GB2159593A - Multi-ratio drive - Google Patents

Abstract

A multi-ratio drive (10) has a first sprocket (12) having a first plate (41) with a plurality of concentric circular rows of holes (63) therein for receiving pins in a fully retracted position, a second plate (60) spaced from the first plate (41) and coaxial therewith, a shifting mechanism (70) for moving the retracted pins in a predetermined row from their retracted position to an extended position while causing any pins outside of the predetermined row to remain in a retracted position, a flexible chain (40) having a plurality of spaced links (103, 104) each with a concave configuration (106) for encircling the extended pins to thereby provide a driving engagement with the extended pins. A second sprocket (20) which is spaced from the first sprocket (12) also engages the chain (40) so that a multi-ratio drive is provided between the sprockets (12,20). The sprocket (20) may be fixed or of similar construction to the first sprocket (12). The means for moving the pins may be magnetic. <IMAGE>

Description

SPECIFICATION Multi-ratio drive The present invention relates to a multi-ratio drive particularly for use on bicycles, motorcycles, automobile transmissions, and any other type of device wherein a multi-ratio drive is required.

By way of background, in various applications, such as bicycles, multi-ratio drives are desirable. However, in the past multi-ratio drives were either limited in the number of drive ratios which were obtainable, as in 10 or 1 5 speed bicycle drives, or, where the drives were infinitely variable, such as in drives utilizing spaced cones, the drive either occupied a relatively large volume, and was therefore impractical for certain applications, or the drive was so complex as to be impractical.

In US-1428999-A a multi-ratio drive is disclosed in which two sprockets are interconnected by a flexible chain made up of links which engage with elements which are selectively extended from one of the sprockets. The elements are moved into and out of their chain engaging positions by an elaborate mechanical arrangement which also requires rotation of the elements about their own axes as they move axially from a retracted to an extended position and also as the sprocket carrying them rotates. Such an arrangement is bulky and subject to wear due to the friction caused as the elements are moved and rotated.

The present invention provides a multi-ratio drive comprising first and second sprockets, an endless flexible member co-operable with said sprockets to transmit motion therebetween, a plurality of openings in the first sprocket arranged in concentric rows, a pin associated with each opening, and means for shifting each pin between a retracted and an extended position, wherein said shifting means moves the pins solely in an axial direction and in that the pins and sprocket rotate together as a unit in use.

The invention further provides a variable diameter sprocket comprising disc means, a plurality of concentric circular rows of holes in said disc means, axially movable pins in said holes, and means for selectively shifting the pins to cause said pins of certain of said rows to move between retracted positions in said disc means to extended positions wherein they project outwardly from said disc means a greater amount than when in said retracted positions, and means for mounting said axially movable pins for rotation with said disc means without rotation about their axes as said disc means rotates, wherein said moving means moves said pins substantially solely in their axial directions.

The invention also provides a multi-ratio drive comprising two sprockets each engagable with an endless chain, a plurality of openings in at least one of said sprockets defining a series of concentric rings of openings, pins movably mounted in said opening, and means for shifting the pins in at least one of the rings so that they project from the sprocket and engage the chain, wherein the shifting means and the pins magnetically interact to move the pins axially only between extended and retracted positions.

It will be appreciated that the above-defined drives and sprockets are advantageously efficient at providing a large number of drive ratios in a simple construction which can also be utilised to modify existing equipment.

