WO1979000522A1

WO1979000522A1 - Drive system

Info

Publication number: WO1979000522A1
Application number: PCT/US1979/000016
Authority: WO
Inventors: R Williams
Original assignee: R Williams
Priority date: 1978-01-18
Filing date: 1979-01-15
Publication date: 1979-08-09
Also published as: IT7919404A0; US4342559A; IT1166582B; EP0008582A1

Abstract

A variable speed pulley and belt drive system (10) for use with bicycles, and for industrial drives, and the like. The system utilizes a variable diameter pulley and belt take-up member (22) to compensate for changes in the pulley diameter, said belt take-up member (22) preferably comprising a somewhat similar variable diameter pulley. Arcuate belt engaging segments (30) are provided between a fixed sideplate (26) and a movable sideplate (27) of the variable diameter pulley and pins (31) are provided at one side of each of the arcuate belt engaging segments to guide one side of each segment (30) in curved guide slots (29) in the fixed sideplate (26) and the other side of each arcuate belt engaging segment in straight slots (33) provided in the movable sideplate (27). Springs (37) interconnecting the fixed (26) and movable (27) sideplates are used to return the movable sideplate (27) in response to tension on the belt (25) passing around the arcuate belt engaging member (30).

Description

DESCRIPTION OF THE INVENTION Technical Field

This invention relates to variable speed, automatic drive systems utilizing pulleys and belts. Background Art

In the past there have been a great many variable speed drive systems developed for use with bicycles and the like. Some of the most common systems utilize sprockets of different sizes and shift a chain from sprocket to sprocket in order to obtain difierent drive ratios. Such systems do not provide for an infinitely variable drive and have proven difficult to maintain in service, since the apparatus used to change from sprocket to sprocket must be maintained in rather precise alignment to effect the shifting, and since such shifting apparatus is easily damaged or knocked out of alignment. Other systems have been developed for changing an effective sprocket diameter around which a chain is entrained. Such systems, are shown for example in U.S. Patent No.'s 3,800,613 and 3,938,403. The systems disclosed in such patents involve means for moving small sprocket wheels that are adapted to be engaged with a chain. In these disclosed systems, controlled means are provided to allow an operator to manually set the drive ration, within the range permitted by the design of the apparatus used. In U.S. Patent No. 3,769,849, there is disclosed a variable speed belt drive for use with bicycles and the like. The drive system disclosed in this patent provides for an infinite variety of ratios between high speed and low speed extremes and to achieve such ratios uses tapered belts, variable pulleys, and lever means to apply tension to change the diameter of a variable control pulley. None of the patents or prior art with whicli I am familiar disclose a variable pulley having a belt engaging surface that will engage the undersurfaces of a belt, and wherein the belt engaging surface of the pulley is movable to change the overall diameter oi the belt engaging portion around which the belt is entrained.

While the drive systems shown in the prior art appear to be useful and many will accomplish the desired objective of changing the torque required of the pulley and belt system, they are not entirely suitable since they generally require a large number of components and are difficult to construct, or they do not provide for adeqυate pulley surface-belt engagement to effect a continuous non-slip drive system.

Disclosure of Invention

Principal objects of the present invention are to provide an automatic pulley-bolt drive system that is reliable in operation and that requires little maintenance for long term, trouble free operation.

Principal features of the invention include a belt engaging pulley having a fixed sidewall and a spacea apart movable sidewall. Arcuate belt engaging sectors are provided between the sidewalls and are mounted to be guided in curved slots provided therefore in the fixed sidewall and in straight slots provided therefor in the movable sidewall. Springs having one end anchored to the fixed sidewall and the other end anchored to the movable sidewall are adapted to re-position xhe movable sidewall in respect to the fixed sidewall after the movable sidewall has rotated with respect to the fixed sidewall in response to tension changes in a belt passing over the arcuate belt engaging sectors and between the sidewalls.

Additional objects and features of the Invention will become apparent from the following derailed decription taken together with the accompanying drawings and claims. prefered as a belt take-up means i.u lake up slack in the belt 25 interconnecting the pulleys 22 and 24, other belt take-up means can be used.

