Patent Description:
Drive chains used for vehicles like bicycles are formed of alternating links. A first link has a narrow opening. The adjacent second links are wider. As may be seen best in <FIG>, bicycle drive chains may be made from outer links <NUM> and inner links <NUM>. In general, the length <NUM> of each link is about the same. However, the outer links <NUM> and the inner links <NUM> differ in width. The outer link <NUM> may have a width <NUM> wider than the width <NUM> of the inner link <NUM>. It will be understood by a person having ordinary skill in the art that in a conventional bicycle drive chain, the series of alternating outer links <NUM> and inner links <NUM> alternate for whatever length of drive chain is deemed desirable. The chain as a whole may be referred to as the chain <NUM>.

A conventional chain ring is shown in <FIG>. The chain ring <NUM> includes a plurality of teeth <NUM> of substantially similar size and shape. The use of teeth of substantially similar size and shape may allow for gaps between an outer surface <NUM> of a tooth <NUM> and a first inner lateral surface <NUM> or a second inner lateral surface <NUM> of an outer link <NUM> of a drive chain (see <FIG>). In many conventional applications, these gaps may not drastically hinder performance, but may increase the risk of chain disengagement.

In the past, some manufacturers have attempted to create chains that have alternating teeth. These alternating teeth have been configured to correspond in size and shape more closely to the alternating width of the links in a chain. These teeth have typically been configured to have a set of narrow teeth alternating with a set of wider teeth. However, the use of teeth of larger size also may increase the weight of the chain ring and the vehicle, which may be deemed undesirable. In addition, the use of a tooth of larger size may, in some cases, increase the risk of a tooth catching on a portion of the chain due to that increased size, thereby creating damage or risk of injury. Further, the use of such a design may increase the likelihood of dirt, mud, or other debris becoming entangled in the ring and/or between the teeth of the ring and impeding the meshing of the teeth and the chain.

<CIT> discloses a sprocket associated with a chain in a power transmission system. The sprocket comprises a behaviour region formed at least at its outer periphery, and a plurality of teeth. A chain including rollers extends around the sprocket so that the teeth are automatically engaged with opposite ends of each roller. A clearance is left between the teeth and roller link plates and pin link plates so as to ensure proper engagement of the sprocket with the chain.

In order to avoid or minimise the above mentioned drawbacks (risk of chain disengagement, increased weight of the chain ring, risk of tooth catching on a portion of the chain due to increased size, thereby creating damage or risk of injury, likelihood of dirt, mud or other debris becoming entangled between the teeth of the chain ring and impeding the meshing of the teeth and chain), a vehicle drive system as defined in claim <NUM> is proposed. Optional embodiments of the claimed invention are indicated in the dependent claims.

In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific term so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose, as long as it is according to the appended claims. For example, the word connected or terms similar thereto are often used. They are not limited to direct connection, but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art.

In this detailed description, various terms relating to direction may be used. The elements discussed herein relate to a bicycle. Because, in its operable position, a bicycle is oriented generally vertically, i.e., perpendicular to the ground, the direction terms refer to the position of an element relative to gravity when the bicycle is in its operable position. Accordingly, for example, the term "downwardly" refers to the direction towards the ground when the bicycle is in its operable position, and the term "forwardly" relates to a direction towards a front wheel of the bicycle when it is in its operable position. Further, the terms "inboard" and "outboard" may be used. The term "inboard" describes a position between one item and a vertical plane substantially bisecting the bicycle. The term "outboard" describes a position of an object laterally farther from the vertical centerplane of the bicycle. In addition, the terms "bicycle" and "bike" are used herein interchangeably. A person having ordinary skill in the art will understand that if something is referred to as one, it can refer to the other.

One embodiment of a chain ring <NUM> is shown in <FIG>. In some respects, the chain ring <NUM> has a conventional design. For example, the chain ring <NUM> has a central bore <NUM> through which a bicycle crank (not shown) may pass. The bicycle crank and/or other hardware may be used to mount the chain ring <NUM> in operative position on a bicycle (not shown) in any conventional manner. A plurality of teeth <NUM> may be joined or connected to one another and may be serially arranged and radially spaced around a circumference <NUM> of the chain ring <NUM>.

