WO2001027500A1

WO2001027500A1 - Automatic transmission pulley

Info

Publication number: WO2001027500A1
Application number: PCT/KR2000/001069
Authority: WO
Inventors: Hyungjin Do
Original assignee: Hyungjin Do
Priority date: 1999-09-27
Filing date: 2000-09-26
Publication date: 2001-04-19
Also published as: KR20000000161A; KR200170873Y1; AU1058201A; KR100352965B1

Abstract

Disclosed herewith is an automatic speed change pulley. The automatic speed change pulley includes a sleeve situated to be concentric with a drive shaft. A plurality of pulley segments are situated to be concentric with the drive shaft and to be spaced apart from the sleeve by a constant distance. The pulley segments transmit the power of the drive shaft to a driven shaft through a power transmitting member. Control means allows the outer diameter formed by the pulley segments to be radially inwardly reduced when an overload is exerted on the pulley segments, and restores the pulley segments to radially outwardly original positions when the overload is eliminated.

Description

Automatic transmission pulley

Technical Field

The present invention relates generally to pulleys used for power transmission apparatuses, and particularly to an automatic speed change pulley, m which the outer diameter of the pulley is automatically reduced to eliminate an overload when the overload is exerted on the pulley, and the rotational speed of the driven shaft of a power transmission apparatus is varied according to variations m the outer diameter of the pulley.

Background Art

With the development of industry, power generated by a power generation apparatus such as an engine or electric motor is utilized in various fields. Pulleys are widely utilized for power transmission apparatuses so as to transmit power generated by power sources to actual working machines.

Such pulleys may be classified into pulleys for simply transmitting power and pulleys for performing speed change as well as transmitting power.

Conventional pulleys are described in detail with reference to accompanying drawings . Fig. 1 is a view showing a conventional pulley that simply performs a power transmission function.

A pulley 10 fitted around a drive shaft 1 transmits power transmitted from the drive shaft 1 to a driven shaft 2 through a power transmitting member 11 such as a V-shaped belt.

While the pulley 10 transmits the power of the drive shaft 1 transmitted from the power source, such as the engine or motor, to the driven shaft 2, the pulley 10 cannot respond to a load acting on the driven shaft 2 during a starting operation and a load acting on the driven shaft 2 during a driving operation. Accordingly, the pulley cannot respond to the load during a driving operation, so there occur problems that a load acting on a power source (such as a motor or engine) is increased and an excessive waste of energy occurs. For the above reason, for a general pulley 10, the diameter of the pulley 10 is made to be relatively small to increase the speed change ratio and transmit a large amount of force m consideration of the prevention of a slip of the power transmitting member, or a belt and a load exerted from the driven shaft 2. Though this type pulley having a small diameter can transmit a large amount of force, the pulley has many problems in the consumption and utilization of energy.

A pulley having a speed change function is described with reference to Fig. 2. As is known well, in a continuously variable pulley, the rotational speed of a speed change pulley 20 is adjusted by moving an outer wheel 22 that is constructed to be operated together with an inner wheel 21.

That is, when the distance between the inner and outer wheels 21 and 22 of the pulley 20 is lengthened by the elastic force of a compression coil spring and centrifugal force, a load is exerted on the power transmitting member, or a belt held at a relatively large diameter and the power transmitting member is held at a relatively small diameter, thereby reducing the number of rotations of the driven shaft.

On the contrary, in order to increase the number of rotations of the driven shaft, continuously variable speed change can be achieved by properly changing the interaxial distance between the inner and outer wheels 21 and 22. The conventional speed change pulley 20 increases and reduces the number of rotations of the driven shaft by the interaxial distance between the inner and outer wheels 21 and 22. This technique requires a complicated mechanical structure to adjust the distance between the wheels, so difficulty in fabricating the pulley is incurred.

The speed change pulley has a complicated mechanical structure, so the volume of the speed change pulley is enlarged and the weight of the speed change pulley is increased, thereby lowering power transmission efficiency. Additionally, since the number of rotations of the speed change pulley 20 is increased and reduced by adjusting an interaxial distance utilizing the inner and outer wheels 21 and 22, two speed change pulleys 20 should be mounted to both of the drive and driven shafts, thereby causing the difficulty m mounting the pulleys 20 and incurring high costs.

