EP0101516A1 - Automatic transmission - Google Patents

Abstract

An automatic transmission automatically changes the gear ratio in response to changes in the torque applied to an arm. A reference or tooth adjustment wheel (22) is rotated by a crank (14) connected to an arm and comprises a pair of first and second radial slots (24, 26, 28, 30) which are oriented respectively in alignment and at right angles to the arm (12). A pair of toothed chain drive segments (78, 80) have a back-and-forth movement in the aligned slots and a pair of chain sliding segments (84, 86) have a back-and-forth movement -is radial in the slots at right angles to actuate a drive chain (82). A connecting wheel or star (148) is rotatable on the crank (14) and is interconnected to the reference wheel (22) by a plurality of connections (36, 28, 40, 42), a connection being provided for each segment chain drive toothed (78, 80) and for each chain sliding segment (84, 86). A power compensation link (24) is pivotally interconnected between the arm (12) and the link wheel (148) so that rotation of the pedal arm exerts rotary forces on the link wheel. An adjustable spring (62, 206, 208) is associated with the arm (12) to permanently urge one end of a power compensation link (72) radially outward to continuously urge the link wheel (148 ) in a direction of rotation to tend to elongate the toothed drive segments (78, 80) and the chain sliding segments (84, 86). The application of the torque on the arm (12) tends to collapse the drive teeth and the chain slides by defeating the return force of the return (62, 206, 208) to automatically adjust the gear ratio. Orientation of the slots (24, 26, 28, 30) and engagement of the chain drive segments (78, 80) with the drive chain (82)

Description

AUTO ATIC TRANSMISSION

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of mechanical transmissions of the chain drive type, and more particularly, relates to an automatic transmission suitable for use with bicyles, motor gear industrial drives and the like wherein the gear ratio can be automatically varied in response to the power requirements.

Bicycle transmissions wherein the gear ratio can be automatically varied through a contractible and expandable sprocket wheel construction in response to the effort exerted upon the pedals by the cyclists are known, as exemplified by U.S. Patent No. 3,995,508. In this patent, the effective diameter of the sprocket wheel assembly is varied by changing the radial positions of a plurality of cooperating sprocket gears. The determination of the radial positions of the sprocket gears is a function of the input torque so that by increasing the torque, the effective diameter of the sprocket wheel components will be decreased. Conversely, by decreasing the input torque applied at the pedals, a continuously acting spring functions to automatically increase the effective diameter of the sprocket wheel components.

In the construction of Patent No. 3,995,508, a one way clutch had to be provided in order to allow changes in the distances between respective sprocket gears at the chain engaging locations inasmuch as the distances between the sprocket gears must vary directly with the changes in the effective wheel diameter.

All prior art automatic bicycle transmissions of which I am aware suffer from a common problem in that the increase or decrease in the effective diameter of the sprocket wheel assembly cannot be smoothly made and the engagement or disengagement of the driving sprockets and the driving chain was always accompanied by an unwanted and uncontrollable clatter or shock, a condition which is definitely detrimental when operating any bicycle transmission, and is especially so under racing conditions. Further, the prior art automatic transmissions, so far as I am aware, all suffer from a common deficiency in their inability to lock or engage the sprocket wheels in any particular radial position. Accordingly, as soon as the applied torque is removed, for example, when coasting or stopping, the associated spring would act in unopposed manner to immediately bias the sprockets to their radially expanded positions.

Additionally, the prior art automatic transmissions tended to be quite complicated and cumbersome in construction, thereby resulting in increased manufacturing costs, in increased aintainence costs, in increased weight and in interacting components that are continually subject to breakdown or wear.

In the design of my earlier filed application, U.S. Serial No. 304,207, the drive segments and chains slides were centrally connected to their respective slide blocks. Experience has now proven that there was a tendency for the chain to slip relative to the sprocket teeth during certain arcuate portions of the drive cycle, thereby allowing uncontrolled and untensioned expansion of the various segments. Additionally, under certain operating conditions, the weight of the chain itself caused the chain to pull free from the chain slide segments, an undesirable occurence. The present improvement provides structure to overcome these difficulties. SUMMARY OF THE INVENTION

The present invention relates generally to the field of automatic bicycle transmissions, and more particularly, is directed to an improved expanding sprocket assembly featuring sprocket which are capable of automatic chain engagement without clatter and which are arranged for automatic locking within any predetermined gear ratio.

The present invention, when applied to a bicycle, includes a reference wheel of fixed diameter which is arranged for rotation upon a hub which is carried on the pedal shaft and is rotated when the associated pedal arm is rotated. The reference wheel includes a pair of radial slots in substantially axial alignment with the pedal arm and a second pair of radial slots which extend at substantially right angles to the pedal arm. A plurality of separate links or a unitary small link star is coaxially connected for rotative movement relative to the reference wheel and is arranged for automatic rotation in response to torque requirements. A plurality of four pivotally connected links interconnect the outer extremities of the small link star or the separate links and the reference wheel at slide blocks positioned in the respective slots. A pair of arcuately formed, drive sprocket segments oppositely ride on slide blocks which are movable within the pedal arm aligned slots in the reference wheel and pair of arcuate, intermediate chain slide segments oppositely ride on the other slide blocks which are movable within the ninety degree angularly offset slots in the reference wheel to comprise an expandable and collapsible sprocket drive assembly.

