Patent Description:
While riding a vehicle with a chain driven drivetrain, management of the chain and chainring engagement is particularly important to safe and effective propulsion of the bicycle. Keeping the chain engaged with the chainring can be difficult, which is especially true of geared bicycles which can experience severe changes in chain tension, and energetic motion of the chain, especially from riding over rough terrain. Moreover, the chainring in any bicycle can potentially touch the chain stay of the bicycle frame when the crank is in a position where high loads are applied by the rider, causing an elastic deformation of the bicycle frame and the crankset. This can lead to damage to the frame and chainring and cause other problems.

The invention provides an enhanced drive chain management, especially for a bicycle that can successfully and reliably be ridden over rough and challenging terrain.

<CIT> describes a bicycle chainring including a number of regular teeth and groups of at least two consecutive teeth having a reduced width or a twisted shape in order to provide better shifting characteristics.

<CIT> describes a cushioned sprocket for a particular chain wherein the sprocket is formed with cushioning teeth supporting particular chain links of the drive chain.

<CIT> describes a sprocket wheel having a first group of teeth and a second group of teeth arranged alternatingly wherein the first teeth are arranged axially offset of the second teeth.

<CIT>, which shows the preamble of claim <NUM>, shows and describes a sprocket with alternatingly arranged thin and thick teeth.

The invention provides a solitary chainring according to claim <NUM>. The solitary chainring, wherein solitary means only one, includes a plurality of teeth formed about a periphery of the chainring, the plurality of teeth consisting of an even number. The plurality of teeth includes a first group of teeth and a second group of teeth arranged alternatingly between the first group of teeth. The first group of teeth and the second group of teeth are equal in number. Each of the first and second group of teeth includes an outboard side and an inboard side opposite the outboard side. Each tooth of the first group of teeth includes at least a first protrusion on the outboard side thereof and each tooth of the second group of teeth is free of protrusions.

The first group of teeth and the second group of teeth are equal in number. Each of the outboard side and the inboard side of each of the second group of teeth may define a recess formed in the chainring along each tooth of the second group of teeth.

The chainring may further comprise a second protrusion on the inboard side of each tooth of the first group of teeth.

The chainring may further provide that the first protrusion has a first width and the second protrusion has a second width, wherein the first width is equal to the second width.

The chainring may further provide that the first width is greater than the second width.

The chainring may further provide that the first group of teeth each have a cross-shaped cross section adjacent a base thereof.

The chainring may further provide that the second group of teeth each have a rectangular-shaped cross section adjacent a base thereof.

The chainring may further provide that each tooth of the first group of teeth and the second group teeth include a front flank, and wherein the front flank includes a protruding tip portion configured to guide the chain.

The chainring may further provide that each tooth of the first group of teeth and the second group teeth include a rear flank, and wherein the rear flank includes a hook portion configured to guide the chain.

The chainring may further provide that each tooth of the first group of teeth and the second group teeth include a front flank and a rear flank, wherein the front flank of each tooth includes a protruding tip portion.

The chainring may further provide that the rear flank of each tooth includes a hook portion.

The chainring may further provide that the hook portion includes a generally radially-oriented portion.

The chainring may further provide that the protruding tip portion and an adjacent tooth hook portion cooperate to guide the chain.

The chainring may further provide that each tooth of the first group of teeth includes a radially outer chamfer having a first extent along the outboard side of each tooth.

The chainring may further provide that each tooth of the second group of teeth includes a radially outer chamfer having a second extent along the outboard side of each tooth.

The chainring may further provide that each tooth of the first group of teeth includes an outer chamfer having a first extent and each tooth of the second group of teeth includes an outer chamfer having a second extent and the first extent is lesser than the second extent.

The chainring may further provide that each of the inboard and outboard sides of each tooth of the second group of teeth define a recess formed in the chainring.

The chainring may further provide that each recess is defined by an axially-extending base surface and a radially-extending wall.

The chainring may further provide that each recess extends from a front flank of a first tooth of the first group of teeth to a rear flank of a second tooth of the first group of teeth, wherein the first tooth and the second tooth are adjacent ones of the first group of teeth in a drive direction.

The chainring may further comprise a first protrusion on the outboard side and a second protrusion on the inboard side of each tooth of the first group of teeth, the first and second protrusions defined at least in part by the recess.

The first width of the chainring may be greater than the second width.