Disclosure of the Invention

Accordingly, the present invention has been made keeping in mind the above problems occurring m the prior art, and an object of the present invention is to provide an automatic speed change pulley in which its outer diameter can be automatically adjusted according to exerted loads, thereby allowing power transmission to be smooth. Another object of the present invention is to provide an automatic speed change pulley that automatically changes the rotational speed of the driven shaft of a power transmission apparatus depending upon the variations of the outer diameter of the pulley, thereby preventing the loss of power and increasing energy efficiency.

In order to accomplish the above object, the present invention provides an automatic speed change pulley, comprising: a sleeve situated to be concentric with a drive shaft, the sleeve receiving power from the drive shaft; a plurality of pulley segments situated to be concentric with the drive shaft and to be spaced apart from the sleeve by a constant distance, the pulley segments transmitting the power of the drive shaft to a driven shaft through a power transmitting member; control means for connecting the sleeve and the pulley segments to transmit the power of the drive shaft to the pulley segments, allowing the outer diameter formed by the pulley segments to be radially inwardly reduced when an overload is exerted on the pulley segments, and restoring the pulley segments to radially outwardly original positions when the overload is eliminated; and two covers each provided with a plurality of pulley guide slots to guide the pulley segment when the pulley segments are moved.

Preferably, the control means comprises: a pair of flanges provided on the center portion of the outer surface of the sleeve; a plurality of connecting holes formed through the flanges; a plurality of engaging grooves formed on the inner surfaces of the pulley segments; a plurality of connecting pieces with their first ends rotatably connected to the connecting holes and their second ends rotatably engaged with the engaging grooves; a plurality of pulley guide projections formed on the pulley segments to guide the movement of the pulley segments by moving along the pulley guide slots formed on the covers; and a plurality of elastic springs secured to the pulley guide projections to provide elastic force so as to control the movement of the pulley segments. Alternatively, the control means may comprise: a plurality of connecting projections formed on the outer surface of the sleeve and each provided with a connecting hole; a plurality of support arms radially inwardly projected from the inner surfaces of the pulley segments and each provided with a through hole; a plurality of elastic springs formed to surround the outer surfaces of the support arms and compressed while the pulley segments are radially inwardly moved; a plurality of support members to both surfaces of which the covers are fixed, the support members supporting the elastic springs; a plurality of connecting pieces with their first ends rotatably connected to the connecting holes of the connecting projections and their second ends rotatably engaged with the through holes of the support arms; and a plurality of pulley guide projections formed on the pulley segments to guide the movement of the pulley segments by moving along the pulley guide slots formed on the covers .

The automatic speed change pulley may further comprise a tension roller for keeping the tension of the power transmitting member constant when the pulley segments are radially inwardly moved.

As a result, the present invention provides an automatic speed change pulley in which an outer diameter formed by pulley segments can be automatically adjusted according to loads exerted on the pulley. That is, when an overload s exerted on the pulley segments, the outer diameter formed by the pulley segments is reduced and a speed change ratio is increased, thereby allowing a large amount of force to be transmitted and causing power transmission to be smooth. When an overload is eliminated, the pulley segments are restored to their radially outward positions and the pulley provides high rotational speed, thereby preventing the loss of power and allowing power to be used effectively.

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 schematic diagram showing a conventional power transmission apparatus including a conventional pulley;

Fig. 2 is a schematic diagram showing a conventional power transmission apparatus including a conventional speed change pulley;

Fig. 3 is a perspective view showing a sleeve in accordance with a first embodiment of the present invention;

Fig. 4 is a perspective view showing an automatic speed change pulley in accordance with the first embodiment of the present invention; Fig. 5 is an exploded perspective view showing the automatic speed change pulley of the first embodiment;

Fig. 6 is a schematic diagram showing a power transmission apparatus including an automatic speed change pulley m accordance with a second embodiment of the present invention;

Fig. 7 is a perspective view showing the automatic speed change pulley of the second embodiment;

Fig. 8 is an exploded view showing the automatic speed change pulley of the second embodiment;

Fig. 9 is an exploded perspective view showing control means of the second embodiment; and

Fig. 10 is a view showing the operation of the automatic speed change pulley of the second embodiment.