One or more adjustable compression springs are carried upon the pedal arm to radially outwardly bias one of the slide blocks to rotate the link star in a direction to continuously urge the plurality of links to tend to push the drive sprocket segments and chain slide segments to their outermost or largest diameter positions. When the cyclist applies more power, for example, when cycling up an incline or hill, the plurality of drive sprockets and chain slides tend to automatically collapse to override the bias of the spring and to change the gear ratio as may be necessary to most efficiently proceed under the particular local road conditions. Accordingly, when the drive sprockets are radially pulled inwardly as a result of the torque imposed on the pedal arm by the cyclist, more power will be applied through the transmission to thereby increase the number of revolutions of the pedal arm relative to the rear wheel. As more power is needed, the operator will unconsciously automatically apply more energy, such as by standing upon the pedals, and the drive assembly, comprising the drive sprockets and chain slides, will then automatically collapse to override the pressue of the.springs.

The aligned and right angled orientation of the radially collapsing and expanding drive sprockets and chain slides relative to the reference wheel allows conscious, automatic locking of the drive sprockets and chain slides in any torque adjusted radial position and prevents the unintentional expansion of the effective drive wheel diameterupon release of torque on the pedal arm, until such time as the expansion is desired by the cyclist. When expansion is desired, the operator can rotate the pedals to an expansion permitting orientation whereat the compression springs will be free to bias the drive sprockets and chain slides to their respective, expanded positions. In this manner, collapsing and expanding of the effective drive diameter of the drive sprockets assembly can be completely controlled by adjusting the angular orientation of the pedal arms.

In the present improved embodiment of the invention, the timing of the drive sprockets is advanced by connecting the respective slide blocks to the drive sprockets and chain slide forwardly of their respective centers. In this manner, more o the sprocket segment teeth will be engaged in the chain in the locked and drive positions, thereby to obviate any tendancy of the chain to slip off the sprocket segments.

It is therefore an object of the present invention to provide an improved automatic bicycle transmission of the type set forth.

It is another object of the present invention to provide a novel automatic bicycle transmission which includes reference wheel that is rotated by the pedal arm and which includes pedal arm aligned slots and slots at right angles to the pedal arms for radial movement therein of a plurality of expandable and collapsible chain contacting means.

It is another of object of. the present invention to provide a novel automatic bicycle transmission including a reference wheel, a plurality of radially movable and rotatable arcuate drive sprockets, a plurality of radially movable and rotatable arcuate chain slides, means to reduce the diametrical distances between the respective drive sprockets and respective chain slides in response to the application of torque, means to continuously bias the drive sprockets and the chain slides to their radially expanded positions.

It is another object of the present invention to provide an novel automatic bicycle transmission that is simple in design, rugged in construction and trouble free when in use.

Other objects and fuller understanding of the invention will be had by referring to the following description and claims of a preferred embodiment, taken in conjunction with the accompanying drawings, wherein like reference characters refer to similar parts throughout the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a side elevational view of an automatic bicycle transmission in accordance with the present invention, partially broken away to expose interior construction details.

Fig. 2. is a partial, cross-sectional view taken along line 2-2 on Fig. 1, showing particularly the pedal arm construction, with the power compensating link partially broken away for purposes of clarity.

Fig. 3 is a schematic representation of the position of the drive sprockets and chain slide segments at the beginning o°f an expanded, locked condition.

Fig. 4 is a view similar to Fig. 3, showing the drive sprockets still in locked condition when rotated through forty-five degrees from the position of Fig. 3.

Fig. 5 is a schematic representation, showing the position of the drive sprockets and chain slide segments in a contracted, unlocked condition, and rotated through ninety degrees from the position of Fig. 4.

Fig. 6 is view similar to Fig. 5, showing the position of the drive sprockets and chain slide segments at the beginning of a locked condition, and rotated through forty-five degrees from the position of Fig. 5.

Fig. 7 is a view similar to Fig. 3, showing the position of the drive sprockets and chain slide segments at the

end of an expanded, locked condition, and rotated through ninety degrees from the position illustrated in Fig. 6.

Fig. 8 is an enlarged, partial, diagrammatic view showing the position of initial drive chain engagement on a drive sprocket.

Fig. 9 is view similar to Fig. 8 showing a second possible position of initial drive chain engagement on a drive sprocket.

Fig. 10 is an exploded, perspective view of the automatic bicycle transmission of the present invention.

Fig. 11 is a side elevational view similar to Fig. 1 showing a modified embodiment of the invention.

Fig. 11A is a view similar to Fig. 11 showing the segments in collapsed position.

Fig. 12 is a rear elevational view of the embodiment of Fig. 11.

Fig. 13 is a partly exploded, cross sectional view looking from line 13-13 on Fig. 11, looking in a direction of the arrows.

Fig. 14 is an enlarged, partial, perspective exploded view showing a segment and slide block connection detail.

OMPI DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

Referring now to the drawings, there is illustrated in Figs. 1 and 2 an automatic bicycle transmission generally designated 10 comprising a drive pedal arm 12 which is affixed in known manner to rotate the pedal crank 14 for chain drive purposes. A central hub 15 is securely affixed to the crank 14 for simultaneous rotation when the crank is rotated in known manner, for example, by employing a suitable bolt 23 and nut 25. A link means or link wheel 18 is freely rotatable about the central hub 15 at the bearing 20 to apply link imposed, radially inwardly directed and radially outwardly directed forces upon the drive sprockets 78, 80 and the chain slides 84, 86 in the manner hereinafter more fully set forth.

