of the wheel and the rotational axis of the wheel. This is illustrated in FIGS. 5 and 6, which are based upon FIGS. 2 and 1, respectively, of U.S. Pat. No. 4,583,787 (“Michelotti”), the disclosure of which is incorporated herein by reference. 
     FIG. 5 illustrates what we will call the centering angle of a spoke, in the context of a rim  10  which has a radius R. In the drawing, the radius R coincides with the center plane of a wheel including the rim  10 , the center plane being perpendicular to the axis of rotation of the wheel and intersecting the center line of the rim. The longitudinal axis, designated SA, of a spoke (not shown) attached to a left hub flange (not shown) deviates from the rim radius R by an angle designated CA for centering angle. In the drawing, the spoke axis SA intersects the rim radius R outside of the rim  10 . Because of this deviation, a spoke connected to the rim  10  and a left hub flange (not shown) exerts a lateral force which is balanced, more or less, depending on the spoking pattern, by an opposite lateral force exerted by a spoke (not shown) connected to the rim  10  and a right hub flange (not shown). These lateral forces keep the rim centered in the wheel center plane and provide essential lateral stability to radially spoked wheels and to tangentially spoked wheels. Thus, the name centering angle. 
     FIG. 6 illustrates what we will call the torsional angle of a spoke, in the context of a rim  12  which has a radius R. In the drawing, the radius R coincides with the center plane of a wheel including the rim  12 , the center plane being perpendicular to the axis of rotation of the wheel and intersecting the center line of the rim  12 . The longitudinal axis, designated SA, of a spoke  14  attached to a right or left hub flange (not shown) deviates from the rim radius R by an angle designated CA for torsional angle. Because of this deviation, which is found in tangentially spoked wheels, primarily used as rear driving wheels, the spoke is operable to transmit a pulling or torsional force from a rotating hub to the rim  12 , tending to cause the rim to rotate. Thus, the name torsional angle. Generally speaking, there is no torsional angle in wheels which are radially spoked. 
     If it were not for the torsional and centering angles of spokes, securing them to a rim would be a fairly simple matter. It is, however, a complicated matter to secure spokes to a rim. This is further complicated because the centering angle and the torsional angle are not constant in bicycle wheels on a moving bicycle. The weight of a rider, forces associated with turning, forces associated with braking and forces associated with acceleration, among other things, can and do cause small but not insignificant changes in these angles and these changes occur very rapidly during cycling. These angle changes cause stresses in spokes, particularly where they are fastened to the rim, typically by internally threaded nipples. Various attempts to deal with these stresses are discussed below. 
     The Michelotti patent discloses a bush which is received in a spoke bore in a rim. The bush is configured with two cylindrical co-axial bodies for receiving the conical head and the cylindrical section of an internally threaded nipple which receives the threaded end of a spoke. The bush is further configured to minimize deviation between the common axes of the cylindrical bodies and the longitudinal axis of the spoke. Apart from difficulties associated with properly orienting the bushes to achieve the desired result, this approach does not begin to account for dynamic changes in the centering angle and the torsional angle. 
     Another prior art method is illustrated in FIG. 2 which shows a rim  20 , in cross-section and a spoke  22  connected to the rim  20 . The rim  20  has a rounded spoke bed indicated at  24  which is raised, as indicated at  26 , adjacent to sidewalls  28  of the rim  20 , and lower in the middle, as indicated at  30 . A spoke bore, indicated at  32 , has an axis which is oriented, so far as possible, to coincide with the longitudinal axis of the spoke  22 , taking into account the centering angle as well as the torsional angle, if any, of the spoke  22 . A nipple  34  is internally threaded and is attached to a threaded end  36  of the spoke  22 . Portions of the bottom end  38  of the nipple  34  engage the rounded rim floor  24  while other portions of the bottom  38  of the nipple  34  do not engage the rim floor  24 . This condition is exacerbated under dynamic conditions when the centering angle and the torsional angle are changing. The resulting stresses tend to concentrate in the unthreaded portion of the spoke  22 , immediately adjacent to the threaded portion  36 . 
     Referring now to FIGS. 3 and 4, an extended nipple  40 , similar to the nipple shown in the Michelotti patent with a head  6 , has a head  42  which is seated on a substantially flat rim floor  44  of a rim  45 . As can be seen in FIG. 4, however, only a small portion of the underside  46  of the head  42  of the nipple  40  seats against the rim floor when it engages a spoke  47  extending through the rim  45 . In this arrangement, the spoke hole, indicated at  48 , is inclined so that its axis coincides generally with the longitudinal axis of the spoke, taking into account the centering angle and, if necessary, the torsional angle. The nipple  40  has a slot, indicated at  49  in FIG. 4, which is engageable by a screwdriver or the like to properly tension the spoke  47 . 
