DRIVE SYSTEM

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 10. 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 15. 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 sproc¬ ket in order to obtain difierent drive ratios. Such systems do not provide for an infinitely variable drive and have 20. proven difficult to maintain in service, since the appar¬ atus used to change from sprocket to sprocket must be maintained in rather precise alignment to ef ect the shift¬ ing, and since such shifting apparatus is easily damaged or knocked out of alignment. Other systems have been developed 25. for changing an effective sprocket diameter around which a chain is entrained. Such systems, are shown for exampl in U.S. Patent No. 's 3,800,613 and 3,938,403. The systems dis¬ closed in such patents involve means for moving small sproc¬ ket wheels that are adapted to be engaged with a chain. In 30. 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 vari¬ able speed belt drive for use with bicycles and the like. 5_ 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 BA β ORIGINAL li belts, variable pulleys, and level- means to apply tens to change the diameter of a variable control pulley. None of the patents or prior art w th whicli I am familiar disclose a variable pulley having a belt enga 5. ing surface that will engage the undersurfaces of a be and wherein the belt engaging surface of the pulley is movable to change the overall diameter oi the belt eng ing portion around which the belt is entrained. While the drive systems shown in the prior art app 10. to be useful and many will accompl i h the desired obje tive of changing the torque requi red of the pul ley 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 ade 15. qυate pulley surface-belt engagement to effect a conti uous non-slip drive system. Disclosure of Invention Principal objects of the present invention are to 20. provide an automatic pulley-bolt drive system that i.s reliable in operation and that requires Little mainten ance for long term, t ouble free operation. Principal features of the invention include a belt engaging pulley having a fixed sidewall and a spaceu 25. apart able sidewall. Arcuate belt engaging sector.-., are provided between the sidewalls and are mounted to be guided in curved slots pi-uvi riod therefore * in the fixed sidewall and in straight slots provided therefor in the movable sidewall. 30. Springs having one end anchored to the fixed side¬ wall and the other end anchored to the movable sidewal are adapted to re-position xhe movable sidewall in re¬ spect to the fixed sidewall after the movable sidewall has rotated with respect to the fixed sidewall in re- 35. sponse o tension changes in a belt passing over the arcuate belt engaging sectors and between the side all Additional objects and features of the Invention will becom apparent from the following derailed d"- cription taken together with the accompany ng dravings and cl ims. 1 i 4 prefered as a belt take-up means i.u lake up slack in the belt 25 interconnecting the pull'-ys 22 and 24, other b**-lt take-up means can be used. 5. As shown best in F gs. 2 and , he variabl 1 pullov 22 includes the sideplate 26 that is iixoα to and movable with the crank arm 23. Another sideplate 27 is journaled on the crank arm 23 and is spaced from the fi ed sideplate by a bushing 28. The ixed sideplate 26 has a series of 10. paired curved slots 29 formed the ein. The .--.lots 29 ru 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 15. on a smaller concentric circle such that each slot 29 will be curved from the end on the rger 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. 20, An arcuate, belt engaging sector 30 extends across each pair of slots 29 and a pin 31 projects from e ch end oi each arcuate sector 30 through an ad acent slot 29 such that the head of the pin is on the outside of the fixed sideplate and the belt engaging seder 30 is between the q . fixed and movable sideplates. The slots 33. each have an outer end on a circle that is concentric with the outer edge o 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 30. concentric circle on which the ends of slots 29 on the fixed sideplate are positioned. The fixed sideplate 26 is ati ached by screws 3-i to the bushing 28 that separates the sideplates 26 and 27. 3ush ; ng 28 has an attachment plate 35 nu ' i.vd the e and the .->q attachment plate is then Jixod to * he crank asserbly 23. The movable sidep ate 27 has a up o t place 36 that fits rotatably around the crar.k assembly hoυsirg. Λ nυmi --r of coil springs 37 "luh have one end fixed to the support plate by a pin 38 and an opposite end aifix-d BABORIGINAL 3 - 1 *. brief Description of D awing 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 5. frame and the pedal crunk as embly of the* bi^yel , shown ragmen rily ; Fig. 2, a side elevation vi t.