Background Art A bicycle equipped with a general transmission is comprised of a pedal and a crank for receiving power from a user, a driving chain gear unit for transmitting power generated by the pedal and the crank, a chain for receiving power from the drive chain gear unit and transmitting power, and a driven chain gear unit for receiving power from the chain and transmitting power to a driving wheel. In this case, the driving chain gear unit and the driven chain gear unit can be comprised of staged chain gears having different diameters and different numbers of teeth. Speed change can be performed by causing the change to be engaged with the chain gear of a desired stage.

However, the conventional transmission has the following problems.

First, while speed change is being performed, the unstable engagement of a chain

and a chain gear unit causes consistent power transmission to be difficult and parts to be easily damaged.

Second, while a bicycle is being driven, suitable speed change should be performed according to road conditions. When suitable speed change is not performed, it is temporarily impossible to drive the bicycle due to the loss or increase of power, thereby requiring a user, the power source of the bicycle, to exert excessive force.

Third, when a user starts to ride a bicycle with a chain engaged with a high speed gear, great effort is required to start the bicycle because speed change to a lower speed is only possible after a certain amount of the rotation of wheels is performed by a considerable amount of power.

Fourth, in order to change speed, one of staged chain gears should be selected. In this case, there occurs a problem that the minute speed change of a bicycle is almost impossible.

Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a transmission for bicycle using a transmission pulley, in which fixed and variable truncated cone wheels having a plurality of radial slits are fitted on the driving shaft of a bicycle and a belt is positioned in a wedge-sectional space formed by the interlocking of the fixed and variable truncated cone wheels, and the driving speed of bicycle is automatically changed by widening and narrowing the wedge-sectional space according to the amount of load.

In order to accomplish the above object, the present invention provides a transmission for bicycles using a transmission pulley, the transmission pulley comprising : a

fixed truncated cone wheel including a plurality of radial ribs, the fixed truncated cone wheel being fitted around a driving shaft of a bicycle; a variable truncated cone wheel including a plurality of radial ribs, the variable truncated cone wheel being fitted around the driving shaft of the bicycle to be spaced apart from the fixed truncated cone wheel and being interlocked with the fixed truncated cone wheel to form a wedge-sectional space between the fixed and variable truncated cone wheels; an elastic spring situated between the fixed and variable truncated cone wheels; an elasticity adjusting unit attached to the fixed truncated cone wheel by an adjusting bolt, the elasticity adjusting unit supporting one end of the elastic spring and adjusting elastic force of the elastic spring by the movement of the adjusting bolt; a transmission lever assembly for controlling range of speed change of a bicycle by moving and fixing the variable truncated cone wheel and restricting movement of the variable truncated cone wheel within a predetermined range; and a plurality of idlers for providing a predetermined amount of tension so as to maintain tension of a belt positioned and rotated in the wedge-sectional space.

The elasticity adjusting unit may comprise an adjusting bar fitted at its central portion around the driving shaft of the bicycle, the adjusting bar being moved along the driving shaft by screw action of the adjusting bolt inserted into a through hole of the adjusting bar to compress and release the elastic spring; a securing piece rotatably attached to a lower end of the adjusting bar and fixed to an interior surface of the fixed truncated cone wheel; an adjusting nut situated in the vicinity of the through hole formed in the adjusting bar for helping engagement of the adjusting bolt and the adjusting bar; a locking nut engaged with the adjusting bolt for securing the adjusting bolt at a predetermined position ; and a split pin fitted into the adjusting bolt for preventing the adjusting bar from being removed from the adjusting bolt.

The transmission lever assembly may comprise a body; a transmission lever

mounted on the body to be rotated in clockwise and counterclockwise directions; a position selecting plate for fixing the transmission lever at a certain position; a pushing lever rotatably attached to a projection upwardly projected from a bicycle body positioned around the driving shaft of the bicycle for forwardly and rearwardly moving the variable truncated cone wheel; a wire connected at its one end to a lower end of the transmission lever and at its other end to a certain position of the pushing lever for transmitting movement of the transmission lever to the pushing lever; a protective sleeve constructed to cover an outer surface of the wire for protecting the wire; and a compression spring situated to surround an outer surface of the wire for providing restoring force to the pushing lever.

The fixed and variable truncated cone wheels may be each provided with a support ring so as to prevent the ribs of the fixed and variable truncated cone wheels from being deformed and to keep the interlocking of the fixed and variable truncated cone wheels stable.

