Transmission System

Abstract

A drive sprocket having a plurality of teeth for meshing with a drive member to transmit rotational motion, the drive member including a plurality of engagement pockets that engage with the teeth of the drive sprocket, each tooth having a tooth profile defined by a first side with a first engagement surface and an opposing second side with a second engagement surface, the engagement surfaces being configured such that, when driven, the teeth mesh with the engagement pockets at a first contact location on the first engagement surface and also at a second contact location on the second engagement surface, the first contact location being radially offset from the second contact location.

Description

Technical Field

[0001] The present invention relates to a transmission system including a drive sprocket and a drive member, a drive sprocket forming part of such a transmission system, and a drive member forming part of the transmission system.

[0002] Drive sprockets or pulleys having a plurality of teeth for use with a drive member such as a power transmission chain or belt are well known and often take the form of a substantially circular sprocket having a plurality of spaced teeth around its outer periphery.

[0003] With such a drive sprocket, various different drive members can be used.

[0004] A first known drive member is a power transmission chain in the form of a roller chain. The roller chain has a plurality of engagement structures that enable engagement with a drive sprocket. The engagement structure is in the form of a receiving structure for receiving the teeth of the drive sprocket. An example of the use of a roller chain is a bicycle. The roller chain of a bicycle passes around a front drive sprocket in the form of a crank drive sprocket and also around a rear drive sprocket in the form of a gear. Known roller chains can also be used in many other different types of devices, including, for example, tricycles, motorcycles, and chain saws.

[0005] A second type of known drive member is a power transmission chain including a silent chain. The silent chain also has a plurality of engagement structures that enable engagement with a drive sprocket. The engagement structure is in the form of a tooth structure that is received in a receiving recess formed between adjacent teeth on the drive sprocket. The silent chain is used in high-torque applications that require high efficiency and a lot of power transmission.

[0006] A typical application is the use of silent chains as timing chains in engines. Silent chains are also known as HY-VO chains.

[0007] A third type of known drive component is a belt adapted to engage with the teeth of a sprocket.

[0008] As is known, the drive member enables the transmission of power between drive sprockets. A known drive sprocket can drive the drive member, as in the case of a bicycle's front sprocket drive sprocket, or the drive sprocket can be driven by the drive member, as in the case of a bicycle's rear gear drive sprocket.

[0009] It is known that power transmission chains are formed by chain links that are in contact with each other in a pivotable manner by a pivot axis that extends transversely across the chain links.

[0010] Known drive members and known drive sprockets do not transmit power as efficiently as desired. More specifically, known drive members are always in contact with the drive sprocket under considerable load, and in such situations, the drive members tend to move frequently relative to the sprocket teeth while maintaining contact under this high load. As a result, known power transmission chains do not operate efficiently with respect to the drive sprocket.

[0011] Known power transmission drive members include power transmission chains or belts adapted to engage with the teeth of a drive sprocket or pulley.

[0012] For example, roller or bushing chains, or hollow pin chains which are variations of standard roller or bushing chains, are adapted to transmit rotational motion from one rotating shaft to another by meshing with the teeth of sprockets attached to each of the shafts.

[0013] A standard bushing chain has inner and outer links. The inner link has two spaced-apart inner plates connected by two bushings that are press-fitted between the plate and the bushing. The outer link has two spaced-apart outer plates connected by two pins that are press-fitted between the plate and the pin. In a standard roller chain, the bushings of the inner links pass through rollers that rotate freely around the outer surface of the bushings and are housed within the inner links by the plates of the links. In both hollow pin chains, and with standard bushings, as well as in roller chains, the links are connected by pins of the outer links that pass through the bushings of adjacent inner links. Adjacent outer and inner links can rotate relative to each other around this pin-bushing interface and carry loads simultaneously. The chain of connected links forms a loop and can articulate around multiple sprockets, transmitting torque and rotational motion between the axes of the sprockets.

[0014] A hollow pin bushing chain is similar to a standard bushing chain, except that the pins in the outer links are hollow. This configuration allows attachments to be easily mounted to the chain, primarily for conveying purposes. Attachments can be mounted by inserting pins into the hollow pins of the chain. The hollow pins also allow for a reduction in the weight of the chain while maintaining the rigidity of the components.

[0015] In known hollow pin bushing chains, each tooth of the drive sprocket is received between two adjacent bushings. Each tooth contacts one of the two adjacent bushings, and the load is transmitted between the chain and the sprocket at this contact interface.

[0016] A known drawback of such power transmission chains is that power is often not transmitted efficiently. More specifically, known power transmission drive members are always in contact with the drive sprocket under considerable load, and in such situations, the drive member tends to move frequently relative to the sprocket teeth while maintaining contact under this high load. As a result, known power transmission members do not act efficiently with respect to the drive sprocket.

[0017] In addition, when the chain links of known drive components articulate around the connecting pivot axis, friction leads to energy loss and wear of the components. This results in further efficiency losses and shortens the lifespan of the drive unit. [Overview of the Initiative]

[0018] According to a first aspect of the present invention, a drive sprocket is provided having a plurality of teeth for meshing with a drive member to transmit rotational motion, the drive member comprising a plurality of engagement pockets for engaging with the teeth of the drive sprocket, each tooth having a tooth profile defined by a first side having a first engagement surface and an opposite second side having a second engagement surface, the engagement surfaces being configured such that when driven, the teeth mesh with the engagement pockets at a first contact position on the first engagement surface and also at a second contact position on the second engagement surface, the first contact position being radially offset from the second contact position.

[0019] In this invention, during use of the drive sprocket, each tooth of the sprocket engages with the drive member at two contact positions on opposite sides of each tooth. In addition, the first contact position shifts radially from the second contact position during use.

[0020] This configuration reduces stress on the sprocket during use, thereby reducing wear and breakage of the drive sprocket and friction losses, and thereby increasing transmission efficiency.

[0021] In addition, the radial displacement of the first and second contact positions helps prevent the engagement pockets of the drive member from being pinched or caught between the teeth during use of the drive sprocket.

[0022] Thus, according to the present invention, when the drive member contacts the drive sprocket, reliable engagement between the teeth and the pitch pockets can be achieved. In addition, when a load is transmitted between the drive sprocket and the drive member, the stress on the drive sprocket is dispersed to reduce local peak stress. Further, reliable disengagement of the pitch pockets from the teeth can be achieved.

[0023] In an embodiment of the present invention, each tooth has a front face and a rear face, the shapes of the front face and the rear face are defined by the first and second sides, the shape of each face is symmetric with respect to the radial axis of the tooth, and the sides of the face are at least partially defined by two arcs. The advantage of having teeth with symmetric front and rear faces is that the drive sprocket can rotate in both the forward and reverse directions. With symmetric teeth, it is also possible to handle torque reversals during operation in an application with only one drive direction. This allows the drive sprocket to be adapted to various applications.

[0024] In an embodiment of the present invention, each arc defines a side of the tooth, has a radius R, the centers of the arcs are at a distance x from each other, and at a perpendicular distance y from the center of the drive sprocket, and the centers of each arc are at ±x / 2, y.

[0025] In an embodiment of the present invention, adjacent teeth are separated from each other by a connecting portion of the sprocket.

[0026] In such an embodiment of the present invention, the tolerance of the transmission system incorporating the drive sprocket according to the embodiment of the present invention to dimensional variations within the components of the system can be increased.

[0027] According to a second aspect of the present invention, there is provided a drive sprocket according to an embodiment of the first aspect of the present invention, and further comprising a drive member, the drive member being adapted to engage with the drive sprocket.

[0028] In an embodiment of the present invention, the drive member includes a plurality of engagement pockets, each engagement pocket having a first engagement surface and a second engagement surface spaced from the first engagement surface, the first and second engagement surfaces forming an engagement surface pair, the pair being rotatable about a rotation axis, and adjacent engagement pockets being connected to each other by a connecting member.

[0029] In an embodiment of the present invention, adjacent engagement pockets are connected to each other by a primary link, the primary link being rotatable about the rotation axis of the engagement surface pair.

[0030] In such an embodiment of the present invention, since the drive member can engage with the teeth of the drive sprocket, each engagement pocket receives the teeth of the drive sprocket and is adapted to engage with the teeth at the first and second engagement surfaces. Since adjacent engagement pockets are connected to each other by a primary link rotatable about the rotation axis of the engagement surface pair, the teeth mesh with the engagement pockets, and a first contact position can engage with the first engagement surface and a second contact position can engage with the second engagement surface.

[0031] [[ID=IS]] Thus, the teeth are firmly held by the engagement pockets such that when the teeth mesh with the engagement pockets, there is little or no movement of the teeth relative to the pockets. In addition, during use of the transmission system, since the first and second contact positions are radially offset from each other, the likelihood that the teeth will catch or be pinched within the engagement pockets is reduced compared to the case where there is no radial offset.

[0032] In an embodiment of the present invention, each primary link is rotatable about the rotation axis of each adjacent engagement pocket. This facilitates the articulation of the drive member.

[0033] In embodiments of the present invention, the drive member comprises a plurality of first primary links that are on the same plane as each other and are rotatably connected to each other at first and second pivot points, the pivot points being spaced apart from each other so that adjacent first primary links can pivot about the axis of rotation of each adjacent engagement pocket.

[0034] Such a configuration is desirable, for example, when the drive member includes a power transmission chain.

[0035] In embodiments of the present invention, the drive member comprises a plurality of second primary links that are on the same plane as each other and are rotatably connected to each other at first and second pivot points, the pivot points being spaced apart from each other so that adjacent second primary links can pivot about the axis of rotation of each adjacent engagement pocket, the first primary link is connected to the second primary link such that the first and second primary links are substantially parallel to each other, the first pivot point of the first link is coaxial with the second pivot point of the second link, and the second pivot point of the first link is coaxial with the first pivot point of the second link.

[0036] In embodiments of the present invention, each engagement pocket comprises first and second transverse members having a first end and a second end, respectively, the first and second transverse members being spaced apart from each other, and the first and second engagement surfaces being formed on the first and second transverse members, respectively.

[0037] In such embodiments, the secondary link may be parallel to the primary link, and the transverse member may be substantially perpendicular to the primary and secondary links.

[0038] In embodiments of the present invention, each engagement pocket comprises a first secondary link positioned at or near the first end of the first and second transverse members, and a second secondary link positioned at or near the second end of the transverse member, wherein the first and second secondary links are parallel to each other.

[0039] In such embodiments of the present invention, the first and second secondary links can be positioned opposite to each other such that the first and second transverse members extend substantially parallel to each other and substantially perpendicular to the first and second secondary links. Thus, each engagement pocket is defined by the first and second secondary links and the first and second transverse members.

[0040] In embodiments of the present invention, the first and second transverse members each have a radius r, the distance between the first and second members of the engagement pocket is p2, and the distance between the first and second pivot points of the primary link is p.