-w of the drive system of the invention as shown in Fig. 1, with additional parts removed for clarity; 10. Fig. 3. an enlarged sectional view taken on the line 3-3 of Fig. 2; Fig. 4, an enlarged sectional view taken on the l .ne 4-4 of Fig. 2; and Fig. 5, is an enlarged pictorial view of an arcuate lύ * . belt engaging sector uf the invention. Best Mode of Carrying out the Invent!on Referring now to the drawings: In the illustrated preferred embodiment, the drive 20. system of the invention, shown generally a 10, is ill¬ ustrated as being used with a bicycle shown generally at 11. As shown, the bicycle, which is shown only frag- mentarily, is represented by bifurcated rear wheel sup¬ port members 12 and 13 that extend rearwardly from n 25. crank housing 14 to which are attached upstanding tub¬ ular 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 fragruontari ly) is mount i in conventional fashion to frame members 12 and 13 by 30. lock nuts 20 and 21. The drive assembly 10 of the invention includes large variable speed pulley 22 attached to and rotat ble with the usual crank arm 23 of the bicycle pedal assembl The crank arm 23 is shown fragrhc-ntariiy, but it is to be 35 _ understood that such crank arm is of conventional config¬ uration and will have pedals (not shown) thr-reon 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 furthe -.;xplallied, while the smaller variable speed pulley is to the bushing 28 by a pin 39. Knch c.oi 1 spring 37 ex¬ tends from its pin 38 outwardly from the crank assembly housing in the direction of rotation of the pulley 22. 5. 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 10. 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 pa rs of curved slots 42 formed therein. Each of the slots 42 has an outer end on 15. a circle that is concentric w th 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 side¬ p ate 41 has pairs of strai ht slots 43 formed therein. 20. 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 oveable plate. The inner end of each slot 43 lies on a smaller concentric- circle closer to the hub 17 and preferably opposite to 25. 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 oppo¬ site ends with pins extending through a pair of the slots 30. 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 pai s of slots 43 3 . such that the heads of the pins 47 are outside the mov¬ able 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 oper¬ ator pushing on pedals (not shown), attached to the crank BAB 1. assembly. With th * 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 5. 24 are positioned at the innermost ends of the slots 42 and 43 the highest drive ration between the crank assemb and the wheel 19 is obtained. Rotation of the variable pulley 22 using the crank assembly 23 will drive the ar¬ cuate belt engaging sectors 45 and the hub 17 and wheel 10. 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 15. 45 and such resistance will pull the arcuate belt engag¬ ing sectors 30 towards the inner ends of their slots 29 and 33, against the biasing effect * >f springs 37 and at the same time will pull the arcuate belt engaging sec¬ tors 45 outwardly with respect to their slots 42 and 43. 20. Thus, as resistance to turning of the wheel 19 is in¬ creased, the effective diameter o i ' 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 25. 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 ar- cuately shaped body portion 60 and sidewalls 61 and 62 projecting upwardly therefrom. The inner surfaces of 30. the sidewalls 61 and 62 are inclined to match the angula side surfaces of the conventional V-belt 25. The upper surface of b*κϊy 60 and the inner surfaces of sidewa 1 is 6 and 62 are each made rough, for example by use of cross- scoring . , as shown, to provide for a better fractional en 35. gagement with the belt 25. While in the err.b-'di ent .shown, the variable pulley 22 is a drive pulley ;- r. d is shown larger than variable pulley 24, which is a driven pulley, it will be apparent that -such relative sizes are -.-ntirely a natter of choice and that each pul ey m y li made larger or s::.?ll r, as 1- desired. It will also be apparent that on variable pulley can be used wi h a pulley of fixed diameter and that conventional belt adjusters may be used to keep the belt taut as the diameter of the variable pulle¬ s ' used changes. It should be further apparent that the: strength of the springs will determine the degree of resistance re¬ quired in the belt 25 to cause movement of the belt en¬ gaging sprocket sectors of the variable pulley or pulleys 10. used and that the springs may bo varied, as required to achieve desired shifting characteri tics. Industrial Applicability The present invention is useful as a means of vary¬ 15, ing the drive ratios of bicycles and other vehicles and for use as an industrial drive for machines and the like. Although a preferred form oi ' h.y invention has herein been disclosed, it is to be understood that the * present disclosure is by way of example and that variations rc- 20, possible without departing from the subject matter coming within the scope of the following cl ims, which subject matter I regard as mv invention. 25, 30, 35. BAB