A sprocket adjusting wheel or reference wheel 22 is secured to the central hub 15 by the threaded nut 16 whereby the sprocket adjusting wheel 22 is rotated as the central hub 15 is rotated by the pedal arm 12 for chain drive purposes. The sprocket adjusting wheel 22 comprises a first pair of radially oriented slots 24, 26 in longitudinal alignment with the pedal arm 12 and second pair of radially oriented slots 28, 30, which slots are positioned at ninety degrees from the axis of the pedal arm 12. A plurality of openings 32 may be provided in the sprocket adjusting wheel 22 for weight reducing purposes, in known manner. As illustrated, a plurality of pivotal links or arms 36, 28, 40, 42 interconnect the link wheel 18 with the sprocket adjusting wheel 22 for automatic gear ratio adjustment purposes, as hereinafter more fully set forth. Each link or arm 36, 38, 40, 42 has its inner end pivotally connected to the link wheel 18 in a respective pivotal connection 44, 46, 48, 50 whereby each of the links is freely pivotal relative to the link wheel 18. Each of the links or arms 36, 38, 40, 42 has its other end or outer end indirectly, pivotally connnected by a respective outer pivot pin 52, 54, 56, 58 to the sprocket adjusting wheel 22. Each of the outer pivot pins 52, 54, 56, 58 respectively is affixed to one of four slide blocks 60, which blocks are preferably rectangular in configuration for linear sliding engagment within one of the longitudinally aligned slots 24, 26 or one of the perpendicularly aligned slots 28, 30. Accordingly, as the sprocket adjusting wheel 22 is rotatively urged relative to the link wheel 18 upon rotation of the hub 15 by the pedal arm 12, the rotative relative movement will be compensated at the slots 24, 26, 28, 30 by equal radial movement of the plurality of slide blocks 60 within the plurality of radially oriented slots.

Still referring to Figs. 1 and 2, the pedal arm 12 is equipped with a coil spring 62 which preferably surrounds the pedal arm and biases between an adjusting collar 64 and an L-shaped actuator lug 66. The adjusting collar 64 is threadedly engaged upon the exteriorly threaded section 68 at the base of the pedal arm 12 for threaded adjustable movement thereupon. A plurality of adjusting openings 70 may be provided in the periphery of the collar in known manner to facilitate rotation of the collar 64 upon the threads 68 when it is desired to adjust spring tension. As illustrated, the spring 62 functions to continually bias the actuator lug 66 toward its outermost position away from the crank 14 along the pedal arm 12.

The actuator lug 66 pivotally connects to one end of a power compensating link 72 at the pivot pin 97. A flattened

OMPI insert 99 cooperates with the end of the pedal arm 12 to prevent rotation of the actuator lug 66 relative to the pedal arm. The other end of the power compensating link 72 is pivotally interconnected with the link wheel 18 by the pivot pin 76. As best seen in Fig. 1, the pivot pin 76 is circularly offset from radial alignment with the outer pivot pin 97 by approximately five degrees to ten degrees whereby the bias of the spring 62, working through the lug 66 , continously tends to pull the link wheel 18 in a clockwise direction about the pedal crank 14. As hereinbefore set forth, the bearing 20 functions to facilitate rotative movement of the link wheel 18 about the pedal crank 14 and relative to the sprocket adjusting wheel 22.

As best seen in Figs. 3-7, a pair of diametrically opposed, arcuate, sprocket segments 78, 80 radially reciprocate on their respective slide blocks 60 in diametrically opposed, longitudinal alignment with the pedal arm 12. Circularly intermediate the sprocket segments 78, 80 are positioned a pair of diametrically opposed, radially adjustable chain slide segments 84, 86. The chain slide segments 84, 86 are similarly secured to slide blocks 60, which blocks are radially reciprocal within the perpendicularly aligned slots 28, 30. Accordingly, the pairs of sprocket segments 78, 80 and chain slide segments 84, 86 are movable in automatic response to the torque applied at the pedal 88 within their respective radial slots to an infinite number of radially oriented positions between a first, large diameter, low power circle 98 (Figs. 3, 4 and 7) and a collapsed, small diameter, high power circle 100, as shown in Figs. 5 and 6.

The sequence of operation and the automatic locking features of the automatic transmission 10 can best be observed in Figs. 3-7 wherein schematic views illustrate the interaction of the parts. In the rotative position illustrated in Fig. 3, the sprocket segments 78, 80 and chain slides 84, 86 are shown in their expanded or low power circle 98 orientation with theleading tooth 102 of the sprocket segment 78 engaged in a link of the drive chain 82. Simultaneously, the leading tooth 112 of the diametrically opposed sprocket segment 80 also engages a link of the chain 82. The engagement of the teeth o the diametrically opposed sprocket segments 78, 80 with spaced links of the drive chain 82 locks the system against further radial expansion or contraction. While sprockets 78, 80 are illustrated in low power circle orientation, it will be appreciated that the same locked condition between the sprocke segments 78, 80 and the chain 82 will apply for all gear ratio radial adjusted positions of the sprockets, from the full expanded orientation of Fig. 3 to the complete collapsed, high power cycle position 100 of Fig. 5.

With the pedal arms 12, 96 rotatively positioned as i Fig. 3, the horizontal forces applied to the upper run of the chain 82 will produce reaction forces at the block 60 and at the elongated radial slot 26, which reaction forces can act only radially outwardly, as indicated by the arrow 106. Accordingly, in this position, no radially inward directed force can result at the slot 26 and therefore, there is no tendency for the sprocket segments 78, 80 to collapse. In the event, that the segments 78, 80 and the chain slides 82, 84 had previously collapsed to any radial position inwardly of the full low power circle 98, the coil spring could not urge the slide block 60 in the radial outward direction indicated by the arrow 106 because of the locking action of the respective sprocket segment leading teeth 102, 112 with respective spaced links of the drive chain 82. See Fig. 6.

