Patent Document

BACKGROUND OF INVENTION 
   This invention relates to a drive chain and more particularly to a bicycle roller chain that prevents the pin connection from rupturing under lateral forces. 
   It is known in the art to provide a roller chain that has a plurality of interconnected chain links that form a drive element between two gear wheels to drive a bicycle. For example, a French patent, FR2753512, discloses a chain for bicycles, which includes chain links having outer link plates and inner link plates. Each plate has holes for receiving pins that connect the links together. &#39;512 discloses a lightweight drive chain while still providing adequate load bearing capacity. The weight of the chain is lightened in two ways. First, the outer link plate point is provided with an opening disposed in the middle of the outer link plate which also reduces the external contour of the outer link plate. Second, the pin is made hollow. The pin is made from tube stock and is pressed into the holes of the outer link plates and inner link plates. After being pressed into the holes, the pin is riveted to increase its press fit in the outer link plate, resulting in a slight expansion of the hole at the outer edge of the hole in the outer link plate. Such an expansion usually occurs, whether the pin is made from solid stock or tube stock because of the act of riveting it. 
   A problem associated with riveting the pins is that the connection between the pins and the link plates may ruptured under lateral forces that occur when changing from a first gear to a second gear which is not aligned with the first gear. Due to these forces, the riveted end of the pin is pulled through the hole of the outer link plate. Thus, merely riveting the pin in the outer link plate does not prevent the destruction of the roller chain under high operating loads. Therefore, there is a need for a roller chain having a configuration that prevents the end of the pin from being pulled through the hole of the outer link plate. 
   Further, when designing a roller chain to be used with a gear set on the rear axle of the bicycle, it is important that the configuration of the roller chain allows the smallest possible interval between the gears in order to accommodate a maximum number of sprockets on the rear axle. This can be accomplished by having components that do not project over the external surface of the roller chain, which is essentially defined by the outer surface of the outer link plate. One component that usually protrudes beyond the outer surface of the outer link plates is the pin. The pin usually has an edge that projects beyond the external surface of the outer chain link. Further, the edges of the pin may get caught on the toothing of an adjacent gear, especially a larger gear, and may give rise to unintended gear shifts or noises. 
   There is a need for a roller chain that has a configuration that prevents the rupture of the pin connection under lateral forces and has a narrow design to permit a maximum number of chain sprockets on the rear axle of the bicycle. 
   SUMMARY OF INVENTION 
   The present invention provides a roller chain having a connection between the head or end of the pin and the outer link plate that is modified to give an improved interlocking connection. The configuration of the present invention prevents the head of the pin from being pulled through the hole in the outer link plate. This is achieved by having a hole in the outer link plate that has an outward-opening conical shape rather than just a cylindrical shape. Although this hole configuration forms a press fit with the pin at its inward narrowest point, the outward extending contour of the hole provides an increasing clearance in relation to the pin. The pin is riveted and the head of the pin fills the free space defined by the clearance. 
   If round or solid stock is used for the pin, the riveting must be performed by a wobble riveting method. Otherwise, conventional riveting would modify the diameter of the entire pin, resulting in the inner chain links becoming fixed on the pin and would adversely affect the functioning of the roller chain. 
   If tube stock is used to make the pin, a more cost-effective riveting method may be used and in addition the tube stock has a lighter weight. A stamping tool is used to rivet the pin. The stamping tool has two punches which approach the pin axially from both sides and expand the heads of the pin from the inside diameter outward. Each punch has an insertion diameter, an expansion cone, and a calibration surface for determining the length of the pin. The expansion cone may be experimentally adjusted to the contour of the hole to vary the tightness of the press fit of the head of the pin along the funnel-shaped hole. A clearance between the pin and the hole may range from zero to a specific clearance that allows the outer link plates and the pins to form a rectangle under no load and to form a parallelogram under load. 
   As stated above, conventional roller chains react to lateral forces by the inner chain link being deflected onto their pins which produces a wear-promoting edge load. This occurs for the first time when changing the first gear of a nonaligning gear pair and for a second time when running on to the second gear on the other side of the pin. The present invention eliminates this problem by providing the previously described parallelogram which prevents the edge load and thus reduces wear. 
   In another embodiment of the present invention, a hole in the outer link plate has a cylindrical section and a tapered section. The tapered section is closest to the outer surface of the outer link plate. The tapered section has a length approximately equal to one third of a thickness of the outer link plate. Preferably, when the pin is made from tube stock, the stamping tool has an expansion cone that produces a tapered angle between 55° and 65°. 