As may be best seen from the views shown in <FIG>, the teeth <NUM> may be separated into two subsets that have differing shapes. A first subset of teeth may include first tooth <NUM>, second tooth <NUM>, and third tooth <NUM>. A second subset of teeth may include fourth tooth <NUM>, fifth tooth <NUM>, and sixth tooth <NUM>. As will be apparent to a person having ordinary skill in the art, each tooth in the first subset of teeth may be substantially identical to one another. Similarly, each tooth in the second subset of teeth may be substantially identical to one another. In the illustrated embodiment, each tooth on the chain ring <NUM> is either one of the first subset of teeth or the second subset of teeth. However, in other embodiments, a chain ring may include one or more teeth that have a shape and size that do not match the size and shape of one of the first and second subset of teeth as may be desired. In the illustrated embodiment, teeth from the first and second subsets may be interspersed or alternated with one another. That is, each tooth in the first subset may be adjacent two teeth from the second subset. For example, the first tooth <NUM> of the first subset may be between the fourth tooth <NUM> and the fifth tooth <NUM> of the second subset. Similarly, each tooth in the second subset may be adjacent two teeth from the first subset. For example, the fifth tooth <NUM> of the second subset may be between the first tooth <NUM> and the second tooth <NUM> of the first subset.

The determination of whether a tooth is in the first subset or the second subset may be made by considering the shape and size of the respective tooth at its thickest point. In the illustrated embodiments, the widest or thickest point of each of the plurality of teeth may be at its base. However, in another embodiment, the thickest point of a respective tooth may be elsewhere on the tooth. In the present embodiment, where a particular configuration is described as being at the "base" of the tooth, a person of ordinary skill in the art will understand that term to include a thickest point of a tooth, regardless of where it appears along a height of the tooth. Similarly, the terms "thickness" and "width" and their related forms may be used interchangeably in the present disclosure. A person having ordinary skill in the art will understand that the terms "width" and "thickness" refer to the dimension of a tooth or ring generally perpendicular to the driving direction of the tooth and ring. In many embodiments, each of the plurality of teeth has a thickness. The thickness of each of the plurality of teeth at its respective thickest point is substantially identical to the thickness of each of the remaining teeth in the plurality of teeth at their respective thickest points.

The shape and size of each tooth at a top surface may be best seen in <FIG> and the shape and size of each tooth at a thickest point thereof may be best seen in <FIG>.

Because each tooth in the first subset of teeth is substantially identical, each respective tooth in the first subset may be described in the same manner and may have the same properties as the first tooth <NUM>, which will be described herein. Because each tooth in the second subset of teeth is substantially identical, each respective tooth in the second subset may be described in the same manner and may have the same properties as the fifth tooth <NUM>, which will be described herein.

As shown in <FIG>, the top surface <NUM> of the first tooth <NUM> may be substantially rectangular. The top surface <NUM> may have a length <NUM> and a width or thickness <NUM>. The thickness of the first tooth <NUM> may increase from its top surface <NUM> to its base <NUM> (see <FIG>) in a first direction <NUM> outward on a first side <NUM> of the first tooth <NUM>, and thus the first side <NUM> may be considered tapered. In the embodiment illustrated in <FIG>, the first direction <NUM> may be an outboard direction.

As shown in <FIG>, at its base <NUM>, the first tooth <NUM> may have a first cross sectional shape. In some embodiments, the first cross sectional shape may be a rectangular cross sectional shape. At the thickest point <NUM>, the first tooth <NUM> may have a length <NUM> and a thickness <NUM>. The thickness <NUM> may be greater than the thickness <NUM>.

As shown in <FIG>, the top surface <NUM> of the fifth tooth <NUM> may be substantially hat-shaped. The top surface <NUM> may have a length <NUM>, a thickness <NUM> at its narrowest point (the "brim"), and a thickness <NUM> at its widest point (the "crown"). The thickness of the widest part of the fifth tooth <NUM> may increase from its top surface <NUM> to its base <NUM> (see <FIG>) in a second direction <NUM> outward on a second side <NUM> of the fifth tooth <NUM>. In some embodiments, the fifth tooth <NUM> may widen more greatly along a length <NUM> that is about one-half of the length <NUM> of the fifth tooth <NUM>. In the embodiment shown in <FIG>, the second direction is an inboard direction.

As shown in <FIG>, at its base <NUM>, the fifth tooth <NUM> may have a second cross-sectional shape. In some embodiments, the second cross sectional shape may be a hat-shaped cross-sectional shape. At the base <NUM>, the fifth tooth <NUM> may have a length <NUM>, a thickness <NUM> at its narrowest point, and a thickness <NUM> at its widest point. The thickness <NUM> at the widest point may be greater than the thickness <NUM> at the widest point at the top surface <NUM> of the fifth tooth <NUM>.

As may be best seen in <FIG>, a portion of each tooth may be aligned with a portion of each other tooth. As may be seen, the first tooth <NUM> has a rectangular top surface <NUM> having a length <NUM> and a width <NUM>. The fifth tooth <NUM> in its narrow portion can also be considered to have a rectangular surface having a length <NUM> and a width <NUM>. In some embodiments, the length <NUM> of the first tooth <NUM> may be substantially identical to the length <NUM> of the fifth tooth <NUM>. In some embodiments, the width <NUM> of the first tooth <NUM> may be substantially identical to the width <NUM> of the fifth tooth <NUM>. In many embodiments, the teeth <NUM>, <NUM> may be arranged such that these identical rectangular portions are aligned with each other around the circumference <NUM> of the chain ring <NUM>.