As the pedal arm 12 is rotated through forty-five degrees to the position illustrated in Fig. A , it will be noted that a plurality of the sprocket teeth of the sprocket segment 78 will engage respective, consecutive links in the upper run

of the chain 82. Similarly, at the this stage of the rotative a plurality of the teeth of the diametrically opposed sprocket segment 80 will also be engaged upon consecutive links in the lower run of the chain 82. Accordingly, with the teeth of the spaced sprocket segments 78, 80 engaged upon spaced links in the chain 82, the system will still be locked against further radial expansion or contraction. In this position, a reaction to all horizontal forces imposed at the chain 82 will be directed rearwardly in the direction indicated by the force arrow 104 and no forces acting in the direction of the force arrow 110 sufficient to overcome the bias forces of the spring 62, which continuously act in the direction of the force arrow 106, will be generated. Therefore, there can be no expanding or collapsing of the sprocket segments 78, 80 and the chain slides 82, 84 when the pedals are positioned as in Fig. 4.

As the pedal arm 12 is rotated through ninety degrees from the position of Fig. 4 to the position of Fig. 5, it will be noted that the teeth of the sprocket segment 78 will be engaged upon links of the chain 82 and the teeth of the diametrically opposed sprocket segment 80 will have rotated clear of the chain 82. Accordingly, there is no locking engagement in the Fig. 5 position. In this position, if the reaction forces indicated by the force arrow 110 (Fig. 4) as applied at the pedal 88 are sufficient to overcome the bias of the spring 62 acting in the direction of the force arrow 106, then the sprocket segments 78, 80 and chain slides 82, 84, acting through their respective links or arms 36, 38, 40, 42, will radially contract and cause rotation of the link wheel 18. In turn, the power compensating link 72 will be urged by rotation of the link wheel 18 to pull radially inwardly upon the actuator lug 66 to compress the coil spring 62. When the pedal arms 12, 96 are positioned to allow the reaction forces upon the chain to act radially inwardly along the longitudinally aligned slots 24, 26, then collapsing of the plurality of sprocket segments and chain slide segments can occur from the large diameter, low power circle 98 toward the small diameter, high power circle 100, if the application of pressure applied at the pedal 88 is sufficient to overcome the bias of the spring 62. In this orientation of parts, the horizontal forces applied at the upper run of the chain 82 will produce reaction forces the block 60 and at the elongated, radial slot 26 which will act radially inwardly, as indicated by the arrow 110 (Figs. 4 and 7).

If the applied torque is greater than the bias of the spring 62, then radially inwardly directed forces, acting in the direction of the arrow 110 will cause the sprocket segments 78, 80 and the chain slides 82, 84 to tend to collapse toward the high power circle 100. See Fig. 5. If the applied torque is less than the bias of the coil spring 62, then the radially outwardly directed spring forces, acting in the direction of the arrow 106, will cause the sprocket segments 78, 80 and chain slides 82, 84 to tend to expand toward the low power circle 98. As above set forth, the system will be locked against radially outward expansion or radially inward contraction whenever the teeth of both sprocket segments 78, 80 are engaged upon portions of the chain 82 as illustrated in Figs. 3, 4, 6 and 7. Collapsing of the plurality of sprocket segments 78, 80 and chain slide segments 82, 84 can only occur when radially inwardly directed forces of sufficient magnitude to overcome the bias of the spring 62, as the pedal arm 12 is moved from the position illustrated in Fig. 4 towards the position of the parts illustrated in Fig. 6 are applied. As the sprocket segments 78, 80 and chain slide segments 82, 84 radially reciprocate between the expanded and collapsed positions 98, 100, any required compensation in the length of chain 82 will be automatically adjusted by a spring biased derailleur (not shown) in the well known, usual manner.

OMPI Referring now to Figs. 8 and 9, the timing of the chain 82 automatically to a sprocket segment 78 is illustrated. As shown, it will be appreciated that the distance between the central axes of adjacent chain rollers 118, 118' will be exactly equal to the distance between adjacent segment teeth 120, 122 measured along approximately the pitch circle of the sprocket segment 78 to facilitate full engagement of the sprocket teeth with the chain rollers in well known manner. It will therefore be appreciated that the distance between the centers of adjacent chain rollers 118, 118* will be less than the circular distance between the centers of adjacent segment teeth 120, 122 measured at the respective outer faces 128 thereof. Inasmuch as it is of great importance to smooth chain engagement that the sprocket segment teeth should time exactly with the chain 82 and engage directly upon the respective rollers 118, 118' of the chain, the differences in the diameter measured at the respective pitch circle 116 of the -sprocket segments and the tooth face circle • 128 of the sprocket segments functions to cause the chain to automatically and smoothly fall into the grooves 124 defined between adjacent segment teeth 120, 122 in a smooth, chatter-free engagement.