   Alternatively, a tubular pin may have a solid middle section and hollow sections at the heads of the pin may be used. The length of the hollow sections are equal to the length of the tapered section in the hole of the outer link plate. The deformation of the head of the pins made from tube stock in order to produce a reliable contact with tapered section of the hole in the outer link plate may be achieved by a combination stamping and wobble riveting method. In this case punches are used which have an expansion cone with a smaller angle, but which after stamping of the pin are then set into a wobbling motion, in order to produce the required tapered angle of 55° to 65° at the head of the pin. 
   In another embodiment of the present invention, the pin may be fixed in the outer link plate by stamping the head of the pin transversely over a face of the head of the pin, resulting in two opposing embossings produced by surface contact pressure on the peripheral area of the tapered section of the hole in the outer link plate. With this configuration, the pin is able to perform a slight swiveling movement in relation to the outer link plate about the connecting axis of the two contact surfaces. The swiveling movement prevents the low-wear operation of the drive chain in the case of nonaligning chain sprockets. Alternatively, the head of the pin may be expanded irregularly using non-round punches, making it also possible to produce two opposing contact embossings between the head of the pin and the outer link plate. In the same way that two contact embossings may be produced, it is possible to produce three or four symmetrically arranged contact embossings by surface contact pressure. 
   Since the pins of the present invention have a greater thickness than the prior art it is no longer possible to press a pin out of the roller chain for the purpose of opening and/or dismantling the roller chain. If the roller chain is to be opened, at least two heads of two pins must be ground off in order to expose the two inner chain links needed for the connection. Thus to solve this problem, a closing link disclosed in the U.S. Pat. No. 5,362,282, entitled “MASTER CHAIN LINK” may used in combination with the roller chain of the present invention. 
   The closing link includes first and second elements. Each of the elements has a closing link plate and a closing pin which are pressed together to form a L-shaped element. When two inner chain links are connected together to close the roller chain, the closing pin of the first L-shaped element is inserted into the first inner chain link and the closing pin of the second L-shaped element is inserted into the second inner chain link from the opposite direction and at the same time pushed through openings in the respective closing link plates situated opposite. 
   Alternatively, the closing link may be constructed according to the French patent, FR2652627 (Reg. Nat. 89 12752), entitled “ACCESSOIRE DE JONCTION POUR CHAINE DE TRANSMISSION.” The closing link includes a first element and a second element. An outer chain link is connected to an inner chain link by pressing the first element and the second element into one another. The first and second elements occupy the same space as a pin. To make the edge of the closing link flush with the outer chain link, the first and second elements have flat heads that fit within indents disposed in an outer surface of the outer chain link. With this configuration, no harmful edges are produced that might adversely affect the gear shift quality of the roller chain. 
   In a specific embodiment of the present invention, the configuration of the roller chain is narrowed by providing the outer link plates with a middle section that has an indent on a side facing the inner link plate. The indent lies in a plane perpendicular to the longitudinal direction of the chain. Also, since a gear shift almost always occurs due to the outer link plate catching teeth of the adjacent gear, this works all the better the further outward the inside of the outer link plate is at the point of contact. 
   In a specific embodiment of the present invention, the pin has a stop located a distance from a face of the head of the pin. The distance equals the thickness of the outer link plate. The area of the pin in the outer link plate has a smaller diameter than a diameter of an area of the pin in the inner link plate and a hole of the inner link plate. This configuration facilitates the assembly of the roller chain in mass production. 
   The object of the present invention is to provide a roller chain that affords increased security against the parting of the connection between the outer link plates and pins under increased loading by lateral forces and has a closing link that allows the roller chain to be opened and closed as often as required. Another object of the present invention is to provide a narrow roller chain that permits a maximum number of chain sprockets on the rear axle of the bicycle. 