[0041] In embodiments of the present invention, the first and second transverse members each comprise first and second rollers, each having a radius r and being rotatable about its respective axis. In other embodiments, the first and second transverse members each comprise first and second pins, each having a radius r and being not rotatable. In yet another embodiment, the first and second transverse members comprise first and second curved surfaces having a radius of curvature r.

[0042] According to a third aspect of the present invention, a drive member is provided which forms part of a transmission system according to an embodiment of the present invention.

[0043] According to a fourth aspect of the present invention, a power transmission drive member is provided which is adapted to mesh with a drive sprocket to transmit rotational motion, the drive member comprising a plurality of engagement mechanisms, each comprising an engagement body having an engagement pocket adapted to engage with a drive sprocket, each of the engagement pockets comprising a first engagement surface and a second engagement surface spaced apart from the first engagement surface, the first and second engagement surfaces forming an engagement surface pair, the pair being rotatable about the axis of rotation of the engagement mechanism, the power transmission drive member comprising a carrier which is articulated and adapted to support the plurality of engagement mechanisms.

[0044] According to the present invention, each tooth of the drive sprocket can engage with the engagement body by contacting both the first engagement surface and the second engagement surface during use.

[0045] This configuration reduces both the stress on the sprocket during use and the relative motion between the chain and sprocket during engagement, thereby reducing wear and breakage of the drive components and drive sprocket. In addition, reduced friction loss improves transmission efficiency.

[0046] Because the carrier is articulated, the engaging body supported by the carrier can articulate around the drive sprocket during use.

[0047] In embodiments of the present invention, the first and second engaging surfaces are positioned symmetrically with respect to the axis of rotation with respect to the engaging body.

[0048] In embodiments of the present invention, the engaging surface is configured such that, when driven, the teeth of the sprocket engage with the engaging pockets at a first contact position on the first engaging surface and also at a second contact position on the second engaging surface.

[0049] In the embodiment of the present invention, the first contact position is radially shifted from the second contact position during use.

[0050] This helps prevent the engagement pocket of the drive member from getting caught or snagged on the teeth during use.

[0051] In embodiments of the present invention, the first and second engaging surfaces are formed on the first and second pins, respectively.

[0052] In some embodiments of the present invention, the pin is formed integrally with the rest of the engaging body, while in other embodiments, the pin is formed separately from the rest of the engaging body. In such embodiments, the pin can be attached to the rest of the engaging body by any convenient method, for example, by press fitting.

[0053] In some embodiments of the present invention, the first and second pins may have a circular cross-section. In other embodiments of the present invention, the cross-section of one or both of the first and second pins may be partially circular. For example, one of the first and second pins may have a semicircular cross-sectional shape, and the respective engaging surface is formed on a curved portion of the pin.

[0054] In embodiments of the present invention, each engagement mechanism includes two engagement bodies, which are spaced apart from each other.

[0055] In embodiments of the present invention, each engagement mechanism is provided with a connecting member having a first end and an opposite second end, which is attachable to one engagement body at the first end and to the other engagement body at the second end, and which extends collinearly with the rotation axis of each engagement mechanism, each engagement body of each engagement mechanism having a front and an opposite rear surface, the engagement surface of each engagement body extending from the front surface of each engagement body, the connecting member extending from the rear surface of each engagement body, and the connecting member being adapted to enable connection of each engagement mechanism to a carrier.

[0056] Since the connecting member extends between the rear surfaces of each engaging body, the connecting member can extend into the carrier to secure each engaging body to the opposite side of the carrier, and the engaging surface of each engaging body extends outward away from the carrier.

[0057] In the embodiment of the present invention, the connecting member is attached to each engaging body by press-fitting with the engaging body.

[0058] This means that each engaging body rotates together with the connecting member. The engaging body cannot rotate independently of the rotation of the connecting member.

[0059] This can be advantageous because each engaging member of the engagement mechanism rotates together with the other engaging bodies that form the respective engagement mechanism.

[0060] In another embodiment of the present invention, the connecting members may be attached to their respective engaging bodies by gap fitting.

[0061] In such embodiments of the present invention, the engaging body rotates independently and freely around the connecting member.

[0062] This may be advantageous in embodiments of the present invention where the carrier is, for example, a bush chain. Such a chain does not have hollow pins.

[0063] In embodiments of the present invention that include a connecting member, the connecting member can extend transversely through the carrier, thereby allowing a first engaging body to be positioned on a first side of the carrier and a second engaging body to be positioned on the opposite second side of the carrier.

[0064] Thus, in such embodiments of the present invention, the engaging body can face outward from the carrier, and each engaging mechanism has a first engaging body on one side of the carrier and a second engaging body on the opposite side of the carrier, so that the teeth of the drive sprocket are positioned outside the carrier.

[0065] This is in contrast to known power transmission drive components such as bushing chains, where the chain engages with the teeth of the sprocket within the chain structure.

[0066] In addition, since the connecting member is coaxial with the rotation axis of the engagement mechanism, each engaging body of the engagement mechanism is rotatable about the axis of the connecting member, and therefore both engaging bodies rotate about the same axis.

[0067] The connecting member can take any convenient form, for example, it may be equipped with a pin.

[0068] Therefore, in such embodiments of the present invention, the connecting member can be considered as the central pin of each engagement mechanism.

[0069] Each engaging body may have a receiving portion adapted to receive a connecting member, the receiving portion having an opening, the center of which is coaxial with the axis of rotation of the respective engaging mechanism.

[0070] The openings formed in each engaging body allow for rotation of the engaging body around the axis of rotation, while enabling the attachment or connection of other components to the engaging body.

[0071] In embodiments of the present invention, the carrier comprises hollow pins extending transversely across the carrier at least partially at intervals spaced apart along the length of the carrier, and each connecting member extends through the hollow pins, thereby connecting the engagement mechanism to the carrier.

[0072] In such embodiments of the present invention, the engaging bodies can be attached to each end of the connecting member such that one engaging body is on one side of the carrier and the other engaging body is on the opposite side of the carrier, and both engaging bodies are on the outside of the carrier with engaging surfaces that extend away from the carrier.

[0073] In such embodiments of the present invention, the carrier may comprise a hollow pin bushing chain.

[0074] In such embodiments of the present invention, the connecting member can be attached to each engaging body by press fit. This means that the engaging body can rotate together with the connecting member.

[0075] In other embodiments of the present invention, the carrier can take a different form and does not have to be a hollow pin bushing chain. For example, the carrier can be a standard bushing chain instead of a hollow pin bushing chain.

[0076] In such embodiments of the present invention, the carrier comprises pins extending transversely across the carrier at least partially at spaced intervals along the length of the carrier, and each connecting member comprises pins extending across the carrier between the engaging bodies of the respective engaging mechanism and through the openings of each engaging body, the pins being shaped to form interference fits with the link plates of the bush chain and clearance fits with the openings of each engaging body.

[0077] In such embodiments of the present invention, the engaging body is rotatable independently of the bushing, around the axis of each pin.

[0078] Therefore, an advantage of the present invention is that a standard chain, such as a hollow pin bushing chain, can be adapted to engage with two sprockets or a single sprocket having two sets of teeth, thereby allowing the teeth of the sprocket or the sprocket to mesh with engagement pockets positioned on the outside of the chain.

[0079] In embodiments of the present invention, the symmetrical planes of both engaging bodies may be parallel to each other so that the engaging surfaces of each engaging body are aligned with one another.

[0080] In such embodiments of the present invention, the power transmission drive member may be configured such that the teeth of the first drive sprocket engage with an engaging body on the first side of the carrier, and the teeth of the second drive sprocket mesh with two drive sprockets spaced apart from each other so as to engage with an engaging body on the second, opposite side of the carrier.

[0081] In such embodiments of the present invention, the carrier and the engagement mechanism are adapted to articulate around a drive sprocket that contacts via the engagement mechanism. Two sprockets are positioned on either side of the carrier, with the teeth of one drive sprocket engaging with the engagement body on a first side of the carrier, and the teeth of the second sprocket engaging with the engagement body on a second, opposite side of the carrier.

[0082] In some embodiments of the present invention, the power transmission drive member comprises a single drive sprocket, which comprises two sets of teeth that are spaced apart from each other.

[0083] In such embodiments of the present invention, the carrier and the engagement mechanism may be adapted to articulate around a drive sprocket that contacts via the engagement mechanism. Two sets of teeth are positioned on either side of the carrier, with the first set of teeth engaging with the engagement body on the first side of the carrier and the second set of teeth engaging with the engagement body on the second, opposite side of the carrier.

[0084] As described above, in some embodiments of the present invention, the carrier may be equipped with a standard hollow pin bushing chain or a standard bushing chain with solid pins. Such chains come in several predetermined sizes based on specific applications and international standards. The dimensions of these known chains depend on the sprocket designed to engage with a particular known chain. The main dimensions are the bushing diameter and the inner width of the chain. The inner width of the chain is the distance between the inner surfaces of the two inner plates that form the inner links of the chain.

[0085] With this invention, the teeth of the drive sprocket, or the drive sprocket itself, engage with the engagement body outside the chain, eliminating the need for the chain to interact with the sprocket teeth through conventional contact with the bushing. This means that the width of the chain can be reduced so significantly that the sprocket teeth cannot fit into the remaining space.

[0086] Furthermore, because the space typically occupied by the teeth of a conventional roller chain can be completely eliminated, the inner links of the chain can be made into a single plate. This design reduces the number of chain components and significantly reduces the chain width, which in turn reduces the required sprocket width and allows for a smaller overall system size.

[0087] In some embodiments of the present invention, the inner link may be thicker than the outer link.

[0088] In another embodiment of the present invention, the inner links of the chain may comprise a composite inner link formed from a plurality of thinner link plates. The advantage of such an embodiment is that thinner link plates can be manufactured and a composite link having the desired thickness can be easily produced by combining an appropriate number of thinner link plates.

[0089] In embodiments of the present invention, each engagement mechanism comprises first and second extension members, which are spaced apart from each other, coaxial with each other, and each having first and second end portions, the extension members extending across the width of the engagement mechanism and through each engagement body such that the first and second end portions of each extension member extend away from the carrier and from the first surface of each engagement body to form a pin, the first engagement surface of each engagement body is formed on the first and second end portions of the first extension member, respectively, and the second engagement surface of each engagement body is formed on the first and second end portions of the second extension member, respectively.

[0090] In such embodiments of the present invention, the first and second extension members serve to connect the two engaging bodies to each other, thereby forming several parts of the engaging mechanism integrally.