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevational view of a bicycle mounting a multi-ratio drive of the present invention; Figure 2 is a fragmentary side elevational view of the multi-ratio drive of Figure 1 in enlarged detail; Figure 3 is a cross sectional view taken substantially along line 3-3 of Figure 2 and showing the manner in which a shifting mechanism is mounted on the fork of a bicycle; Figure 4 is a fragmentary cross sectional view taken substantially along line 4-4 of Figure 2 and showing the shifting mechanism in relationship to a pin-carrying sprocket; Figure 5 is a fragmentary enlarged view of the encircled portion of Figure 4 showing in greater detail a pin and sprocket mechanism;; Figure 6 is a side elevational view of a portion of the sprocket showing the plurality of concentric series of pin-openings therein; Figure 7 is a fragmentary side elevational view of the chain which encircles the pins in the sprocket; Figure 8 is a fragmentary cross sectional view taken substantially along line 8-8 of Figure 7; Figure 9 is a fragmentary cross sectional view similar to Figure 4 but showing a modified form of shifting mechanism and sprocket wheel utilizing magnets to effect the shifting; Figure 9A is a schematic view of a shifting mechanism similar to Figure 9 but utilizing electromagnets to effect the shifting; Figure 10 is a fragmentary cross sectional view similar to Figure 9 but showing a modified shifting mechanism and sprocket which utilizes mechanical contact to shift the pins; Figure 11 is an enlarged view of the encircled portion of Figure 10;; Figure 1 2 is a plan view of a modified multi-ratio drive utilizing two large sprockets capable of providing approximately 1 61 different speeds and also showing in phantom the rear forks of a bicycle relative to which it is mounted; Figure 1 3 is a fragmentary cross sectional view taken substantially along line 13-13 of Figure 1 2 and showing a rear axle and drive construction which permits a large sprocket to be mounted on a bicycle having a conventional rear fork; Figure 14 is a fragmentary cross sectional view similar to Figure 5 but showing a modified type of pin construction;; Figure 1 5 is a fragmentary cross sectional view taken substantially along line 1 5-1 5 of Figure 14 and showing an O-ring construction on the pin for maintaining the pin in the position to which it is moved; Figure 16 is a side elevational view of the rear sprocket of a conventional 10-speed bicycle; Figure 1 7 is a cross sectional view taken substantially along line 1 7-1 7 of Figure 16; Figure 1 8 is a side elevational view, taken substantially along line 18-18 of Figure 19, of a small pin-carrying sprocket mounted on a rear hub of a conventional 10-speed bicycle for replacing five conventional sprockets; Figure 1 9 is a fragmentary cross sectional view taken substantially along line 1 9-1 9 of Figure 18;; Figure 20 is a side elevational view of a modified form of pin-carrying sprocket in which a pedalsupporting crankarm is cast integrally with the sprocket; Figure 21 is a schematic view showing the chain encircling protruding pins defining a circle of relatively small diameter; Figure 22 is a view similar to Figure 21 but showing the transition as the chain assumes engagement with a circle of pins of larger diameter while retaining engagement with the circle of pins of smaller diameter; Figure 23 is a view similar to Figure 22 but showing a further step in the transition process; Figure 24 is a view similar to Figure 23 but showing the chain engaging the circle of pins of greater diameter after the transition has been completed;; Figure 25 is a view similar to Figure 24 but showing a shifting mechanism moved to cause pins of the smaller diameter circle to protrude and the pins of the larger diameter circle to progressively retract; Figure 26 is a view similar to Figure 25 but showing the chain starting to engage the circle of pins of smaller diameter while retaining engagement with the circle of pins of larger diameter; Figure 27 is a view to Figure 26 but showing a further step in the transition as the chain moves onto the smaller diameter circle of pins; and Figure 28 is a view similar to Figure 27 but showing the chain in full engagement with the smaller diameter circle of pins.

A multi-ratio drive 10 is shown mounted on bicycle 11. It will be appreciated, however, that the multi-ratio drives of the present invention may be used in other applications, such as motorcycles, automobile transmissions and for any other use wherein variable drive ratios are required.

The multi-ratio drive 10 includes a pincarrying sprocket 1 2 keyed to shaft 1 3 which is journalled for rotation in hub 14 (Fig.4) located at the junction of frame members 1 5 and 1 6. Crankarms 1 7 and 1 9 are nonrotatably coupled to shaft 1 3 in any suitable manner. Sprocket 12 and crankarms 1 7 and 1 9 may be substituted for the conventional sprocket and crankarms on an existing bicycle. It will be appreciated that by rotating crankarms 1 7 and 1 9 in the conventional manner pin-carrying sprocket 1 2 will also be rotated.A second pin-carrying sprocket 20 (Figs. 2 and 19) is mounted on shaft 21 instead of the conventional five sprocket wheels (Figs. 1 6 and 1 7) which are normally mounted on this shaft to provide 10-speed operation. The conventional structure is shown in Figure 1 7 wherein a one-way clutch 22 is threaded onto enlarged portion 23 of shaft 21 at 24. The one-way clutch 22 may be of the type generally known as a free wheel" which locks when the shaft 21 is being driven in a clockwise direction in Figure 2 but which free wheels when the sprockets are being driven in a counterclockwise direction.The conventional sprocket arrangement shown in Figure 1 7 includes sprocket wheels 25, 26, 27, 29 and 30. 8prockets 25, 26 and 27 are slid onto enlarged surface 31 of free wheel 22 and are suitably keyed thereto.