Accordingly, a wedge-sectional space formed by the interlocking of the fixed and variable truncated cone wheels is elastically widened and narrowed by load generated by the rotational force of a belt, thereby changing the speed of a bicycle and controlling the range of speed change.

Brief Description of the Drawings The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a plan view showing a truncated cone wheel constituting a transmission pulley in accordance with the present invention; Fig. 2 is a view explaining the interlocking of fixed and variable truncated cone

wheels of the present invention; Fig. 3 is an exploded view showing the assembly of the transmission pulley; Fig. 4 is a view showing a state of the transmission pulley when a large amount of power is exerted on the transmission pulley; Fig. 5 is a view showing a state of the transmission pulley when a small amount of power is exerted on the transmission pulley ; Fig. 6 is an exploded perspective view showing an elasticity adjusting unit; Fig. 7 is a sectional view showing a state in which the elasticity adjusting unit is mounted on the fixed truncated cone wheel; Fig. 8 is a view showing the operation of idlers when a large amount of load acts on the transmission pulley; Fig. 9 is a view showing the operation of idlers when a small amount of load acts on the transmission pulley; Fig. 10 is a view showing the mounting of a transmission lever assembly ; Fig. 11 is a view showing a position selecting plate; Fig. 12 is a view showing a pushing lever ; and Fig. 13 is a graph showing a torque change, a diameter change and a diameter change ratio.

Best Mode for Carrying Out the Invention Hereinafter, a preferred embodiment of the present invention is described in detail with reference to accompanying drawings.

A transmission for bicycles using a transmission pulley according to the present invention serves to automatically change speed in such a way that a belt is positioned in a

wedge-sectional space formed by the interlocking of fixed and variable truncated cone wheels and the wedge-sectional space is selectively widened and narrowed according to the application of external load. The transmission of the present invention is comprised of a transmission pulley 100, an elastic spring 150, an elasticity adjusting unit 200, a plurality of idlers 210, a transmission lever assembly 220, and two support rings 230.

As shown in Figs. 1 to 5, the transmission pulley 100 is comprised of a fixed truncated cone wheel 110 and a variable truncated cone wheel 120. The two truncated cone wheels 110 and 120 are generally shaped in the form of dishes. A plurality of slits 111 and 121 are formed on the fixed and variable truncated cone wheels 110 and 120 to be radially extended from the peripheries of the fixed and variable truncated cone wheels 110 and 120, respectively. A plurality of ribs 112 and 122 are radially formed on the portions of the fixed and variable truncated cone wheels 110 and 120 except for the central portions of the truncated cone wheels 110 and 120. Two through holes are formed on the centers of the truncated cone wheels 110 and 120 to allow the driving shaft of the bicycle to be extended therethrough. The truncated cone wheels 110 and 120 are mounted on the frame of the bicycle by fitting the driving shaft into the through holes. The ribs 112 and 122 become widened by a certain ratio in a direction from the centers of the truncated cone wheels 110 and 120 to their peripheries. Additionally, a through hole, into which an adjusting bolt 201 described below is fitted, is formed in the vicinity of the center portion of the fixed truncated cone wheel 110.

The fixed truncated cone wheel 110 is mounted on the driving shaft of the bicycle at a certain position by inserting the driving shaft into the through hole formed on the fixed truncated cone wheel 110. The fixed truncated cone wheel 110 is secured to a certain position of the driving shaft of the bicycle by fitting a securing pin 114 through a boss 113.

The variable truncated cone wheel 120 is mounted on the driving shaft of the bicycle

in the same manner as the fixed truncated cone wheel 110 so as to be moved forward and rearward. That is, the variable truncated cone wheel 120 is moved forward and rearward along the driving shaft of the bicycle. A boss 123 is formed around the through hole of the variable truncated cone wheel 120 to allow the variable truncated cone wheel 120 to be stably moved on the driving shaft of the bicycle. A thrust bearing 124 is formed around the boss 123. The variable truncated cone wheel 120 is moved by pushing the thrust bearing 124 with a transmission lever assembly described below, so an interval between the two truncated cone wheels 110 and 120 is determined, thereby determining the range of the speed change of a bicycle.

The two truncated cone wheels 110 and 120 are interlocked with each other while being fitted around the driving shaft, thereby forming a wedge-sectional space 240. The ribs 112 and 122 are inserted into the slits 111 and 121 in such a way that the ribs 112 of the fixed truncated cone wheel 110 are inserted into the slits 121 of the variable truncated cone wheel 120 and the ribs 122 of the variable truncated cone wheel 120 are inserted into the slits 111 of the fixed truncated cone wheel 110, resulting in the forming of the wedge-sectional space 240.