Best Mode for Carrying Out the Invention

Hereinafter, the preferred embodiments of the present invention are described m detail with reference to accompanying drawings . <Fιrst embodιment>

Fig. 3 is a perspective view showing a sleeve in accordance with a first embodiment of the present invention.

Fig. 4 is a perspective view showing an automatic speed change pulley in accordance with the first embodiment of the present invention. Fig. 5 is an exploded perspective view showing the automatic speed change pulley of the first embodiment.

Hereinafter, the same reference numerals as those of Figs. 1 and 2 are used to designate the same elements as those of Figs. 1 and 2.

As depicted m the drawings, the automatic speed change pulley is generally comprised of a sleeve 100, pulley segments 200, control means 300 and a cover.

First of all, the sleeve 100 is described. The sleeve 100 has a cylindrical shape. A key groove 101 is longitudinally formed along the inner surface of the sleeve 100 to hold the sleeve 100 and a drive shaft 1 together. A key 102 is fitted into the sleeve 100 while the drive shaft 1 is inserted into the center hole of the sleeve 100, so the sleeve 100 is prevented from slipping out of the drive shaft 1 and is securely fixed to the drive shaft 1.

A through hole 103 is formed on the outer surface of the end portion of the sleeve 100 to be connected to the key groove 101 so as to prevent the sleeve 100 from being removed from the drive shaft 1 while the sleeve 100 is fitted over the drive shaft 1. The sleeve 100 fitted as described above receives power from the drive shaft 1 and transmits the power to the pulley segments 200.

Two flanges 110 shaped in the form of rings are formed around the center portion of the outer surface of the sleeve 100. A plurality of connecting holes 111 are formed to pass through the flanges 110 so as to be rotatably connected to connecting pieces 310. Two support projections 130 are formed on the outer surface of the sleeve 100 at two positions that are laterally outwardly spaced apart from the flanges 110 to be brought into contact with an inner cover 401. Two snap ring holding grooves 120 are formed on the outer surface of the sleeve 100 at two positions that are laterally outwardly spaced apart from the support projections 130 to hold snap rings 121 for securing the inner cover 401. Two snap ring holding grooves 120' are formed on the outer surface of the sleeve 100 at two positions that are laterally outwardly spaced apart from the snap ring holding grooves 120. Each support projection 130, each snap ring holding groove 120 and each snap ring holding groove 120' are formed on each half of the sleeve 100 by both sides of the flanges 110.

Next, the pulley segments 200 are described. The pulley segments 200 each have an arc shape having a predetermined width, and are comprised of a plurality of segments. At least one transmission member groove 201 is formed along the outer surfaces of the pulley segments 200 and the pulley segments 200 are arranged to be spaced apart from the sleeve 200 by a constant distance and be coaxial with the sleeve 200. In this case, the pulley segments 200 serve to transmit power supplied by the drive shaft 1 to a driven shaft 2 using a power transmitting member (such as a V belt, a chain or the like) .

Two pairs of pulley guide projections 210 are formed on the upper and lower surfaces of each of the pulley segments 200. The pulley guide projections 210 are formed to correspond to the pulley guide slots 410 formed through the inner covers 401. While the outer diameter formed by the pulley segments 200 is reduced or restored, the pulley guide projections 210 guide the movement of the pulley segments 200 by sliding along the pulley guide slots 410 of the inner covers 401.