     SUMMARY OF THE INVENTION 
     The present invention is based upon the discovery of an improved method for attaching a threaded end of a spoke to a rim and a wheel made in accordance with the method. According to the method, a rim, preferably one having a substantially flat rim floor, is provided with spoke bores that are oriented so that the axis of the bore coincides or is substantially parallel to a radius of the wheel. The threaded end of the spoke is inserted through the spoke bore, a cylindrical spacer element is positioned around the spoke end and an internally threaded nipple is attached to the threaded portion of the spoke end. According to the method. the spacer height is controlled, relative to the stiffness of the spoke, so that, when the spoke is tightened, the threaded portion and an unthreaded portion adjacent thereto coincide with or are substantially parallel to a radius of the wheel and so that a bend is formed in the spoke, as it is tightened to accommodate centering angle and, if necessary, the torsional angle. The bend is formed in the spoke at a point which is remote from the transition between the threaded portion of the spoke and the adjacent, unthreaded spoke portion. Preferably, the bend is formed at or near a point on the spoke, adjacent to point where the spoke exits the underside of the rim. This arrangement moves stresses of the type described above, away from the transition between the threaded portion of the spoke and the unthreaded portion of the spoke, while providing for a firm, stable support between the underside of the nipple and the spoke floor with good distribution of tensile stresses on the rim floor. 
     Accordingly, it is an object of the present invention to provide a method for connecting a spoke to a rim which will reduce stresses found in prior art wheels adjacent to the intersection of the threaded end portion of the spoke and the adjacent, unthreaded portion of the spoke. 
     It is a further object of the invention to provide a method for securing a spoke to a rim with a nipple so that the underside of the spoke is firmly supported relative to the rim floor. 
     It is a further object of this invention to provide a wheel which resists failure due to bending of the spoke adjacent to the intersection between the threaded end portion of the spoke and the adjacent unthreaded portion. 
     It is yet another object of the invention to provide a wheel in which an end portion of the spoke is oriented so that its longitudinal axis coincides with or is substantially parallel to a radius of the wheel and there is a bend in a portion of the spoke at a point which is remote from the intersection between the threaded portion of the spoke and the adjacent unthreaded portion. 
     It is a primary object of this invention to provide an improved spoked wheel. 
     These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having read this detailed description of the invention including the following description of the preferred embodiment which is illustrated by the various figures of the drawing. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is a view, partially in cross-section, of a portion of a rim section including a spoke and rim connection according to the present invention. 
     FIG. 2 is a view, partially in cross-section, of a rim section showing a prior art spoke and rim connection. 
     FIG. 3 is a cross-sectional view of a rim section showing a prior art spoke and rim connection. 
     FIG. 4 is a cross-sectional view of a rim section showing a prior art spoke and rim connection. 
     FIG. 5 is a modified version of FIG. 2 of the Michelotti patent, illustrating the centering angle of a spoke. 
     FIG. 6 is a modified version of FIG. 1 of the Michelotti patent, illustrating the torsional angle of a spoke. 
     FIG. 7 is a view, partially in cross-section, of a portion of a rim section illustrating further details of a spoke and rim connection according to the present invention. 
     FIG. 8 is a view, partially in cross-section, of a portion of a rim section illustrating a spoke and rim connection, wherein the spoke is a bladed spoke, according to the present invention. 
     FIG. 9 is a view taken along the line  9 — 9  of FIG.  8 . 
     FIG. 10 is a view, partially in cross-section, of a portion of a rim section, including a curved rim floor, showing a spoke and rim connection according to the present invention. 
     FIG. 11 is a view, partially in cross-section, of a portion of a rim section illustrating a spoke and rim connection according to the present invention wherein the threaded portion of the spoke is not radially oriented. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a spoke  100  is shown connected to a rim  102  by a nipple  104 . An end portion  106  of the spoke  100  is threaded and is received in an internally threaded bore, indicated at  108 , in the nipple  104 . The outer surface of the nipple may have four or six sides or flats (not shown) engageable by a wrench, although other torque transmitting configurations may certainly be employed. Preferably, there is a locking feature incorporated in the bore  108  of the nipple  104  which serves to lock the nipple  104  to the spoke  100  so that the nipple will not turn relative to the spoke. This feature in the art is known generally as a locking nut. 