Spacers 32 and 33 are positioned between the sprocket wheels as shown and a lip 34 prevents sprocket wheel 25 from moving to the right in Figure 1 7. A spacer 35 abuts sprocket wheel 27 and shoulder 36' and sprocket wheels 29 and 30 are threaded onto reduced portion 36 at 37 to lock the five sprockets in position.

In order to mount sprocket 20 (Figs.2 and 19) on shaft 21, sprocket wheels 29 and 30 are unscrewed and thereafter sprocket wheels 27, 26 and 25 are slid off surface 31.

Thereafter, the pin-carrying sprocket 20 is threaded onto reduced portion 36. Thus, the free wheel 22 will function in the same manner as it does on a conventional 10-speed bicycle but the pin-carrying sprocket 20 can be used to receive the special type of chain 40 (Figs. 2, 7 and 8) which encircles pincarrying sprockets 1 2 and 20 to effect a drive therebetween.

As shown in Figure 19, sprocket 20 has three concentric circular rows of holes 100, 101 and 102 in disc 103' and there are three corresponding aligned rows of holes 100', 101' and 102' in disc 104" (Fig.18) which is spaced from disc 103'. An innermost row of pins 106' is fixedly mounted in the smallest diameter row of holes 102-102'. By the use of a sprocket 20, a conventional rear wheel sprocket construction, such as shown in Fig ure 17, may be replaced by one which uses the present drive. The pins 104' and 105' in rows 100 and 101, respectively, may be shifted by the use of a shifter such as described hereafter relative to Figures 2, 4, 12, 1 8 or any of the other figures which show a shifter.The diameter of the extended row of pins in sprocket 20 will determine the drive ratio which is available between it and the various rows of pins in sprocket 1 2. A representative diameter defined by the pins in outer row 100 is 9 cm; a representative outer diameter for row 101 is 7.5 cm; and a representative diameter for row 102 is 6 cm.

A circular plate 107', Fig.19, is suitably attached to the outside of disc 104" to limit movement of the pins 104' and 105' to the left in Fig.19. A circular plate 108' is suitably secured to disc 103' to limit the amount of movement of the pins 104' and 105' to the right in Fig.19. pins 104' and 105' are fabricated of the same material as the pins carried by sprocket 12, which is described hereafter. Metal pins 97' and 99' are mounted on discs 108' and 107', respectively, for retaining the pins in the positions in which they are last placed by the shifter mechanism. The pins 97" perform this function in the same manner as pins 97' and 99' described hereafter relative to Fig.5.

The pin-carrying sprocket 1 2 includes a main disc 41 (Figs.5 and 6) having a plurality of concentric circular rows of pin-carrying holes therein. In this respect, for example, the innermost row 42 includes 1 2 holes and each succeeding outwardly spaced row includes four more holes. Thus, row 43 has 1 6 holes, row 44 has 20 holes, row 45 has 24 holes, row 46 has 28 holes, row 47 has 32 holes, row 49 has 36 holes, row 50 has 40 holes, row 51 has 44 holes, row 52 has 48 holes, row 53 has 52 holes, row 54 has 56 holes, row 55 has 60 holes, row 56 has 64 holes, row 57 has 68 holes. The innermost row of holes 62' receive screws 62. Outer row 57 has an outer diameter of 26cm and each succeeding outer row is 0.8cm smaller in outer diameter than the preceding row, so that inner row 42 has an outer diameter of 14cm.An outer circular plate 60 (Figs. 4 and 5) is spaced from plate 41 by spacer 61 and plate 60 is attached to plate 41 by screws 62.

plate 60 has the same number of concentric rows of holes as main disc 41, and each of the holes in plate 60 is aligned with a corresponding pin-carrying hole in disc or plate 41.

The rows of holes in plate 60 are designated by primed numerals which correspond to the unprimed numerals of disc 41. Each of the holes in disc 41 contains a cylindrical metallic pin 63 and normally these pins are in a retracted position as shown by numeral 63' in Fig.5. However, one row of pins, denoted by numeral 63", is in an extended position wherein it bridges the space 64 between discs 41 and 60. As will become more apparent hereafter, the pins which lie on smaller dia meters than the extended row of pins which is engaged by the chain will also remain in an extended position, and they will not interfere with the engagement between the chain and the outermost row of pins which are in an extended position. The pins 63 are .728 cm in diameter and the holes are .739 cm in diameter. Chain 40 engages the outer sides of the extended circular row of pins.The drive ratio is determined by the particular row of pins which is in an extended position. It can readily be seen that when a pin occupies an extended position, such as shown as 63" in Fig.5, the outer end 65 of the pin is received in opening 66 of pin-receiving disc 60 and thus an extended pin, such as 63", has one end supported by opening 66 and its other end supported at 67 in opening 69 from which it was extended.

