WO2004101195A1

WO2004101195A1 - A device for forming tooth form of sprocket gear for power transmission apparatus of cahinless bicycle

Info

Publication number: WO2004101195A1
Application number: PCT/KR2004/001166
Authority: WO
Inventors: Chil-Sung Hwang
Original assignee: Bikevalley Co., Ltd
Priority date: 2003-05-17
Filing date: 2004-05-17
Publication date: 2004-11-25
Also published as: CN1787890A; KR100527093B1; KR20040099052A; CN100396399C

Abstract

The present invention discloses a device for forming a tooth form of a sprocket gear for the power transmission apparatus fore a chainless bicycle. The device for forming a tooth form comprises a first and second main driving motor operated by the operation of an operating switch according to information set in a control unit, a first gear unit rotated by the first main driving motor, a second gear unit rotated by the second main driving motor, a tooth forming unit of crown sprocket gear including a first end mill machining unit mounted in the first gear unit, and a tooth forming of flat sprocket gear including a second end mill mounted in the second gear unit. A working object to be machined to a crown or flat sprocket gear is attached too the tooth forming unit of crown or flat sprocket gear such that the respective tooth is machined by the first or second end mill.

Description

A DEVICE FOR FORMING TOOTH FORM OF SPRQKET GEAR FOR POWER TRANSMISSION APPARATUS OF CAHINLESS BICYCLE

Technical Field The present invention relates to a device for forming a tooth form of a sprocket gear ^• for _ the power transmission apparatus of a chainless bicycle. More specifically, the invention relates to such a device, in which a crown sprocket gear or a flat sprocket gear is so machined that it can be tooth-engaged with a roller-tooth wheel for transmitting a driving power to the rear wheel of a chainless bicycle, in such a manner that the tooth-engagement is carried out by a silent and accurate face-contact.

Background Art

In general, a bicycle is composed of a frame, a pedal rotatably installed on the frame for generating a driving power by means of the feet of a bicycle rider, front and rear wheels freely rotatably mounted in the front and rear portion of the frame, and a power transmission member for transmitting the driving power generated by rotation of the pedal to the rear wheel .

In this construction of the bicycle, the power transmission member of the bicycle includes a drive sprocket mounted in the pedal side, a driven sprocket mounted in the rear wheel side and having a ratchet for transmitting the , driving power in a unidirectional fashion, and a chain for coupling the drive sprocket and the driven sprocket to each other.

In the bicycle having the above-described construction, when the pedal is rotated in one direction, i.e., in an advancing direction, the driving power is transmitted to the rear wheel by means of the chain for coupling the drive and driven sprockets so that the bicycle can be ridden in a forward direction only.

Therefore, since the pedal must be rotated in one direction only, i.e., only in a> riding direction of the bicycle, the muscle of feet is developed non-uniformly, particularly during the long-term riding period.

In addition, since such a simple and identical exercise is repeated, the rider feels bored and tired after a short period of riding on a bicycle, and it is not readily possible for the rider to relax the fatigue of muscles during the bicycle riding.

In the conventional driving mechanism, when the pedal is not rotated or rotated in a reverse direction, the drive sprocket and the chain is also rotated in a reverse direction, but the power transmission is intermitted by the ratchet inside the driven sprocket, which is rotated freely in a reverse direction.

In addition, a transmission device, which is modified from the power transmission unit, has been known. This transmission device has been applied to a wheel chair, a toy car using a pedal, or the like.

The above conventional transmission device incldues a gear having various diameters in the shafts of the front and rear wheels, in which a speed variation is carried out by changing the position of a ch^in for transmitting the driving power between the gears. Besides this conventional transmission, recently, a transmission device installed inside the rear wheel hub of the bicycle or the like has been developed and commercialized, in which small gears are arranged inside the hub and the speed change is performed by the number ratio of the teeth of the gears.

However, disadvantageously, the conventional transmission device of bicycles having the above-described construction has an increased volume and weight due to the complexity of its construction, and accordingly the overall durability thereof may not be guaranteed.