The chainring may further provide that the first group of teeth each have a cross-shaped cross section adjacent a base thereof defined by the recess.

The chainring may further provide that the second group of teeth each have a rectangular-shaped cross section adjacent a base thereof defined by the recess.

The chainring may further provide that the protruding tip portion and an adjacent one of the hook portion cooperate to guide the chain.

The chainring may further provide that each tooth of the first group of teeth includes an outer chamfer having a first extent and each tooth of the second group of teeth includes an outer chamfer having a second extent, the first extent being less than the second extent.

The chainring may further provide that the recess is formed by an axially-extending base surface and a radially-extending wall.

The invention further contemplates a bicycle crankset comprising a bicycle crank arm having only the bicycle solitary chainring attached thereto.

These and other features and advantages of the present invention will be more fully understood from the following description of one or more embodiments of the invention, taken together with the accompanying drawings.

Preferred embodiments of the invention will herein be described with reference to the drawings. It will be understood that the drawings and descriptions set out herein are provided for illustration only and do not limit the invention as defined by the claims appended hereto and any and all their equivalents. For example, the terms "first" and "second" or "left" and "right" are used for the sake of clarity and not as terms of limitation.

Referring to <FIG> of the drawings, numeral <NUM> generally indicates a conventional roller drive chain for a bicycle or any similar chain-driven device. The drive chain <NUM> generally includes outer chain links <NUM> and inner chain links <NUM> which are pivotally mounted on and connected to the outer chain links by pins <NUM>, <NUM>. The outer chain links <NUM> are alternatingly interleaved with the inner chain links <NUM>.

The outer chain links <NUM> have paired outer link plates <NUM> and the inner chain links have paired inner link plates <NUM>. Typically, rollers <NUM> are arranged around the pins <NUM>, <NUM>. The plates <NUM>, <NUM> are provided with holes <NUM> at their ends <NUM>. The pins <NUM>, <NUM> typically extend through and project out of the holes <NUM>, although no projection at all is considered to be optimal. The pins <NUM>, <NUM> are externally riveted at their ends <NUM>, <NUM> during the assembly of the roller chain <NUM>. While the pin <NUM> may be made of round stock, pin <NUM> may be made of tube stock, as in the roller chain <NUM> in <FIG>. A narrow middle part <NUM>, which helps to determine the positioning of the roller chain <NUM> extends between the two circular ends <NUM> of each of the outer link plates <NUM> and the inner link plates <NUM>.

As seen best in <FIG>, and as viewed from above (or below) the chain, the interleaving of the outer links <NUM> and inner links <NUM> creates corresponding alternating outer link spaces <NUM> and inner links spaces <NUM>. Generally, the outer link spaces <NUM> are openings defined by the outer link plates <NUM> and rollers <NUM>. Generally, the inner link spaces <NUM> are openings defined by the inner link plates <NUM> and rollers <NUM>.

The inner link spaces <NUM> are generally rectangular with the long axis of the rectangle aligned with the long axis (A) of the chain <NUM> (as viewed as in <FIG>). The axial length of the inner link spaces <NUM> is determined by the distance between the rollers <NUM>, while the distance between the inner link plates <NUM> determines the transverse spacing of the inner link spaces.

As seen in <FIG>, the outer link spaces <NUM> are generally in the shape of a "cross" or in other words, a "plus. " The axial length of the outer link spaces <NUM> is determined by the distance between the rollers <NUM>, while the distance between the outer link plates <NUM> determines the transverse spacing of the outer link spaces.

It can be seen that the transverse spacing between the outer link plates <NUM> is greater than the spacing between the inner link plates <NUM>. Thus, because the transverse width of the rollers <NUM> determines the spacing of the inner link plates <NUM>, the rollers dictate the transverse spacing D1 of the inner link spaces <NUM>. Similarly, since the outer link plates <NUM> are positioned on the pins <NUM> (or <NUM>) on the outboard sides of the inner link plates <NUM>, the transverse spacing D2 of the outer link spaces <NUM> is dictated by the sum of the transverse width of the rollers <NUM> and the thickness of two inner link plates.