One possible initial engagement between the leading sprocket tooth 102 and a chain roller 118 or 118' is illustrated in Fig. 9 wherein initial contact is made upon the outer face 128 of the tooth 122 by the middle of a chain roller 118, 118'. Because the distance between centers of adjacent chain rollers 118, 118' will be less than the distance between the faces of adjacent segment teeth 120, 122 measured at the face circle 128, as above set forth, then the next trailing chain roller 118' will position slightly forwardly of the rearwardly adjacent sprocket tooth 102'. Similarly, the next trailing roller 118" of the chain 82 will engage the next rearwardly adjacent tooth 102" partially upon the forward face

f O 130 whereby the rollers 118, 118', 118" will automatically be pulled downwardly into the respective grooves 124 between adjacent segment teeth in an automatic, smooth manner. It is noteworthy that the sprocket segments 78, 80 are fabricated as portions of a circle and the respective differences in the diameter between the pitch circle of a sprocket and the face circle of the sprocket functions automatically to cause the chain rollers 118, 118', 118" to fall into the sprocket grooves 124 for smooth chain engagement.

In the configuration of Fig. 8, the initial contact between the leading sprocket tooth 102 and the chain roller 118 is on the forward surface or leading face 130 of the face of the tooth 102 as illustrated. Accordingly, the next trailing roller 118' will engage the forward face of the rearwardly adjacent sprocket tooth 122' inasmuch as the distance between the adjacent rollers 118, 118' is less than the distance between the adjacent teeth 102, 122' when measured at the face circle 128. Similarly, the next reawardly spaced roller 118" will be caused to engage the next rearwardly adjacent tooth 102" more forwardly and closer to the root of the groove 124 between adjacent teeth whereby all of the rollers 118, 118* , 118" will automatically and freely seat directly within respectively adjacent sprocket teeth grooves 124. As illustrated, the teeth 102, 120', 122 of a sprocket segment 78 engage adjacent rollers 118, 118', 118" of the chain 82 smoothly and automatically and the rollers automatically fall into the sprocket grooves 124 without chatter regardless of the orientation of the initial contact between a chain roller and the leading sprocket segment 102.

In the transmission embodiment 10' illustrated in Figs. 11-14, a pedal arm 12' is secured to the pedal crank 14' through a square shank 91 and nut 132 in known manner. The pedal arm terminates in an integral central hub 15', which hub is machined or otherwise treated to provide an attaching flange 134 and an external threaded section 136. A nut 138 having internal threads 140 engages the hub threads 136 and securely clamps the pedal arms 12 to the sprocket adjusting wheel 22'. Accordingly, the pedal arm 12', the pedal crank 14' and the sprocket adjusting wheel 22* will rotate in unison. In the manner hereinbefore set forth, the sprocket adjusting wheel 22' is provided with a pair of longitudinally aligned slots 24', 26 in longitudinal alignment with the pedal arm 12 and a pair of aligned slots 28', 30' which are disposed perpendicular to the pedal arm 12. The side edges of the slots 24', 26' , 28' 30' may be protected with shoes or shields 146 to prevent wear if so desired.

As can best be seen in Figs. 12 and 13, a link star 148 comprising four points 150, 152, 154, 156 is concentric with the sprocket adjusting wheel 22' and is provided with a central opening 158. The central opening is formed of sufficient size to be freely rotatable on the cylindrical hub 160, which hub forms the inner terminus of the nut 138. It is important to note that the hub 160 is defined from the remainder of the nut 138 by a radially outwardly extending flange 162 and that the thickness of the hub is slightly greater than the thickness of the link star 148. Accordingly, when the nut 138 is tightened on the central hub threads 136 to clamp the sprocket adjusting wheel 22' to the pedal arm 12', an inward, annular channel 164 is defined between the nut flange 162 and the sprocket adjusting wheel 22'. The link star 148 is retained within and is freely rotatable within the said annular channel 164.

A plurality of links or arms 36', 38', 40', 42" have one end respectively thereof pivotally interconnected with a point 156, 150, 152, 154 of the link star 148 by utilizing suitable pivotal connectors 44*, 46', 48', 50'. The other ends

^{O PI} of the links 36', 38', 40', 42! are pivotally respectively connected to a plurality of slide blocks 60' by employing suitable pivot pins 52', 54', 56' , 58'. The blocks 60' are all similarly formed and are arranged for radial reciprocation within the slots 24', 26', 28', 30'.

As illustrated in Fig. 14, each block 60' is a sliding fit within its respective slot 24', 26', 28', 30', and each block 60' is radially moved whenever the link star 148 is rotated relative to the sprocket adjusting-wheel 22'. In the preferred embodiment, hardened steel or other suitable material shoes or shields 146 are provided along the long edges of the slots to protect against wear of the sprocket adjusting wheel 22' after prolonged periods of use. In the event of wear, only the shoes 146 need now be replaced, rather than the entire wheel 22* .

Referring now to Figs. 1, 13, and 14, a pair of arcuate, sprocket drive segments 78', 80', and a pair of chain slide segments 84', 86, are individually affixed to the plurality of slide blocks 60' by employing the pivot pin connectors 52', 54', 56', 58'. Accordingly, the segments 78', 80', 84', 86* will reciprocate along the slots 24', 26', 28', 30' as the blocks 60' are reciprocated upon relative rotation of the link star 148. In a preferred construction, the slide blocks 60' can be provided with raised tongues 166 of size to snugly fit within corresponding openings 168 provided in the segments to assure trouble free interconnections under all conditions of use.