Next, the control means 300 is described. The control means 300 generally comprises the flanges 110, engaging grooves 220, the connecting pieces 310, the pulley guide projections 210 and elastic springs 320. The flanges 110 are formed on the generally center portion of the outer surface of the sleeve 100 while being spaced apart from each other. The flanges 110 are provided with a plurality of connecting holes 111 into which one-side ends of the connecting pieces 310 are fitted. An accommodating groove 221 is formed on the inner surface of each pulley segment 200. The accommodating groove 221 serves to receive the flanges 120 of the sleeve 100 when the pulley segments 200 are moved radially inwardly. An engaging groove 220 is formed outside the accommodating groove 221 to communicate with the accommodating groove 221. The outer end of the connecting piece 310 is fixedly inserted into the engaging groove 220, and a holding hole 222 is vertically formed through each pulley segment 200 to be connected to the engaging groove 220 so as to be engaged with the pin formed on each pulley segment 200.

Next, the connecting pieces 310 are described. Each of the connecting pieces 310 has a rod shape of a predetermined width, is rounded at its both ends, and is provided with two connecting holes 111 at its both ends. One end of each of the connecting pieces 310 is inserted into a space between the flanges 110 formed on the sleeve 100 and is rotatably engaged with the connecting hole 111 formed on the flanges 110, while the other end is engaged with the engaging groove 220. The connecting pieces 310 adjusts the outer diameter formed by the pulley segments 200 in such a way that the connecting pieces 310 are moved together with the pulley segments 200 by the loads exerted upon the pulley segments 200 while an overload is exerted on the pulley segments 200.

That is, when an overload is exerted on the pulley segments 200, the connecting pieces 310 connected to the flanges 110 of the sleeve 100 are moved m the same direction as that of the sleeve 100 to cause the pulley segments 200 to be radially inwardly moved. In this case, the connecting pieces 310 are situated in the space between a pair of flanges 110. Two pairs of pulley guide projections 210 are formed on the upper and lower surfaces of each of the pulley segments 200, are situated m the pulley guide slots 410 formed through the inner covers 401 described later in more detail, and guide the movement of the pulley segments 200 by sliding along the pulley guide slots 410 of the inner covers 401. A connecting hole 211 is formed on each of the pulley guide projections 210 to hold one end of each of the elastic springs 320.

Each of the elastic springs 320 is coil-shaped, and its both ends are extended outwardly. One end of the elastic spring 320 is secured to the connecting hole 211 of each pulley guide projection 210 of one pulley segment 200, while the other end of the elastic spring 320 is secured to the connecting hole 211 of each pulley guide projection 210 of another pulley segment 200, thus providing elastic force to each pulley segment 200. The elastic spring 320 is connected outside the inner cover 401 after the pulley guide projections 210 are engaged with the pulley guide slots 410.

While an overload is exerted on the pulley segments 200 and the outer diameter formed by the segments 200 is reduced, the elastic springs 320 are deformed; whereas when the overload is eliminated, the elastic springs 320 provide restoring force to the pulley segments and restore the pulley segments to their original positions. The elastic springs 320 are not limited to coil type springs, but all types of springs that can provide elastic force like plate springs can be employed to the speed change pulley of the present invention.

The cover situated by both sides of the pulley segments 200 is comprised of two inner covers 401 and two outer covers 402.

Each of the inner covers 401 has a disk shape of a predetermined thickness. A center hole of a predetermined diameter is formed on the center of the inner cover 401, and accommodates the sleeve 100. A plurality of pulley guide slots 410 are formed on the inner cover 401 to be radially outwardly spaced apart from the center hole so as to guide the movement of the pulley guide projections 210. The pulley guide slots 410 each have a width and a length that allow the pulley guide projections 210 to be moved.

The inner cover 401 is secured by each support projection 130 of the sleeve 100 and each snap ring 121. The pulley grooves 410 are formed on the inner cover 401 to correspond to the pulley guide projections 310 of the pulley segments 200. A sleeve hole 403 is formed through the center of the outer cover 402. While the sleeve 100 is inserted into the sleeve hole 403 of the outer cover 402, the outer cover 402 is brought into contact with the outer surface of the inner cover 402. The elastic springs 320 engaged with the connecting holes 211 of the pulley guide projections 210 are situated m spaces in outer covers 402, so the displacement and removal of the elastic springs 320 are prevented.