In order to extend a particular row of pins while causing the remainder outside of this row to remain in a retracted position wherein they do not bridge gap 64, a shifter mechanism 70 (Fig.2, 3 and 4) is employed. The shifter mechanism includes a pair of clamping blocks 71 and 72 which are locked onto rear fork 73 by screws 74. A guide block 75 is attached to block 72 by means of a plurality of screws 76. A slidable member 77 is keyed for sliding movement within slot 79 of block 75 with keys 80 and 81 being recveived in keyways 82 and 83, respectively. A second block 84 is attached to block 85 by screws 86, and block 85 is attached to member 77 by screws 87. Thus, slidable members 77 and 84 will move in unison.The exact position of member 77 in groove 79 is determined by Bowden wire unit 89 which has its central portion secured to frame member 1 5 and which terminates at control levber 90 at one end and is attached to slidable member 77 at its other end. It will be appreciated that any other type of cable connection can be used.

Thus, by manipulating lever 90, slidable member 77, and member 84 attached thereto, may be moved back and forth in the direction of the arrows designated by numerais 91 and 95. Each of pins 63 (Fig.5) comprises a magnet having north and south poles as indicated. A magnet 92 is housed in slidable member 77 with its north and south poles as indicated. A magnet 93 is mounted toward the end of slidable member 84 with its north and south poles oriented as indicated.

Thus, whenever slidable members 77 and 84 are moved in the direction of arrow 95 in Fig.4, all pins 63 to the left of the end 96 of slidable member 77 (Fig.5) will be axially pulled to a retracted position within disc 41 while the row of pins at 63" which is aligned with magnet 93 will be axially pulled to the extended position shown in Fig.5. The pins move purely axially without rotation. The rows of pins of lesser diameter than the row in alignment with magnet 93 will remain in their extended positions but they will not interfere with the chain because they lie inwardly thereof. The disc 41 and the disc 60 are fabricated from any suitable material, such as plastics, aluminum or suitable steel, which will not interfere with the above described magnetic action.It can thus be seen that by moving sliding member 77 back and forth in the direction of arrows 91 and 95, and by simultaneously rotating pin-carrying sprocket 12, a predetermined row of pins may be caused to bridge gap or space 64 and the diameter of the particular row of pins which is thus extended will determine the drive ratio produced by rotation of pin sprocket 1 2. A plastics or metal non-magnetic cover 60' (Figs.2, 4 and 5) is suitably attached to disc 60 and a plastics cover 41' is suitably attached to disc 41. Covers 60' and 41' serve to mount metal members 99 and 97, respectively. They also prevent the accumulation of debris in the various openings on the outsides of discs 41 and 60. At the end of each of the holes 69 in disc 41 a metal member 97 to which a magnet will adhere is fastened on plate portion 41.At the end of each of the holes, such as 66 in disc 60, a metal member 99 to which a magnet will adhere is fastened on cover 60'. Alternatively, members formed of plastics impregnated with material to which a magnet will adhere may be used. Instead of being in the same shape as members 97, the plastics members may be in the form of a thin disc (not shown) lying flat and securted in position on the members 41' and 60' at the bottom of bores in which the pins 63 slide.

The function of members 97 and 99 is to hold pins 63 in the positions to which they have been moved so that when the bicycle is laid on its side, the pins will not slide out of the positions to which they have been moved.

A shifter mechanism 1 50, which is shown in Fig.1 2 but which is not shown in Fig.2, it utilised to shift the pins in rows 100 and 101 in rear pin-carrying sprocket 20, as described hereafter relative to Fig.1 3. 8hifter mechanism 1 50 may be the mirror image of shifter mechanism 70 described above if the rear sprocket is the same size as sprocket 12, or it may be of a smaller size if the rear sprocket is of a smaller size, as described above relative to Fig. 1 9. In the embodiment of Figs. 1 to 6 there are 1 5 rows of holes in pin-carrying sprocket 1 2 and 3 rows of holes in pincarrying sprocket 20 so that there are 3 times 15 or 45 possible speeds when the pins are shiftable on both the front sprocket 1 2 and rear sprocket 20.