As shown in Figs. 11 and 14, the chain drive or sprocket segments 78', 80' and the chain slide segments 84*, 86, are constructed for timing purposes to advance the interconnection between each segment and its associated slide block. Accordingly, each block 60', is connected respectively

-._f.—.__,„ ._ OM near the forward or leading edge of each of the segments. In this manner, more of the sprocket segment teeth 102', 108', 120*, 122' will be engaged in the chain rollers when the sprocket segments are rotated to their locking positions (Figs. 3, 4, 6). In order to discourage any tendency of a chain 82 to disassociated itself from the chain slide segments 84', 86' due to stretching, weight of the chain or angle of the segments, radially outwardly extending keepers 170, 172 can be provided and can be secured in known manner by employing the existing pivot pin connectors 52*, 56*.

Referring now to Figs. 11 and 15, a dual, balanced spring system 174 is illustrated in diametrical position to normally bias the segments 78', 80', 84', 86' to their outermost reciprocal positions as illustrated. The spring system 174 comprises a pair of arms 176, 178 of length to extend substantially diametrically across the sprocket adjusting wheel 22'. Each arm includes a bent connection 180, 182 which can be threaded to threadedly engage in a threaded socket 184, 186 that is provided near the outer extremety of the pedal arm 12'. The arms are provided with threaded upper shanks 188, 190 to threadedly receive the spring adjusting nuts 192, 194. The arms 176, 178 terminate in plain ends 196, 198, which ends are a sliding fit within openings 200, 202 provided in the spring block 204. A pair of easily changeable coil springs 206, 208 overfit the arms 176, 178 and bias between the adjusting nuts 192, 194 and the spring block. Accordingly, the springs 206, 208 continuously bias the spring block 204 radially outward.

As best seen in Figs. 11 and 13, the spring block 204 includes a connecting leg 210 which is undercut or otherwise configured to engage upon a spring stop or stud 212. The stud 212 extends from the pivot pin connection 58' sufficiently to provide a convenient attachment or stop for the srping block

O cwrnr i ^; ir i — _,_ _ - __ . <~~^f " - - ^ _N 204. Through the common interconnection between the spring block 204, the sprocket segment 80*, and the link star 148 at the pivotal connection 58', the bias of the springs 206, 208 will be transmitted directly through the pivotal connection 58 to continuously tend to urge the link star in a clockwise direction, as viewed in Fig. 12. It will be noted from Fig. 1 that the links 36*, 38', 40', 42*, are angularly offset from the radial orientation of the slots 24' ,.26' , 28', 30', thereb causing the rotation of the link star 148 relative to the whee 22* upon radial movement of the slide blocks 60' within their respective tracks or slots.

The springs 206, 208 are readily replaceable to accommodate stronger or weaker operators. For example, if the automatic transmission 10 were applied to a bicycle (not shown) , it can well be appreciated that an adult male rider will require stronger and heavier springs than a female rider or perhaps younger children. In order to allow the springs 206, 208 to be readily interchanged for easy adjustment to the strength of the rider, all that need to be done is to push the spring block 204 radially inwardly, thereby depressing the springs 20-6, 208 sufficiently to disengage the spring block from the extending stud 214. Then the radial pressure on the spring block can be released and the arms lifted sufficiently to allow the springs to push the block 204 over the stud 212 and past the plain ends 196, 198 of the arms 176, 178^*. With the spring block removed, the springs 206, 208 readily slide off of the free ends 196, 198 of the arms and the new heavier (or lighter) springs can be reinstalled. Replacing the spring block 204 over the plain ends 196, 198 and reengaging the spring block upon the stud 212 is all that is required to resume automatic transmission operation.

As best seen in Fig. 15, the arms 176, 178 include threaded shanks 188, 190 and adjusting nuts 192, 194 threadedly

_<_.» . _-.,«_>.__.._—. I OMPI engaged thereon. As hereinbefore set forth, the inward ends^'of the springs 206, 208 stop against the nuts 192, 194. Accordingly, by threadedly moving the nuts along the threaded shanks 188 190, the bias of the springs 206, 208 can be readily adjusted. In order to personalize the transmission 10' to the needs and strength of the user, springs with approximately the correct spring constant can be selected and placed upon the arms 176, 178. It is anticipated that this will be an experimental process and perhaps two or three different sets of springs may have to be tried until the proper springs are selected. Once springs that are closer to and that match the strength of the user are selected and positioned upon the arms 176, 178, then the adjusting nuts 192, 194 can be turned as necessary to fine tune the assembly to best satisfy the needs and wishes of the user.

It should also be appreciated that the automatic transmissions, 10, 10' of the present invention can be easily applied or "retrofitted" to most types of 5-speed or 10-speed bicycle constructions that are popularly in use not only in this country, but throughout the world. In order to apply the transmissions 10, 10' to existing bicycyles, all that is required is to remove the existing sprocket and the first and second large gears. The existing chain, deralleur, one of the pedal arms and one of the small rear gears, (without need to remove the other small gears) are reused. Once the existing sprocket is removed, the assembly 10, 10' is retrofitted upon the same pedal crank_^and is tightened in place. The existing chain is trained about the sprocket segments and the chain slide segments and adjustments as necessary can then be made to adapt the new transmission 10, 10' to the existing bicycle construction.

As can be noted in Fig. 4 and in Fig. 11, the chain slide segments and the chain drive segments terminate endwardly

OMPI in similar, radially aligned, forward and rearward ends 214, 216. When the segments are completely collapsed, as in Figs. 5 and 6, the respective radial ends 214, 216 of adjacent segments 78, 80, 78', 80' meet to form a solid wheel. Accordingly, when the segments are fully contracted, the end to end juxtaposition and contacts of the segments provides maximum strength and gives most support at precisely the time when such added strength is most needed.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.