The inner covers 401 and the outer covers 402 are situated on both sides of the pulley segments 200 by pair. The outer diameter formed by the pulley segments 200 is designed to be automatically varied by a load exerted on the pulley. When an overload is exerted on the pulley segments

200, the outer diameter formed by the pulley segments 200 is automatically reduced by radially inward force, thus allowing a large amount of force to be transmitted and causing power transmission to be smooth. When an overload is exerted upon the pulley segments 200, the outer diameter formed by the pulley segments 200 is restored to its original value by the elastic restoring force, thus allowing a large amount of rotating force to be transmitted and allowing power to be effectively transmitted without a large loss.

Another automatic speed change pulley different from the automatic speed change pulley is described in detail, hereinafter.

In this description, the same reference numerals as tnose of the first embodiment are used to designate the same elements of those of the first embodiment.

Fig. 6 is a schematic diagram showing a power transmission apparatus including an automatic speed change pulley in accordance with a second embodiment of the present invention. Fig. 7 is a perspective view showing the automatic speed change pulley of the second embodiment. Fig. 8 is an exploded view showing the automatic speed change pulley of the second embodiment. Fig. 9 is an exploded perspective view showing control means of the second embodiment. Fig. 10 is a view showing the operation of the automatic speed change pulley of the second embodiment.

As depicted in the drawings, the automatic speed change pulley of the second embodiment is generally comprised of a sleeve 100' , pulley segments 200' , control means 300' and a cover 400.

The sleeve 100' of the second embodiment has a cylindrical shape, and is provided with a plurality of connecting projections 140 at its outer surface. A key groove 101 is formed along the inner surface of the sleeve 100' to prevent the slip of the sleeve 100 and fix a drive shaft 1 securely, and a key 102 is fitted into the sleeve 100 along with the drive shaft 1. The sleeve 100' fitted as described above receives power from the drive shaft 1 and transmits power to the below-described pulley segments 200' .

The pulley segments 200' each have an arc shape having a predetermined width, and are comprised of a plurality of segments. A transmission member groove 201 is formed along the outer surfaces of the pulley segments 200' and the pulley segments 200' are arranged to be spaced apart from the sleeve 200' by a constant distance and be coaxial with the sleeve 200' . In this case, the pulley segments 200' serve to transmit power supplied by the drive shaft 1 to a driven shaft 2 using a power transmitting member (such as a V belt, a chain

Hereinafter, the control means 300' is described n detail with reference to Fig. 9.

As illustrated in the drawing, the control means 300' is generally comprised of the connecting projections 140, pulley guide projections 210, connecting pieces 310' , support projections 311, elastic springs 320' and support members 340.

The connecting projections 140 are projected from the outer surface of the sleeve 100' , and are each provided with a connecting hole 141 that is connected to each of the below- described connecting pieces 310' .

Each of cylindrical support arms 330 is projected from the inner surface of each of the pulley segments 200' . Each of the elastic springs 320' is positioned to surround the outer surface of each of the support arms 330. A through hole 331 is formed on one end of each of the support arms 330 to allow each of the connecting pieces 310' to be rotatably connected to the through hole 331 of the support arm 330.

As described above, each of the elastic springs 320' is arranged to surround the outer surface of each of the support arms 330. While the outer diameter formed by the pulley segments 200' is radially inwardly reduced by the application of an overload, the elastic springs 320' are compressed with its one end supported on the inner surfaces of the pulley segments 200' and its the other end supported on the outer surfaces of the support member 340. When the overload is eliminated, the pulley segments 200' are restored to their original positions by the restoring force of the elastic springs 320' . Each of the connecting pieces 310' has a rod shape of a predetermined width, is rounded at its both ends, and is provided with two connecting holes 311 at its both ends. One connecting hole 311 of the connecting piece 310' and the connecting hole 141 of the connecting projection 141 are used to rotatably connect the connecting piece 310' and the connecting projection 141, while the other connecting hole 311 and the through hole 331 of the support arm 330 are used to rotatably connect the connecting piece 310' and the support arm 330. When an overload is exerted upon the pulley segments 200' , the connecting pieces 310' directly adjust the outer diameter formed by rhe pulley segments 200' , by being moved while being connected to the sleeve 100' .

