CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority benefit of U.S. Provisional Patent

Application Serial No. 61/205,098 filed January 15, 2009.

BACKGROUND OF THE INVENTION Field of Invention

[0002] The invention relates to vehicles having belt drive systems and, more particularly, to vehicles, such as riding lawn mowers, which utilize a transaxle having a single control lever for controlling direction and speed of the vehicle.

Description of Related Art

[0003] It is known to use a transaxle and a belt drive system on a vehicle such as a riding mower to drive the vehicle in both the forward and reverse directions. In some applications, it is known to have the vehicle's engine drive a first belt which acts either directly or indirectly on a variator which in turn causes a second belt to drive the input sheave to the transaxle. By varying the tension on the first belt, the variator increases or decreases the speed of rotation of the second belt. The benefit of using a vehicle belt drive, as described, is that the performance characteristic of a hydrostatic drive may be simulated without incurring the requisite expense associated with conventional hydrostatic transmissions.

[0004] However, these applications typically use separate controls to shift the transaxle from a forward to a reverse operating mode. Therefore, a separate control is necessary for directional change from that used to vary the speed of the belt drive. If vehicle direction and speed could be controlled by a single control lever, much like that employed in conjunction with vehicles having hydrostatic transmissions, it would enhance operator convenience and simplify the operation thereof. Thus, there is a need for a single lever control for a vehicle belt drive which provides for both direction and speed control. SUMMARY OF THE INVENTION

[0005] The invention is directed to an improved a belt drive system for a vehicle such as a riding lawn mower. The belt drive system includes a prime mover and an output double-stacked pulley rotated by the prime mover. The belt drive system also includes a triple-stacked variable speed pulley between the output pulley and a transaxle input pulley. A forward belt drive system operatively connects a first sheave of the output pulley to a first sheave of the variable speed pulley, and a reverse belt drive system operatively connects a second sheave of the output pulley to a second sheave of the variable speed pulley. A third sheave of the variable speed pulley is connected by a transmission belt to the transaxle input pulley connected to the input shaft to the transaxle. The forward belt drive system rotates the input shaft of the transaxle in a first direction to drive the vehicle in a forward direction, and the reverse belt drive system rotates the input shaft in the opposite direction to drive the vehicle in a reverse direction.

[0006] Another aspect of the invention is directed to a vehicle such as a lawn or garden tractor. The vehicle includes a prime mover, a transaxle having an input shaft, and a pair of ground-engaging drive wheels connected to the transaxle. A belt drive system connects the prime mover to the transaxle in order to rotate the drive wheels so as to provide locomotion to the vehicle. The belt drive system includes an output double-stacked pulley rotated by the prime mover. The belt drive system also includes a triple-stacked variable speed pulley between the output pulley, and a transaxle input pulley. A forward belt drive system operatively connects a first sheave of the output pulley to a first sheave of the variable speed pulley and a reverse belt drive system operatively connects a second sheave of the output pulley to a second sheave of the variable speed pulley. A third sheave of the variable speed pulley is connected by a transmission belt to the transaxle input pulley connected to the input shaft to the transaxle. The forward belt drive system rotates the input shaft of the transaxle in a first direction to drive the vehicle in a forward direction, and the reverse belt drive system rotates the input shaft in the opposite direction to drive the vehicle in a reverse direction. [0007] These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of various exemplary embodiments of the systems and methods according to this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The structure, operation, and advantages of the presently disclosed embodiment of the invention will become apparent when consideration of the following description taken in conjunction with the accompanying drawings wherein: [0009] FIG. 1 is a perspective view of a vehicle having a belt drive control system according to the invention;

[0010] FIG. 2 is an exploded perspective of the belt drive control system of the vehicle of HG. 1;

[0011] FIG. 3 is a plan view of a portion of the belt drive control system of

FIG. 2;

[0012] FIG. 4 is side view of the portion of the belt drive control system of

FIG. 3;

[0013] FIG. 5 is a cross-sectional view of a variable speed pulley of the belt drive control system in a neutral condition;

[0014] FIG. 6A is a cross-sectional view of the variable speed pulley in a forward low-speed condition;

[0015] FIG. 6B is a cross-sectional view of the variable speed pulley in a forward high-speed condition;