-^URE

OMP

Claims

WHAT IS CLAIMED IS:

1. In a bicycle transmission to automatically change the gear ratio between the input and the output of the type including a pedal arm to supply rotative forces, to a drive chain, the combination of

a sprocket wheel means rotated by the pedal arm,

the sprocket wheel means comprising a sprocket adjusting wheel and a plurality of chain drive segments, the sprocket drive segments having teeth in mesh with the drive chain to impart rotative forces to the drive chain as the sprocket adjusting wheel is rotated,

the sprocket drive segments being movable relative to the sprocket adjusting wheel between expanded and contracted positions to change the gear ratio; and

means to lock the sprocket drive segments in an expanded or contracted position.

2. In the bicycle transmission of claim 1 wherein the sprocket wheel means comprises a plurality chain slide segments in sliding contact with the chain, the chain slide segments being movable relative to the sprocket adjusting wheel between expanded and contracted positions in response to the change in gear ratio.

3. The bicycle transmission of claim 1 wherein the sprocket adjusting wheel comprises a plurality of radially oriented slots and wherein the sprocket drive segments are adapted for radial reciprocation along the slots.

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4. The bicycle transmission of claim 2 wherein the sprocket adjusting wheel comprises a plurality of radially oriented slots and wherein the chain slide segments are adapted for radial reciprocation along the slots.

5. The bicycle transmission of claim 3 wherein the sprocket wheel means further comprises a link wheel directly connected for rotation by the pedal arm.

6. The bicycle transmission of claim 5 and a link pivotally interconnected between the link wheel and a sprocket drive segment.

7. The bicycle transmission of claim 4 wherein the sprocket wheel means further comprises a link wheel directly connected for rotation by the pedal arm.

8. The bicycle transmission of claim 7 and a link pivotally interconnected between the link wheel and a chain slide segment.

9. The bicycle transmission of claim 7 and a power compensating link interconnected between the link wheel and the pedal arm.

10. The bicycle transmission of claim 7 and a power compensating link interconnected between the link wheel and the pedal arm, the pedal arm including an operating spring, the spring being adapted to continuously bias the power compensating link away from the link wheel.

11. The bicycle transmission of claim 7 and a power compensating link interconnected between the link wheel and the pedal arm, the power compensating link being angularly offset from the longitudinal axis of the pedal arm.

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12. The bicycle transmission of claim 7 and a power compensating link interconnected between the link wheel and the pedal arm, the power compensating link being angularly offset from the longitudinal axis of the pedal arm by an angle of between one and ten degrees.

13. The bicycle transmission of claim 2 wherein the sprocket adjusting wheel comprises a plurality of radially oriented slots, the sprocket drive segments and the chain slide segments being adapted for radial reciprocation along the slots to change the gear ratio.

14. The bicycle transmission of claim 13 wherein the sprocket wheel means comprises a link wheel connected for direct rotation by the pedal arm.

15. The bicycle transmission of claim 14 and a plurality of links interconnected between the link wheel and the chain drive segments.

16. The bicycle transmission of claim 15 and a plurality of links interconnected between the link wheel and the chain slide segments.

17. In a bicycle transmission to change the gear ratio between the imput to a drive chain and the output of the drive chain automatically in response to changes in applied torque, the combination of

a pedal arm adapted to supply rotative forces to a pedal crank;

a reference wheel connected for direct rotation by the pedal crank,

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a plurality of chain drive sprockets in contact with the drive chain and connected for movement relative to the reference wheel along some of the slots between low gear ratio and high gear ratio positions;

a plurality of chain slide segments in contact with the drive chain and connected for movement relative to the reference wheel along some of the slots simultaneously wit the movement of the chain drive sprockets;

means to reduce the distances between the chain drive sprockets and chain slide segments in response to the application of torque upon the pedal arm; and

means to continously bias the chain drive sprockets t their high gear ratio positions.

18. The bicycle transmission of claim 17 wherein the slots are radially orientated relative to the pedal crank.

19. The bicycle transmission of claim 17 wherein the chain drive sprockets and chain slide segments circularly alternate about the reference wheel.

20. The bicycle transmission of claim 18 wherein the means to reduce comprises a link wheel adapted for rotation about the pedal crank and a plurality of links respectively interconnecting at least some of the chain drive sprockets with the link wheel.

21. The bicycle transmission of claim 18 wherein the means to reduce comprises a link wheel adapted for rotation about the pedal crank and a plurality of links, one said link interconnecting each chain drive sprocket with the link wheel.

22. The bicycle transmission of claim 21 wherein one said link interconnects each chain slide segment with the link wheel.

23. The bicycle transmission of claim 22 wherein the links are pivotally connected to the link wheel.

24. The bicycle transmission of claim 21 wherein at least one slot in positioned in longitudinal alignment with the pedal arm and another said slot is positioned at right angles to the longitudinal orientation of the pedal arm.

25. The bicycle transmission of claim 24 and a power compensating link interconnected between the link wheel and a radial outward portion of the pedal arm.

26. The bicycle transmission of claim 25 wherein the power compensating link is angularly offset from the longitudinal axis of the pedal arm.

27. The bicycle transmission of claim 26 wherein the angularity between the pedal arm and the power compensating link is between one and ten degrees.

28. The bicycle transmission of claim 26 wherein the means to continuously bias comprises a spring.

29. The bicycle transmission of claim 28 wherein the spring is adapted to continuously bias one end of the power compensating link toward the radial outward portion of the pedal arm.