In other embodiments, the size, shape, and placement of the top surfaces of the teeth may vary from the exemplary designs shown. While the illustrated embodiments show each tooth having a rectangular top surface portion, the top surfaces of the teeth may have non-rectangular shapes and may have shapes different from one another. In some embodiments, the top surfaces are offset from one another.

In the embodiment shown, the thickness <NUM> of the fifth tooth <NUM> may be greater at the widest point of its top surface <NUM> than the thickness <NUM> of the first tooth <NUM> at the widest point of its top surface. As will be seen in <FIG> below, in some embodiments, the fifth tooth <NUM> may be designed such that the fifth tooth <NUM> may have only a rectangular portion at the top surface <NUM> having the thickness <NUM>. Such a taper may be desirable in some embodiments, and accordingly, the increase in thickness to a thickness <NUM> may be optional in some embodiments.

Further, each tooth <NUM>, <NUM> may be configured to have one side that is more highly tapered than the other, or one side may be tapered and the opposite side may not be tapered at all. In the embodiment illustrated in <FIG> and <FIG>, each tooth <NUM>, <NUM> may have a respective tapered side. The first side <NUM> of the first tooth <NUM> may be the tapered or more tapered side and the second side <NUM> of the second tooth <NUM> may be the tapered or more tapered side. Each tooth <NUM>, <NUM> may similarly have a less tapered or substantially planar side. The second side <NUM> of the first tooth <NUM> may be less tapered or the substantially planar side and the first side <NUM> of the second tooth <NUM> may be less tapered or the substantially planar side. While this feature of tapering in opposite directions may be seen in <FIG> and <FIG>, it may be more apparent in a comparison of the views of <FIG> and <FIG>, showing a perspective view of the chain ring from opposite directions. In some embodiments, the opposite directions and magnitudes of the taper may be designed to facilitate a function of the teeth <NUM>, <NUM>, namely, to create opposing lateral forces on adjacent links of a drive chain. The teeth <NUM>, <NUM> may be configured such that the more tapered side <NUM>, <NUM> of the respective tooth <NUM>, <NUM> may be the side that is configured to apply a lateral force to a drive chain link. The respective opposite, less tapered side <NUM>, <NUM> may be configured to be spaced from an interfitting drive chain link or to merely be permitted to contact the interfitting link slightly. These features of the drive train as a whole will be disclosed in greater detail in connection with at least <FIG> and <FIG>.

Looking now at <FIG>, the thicknesses of the teeth may also be understood in relation to each other. In many embodiments, the thickness <NUM> of the first tooth <NUM> is substantially identical to the thickness <NUM> of the fifth tooth <NUM> at its widest point. In many embodiments, the length <NUM> of the first tooth <NUM> may be substantially identical to the length <NUM> of the fifth tooth <NUM>. Thus, even though the cross-sectional shapes of the teeth may differ, each of the plurality of teeth has substantially the same width or thickness and may have substantially the same length.

Turning now to <FIG>, a closer side view of the first tooth <NUM> and the fifth tooth <NUM> from the inboard side may be seen. The first tooth <NUM> may have a leading edge <NUM> and a trailing edge <NUM>. The fifth tooth <NUM> may have a leading edge <NUM> and a trailing edge <NUM>. In the embodiment shown, the each edge <NUM>, <NUM>, <NUM>, <NUM> of each tooth may angle in the direction of rotation. The use of such an angle may provide a variety of functions, such as, improving the mating of the teeth <NUM> with a drive chain (not shown). Such an angled portion is merely one example of an appropriate tooth shape. Within the present disclosure, each tooth may be described as having a base, and various features of the teeth at the base may be described. The base of a tooth may be considered to be the general area on the tooth where it begins projecting from the central portion of the chain ring. As an example only, the base of the first tooth <NUM> may be in the area identified as <NUM> and the base of the fifth tooth <NUM> may be in the area identified as <NUM>.