   These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention take together with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     In the drawings: 
       FIG. 1  is a partial view of a prior art roller chain; 
       FIG. 2  is a partial view of the prior art roller chain of  FIG. 1  rotated 90 degrees; 
       FIG. 3  is a cross-sectional view of a roller chain in accordance with a specific embodiment of the present invention 
       FIG. 4  is a diagram of a closing link between two inner chain links in accordance with a specific embodiment of the present invention; 
       FIG. 5  is a perspective view of the closing link of  FIG. 4 ; 
       FIG. 6  is a cross-sectional view of a stamping tool being inserted into a pin to expand the ends of the pin; 
       FIG. 7  is a side view of the roller chain on two gears that are not align with one another; 
       FIG. 8  is a partial cross-sectional view of the outer link plate in accordance with a specific embodiment of the present invention; 
       FIG. 9  is a partial cross-sectional view of a pin inserted into the chain links in accordance with a specific embodiment of the present invention; 
       FIG. 10  is a cross-sectional view of a pin having a solid middle section in accordance with a specific embodiment of the present invention; 
       FIG. 11  is a partial cross-sectional view of a hole of the outer link plate in accordance with a specific embodiment of the present invention; 
       FIG. 12  is a top view of a pin having an embossment running transversely over its end face that is disposed in the hole of  FIG. 11 ; 
       FIG. 13  is a partial cross-sectional view of a hole of the outer link plate in accordance with a specific embodiment of the present invention; 
       FIG. 14  is a top view of a pin with a cruciform embossment that is disposed in the hole of  FIG. 13 ; 
       FIG. 15  is a side view of a outer link plate having a narrow middle section facing an inner link plate; 
       FIG. 16  is a side view of a closing link in accordance with a specific embodiment of the present invention; and 
       FIG. 17  is a partial side view of a pin having a stop and a reduced diameter for receiving an outer link plate. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2  of the drawings, numeral  10  generally indicates a prior art roller chain for a bicycle. The chain  10  generally includes outer chain links  12  and inner chain links  14  which are pivotally connected by tubular pins  16 ,  18 . The outer chain links  12  have outer link plates  20  and the inner chain links have inner link plates  22 . Rollers  24  may interact with teeth of gears  26 ,  28 , shown in  FIG. 7 , and may be arranged around the pins  16 ,  18 . The plates  20 ,  22  are provided with holes  30  at their circular ends  32 . The pins  16 ,  18  extend through and project out of the holes  30 . The pins  16 ,  18  are externally riveted at their ends  34 ,  36  during the assembly of the roller chain  10 . While the pin  16  is made of round stock, pin  18  is made of tube stock, as provided in the roller chain  10  in  FIG. 2 . A narrow middle part  38  which determines the axial position of the roller chain  10  on the teeth of the gears  26 ,  28 , extends between the two circular ends  32  in each of the outer link plates  20  and the inner link plates  22 . 
     FIG. 3  illustrates a partial cross section of a roller chain  40  in accordance with a specific embodiment of the present invention. The chain  40  includes outer link plates  42  and inner link plates  44 . A tubular pin  46  connects the links together. The pin  46  is made of tube stock. A roller  48  is arranged around the pin  46 . The inner and outer link plates have centrally located holes  50 ,  52 , respectively, for receiving the pin  46 . The pin  46  is enclosed by a large bearing surface of the holes  50  of the inner link plates  44  and the rollers  48 . The large bearing surface is a result of bends  54  in the inner link plates  44 . The rollers  48  are supported on the bends  54 . The holes  52  of the outer link plates  42  have a contour  56  which opens outward in a conical or funnel shape. A clearance  58  is formed between the holes  52  and heads  60  of the pin. The clearance  58  increases in an outward direction. The heads  60  of the pin are wider than the inside diameter of the pin  46 . However, the heads  60  are just wide enough to allow the clearance  58  to equal a value in the micron range, in order to obtain a restricted mobility of a press-fit connection. 
   Referring to  FIG. 6 , the heads  60  of the pin  46  are deformed by a control press-fit using a stamping tool  62  to produce an interlocking fit with the contour  56 . The stamping tool  62  may be fitted into a chain riveting machine. The stamping tool  62  includes two punches  64 . Each punch  64  has a specific insertion diameter  66  that allows it be initially inserted into the hollow pin  46 . Each punch  64  also has an expansion cone  68  for expanding the heads  60  of the pin  46 . The expansion cone  68  is adjacent the insertion diameter  66 . Further, each punch  64  has a calibration surface  70  for determining the length of the pin  46  and for making the heads  60  conform to the contour  56  of the hole  52  in the outer link plates  42 . In operation, the punches  64  are inserted into the hollow heads  60  of the pins  46 , then by a control press-fit the expansion cone  68  widens the heads  60  and at end of the process the length and shape of the heads  60  are calibrated by the calibration surface  70 . 
   Referring now to  FIGS. 4 and 5 , a closing link  72  may be used to close the roller chain  40 . The closing link  72  is designed in accordance with U.S. Pat. No. 5,362,282. The two inner link plates  44  being situated opposite one another for this purpose. The closing link  72  includes identical two parts  74 ,  76 . Each part  74 ,  76  includes a closing pin  78  and a closing link plate  80 . The first part  74  is connected to the first inner chain link and the second part  76  is connected to the second inner chain link. The closing pins  78  have first and second heads  82 ,  84 . The heads  82 ,  84  of the closing pins  78  are formed by undercutting. The closing link plates  80  have apertures  86 . The apertures  86  have a narrow curvilinear portion  88  which is narrower than the first head  82  to prevent the first head  82  from passing therethrough. The apertures  86  also have a wide curvilinear portion  90  which is wider than the first head  82  to prevent the first head  82  from passing therethrough. To assemble the closing link  72 , the first heads  82  of the pins  78  are inserted into the wide curvilinear portion  90  of the aperture and than slide into the narrow curvilinear portion  88 . The apertures  86  have embossed locks in which the heads  82  of the pins are detachably anchored. 