In addition, most of conventional bicycles transmit the driving power to the rear wheel by means of a chain. Therefore, a problem occurs in that the clothes of bicycle riders can be damaged during the bike riding.

In the old bicycles, the chain can be readily and accidentally slipped off, and thus the bicycle rider must replace the chain onto the sprocket gear, so that the rider wastes his or her time and his or her _t hands and clothes may be stained.

FIGS. 1 and 2 show a conventional power transmission device of a bicycle to solve the above problems, in which the power transmission device is denoted by a reference numeral 2. The power transmission device includes a transmission drive unit 4 in a pedal shaft 10 of the bicycle. The transmission drive unit

4 has a main transmission 14 inside a housing 40, and the main transmission 14 includes a sun gear, a ring gear, a multi-step carrier and an epicyclic gear. Using a transmission lever 16, a driving power is transmitted to a crown sprocket gear 56 of a hub via front and rear roller-tooth wheels 52, 60 of a driven shaft 62, which is tooth-engaged with a crown sprocket gear 18.

At this time, using an auxiliary transmission lever 80, a transmission driven shaft unit 6 operates an auxiliary transmission unit 58, so that an auxiliary acceleration can be achieved.

In the power transmission device of a bicycle as describe above, the roller-tooth wheel for transmitting a driving power is tooth-engaged with the crown sprocket gear or a flat sprocket gear (not shown) in a sμch a manner that they are disposed at a certain angle with each other. FIG. 3 shows a tooth curvature 'of a flat sprocket gear engaged with a roller-tooth wheel in the conventional power transmission device of a bicycle. As shown in FIG. 3, the tooth 68 and the tooth groove 70 of the flat sprocket gear 66, which is engaged with the roller tooth 64 of the roller-tooth wheels 52 and 60, are formed such that they have a specific curvature, thereby enabling a precision tooth-engagement.

Although FIG. 3 illustrates the flat sprocket gear 66, the same is applied to the crown sprocket gear 56. FIG. 4 shows an engagement between teeth in the conventional gears. As depicted in FIG. 4, the shape of the tooth 74 and the tooth groove 76 in an ordinary gear 72 are distinguished from the tooth 68 and the tooth groove 70 of the flat or crown sprocket gear 66, 56, which is engaged with the roller-tooth 52, 60. In general, it is difficult that a gear machining apparatus for manufacturing an ordinary gear is used for precisely machining and manufacturing a flat or crown sprocket gear, which is to be engaged with a roller-tooth wheel.

In other words, in ¹ the case wherl,'e ordinary equipment and tools is used for forming a tooth form of the flat or crown sprocket gear, which is utilized for transmitting a driving power, the efficiency of work and the productivity are decreased and a precision machining cannot be readily carried out. Also, it is a problem that the manufactured gears cause noise when they are engaged with each other.

The driving or operating power is transmitted while rolling-contacting between the roller-tooth wheel and the flat or crown sprocket gear. Accordingly, the ordinary equipment and tools cannot overcome a, limitation in a precision machining, an efficient working, and productivity, which must be associated with the machining or manufacturing of the above flat or crown sprocket gear. Disclosure of Invention

Therefore, the present invention has been made in order to solve the above problems occurring in the prior art, and it is an object of the present invention to provide a device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle, in which a crown sprocket gear or a flat sprocket gear is so machined that it can be tooth-engaged with a roller-tooth wheel for transmitting a driving power to the rear wheel of a chainless bicycle, in such a manner that the tooth-engagement is carried out by a silent and accurate face-contact.