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30. The bicycle transmission of claim 29 and means to adjust the bias of the spring to vary the effect of the applied torque at the link wheel.

31. The bicycle transmission of claim 28 and means to lock the chain drive sprockets in a torque adjusted gear ratio position.

32. The bicycle transmission of claim 31 wherein the means to lock comprises engaging at least ^ne tooth of each of at least a pair of spaced chain drive sprockets upon spaced portions of the drive chain.

33. The bicycle transmission of claim 31 wherein the spaced chain drive sprockets are diametrically spaced.

34. A transmission of the drive chain type to automatically change the gear ratio between the input to a drive chain and the chain output including a power arm to supply imput rotative forces, comprising

a sprocket adjusting wheel means rotated by the arm to impart rotative forces on the drive chain,

the sprocket adjusting wheel means comprising a sprocket adjusting wheel,

a plurality of chain drive segments and a plurality of chain slide segments movably carried by the sprocket adjusting wheel,

the chain drive segments having teeth in mesh with the drive chain to impart rotative forces to the drive chain as the sprocket adjusting wheel is rotated.

the chain drive segments and the chain slide segments being movable relative to the sprocket adjusting wheel between expanded and contracted positions to change the gear ratio in response to . torque changes in the input forces;

means to continously bias the chain drive segments and the chain slide segments to their said expanded positions; and

resilient means to lock the chain drive segments and the chain slide segments in an infinite number of expanded or contracted positions.

35. The transmission of claim 34 wherein the sprocket adjusting wheel comprises a first plurality of radially oriented slots, and the chain drive segments being radially reciprocated along the first slots.

36. The transmission of claims 35 wherein the sprocket adjusting wheel comprises a second plurality of radially oriented slots, the chain slide segments being radially reciprocated along the second slots.

37. The transmission of claim 36 wherein the first plurality of slots longitudinally align with the power arm and the second pluarality of slots align perpendicular to the said arm.

38. The transmission of claim 34 wherein the sprocket ajdusting wheel means further comprises a link star indirectly connected for rotation by the arm, the link star comprising at least four points.

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39. The transmission of claim 38 and links pivotally interconnected respectively between two of the link wheel points and two chain drive segments and between two of the link wheel points and two chain slide segments.

40. The transmission of claim 39 wherein the chain drive segments comprise an arcuate center and wherein the links pivotally connect to the chain drive segments at arcuate locations away from the said centers.

41. The transmission of claim 40 wherein the connections between the links and the chain drive segments are arcuately forward of the said centers.

42. The transmission of claim 37 and an operating stud carried by the chain drive segments that is furthest from a radially outward portion of the power arm, the resilient means contacting and continuously biasing the operating stud radially outwardly.

43. The transmission of claim 42 wherein the resilient means comprises a pair of spring arms each connected at one end to the power arm at the outward portion there of an a spring associated with each spring arm to bias the chain drive segments and chain slide segments radially outwardly relative to the sprocket adjusting wheel.

44. The transmission of claim 43 and a spring block slidable along the spring arms, the spring block interconnecting the power arm and the operating stud, the springs being adapted to continuously bias the spring block against the operating stud to push the attached chain drive segment radially outwardly along its associated slot.

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45. The transmission of claim 43 wherein one spring positions on each side of the power arm.

46. The transmission of claim 43 wherein the resilient means further comprises adjusting means to vary spring pressure.

47. The transmission of claim 46 wherein the adjusting means comprises threaded shanks on the spring arms and adjusting nuts threadedly engaged on the threaded shanks, the adjusting nuts contacting one end of the springs and being adapted to move toward or away from the spring block to contract or expand the springs.

48. The transmission of claims 35 and first shields lining the side of the first slots.

49. The automatic transmission of claim 48 wherein the shields are interposed between the sprocket adjusting wheel and the chain drive segments to prevent wear of the sprocket adjusting wheel.

50. The transmission of claim 48 and second shields lining the sides of he second slots.

51. The transmission of claim 34 wherein the chain slide segments comprise radially extending keepers, the keepers being adapted to maintain the drive chain in association with the chain slide segments,

52. The transmission of claim 34 whrein the chain drive segments and the chain slide segments terminate forwardly and rearwardly in radial edges.

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53. The transmission of claim 52 wherein the forward radial edge of a chain slide segment contacts the rearward radial edge of a chain drive segment when the plurality of segments are urged to their most contracted positions.

54. The transmission of claim 53 wherein the chain drive segments and the chain slide segments respectively touch in edge to edge juxtaposition when they are urged to their mos contracted positions.

55. The transmission of claim 54 wherein each segment touches two other segments to form a solid wheel when the segments are urged to their said most contracted positions.

56. The method of retrolifting an automatic transmission on a multi-speed bicycle of the type including a sprocket wheel driven by a pedal arm, at least one large gear coaxial with the sprocket wheel, a plurality of smaller gears spaced from the sprocket wheels, a chain selectively interconnecting one of the smaller gears with a large gear and a derailleur in contact with the chain, comprising

removing the pedal arm, sprocket wheel and the said at least one large gear;

installing an automatic transmission of the type comprising a pedal arm, a sprocket adjusting wheel, a plurality of chain contacting expanding and contracting segments and spring means to normally bias the segments towards their most expanded positions in the location formerly occupied by the removed parts; and

engaging the chain with one of the said plurality of smaller gears.

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