[0091] In such embodiments of the present invention, the power transmission drive member may be a chain formed from links, comprising a body portion and first and second legs extending from the body portion, defining a space between the legs and the body portion, each leg comprising a hollow pin receiving portion, the hollow pin receiving portion of the first leg of the link being coaxial with the axis of rotation of a first engagement mechanism, the hollow pin receiving portion of the second leg of the link being coaxial with the axis of rotation of a second, adjacent engagement mechanism, each connecting member being adapted to extend through their respective hollow pins and engagement bodies, thereby connecting the engagement bodies to the links, the space of each link providing space for such rotation so that each engagement body can rotate about its axis of rotation.

[0092] In embodiments of the present invention having an opening, the hollow pin receiving portion of the first leg of the link may be coaxial with the opening of the first engaging body, the hollow pin receiving portion of the second leg of the link may be coaxial with the opening of the second adjacent engaging body, and the hollow pin may extend through the opening of the engaging body.

[0093] According to the present invention, when the chain is under tension, little to no force is transmitted to the central pin of the engagement mechanism. This means that the central pin can rotate freely around its axis regardless of the load on the chain. This improves the efficiency of power transmission because, during engagement, the engagement mechanism rotates when it contacts the teeth, and since it rotates without placing a large load on the contact interface with the inner surface of the hollow pin chain or pin link, friction loss is greatly reduced.

[0094] On the other hand, when moving between sprockets, the engagement mechanism rotates freely with virtually no resistance, which can lead to an undesirable orientation relative to the teeth of the sprocket it engages with. In other words, instead of taking the correct position with the engagement surface on either side of the tooth, the orientation of the engagement body may cause it to catch on the tooth. If this situation occurs, it can cause undesirable vibration and wear, and when the chain tension increases enough to pull it into place, it may either snap into place to correct itself or remain stuck in an improper position, interfering with the engagement of the next engagement mechanism, thereby increasing the tension of the system and potentially causing the entire system to fail.

[0095] Therefore, in embodiments of the present invention, the carrier includes a rotation angle limiter adapted to restrict the rotation of the engagement mechanism.

[0096] The rotation angle limiter may include stoppers formed on the carrier, such as folded portions, punched portions, and punched and folded portions. Such portions provide a physical stopper to the rotational motion of the engagement mechanism.

[0097] In embodiments of the present invention, a rotation angle limiter can be formed on the links of the chain that form the carrier.

[0098] In each of the embodiments described above, each engaging body comprises an engaging pocket adapted to engage with a drive sprocket, each engaging pocket comprising a first engaging surface and a second engaging surface spaced apart from the first engaging surface, the first and second engaging surfaces forming an engaging surface pair, the pair being rotatable about the rotation axis of the engaging mechanism, and the power transmission drive member comprising a carrier, the carrier being articulated and adapted to support a plurality of engaging bodies.

[0099] According to the present invention, each tooth of the drive sprocket engages with the engagement body by contacting both the first engagement surface and the second engagement surface during use.

[0100] Thus, the engagement mechanism forming part of the present invention is a double engagement mechanism that ensures double engagement of the teeth of a sprocket that engages with a power transmission drive member according to a first aspect of the present invention.

[0101] According to a fifth aspect of the present invention, an engagement mechanism is provided which forms part of a power transmission drive member according to a first aspect of the present invention.

[0102] According to a sixth aspect of the present invention, a power transmission system is provided comprising a power transmission drive member according to a first aspect of the present invention and a drive sprocket, wherein the power transmission drive member is adapted to mesh with the drive sprocket to transmit rotational motion.

[0103] According to a seventh aspect of the present invention, a drive sprocket is provided having a plurality of teeth for transmitting rotational motion by meshing with a drive member, the drive member including a plurality of engagement pockets that engage with the teeth of the drive sprocket, each tooth having a tooth profile defined by a first side having a first engagement surface and an opposite second side having a second shaped surface, the engagement surfaces being configured such that when driven, the teeth mesh with the engagement pockets at a first contact position on the first engagement surface and also at a second contact position on the second engagement surface, the first contact position being the second contact The teeth are radially offset from their position, and each tooth has an anterior and a posterior surface, the shape of which these surfaces is defined by first and second lateral portions such that the shape of these surfaces is symmetrical with respect to the radial axis of the tooth, the first lateral portion of each surface is at least partially defined by the arc of the first surface, and the second lateral portion of each surface is at least partially defined by the arc of the second surface, and the distance between the center of the arc of the first surface of each tooth and the center of the arc of the second surface is substantially the same as the distance between the center of the arc of the first surface of the first tooth and the center of the arc of the second surface of the adjacent tooth.

[0104] Therefore, according to the present invention, not only are each teeth symmetrical and all teeth substantially the same shape, but the distance between adjacent teeth is defined by the radius of the arcs forming the arcs of the first and second faces.

[0105] In some embodiments of the present invention, the arc of the first surface forms the base portion of the first side of each tooth, the arc of the second surface forms the base portion of the second side of each tooth, and the arcs of the first and second surfaces each provide a roller seating curve.

[0106] In such embodiments of the present invention, the roller seating curve is adapted to receive a roller or other engaging portion of a drive member that is adapted to mesh with a sprocket.

[0107] In some embodiments of the present invention, each first and second side portion comprises a second portion having a convex arc extending from the respective roller seating curve toward the tip portion of the respective tooth.

[0108] In such embodiments of the present invention, the second portion including a convex arc may include an operating curve. The convex arc shape of the operating curve allows the drive member to articulate during engagement and disengagement without contacting the teeth of the sprocket.

[0109] The drive sprocket may further include support curves extending from the roller seating curve of the first tooth toward the roller seating curve of the adjacent tooth.

[0110] In such embodiments of the present invention, the support curve is adapted to receive and support the roller or other member of the drive member.

[0111] According to an eighth aspect of the present invention, a transmission system is provided comprising a drive sprocket according to an embodiment of the first aspect of the present invention, further comprising a drive member, wherein the drive member is adapted to mesh with the drive sprocket.

[0112] In embodiments of the present invention, the drive member includes a plurality of engagement pockets, each engagement pocket comprising a first engagement surface and a second engagement surface spaced apart from the first engagement surface.

[0113] In embodiments of the present invention, the drive member comprises a roller chain, and the engagement pockets are defined between adjacent rollers forming the roller chain.

[0114] The engagement pocket of the drive member is thought to be a pair of parallel cylindrical rollers, spaced at a certain distance from each other, that form a space adapted to accommodate the teeth of the drive member.

[0115] In embodiments of the present invention in which the drive member includes a roller chain, engagement pockets are defined between adjacent rollers of the roller chain.

[0116] When the occlusal pocket is engaged with a tooth, it has only one degree of freedom. This is the articular movement of the engagement pocket around the center of each roller.

[0117] In embodiments of the present invention, the roller chain has a pitch p, and the distance between the center of the arc of the first face of each tooth and the center of the arc of the second face, and the distance between the center of the arc of the first face of the first tooth and the center of the arc of the second face of the adjacent tooth are substantially equal to p.

[0118] In embodiments of the present invention, two rollers are positioned between adjacent teeth of a sprocket to form engaging pairs. This means that every other engaging pocket engages with a tooth of the sprocket, because only every other roller pair is positioned around a tooth to form an engaging pair of rollers. The remaining pairs of rollers are positioned between adjacent teeth of the sprocket, so the engaging pockets of these roller pairs do not come into contact with the teeth.

[0119] This is advantageous because only half of the roller is load-bearing while the drive member articulates on the sprocket. The other half is supportive, reducing contact load during articulation. This reduces some of the wear and friction loss in the transmission system, improving transmission efficiency.

[0120] This is in stark contrast to known sprockets used with roller chain drive members in which each roller is positioned between two adjacent teeth during sprocket operation.

[0121] In an embodiment of the present invention in which the drive member is a roller chain, the radius of each roller is substantially equal to or slightly smaller than the radius of each seating curve.

[0122] According to the present invention, the rollers of the roller chain are supported by a roller seating curve such that engagement pockets defined between adjacent rollers of the drive member engage with the teeth, thereby causing the engagement pockets to engage at two contact positions.

[0123] The dimensions of the arc defining the roller seating curve and the radius of each roller relative to that arc allow the roller chain to engage such that, during use of the transmission system, two rollers are positioned between adjacent teeth.

[0124] In addition, regardless of the number of teeth on the sprocket, the radii of the arc of the first face and the arc of the second face remain substantially the same.

[0125] This simplifies the sprocket manufacturing process.

[0126] In embodiments of the present invention, during use of the transmission system, the first roller or other drive member engagement portion may function as a load-bearing roller or portion, and the second roller or drive member portion may function as a support roller or portion. When the roller or other engagement portion acts as a support, it may be supported and received by a roller seating curve.

[0127] According to a ninth aspect of the present invention, a transmission system is provided comprising a drive sprocket and a drive member adapted to mesh with the drive sprocket, wherein the drive sprocket has a plurality of teeth for meshing with the drive member to transmit rotational motion, and the drive member has a plurality of engagement pockets adapted to engage with the teeth of the drive sprocket. Each tooth of the drive sprocket has a tooth profile defined by a first side having a first engaging surface and an opposite second side having a second engaging surface, wherein, when driven, the teeth engage with an engaging pocket at a first contact position on the first engaging surface and also at a second contact position on the second engaging surface, the first contact position being radially offset from the second contact position. The drive member comprises a roller chain having multiple spaced-apart rollers, each roller being spaced a predetermined distance from an adjacent roller and connected to an adjacent roller by a rigid connecting member extending between two adjacent rollers, thereby defining an engagement pocket between adjacent rollers. A first engagement pocket is formed by adjacent first and second rollers, a second engagement pocket is formed by a first roller and a third roller, a third engagement pocket is formed by a second roller and a fourth roller, the third roller is adjacent to the first roller, and the fourth roller is adjacent to the second roller. The angle formed between the connecting member connecting the first roller and the second roller and the connecting member connecting the first roller and the third roller includes a first joint angle, and the angle formed between the connecting member connecting the first roller and the second roller and the connecting member connecting the second roller and the fourth roller includes a second joint angle. The magnitude of the first joint angle formed when the first, second, and third rollers are all in contact with the teeth is different from the magnitude of the second joint angle formed when the first, second, and fourth rollers are all in contact with the teeth.

[0128] Accordingly, the present invention provides a transmission system in which the articulation angle of the first roller, which contacts the first tooth at the first contact point, is different from the articulation angle of the second roller, which contacts the same tooth on the opposite side of the tooth at the second contact point, when the third roller contacts the second tooth adjacent to the first tooth on the first side of the first tooth, and the fourth roller contacts the third tooth adjacent to the first tooth on the second side of the first tooth.

[0129] The drive member can be considered to have multiple joint points, and the joint angles are defined at the joint points.

[0130] In embodiments of the present invention, the connecting member comprises a link. In such embodiments of the present invention, the link articulates around an articulation point, and the articulation angle defines the angle of articulation between the first link and the second link.