Referring to <FIG>, a chainring <NUM> according to the invention is used with a conventional chain <NUM>. Chainrings typically have a large plurality of teeth compared to cassettes, for example, having about <NUM> or more teeth. A crank or crank arm <NUM> is in a typical position and attached to the chain ring <NUM> in a well-known manner. The crank side of the chainring <NUM> is shown in <FIG>, which is the outboard side <NUM> of the chainring. The outboard side also faces away from the vehicle to which it is attached. The opposite of the outboard side <NUM> of the chainring <NUM> is the inboard side <NUM>. The inboard side <NUM> faces toward the vehicle.

Generally, force applied to the crank arm <NUM> (typically in a downward direction, for example) causes rotation of the chainring <NUM> in a like direction (clockwise). Rotation of the chainring <NUM> causes the chain <NUM> to be drawn over and advanced about the chainring.

The chainring <NUM> has a plurality of teeth <NUM> formed about the periphery <NUM> of the chainring, with the total number of the plurality of teeth consisting of an even number. The plurality of teeth <NUM> include a first group of teeth <NUM> and a second group of teeth <NUM> arranged in an alternating fashion and wherein the first group of teeth is equal in number to the second group of teeth. In a most general form, the invention provides the first group of teeth <NUM>, that is configured to be received by and fitted into the outer link spaces <NUM>, and a second group of teeth <NUM> that is configured to be received by and fitted into the inner link spaces <NUM>.

The overall shape of the chainring periphery <NUM> may be generally circular or non-circular, that is elliptical, oval, polygon, or parabolic, for example. All of the examples of chainrings provided herein are shown with a circular periphery <NUM>.

Each tooth of the first group of teeth <NUM> is configured to engage with the chain <NUM> via an outer link space <NUM>. Each tooth of the second group of teeth <NUM> is configured to engage with the chain <NUM> via an inner link space <NUM>.

Turning to <FIG>, each tooth of the second group of teeth <NUM> has a shape which in a cross sectional view is generally rectangular, particularly at or near the base or root of the tooth. The cross sectional view is taken through a plane parallel to the top land <NUM> of the tooth and passing through the base circle position of the tooth, i.e., about halfway between the root circle and the outside circle.

The rectangular cross section and overall width WO<NUM> of each tooth of the second group of teeth <NUM> should closely match the configuration of each of the inner link spaces <NUM> (<FIG>). The cross section shown of each tooth of the second group of teeth shows that the outboard side <NUM> is generally planar and the inboard side <NUM> is also generally planar. Each tooth of the second group of teeth <NUM> may fill over about <NUM>% of the axial distance D<NUM> of a corresponding space in the chain <NUM>. Preferably, each tooth of the second group of teeth <NUM> may fill over about <NUM>% of D<NUM> of a corresponding space in the chain <NUM>. More preferably, each tooth of the second group of teeth <NUM> may fill over about <NUM>% of D<NUM> of a corresponding space in the chain <NUM>.

Turning to <FIG>, each tooth of the alternative versions of teeth 58a, 58b, 58c of the first group of teeth <NUM> (see <FIG>) has a shape which in a cross sectional view, taken through the tooth as in <FIG>, has the same longitudinal length LT as that of the second group of teeth <NUM> (<FIG>). Each tooth of the first group of teeth <NUM> may fill over about <NUM>% of the distance D<NUM> of a corresponding space in the chain <NUM>. Preferably, each tooth of the first group of teeth <NUM> may fill over about <NUM>% of D<NUM> of a corresponding space in the chain <NUM>. More preferably, each tooth of the first group of teeth <NUM> may fill over about <NUM>% of D<NUM> of a corresponding space in the chain <NUM>.

Each tooth of the first group of teeth <NUM> has the additional feature of an outboard or first protrusion <NUM> on the outboard side <NUM> of each alternative teeth 58a, 58b, and 58c. <FIG> also demonstrates that the inboard side <NUM> of tooth 58a can be the same (i.e., without a protrusion) as the inboard side <NUM> of each of the second group of teeth <NUM>. The first protrusion <NUM> is configured to fit into the corresponding part of outer link spaces <NUM> of chain <NUM> (<FIG>) and has a width W<NUM>. The protrusion <NUM> functions to help maintain the chain <NUM> on the chainring <NUM> (<FIG>). The protrusion <NUM> causes an overall width WO<NUM> of each of teeth 58a to be greater than the overall width WO<NUM> of each of teeth <NUM> by the extent of protrusion <NUM>.