That is, while an overload is exerted upon the pulley segments 200' , connecting pieces 310 rotatably connected to the connecting projections 140 of the sleeve 100' are pulled in the same direction as that of the sleeve 100' , thereby causing the pulley segments 200' to be radially inwardly moved. At this time, each connecting piece 310' is situated in a predetermined space between the sleeve 100' and each support arm 330.

Next, the support members 340 are described. The support members 340 are arranged to be concentric with the drive shaft 1, supported by the elastic springs 320' on their outer surfaces, and provided with a plurality of bolt holes 341 that are used to secure below-described covers 400 to the support members 340. The support members 340 each have a curved rod shape of a predetermined width, are constantly spaced apart from the outer surface of the sleeve 100' , and are comprised of a plurality of members. Hereinafter, the covers 400 are described. Each of the covers 400 has a disk shape of a predetermined thickness. A center hole 420 of a predetermined diameter is formed on the center of each cover 400, and accommodates the sleeve 100' connected to the drive shaft 1. A plurality of bolt holes 430 are formed on the cover 400 at positions that are spaced aoart from the center hole 420 by a constant interval, to be useα to secure the cover 400 to the connecting members 340. A plurality of pulley guide slots 410 each having a predetermined length are formed through each cover 40C to guide the pulley guide projections 210 of the pulley segments The covers 400 are situated on both sides of the pulley segments 200 by pair. Since the covers 400 are provided with the pulley guide slots 410, the covers 400 can guide the pulley segments 200' smoothly by guiding the pulley guide projections 210 formed on the pulley segments 200' . The covers 400 are secured to the bolt holes 341 of the support arms 340 to keep the pulley segments 200' concentric with the drive shaft 1. A tension roller 500 is brought into contact with a power transmitting member 11 to keep the tension of the power transmitting member 11 constant. If the outer diameter of the pulley segments 200' is reduced by the application of an overload to the pulley segments 200' , the tension of the power transmitting member 11 is weakened, thereby preventing power transmitted from the drive shaft 1 from being transmitted to the driven shaft 2 effectively and causing the power transmitting member, or belt to slip. The tension roller 500 serves to keep the tension of the power transmitting member 11 constant by compensating for the problems. Since the tension roller 500 is well known, the detailed description is omitted here .

The operation of the automatic speed change pulley of the present invention is described, hereinafter. The order of power transmission is as follows; power is transmitted from the drive shaft 1 to the sleeve 100' , from the sleeve 100' to the connecting pieces 310 connected to the sleeve 100' , from the connecting pieces 310 to the pulley segments 200 rotatably connected to the connecting pieces 310, from the pulley segments 200 to the power transmitting member 11, such as a belt or chain, surrounding the pulley segments 200, and from the power transmitting member 11 to the driven shaft 2, sequentially.

A load exerted on the pulley segments 200 during a starting operation and an impact transmitted from the drive shaft 1 to the sleeve 100' are absorbed by the elastic springs 320 and the rotating force of the drive shaft 1 is transmitted to and rotates the sleeve 100' , and the plurality of connecting pieces 310 rotatably connected to the flanges 110 integrated with the outer surface of the sleeve 100 are pulled at the same time. When the connecting pieces 310 are pulled, the sleeve 100 and the connecting pieces 310 are moved together. At this time, the connecting pieces 310 are situated in the space between the pair of flanges 110, and the projected flanges 110 are situated in the accommodating grooves 221 of the pulley segments 200.

When one-side ends of the connecting pieces 310 rotatably connected to the sleeve 100 are moved together with the sleeve 100, the pulley guide projections 210 formed on the pulley segments 200 connected to the other-side ends of the connecting pieces 210 are radially inwardly moved along the pulley guide slots 410 formed through the inner covers 401, thereby causing the outer diameter formed by the pulley segments 200 to be reduced. At this time, the elastic springs 320 fixed to the connecting holes 211 of the pulley guide projections 210 are compressed.