[0131] In embodiments of the present invention, the rollers are arranged at each articulation point such that each tooth is engaged by two rollers, The two roller contact points are located on the opposite side of the teeth. The contact points are offset from each other in the radial direction. The distance between the centers of two adjacent rollers is always the same.

[0132] The efficiency of the sprocket is improved by having a first joint angle that is not equal to the magnitude of the second joint angle. This is because in conventional roller chains, alternating links articulate through two different types of joint movements called bush joint movement and pin joint movement. During pin joint movement, the pin of the articulated link rotates within the bush of the adjacent link, which remains stationary relative to the sprocket. During bush joint movement, the bush of the articulated link rotates within the roller around the pin of the adjacent link, which remains stationary relative to the sprocket. Thus, bush joint movement causes slippage on two surfaces during the articulation, while pin joint movement causes slippage on only one surface. This means that more energy is lost during bush joint movement than during pin joint movement. In conventional roller chains, the articulation types alternate between each articulation. With this invention, the net energy loss of the drivetrain can be reduced by reducing the size of the joint angle associated with the less efficient bush joint movement and increasing the size of the joint angle associated with the more efficient pin joint movement.

[0133] Differences in joint angles can also be used to reduce wear at the pin-bushing interface, which leads to chain elongation, also known as chain stretch. The load at the pin-bushing interface during bush joint movement is smaller than the load during pin joint movement. This means that bush joint movement leads to more wear than pin joint movement. According to the present invention, net pin-bushing wear of a drive member can be reduced by reducing the size of the joint angle associated with the joint movement of the higher-wear pin and increasing the size of the joint angle associated with the joint movement of the lower-wear bush.

[0134] In embodiments of the present invention, the first roller is a load-bearing roller, and the second roller is a support roller.

[0135] In the embodiment of the present invention, the magnitude of the first joint angle is greater than the magnitude of the second joint angle.

[0136] In embodiments of the present invention, the magnitude of every other joint angle is the same. Therefore, in such embodiments, the joint angles alternate between two values.

[0137] In embodiments of the present invention, when the first roller is a load-bearing roller and the second roller is a support roller, the first joint angle at each load-bearing roller may be the same, and the second joint angle at each support roller may be the same.

[0138] In other embodiments of the present invention, there may be different variations in the articular angles at the articular points around the sprocket. The magnitude of the articular angles can be selected to suit the conditions under which the invention is widely practiced.

[0139] In embodiments of the present invention, the shape of each tooth surface is symmetrical with respect to the radial axis of the tooth.

[0140] In embodiments of the present invention, the first side of each face is at least partially defined by the arc of the first face, and the second side of each face is at least partially defined by the arc of the second face.

[0141] In some embodiments of the present invention, the arc of the first surface forms the base portion of the first side of each tooth, the arc of the second surface forms the base portion of the second side of each tooth, and the arcs of the first and second surfaces each provide a roller seating curve.

[0142] In such embodiments of the present invention, the roller seating curve is adapted to receive a roller or other engaging portion of a drive member that is adapted to mesh with a sprocket.

[0143] In some embodiments of the present invention, each first and second side portion comprises a second portion having a convex arc extending from the respective roller seating curve toward the tip portion of the respective tooth.

[0144] In such embodiments of the present invention, the second portion including a convex arc may include an operating curve. The convex arc shape of the operating curve allows the drive member to articulate during engagement and disengagement without contacting the teeth of the sprocket.

[0145] The drive sprocket may further include support curves extending from the roller seating curve of the first tooth toward the roller seating curve of the adjacent tooth.

[0146] In such embodiments of the present invention, the support curve is adapted to receive the roller in order to support it.

[0147] In embodiments of the present invention, the roller chain comprises a plurality of inner links, each serving to connect two rollers so as to form a roller pair, and a plurality of outer links, each serving to connect pairs of rollers to one another so as to form a roller chain, thereby defining a space between the inner surfaces of opposing inner links and also between the inner surfaces of opposing outer links, and each tooth having a width that is equal to or slightly less than the distance between the inner surfaces of opposing outer links and greater than the distance between the inner surfaces of opposing inner links.

[0148] In such embodiments of the present invention, each tooth of the sprocket has a width equal to or slightly less than the distance between the inner surfaces of the opposing outer links, so that the teeth can engage with a very small gap between the outer surface of the tooth and the inner surface of the opposing outer link. The width of the teeth can also prevent the teeth from engaging between the opposing inner links, so that the sprocket can engage with teeth only between the outer links and not between the inner links. This helps to maintain the alignment of the roller chain in use.

[0149] This is in stark contrast to the situation in known transmission systems, as the width of each tooth is smaller than the distance between the inner surfaces of the opposing inner links, and for teeth of known sprockets, it is possible to mesh with either the inner or outer links of the chain. This means that when teeth of known sprockets mesh with an outer link, there is a considerable gap between the outer surface of the tooth and the inner surface of the opposing outer link.

[0150] In embodiments of the present invention, each tooth of the sprocket has a first width that is equal to or slightly less than the distance between the inner surfaces of the opposing inner links, and a second width that is equal to or slightly less than the distance between the inner surfaces of the opposing outer links.

[0151] In such embodiments, each tooth portion having a first width prevents the inner link from interfering with the teeth when the teeth engage between opposing outer links.

[0152] According to a tenth aspect of the present invention, a sprocket is provided which forms part of a transmission system according to an embodiment of the first aspect of the present invention, further comprising a drive member including a plurality of spaced-apart rollers. [Brief explanation of the drawing]

[0153] Herein, embodiments of the present invention will be described further, only illustratively, with reference to the following accompanying drawings.

[0154] [Figure 1] This is a schematic diagram of a drive sprocket according to an embodiment of the first aspect of the present invention. [Figure 2] Figure 1 is a detailed view of a part of the drive sprocket. [Figure 3] These are schematic diagrams of the drive sprockets shown in Figures 1 and 2, which engage with a drive member according to a third embodiment of the present invention and are equipped with a power chain to form a transmission system according to a second embodiment of the present invention. [Figure 4] Figure 3 is a more detailed schematic diagram of the transmission system. [Figure 5]Figures 3 and 4 are schematic diagrams showing the transmission system with the primary link from one side removed. [Figure 6] Figure 5 is a schematic diagram of a part of the transmission system, showing the position of the secondary link during rotation of the drive sprocket. [Figure 7] Figure 5 is a schematic diagram of a part of the transmission system, showing the position of the secondary link during rotation of the drive sprocket. [Figure 8] Figure 5 is a schematic diagram of a part of the transmission system, showing the position of the secondary link during rotation of the drive sprocket. [Figure 9] This is a schematic diagram showing the dimensions of the primary and secondary links of the transmission chain. [Figure 10] This is a schematic diagram showing the dimensions of the primary and secondary links of the transmission chain. [Figure 11] This is a schematic diagram showing the position of the arc center defining the side surface of the teeth of the drive sprocket relative to the center of the drive sprocket. [Figure 12] Figure 1 is a schematic diagram showing the radial offset of the first and second contact positions of the teeth of the drive sprocket. [Figure 13] Figures 1 and 2 show schematic dimensions of the drive sprockets. [Figure 14] The carrier is a power transmission drive member according to one embodiment of the present invention, comprising a hollow pin chain having multiple engaging bodies articulated around a drive sprocket. [Figure 15] Figure 14 is an exploded view of a portion of a hollow pin chain, showing the links of the chain. [Figure 16] Figure 14 is a detailed view of the links in the hollow pin chain. [Figure 17] Figure 14 is an exploded view of two engagement mechanisms that form part of the power transmission drive mechanism, showing the connecting members of each engagement mechanism passing through the pins of the hollow pin chain in Figure 14. [Figure 18] This is a schematic diagram of the engagement mechanism that forms part of the chain in Figure 14. [Figure 19]This is a schematic perspective view of an engagement body suitable for forming a part of an engagement mechanism that forms a part of a drive transmission drive member, according to an embodiment of the present invention. [Figure 20] Figure 14 is a schematic diagram of a drive sprocket suitable for engaging with the drive member. [Figure 21] This is a schematic diagram of an embodiment of a power transmission member having a width narrower than the width of the power transmission drive member in Figure 14, and articulating around a drive sprocket having a width narrower than the width of the sprocket in Figure 20. [Figure 22] This diagram schematically shows a portion of the chain in Figure 21. [Figure 23] This is a cross-sectional view of a portion of the chain shown in Figure 22, illustrating the engagement mechanism in a predetermined position. [Figure 24] This is a schematic diagram of a portion of a chain according to another embodiment of the present invention, showing an engaging body connected to a link in the chain. [Figure 25] This is a schematic diagram of the link shown in Figure 24, excluding the engaging body. [Figure 26] This is a schematic exploded view of a part of a chain according to another embodiment of the present invention, in which the inner link is formed from multiple link plates. [Figure 27] This is a schematic exploded view of a part of a chain according to another embodiment of the present invention, where the chain is a bushing chain having solid pins. [Figure 28] Figure 27 is a schematic perspective view of a portion of the chain, showing a state where the engaging body is not in its predetermined position. [Figure 29] This is a schematic exploded view of a portion of a chain forming a power transmission drive member according to another embodiment of the present invention. [Figure 30] Figure 29 is an exploded view of a part of the chain, showing the hollow pins that pass through the chain. [Figure 31] Figure 29 is a top-down perspective view of the chain portion. [Figure 32] Figure 29 is a top-down perspective view of a portion of the chain, which has an engaging surface formed from a single body extending across the width of the chain. [Figure 33]This is a schematic diagram of the outer link plate with an angle limiter. [Figure 34] This is a schematic diagram of a roller chain that engages with a sprocket according to one embodiment of the present invention and forms a transmission system according to one embodiment of the present invention. [Figure 35] Figure 34 is a schematic diagram of the transmission system with some links removed to more clearly show how the chain rollers mesh with the sprocket. [Figure 36] Figure 34 is a perspective view of a portion of the sprocket, showing the tooth profile of the sprocket teeth. [Figure 37] Figure 34 is a schematic diagram of the transmission system showing how the rollers of the roller chain mesh with the teeth of the sprocket. [Figure 38] Figure 34 is a schematic diagram of the transmission system showing where the engagement pockets are located during use of the transmission system. [Figure 39] Figure 34 is a schematic diagram showing the roller dimensions of the roller chain. [Figure 40] Figure 34 is a schematic diagram of the sprocket arc structure of the transmission system shown. [Figure 41] Figure 34 is a schematic diagram showing the movement of the roller due to wear of the drive member. [Figure 42] Figure 34 is a schematic diagram of the transmission system showing how the rollers of the roller chain mesh with the teeth of the sprocket and the joint angles. [Figure 43] This is a schematic diagram of a polygon formed by the articulation points of a sprocket that forms part of a transmission system according to one embodiment of the present invention. [Figure 44] Figure 43 is a schematic diagram of a polygon superimposed on the sprocket in Figure 42, which shows rollers arranged around the sprocket. [Figure 45] Figure 34 is a schematic diagram of a portion of the roller chain, showing the inner and outer links. [Figure 46]This is a schematic diagram of a sprocket according to another embodiment of the present invention, in which each tooth has a first width and a second width, the second width being greater than the first width. [Figure 47] Figure 45 shows a standard roller chain of the type shown in Figure 45, with the sprocket shown in Figure 46 engaged. [Modes for carrying out the invention]

[0155] Referring first to Figures 1 and 2, the drive sprocket according to an embodiment of the first aspect of the present invention is typically designated by reference numeral 10.