The endless flexible member of chain 40 (Figs.7 and 8) is fabricated from outer links 103 which are pivotally coupled to inner links 104 by means of rivets 105. Links 103 and 104 are identical except for their positions.

Links 103 define pin-receiving concavities 106 which engage the outer surfaces of the cylindrical pins in essentially complementary mating driving relationship. In order to maintain chain 40 taut, a conventional tensioning member 107 (Fig.2) is provided having spaced wheels 109 around which chain 40 winds, as shown in Fig.2, with member 110 on which wheels 109 are rotatably mounted being tensioned by a spring (not shown) in a clockwise direction about pivot pin 111, as is well known in the art.

In Fig.9, a modified form of shifting mechanism is disclosed. In this embodiment a slidable member 11 2 is provided on block 11 3 which is attached to the bicycle fork. Slidable member 11 2 is analogous to slidable member 77 of Fig.4. A plurality of magnets 114 are carried by slidable member 11 2. Members 114 have their north and south poles oriented in a first direction. The end magnet 11 5 has its poles oriented in the opposite direction.

Magnets 114 will attract pins 11 6 which are magnets. Magnet 11 5 will repel magnetic pins 116. Thus, as slidable member 112 is moved in the direction of arrow 117, all of the magnetic pins 11 6 which are aligned with magnets 114, will be pulled axially without rotation into a retracted position into the openings 117' in disc 11 9 of pin-carrying sprocket 1 20. The row of magnets 11 6 which is aligned with magnet 11 5 will be moved to their extended positions wherein they bridge the gap 121 between disc 119 and disc 122, which receives the outer ends of magnetic pins 116 in openings 123'.As can be seen from Fig.9, chain 1 23 passes through the space 1 21. In the embodiment of Fig.9 disc 11 9 and disc 1 22 are fabricated of nonmagnetic material and metal pins 1 24 and 1 25 to which magnets will adhere are provided in discs 11 9 and 122, respectively, to hold the magnets in either an extended or a retracted position, that is, to hold the pins 11 6 in the position in which they were last placed by magnets 114 and 11 5 so as to prevent the magnets from sliding to another position when the bicycle is laid on its side.

In Fig.9A a modification of the embodiment of Fig.9 is shown. In Fig.9A electromagnets are utilized to shift magnetic pins 116' from their retracted position in disc 120' to their extended position wherein they bridge the gap 121' between disc 120' and disc 122'. In this respect, a lever 130' is provided on an indicator dial 131' mounted on the handlebars or other suitable portion 132' of the bicycle. A bowden wire unit 133' extends between handle 130' and slidable conductor member 134' which is slidable on a base member 135' suitably secured to the fork 136' of the bicycle. Conductor member 134' includes two conductive rods 137' and 139' which are separated by insulators 140' and 140". A battery 141' has its opposite ends connected to conductor rods 137' and 139'.

A plurality of electromagnets 142' are also mounted on block 135'. As member 134' slides, it will bridge the contacts at the ends of each coil of each electromagnet 142' so that when the member 134' is in the position shown in the drsawings, the polarity of the three left electromagnets 142' will be such that magnetic pins 116' will be in the retracted position within disc 120'. However, as can be seen from the drawing, the ends of conductors 137' and 139' are crossed at 143' and there is an insulator 140" between the crossed ends. In view of the foregoing, the polarity of the electromagnet 142', which is fourth from the left, will be reversed from those to the left of it in Fig.9A. Therefore magnetic pin 116', which is aligned with the electromagnet which has it polarity reversed, will bridge the gap 121'.It can therefore be seen that as the slidable member 134' is shifted to the right in Fig.9A from the position shown, the pins 116' will be pulled into disc 120' at all points to the left of the crossed conductors at 143', while all of the pins 116' to the right of the crossed conductors 143' will remain in a position wherein they bridge gap 121'. pins 124' and 125' are provided at the ends of the bores in which pins 11 6' ride, in both disc 120' and disc 122'. These pins are analogous to pins 124 and 125 of Fig.9 and are made of a metal to which magnets will adhere so that they will hold magnetic pins 116' in the position in which they were last placed by the actions of electromagnets 142'. This prevents the pins 116' from sliding to another position when the bicycle is laid on its side.Discs 120' and 122' are fabricated of nonmagnetic material so as not to interfere with the magnetic action described above.