     Adjacent to the threaded portion  106  of the spoke  100 , there is an unthreaded portion  110  of the spoke  100 . The intersection between the threaded portion  106  and the unthreaded portion  110  is indicated by the reference numeral  112 . Generally, wheels are designed so that the intersection  112  is adjacent to an underside  114  of the nipple  104  when the spoke is at final tension. 
     The rim has a substantially flat rim floor, indicated at  116  although it will certainly be appreciated that the floor bed is actually a surface of revolution. However, because radius of the rim floor is relatively large, especially compared to the size of the nipple, the rim floor  116  may be considered substantially flat for present purposes. 
     Between the underside  114  of the nipple  104  and the rim floor  116 , there is a spacer element  118 . It is basically a right cylinder with a flat end  120  which abuts the underside  114  of the nipple and a flat end  122  which abuts the rim floor  116 . The abutment occurs when the spoke  100  is tightened, along with other spokes in the wheel, to produce a finished wheel. These tensions may be quite high, as in the case of a low spoke count wheel having, for example, 16 or so spokes. The spacer  118  has an internal bore, indicated at  124 , which has an axis which is perpendicular to the surfaces  120  and  122 . The bore  124  is slightly larger in diameter than the unthreaded portion  110 of the spoke  100 , so that the spoke is easily received in the bore  124 . Generally speaking, the diameter of the bore  124  should be about one tenth of an inch larger than the diameter of the spoke portion received therein. 
     The unthreaded portion  110  of the spoke  100  extends through the spacer  118  and through a spoke bore, indicated at  126 , through the rim. When the spoke  100  is tightened, as by turning the nipple  104 , the threaded portion  106  and the adjacent unthreaded portion  110  of the spoke  100 , remain substantially straight down to a bend  128  in the spoke, which occurs in the spoke at or near the point where the spoke  100  exits the underside of the rim  102 . The outer portion of the spoke, above the bend  128 , remains substantially straight and coincides with or is substantially parallel to a radius of the rim  102 . The inner portion of the spoke  100 , below the bend  128 , has a longitudinal axis which coincides with the centering angle and, if necessary, the torsional angle of the wheel, as measured from the bend  128 . The height of the spacer  118  is a few millimeters and various heights will work in the method of this invention. The height must be such that, when the spoke is tightened, it will bend at a point coinciding with or adjacent to the bend  128 , remote from the intersection  112  of the threaded portion  106  and the unthreaded portion  112 . Excellent results have been achieved with two spacers having a combined height of 5 millimeters. The spacer height might have to be lower or higher, depending upon the stiffness of the spoke. It will be appreciated that a two piece or multiple piece spacer could be substituted for the single spacer  118 , provided that the pieces have an appropriate combined height. Essentially, the spacer  118  has an upper surface  120  and lower surface  122  which are parallel to each other and a spoke bore  124  having a longitudinal axis which is substantially perpendicular to the surfaces  120  and  122 . The spacer  118  is illustrated as having an outer surface  130  which is substantially cylindrical although it may have other configurations and still perform in accordance with the present invention. 
     It will be appreciated that, when the spoke  100  is attached to the rim  102  in accordance with the method of the present invention, the spoke  100  is forced to bend, as it is tightened at about the point where it exits the spoke bore  126  in the rim. Because the longitudinal axes of the nipple  104 , the spacer  118  and the spoke bore  126  coincide with or are substantially parallel to a radius of the wheel, and the upper and lower surfaces  120  and  122  of the spacer are perpendicular to the axes, the lower surface  122  seats squarely on the rim floor  116 , providing excellent distribution of the tensile forces to the rim floor  116 , all around the spoke bore  126 . The spoke bend  128  accommodates the centering angle and, if necessary, the torsional angle, minimizes stresses in the region of the intersection  112  between the threaded portion of the spoke  106  and the unthreaded portion of the spoke  110 , and dissipates the stresses caused by dynamic changes in the centering and torsional angles. 