<FIG> is another embodiment of a tooth 58b of the first group of teeth <NUM>. In particular, tooth 58b is similar to those of <FIG>, with the additional feature of an inboard or second protrusion <NUM> on the inboard side <NUM> of the tooth. The protrusion <NUM> has a width W<NUM> that is less than the width W<NUM> of the protrusion <NUM> of tooth 58a, or alternatively, greater than W<NUM>. The protrusions <NUM>, <NUM> cause an overall width WO<NUM> of each of teeth 58b to be greater than the overall width WO<NUM> of each of teeth <NUM> by the extent of protrusions <NUM>, <NUM>. Furthermore, WO<NUM> is greater than WO<NUM>.

<FIG> is yet another embodiment of a tooth 58c of the first group of teeth <NUM>. In particular, tooth 58c is similar to that of <FIG>, with an inboard or second protrusion <NUM> on the inboard side <NUM> of the tooth. The protrusion <NUM> has a width W<NUM> that is equal to the width W<NUM> of the protrusion <NUM> of tooth 58a. The protrusions <NUM>, <NUM> cause an overall width WO<NUM> of each of teeth 58c to be greater than the overall width WO<NUM> of each of teeth <NUM> by the extent of protrusions <NUM>, <NUM>. Furthermore, WO<NUM> is greater than WO<NUM>.

It will be understood that the various configurations of the teeth <NUM> include protrusions that are positioned along the side or sides of each tooth in a position where they effectively function to assist in positioning the chain on the chainring <NUM>, including positions that are adjacent or at the base of each tooth or higher on each tooth <NUM>.

<FIG> and <FIG> is an outboard side <NUM> of chainring <NUM> and the driving direction DD. The first group of teeth <NUM> is alternatingly arranged with the second group of teeth <NUM>.

The configuration of the second group of teeth <NUM> may be defined, with respect to the outboard and inboard sides <NUM>, <NUM> of each of the teeth <NUM>, by forming an inner link receiving recess <NUM> in the chainring <NUM> that represents material removed from the sides of the teeth <NUM>. The inner link receiving recess <NUM> also serves to define the cross-sectional shape of each tooth of the group of teeth <NUM>. The inner link receiving recess <NUM> defines the outboard and inboard sides <NUM>, <NUM> of each tooth and extends from the front flank <NUM> of one of the group of teeth <NUM> to a rear flank <NUM> of an adjacent one of the group of teeth <NUM> in the drive direction DD. Each inner link receiving recess <NUM> is configured to receive the length LP an inner link plate <NUM> of the chain (<FIG>). Each recess <NUM> has a base surface 72a that extends in an axial direction and a wall 72b (<FIG>) that extends radially. The base surface 72a may describe a smoothly curving contour, and may be generally in the shape of a "U".

<FIG> is the profile of each tooth of the teeth <NUM>, <NUM> in more detail. The inner link receiving recess <NUM> is formed in the chainring <NUM> and can be seen extending along the side of each tooth of the second group teeth <NUM> and extending from the load side, front or leading flank <NUM> of one of the group of teeth <NUM> to a rear flank <NUM> of an adjacent one of the group of teeth <NUM> in the drive direction DD. The recess <NUM> is configured to receive the length LP (<FIG>) of an inner link plate <NUM>. Each tooth may have a top land <NUM>. The base surface 72a may extend to the top land <NUM> of each of the teeth <NUM>. The front flank <NUM> of each tooth includes a contact zone <NUM>, where a roller <NUM> (<FIG>) contacts the tooth.

Above the contact zone <NUM> is an optional tip portion <NUM>. The roller <NUM> does not contact the tip portion <NUM> under normal driving conditions. The tip portion <NUM> may protrude forwardly from a line drawn along the contact zone <NUM> a distance T. The protruding tip portion <NUM> functions to engage a chain link earlier than a chain lacking the tip portion and provides better guiding of the chain.

An optional hook feature <NUM> is a feature that may be formed on the rear flank <NUM> of each of teeth <NUM>, <NUM>. The hook feature <NUM> is positioned along the rear flank <NUM> and may cooperate with the tip portion <NUM> to provide better guiding of the chain. The hook feature <NUM> may include a portion of the rear flank <NUM> being aligned in the radial direction R.