[0016] FIG. 7A is a cross-sectional view of the variable speed pulley in a reverse low-speed condition;

[0017] FIG. 7B is a cross-sectional view of the variable speed pulley in a reverse high-speed condition;

[0018] FIG. 8 is a plan view of a portion of another embodiment of the belt drive control system; and

[0019] FIG. 9 is side view of the portion of the belt drive control system of

FIG. 8. [0020] Corresponding reference characters indicate corresponding parts throughout the views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0021] The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

[0022] Referring now to the drawings, FIG. 1 shows a vehicle, such as a lawn and garden tractor or riding mower, generally indicated at reference number 10. The vehicle 10 includes a prime mover such as an internal combustion engine 12 mounted to a structural frame or chassis 14. The vehicle 10 includes left and right drive wheels 16 located toward the rear of the vehicle 10 and right and left front ground- engaging wheels 18. As seen in FIG. 2, the chassis 14 has fixably mounted thereto by any conventional means a transaxle 20 which may perform the function of a gear box, transaxle and brake. Extending transversely from each side of the transaxle 20 is a drive axle 19 fixably mounted to a respective drive wheel 16 by any conventional means. The engine 12 is operatively connected to the transaxle 20 with a belt drive control system, generally designated by reference number 21, so as to provide locomotion to the vehicle 10.

[0023] Returning to FIG. 1 , the chassis 14 also supports an operator station comprising a seat 22. A steering input member 24 and a speed input member 28 are located near the seat 22 so that they are accessible to the operator of the vehicle 10. The steering input member 24 provides steering inputs and may take the form of a conventional steering wheel. However, it is expressly noted that the steering wheel 24 may be another suitable steering control mechanism chosen with sound engineering judgment including, but not limited to, a steering rod or joystick (not shown). According to the invention, the speed input member 28 is desirably a foot pedal and regulates the direction and speed of the vehicle 10 in both the forward and reverse directions. The foot pedal 28 is desirably mounted such that the foot pedal 28 is rocked forward by pressing down in a forward direction to select forward drive, or rocked backward by pressing down in a rearward direction to select reverse drive. Although the illustrated embodiment shows the speed input member 28 as being a foot pedal, one skilled in the art will understand that the speed input member may also be a hand control lever without departing from the scope of the invention. Desirably, the foot pedal 28 is biased toward a central position, corresponding to a neutral or stationary condition. A brake pedal (not shown) is also located near the seat 22 and configured to engage a brake system to brake the vehicle 10 via means known in the art. The brake system desirably interacts with the belt drive control system 21 such that the brake can be set in a parking brake mode only when the control system is in a neutral condition or the brake system forces the control system into the neutral condition when set.

[0024] The belt-drive control system 21 for the vehicle 10 will now be described with respect to FIGS. 2-4. A double-stacked engine output drive pulley 42 is mounted on the drive shaft (not shown) of the engine 12 in any manner commonly known in the art. A driven transaxle input pulley 44 is mounted on the transaxle 20 for receiving torque from the engine 12 and the engine output pulley 42. The transaxle input pulley 44 is desirably a single pulley connected to the input shaft 46 of the transaxle 20 in any manner commonly known in the art.

[0025] According to the invention, a triple-stacked variable speed pulley 50 operatively connects the engine output pulley 42 with the transaxle input pulley 44. Torque is supplied by the engine output pulley 42 to the variable speed pulley 50 through either a forward belt drive system 100 or a reverse belt drive system 200. The forward belt drive system 100, utilizing a forward-direction drive belt 101, operatively connects a first drive pulley 102 of the double-stacked engine output pulley 42 to a forward drive pulley 103 of the triple-stacked variable speed pulley 50. The reverse belt drive system 200, utilizing a reverse-direction drive belt 201, connects a second drive pulley 202 of the engine output pulley 42 to a reverse drive pulley 203 of the variable speed pulley 50. A rear transmission drive belt 51 connects a transmission pulley 53 of the variable speed pulley 50 to the transaxle input pulley 44 of the transaxle 20. Desirably, the forward-direction drive belt 101, the reverse- direction drive belt 201 and the rear transmission belt 51 are conventional v-belts known to those skilled in the art. The forward-direction and reverse-direction drive belts 101, 201 are routed to turn the variable speed pulley 50 in opposite directions, and depending on which drive system, the forward belt drive system 100 or the reverse belt drive system 200 is engaged through operation of the foot pedal 28. Both belt drive systems 100, 200 share the rear transmission drive belt 51 that connects the variable speed pulley 50 to the transaxle input pulley 44. The forward belt drive system 100 rotates the variable speed pulley 50 in a first or forward direction (clockwise in the illustrated embodiment) thereby causing the transaxle 20 to drive the vehicle 10 in a forward direction, while the reverse belt drive system 200 rotates the variable speed pulley 50 in the opposite or reverse direction so as to cause the transaxle 20 to drive the vehicle in a reverse direction. It therefore can be seen that the rear transmission drive belt 51 can travel in either direction, depending on the input to the variable speed pulley 50.