As shown best in Figs. 2 and 3, the variable pulley 22 includes the sideplate 26 that is fixed to and movable with the crank arm 23. Another sideplate 27 is journaled on the crank arm 23 and is spaced from the fixed sideplate by a bushing 28. The fixed sideplate 26 has a series of paired curved slots 29 formed therein. The slots 29 are of identical configuration, with one end of each slot terminating on a circle spaced inwardly of and concentric with the outer edge of the outside edge of the sideplate 26. The other end of each slot 29 is similarly terminated on a smaller concentric circle such that each slot 29 will be curved from the end on the larger concentric circle to the end on the smaller concentric circle in the direction opposite to the rotation of the sideplate 26 during driving operation of the crank 23.

An arcuate, belt engaging sector 30 extends across each pair of slots 29 and a pin 31 projects from each end of each arcuate sector 30 through an adjacent slot 29 such that the head of the pin is on the outside of the fixed sideplate and the belt engaging sector 30 is between the fixed and movable sideplates.

The slots 33 each have an outer end on a circle that is concentric with the outer edge of the movable sideplate

27 and an inner end that is on a concentric circle spaced closer to the crank assembly 23 and opposite to the smaller concentric circle on which the ends of slots 29 on the fixed sideplate are positioned.

The fixed sideplate 26 is attached by scrows 34 to the bushing 28 that separates the sideplates 26 and 27. Bushing

28 has an attachment plate 35 affixed thereto and the attachment plate is then fixed to he crank assembly 23. The movable sideplate 27 has a support place 36 that fits rotatably around the crank assembly hoυsing.

A nυmber of coil springs 37 each have one end fixed to the support plate by a pin 38 and an opposite end affixed brief Description of Drawings

In the drawings:

Fig. 1 is a top plan view of the drive system of the invention shown mounted on a bicycle frame and with the frame and the pedal crunk assembly of the bicyele, shown fragmentarily;

Fig. 2, a side elevation view of the drive system of the invention as shown in Fig. 1, with additional parts removed for clarity; Fig. 3. an enlarged sectional view taken on the line 3-3 of Fig. 2;

Fig. 4, an enlarged sectional view taken on the line 4-4 of Fig. 2; and

Fig. 5, is an enlarged pictorial view of an arcuate belt engaging sector of the invention.

Best Mode of Carrying out the Invention Referring now to the drawings:

In the illustrated preferred embodiment, the drive system of the invention, shown generally at 10, is illustrated as being used with a bicycle shown generally at 11. As shown, the bicycle, which is shown only fragmentarily, is represented by bifurcated rear wheel support members 12 and 13 that extend rearwardly from n crank housing 14 to which are attached upstanding tubular frame members 15 and 16. A rear hub 17, having spokes 18 emenating therefrom as part of a wheel (th spokes and wheel being shown fragruontarily) is mount in conventional fashion to frame members 12 and 13 by lock nuts 20 and 21.

The drive assembly 10 of the invention includes a large variable speed pulley 22 attached to and rotatuble with the usual crank arm 23 of the bicycle pedal assembly. The crank arm 23 is shown fragmentarily, but it is to be understood that such crank arm is of conventional configuration and will have pedals (not shown) thereon through which the crank arm is rotated. A smaller variable speed pulley 24 of the invention is fixed to the hub 17 and rotates with the wheel of the bicycle. As will be further explained, while the smaller variable speedpulley is to the bushing 28 by a pin 39. Ench coil spring 37 extends from its pin 38 outwardly from the crank assembly housing in the direction of rotation of the pulley 22. The springs 37, thus normally bias the support plate 36 and the attached movable sideplate 27 such that the pins

31 are in the outermost ends of slots 29 and the pins

32 are in the outermost ends of the slots 33.

Variable speed pulley 24 serves to compensate for slack in the belt 25, as will bo further explained. The pulley 24 includes a fixed sideplate 40 and a spaced apart movable sideplate 41. As with the fixed sideplate 26, the fixed sideplate 40 has pairs of curved slots 42 formed therein. Each of the slots 42 has an outer end on a circle that is concentric with the outer edge of the fixed sideplate 40 and an inner end lying on a concentric circle of the hub 17, to which the sideplate 40 is affixed.