The illustrated embodiments disclose very few configurations of teeth that may be used. In many embodiments, it may be desirable for all the teeth to have similar shapes and sizes. In other embodiments, the teeth may vary in shape and size. In some embodiments, only teeth having a shape and size corresponding to one of the first subset and the second subset may be used. In other embodiments, teeth having a configuration different from that disclosed as being desirable for the first and second subset may be used. In many embodiments, it may be desirable for the chain ring to include substantially the same number of teeth in the first subset and the second subset. In many embodiments, it may be desirable for the chain ring to have an alternating pattern of teeth in the first subset and teeth in the second subset around the entire circumference. In the disclosed embodiments, the crown portion of the hat-shaped cross section in the second subset of teeth is shown as being one half the length of the remainder of the tooth. However, in other embodiments, the crown portion may be longer or shorter, based on the circumference of the ring or the number of teeth thereon, or for any other reason deemed relevant by a designer. In other embodiments, rather than the leading and trailing edges both being angled in the direction of rotation, the leading edge may be angled away from the direction of rotation to provide a reduced surface area for the tooth at the top surface. In other embodiments, the leading and trailing edges may not include any substantial taper. Other modifications to the design are possible and will be understood by a person having ordinary skill in the art to fall within the scope of the disclosure.

Turning now to <FIG>, the interaction of the chain ring teeth and the drive chain is shown. <FIG> shows the interaction and relative position of one outer link of a drive chain with a tooth of the second subset and the interaction and relative position of the two flanking inner links of a drive chain with teeth of the first subset. As is conventional, the chain ring is configured to removably interconnect with the drive chain in order to drive or propel the bicycle. A person having ordinary skill in the art will recognize that in operative position, a plurality of many more chain links, both inner and outer, will be present and engaged with the teeth and other parts to drive the bicycle. Only three links are shown in this FIG.

Looking first at the first tooth <NUM>, the first tooth <NUM> is configured to fit within or interfit with a respective first link <NUM> of the drive chain in operative position. In the illustrated embodiment, the first link <NUM> may be an inner link. A first face <NUM> of the first tooth <NUM> may contact a first plate <NUM> of a first link <NUM> of the drive chain. The first face <NUM> of the first tooth <NUM> may correspond to the more tapered side <NUM> of the first tooth <NUM>. This contact between the face <NUM> and the first link <NUM> may apply a lateral pressure or force on the first link <NUM> in the first lateral direction <NUM>. In this embodiment, the first lateral direction may be outboard. The drive face <NUM> of the first tooth <NUM> may contact a roller <NUM> of the drive chain to impart driving force to the drive chain and other drive train elements. The first tooth <NUM> may also have a second face <NUM>, which may correspond to the less tapered face <NUM> of the first tooth <NUM>. The second face <NUM> may be configured to be spaced from the second plate <NUM> of the first link <NUM> of the drive chain. In other embodiments, the second face <NUM> may be permitted to contact the second plate <NUM> of the first link of the drive chain. In some embodiments, the configuration of the second face <NUM> as a substantially planar surface in conjunction with the remaining features of the configuration (which will be described in greater detail below) may enable the second face <NUM> to remain spaced from the second plate <NUM> in use.

Looking next at the fifth tooth <NUM>, the fifth tooth <NUM> may be configured to fit within or interfit with a respective second link <NUM> of the drive chain. In the illustrated embodiment, the second link <NUM> may be an outer link. The outer face <NUM> of the fifth tooth <NUM> may contact a second plate <NUM> of the second link <NUM> of the drive chain. The outer face <NUM> of the fifth tooth <NUM> corresponds to the more tapered side <NUM> of the fifth tooth <NUM>. This contact between the face <NUM> and the second link <NUM> may apply a lateral pressure or force on the second link <NUM> in the second lateral direction <NUM>. In this embodiment, the second lateral direction may be inboard. In some embodiments, the fifth tooth <NUM> may also engage an edge <NUM> of an adjacent first link <NUM>, but may not apply a substantial force thereto. The drive face <NUM> of the fifth tooth <NUM> may contact a roller <NUM> of the drive chain to impart driving force to the drive chain and other drive train elements. The fifth tooth <NUM> may also have a second face <NUM>, which may correspond to the less tapered face <NUM> of the fifth tooth <NUM>. The second face <NUM> may be configured to be spaced from the second plate <NUM> of the second link <NUM> of the drive chain. In other embodiments, the second face <NUM> may be permitted to contact the second plate <NUM> of the second link <NUM> of the drive chain. In some embodiments, the configuration of the second face <NUM> as a substantially planar surface in conjunction with the remaining features of the configuration, such as a common thickness between all the teeth (which will be described in greater detail below) may enable the second face <NUM> to remain spaced from the second plate <NUM> in use.