[0026] As best seen in FIG. 4, the forward-direction drive belt 101 connects the first pulley 102 of the engine output pulley 42 to the forward drive pulley 103 of the variable speed pulley 50 for selective rotation of the variable speed pulley 50. In one embodiment, the forward-direction drive belt 101 is wound around a first fixed pulley 104 and a second pulley 106 mounted on a pivoting bracket 108. The second pulley 106 rotates around an axle 110 mounted on the pivoting bracket 108. A biasing spring 112 is connected between the chassis 14 and the bracket 108. However, tension in the forward-direction drive belt 101 may be controlled with other means known in the industry using sound engineering judgment. The spring 112 biases the bracket into a neutral condition that causes the forward-direction drive belt 101 to be slacked. In this neutral position, the pulley 106 mounted on the bracket 108 permits the forward-direction drive belt 101 to slack such that the forward-direction drive belt 101 slips with respect to the first pulley 102 of the engine output pulley 42 and the forward drive pulley 103 of the variable speed pulley 50. In this condition, the forward belt drive system 100 does not cause a forward rotation of the variable speed pulley 50, and no forward input is provided to the transaxle 20. Pivoting movement of the bracket 108 against the biasing force of the spring 112 causes the pulley 106 to place a tension in the forward-direction drive belt 101. Therefore, movement of the bracket 108 using the foot pedal 28 controls the tension of the forward-direction drive belt 101 and varies the forward speed of the vehicle 10 as will be described below.

[0027] The reverse-direction drive belt 201 connects the second pulley 202 of the engine output pulley 42 on the drive shaft to the reverse drive pulley 203 of the variable speed pulley 50. In one embodiment, the reverse belt drive system 200 comprises the reverse-direction drive belt 201 wound around a first fixed pulley 204 and a second pulley 206 mounted on a pivoting bracket 208. As can be seen, the reverse-direction drive belt 201 is wound such that the reverse belt drive system 200 is configured to rotate the variable speed pulley 50 in the opposite direction than the forward belt drive system 100. The second pulley 206 rotates around an axle 210 mounted on the pivoting bracket 208. A biasing spring 212 is connected between the chassis 14 and the bracket 208. However, tension in the reverse-direction drive belt 201 may be controlled with other means known in the industry using sound engineering judgment. The spring 212 biases the bracket 208 into a neutral condition that causes the reverse-direction drive belt 201 to be slacked. In this neutral position, the pulley 206 mounted on the bracket 208 permits the reverse-direction drive belt 201 to slack such that the reverse-direction drive belt 201 slips with respect to the second pulley 202 of the engine output pulley 42 and the reverse drive pulley 203 of the variable speed pulley 50. In this condition, the reverse belt drive system 200 does not cause a reverse rotation of the variable speed pulley 50, and no reverse input is provided to the transaxle 20. Pivoting movement of the bracket 208 against the biasing force of the spring 212 causes the pulley 206 to place a tension in the reverse- direction drive belt 201. Therefore, movement of the bracket 208 using the foot pedal 28 controls the tension of the reverse-direction drive belt 201 and varies the reverse speed of the vehicle 10 as will be described below. [0028] Referring back to FIG. 2, a pivotable shaft 58 is conventionally connected to the chassis 14 of the vehicle 10 such that it extends transversely across the chassis 14. Operatively connected to the shaft 58 is the foot pedal 28 such that movement of the foot pedal 28 causes rotation the shaft 58 in a first direction (clockwise in the illustrated embodiment) when pressed in the first direction and pressing down on the foot pedal 28 in a second direction causes the shaft 58 to rotate in the second direction. Two cams 120 and 220 are conventionally mounted on the shaft 58. The first cam 120 is a forward direction control cam, and the second cam 220 is a reverse direction control cam.