In Figs. 10 and 11 a further modification is disclosed wherein the pins 1 26 are moved between extended and retracted positions by shifter mechanism 1 27 which includes a slider member 1 29 coupled for movement in unison with slider member 1 30. Slider member 1 29 slides in block 1 31 and slider member 1 30 slides in block 132, both of which are suitably attached to the fork of the bicycle.

Slider member 1 29 includes a cam member 1 33 having a cam surface 1 34 thereon. pins 1 26 at the left end of pin-carrying sprocket 1 34 are shown in the fully retracted position wherein springs 1 36 are expanded and they extend between the rear edge 139' of disc 135 and the ends 139 of pins 126. In order to move a pin 1 26 from the retracted position shown at the left of disc 1 35 to an extended position designated by numeral 126', the cam surface 1 34 engages the outer end of pin 126 and forces it downwardly in Fig.10 until it reaches a position, such as shown at 126'.

In this position the end 140 of pin 126 will extend through opening 141 in disc 142. A first O-ring 143 is mounted in annular groove 144 in pin 126 and a metal snap ring 127 is also mounted in annular groove 144, with the outer portion of metal snap ring 127 extending beyond the outer circumference of pin 126. Therefore, when pin 1 26 reches the position shown for pin 126', metal snap ring 127 will retain it in an extended position.In order to cause pin 1 26' to return to its retracted position a cam surface 1 45 on slider member 1 30 engages the end portion 146 of pin 126' in its extended position and forces metal snap ring 127 into opening 141, whereupon spring 1 36 will expand from the contracted position to its expanded position to draw the pin back to the position designated by numeral 126.

In Figures 1 2 and 1 3 a further modified drive is disclosed wherein the rear pin-carrying sprocket 1 49 is identical to front pin-carrying sprocket 1 2 and wherein the rear shifter mechanism 1 50 is essentially the mirror image of the front shifter mechanism 70. Therefore, it is believed that a detailed description of rear pin-carrying wheel 149 and rear shifter mechanism 1 50 is not necessary. Rear shifter mechanism 1 50 is actuated by a Bowden wire unit 1 58 which has a control lever (not shown) analogous to control lever 90 mounted on the handlebars.Ordinarily when the rear shaft 21 (Fig.17) mounts the free wheel 23 in the conventional manner, the spacing between the outside of the bicycle and the rear fork 151 of the bicvycle is such that only a relatively small pin-carrying wheel, such as 20 (Figs. 1, 2 and 19), can be mounted on the rear wheel. However the free wheel one-way clutch device 22, such as shown in Figs. 1 7 and 1 9, is mounted in a specially designed hub or axle 153 (Figs.12 and 1 3) so as to provide the added space needed to permit mounting of a relatively large pin-carrying sprocket 149, which is the same size as pin-carrying sprocket 1 2. Thus, since each pin-carrying sprocket has 1 5 rows of holes, there is a possibility of 225 different drive combinations.However, since certain of these combinations provide the same ratio as other combinations, the effective number of actual combinations is approximately 1 61. to provide 161 different ratios.

The rear hub 1 53 of Fig. 1 3 includes a housing 1 52 which receives the threaded portion 1 54 of free wheel unit 22 in threaded relationship, with the unthreaded portion 1 55 of the free wheel 22 being received in hub portion 1 56. The housing portion 152 is journalled on shaft 1 57 by bearings 1 59 and 160. Portions 161 and 162 are spacers between the rear forks 1 51 of the bicycle which are secured in position by nuts 163.The rear pin-carrying sprocket 149 is mounted on hub portion 1 64 and secured thereto by screws 1 65. Hub portion 164 is threaded into the free wheel 22 at 1 68 for rotation therewith.

In Fig.14 a modified type of pin arrangement is shown, and this pin arrangement is actually an enlargement of the arrangement shown in Fig. 1 3. In this arrangement a shifter mechanism sliding member 77 may be identical to that described above relative to Figs. 4 and 5. The pin-carrying disc 41 includes the plurality of concentric rows of holes. A magnet 92 is carried by member 77. A slidable member 84 carries a magnet 93. Up to this point the shifter mechanism 70 is identical to that described above relative to Figs. 4 and 5.