[0156] The sprocket 10 has a plurality of teeth 12 spaced apart from each other around the outer perimeter 14 of the sprocket 10.

[0157] Each tooth has a tooth profile defined by a first side portion 16 including a first engaging surface 18 and an opposite second side portion 20 including a second engaging surface 22. Each tooth further includes a front surface 24 and a rear surface 26, the shape of which in this embodiment is defined by the first and second sides 18, 20 including the first and second engaging surfaces. The shape of each surface is symmetrical with respect to a radial axis 28 extending along the length of each tooth.

[0158] The shape of each side portion 16, 20 is defined at least partially by an arc. Since each tooth 12 is symmetrical with respect to the axis 28, the dimensions of the arcs forming all the sides are the same.

[0159] Referring now to Figure 11, it can be seen that in this embodiment, each arc defining the side of the tooth 12 has a radius of R. The centers of the arcs are at a distance x from each other and at a perpendicular distance y from the center of the drive sprocket. The centers of each arc are ±x / 2, y. Adjacent teeth 12 are separated from each other to define a connection portion 30, as shown, for example, in Figure 2. In the exemplary embodiment, the connection portion is substantially flat. However, it should be understood that in other embodiments of the invention, the connection portion does not have to be flat, or there may be no connection portion at all.

[0160] Referring here to Figures 3-8, a transmission system according to an embodiment of a second aspect of the present invention is shown overall by reference numeral 100. The transmission system 100 comprises the sprocket 10 shown in Figures 1 and 2 and described above. The transmission system 100 further comprises a power transmission chain 110. The power transmission chain 110 is adapted to engage with the sprocket 10, as described later, in order to enable power transmission between the drive sprocket 10 and another drive sprocket (not shown).

[0161] In particular, as shown in Figures 6, 7, and 8, the power transmission chain 110 includes a plurality of engagement pockets 150 extending along the chain 110. Each engagement pocket 150 includes a first engagement surface 152 and a second engagement surface 154 spaced apart from the first engagement surface 152. The first and second engagement surfaces 152 and 154 together form an engagement surface pair 156.

[0162] Each pair of engaging surfaces 156 is rotatable about a pivot axis 158. Adjacent engaging pockets 150 are connected to each other by at least one primary link 112, which is rotatable about a pivot axis 158.

[0163] In this embodiment, there are a set of first primary links 114, a set of second primary links 116, a set of third primary links 118, and a set of fourth primary links 120, all of which are coplanar. Each set of primary links is substantially parallel to each other.

[0164] Primary links 112 in a particular set that are on the same plane are also connected to each other so as to be pivotable. Each primary link 112 has a first pivot point 122 and a second pivot point 124, and the first and second pivot points 122 and 124 are spaced apart along each primary link 112 so that adjacent primary links 112 can pivot about the first and second primary pivot points 122 and 124.

[0165] In the illustrated embodiment of the present invention, the first primary link 114 and the second primary link 116 are connected to and adjacent to each other such that the first pivot point 122 of the first primary link 114 is coaxial with the second pivot point 124 of the second primary link 116, and vice versa.

[0166] Similarly, the third primary link 118 and the fourth primary link 120 are connected to and adjacent to each other such that the first pivot point 122 of the third primary link 118 is coaxial with the second pivot point 124 of the fourth primary link 120, and vice versa.

[0167] The power transmission chain 110 further comprises a plurality of secondary links 130, each of which is adapted to rotate substantially around the pivot axis 158 of its respective engagement pocket 150. Each secondary link 130 is positioned substantially parallel to its respective primary link 112 such that the pivot axis 158 of a particular engagement pocket 150 is coaxial with the first pivot point 122 or second pivot point 124 of the corresponding primary link 112. This means that adjacent primary links 112 are pivotable around the pivot axis 158.

[0168] In this embodiment, the plurality of secondary links 132 comprises a plurality of first secondary links 138 and a plurality of second secondary links 140. Each first secondary link 138 abuts against a second primary link 116, and each second secondary link 140 abuts against a third primary link 118.

[0169] In this embodiment, two first secondary links 138 abut against each second primary link 116, and two second secondary links 140 abut against each third primary link 118.

[0170] In this embodiment of the present invention, the first secondary links 138 are substantially coplanar with each other, the second secondary links 140 are substantially coplanar with each other, and the first secondary links 138 are spaced apart from the second secondary links 140 such that each first secondary link 138 faces the corresponding second secondary link 140 to form a pair of secondary links 142.

[0171] In this embodiment, each engagement pocket 150 comprises first and second transverse members 144, 146 spaced apart from each other and having first and second engagement surfaces 152, 154 formed on them, respectively. The first and second transverse members 144, 146 extend transversely between corresponding first and second secondary links forming a pair. Thus, the transverse members 144, 146 connect the secondary links together. In this embodiment, the first and second transverse members 144, 146 each comprise a roller 148. In other embodiments, each transverse member 144, 146 may comprise a pin.

[0172] The space defined between the first and second transverse members of the secondary link forms an engagement pocket 150. The engagement pocket 150 is shaped and positioned to receive and engage the teeth 12 of the sprocket 10, as shown in the figure.

[0173] In the use of the transmission system 100, the teeth 12 of the drive sprocket 10 can engage with the engagement pocket 150 at a first contact position 160 on a first engagement surface 18 and at a second contact position 162 on a second engagement surface 20, as shown in Figure 6, for example. When engaged, the first contact position 160 engages with the first engagement surface 152 of the engagement pocket 150, and the second contact position 162 engages with the second engagement surface 154 of the engagement pocket 150.

[0174] Due to the characteristics of the transverse members 144 and 146 and the drive sprocket 10, as well as the aforementioned interrelationship between the primary and secondary links, the first contact position 160 is radially shifted from the second contact position 162 during use of the transmission system 100.

[0175] As a result, the roller 148 maintains contact with the first and second engaging surfaces 18, 20 of the corresponding teeth 12, and each secondary link 130 is seated at an offset angle such that one roller 148 is seated radially on one side of the tooth 12 higher than the roller 148 on the other side of the tooth.

[0176] The geometric shapes of the teeth 12 and the transmission chain 110 will be described in more detail with reference to Figures 9-13 in particular.

[0177] Referring first to Figures 9 and 10, a portion of the transmission chain 110 is schematically shown.

[0178] As can be seen from the figure, the distance between the first and second p pivot points 122 and 124 of the primary link 112 is p, the distance between the axes of the first and second transverse members 144 and 146 is p2, and the radius of each roller 148 is r.

[0179] Referring to Figure 11, following Cartesian coordinates where the origin is at the center of the sprocket and the centerlines of the teeth are parallel to the y-axis, we have the following:

[0180] The geometric shape of a symmetrical tooth is such that the center of the arc is

number

[0181] Furthermore, a straight line of length l extends over the teeth at an angle from the end of the arc toward the centerline, and as the γ chain wears, the chain's pitch p stretches, and the corresponding pitch circle radius, r p It increases. 1. Contact with the teeth can be maintained by both rollers, and 2. The normal contact force acting on the load-bearing upper roller remains parallel to the tension of the primary link on the high-pressure side of the chain.

[0182] Now, with reference to Figures 12 and 13, we will examine the geometric shape of the sprocket in more detail.

[0183] Equations 1 and 2 below are given by α, joint angle, and r p For an n-tooth sprocket with pitch p, the pitch circle radius is given.

number

[0184] The values ​​of the arc parameters R, x, and y are given by the solution to the set of simultaneous equations given by equations 3-6, where,

number

[0185] Referring to Figures 14-20, and first to Figure 14, a power transmission drive member according to one embodiment of the present invention is designated collectively by reference no. 100. The drive member 100 is shown to articulate around a drive sprocket 200, as shown in more detail in Figure 20. In particular, as can be seen from Figure 20, the sprocket 200 comprises a first set of teeth 210 and a second set of teeth 220. The sets of teeth 210, 220 are spaced apart from each other by the sprocket body 230. In another embodiment of the present invention, the drive sprocket 200 can be replaced by two separate sprockets, each having a single set of teeth and spaced apart from each other, so that the teeth of both sprockets engage with the drive member.

[0186] In this embodiment of the present invention, the drive member comprises a hollow pin bush chain 110 having an inner link 120 and an outer link 130, the links 120 and 130 being connected to each other by hollow pins 140, for example, as shown particularly in Figures 15 and 16.

[0187] The drive member 100 further comprises an engagement mechanism 300, particularly as shown in Figure 18. In this embodiment of the present invention, each engagement mechanism comprises two engagement bodies 310. Each engagement body 310 comprises an engagement pocket 320 adapted to engage with the drive sprocket 200. Each engagement pocket comprises a first engagement surface 330 and a second engagement surface 340 spaced apart from the first engagement surface 330. The first and second engagement surfaces 330, 340 together form a pair of engagement surfaces 350 that are rotatable around the axis of rotation of the engagement mechanism, as shown by the dotted line 360 ​​in Figure 18.

[0188] When the drive member 100 articulates with the sprocket 200, each tooth 240 of the drive sprocket 200 engages with the engaging body 310 by contacting both the first engaging surface 330 and the second engaging surface 340 of the engaging body 310. In other words, the engagement mechanism 300 is adapted to engage with each tooth 240 of the sprocket 200 using the principle of double engagement, thereby ensuring contact on both sides of each tooth 240, resulting in an energetically efficient and reliable engagement that distributes the chain load across the numerous teeth of the sprocket 200.

[0189] The first and second engaging surfaces 330 and 340 are configured such that, when driven, the teeth 240 of the sprocket 200 engage with the engaging pockets 320 of the engaging mechanism 300 at a first contact position 250 on the first engaging surface 330 and a second contact position 260 on the second engaging surface 340.

[0190] During use, the first contact position 250 is radially offset from the second contact position 260. This helps prevent the engagement pocket 320 from getting pinched or caught on the teeth 240 during use.

[0191] In this embodiment of the present invention, the first and second engaging surfaces 330 and 340 are formed on the first and second pins 280 and 290, respectively.

[0192] The pins 280 and 290 may be formed integrally with the rest of the engaging body 310.