     Referring now to FIG. 7, there is illustrated a spoke and rim connection, according to the present invention, for front and rear wheels. A spoke  200  is attached to a carbon fiber rim  202  by a connector comprising an internally threaded nipple  204  and a spacer  205 . It will be appreciated that the connector could be a unitary element rather than two elements as shown in FIG.  7 . The rim  202  has a spoke bed  206  and a spoke bore indicated at  208  extending through the rim. A threaded portion  210  of the spoke  200  is received in the nipple  204  and the threaded portion  210  of the spoke  200  terminates, within the rim  202 , at a point designated  212  and an unthreaded portion  213  extends down to and through the spoke bore  208  and towards a hub flange (not shown) of a hub. A first portion  214  of the spoke  200  extends from a hub (not shown) to the rim  202  and a second, outer portion of the spoke  200  is constituted by the threaded portion  210  and the unthreaded portion  213 . At about a point where the spoke  200  exits the spoke bore, between the first portion  214  and second portion of the spoke  200 , there is a bend  216  in the spoke  200 . The bend  216  is preferably formed in the spoke  200  during the process of building a wheel including the spoke  200  and other spokes, the rim  202  and a wheel hub (not shown). The formation of the bend  216  will be further explained below in the context of building such a wheel. 
     A wheel for a bicycle or other human powered vehicle typically comprises a hub with a pair of opposed hub flanges and spoke openings in the hub flanges for receiving a spoke and seating a head on the spoke adjacent to a J-bend provided at a first end of the spoke. A second end of the spoke is typically threaded and, initially, the spoke is straight from the J-bend to the threaded end. The reader may refer to U.S. Pat. No. 5,445,439, the disclosure of which is incorporated herein by reference, for further details concerning human powered vehicle wheels. In building a wheel, one guides the threaded end of each spoke through its spoke opening in the hub flange until the spoke head engages the hub flange. The threaded end of each spoke is then guided through its spoke opening in a rim and an internally threaded nipple or the like is turned to engage a portion of the threaded portion of the spoke until all spokes are roughly in place. Then, the spokes are tightened towards and to a final design tension and, finally, the wheel is trued by individual adjustment of certain ones of the spokes. There are wheel building machines which automate some or all of these steps. As the spokes are tightened, the spoke is elastically deformed at first, and then plastically deformed so that it takes on a permanent bend where it enters or exits the rim, remote from the threaded portion of the spoke. 
     Referring again to FIG. 7, in the process of building a wheel including, the threaded end of the spoke  200  is threaded through a hole in a hub flange (not shown), through the spoke bore  208 , through the spacer  205  and the nipple  204  is turned onto the threaded portion  210  of the spoke. Co-action between the spoke bed  206  and the connector comprising the nipple  204  and the spacer  205 , causes the threaded portion  210  of the spoke  200  to be aligned radially, i.e., along a radius R of the wheel. The first portion of the spoke, between the hub and the rim, will be skewed relative to the axis of the threaded portion  210 , to account for the centering angle and, if present, the torsional angle. As a consequence, the spoke  200  will not be straight. As the nipple is tightened towards a final design tension, the spoke  200 , will attempt to straighten, tending to cause the spoke to bend, initially, at a point  220  where the spoke exits the nipple  204 . This bending will continue until a portion of the spoke  200  engages a portion of the rim which defines the spoke bore  208  (not shown) at which point the axis of the unthreaded portion  213  will be aligned, as indicated at EB, forming an angle, designated alpha, with respect to the radius R of the wheel. This bending does not exceed the elastic limits of the spoke  200  and no permanent bend is imparted to the spoke adjacent the point  220 . As the spoke is tightened further, the constrained spoke  200  will tend to bend at a point designated  222  to accommodate the skew between the axis EB of the unthreaded portion  213  and the axis SA of the first portion  214  of the spoke. This bending does exceed the elastic limits of the spoke so that the spoke  200  takes on the permanent bend  216  adjacent the point where the spoke  200  exits the rim  202 . The angle beta, between the axis EB of the unthreaded portion  213  and the axis SA of the first portion  214  of the spoke  200 , is larger than the angle alpha. 
     Referring now to FIGS. 8 and 9, another embodiment of the invention will now be described. A bladed spoke  300  is connected to a carbon fiber rim  302 . The spoke corresponds with one that is commercially available as a stock DT New Aero spoke. It is stainless steel and has a J-bend (not shown) at one end, a threaded portion  304  at the opposite end, a round, unthreaded portion  306  and a bladed or flat portion  308 . A first portion of the spoke  300  extends from a hub (not shown) to the rim  302  and corresponds with the bladed portion  308 . A second portion of the spoke  300  comprises the threaded portion  304  and the adjacent, unthreaded portion  306 . 