Claims: 1 . TII CLAI MS I Cl aim : 1. A drive system comprising a pair of pulleys; 5. a belt drivingly engaged with said pulleys; at least one of said pulleys being a variable sp_*ed pulley and including a sideplate fixed with respect to a rotatable shaft; a movable sideplate spaced from said fixed sideplat 10. 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 15. 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 4 sidewall ; pairs of straight slots formed in the movable side- 20. plate, each said straight slots having one oute 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 ;.n 25. movable sidewalls. each said belt engaging se t means at opposite ends of one side there for guiding said belt engaging sector in a pair of said curved slots and means at opposite ends of an opposite s de thereof for guiding sa d 30. 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 35. means resilientiy biasing the movable si deplete wit respect to the fixed sideplate s.uch that the be engaging sectors are guided to the outer ends o the slots. BAB OR1GHNA 1. A dr ve system as n Claim 2, wherein the means resilientiy biasing t e movable side-plate with .respect to the fixed sideplate comprises springs connected between the said sideplates. 5. A drive system as in Claim 1, wherein the belt engaging sectors have an arcuate belt engag¬ ing surface and upstanding sidewalls adapted to engage the belt. 10, 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 15 A drive system as in Claim 5. wherein both pulleys are variable speed pulleys, each includ¬ ing a fixed sideplate; a movable sideplate spaced from said fixed side¬ plate; pairs of curved slots formed in the xed 20 sideplate; said curv?d slots each having an outer end spaced inwardly from an outer edge of the fixed sideplate and on a circle con¬ centric with the outer edge and its other inner end on a smaller concentric circle, where¬ 25 by said slots extend outwardly and in a direc¬ tion of rotation of the sideplate; pairs of straight slots formed in the movable side¬ plate, each said straight slot having one outer end on a circle concentric with the outer edge of 30, 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 end.-, of one 35 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 sec¬ tor in a pair of said straight slots. 1. 7. A drive .system as in Claim 6. wherein at least, one; [ the variable speed pul leys includes means resilientiy biasing the movable sideplate with respect to the fixed sideplate such that 5. the belt engaging sectors r gui ed to the outer ends of the slots. 8. A drive system as in Clain 7, wherein the means resilientiy biasing the movable sideplate 10. 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 te) be fixed to a 15. rotatable shait; a movable sideplate spaced from said fixed sideplate and rotatable around the rot t jjle shaft; pairs of curved slots formed in the fixed sideplate, said curved slots each having one outer end space 20. inwardly from an outer edg f> of the ϊixed sideplat and on a circle concentric, with the outer edge an its other inner end on a smaller concentric circl whereby said slots extend outwardly and in a di ¬ ection or rotation of the sidewall; 25. pairs of straight slots forme/d in the movable side¬ plate, each said straight slots having one outer end on a circle concentric wi h the outer edge of the movable sideplate and its other inner end on a smaller concentric circle; and 30. 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 o said curved slots and means at opposite ends of a 35 _ opposite side thereof for guiding said belt engag ing sector in a pair of said straight slots. 10. A variable pulley as in Claim 9, further including means resilientiy biasing tin * movable sideplate with respect to the fixed sideplate such that the be t 2A 1. engaging sectors are guided to the outer ends of the slots. 11. A variable pulley as in Claim 10, wherein 5. 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 10. the belt engaging sectors have an arcuate belt en¬ gaging surface and upstanding sidewalls adapted to engage the belt. 13. A* ariable pulley as in Claim 12, wherein 15. the belt engaging surface and the sidewalls are each provided with a rough surface * to engage the belt 20 25 30, 35, BURt,T -

Inventors: WILLIAMS R
Applicants: WILLIAMS R
Application year: 1979
Main classification: B62M9
IPC codes: B62M9, F16H9