[0193] In another embodiment of the present invention, the pins 280, 290 may be formed separately from the rest of the engaging body 310, as shown in Figure 19. In this embodiment, the engaging body 310 includes a pin opening 370, which is molded so that the pins 280, 290 can be press-fitted into the pin opening 370.

[0194] In another embodiment of the present invention, the pins 280 and 290 have a semicircular cross-section, and the engaging surfaces are formed on the curved portions of the pins 280 and 290.

[0195] In another embodiment, the first and second engaging surfaces 330, 340 are formed from folded sheet material. Alternatively, the engaging body 310 is molded to optimize engagement with the sprocket teeth 240.

[0196] Each of the engaging bodies 310 includes an opening 270, the center of which is coaxial with the rotation axis 360 of the engaging mechanism.

[0197] Each engagement mechanism 300 further comprises a connecting member 400 having a first end 410 and a second end 420. The connecting member 400 can be attached to the first engagement body 310 at the first end 410 and to the second engagement body 310 at the second end 420, so as to extend coaxially with the rotation axis of each engagement mechanism.

[0198] In this embodiment of the present invention, the first and second ends 410 and 420 of the connecting member 400 are fitted into the openings 270 of the engaging bodies 310 such that both engaging bodies 310 of the engaging mechanism 300 rotate together with the connecting member 400 around the pivot axis 360. In other words, the engaging bodies 310 cannot rotate independently of the connecting member. The openings 270 thus function as a receiving portion adapted to receive the connecting member 400.

[0199] In some embodiments of the present invention, the opening 270 is profiled. This can help in the orientation of the engaging body 310 with respect to the connecting member 400.

[0200] In this embodiment of the present invention, each connecting member 400 extends through a hollow pin 140, thereby connecting the engagement mechanism 300 to the chain 110, such that the first engagement body 310 is on one side of the chain 110 and the other engagement body 310 is on the other side of the chain. Thus, both engagement bodies 310 are outside the chain 110, the engagement surfaces extend away from the chain, and the connecting members 400 extend transversely across the chain. In addition, both engagement bodies 310 rotate around a pivot axis 360.

[0201] Accordingly, the present invention allows a standard hollow pin bushing chain to be easily adapted to engage with two sprockets, or, as in this embodiment, with a single sprocket 200 having two sets of teeth 210, 220, so that the teeth 240 of the sprocket 200 mesh with engagement pockets 320 positioned on the outside of the chain.

[0202] Referring now to Figures 21-23, it is shown that a power transmission drive member 1100 according to another embodiment of the present invention articulates around a drive sprocket 1200 having teeth 1240.

[0203] In this embodiment of the present invention, the power transmission drive member 1100 comprises a hollow pin chain 1110 that is narrower than a conventional hollow pin chain of the type shown, for example, in Figure 34. The chain 1110 comprises an inner link 1120 and an outer link 1130, similar to the links 110 and 120 of the chain 110 in Figure 3, except that the width of the chain 1110 does not need to be wide enough to accommodate the teeth of the sprocket. This is because the teeth 1240 of the sprocket 1200 engage with the outside of the chain 1110 in the same manner as described herein with respect to the embodiments shown in Figures 14-20.

[0204] Since the width of chain 1110 is narrower than the width of chain 110, the space between the teeth of the two sets of sprocket 1200 is correspondingly narrower than the space between the teeth of the two sets of sprocket 200.

[0205] In the alternative embodiments shown in Figures 24 and 25, the inner link 1120 is replaced by a single plate 1135, which comprises first and second hollow pin receiving portions adapted to receive hollow pins in a manner similar to that of the earlier embodiments described above.

[0206] In all other respects, the power transmission drive member 1100 includes corresponding components and operates similarly to the power transmission drive member 100.

[0207] Now, looking at Figure 26, another embodiment of the present invention is shown. In this embodiment, the inner link 1135 is replaced by a plurality of thinner link plates 1235 that form a composite inner link. This is advantageous from a manufacturing standpoint and also means that having a plurality of link plates 1235 allows the thickness of the composite link to be varied depending on the preferred application.

[0208] Referring now to Figures 27 and 28, another embodiment of a power transmission drive chain according to one embodiment of the present invention is shown.

[0209] In this embodiment of the present invention, the power transmission drive member comprises a bush chain 4200, the bush chain 4200 comprising solid pins 4300 extending across the width of the bush chain.

[0210] Each of the pins 4300 has pin extensions 4320 at both ends of each pin 4300. Each of the pins 4300 passes through the openings of the outer link plate 4130, the inner link plate 4120, and the bush 4150. The pins are sized and shaped such that there is an interference fit between each pin and each outer link plate 4130. Each pin extends between each engaging body 310, and each pin extension 4320 is adapted to pass through the opening 270 of each engaging body 310. Each pin extension is sized and shaped such that there is a clearance fit between each pin extension 4320 and each engaging body 310.

[0211] In such embodiments of the present invention, each engaging body 310 can rotate independently around its respective pin extension 4320.

[0212] Each pin 4300 may have a head formed at each end to prevent each engaging body 310 from disengaging from its respective pin 4300.

[0213] Referring now to Figures 29-32, a part of a power transmission drive member 2100 according to another embodiment of the present invention is shown.

[0214] In this embodiment, each engagement mechanism 2300 comprises two engagement bodies 2310 spaced apart from each other. Each engagement mechanism further comprises first and second extension members 2500, 2510, which extend through each engagement body and function to connect the two engagement bodies 2310 to each other.

[0215] Each extension member 2500, 2510 extends through the engaging body 2310 and forms pins 2280, 2290 on which the first and second engaging surfaces 2330, 2340 are formed. Thus, the first and second engaging surfaces of both engaging bodies 2310 are formed integrally.

[0216] The drive member 2100 includes a chain 2110, a part of which is shown in particular in Figure 30. The chain includes outer links 2120 and inner links 2130 connected to each other by hollow pins 2140.

[0217] Each link 2120, 2130 comprises a main body portion 2520 and a first leg 2530 and a second leg 2540 integrally formed with the main body portion 2520, extending from the main body portion 2520 and defining a space 2550 between the legs 2530, legs 2540 and the main body portion 2520. Each leg 2530, 2540 comprises a hollow pin receiving portion 2560, and each link 2120, 2130 is positionable on the engagement body 2310 such that the hollow pin receiving portion 2560 of the first leg 2530 of the link is coaxial with the rotation axis of the first engagement mechanism, and the hollow pin receiving portion 2560 of the second leg of the link is coaxial with the rotation axis of the adjacent second engagement mechanism. This means that the hollow pin receiving portion 2560 is coaxial with the opening 2270 of the engagement body 2310.

[0218] Each engagement mechanism 2300 further comprises a central pin 2570 through which the respective hollow pins 2140 pass.

[0219] Each hollow pin 2140 fits into the hollow pin receiving portion 2560 of the respective inner link 2130. The central pin 2570 extends through the hollow pins 2140 and the respective openings 2270 of both engaging bodies 2310, which are positioned on both sides of the outer link 2120.

[0220] This configuration allows the engagement mechanism to rotate around its respective axis of rotation. Space 2550 provides space for rotation.

[0221] The engagement mechanism 2300 and the engagement body 2310 are equivalent to and function similarly to the engagement mechanism 300 and the engagement body 310. In particular, the first and second engagement surfaces 2330 and 2340 form an engagement pocket 2320 equivalent to the engagement pocket 320, and thus result in double engagement of the sprocket teeth in the pitch pocket, as described with reference to the previous embodiment.

[0222] Referring now to Figure 33, a further embodiment of the outer link plate 3120 including rotation angle limiters is shown. These limiters are designed to prevent excessive rotation of the engaging body during use.

[0223] In the embodiment shown in Figure 33, the outer link plate 3120 includes a limiter 3600 formed from a bent section of the outer link plate 3120. The angle limiter 3600 restricts the rotational movement of the engaging body 3310 and thus reduces the possibility of the engaging body becoming immobile.

[0224] As described above, in this invention, each tooth of the drive sprocket engages with the engagement body by contacting both the first engagement surface and the second engagement surface. This double engagement reduces not only the relative movement between the chain and sprocket during use, but also the stress on the sprocket, thereby reducing wear and breakage of the drive member and drive sprocket. In addition, the reduction in friction loss improves transmission efficiency.

[0225] Referring here to Figures 34 and 35, a transmission system according to one embodiment of the present invention is generally shown by reference numeral 2. The transmission system comprises a sprocket 4 and a drive member having a roller chain 6.

[0226] In this embodiment of the present invention, the roller chain 6 is a standard roller chain comprising a plurality of rollers 8 that extend transversely across a transmission member and are spaced apart along the length of a drive member to form a chain. The rollers are connected to each other in known ways by links 10. The roller chain 6 can articulate between adjacent rollers 8. Engagement pockets 40 are defined between adjacent rollers 8. Each engagement pocket 40 is adapted to engage with teeth 12, as will be described in more detail below.

[0227] However, according to the present invention, during use of the transmission system 2, only every other engagement pocket 40 engages with the teeth. The remaining every other engagement pockets 40 can effectively engage with the space between adjacent teeth 12.

[0228] Referring to Figure 36, the sprocket 4 is shown in more detail.

[0229] The sprocket 4 includes multiple teeth 12, all of which are substantially identical in shape to one another. Each tooth has a tooth surface or tooth profile 14 that is symmetrical with respect to the radial axis R of the sprocket 4.

[0230] The tooth profile 14 is defined by a first side portion 16 including a first engagement surface 18 and a second side portion 20 defining a second engagement surface 22. Each of the first and second side portions 16, 20 includes a base portion 24 that forms a roller seating curve 25. Each side portion further includes a portion 26 that extends from the roller seating curve toward the tip of the tooth 28. The portion 26 is convex and defines an operating curve 29.

[0231] The sprocket 4 includes a further curve 30 that forms a support curve 31 extending between adjacent teeth.

[0232] In particular, as shown in Figures 37 and 38, in the use of the transmission system 2, every other engagement pocket 40 can engage with each tooth 12, but the remaining every other engagement pocket 40 cannot engage with a tooth. This is because, due to the dimensions of the sprocket, especially the tooth shape, relative to the dimensions of the rollers 8, when the roller chain 6 engages with the sprocket 4, two rollers 8 are positioned between adjacent teeth. This means that every other engagement pocket 40 engages with the teeth 12, and the every other engagement pocket effectively engages with the space between adjacent teeth 12 of the sprocket.

[0233] Referring to Figure 37, the manner in which the roller 8 engages with the sprocket 4 during the use of the transmission system 2 is schematically shown.

[0234] Considering a pair of rollers 8 positioned on either side of the teeth 12, one roller 32 becomes a load-bearing roller and the second roller 8 becomes a support roller 34.

