BACKGROUND OF THE INVENTION Bicycle riding constitutes a major form of non-motorized transportation as well as a common recreational pass time. Bicycle performance is a constant concern for those within the bicycle trade who sell and design bicycles, and to those purchasing bicycles. One bicycle feature affecting performance is the chain tensioner. Chain tensioners are used to obtain the proper tension on the chain and thus maximize the bicycle rider's pedaling efficiency, reduce the bicycle's rear wheel wobble, and when appropriate, make more convenient the removal of the rear wheel from, and re-assembly onto, the bicycle.

Chain tensioners are usually positioned near the intersection of the rear ends of the chain and seat stays. Presently available chain tensioners typically include several components that can be difficult to adjust, require special mounting, or are made up of several components that are complicated and likely to break or become mis- aligne. In addition, some chain tensioners do not allow the rear wheel to be removed and replaced without re-adjusting the chain tensioner.

It is with the above-referenced problems in mind that the bolt-on chain tensioner of the present invention was developed.

BRIEF SUMMARY OF THE INVENTION It is the object of the present invention to provide a simple easy to use chain tensioner which allows a user to adjust the chain tension on a bicycle.

It is another object of the present invention to provide a chain tensioner which allows a user to remove and replace a bicycle rear wheel while maintaining a pre-set chain tension.

Typically, a bicycle has a seat stay, chain stay and drop-out on either side of the rear wheel. Each drop-out defines a slot for receiving an end of the bicycle's rear axle. The bolt-on chain tensioner is mounted on the drop-out adjacent to the rear axle and is comprised of a tensioner bolt, a boss with a threaded bore, a lock-nut, and an axle- nut.

The boss, which is generally a narrow rectangular shaped box, has a flat base, curved sides, and a convex top. The flat base of the boss rests against the drop-out and extends outwardly away from the drop-out. The boss defines two apertures which allow it to be attached to the drop-out through two corresponding apertures formed in the drop-out. The apertures can be flush or counter-sunk with the top of the boss. A threaded bore is formed in the boss which is transverse to the bolt apertures. The bore receives the tensioner bolt.

The tensioner bolt is a threaded bolt having a head shaped so as to facilitate turning, and a shank of suitable length so that it will be received by the boss, and interact with the axle-nut when the rear axle is in its most rearward position in the drop-out slot.

The axle-nut is placed on either end of the rear axle. It has a hexagonal top portion and a cylindrical bottom portion that are fixed together so as not to turn independently from each other. The hexagonal top portion of the axle-nut is a slightly larger diameter than the cylindrical bottom portion of the axle-nut. A threaded bore extends axially through the top and bottom portions of the axle-nut and acts to receive the rear axle. The cylindrical bottom portion forms an engagement surface against which the tensioner bolt rests.

Alternatively, the axle-nut may include a hexagonal top portion and a cylindrical bottom portion. The cylindrical bottom portion has a larger diameter than the top portion. A threaded bore extends axially through the hexagonal top portion of the axle-nut and an unthreaded bore extends through the bottom portion of the axle-nut. The top and bottom bores act together to receive the rear axle. The hexagonal top portion allows the axle-nut to be turned onto the rear axle, while the cylindrical bottom portion forms an engagement surface against which the tensioner bolt rests. The two portions are rotationally engaged. A collar extends axially from the top hexagonal portion through an aperture in the cylindrical bottom portion. A flange extends radially outwardly from the collar to contact a flange extending radially inwardly from the cylindrical bottom portion. The collar with radially inwardly extended flange of the top portion is in rotational engagement with the flange of the bottom portion. The rim of the bottom portion has serrations.

The lock-nut has an internally threaded bore for being received on the threaded shank of the tensioner bolt. The lock-nut has an external surface which facilitates it being turned along the length of the tensioner bolt.