However, in the embodiment in Fig.14, the pins 1 66 are made out of magnetic material, such as steel, but they are not magnetized, and each of them carries a split O-ring 1 67 which is received in a groove 1 69. It can be seen that there is a gap 1 70 between the ends 171 of the O-ring. When the shifter mechanism 70 is in the position shown in Fig. 14, pins 166 will be attracted by magnet 92 and pin 166' will be attracted by magnet 93 so that pin 166' will bridge the gap 64 between pin-carrying disc 41 and pin-receiving disc 60.The O-rings 1 67 will cause the pins 1 66 to remain in the position in which they were last placed by the magnets so that when the bicycle is laid on its side, the pins 1 66 will not slide away from the position in which they were last positioned. It can also be appreciated that pins 1 66 and 166' may be magnetized, and this will permit the use of smaller magnets in the shifting mechanism and will also produce a faster action as they slide between the retracted positions designated by numeral 1 66 and the extended position designated by numeral 166'. plates 41a and 60a of non-magnetic material are suitably secured to the outsides of discs 41 and 60, respectively, to prevent the pins 1 66 from moving beyond the plates.

In Fig.20 a modified form of pin disc 1 72 is shown in which the crankarm 1 73 is essentially an integrally molded part of the pinreceiving disc 1 74 which is analogous to pinreceiving disc 60 of Fig.14. By integrating the crankarm into a molded pin-receiving disc, the cost is reduced.

In Figs.21 to 28 there is a schematic representation showing how the described multiratio drive 10 operates. For example, in Fig.21 the chain 40 encircles row 42 defined by the extended pins in this row. When it is desired to shift to another row of pins, for example, to row 50, the shifter mechanism 70 is moved in the direction of arrow 1 75.

This will cause the pins in row 50 to bridge the gap 64 and thus assume their extended positions. Each of the pins in row 50 will become sequentially extended as the pin-carrying disc 1 2 rotates in the direction of arrow 1 76. A point will be reached where the first pin 50, will have engaged chain 40 and lifted it away from the pins in row 42. Continued rotation of pin-carrying sprocket 12 in the direction of arrow 1 76 will next result in chain 40 reaching the position shown in Fig.23 at which point contact is practically lost with the pins of row 42. Finally, a sufficient number of pins will be extended from row 50 so that chain 40 now is being driven solely by all of the pins in row 50.Continued rotation in the direction of arrow 1 76 will cause the remainder of the pins in row 50 to become extended and this condition will continue until there is a subsequent shifting. It is ta be noted, however, that all of the pins in row 42 will remain extended and this will not affect operation of the drive because the circle of pins in row 42 is within the circle of pins within row 50.

Furthermore, certain select pins in the rows between rows 42 and 50 may be moved into their extended position due to the wiping of shifter mechanism 70 across such rows as it moved radially outwardly. However, here again, the extended pins are within the radius of row 50 and thus will not interfere with the operation of driving chain 40 by row 50.

In order to move the chain from a row of pins of larger diameter onto a row of pins of lesser diameter, the shifter mechanism 70 is moved inwardly in the direction to arrow 1 77 of Fig.25. This will cause the magnet 92 (Fig.4) to attract all of the pins with which it is in alignment and thus as such pins in rows 50 and the rows between row 50 and row 42 pass the magnet, they will be pulled into a retracted position designated by pins 1 66 in Fig.14. Continued movement of pin-carrying sprocket 1 2 in the direction of arrow 1 76 will cause the chain 40 to drop down onto the pins of row 42 as shown in Fig.26.Continued rotation of sprocket 1 2 in the direction of arrow 1 76 will cause chain 40 to assume the position shown in Fig.27 and ultimately chain 40 will assume the position shown in Fig.28 wherein it is being driven by the pins in row 42.

It is to be especially noted that the transition from one row to another is extremely smooth. There is no abrupt shock in moving from one row to another, whether there is movement from the smallest row to the largest row or movement between any of the intermediate rows. In this respect, it can be seen from a comparison of Figs. 21 and 22 that the first pin of row 50 which engages the chain will be the same distance X from diameter 1 78 as is the pin in row 50 on diameter 1 79. Continued movement of the sprocket in the direction of arrow 1 76 will cause the chain 40 to be lifted gradually as the pin 50 raises the chain. In other words, there is no abrupt shock due to the change in ratio. There is a gradual transition from one ratio to another. This same characteristic is realized when moving the chain from a larger diameter row of pins to a smaller diameter row of pins, and this can be seen in Fig.26.

In this respect, as the pins in row 50 are retracted as they pass shifter mechanism 70, the diameter of the pin row will decrease and the upper run of chain 40 will gradually lower itself until it engages the extended pins in row 42. Thereafter, there will be a smooth transition onto row 42 as shown in Figs. 27 and 28. Thus, here again, there is no abrupt jarring experienced during the shifting operation.