Looking at <FIG>, any chain <NUM> has a centerline <NUM>. As may be seen in <FIG>, the first tooth <NUM> and the fifth tooth <NUM> are arranged such that their top surfaces are offset from the centerline <NUM> of the chain. The first tooth <NUM> may taper to a first rectangular top face <NUM>. The fifth tooth <NUM> may taper to include a second rectangular portion of the top face <NUM>. The first rectangular top face <NUM> and the second rectangular top face <NUM> may be aligned with each other, as was also discussed in connection with <FIG>. Comparing the positions of the first rectangular top face <NUM> and the second rectangular top face <NUM> relative to the centerline <NUM> of the drive chain, it is apparent that the first rectangular top face <NUM> and the second rectangular top face <NUM> are offset laterally from the centerline <NUM>. The particular lateral offset between the top faces <NUM> and <NUM> may vary depending on the desires of a designer. However, in the embodiments of the invention, the top faces <NUM> and <NUM> are positioned such that they are not symmetrical about the centerline <NUM> of the drive chain. As may be seen, the top surface <NUM> has a first top surface centerline <NUM>, and top surface <NUM> has a second top surface centerline <NUM>. It will be understood by a person having ordinary skill in the art that the respective centerline <NUM>, <NUM> of a respective top surface <NUM>, <NUM> of a respective tooth <NUM>, <NUM> is defined as the line defining the lateral middle of the respective top surface <NUM>, <NUM> between a respective first top surface edge <NUM>, <NUM> and a respective second top surface edge <NUM>, <NUM>. In the embodiment illustrated in <FIG>, the first top surface edge <NUM>, <NUM> may be an outermost edge and the second top surface edge <NUM>, <NUM> may be an innermost edge. In another embodiment, the first top surface edge <NUM>, <NUM> may be an innermost edge and the second top surface edge <NUM>, <NUM> may be an outermost edge.

As may be seen in <FIG>, the respective centerlines <NUM> and <NUM> are both offset laterally from the centerline <NUM> of the drive chain in operative position. In the illustrated embodiment, the respective centerlines <NUM>, <NUM> are offset laterally from the centerline <NUM> in the same direction, namely, an inboard direction. In another embodiment, the centerlines are offset laterally in an outboard direction.

In addition, the teeth <NUM> and <NUM> and the remainder of the plurality of teeth may each be considered to have a position across a thickness of the chain ring. This relationship may be best seen in <FIG>. Comparing the view of <FIG> to the view of <FIG>, and considering the description in the preceding paragraphs, each of the plurality of teeth may be considered to have a position relative to the centerline <NUM> of the chain. In some embodiments, the tooth position of a tooth may be defined as the centerline of the respective tooth at a base of that tooth. As shown in <FIG>, the centerline <NUM> of the tooth <NUM> and the centerline <NUM> of the tooth <NUM> are both offset from the centerline <NUM> of the chain. Accordingly, an evaluation of the centerlines at the bases may reveal an average tooth position for the plurality of teeth as a whole. In many embodiments, such as the one shown in <FIG>, the average tooth position may be offset from the centerline <NUM> of the drive chain in operative position.

In addition, the top surfaces <NUM> and <NUM> are arranged laterally asymmetrically about the centerline <NUM> of the drive chain in operative position. When viewing the top surfaces <NUM> and <NUM> relative to the centerline <NUM>, it is apparent that lateral symmetry is not present. Indeed, <FIG> shows both the top surface <NUM> and the top surface <NUM> are offset laterally from the chain centerline <NUM>. Both top surfaces <NUM>, <NUM> are offset laterally in the same direction from the chain centerline <NUM>. In the illustrated embodiment, the top surfaces <NUM>, <NUM> may be offset laterally on an inboard side of the chain centerline <NUM>. In another embodiment, the top surfaces <NUM>, <NUM> may both be offset laterally from the chain centerline <NUM> in an outboard direction.

Further, the respective bases <NUM>, <NUM> of the teeth <NUM>, <NUM> may have a similar relationship to the chain centerline <NUM> as their top surfaces <NUM>, <NUM>. As may be seen, the first base <NUM> has a first base centerline <NUM>, and the second base <NUM> has a second base centerline <NUM>. It will be understood by a person having ordinary skill in the art that the respective centerline <NUM>, <NUM> of a respective base <NUM>, <NUM> of a respective tooth <NUM>, <NUM> is defined as the line defining the lateral middle of the respective base <NUM> between a respective first base side <NUM>, <NUM> and a respective second base side <NUM>, <NUM>. In the embodiment illustrated in <FIG>, the first base side <NUM>, <NUM> may be an outermost side and the second base side <NUM>, <NUM> may be an innermost side. In another embodiment, the first base side <NUM>, <NUM> may be an innermost side and the second base side <NUM>, <NUM> may be an outermost side.

As may be seen in <FIG>, the respective centerlines <NUM> and <NUM> may be both offset laterally from the centerline <NUM> of the drive chain in operative position. However, in many embodiments, the first base centerline <NUM> may be aligned, such as coincident, with the chain centerline <NUM>. In the illustrated embodiment, the respective centerlines <NUM>, <NUM> may be offset laterally from the centerline <NUM> in the same direction, namely, an inboard direction. In another embodiment, the centerlines may be offset laterally in an outboard direction or may each be offset laterally in a different direction.