   Alternatively, a closing link  92  illustrated in  FIG. 16  may used to assembly the roller chain  40 . The closing link  92  is designed in accordance with French patent, FR2652627 (Reg. Nat. 89 12752). The closing link  92  includes first and second elements  94 ,  96  which are pressed into one another so as to occupy the same space as the pin  46 . To produce a flush edge with the outer link plates  42 , the first and second elements  94 ,  96  may have flat heads  98  which are inserted into indents  100  in the outer link plates  42 . 
   Referring now to  FIG. 7 , the roller chain  40  follows a curved path when it forms a drive with gears  20  and  21  that do not align with one another. In this instance, the chain links are twisted in the shape of a parallelogram because of the built-in clearance between the outer link plates and the pins. Mobility between the pins and the outer link plates is possible even where the clearance approximates to zero. 
     FIG. 8  illustrates another embodiment of the present invention, a hole  102  in the outer link plate  42  does not have a contour as shown in  FIG. 3 , but has a cylindrical section  104  and a tapered section  106  over a specific length  108 . The length  108  equals a third of a thickness  110  of the outside link plate  42 . The tapered section  106  preferably has an angle between 40° to 60° in order to produce an effective connection with the head  60  of the pin  46 . 
     FIG. 9  illustrates another embodiment, the pin  46  may be pressed in and riveted into the hole of the outer link plate  42 . While the pin  46  is being pressed into the hole, the pin  46  is embossed with a tapered angle  112 . The tapered angle  112  falls within the range of 55° to 65° to ensure a force-closed contact with the tapered section of the outer link plate. In this embodiment, the faces of the pin heads are modified to have spherically domes inclines. The inclines do not alter the gear shift quality provided that no edge is produced on the external contour of the roller chain. 
     FIG. 10  illustrates an alternative embodiment of the pin  46 . Pin  114  has a solid middle section  116  and depressions  118  at the heads  120  of the pin  114 . Preferably, the heads  120  only have a length  122  equal to the thickness of the outer link plate  42 . As a result, the pin  114  can be processed like a typical pin  46  as shown in  FIG. 1  made from tube stock. An advantage of this configuration is that the pin  114  is not subject to plastic deformation in the middle area of the solid cross section. No bulging occurs in the middle section  116  as a result of the stamping forces acting on the heads  120  of the pin  114 . 
     FIGS. 11-15  illustrate variations of the pin  46  pressed and riveted into the hole of the outer link plate. In  FIG. 12 , the head of pin  126  is riveted by an embossment  128  running transversely over a face  130  of the head. The riveting of the pin  126  produces two opposing contact embossings  132  on the tapered section  106  of the hole  102 , see  FIG. 11 . In  FIG. 14 , the head of pin  134  is riveted by a cruciform embossment  136  which results in four contact embossing  138  on the tapered section  106  of the hole  102 . This configuration prevents slight swivel movements in a drive over non-aligning gears  21 ,  22 . The strength achieved is similar to those in all-round riveting. 
   Referring now to  FIG. 15 , an outer link plate  140  has a middle section  142  with a reduced thickness or indent  144  on a side facing the inner link plate  44 . The indent  144  lies in a plane  146  perpendicular to a longitudinal direction of the chain. The indent  144  extends transversely over the area of its narrow middle part  142 , in order to achieve or improve the function of the narrow roller chain in the gear shift process. It also helps to improve the function, if the reduced thickness  144  runs over the entire area between the inner link plate  44  and along the plane  146  transversely to the longitudinal direction of the roller chain. 
     FIG. 17  illustrates a pin  148  which has a stop  150  located at a distance  152  from a face of the head of the pin which is an assembly aid for the roller chain. The distance  152  equals to the thickness of the outer link plate  42 . The stop  150  separates an outer reduced diameter  154  from the actual normal diameter of the conventional pins  46 . When advancing the outer link plates  42  in the automatic assembly machine, the outer link plate  42  reaches its predetermined position when it encounters the stop  150 , thereby allowing a measuring sequence to be dispensed with and facilitating the stretching process. 
   While this invention has been described by reference to several preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.

Technology Category: 7