The positioning of the rear axle within the drop-out slot is responsible for creating the tension in the chain. In order to move the axle within the drop-out slot and thus create tension, the present invention operates as follows: the boss is mounted on the drop-out adjacent to and in line with the slot. The tensioner bolt is positioned through the bore in the boss so that the shank end of the tensioner bolt engages the cylindrical bottom portion of the axle-nut. The lock-nut is positioned on the tensioner bolt on either side of the boss so as to act as a jam-nut when tightened against the boss. To adjust the chain tension the axle-and lock-nuts (on both sides of rear wheel) are

loosened and the tensioner bolt adjusted. The axle and lock-nuts are then re-tightened to secure the rear axle position and thus secure the tension in the chain.

Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of a preferred embodiment taken in conjunction with the drawings and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of the bolt-on chain tensioner mounted on the drop-out of a conventional bicycle.

Fig. 2 is a perspective exploded view of the bolt-on chain tensioner of the present invention.

Fig. 3 is a perspective exploded view of the alternative embodiment of the bolt-on chain tensioner of the present invention.

Fig. 4 is a side view of the bolt-on chain tensioner in-line with the drop-out slot.

Fig. 5 is a section taken along line 6-6 of Fig. 4 of the components of the bolt-on chain tensioner.

Fig. 6 is a side view similar to Fig. 4, showing an alternative embodiment of the boss and axle-nut.

Fig. 7 is a section taken along line 8-8 of Fig. 6 of the components of the bolt-on chain tensioner, where the axle is in a forward position in the drop-out slot relative to the boss.

Fig. 8 is a section similar to that of Fig. 7, where the axle is in a rearward position in the drop-out slot relative to the boss.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, a bicycle 20 incorporating the present invention is shown. The bicycle has a front 22 and rear wheel 24, handlebars 26, a seat 28, and a frame 30 including a rear triangle 32 defined by a chain stay 34, a seat tube 36, and a seat stay 38. The seat stay 38 and chain stay 34 are both attached at their forward ends to the top 40 and bottom 42 of the seat tube 36, respectively, in a known manner. The rear ends of the seat stay 38 and chain stay 34 are both attached to a drop-out 44, also in a known manner. The bolt- on chain tensioner 46 of the present invention acts in coordination with the drop-out 44.

The conventional bicycle 20 has a seat stay 38, chain stay 34 and drop-out 44 on either side of the rear wheel 24 (see Fig. 2). While there are two drop-outs 44 on each bicycle 20, the structure and operation of the bolt-on chain tensioner 46 is described herein with respect to only one drop-out 44. The structure and operation of the other bolt-on chain tensioner 46 is identical to that described herein.

The bicycle drop-out 44 typically defines a slot 48 for receiving an end of an axle 50 of the rear wheel 24 (see Fig. 2). The rear wheel axle 114 typically has a gear set 52 mounted on one end (see Fig. 4).

The gear set 52 is made up of a plurality of different gears, as is well known. The rear axle 114 is operably connected to the front chain ring 62 by a chain 54 positioned around the front chain ring 62 and extending rearwardly to and around one of the gears on the gear set 52. To propel the bicycle 20, crank arms 56 with suitable pedals 58 are attached to the front chain ring 62. The bicycle 20 can include a derailleur 60 (Fig. 5) to move the chain 54 on the front chain ring 62 and/or rear gear set 52 so as to allow the user to change gears, as is well known. The front chain ring 62, crank arms 56 and pedals 58 are rotationally mounted to a bottom bracket 64.

In order to adequately tension the chain 54 extending between the front chain ring 62 and the gear set 52, the bolt-on chain tensioner 46 of the present invention is used to allow the user the ability to adjust the forward and rearward position of the rear axle 114 in the slot 48 formed in the drop-out 44. The chain 54 is tensioned by moving the axle 114 rearwardly in the slot 48, and de-tensioned by moving the axle 114 forwardly in the slot 48.

Fig. 2 is an exploded view of the bolt-on chain tensioner 46 positioned on either side of the rear wheel 24. The drop-out 44 is typically plate-like in shape and is positioned at the intersection of the rear ends of the seat stay 38 and the chain stay 34. The seat stay 38 is attached, such as by welding, to a top-forward region of the drop-out 66. The chain stay is attached, such as by welding, to a bottom forward region of the drop-out 68. The drop-out 44 typically has an elongated slot 48, preferably positioned in the middle-back region of the plate. The slot 48 typically defines a closed front end 70 and a rear open end 72, and is substantially parallel to the ground (horizontal). It is envisioned that the slot 48 does not necessarily have to be horizontal to the ground or positioned in the middle-back region, rather it can be positioned differently if desired.