In order to accomplish the above object, according to one aspect of the invention, there is provided a device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle. The device for forming a tooth form including: a) first and second main driving motors disposed spaced- apart from each other in a base frame, the first and second main driving motors being electrically connected to each other and being operated by a control unit according to information set therein, the control unit sensing the operation of an operating switch; b) a first gear unit including a left driven gear disposed at one side thereof to be rotated by a first driving shaft gear of the first main driving motor and a right driven gear disposed at the other side thereqf to be rotated .through an idle gear; c) a second gear unit including a drive gear disposed at one side thereof to be rotated by a second driving shaft gear of the second main driving motor and a driven gear being rotated by the drive gear while being engaged with the drive gear; d) a first end mill machining unit including a first end mill motor, an end mill chuck and a first end mill installed in the described order in a support frame of a support member, the support member being mounted in a first slanted shaft, the first slanted shaft being slantly installed at a certain angle relative to a left driven shaft of the left driven gear in the first gear unit such that it can be cooperatively rotated by a bevel gear of the left driven shaft; e) a tooth forming unit of a crown sprocket gear, wherein a working object to be machined to a crown sprocket gear can be attached to one end of a second slanted shaft such that a tooth form is machined by the first end mill, the second slanted shaft being slantly installed at a certain angle relative to the right driven shaft such that it can be cooperatively rotated by a bevel gear of the right 'driven shaft in('the right driven gear; f) a tooth forming unit of flat sprocket gear including a circular plate having a certain size fixed to the upper portion of a driving shaft of a drive gear in the second gear unit, and a second end mill mounted on the vertical line of the outer circumference of the drive gear and being rotatably operated by the driving power of a second end mill motor, wherein a working object to be machined to a flat sprocket gear is attached to the upper portion of the driven shaft of the driven gear, the working object having the same size as the driven gear, whereby the second end mill forms a tooth form¹ when the driven gear is rotated by the drive gear.

Brief Description of Drawings

Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGS. 1 and 2 show a conventional power transmission device of a bicycle to solve the problems in the prior art; FIG. 3 shows a tooth curvature of a flat sprocket gear engaged with a roller-tooth wheel in the conventional power transmission device of a bicycle;

FIG. 4 shows an engagement between teeth in the conventional gears;

FIG. 5 illustrates a device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle according to one embodiment of the invention; and FIG. 6 shows a tooth engagement between a roller-tooth wheel and a flat sprocket gear manufactured according to the present invention.

Best Mode for Carrying Out the Invention Referring to the accompanying drawings, the preferred embodiments according to the present invention are hereafter described in detail.

FIG. 4 illustrates to a device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle according to one embodiment of the invention, in which the device of the invention denoted by a reference numeral 80. FIG. 5 shows an example of tooth engagement between a roller-tooth wheel and a flat sprocket gear machined according to the present invention. The device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle 80 is composed of a first and second main driving motor 82, 84, a first gear unit 86, a second gear unit 88, a tooth forming unit 90 of crown sprocket gear, and a tooth forming unit 92 of flat sprocket gear.

The first and second main driving motors 82, 84 are spaced apart from each other inside a base frame 98, and electrically connected and cooperatively operated according to data set in a control unit 96, which senses an operation of an operating switch 94.

The first and second driving motors 82, 84 may be adjusted to a certain r.p.m by the control unit 96, and operated with the adjusted r.p.m when the operating switch 94 is operated. Also, the first and second driving motors 82,. 84 are configured to be variably controlled according to the amount of working materials and a required precision of design. The first gear unit 86 comprises a left driven gear 102 disposed at one side of the first gear unit 86 to be rotated by a first driving shaft gear 100, and a right driven gear 106 disposed at the other side of the first gear unit 86 to be rotated by an idle gear 104. The left driven gear 102 and the right driven gear 106 are different from each other with respect to their gear ratios. In other words, the gear dimension of the, left driven gear 102 is formed rather smaller at a certain proportion such that it can be rotated faster. Therefore, it is set to a certain ratio such that the machining contact point between a first end mill 108 and a working object 110 to be machined to a crown sprocket gear can be continuously moved and, consequently, reached to the first forming tooth groove.

The second gear unit 88 is composed of a drive gear 114 being rotated by a second driving shaft gear 112 of the second driving motor 84, and a driven gear 116 being engaged with the drive gear 114 and rotated thereby.