[0029] In the illustrated embodiment, the reverse direction control cam 220 has a cam slot 222 formed therein. A cam follower 224 is slideably mounted within the cam slot 222. The cam follower 224 is conventionally pivotally mounted to one end of a cam link 226. The opposite end of the cam link 226 is connected to the reverse bracket 208. The reverse bracket 208 is conventionally pivotally mounted to the chassis 14 at pivot point 230. Movement of the foot pedal 28 in the reverse direction rotates the shaft 58 in the counter-clockwise direction. This rotation causes the reverse cam 220 to rotate such that the cam follower 224 reaches the end of the cam slot 222 and then move with the reverse cam 220. Movement of the cam follower 224 causes the reverse bracket 208 to pivot via the cam link 226 against the biasing force of the spring 212. As the reverse bracket 208 pivots, the pulley 206 mounted on the reverse bracket 208 tensions the reverse-direction drive belt 201. However, one skilled in the art will understand that other means may be used to control the tension in the reverse-direction drive belt 201 without departing from the scope of the invention. As the reverse-direction drive belt 201 is tensioned, rotation of the engine output pulley 42 is transmitted to the variable speed pulley 50. Rotation of the variable speed pulley 50 is transmitted to the transaxle input pulley 44 by belt 51, thus driving the transaxle shaft 46 in the reverse direction.

[0030] As previously mentioned, the forward direction control cam 120 is also operatively mounted on the shaft 58. The forward direction control cam 120 likewise has a cam slot 122 for receiving a cam follower 124. The cam follower 124 is attached to a forward direction control link 126. The forward direction control link 126 extends rearwardly toward the transaxle 20 and is operatively connected to the bracket 108. The bracket 108 is conventionally pivotally mounted to the chassis 14 at pivot point 130. Movement of the foot pedal 28 in the forward direction rotates the shaft 58 in the clockwise direction. This rotation of the shaft 58 causes the forward cam 120 to rotate such that the cam follower 124 reaches the end of the cam slot 122 and then moves with the forward cam 120. Movement of the cam follower 124 causes the bracket 108 to pivot via the forward direction control link 126 against the biasing force of the spring 112. As the bracket 108 pivots, the pulley 106 tensions the forward-direction drive belt 101. However, one skilled in the art will understand that other means may be used to control the tension in the forward-direction drive belt 101 without departing from the scope of the invention. As the forward-direction drive belt 101 is tensioned, rotation of the engine output pulley 42 is transmitted to the transaxle input pulley 44 via the variable speed pulley 50, thus driving the transaxle shaft 46 in the forward direction. Pressing down further on the foot pedal 28 in the forward direction changes the belt pitch diameters between belts 101, 51 and therefore a greater rotational speed is transmitted to the transaxle input pulley 44. Pressing down further on the foot pedal 28 in the reverse direction changes the belt pitch for belt 201 at pulley 203, but not at belt 51. Accordingly, this arrangement provides the ability for the operator to vary the speed of the vehicle 10 in both the forward and reverse direction by selecting the amount of movement of the foot pedal 28 in the forward or reverse directions.