Both of the opposing ends of the rear wheel axle 50 are received in drop-out slots 48, and can move forwardly and rearwardly in the slots 48 respectively. Each drop-out 44 includes a space adjacent the slot with two apertures 74 formed therein to mount a boss 76, as is described in more detail below.

The drop-out 44 can alternatively be attached to the seat stay 38 and chain stay 34 in different positions as long as it includes the required structure to allow the movement of the axle 114 in the slot 48.

Still referring to Fig. 2, the four basic components of the bolt-on chain tensioner 46 are shown: a tensioner bolt 78, a boss 76 with a threaded bore 80, a lock-nut 82, and an axle-nut 84. The components can be made out of a variety of materials, such as steel or aluminum, as long as the material facilitates the device's use.

The boss 76 has a general narrow rectangular box shape with a flat base 86, curved sides 88, and a convex top 90. The boss 76 defines a threaded bore 80 extending though the narrow dimension of the boss 76. The flat base 86 of the boss rests against the drop-out 44 and extends outwardly away from the drop-out 44. The boss 76 defines apertures 92 therethrough, one on either end, to allow the boss 76 to be attached to the drop-out 44, such as being bolted through the two corresponding apertures 74 found in the drop-out. The threaded bore 80 is formed transversely to the bolt apertures 92 for receiving the tensioner bolt 78. The exterior of the boss 76 is smooth and may be painted to match the color of the bicycle's drop-out 44. The internal diameter of the boss's threaded bore 80 operatively matches the diameter of the tensioner bolt 78.

To attach the boss 76 to the drop-out 44, bolts 94 are positioned on the side of the drop-out 44 opposite the boss 76, and the bolts 94 extend through the apertures 74 in the drop-out 44 and into threaded apertures 92 formed in the boss 76.

The tensioner bolt 78 is a threaded bolt having a typical hex- head or an Allen-wrench-receiving head, or other suitable shape 96.

The head of the tensioner bolt is preferably shaped so that the user can grip it and turn it with either his or her hand, or by using a conventional tool, such as an Allen wrench. It is envisioned that the tensioner bolt shank 98 diameter and length will be such that it will be received by the boss 76, and be of a length that it can interact with the

axle-nut 84 when the axle 114 is in its most rearward position in the drop-out slot 48 (see Fig. 9), as described below. The tensioner bolt 78 is preferably an M6 x 1.0 long x 45L. The end of the tensioner bolt shank is flat 100. However, the present invention does envision that the shank end could be shaped in any manner that facilitates an effective interaction between the axle-nut and the tensioner bolt.

Also shown in Fig. 2 is the axle-nut 84. The axle-nut 84 has a hexagonal top portion 102 and a cylindrical bottom portion 104. The cylindrical bottom portion 104 has a slightly smaller diameter than the effective diameter of the hexagonal top portion 102. The top portion of the axle-nut can be of any shape desired, preferably one that is able to be tightened by a tool. A threaded bore 106 extends axially through the top and bottom portions of the axle-nut and acts to receive the bicycle axle 114. One axle-nut 84 is placed on either end of the axle 114. The hexagonal top portion 102 allows the axle-nut 84 to be turned onto the threaded axle end 50. The sidewall 108 of the cylindrical bottom portion 104 forms an engagement surface against which the flat end of the tensioner bolt shank 100 rests. It is also envisioned that the bottom portion of the axle-nut 104 can have any shape that can facilitate the interaction between the tensioner bolt 78 and the axle-nut 84. An example is a bottom portion with either multiple flat sides, or with a narrow groove defined throughout its circumference. The bottom portion of the axle-nut 104 is fixed to the top portion 102 and does not turn independently therefrom. A washer 110 can be used when securing the axle-nut 84 onto the axle 114, with the washer 110 being positioned between the bottom portion of the axle-nut 104 and the drop-out 44. The axle-nut 84 is tightened against the drop-out 44 to fix the axle 50 in place within the drop-out slot 48.