In this case, when the variable truncated cone wheel 120 approaches the fixed truncated cone wheel 110, the wedge-sectional space 240 is widened. On the other hand, when the variable truncated cone wheel 120 recedes from the fixed truncated cone wheel 110, the wedge- sectional space 240 is narrowed.

A belt 250 is positioned in the wedge-sectional space 240 to be wound around the driven shaft of the bicycle and transmit power from the transmission pulley 100 to the driven shaft. The ribs 112 and 122 of the truncated cone wheels 110 and 120 may be damaged by the pushing of the belt 250 that will be accommodated in the wedge-sectional space 240 formed by the interlocking of the two truncated cone wheels 110 and 120. In order to prevent the ribs 112 and 122 from being damaged, two support rings 230 are positioned to

support the ribs 112 and 122 of the truncated cone wheels 110 and 120 and prevent them from being deformed. A projection is formed on a driven pulley mounted on a driven shaft so as to prevent the belt 250 from slipping on the driven pulley.

An elastic spring 150 is mounted around the driving shaft between the fixed truncated cone wheel 110 and the variable truncated cone wheel 120 so as to elastically maintain an interval between the truncated cone wheels 110 and 120 and to adjust the interval according to load exerted by the belt 250. In this case, one end of the elastic spring 150 is brought into contact with the variable truncated cone wheel 120 and the other end of the elastic spring 150 is brought into contact with the adjusting bar 202 of the elasticity adjusting unit 200.

Referring to Figs. 6 and 7, the elasticity adjusting unit 200 is brought into contact with one end of the elastic spring 150, so the degree of the compression of the elastic spring 150 can be controlled by the forward/rearward movement of an adjusting bolt 201. The elasticity adjusting unit 200 is basically comprised of the adjusting bar 202, a securing piece 203, an adjusting nut 204, a locking nut 205, and a split pin 206.

The adjusting bar 202 has a ring-shaped central portion, and is mounted around the driving shaft of the bicycle by fitting the ring-shaped central portion around the driving shaft.

One end of the elastic spring 150 is brought into contact with the central portion of the adjusting bar 202. A bolt hole 202a is formed on the upper portion of the adjusting bar 202, and the adjusting bolt 201 is inserted into the bolt hole 202a.

A plurality of projections 202b are formed in the vicinity of the bolt hole 202a.

The adjusting nut 204 is engaged with the projections 202b. The adjusting nut 204 is provided at its center with a through hole to communicate with the bolt hole 202a formed on the adjusting bar 202, and a plurality of projections to be engaged with the projections 202b formed on the adjusting bar 202, to prevent the slippage of the adjusting bar 202 engaged with

the adjusting bolt 201 and to help the forward and rearward movement of the adjusting bar 202 by the rotation of the adjusting bolt 201.

The securing piece 203 is rotatably attached by means of a hinge 203a to be rotated with regard to the adjusting bar 202.

The adjusting bar 202 is attached to the fixed truncated cone wheel 110 by securing the securing piece 203 to the fixed truncated cone wheel 110 by a rivet 203b.

The locking nut 205 is engaged with the adjusting bolt 201 while being brought into contact with an engaging nut 207 engaged with the adjusting bolt 201 inserted into the through hole 115 formed on the fixed truncated cone wheel 110. While the adjusting bar 202 adjusts the degree of the compression of the elastic spring 150 by the rotation of the adjusting bolt 201, the locking nut 205 prevents the adjusting bolt 201 from receding toward the fixed truncated cone wheel 110 and secures the adjusting bolt 201 at a certain position in the through hole 115 of the fixed truncated cone wheel 110.

The split pin 206 is fitted into the adjusting bolt 201 while being inserted into a split pin hole 201a formed on an end portion of the adjusting bolt 201. The split pin 206 serves to prevent the adjusting bolt 201 and the adjusting bar 202 from being separated from each other by restricting the further retreat of the adjusting bolt 201.