The outer diameter formed by the pulley segments 200 is reduced by the operation, so a high speed change ratio can be achieved, thereby allowing strong rotating force to be transmitted to the driven shaft 2.

When the load is eliminated and the rotation is smoothed by the operation, the pulley segments 200 are restored to their radially outward positions by centrifugal force caused by the rotation of the pulley segments 200 and the elastic restoring force of the elastic springs 320. When the overload is eliminated as described above, the pulley segments 200 are radially outwardly moved, thereby allowing high-speed rotational force to be transmitted to the driven shaft 2.

When an overload occurs during a normal operation after start, the pulley segments 200 are moved as described above, thereby eliminating the overload transmitted to the drive shaft 1.

Industrial Applicability As described above, the present invention provides an automatic speed change pulley in which an outer diameter formed by pulley segments can be automatically adjusted according to loads exerted on the pulley. That is, when an overload is exerted on the pulley segments, the outer diameter formed by the pulley segments is reduced and a speed change ratio is increased, thereby allowing a large amount of force to be transmitted and causing power transmission to be smooth. When an overload is eliminated, the pulley segments are restored to their radially outward positions and the pulley provides high rotational speed, thereby preventing the loss of power and allowing power to be used effectively. Accordingly, the automatic speed change pulley can be used for various power transmission apparatus. For example, the automatic speed change pulley can be applied to special purpose machinery, such as a cultivator, tractor or transplanter, internal combustion engines for automobiles, household appliances, ships, bicycles, motorcycles and the like.

In addition, the automatic speed change pulley of the present invention can lengthen the life span of an apparatus by the prevention of the wear of a power source, so the considerable portion of the costs of the apparatus can be saved.

?-?

Claims

1. An automatic speed change pulley, comprising: a sleeve situated to be concentric with a drive shaft, said sleeve receiving power from said drive shaft; a plurality of pulley segments situated to be concentric with said drive shaft and to be spaced apart from said sleeve by a constant distance, said pulley segments transmitting the power of said drive shaft to a driven shaft through a power transmitting member; control means for connecting said sleeve and said pulley segments to transmit the power of said drive shaft to said pulley segments, allowing the outer diameter formed by said pulley segments to be radially inwardly reduced when an overload is exerted on said pulley segments, and restoring said pulley segments to radially outwardly original positions when the overload is eliminated; and two covers each provided with a plurality of pulley guide slots to guide said pulley segment when said pulley segments are moved.

2. The automatic speed change pulley according to claim 1, wherein said control means comprises: a pair of flanges provided on the center portion of the outer surface of said sleeve; a plurality of connecting holes formed through said flanges; a plurality of engaging grooves formed on the inner surfaces of said pulley segments; a plurality of connecting pieces with their first ends rotatably connected to said connecting holes and their second ends rotatably engaged with said engaging grooves; a plurality of pulley guide projections formed on said pulley segments to guide the movement of said pulley segments by moving along said pulley guide slots formed on said covers; and a plurality of elastic springs secured to said pulley guide projections to provide elastic force so as to control the movement of said pulley segments.

3. The automatic speed change pulley according to claim 1, wherein said control means comprises: a plurality of connecting projections formed on the outer surface of said sleeve and each provided with a connecting hole; a plurality of support arms radially inwardly projected from the inner surfaces of said pulley segments and each provided with a through hole; a plurality of elastic springs formed to surround the outer surfaces of said support arms and compressed while said pulley segments are radially inwardly moved; a plurality of support members to both surfaces of which said covers are fixed, said support members supporting said elastic springs; a plurality of connecting pieces with their first ends rotatably connected to the connecting holes of said connecting projections and their second ends rotatably engaged with the through holes of said support arms; and a plurality of pulley guide projections formed on said pulley segments to guide the movement of said pulley segments by moving along said pulley guide slots formed on said covers .

4. The automatic speed change pulley according to claim 1 or 2, further comprising a tension roller for keeping the tension of said power transmitting member constant when said pulley segments are radially inwardly moved.