The drive gear 114 and the driven gear 116 are different from each other with respect to the number of their teeth. In other words, the number of teeth of the drive gear 114 is formed lower than that of the driven gear 116 such that the drive gear 114 can be rotated faster. With respect to the left driven gear 102 and the right driven gear 106, and the drive gear 114 and the driven gear 116, their tooth ratio may not be necessarily fixed. I.e., they may be prepared to have various numbers pf teeth and selectively assembled, depending on the design specification of a working object to be machined.

The tooth forming unit 90 of crown sprocket gear comprises an end mill machining unit 132, which is composed of a first end mill motor 128, an end mill chuck 130, a first end mill 108 that are installed, in the described order, in a support frame 126 of a support member 124. The support member 124 is mounted on a first slanted shaft 122, which is slantly installed at a certain angle such that it can be cooperatively rotated by a bevel gear 120 of the left driven shaft 118 of the left driven gear 102 in the first gear unit 86. In addition, the working object 110 to be machined to a crown sprocket gear by the end mill 108 is installed at one end of a second slanted shaft 136, which is slantly installed at a certain angle such that it can be cooperatively rotated by a bevel gear 120 of the right driven shaft 134 in the right driven gear 106.

The tooth forming unit 92 of flat sprocket gear comprises a circular plate 140 fixed to the upper portion of the driving shaft 138 of the drive gear 114 in the second gear unit 88. A second end mill 142 is> installed at the vertical line of the outer circumference of the drive gear 114 such that the circular plate 140 can be operated by the driving power of the second end mill 142. The working object 148 to be machined to a flat sprocket gear is installed with a fixing bolt 146 at the upper portion of the driven shaft 114 of the driven gear 116 rotated by the drive gear 114, and the working object 148 has the same size as that of the driven gear 116, such that it can be machined to a desired tooth form by the second end mill 142. FIG. 6 shows a tooth forming of crown sprocket gear by means of an end mill according to the invention. As illustrated in FIG. 6, the first end mill 108 is operated and rotated fast by the first end mill motor 142 and travels along an orbital line 150. Simultaneously, the working object 110 to be machined to a crown sprocket gear is rotated and contacted with the first end mill 108 at the machining points a, b, c, d, and the like. A difference between their rotations is caused due to the difference in the number of gear teeth set in the order of these machining points a, b, c, d and the like. Therefore, while travelling along the orbital line 15.0, the tooth and tooth groove are machined.

The operation of the invention as describe above will be explained below. In the power transmission apparatus of a chainless bicycle, a sprocket gear transmits the driving power while maintaining a certain angle of tooth-engagement with a roller-tooth wheel. In order to form a tooth form of such sprocket gear having various shapes according to the invention, first, the working object 110 to be machined to a crown sprocket gear is mounted in the second slanted shaft 136, or the working object 148 to be machined to a flat sprocket gear is mounted in the driven shaft 144.

Afterwards, the operator operates the operating switch 94 such that the control unit 96 operates the first main driving motor 82. Then, the left driven gear 102 engaged with the fist driving shaft gear 100 rotates faster since the number of teeth thereof is lower than that of the right driven gear 106. The left driven gear 102 rotates the first slanted shaft 122 slanted at a certain angle relative to the left driven shaft 118, via the bevel gear 120 of the left driven shaft 118.

Therefore, due to • the rotation of the first slanted shaft 122, the end mill machining unit 132 on the support frame 16 integrally formed with the support member 124 revolves about the center of the first slanted shaft 122 following a large circle.

Simultaneously, the first end mill motor 128 of the end mill machining unit 123 is operated to rotate the first end mill 108 according to the above established information.

Then, according to the rotation of the left driven gear 102, the rotation of the right driven gear 106 tooth-engaged with the idle gear 104 is transmitted to the .second slanted shaft 136 disposed at a certain angle relative to the right driven shaft 134 via the bevel gear 120. Therefore, the working object 110 to be machined to a crown sprocket gear fixed to one end of the second slanted shaft 136 is rotated faster than the first end mill 108.