In such a case, one end of the elastic spring 150 is brought into tight contact with one surface of the adjusting bar 202, so the range of the compression of the elastic spring 150 is determined by the rotation of the adjusting bolt 201. That is, when the adjusting bolt 201 is rotated in a counterclockwise direction, the adjusting bolt 202 recedes from the fixed truncated wheel 110 by the screw action of the adjusting bolt 201, thereby reducing the range of the compression of the elastic spring 150. On the other hand, when the adjusting bolt 201 is rotated in a clockwise direction, the adjusting bar 202 approaches the fixed truncated cone wheel 110, thereby expanding the range of the compression of the elastic spring 150.

Referring to Figs. 8 and 9, the idlers 210 are situated to adjust the tension of the belt 250 that passes over the driving and driven shafts of the bicycle. That is, when the tension of the belt 250, which is accommodated in the wedge-sectional space 240 of the transmission pulley 100, is varied by the transmission pulley 100, the idlers 210 keep the tension of the belt 250 constant. In this case, the idlers 210 are well known, so a detailed explanation of them is omitted.

As shown in Figs. 10 to 12, the transmission lever assembly 220 controls the transmission of the bicycle by determining the maximum spaced range, or controlling the maximum spaced interval between the variable truncated cone wheel 120 and the fixed truncated cone wheel 110 along the driving shaft of the bicycle.

In this case, the transmission lever assembly 220 is comprised of a body 221, a transmission lever 222, a position selecting plate 223, a pushing lever 224, a wire 225, a protection sleeve 226 and a compression spring 227.

The body 221 is a space in which the transmission lever 222 and the position selecting plate 223 are situated.

The transmission lever 222 is constructed to be rod-shaped, and is situated to be rotatable around a rotating shaft 221 a formed on the transmission lever assembly body 221.

One end of the wire 225 is attached to the lower end of the transmission lever 221.

The position selecting plate 223, through which the upper portion of the transmission lever 222 is extended, is mounted on the transmission lever assembly body 221.

The position selecting plate 223 controls the position of the pushing lever 224 by securing the transmission 222 at a certain position, thereby restricting the movement of the variable truncated cone wheel 120 within a certain range.

The pushing lever 224 is rotatably attached to a projection 260 upwardly projected from a bicycle body positioned around the driving shaft of the bicycle.

Two branch-shaped pushing portions 224a are formed on the lower end of the pushing lever 224. The maximum interval between the variable and fixed truncated cone wheels 120 and 110 is determined by pushing the variable truncated cone wheel 120 with the pushing portions 224a that are brought into contact with the thrust bearing 124 formed around the boss 123 of the variable truncated cone wheel 120.

The wire 225 is connected at its one end to the lower end of the transmission lever 222 and at its other end to a certain position of the pushing lever 224, and transmits the movement of the transmission lever 222 to the pushing lever 224.

The protective sleeve 226 is constructed to cover the outer surface of the wire 225, and is supported on the bicycle while being connected to the bicycle body. One end of the protective sleeve 226 is fixedly attached to the transmission lever assembly body 221, thus securing the transmission lever assembly body 221 to the bicycle body. A compression spring support 226a is formed on the other end of the protective sleeve 226.

The compression spring 227 is situated to surround the wire 225. One end of the compression spring 227 is brought into contact at its one end with the compression spring support 226a and at its other end with the pushing lever 224, thus restoring the pushing lever 224 to its original position. When the transmission lever 222 is moved from the front potion of the position selecting plate 223 to the rear portion of the position selecting plate 223, the pushing lever 224 is returned to its original position by the restoring force of the compression spring 227.

The operation of the transmission of the present invention having such a construction is described, hereinafter.

The wedge-sectional space 240 is formed by the interlocking of the fixed and variable truncated cone wheels 110 and 120 fitted around the driving shaft of the bicycle. A user situates the belt 250, which passes over the driven shaft of the bicycle, in the wedge-

sectional space 240. The interval between the fixed truncated cone wheels 110 and the adjusting bar 202 is determined by the movement of the adjusting bar 202, which is in contact with the interior surface of the fixed truncated cone wheel 110 while being engaged with the adjusting bolt 201, utilizing the adjusting bolt 201 fitted into the fixed truncated cone wheel 110. When a user is strong, the elastic spring 150 in contact with the adjusting bar 202 is allowed to be compressed by rotating the adjusting bolt 201 in a counterclockwise direction to cause the adjusting bar 202 to recede from the fixed truncated cone wheel 110, thereby restricting the movement of the elastic spring within a relatively small range. When the movement of the elastic spring 150 is restricted within a relatively small range, power required to start the transmission pulley 100 is increased and time required to obtain a certain speed is shortened. Accordingly, when a user is strong, it is desirable to use the compressed elastic spring 150.