In addition, the bases <NUM>, <NUM> are be arranged laterally asymmetrically about the centerline <NUM> of the drive chain in operative position. When viewing the bases <NUM>, <NUM> relative to the centerline <NUM>, it is apparent that lateral symmetry is not present. In the illustrated embodiment, the first base <NUM> may be arranged substantially on or symmetrically about the chain centerline <NUM>, while the second base <NUM> may be offset laterally from the centerline <NUM>, in this embodiment in an inboard direction. This difference in offset may create asymmetry in positioning.

In some embodiments, only one of the top surfaces may be offset laterally from a centerline of the drive chain in operative position. In some embodiments, only the top surface of the first tooth may be offset laterally from a centerline of the drive chain when the chain ring and the drive chain are placed in operative position. The top surface of the second tooth may be positioned laterally symmetrically around the drive chain centerline.

It will be apparent to one of ordinary skill in the art that, among the reasons that each respective tooth in the first subset of teeth may be positioned between two teeth in the second subset of teeth (and vice versa) in an alternating pattern around the chain ring, is that a drive chain typically has alternating inner links and outer links along its length. The chain ring may be configured to have alternating teeth configured to fit into the appropriate width and shape of alternating link. It will be apparent to a person having ordinary skill in the art that while the illustrated embodiment envisions the first subset of teeth applying a lateral force to the chain in an outboard direction and the second subset of teeth applying a lateral force to the chain in an inboard direction, the teeth could be oppositely oriented and positioned on the chain ring to apply force in the opposite directions. A person having ordinary skill in the art is able to make such a modification without undue experimentation.

<FIG> illustrates a few modifications that may be made to the configuration. In brief, the degree of taper of the second tooth is changed and the directions of taper of the first and second teeth are reversed. However, the comparative features of the teeth remain, such as the inclusion of tapers in opposite directions, the spacing of the faces of the teeth relative to the links of the chain, the differing cross sectional shapes of the teeth, and any other features not specifically mentioned.

In the embodiment of <FIG>, the top surface <NUM> of the fifth tooth <NUM> is rectangular instead of hat-shaped. In this embodiment, the fifth tooth <NUM> tapers more greatly toward the top surface than the fifth tooth that is shown and described in the embodiment above. Accordingly, the top surface <NUM> may be rectangular or substantially rectangular. A person having ordinary skill in the art will be able to easily select an appropriate taper as the designer deems appropriate.

In addition, the directions of taper are reversed from those of <FIG>. Looking first at the first tooth <NUM>, the first tooth <NUM> may be configured to fit within an inner link <NUM> of the drive chain. The first tooth <NUM> may project outwardly in a first direction <NUM>. The outer face <NUM> of the first tooth <NUM> contacts a first plate <NUM> of an inner link <NUM> of the drive chain. This contact between the face <NUM> and the inner link <NUM> may apply a lateral pressure on the inner link <NUM> in the first lateral direction <NUM>. In this embodiment, the first direction <NUM> is inboard.

Looking next at the fifth tooth <NUM>, the fifth tooth <NUM> may be configured to fit within an outer link <NUM> of the drive chain. The first tooth <NUM> may project outwardly in a second direction <NUM>. The outer face <NUM> of the fifth tooth <NUM> may contact a second plate <NUM> of an outer link <NUM> of the drive chain. This contact between the face <NUM> and the outer link <NUM> may apply a lateral pressure on the outer link <NUM> in the second lateral direction <NUM>. In some embodiments, the fifth tooth <NUM> may also engage an edge <NUM> of an adjacent inner link <NUM>, but may not apply a substantial force thereto. In this embodiment, the second lateral direction <NUM> is outboard.

As may be seen, the top surface <NUM> of the first tooth <NUM> may have a first top surface centerline <NUM>, and the top surface <NUM> of the second tooth <NUM> may have a second top surface centerline <NUM>. It will be understood by a person having ordinary skill in the art that the respective centerline <NUM>, <NUM> of a respective top surface <NUM>, <NUM> of a respective tooth <NUM>, <NUM> may be defined as the line defining the lateral middle of the respective top surface <NUM>, <NUM> between a respective first top surface edge <NUM>, <NUM> and a respective second top surface edge <NUM>, <NUM>. In the embodiment illustrated in <FIG>, the first top surface edge <NUM>, <NUM> is an innermost edge and the second top surface edge <NUM>, <NUM> is an outermost edge. In another embodiment, the first top surface edge <NUM>, <NUM> may be an outermost edge and the second top surface edge <NUM>, <NUM> may be an innermost edge.