Also, like the movable sideplate 27, the movable sideplate 41 has pairs of straight slots 43 formed therein. The outer end of each slot 43 lies on a circle concentric with the outer edge of the movable sideplate 41 and spaced inwardly from the outer edge of the moveable plate. The inner end of each slot 43 lies on a smaller concentric circle closer to the hub 17 and preferably opposite to the inner ends of slots 42. Arcuate belt engaging sectors 45 are provided between the fixed sideplate 40 and the movable sideplate 41. Each arcuate belt engaging sector 45 has pins 46 projecting from one side thereof at opposite ends with pins extending through a pair of the slots 42 such that heads of the pins are outside of the affixed sideplate and the arcuate belt engaging sectors are inside the fixed sideplate. Similarly, pins 47 extend from the opposite sides of the arcuate belt engaging sectors at opposite ends thereof and through the pairs of slots 43 such that the heads of the pins 47 are outside the movable sideplate 41 while the arcuate sectors are inside the plate.

In the operation of the drive system 10, the crank assembly 23 is turned in conventional fashion by an operator pushing on pedals (not shown), attached to the crank assembly. With the drive assembly in the condition shown, wherein the arcuate belt engaging sectors 30 are at the outermost ends of the slots 29 and 33, and wherein the arcuate belt engaging sectors 45 of the variable pulley 24 are positioned at the innermost ends of the slots 42 and 43 the highest drive ration between the crank assembly and the wheel 19 is obtained. Rotation of the variable pulley 22 using the crank assembly 23 will drive the arcuate belt engaging sectors 45 and the hub 17 and wheel 19 attached thereto. As greater resistance develops to turning of the wheel 19, as for example when a user thereof is attempting to pedal the bicycle 11 up a hill, the resistance is transmitted through the upper run of the belt 25 to the arcuate belt engaging sectors 30 and 45 and such resistance will pull the arcuate belt engaging sectors 30 towards the inner ends of their slots 29 and 33, against the biasing effect of springs 37 and at the same time will pull the arcuate belt engaging sectors 45 outwardly with respect to their slots 42 and 43. Thus, as resistance to turning of the wheel 19 is increased, the effective diameter of the driving pulley, i.e. variable pulley 22 is decreased while the effected diameter of the driven pulley, i.e. variable pulley 24 is increased, to thereby change the drive ratio between the crank assembly 23 and the wheel 19.

The arcuate belt engaging sectors 30 and 45 are best shown in Fig. 5. As shown, each sector includes an arcuately shaped body portion 60 and sidewalls 61 and 62 projecting upwardly therefrom. The inner surfaces of the sidewalls 61 and 62 are inclined to match the angular side surfaces of the conventional V-belt 25. The upper surface of body 60 and the inner surfaces of sidewalls 61 and 62 are each made rough, for example by use of cross-scoring, as shown, to provide for a better fractional engagement with the belt 25.

While in the embodiment shown, the variable pulley 22 is a drive pulley and is shown larger than variable pulley 24, which is a driven pulley, it will be apparent that such relative sizes are entirely a matter of choice and that each pulley may be made larger or smaller, as desired. It will also be apparent that ono variable pulley can be used with a pulley of fixed diameter and that conventional belt adjusters may be used to keep the belt taut as the diameter of the variable pulleyused changes.

It should be further apparent that the strength of the springs will determine the degree of resistance required in the belt 25 to cause movement of the belt engaging sprocket sectors of the variable pulley or pulleys used and that the springs may bo varied, as required to achieve desired shifting characteristics.

Industrial Applicability

The present invention is useful as a means of varying the drive ratios of bicycles and other vehicles and for use as an industrial drive for machines and the like.

Although a preferred form of my invention has herein been disclosed, it is to be understood that the present disclosure is by way of example and that variations are possible without departing from the subject matter coming within the scope of the following claims, which subject matter I regard as my invention.