Fig. 2 also shows a lock-nut 82. The lock-nut 82 has an internally threaded bore 112 for being received on the threaded shank

98 of the tensioner bolt 78. The external surface of the lock-nut 82 is knurled, textured, defines protrusions, or has a hexagonal shape to allow it to be turned along the length of the tensioner bolt 78. The lock- nut 82 is preferably threaded onto the shank of the tensioner bolt 98 prior to the tensioner bolt 78 being threaded through the boss 76. The tensioner bolt 78, containing the lock-nut 82, is next threaded through the bore formed in the boss 80, with the free end of the bolt directed toward the slot 48, and the head of the tensioner bolt 96 directed forwardly of the boss 76 (see Figs. 4-5). It is also envisioned that the lock-nut 82 could alternatively be threaded onto the tensioner bolt 78 after the bolt has been received by the boss 76. The tensioner bolt 78 can be moved with respect to the boss 76 linearly in line with the slot 48, both forwardly and rearwardly. The tensioner bolt 78 is fixed in position by the lock-nut 82, which acts as a jam-nut when tightened against the boss 76.

In operation, as shown in Figs. 4 and 5, the boss 76 of the bolt- on chain tensioner 46 is mounted on the drop-out 44 adjacent and in line to the slot 48. The slot 48 is typically created with the closed end 70 positioned forwardly, so that the boss 76 is attached to the drop-out 44 near the closed end 70. The axle-nut 84 is positioned over the axle- end 50 and positioned near or in engagement with the drop-out 44.

The tensioner bolt 78 is positioned through the bore in the boss 80 so that the end of the tensioner bolt 100 engages the lower portion of the axle-nut 104. The lock-nut 82 is positioned on the tensioner bolt 78 so as to act as a jam-nut when tightened against the boss 76.

Fig. 5 represents a cross-section through line 6-6 of Fig. 4 showing the bolt-on chain tensioner 46 positioned on either side of the rear wheel axle 114. The tensioner bolt 78 on each side of the bicycle axle 114 is shown threaded through the lock-nut 82 and boss 76, and engaged with the axle-nut 84. The lock-nut 82 is positioned so as to fix

the tensioner bolt 78 in position, while the axle-nut 84 is tightened down against the drop-out 44 so as to fix the axle 114 in position in the drop-out slot 48.

A second embodiment of the boss 116 is shown in Fig. 3. Like the previous embodiment, this boss 116 rests against the drop-out 44 on its flat base 120, has the same general shape, and extends away from the drop-out 44 to define a threaded bore 122 formed transversely to the bolt apertures 124. The bore 122 receives the tensioner bolt 78.

However, unlike the previous embodiment of the boss 76, this embodiment includes counter-sunk apertures 124 on the boss's top side 126, with the apertures 124 extending through the boss 116. Bolts 94 enter the apertures 124 formed in the boss 116 from the outside of the boss 116 and thread through the boss 116 and into the threaded apertures 74 formed in the drop-out to secure the boss to the drop-out.

The axle-nut 128 shown in Fig. 3 includes a hexagonal top portion 130 and a cylindrical bottom portion 132. The bottom portion 132 has a larger diameter than the effective diameter of the top portion 130. A threaded bore 134 extends axially through the top portion of the axle-nut 128, and an unthreaded bore 136 extends through the bottom portion 132 of the axle-nut 128, the bores acting together for receiving the axle 114. The axle 114 is threadedly received in the top portion 130 and is freely received in the bottom portion 132. The hexagonal top portion 130 allows the axle-nut 128 to be turned onto the threaded axle end 50. The sidewalls 138 of the cylindrical bottom portion 132 form a consistent surface against which the tensioner bolt 78 engages. As was discussed in the previous embodiment, the bottom portion of the axle-nut 132 can have any shape that can facilitate the interaction between the tensioner bolt 78 and the axle-nut 128. The bottom portion 132 is preferably 23 mm. in diameter and 10 mm. long.