Turning to <FIG> the first group of teeth <NUM> and the second group of teeth <NUM> of the chainring <NUM> are arranged in an alternating fashion. An optional feature of each tooth of the first group of teeth <NUM> and second group of teeth <NUM> is a respective outer chamfer 82a, 82b. Each tooth of the first group of teeth <NUM> has an outer chamfer 82a, which may be an arcuate face formed on the outboard side <NUM> or shoulder of each tooth. Each tooth of the second group of teeth <NUM> has an outer chamfer 82b, which may be an arcuate face formed on the outboard side <NUM> or shoulder of each tooth. The outer chamfer of 82b of each tooth <NUM> may have an extent C<NUM> that is greater relative to the extent C<NUM> of the outer chamfer 82a of each tooth <NUM>.

Turning to <FIG> and <FIG> the chainring <NUM> includes chain <NUM> positioned and engaged thereon. Outer chain links <NUM> are positioned on the first group of teeth <NUM>. Inner chain links <NUM> are positioned on the second group of teeth <NUM>.

<FIG> respectively is a front view of the chainring <NUM> without a chain <NUM> and with a chain. A feature of all of the teeth <NUM>, <NUM> of the chainring <NUM> is an offset OS of the center of the tooth tip or top land <NUM> from the center line CL in a direction toward the inboard side <NUM> of the chainring. This offset feature provides better guiding of the chain to one side of the chainring.

Turning to <FIG>, a chainring <NUM> includes a number of teeth <NUM>, <NUM>. Link <NUM> of a chain engaged on the chainring <NUM> is represented by line L<NUM>, and link <NUM> and link <NUM> are represented by lines L<NUM>, L<NUM> respectively. The line of each of L<NUM>-<NUM> is drawn between the centers of the axis of each of the chain rollers <NUM>.

The hook feature <NUM> is shown on the rear flank <NUM> of each of teeth <NUM>, <NUM>. The hook feature <NUM> is positioned along the rear flank <NUM> and may cooperate with the tip portion <NUM> of the front flank <NUM> to provide better guiding of the chain. The hook feature <NUM> may include a portion of the rear flank <NUM> being aligned in the radial direction R. The hook feature <NUM> has a radially outermost extent 78a where the hook feature and the link centerlines L<NUM>-<NUM> intersect. Alternately, the outermost extent 78a may be higher than the centerlines L<NUM>-<NUM>, providing more room for the roller to engage the teeth in the driving direction. The curved line <NUM> is the path of the roller <NUM> when it disengages the tooth.

Claim 1:
A bicycle solitary chainring (<NUM>) of a bicycle front crankset and adapted for engagement with a drive chain, comprising:
a plurality of teeth (<NUM>) extending from a periphery of the chainring (<NUM>) wherein the plurality of teeth (<NUM>) are formed about the periphery of the chainring, the plurality of teeth (<NUM>) consisting of an even number;
the plurality of teeth (<NUM>) including a first group of teeth (<NUM>) and a second group of teeth (<NUM>), wherein the first group of teeth (<NUM>) and the second group of teeth (<NUM>) are equal in number, wherein each tooth of the plurality of teeth (<NUM>) includes an outboard side (<NUM>) and an inboard side (<NUM>) opposite the outboard side (<NUM>) and each tooth of the first group of teeth (<NUM>) includes at least a first protrusion (<NUM>) on the outboard side (<NUM>) and each tooth of the second group of teeth (<NUM>) is free of protrusions, wherein the overall width of each tooth of the first group of teeth (<NUM>) is wider than the overall width of the teeth of the second group of teeth (<NUM>) by the extent of the at least first protrusion (<NUM>),
wherein the teeth of the second group of teeth (<NUM>) are arranged alternatingly and adjacently between teeth of the first group of teeth (<NUM>) such that a single tooth of the first group of teeth (<NUM>) follows along the peripheral drive direction (DD) to a successive single tooth of the second group of teeth (<NUM>) and a single tooth of the second group of teeth (<NUM>) follows along the peripheral drive direction (DD) to a successive single tooth of the first group of teeth (<NUM>);
wherein each tooth of the plurality of teeth includes a tooth tip;
wherein the chainring (<NUM>) includes an outboard side (<NUM>) and an inboard side (<NUM>) opposite the outboard side (<NUM>),
wherein a feature of the teeth of the first group of teeth (<NUM>) and the second group of teeth (<NUM>) of the chainring (<NUM>) is an offset (OS) of the center of the tooth tip from the center line (CL) in a direction toward the inboard side (<NUM>) of the chainring (<NUM>), the offset feature being configured to provide better guiding of the drive chain to one side of the chainring (<NUM>).