[0235] The roller seating curve 25 provides the initial seating position for the engaging roller 8 of the roller chain 6. For both the load-bearing roller and the support roller, this curve helps distribute the contact load over a wider area, reducing stress on the material, at least in the initial stages when chain wear is low. The roller seating curve 25 also allows the roller to easily transition between the support position and the load-bearing position, even when the drive direction is reversed.

[0236] The load-bearing roller 32 can engage with the teeth 12 on the first engaging surface 36, and the support roller 34 can engage with the teeth on the second engaging surface 38.

[0237] The first and second engagement surfaces 36 and 38 are radially offset from each other. This allows the roller chain to contact the teeth 12 of the sprocket at two contact points 37 and 39 on the engagement surfaces 36 and 38 of each tooth of the sprocket, so that the pair of rollers 8 that engage with the teeth 12 can engage in double engagement.

[0238] Thus, the two contact points 37 and 39 are located on opposite sides of the tooth with respect to their radial centerline R, are radially offset from each other, and are therefore not symmetrical with respect to the radial centerline R.

[0239] The combination of these features results in secure engagement of the teeth of the drive sprocket by the roller chain 6, ensuring that the roller 8 does not get caught in the teeth. In addition, there is little to no relative movement between the teeth and the roller 8 while in contact.

[0240] The first contact point 37 is load-bearing and transmits the load between the roller chain 6 and the teeth 12. The second contact point 39 supports the roller chain 6 on the sprocket 4, thereby stabilizing it and increasing the load distribution across the teeth 12 of the sprocket.

[0241] As shown in Figures 36 and 37, each tooth 12 further includes an operating curve 26 that extends from the roller seating curve toward the tooth tip 28.

[0242] The operating curve 26 is convex, and the convex arc forming the operating curve 26 curves toward the tooth centerline R. The surface of the operating curve 26 is in contact with the load-bearing roller 32, enabling torque transmission between the roller chain 6 and the sprocket 4. As the chain pitch elongates due to internal wear, this surface also accommodates the rise of the load-bearing roller, as shown in Figure 40.

[0243] The tip 28 of each tooth does not need to have a pointed shape. This is because when the engagement pocket 40 is at the point of engagement with the tooth 12, it has only one degree of freedom, which is the articulation of the engagement pocket around the center of the roller.

[0244] The operating curve is the primary load-bearing contact surface located on the upper side of each tooth. This surface contacts the load-bearing roller 32, enabling torque transmission between the chain and the sprocket. As the chain pitch elongates due to internal wear, this surface also accommodates the rise of the load-bearing roller, allowing the sprocket to transmit the load throughout the chain's lifespan.

[0245] Referring again to Figure 36, the sprocket further includes a support curve 50 that extends between the roller seating curves of adjacent teeth.

[0246] The support curve is designed to accommodate the support roller 34. As the worn chain takes on a changed position on the sprocket, the support curve can also adapt to some movement of the support roller 34 over the life of the roller chain 6.

[0247] Referring particularly to Figures 37 and 38, the engagement pocket 40 is represented by line 42.

[0248] The line 42 of each engagement pocket is located with an endpoint situated on a circle 44 known as the pitch circle. The pitch circle defines the center point of all roller seating curves 25.

[0249] In this embodiment of the present invention, the radius of each roller seating curve is slightly larger than the radius of each roller. This causes the engagement pocket 40 to seat slightly off-center from the pitch circle 44. This ensures that the rollers are in their respective load-bearing and support positions and prevents the engagement pocket from catching on the teeth.

[0250] The dimensions of the roller chain 6 are shown in more detail in Figure 39.

[0251] As can be seen from Figure 39, the distance between adjacent rollers, known as the chain pitch, can be represented by the letter p, and the diameter of each roller is d. r It can be expressed as follows.

[0252] Next, referring to Figure 40, a schematic diagram of a part of the transmission system 2 in Figure 34 is shown. (Circle radius r) p ρ represents the pitch circle. This is a circle that passes through all the vertices of an n-sided regular polygon for a sprocket 4 with n / 2 teeth. The length of each side of the regular polygon is ρ. Figure 40 shows the lengths of the three sides of the regular polygon as ρ.

[0253] The radii of the arcs forming the first face arc and the second face arc are r s and can be represented by. The radius r s The center of the roller seating curve 25 having is seated at each vertex of the regular polygon forming the base of the tooth. The radius of the arc is compared to the radius of the roller and given as a ratio ρ. In addition, the steepness of the working curve with respect to the center line of the tooth at the contact point of the load-bearing roller 32 can be represented by Θ. In an embodiment of the present invention, it has been found that the ratio ρ is 1.01 regardless of the number of teeth of the sprocket 12

[0254] It has been found that Θ varies depending on the number of teeth of the sprocket

[0255] A representative but non-exhaustive list of values of Θ is shown below [Table 2]

[0256] Thus, in the transmission system according to an embodiment of the present invention, it can be seen that the tooth 12 of the sprocket 4 has an outer shape that hardly changes according to the number of teeth forming the sprocket

[0257] Thus, according to an embodiment of the present invention, a standard roller chain, for example, a roller chain that meets the ISO 606 standard, can engage with a sprocket so that double engagement is achieved

[0258] In an embodiment of the present invention where the sprocket 4 has n teeth, the roller seating arc has a constant radius r s for all n, and this radius is slightly larger than the radius of each roller 8

[0259] First, referring to FIGS. 34 and 35, a transmission system according to an embodiment of the present invention is generally indicated by reference numeral 2. The transmission system includes a sprocket 4 and a drive member including a roller chain 6

[0260] In this embodiment of the present invention, the roller chain 6 is a standard roller chain comprising a plurality of rollers 8 that extend transversely across a transmission member and are spaced apart along the length of a drive member to form a chain. The rollers are connected to each other in known ways by links 10. The roller chain 6 can articulate between adjacent rollers 8. Engagement pockets 40 are defined between adjacent rollers 8. Each engagement pocket 40 is adapted to engage with teeth 12, as will be described in more detail below.

[0261] However, according to the present invention, during use of the transmission system 2, only every other engagement pocket 40 engages with the teeth. The remaining every other engagement pockets 40 can effectively engage with the space between adjacent teeth 12.

[0262] Referring to Figure 36, the sprocket 4 is shown in more detail.

[0263] The sprocket 4 includes multiple teeth 12, all of which are substantially identical in shape to one another. Each tooth has a tooth surface or tooth profile 14 that is symmetrical with respect to the radial axis R of the sprocket 4.

[0264] The tooth profile 14 is defined by a first side portion 16 including a first engagement surface 18 and a second side portion 20 defining a second engagement surface 22. Each of the first and second side portions 16, 20 includes a base portion 24 that forms a roller seating curve 25. Each side portion further includes a portion 26 that extends from the roller seating curve toward the tip of the tooth 28. The portion 26 is convex and defines an operating curve 29.

[0265] The sprocket 4 includes a further curve 30 that forms a support curve 31 extending between adjacent teeth.

[0266] In particular, as shown in Figure 37, in the use of the transmission system 2, every other engagement pocket 40 can engage with each tooth 12, but the remaining every other engagement pocket 40 cannot engage with a tooth. This is because, due to the dimensions of the sprocket, especially the tooth shape, relative to the dimensions of the rollers 8, when the roller chain 6 engages with the sprocket 4, two rollers 8 are positioned between adjacent teeth. This means that every other engagement pocket 40 engages with the teeth 12, and the every other engagement pocket effectively engages with the space between adjacent teeth 12 of the sprocket.

[0267] Referring to Figure 37, the manner in which the roller 8 engages with the sprocket 4 during the use of the transmission system 2 is schematically shown.

[0268] Considering a pair of rollers 8 positioned on either side of the teeth 12, one roller 32 becomes a load-bearing roller and the second roller 8 becomes a support roller 34.

[0269] The roller seating curve 25 provides the initial seating position for the engaging roller 8 of the roller chain 6. For both the load-bearing roller and the support roller, this curve helps distribute the contact load over a wider area, reducing stress on the material, at least in the initial stages when chain wear is low. The roller seating curve 25 also allows the roller to easily transition between the support position and the load-bearing position, even when the drive direction is reversed.

[0270] The load-bearing roller 32 can engage with the teeth 12 on the first engaging surface 36, and the support roller 34 can engage with the teeth on the second engaging surface 38.

[0271] The first and second engagement surfaces 36 and 38 are radially offset from each other. This allows the roller chain to contact the teeth 12 of the sprocket at two contact points 37 and 39 on the engagement surfaces 36 and 38 of each tooth of the sprocket, so that the pair of rollers 8 that engage with the teeth 12 can engage in double engagement.

[0272] Thus, the two contact points 37, 39 are on opposite side portions of the tooth with respect to its radial center line R, and are radially offset from each other, and thus are not symmetric with respect to the radial center line R.

[0273] The combination of these features results in a reliable engagement of the teeth of the drive sprocket by the roller chain 6, ensuring that the rollers 8 are not pinched between the teeth. In addition, during contact, there is little or no relative movement between the teeth and the rollers 8.

[0274] The first contact point 37 is load-bearing and transmits the load between the roller chain 6 and the tooth 12. The second contact point 39 supports the roller chain 6 on the sprocket 4, thereby stabilizing it and increasing the load distribution across the teeth of the sprocket.

[0275] As shown in FIG. 37, each tooth 12 further comprises an actuating curve 26 extending from the roller seating curve towards the tip 28 of the tooth.

[0276] The actuating curve 26 is convex, and the convex arc forming the actuating curve 26 is curved towards the center line R of the tooth. The surface of the actuating curve 26 contacts the load-bearing roller 32 and enables torque transmission between the roller chain 6 and the sprocket 4. This surface also accommodates the rise of the load-bearing roller as the chain pitch elongates due to internal wear.

[0277] Referring again to FIG. 36, the sprocket further comprises a support curve 50 extending between the roller seating curves of adjacent teeth.

[0278] As described above, the rollers 8 of the roller chain 6 can articulate relative to each other via links connecting adjacent rollers.

[0279] In FIG. 44, two articulation angles a1 and a2 are shown, which will be further described. <OOC00984> The diagram shows a first roller 32 and a second roller 34 that form a first engagement pocket 401 that meshes with the first tooth 112. A third roller 322 contacts the second tooth 212 and is positioned on one side of the first roller 32. Together, the third roller 322 and the first roller 32 form a second engagement pocket 402.

[0281] The fourth roller 422 is positioned adjacent to the second roller 34 and is in contact with the third tooth 312. Together, the second and fourth rollers 34 and 422 form a third engagement pocket 403.

[0282] In this embodiment of the present invention, the first roller 32 is a load-bearing roller, and the second roller 34 is a support roller. Every other roller, starting from the load-bearing roller 32, can also be a load-bearing roller. Therefore, referring to Figure 42, the fourth roller 422 is also a load-bearing roller. This pattern can be repeated around the sprocket 4.