[0031] Cams 120 and 220 and cam slots 122 and 222 are particularly designed to complement each other and to coordinate the engagement of the forward and rear belt drive systems 100, 200 with the foot pedal 28. Specifically, the profiles of the cam slots 122, 222 are designed such that only one of the forward and reverse drive systems 100, 200 can cause the variable speed pulley 50 to rotate at a time. When the foot pedal 28 rotates in the forward or clockwise direction, the cam follower 224 slides in the slot 222 in the reverse cam 220 such that the reverse belt drive system 200 stays in its neutral condition. Likewise, when the foot pedal 28 rotates in the reverse or counter-clockwise direction, the cam follower 124 slides in the slot 122 in the forward cam 120 such that the forward belt drive system 100 stays in its neutral condition. Therefore, the two systems 100, 200 do not compete and attempt to rotate the variable speed pulley 50 in opposite directions at the same time. The cams 120 and 220 and cam slots 122 and 222 are desirably designed such that there is a suitable dwell or delay when shifting from the forward to the reverse direction and vice versa. [0032] Since the rear transmission belt 51 is designed to travel in either direction, the tight or tension side of the belt 51 flips when changing directions. In the embodiment illustrated in FIGS. 2-4, two fixed idler pulleys 60, 62 and an idler pulley 64 mounted on an idler arm 66 are supplied to account for the tension side flipping. The two fixed idler pulleys 60, 62 are desirably positioned behind the transaxle input pulley 44 to provide for suitable wrapping of the rear transmission drive belt 51 around the transaxle input pulley 44. Referring to FIG. 3, when the rear transmission drive belt 51 is moving in the forward driving direction, the top side is the tight side. In this case, the portion of the rear transmission drive belt 51 that wraps around top side of the transaxle input pulley 44 is the primary contributor to power transfer. When the rear transmission drive belt 51 is in reverse driving direction, the bottom side is the tight side. In this case, the portion of the rear transmission drive belt 51 that wraps around bottom side of the transaxle input pulley 44 is the primary contributor to power transfer. A tensioning spring 68 mounted between the chassis 14 and idler arm 66 provides a suitable and generally constant tension in the rear transmission drive belt 51. Desirably, there are no pulleys located directly between the transaxle input pulley 44 and the variable speed pulley 50 in either direction. As one skilled in the art would understand, it is desirable that that there not be an idler pulley between the tight side of input and output pulleys in order to prolong belt life. The illustrated embodiment is configured so that this does not occur the vehicle 10 is driven in either direction.

[0033] Turning now to FIG. 5, the variable speed pulley 50 is supported on a shaft 70 for rotation about its axis. The shaft 70 is supported by bearings 72 for rotation relative to the chassis 14 of the vehicle 10. The variable speed pulley 50 includes an outer first sheave 71 fixed to the shaft 70 and a slidable inner pulley 68 configured to both rotate and slide relative the shaft 70. The slidable pulley 68 includes a second sheave 72 and a third sheave 73. The second sheave 72 is a desirably a mirror image of the third sheave 73 and both pulley halves are fixed to each other to form the slidable pulley 68. The variable speed pulley 50 also includes an inner fourth sheave 74 fixed to the shaft 70, an inner fifth sheave 75 configured to rotate and slide on the shaft 70, and an outer sixth sheave 76 fixed to the shaft. The first and second sheaves 71 and 72, together, make up the transmission pulley 53 and form variable width pulley groove therebetween that receives the transmission drive belt 51. The third and fourth sheaves 73 and 74, together, make up the forward drive pulley 103 and form a variable width pulley groove therebetween that receives the forward-direction drive belt 101. The fifth and sixth sheaves 75 and 76, together, make up the reverse drive pulley 203 and form a variable width pulley groove therebetween that receives the reverse-direction drive belt 201. The sheaves 71-76 have a belt engagement surface or inner surface as is known in the art. Sheaves 72, 73 and 75 are movable axially to form variable diameter pulleys 5. Axial movement of the slidable pulley 68 comprising sheaves 72 and 73 changes the effective drive ratio between the forward-direction drive belt 101 and the transmission belt 51, and, as a result, the forward speed of the vehicle 10. Axial movement of the slidable fifth sheave 75 changes the effective drive ratio between the reverse direction drive belt 201 and the transmission belt 51, and, as a result, the reverse speed of the vehicle 10. As can be seen, however, axial movement of sheave 75 only affects the belt-receiving groove in the reverse drive pulley 203 and does not affect the transmission pulley 51. Accordingly, the reverse speed is limited to a slower speed, desirably approximately one-half of the forward speed. However, one skilled in the art will understand that pulley diameters may be selected to obtain different forward/reverse speed combinations.