While all of the pins and their associated openings or bores described above are of circular cross-section, it will be appreciated that the pins and the bore in which they slide can be made of any other suitable crosssection, such as square, diamond-shaped, or any other suitable shape.

In the above description reference was made to pin made of magnetic material. This may include pins having a plastics matrix with magnetic material therein. In the appropriate instances, such pins can be magnetized to act as magnets and in other instances they need only be capable of being attracted by magnets, but need not be magnetized.

Claims (11)

1. A multi-ratio drive comprising first and second sprockets, an endless flexible member co-operable with said sprockets to transmit motion therebetween, a plurality of openings in the first sprocket arranged in concentric rows, a pin associated with each opening, and means for shifting each pin between a retracted and an extended position, wherein said shifting means moves the pins solely in an axial direction and in that the pins and sprocket rotate together as a unit in use.

2. A multi-ratio drive as claimed in claim 1, wherein both sprockets have concentric rows of openings and pins associated therewith, and respective shifting means.

3. A multi-ratio drive or sprocket according to claim 1 or 2, wherein said endless flexible member comprises a chain having concave links co-operable with the pins.

4. A variable diameter sprocket comprising disc means, a plurality of concentric circular rows of holes in said disc means, axially movable pins in said holes, and means for selectively shifting the pins to cause said pins of certain of said rows to move between retracted positions in said disc means to extended positions wherein they project outwardly from said disc means a greater amount than when in said retracted positions, and means for mounting said axially movable pins for rotation with said disc means without rotation about their axes as said disc means rotates, wherein said moving means moves said pins substantially solely in their axial directions.

5. A variable diameter sprocket as claimed in claim 4, wherein said axially movable pins are entirely supported solely by said peripheral disc surfaces.

6. A multi-ratio drive or sprocket according to any one of the preceding claims, wherein the pins and shifting means magnetically interact.

7. A multi-ratio drive or sprocket according to claim 6, wherein the pins comprise magnetic material or are magnets, and said shifting means comprises magnet means.

8. A multi-ratio drive or sprocket as claimed in claim 6 or 7, wherein the shifting means is selectably movable to retract by magnetic force the pins in rows radially outside the row required to engage the flexible member.

9. A multi-ratio drive or sprocket as claimed in any one of the preceding claims, wherein the or said first sprocket includes a first disc in which said openings are located, a second disc coaxial with and axially spaced from said first disc to define a space therebetween for receiving said endless member, said first disc supporting first ends of said pins in their extended positions, and second openings in said second disc in alignment with corresponding openings in said first disc for supporting second ends of said pins in their extended positions.

1 0. A multi-ratio drive or sprocket as claimed in claim 9, wherein at least said openings in the outer concentric rows of said first disc are of sufficient depth to receive said pins substantially in their entireties when said pins are retracted.

11. A multi-ratio drive or sprocket as claimed in any one of the preceding claims, wherein it further comprises means for retaining said pins in either said extended or retracted positions in which they are placed.

1 2. A multi-ratio drive comprising two sprockets each engagable with an endless chain, a plurality of openings in at least one of said sprockets defining a series of concentric rings of openings, pins movably mounted in said openings, and means for shifting the pins in at least one of the rings so that they project from the sprocket and engage the chain, wherein the shifting means and the pins magnetically interact to move the pins axially only between extended and retracted positions.

1 3. A multi-ratio drive comprising first and second spaced sprockets, an endless flexible member effectively engaging said first and second sprockets to transmit motion therebetween, a plurality of concentric rows of openings in said first sprocket, pins in said openings, first pin-actuating means for selectively extending pins from a retracted position in said concentric rows of openings, and second pin-actuating means for retracting said pins into said openings by magnetic action to thereby vary the effective diameter of said first sprocket and thus vary the drive ratio between said first and second sprockets.

1 4. A variable diameter sprocket construction comprising disc means, a plurality of concentric circular rows of holes in said disc means, axially movable pins in said holes, and means for selectively moving pins of certain of said rows in a direction axially of said pins to cause said pins of certain of said rows to move between retracted positions in said disc means to extended positions wherein they project outwardly from said disc means a greater amount than when in said retracted positions, said axially movable pins being substantially cylindrical throughout their lengths.

1 5. A multi-ratio drive substantially as herein described with reference to Figures 1 to 8, Figure 9, Figure 9A, Figures 10 and 11, Figures 1 2 and 13, Figures 14 and 15, Figures 18 and 19, or Figure 20.