[0283] The first roller 32 and the third roller 322 are positioned on their respective engagement surfaces at the point where the first roller 32 contacts the first tooth 112 and the third roller 322 also contacts the second tooth 212, and the second roller 34 is positioned thereon, and the first articulation angle a1 is formed at the articulation point 400 which in this embodiment coincides with the axis of the first roller 32.

[0284] Considering the second roller 34 and the fourth roller 422, the second articular angle a2 is formed by the second roller 34 when the second roller 34 and the fourth roller 422 are in contact with their respective teeth 12, and the first roller 322 is in contact with the teeth 112.

[0285] In this example, the magnitude of the first joint angle a1 at the point defined above is greater than the second joint angle a2 at the point defined above.

[0286] Similarly, every other roller starting from the second roller 34 is a support roller. Thus, in this embodiment, the third roller 322 is also a support roller, and this pattern is repeated around the sprocket 4.

[0287] In this embodiment, every other joint angle is the same. This means that joint angle a1 is for all load-bearing rollers, and joint angle a2 is for all support rollers.

[0288] Adjacent rollers are connected to each other by links that provide a rigid connection between them.

[0289] In this embodiment, the first roller 32 is connected to the second roller 34 by link 450. The third roller 322 is connected to the first roller 32 by link 452, and the second roller 34 is connected to the fourth roller 422 by link 454.

[0290] Links 450, 452, and 454 move relative to each other, as indicated by the joint angles.

[0291] In this embodiment, the joint angles at each load-bearing roller 32, 422 are greater than the joint angles a2 at all the support rollers 34, 322, so that each load-bearing roller 332 can articulate for a longer duration than in the case of each support roller 34. This can improve the efficiency of the transmission system.

[0292] Therefore, the present invention makes it possible to achieve selective joint movement by setting the joint angles of each tooth to be different, or by following a regular pattern, as in this embodiment.

[0293] This is desirable from the standpoint of both power transmission efficiency and chain wear. Joint movement under load inevitably causes friction between adjacent chain links. This leads to both energy loss and wear of components. The magnitude of these losses is roughly proportional to the magnitude of the joint angle.

[0294] The losses associated with each joint movement are due to the alternating repetition of the inner and outer chain links in a standard power transmission roller chain. The joint movement of the outer links is more efficient than that of the inner links, but the joint movement of the inner links reduces chain elongation more effectively than that of the outer links. By using selective joint movement, the magnitude of the beneficial or detrimental effects of specific joint movements can be manipulated to improve the overall capability of the drivetrain.

[0295] In particular, as shown in Figures 43 and 44, the joint point 400 of the transmission system according to the embodiment of the present invention defines an irregular polygon 500 with sides.

[0296] In an embodiment of the present invention where the first joint angle is a1 and the second joint angle is a2, the pattern is repeated for each pair of links around the circumference of the sprocket.

[0297] Therefore, as shown in Figure 43, the relationship between these new joint angles and the original exterior angle a of the n-sided polygon is a1 + a2 = 2a.

[0298] To realize this n-sided irregular polygon, an n / 2-tooth sprocket is used, with one tooth seated between every other side vertex of the polygon. This is shown more clearly in Figure 44.

[0299] Referring here to Figures 45-47, a sprocket 904 according to another embodiment of the present invention is schematically shown. The sprocket 904 forms part of a transmission system 1002 comprising the sprocket 904 and a roller chain 6.

[0300] The portion of the transmission system 1002 equivalent to the transmission system 2 described above is given a corresponding reference number for ease of reference.

[0301] In particular, as shown in Figure 45, the roller chain 6 comprises a plurality of rollers 8. The rollers 8 are connected to adjacent rollers by inner links 810 and outer links 820.

[0302] The inner link 810 connects the two rollers 8 together to form a roller pair 850. The outer link connects the roller pair 850 together to form a roller chain 6. The distance between the inner surfaces 860 of the inner link 810 is shown by reference number d1 in Figure 45. The distance between the inner surfaces 870 of the opposing outer link 820 is shown by reference number d2. As shown in Figure 45, d2 is greater than d1.

[0303] Figures 46 and 47 provide a more detailed explanation of the sprocket 904.

[0304] The sprocket includes a plurality of teeth 12 spaced apart around the sprocket. Each tooth has a first width 914 that is equal to or slightly less than the distance between the inner surfaces of the opposing inner link 800(d1).

[0305] Each tooth 12 also has a second width 915 that is equal to or slightly less than the distance (d2) between the inner surfaces 870 of the outer link 820.

[0306] In this embodiment of the present invention, each tooth includes an intermediate tooth portion 920 and outer tooth portions 922, 924, which together define a second width.

[0307] When the sprocket 904 engages with the roller chain 6, the teeth are positioned between the two outer links, as shown in Figure 47. The width of the intermediate portion 920, along with the width of the outer tooth portions 922 and 924, is equal to or slightly less than the distance (d2) between the inner surfaces of the opposing outer links, and greater than the distance (d1) between the inner surfaces of the opposing inner links. This means that the engagement between the teeth 12 and the chain 6 is such that there is almost no gap between the teeth and the chain. Furthermore, the presence of the outer tooth portions 922 and 924 prevents the teeth from engaging between the inner links, and thus the alignment of the chain is substantially maintained during use of the drive transmission system.

[0308] In addition, the presence of the intermediate section 920 prevents the inner link from interfering with the teeth during use.

Claims

1. A drive sprocket (10) having a plurality of teeth (12) for meshing with a drive member (110) to transmit rotational motion, said drive member including a plurality of engagement pockets (150) for engaging said teeth of said drive sprocket, said teeth being integrally formed with said drive sprocket, each tooth of said plurality of teeth having a tooth profile defined by a first side (16) with a first engagement surface (18) and an opposing second side (20) with a second engagement surface (22), the engagement surfaces are configured such that, when driven, teeth engage the engagement pockets at a first contact location (160) on the first engagement surface and also at a second contact location (162) on the second engagement surface, the first contact location being radially offset from the second contact location.

2. 2. A drive sprocket as recited in claim 1, wherein each tooth (12) has a leading face (24) and a trailing face (26) whose shape is defined by said first and second sides (16, 20), said shape of each face being symmetrical about a radial axis of the tooth, and said sides of said faces being defined, at least in part, by two circular arcs.

3. 3. A drive sprocket according to claim 1 or 2, wherein adjacent teeth (12) are spaced from one another to define a connecting portion (30) of the sprocket (10).

4. 2. A drive sprocket according to claim 1, wherein each tooth (12) has a leading face (24) and a trailing face (26) the shape of which is defined by said first and second sides (16, 20) such that the shape of those faces is symmetrical about a radial axis of the tooth, the first side of each face being defined at least in part by an arc of a first face and the second side of each face being defined at least in part by an arc of a second face, and wherein a distance between a center of the arc of the first face of each tooth and a center of the arc of the second face of each tooth is substantially the same as a distance between a center of the arc of the first face of a first tooth and a center of the arc of the second face of an adjacent tooth.

5. 5. A drive sprocket as recited in claim 4, wherein the arc of the first face of each tooth (12) comprises a base portion of the first side (16) of the tooth and the arc of the second face of each tooth forms a base portion of the second side (20) of the respective tooth, the arcs of the first and second faces each comprising a roller seating curve.

6. 6. A drive sprocket as claimed in claim 4 or 5, wherein each of the first and second sides (16, 20) includes a second portion that includes a convex arc extending from the respective roller seating curve towards a tip portion of the respective tooth (12).

7. A drive sprocket according to any one of claims 4 to 6, further comprising a support curve extending from the roller seating curve of a first tooth towards the roller seating curve of an adjacent tooth (12).

8. A transmission system comprising a drive sprocket (10) according to any one of claims 4 to 7, and a drive member (110) adapted to mesh with said drive sprocket.

9. 9. The transmission system of claim 8, wherein the drive member (110) comprises a roller chain, adjacent rollers forming the roller chain defining a plurality of engagement pockets (150), each of the engagement pockets comprising a first engagement surface (152) and a second engagement surface (154) spaced from the first engagement surface, and preferably wherein the roller chain has a pitch p, and the distance between the center of arc of the first face of each tooth and the center of arc of the second face, and the distance between the center of arc of the first face of a first tooth and the center of arc of the second face of an adjacent tooth, are substantially equal to p.

10. A transmission system comprising a drive sprocket according to claim 1 and a drive member adapted to mesh with the drive sprocket (10), the drive member comprises a roller chain having a plurality of spaced apart rollers (32, 34, 322, 422), each roller being spaced from an adjacent roller by a predetermined distance and connected to the adjacent roller by a rigid connecting member (450, 452, 454) extending between two adjacent rollers, whereby the engagement pocket is defined between the adjacent rollers; a first engagement pocket (401) is formed by first and second rollers (32, 34) adjacent to each other, a second engagement pocket (402) is formed by the first roller (32) and a third roller (322), a third engagement pocket (403) is formed by the second roller (34) and a fourth roller (422), the third roller being adjacent to the first roller and the fourth roller being adjacent to the second roller; an angle formed between a connecting member connecting the first roller and the second roller and a connecting member connecting the first roller and the third roller includes a first joint angle, and an angle formed between the connecting member connecting the first roller and the second roller and a connecting member connecting the second roller and the fourth roller includes a second joint angle; a magnitude of the first articulation angle formed when the first, second and third rollers all contact a tooth is different from a magnitude of the second articulation angle formed when the first, second and fourth rollers all contact a tooth.

11. The transmission system of claim 10, wherein the drive member (110) comprises a plurality of articulation points, and the articulation angles are defined at the articulation points.

12. 12. A transmission system according to claim 10 or 11, wherein the first roller comprises a load-bearing roller and the second roller comprises a support roller.

13. A transmission system according to any one of claims 10 to 12, wherein the magnitude of the first joint angle is greater than the magnitude of the second joint angle.

14. A transmission system according to any one of claims 10 to 13, wherein every other joint angle has substantially the same magnitude.

15. 15. A transmission system according to any one of claims 10 to 14, wherein the roller chain comprises a number of inner links (120), each serving to connect two rollers to form a roller pair, and a number of outer links (130), each serving to connect a roller pair to each other to form the roller chain, whereby a space is defined between the inner surfaces of the opposing inner links and also between the inner surfaces of the opposing outer links, each tooth (12) of the sprocket teeth having a width that is the same as or slightly smaller than the distance between the inner surfaces of the opposing outer links and greater than the distance between the inner surfaces of the opposing inner links, and optionally each tooth of the sprocket comprises a first width that is the same as or slightly smaller than the distance between the inner surfaces of the opposing inner links and a second width that is the same as or slightly smaller than the distance between the inner surfaces of the opposing outer links.

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