As describe above, the first end mill 108 is rotated faster than the working object 110 to be machined to a crown sprocket gear while being contacted thereto, so that a tooth groove can be formed in the working object 110 following a certain curvature, thereby enabling the precision machining of a crown sprocket gear. In addition, the tooth forming unit 92 of flat sprocket gear is installed at one end of the base frame 98 such that a flat sprocket gear can be manufactured, simultaneously with the manufacturing of a crown sprocket gear. By the operation of the operating switch 94, the control unit 96 operates the second main driving motor 84 according to an electrical signal thereof, and the second main driving motor 84 rotates the drive gear 114 via the second driving shaft gear 112. Here, the number of teeth of the drive gear 114 is lower than that of the driven gear 116.

Accordingly, the drive gear 114 is rotated faster than the driven gear 116 to rotate the circular plate 140 mounted in the driving shaft 138, so that the second end mill 142 attached to the circular plate 140 is operated following a circle, while rotating itself.

When the drive gear 114 is rotated, the driven gear 116 is rotated slower than the drive gear 114 and rotates the driven shaft 144. Therefore, the second end mill 142 forms a tooth form in the working object ,148 fixed to t,he upper portion of the driven shaft 144, while moving the contact point therewith.

As describe above, the device for forming a tooth form according to the invention can machine a crown or flat sprocket gear capable of providing a smooth rolling contact with a roller-tooth wheel, particularly a precision sprocket gear can be manufactured in a fast way.

Industrial Applicability

The tooth forming device of the present invention provides a crown or flat sprocket gear, which can transmit a driving or operating power by a silent and accurate contact with a roller- tooth wheel, when used in a power transmission apparatus of a particular industry including a chainless bicycle.

Furthermore, the crown or flat sprocket gear according to the invention can be applied to a driving unit for transmitting a small operating or driving power, thereby improving reliability and quality of product.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

What Is Claimed Is :

1. A device for forming a tooth form of a sprocket gear for the power transmission apparatus of a chainless bicycle comprising: a) first and second main driving motors disposed spaced- apart from each other in a base frame, the first and second main driving motors being electrically connected to each other and being operated by a control unit according to information set therein, the control unit sensing the operation of an operating switch; b) a first gear unit including a .,left driven gear disposed at one side thereof to be rotated by a first driving shaft gear of the first main driving motor and a right driven gear disposed at the other side thereof to be rotated through an idle gear; c) a second gear unit including a drive gear disposed at one side thereof to be rotated by a second driving shaft gear of the second main driving motor and a driven gear being rotated by the drive gear while being engaged with the drive gear; d) a first end mill machining unit including a first end mill motor, an end mill chuck and a first end mill installed in the described order in a support frame;, of a support member, the support member being mounted in a first slanted shaft, the first slanted shaft being slantly installed at a certain angle relative to a left driven shaft of the left driven gear in the first gear unit such that it can be cooperatively rotated by a bevel gear of the left driven shaft; e) a tooth forming unit of crown sprocket gear, wherein a working object to be machined to a crown sprocket gear can be attached to one end of a second slanted shaft such that a tooth form is machined by the first end mill, the second slanted shaft being slantly installed_' at a certain angle relative to the right driven shaft such that it can be cooperatively rotated by a bevel gear of the right driven shaft in the right driven gear; f) a tooth forming unit of flat sprocket gear including a circular plate having a certain size fixed to the upper portion of a driving shaft of a drive gear in the second gear unit, and a second end mill mounted on the vertical line of the outer circumference of the drive gear and being rotatably operated by the driving power of a second end mill motor, wherein a working object to be machined to a flat sprocket gear is attached to the upper portion of the driven shaft of the driven gear, the working object having the same size as* the driven gear, whereby the second end mill forms a tooth form when the driven gear is rotated by the drive gear.

2. A device for forming a tooth form according to claim 1, wherein at least one of the left driven gear and the right driven gear in the tooth forming unit of a crown sprocket gear has a different gear tooth ratio at a certain proportion.

3. A device for forming a tooth form according to claim 1, wherein at least one of the drive gear and the driven gear in the tooth forming unit of flat sprocket gear has a different gear tooth ratio at a certain proportion.