The cylindrical bottom portion 132 of the axle-nut 128 is rotationally

attached to the top portion 130 and turns independently therefrom.

Because the top 130 and bottom 132 portions of the axle-nut 128 turn independently of one another, a separate washer is not needed to effectively tighten the axle-nut 128 on the axle end 50 to the drop-out 44.

Fig 7 shows the structure for attaching the top hexagonal portion 130 to the bottom cylindrical portion 132 of the axle-nut 128. The bottom portion 132 has a cylindrical shape with opposing open ends. A radially inwardly extending flange 140 defines an aperture in the first end, and the end edge (rim) 142 of the cylindrical wall defines the aperture in the second end. A collar 144 extends axially from the top hexagonal portion 130 through the aperture in the first end of the bottom portion and a flange 146 extends radially outwardly from the collar 144 to retain the collar 144, and hence the top portion 130, in rotational engagement with the bottom portion 132. The rim of the bottom portion 142 defines serrations 148 (saw-teeth) directed to resist counter-clockwise rotation (loosening) of the bottom portion 132 when engaged with the drop-out 44.

As discussed in the previous embodiment the lock-nut 82 is positioned on the tensioner bolt 78 such that when tightened against the boss 116 it acts as a jam-nut and secures the alignment and place of the tensioner bolt 78 in relation to the boss 116.

Fig. 6 shows the alternative embodiment of the boss 116 and axle-nut 128 as part of the bolt-on chain tensioner 46 mounted on the drop-out 44 adjacent to the rear wheel axle 114. The specially adapted axle-nut 128 is positioned over the axle-end 50 and positioned near or in engagement with the drop-out 44. The tensioner bolt 78 is positioned through the bore in the boss 122 so that the end of the tensioner bolt 100 engages the larger cylindrical portion 132 of the

axle-nut 128. As shown in the previous embodiment the lock-nut 82 is positioned on the tensioner bolt 78 so as to act as a jam-nut when tightened against the boss 116.

The positioning of the rear axle 114 within the drop-out slot 48 is responsible for creating the chain tension in the bicycle 20, with the specially adapted axle-nut 128 holding the rear wheel axle 114 in place. When the axle-nut 128 is loosened there are two forces acting on the rear wheel axle 114. First, the tensioner bolt 78 abuts the adapted axle-nut 128 which limits the forward movement of the axle 114 in the slot 48; and second, the chain 54 extends around the gear set 52 in the back and the chain ring 62 in the front which thus limits the rearward movement of the axle 114 in the slot 48.

Therefore, in order to overcome these two competing forces to alter the chain tension, the user loosens the axle-nut 128 to allow the rear wheel axle 114 to move in the drop-out slot 48 (note the movement restrictions discussed above) and the tensioner bolt 78 is adjusted accordingly. The axle 114 and lock-nuts 82 are then re-tightened to secure the position of the rear wheel axle 114. Note that this procedure is performed on both sides of the axle 114 to insure that the rear wheel 24 is properly aligned in the drop-out 44. Figs. 7 and 8 illustrate the outcome of the procedure. Fig. 7 shows the rear wheel axle 114 in a forward position relative to the attached boss 116, whereas Fig. 8 shows the rear wheel axle 114 in a rearward position relative to the attached boss 116.

The instant invention allows the user to precisely control the adjustment of the chain tension with a simple, easy to use mechanism that is integral with the drop-out 44. In addition, the device allows the rear wheel 24 of the bicycle 20 to be entirely removed and be replaced into the same position while maintaining the pre-set chain tension.

Finally, the tensioner bolt 78 can be calibrated, such as by calibrated markings on the tensioner bolt 78, to help make the settings on either side of the axle 114 consistent with one another. The markings can be in the form of different colors or incremental etchings on the tensioner bolt 114.

A presently preferred embodiment of the present invention and many of its improvements have been described with a degree of particularity. It should be understood that this description has been made by way of preferred example, and that the invention is defined by the scope of the following claims.