As may be seen in <FIG>, the respective centerlines <NUM> and <NUM> may be both offset laterally from the centerline <NUM> of the drive chain in operative position. In the illustrated embodiment, the respective centerlines <NUM>, <NUM> may be offset laterally from the centerline <NUM> in the same direction, namely, an outboard direction.

In addition, the top surfaces <NUM> and <NUM> may also be arranged laterally asymmetrically about the centerline <NUM> of the drive chain in operative position. When viewing the top surfaces <NUM> and <NUM> relative to the centerline <NUM>, it is apparent that lateral symmetry is not present. Indeed, <FIG> shows both the top surface <NUM> and the top surface <NUM> may be offset laterally from the chain centerline <NUM>. Both top surfaces <NUM>, <NUM> may be offset laterally in the same direction from the chain centerline <NUM>. In the illustrated embodiment, the top surfaces <NUM>, <NUM> may be offset laterally on an outboard side of the chain centerline <NUM>. In another embodiment, the top surfaces <NUM>, <NUM> may both be offset laterally from the chain centerline <NUM> in an inboard direction.

Further, the respective bases <NUM>, <NUM> of the teeth <NUM>, <NUM> may have a similar relationship to the chain centerline <NUM> as their top surfaces <NUM>, <NUM>. As may be seen, the first base <NUM> may have a first base centerline <NUM>, and the second base <NUM> may have a second base centerline <NUM>. It will be understood by a person having ordinary skill in the art that the respective centerline <NUM>, <NUM> of a respective base <NUM>, <NUM> of a respective tooth <NUM>, <NUM> may be defined as the line defining the lateral middle of the respective base <NUM> between a respective first base side <NUM>, <NUM> and a respective second base side <NUM>, <NUM>. In the embodiment illustrated in <FIG>, the first base side <NUM>, <NUM> may be an innermost side and the second base side <NUM>, <NUM> may be an outermost side. In another embodiment, the first base side <NUM>, <NUM> may be an outermost side and the second base side <NUM>, <NUM> may be an innermost side.

As may be seen in <FIG>, the respective centerlines <NUM> and <NUM> are both offset laterally from the centerline <NUM> of the drive chain in operative position. However, in many embodiments, the first base centerline <NUM> may be aligned with the chain centerline <NUM>. In the illustrated embodiment, the respective centerlines <NUM>, <NUM> are offset laterally from the centerline <NUM> in the same direction, namely, an outboard direction. In another embodiment, the centerlines may be offset laterally in an inboard direction.

In addition, the bases <NUM>, <NUM> may also be arranged laterally asymmetrically about the centerline <NUM> of the drive chain in operative position. When viewing the bases <NUM>, <NUM> relative to the centerline <NUM>, it is apparent that lateral symmetry is not present. In the illustrated embodiment, the first base <NUM> may be arranged substantially on or symmetrically about the chain centerline <NUM>, while the second base <NUM> may be offset laterally from the centerline <NUM>, in this embodiment in an outboard direction. This difference in offset may create asymmetry in positioning.

The size, shape, and position of the teeth of the chain ring may be selected such that the nominal width of the teeth is greater than the nominal width of adj acent links. Returning to <FIG>, the first inner lateral surface <NUM> of the outer link <NUM> may be considered to lie in, at, outside of, or along a first plane <NUM>. A third inner lateral surface <NUM> of the inner link <NUM> may be considered to lie in, at, outside of or along a second plane <NUM>. The first inner lateral surface <NUM> and the third inner lateral surface <NUM> of the respective links may face one another. The link nominal width or link planar separation may be measured as the shortest distance between the first plane <NUM> and the second plane <NUM> measured substantially perpendicular to the first plane <NUM> and the second plane <NUM>. One exemplary location of measurement is shown at <NUM>.

Similarly, the first inner lateral surface <NUM> may have a first centerpoint <NUM>. Because chain link plates are generally both horizontally and vertically symmetrical, the first centerpoint <NUM> may be positioned at a point where the horizontal and vertical axes of symmetry intersect. The third inner lateral surface <NUM> may have a similarly defined second centerpoint <NUM>. A link distance may be measured as the shortest distance between the first centerpoint <NUM> and the second centerpoint <NUM> of two adjacent links. One exemplary location of measurement is shown at <NUM>.

Turning now to <FIG>, the outer face <NUM> of the first tooth <NUM> may be said to lie in a third plane <NUM>. The outer face <NUM> of the fifth tooth <NUM> may be said to lie in a fourth plane <NUM>. The tooth nominal width or tooth planar separation may be measured as the shortest distance between the third plane <NUM> and the fourth plane <NUM> measured substantially perpendicular to the third plane <NUM> and the fourth plane <NUM>. One exemplary location of measurement is shown at <NUM>.