Claims

THE CLAI MSI Cl aim :

1. A drive system comprising a pair of pulleys; a belt drivingly engaged with said pulleys; at least one of said pulleys being a variable speed pulley and including a sideplate fixed with respect to a rotatable shaft; a movable sideplate spaced from said fixed sideplate and rotatable around the rotatable shaft; pairs of curved slots formed in the fixed sideplate, said curved slots each having one outer end spaced inwardly from an outer edge of the fixed sideplate and on a circle concentric with the outer edge and its other inner end on a smaller concentric circle, whereby said slots extend outwardly and in a direction of rotation of the sidewall; pairs of straight slots formed in the movable side- plate, each said straight slots having one outer end on a circle concentric with the cuter edge of the movable sideplate and its other inner end on a smaller concentric circle; and arcuate belt engaging sectors between said fixed and movable sidewalls. each said belt engaging sectors having means at opposite ends of one side thereof for guiding said belt engaging sector in a pair of said curved slots and means at opposite ends of an opposite side thereof for guiding said belt engaging sector in a pair of said straight slots.

2. A drive system as in Claim 1 , wherein at least one of the variable speed pulleys includes means resilientiy biasing the movable si deplete with respect to the fixed sideplate such that the belt engaging sectors are guided to the outer ends of the slots.

3. A drive system as in Claim 2, wherein the means resilientiy biasing the movable side-plate with .respect to the fixed sideplate comprises springs connected between the said sideplates.

4. A drive system as in Claim 1, wherein the belt engaging sectors have an arcuate belt engaging surface and upstanding sidewalls adapted to engage the belt.

5. A drive system as in Claim 4, wherein the belt engaging surface and the sidewalls are each provided with a rough surface to engage the belt

6. A drive system as in Claim 5. wherein both pulleys are variable speed pulleys, each including a fixed sideplate; a movable sideplate spaced from said fixed sideplate; pairs of curved slots formed in the fixed sideplate; said curve?d slots each having an outer end spaced inwardly from an outer edge of the fixed sideplate and on a circle concentric with the outer edge and its other inner end on a smaller concentric circle, whereby said slots extend outwardly and in a direction of rotation of the sideplate; pairs of straight slots formed in the movable sideplate, each said straight slot having one outer end on a circle concentric with the outer edge of the movable sideplate and its other inner end on a smaller concentric circle; and arcuate belt engaging sectors between said fixed and movable sidewalls, each said belt engaging sector having means at opposite ends of one side thereof for guiding said belt engaging sector in a pair of said curved slots and means at opposite ends of an opposite side thereof for guiding said belt engaging sector in a pair of said straight slots

7. A drive system as in Claim 6. wherein at least one o f the variable speed pulleys includes means resiliently biasing the movable sideplate with respect to the fixed sideplate such that the belt engaging sectors aro guided to the outer ends of the slots.

8. A drive system as in Clain 7, wherein the means resilientiy biasing the movable sideplate with respect to the fixed sideplate comprises springs connected between the said sideplates.

9. A variable pulley for use with belt drive systems comprising a sideplate adapted to be fixed to a rotatable shait; a movable sideplate spaced from said fixed s i depl ate and rotatable around the rotatable shaft; pairs of curved slots formed in the fixed sideplate, said curved slots each having one outer end spaced inwardly from an outer edge of the fixed sideplate and on a circle concentric with the outer edge and its other inner end on a smaller concentric circle, whereby said slots extend outwardly and in a direction or rotation of the sidewall; pairs of straight slots formed in the movable sideplate, each said straight slots having one outer end on a circle concentric with the outer edge of the movable sideplate and its other inner end on a smaller concentric circle; and arcuate belt engaging sectors between said fixed and movable sidewalls, each said belt engaging sector having means at opposite ends oJ one side thereof for guiding said belt engaging sector in a pair of said curved slots and means at opposite ends of an opposite side thereof for guiding said belt engaging sector in a pair of said straight slots.

10. A variable pulley as in Claim 9, further including means resilientiy biasing themovable sideplate with respect to the fixed sideplate suchthat the belt engaging sectors are guided to the outer ends of the slots.

11. A variable pulley as in Claim 10, wherein the means resilientiy biasing the movable sideplate with respect to the fixed sideplate comprises springs connected between the said sideplates.

12. A variable pulley as in Claim 11, wherein the belt engaging sectors have an arcuate belt engaging surface and upstanding sidewalls adapted to engage the belt.

13. A variable pulley as in Claim 12, wherein the belt engaging surface and the sidewalls are each provided with a rough surface to engage the belt.