     Front and rear wheels were produced with the bladed spokes  300 , tubular, carbon fiber rims which are commercially available from Lew Composites of Las Vegas, Nev., and front and rear hubs corresponding with the front and rear hubs used in Rolf (trademark) Vector Pro wheels which are commercially available from Trek Bicycle Company. Sixteen spokes were used on the front and rear wheels and the lacing pattern of the spokes corresponded with the lacing pattern of the corresponding Vector Pro wheels. The threaded ends of the spokes  300  were laced through the spoke holes in the hub flanges and then through spoke bores, indicated at  310 , through spacers  312  and nipples  314  were turned onto the threaded portions  304  of the spokes  300 . Dimensions were controlled so that, as shown in FIG. 9, edges  320  of the bladed portions  308  of the spokes  300  engaged a portion of the wall defining the spoke bore  310 . The distance between the two edges exceeded the diameter of the spoke bore  310  by less than one millimeter. Yet, the engagement between the edges  320  and the wall defining the spoke bore  310  prevented lateral movement of the spoke within the bore  310 . Accordingly, as the spokes were brought up to wheel design tension, between 200 and 400 pounds per spoke, the spokes did not bend at a point  322  between the threaded portion  304  and the unthreaded portion  306 . Instead, the spokes bent at a point  324 , right where the edges  320  engaged the wall defining the spoke bore  310 . 
     The front and rear wheels produced as described above were ridden by a two hundred pound rider for 1200 miles with outstanding performance. The rear wheel was further tested on a drum tester comprising a drum which is smooth except for a portion that is raised so that it is three eighths of an inch off of the drum surface, and a fixture for supporting the wheel with a one hundred and fifty pound load applied at the axle, which is equivalent to having a three hundred pound rider. The drum and wheel are rotated to simulate a road speed of 47 miles per hour. The rear wheel racked up 49 hours on the drum test with no spoke failure. 
     Additional wheels were built according to the present invention from aluminum rims in clincher and tubular styles, but otherwise corresponding with the wheels described above with reference to FIGS. 8 and 9. Referring now to FIG. 10, a clincher rim  400  is illustrated with a bladed or aero type spoke  402  secured to the rim  400 . The rim  400  has a rounded spoke bed  404 . The spoke  402  comprises a first, bladed portion  406  and a second portion comprising an unthreaded portion  408  and a threaded portion  410 . As a wheel is produced including the rim  400 , the threaded end  410  of each spoke is first inserted through a hub flange spoke opening, through a spoke bore indicated at  412  in the rim  400 , through a spacer  414 , and an internally threaded nipple is threaded onto the threaded end  410  of the spoke  402 . Edges (not shown) of the bladed portion  406  of the spoke  402  engage a portion of the wall defining the spoke bore indicated at  412 , preventing bending of the spoke  402  in the unthreaded portion  408 . As the spoke  402  is further tensioned, the spoke elastically deforms at first, and then plastically deforms causing it to take on a permanent bend at a point  418  between the first, bladed portion  406  and the unthreaded portion  408 . A front clincher wheel so produced was tested on the drum tester described above until the rim cracked. The rim was replaced and the wheel was rebuilt with the same spokes. This was repeated six more times until each spoke had racked up  189  hours on the drum tester without a single spoke failure. 
     Referring now to FIG. 11, an aluminum rim  500  and a spoke  502  are illustrated. This wheel corresponds generally with previously described wheels. The rim  500  has a curved spoke bed  504  and a first, bladed portion  506  of the spoke  502  terminates just below the point where the spoke  502  enters the rim. Adjacent to the bladed portion  506 , there is an unthreaded portion  508  and the spoke  502  terminates in a threaded portion  510 . The spoke  502  passes through a spoke bore indicated at  512  in the rim  500 , through a spacer  514  and into an internally threaded nipple  516 . The nipple and the spacer cooperate with the spoke bed  504  so that the axis of the unthreaded portion  508  and axis of the threaded portion  510  of the spoke  502  do not coincide with and are not parallel to a radius of the wheel. As the spoke is tightened, the spoke is deformed elastically, at first, and the deformed plastically causing it to take a permanent bend at the point  518 , between the bladed portion  506  and the unthreaded portion  508 . 
     In sum, the present invention involves a method for producing a wheel from a rim, a hub and a plurality of spokes which are essentially straight wherein, as each spoke is tightened in the wheel, a permanent bend is made in the spoke, at a point remote from an intersection between an outer threaded portion and an adjacent, unthreaded portion. 
     The foregoing description is intended to enable one skilled in the art to practice this invention and constitutes the best mode presently known to the inventor for carrying out the invention. Modifications and adaptations of the invention, as described herein, will undoubtedly occur to those skilled in the art and, although not described herein, may nevertheless fall within the spirit and scope of the invention as defined in the claims.