Similarly, outer face <NUM> of the first tooth <NUM> may have a first centerpoint <NUM>. The first centerpoint <NUM> may be defined as the longitudinal middle point of the widest section of the first tooth <NUM> measured at the base. The outer face <NUM> of the fifth tooth <NUM> may have a similarly defined second centerpoint <NUM>. A tooth distance may be measured as the shortest distance between the first centerpoint <NUM> and the second centerpoint <NUM>. One exemplary location of measurement is shown at <NUM>.

In many embodiments, the amount of lateral pressure on the drive chain from the chain ring teeth may be determined by the relative positioning of these parts. In many embodiments, the tooth planar separation may be greater than the link planar separation. In many embodiments, the tooth distance may be greater than the link distance. In many embodiments, both will be true. Because the tooth shape may vary, it may be more meaningful in some embodiments to measure a tooth planar separation, and in other embodiments, it may be more meaningful to measure a tooth distance. For example, if the outer face <NUM> of one tooth is not parallel to the outer face <NUM> of another tooth, it may be difficult or impossible to judge a planar separation. In other embodiments, where there may be multiple discrete points that form an outer face of a tooth, rather than a planar surface, selecting a centerpoint may be complicated or impossible. In some embodiments with a single contact point between an outer tooth face and an inner surface of a chain link, that point may be considered the centerpoint. In some embodiments with multiple discrete points of contact between an outer tooth face and an inner surface of a chain link, the most central point may be considered to be the centerpoint. In many embodiments, however, the teeth and links may have a regular, symmetrical shape where either measurement can be made and evaluated to determine the amount of lateral pressure that will be created between the chain ring and the drive chain.

It will be apparent to a person having ordinary skill in the art that the measurements noted in the specification and claims may be complicated to accurately measure. Manufacturing tolerances, wear, and the like may cause variation in the size, shape, thickness, and position of the chain ring teeth and various parts of any given drive chain. Accordingly, measurements may be taken at varying points along a chain ring and/or drive chain. In some embodiments, an average actual relative measurement may be used. In other embodiments, a dimension as designed may be considered. In addition, a variety of drive chains could be used with the chain ring disclosed in the present invention. In many embodiments, the drive chain may be selected to have the size and spacing characteristics relative to the chain ring dimensions. In many embodiments, drive chains that are commonly used with <NUM>, <NUM>, and <NUM> speed bicycles are appropriate for use in the disclosed design.

Claim 1:
A drive system for a vehicle, comprising:
a drive chain (<NUM>) having a plurality of links (<NUM>, <NUM>;<NUM>,<NUM>; <NUM>,<NUM>) and a centerline (<NUM>;<NUM>; <NUM>); and
a chain ring (<NUM>) having a plurality of teeth (<NUM>;<NUM>,<NUM>; <NUM>,<NUM>)joined to one another and serially arranged;
wherein each of the plurality of teeth (<NUM>;<NUM>,<NUM>;<NUM>,<NUM>;) is configured to interfit with a respective one of the plurality of links (<NUM>, <NUM>; <NUM>,<NUM>; <NUM>, <NUM>) of the drive chain (<NUM>);
wherein each of the plurality of teeth (<NUM>) has a top surface (<NUM>;<NUM>;<NUM>) and a base (<NUM>;<NUM>;<NUM>);
wherein each of the plurality of teeth (<NUM>; <NUM>,<NUM>;<NUM>,<NUM>) has a thickness (<NUM>), the thickness of each of the plurality of teeth at its respective thickest point (<NUM>,<NUM>;<NUM>,<NUM>) being substantially identical;
wherein, when the drive chain (<NUM>) and chain ring (<NUM>) are interfitted with one another, the bases (<NUM>;<NUM>;<NUM>,<NUM>) of the teeth (<NUM>;<NUM>,<NUM>;<NUM>,<NUM>) are laterally asymmetrically arranged about the centerline (<NUM>;<NUM>;<NUM>) of the drive chain (<NUM>); and
wherein, when the drive chain (<NUM>) and the chain ring (<NUM>) are interfitted with one another, the top surfaces (<NUM>;<NUM>;<NUM>) of the teeth (<NUM>;<NUM>,<NUM>;<NUM>,<NUM>) are laterally asymmetrically arranged about the centerline (<NUM>;<NUM>;<NUM>) of that drive chain (<NUM>),
characterized in that, when in operative position, each centerline (<NUM>, <NUM>;<NUM>,<NUM>) of each top surface (<NUM>;<NUM>,<NUM>;<NUM>;<NUM>,) of each tooth (<NUM>;<NUM>,<NUM>;<NUM>,<NUM>) is offset laterally from the centerline (<NUM>; <NUM>) of the drive chain (<NUM>) in the same direction.