When a user is weak, the elastic spring 150 in contact with the adjusting bar 202 is allowed to be released by rotating the adjusting bolt 201 in a clockwise direction to cause the adjusting bar 202 to approach the fixed truncated cone wheel 110, thereby extending the movement of the elastic spring to a relatively large range. That is, when the range of the movement of the elastic spring 150 is extended, the tension of the elastic spring 150 is reduced, so power required to start the transmission pulley 100 is reduced and time required to obtain a certain speed is lengthened. Accordingly, when a user is weak, it is desirable to use a released elastic spring 150.

The compressing force of the elastic spring 150 is controlled and the wedge- sectional space 240 is determined, by the setting of the interval between the two truncated cone wheels 110 and 120.

When a certain amount of load is exerted, such as for starting a bicycle, the variable truncated cone wheel 120 approaches the fixed truncated cone wheel 110 and the wedge-

sectional space 240 is widened. Accordingly, the diameter of a circle formed by the intersection points of the fixed and variable truncated cone wheels 110 and 120 is reduced, so a relatively great power is transmitted. When the load is eliminated, the interval between the fixed and variable truncated wheels 110 and 120 is increased and the wedge-sectional space 240 is narrowed. Accordingly, the diameter of the circle formed by the intersection points of the fixed and variable truncated cone wheels 110 and 120 is increased, so speed change is produced to increase the speed of a bicycle.

In this case, while the crank of a bicycle receives power from a user and transforms the power into rotational movement, a change in torque occurs. Referring to Fig. 13, the torque change of the driving transmission pulley 100 causes the tension change of the tensioned portion of a belt, and the phase of the diameter of a circle formed by the intersection points of the two truncated cone wheels 110 and 120 is opposite to the phase of the torque change.

However, a diameter change ratio should be kept constant regardless of the torque changes. The diameter of a circle formed by the intersection points of the two truncated cone wheels 110 and 120 is changed according to the torque change by frictional resistance generated by contact among the slits 111 and 121 and the ribs 112 and 122 formed on the two truncated cone wheels 110 and 120, but the diameter change does not occur abruptly.

A user determines the range of speed change of a bicycle by the transmission lever 222 of the transmission lever assembly 220. When the transmission lever 222 is situated in a certain position of the position selecting plate 223, the movement of the transmission lever 222 is transmitted to the pushing lever 224 through the wire 225 connected to the transmission lever 222. Subsequently, the pushing lever 224 pushes and moves the variable truncated cone wheel 120, so the maximum interval between the variable and fixed truncated cone wheels 120 and 110 is determined.

In this case, the transmission lever 222 is generally situated at"D"position. When the transmission lever 222 is pushed to"1"position if necessary, the transmission lever 222 is rotated around the rotating shaft 221a, the upper portion of the pushing lever 224 is rotated toward the transmission lever assembly body 221 by the wire 225 connected to the transmission lever 222, and, finally, the pushing portion 224a of the pushing lever 224 causes the variable truncated cone wheel 120 to approach the fixed truncated cone wheel 110 by pushing the variable truncated cone wheel 120. As the variable truncated cone wheel 120 approaches the fixed truncated cone wheel 110, there is widened the wedge-sectional space 240 formed by the interlocking of the variable and fixed truncated cone wheel 120 and 110.

That is, the diameter of a circle formed by the intersection points of the two truncated cone wheels 110 and 120 is reduced, so a stopped bicycle is easily started. This has the same effect as starting to ride a bicycle in a first stage gear. The speed change of a bicycle is controlled by fixing the transmission lever 222 at"2","3"or"D"position as occasion demands.

Industrial Applicability As described above, the present invention provides a transmission for bicycles using a transmission pulley, in which a wedge-sectional space formed by the interlocking of fixed and variable truncated cone wheels fitted around the driving shaft of a bicycle is widened and narrowed according to the amount of load, so that speed change is automatically carried out according to the amount of load and the transmission can be applied to all kinds of bicycles requiring speed change.

Additionally, the range of the speed change of a bicycle can be freely controlled as desired by a user, so the speed change of the bicycle can be performed according to driving

and road conditions and the transmission can be applied to mountain bicycles.

Additionally, the transmission pulley of the present invention can be employed as an industrial transmission pulley for an apparatus requiring the transmission of power generated by a motor, which can transmit power from a driving shaft to a driven shaft and control the amount of load transmitted.