[0034] The first, fourth, and sixth sheaves 71 , 74, 76 are fixed to the shaft 70 and configured to rotate therewith. The sheaves 71, 74, 76 may be made from sheet metal which is stamped and formed to the generally circular configuration shown in cross-section in FIG. 5 with an axially extending portion which is welded or otherwise secured to the shaft 70. The second and third sheaves 72, 73 are fixed to each such that their belt engagement surfaces face away from each other and are mounted onto a cylindrical sleeve 80. The sheaves 72, 73 may be made from sheet metal which is stamped and formed to the generally circular configuration shown in cross-section in FIG. 5 with an axially extending portion which is welded or otherwise secured to the sleeve 80. The sleeve 80 is slidable axially on the shaft 70 to enable movement of the second and third sheaves 72, 73 in opposite directions between the axially fixed first sheave 71 and the axially fixed fourth sheave 74. The sleeve 80 is also rotatable on the shaft 70. A first end 81 of the sleeve 80 is nestable within first sheave 71 as viewed in FIG. 6 A and a second end 82 of the sleeve 80 is nestable within the fourth sheave 74, as viewed in FIG. 6B.

[0035] The fifth sheave 75 is mounted on a cylindrical bearing 84. The fifth sheave 75 may be made from sheet metal which is stamped and formed to the generally circular configuration shown in cross-section in FIG. 5 with an axially extending portion which is welded or otherwise secured to the bearing 84. The bearing 84 is slidable axially on the shaft 70 to enable movement of the fifth sheave 75 in opposite directions between the axially fixed fourth sheave 74 and the axially fixed sixth sheave 76. The bearing 84 is also rotatable on the shaft 70. A first end 86 of the bearing 84 is nestable within sixth sheave 76 as viewed in FIG. 7A. [0036] A compression spring 88 is located between fixed fourth sheave 74 and slidable fifth sheave 75. The spring 88 places a compressive force on the reverse drive pulley 203 such that the pulley 204 biases the reverse-direction drive belt 201 to a radially outward position in the groove and into a low speed or disengaged condition. In the illustrated embodiment, a washer 90 is placed between the spring 88 and one of the adjacent sheaves 74, 75. Desirably, the washer 90 is placed between the fourth sheave 74 and the spring 88. The washer 90 is used to reduce rotational wind-up of the compression spring 88. The end of the compression spring 88 tends to dig into the material that it is resting against and anchor into place. When either of the adjacent sheaves 74, 75 are rotated, tension in the opposite direction of rotation builds up in the spring 88. With the washer 90 positioned between one sheave 74 or 75 and the spring 88, the spring 88 digs into the washer 90 and the washer 90 and spring 88 are then able slide freely with respect to the sheaves 74, 75. [0037] The bearing 84 is pressed into the fifth sheave 75 and contains a radially extending shoulder 92 on the top side thereof. The shoulder 92 prevents the fifth sheave 75 from sliding off of the bearing 84 when the reverse-direction drive belt 201 presses on the fifth sheave 75 causing the bearing 84 to slide along the shaft 70 against the biasing force of the spring 88 as the reverse belt drive system 200 is engaged. Desirably, the bearing 84 is a powdered metal bearing. [0038] Upon startup of the belt drive control system 21, the variable speed pulley 50 is in the neutral condition shown in FIG. 5. The slidable pulley 68 comprising sheaves 72 and 73 is in a position shifted axially closest to the fourth sheave 74 and farthest from the first sheave 71. The fifth sheave 75 is in a position shifted axially closest to the sixth sheave 76. The forward-direction and reverse- direction drive belts 101 and 201 are slacked and in disengaged positions with respect to the forward drive pulley 103 and reverse drive pulley 203, respectively. [0039] FIG. 6A shows a high torque, low forward speed condition where the forward belt drive system 100 has placed a small tension in the forward-direction drive belt 101. The forward-direction drive belt 101 is engaged but in a radially outward position in the groove formed in the forward drive pulley 103 in the variable speed pulley 50. The transmission drive belt 51 is in a radially inward position in the transmission pulley 53 in the variable speed pulley 50. The reverse-direction drive belt 201 is disengaged.

[0040] Upon movement of the bracket 108 to place a greater tension in the forward-direction drive belt 101, the sliding pulley 68 moves axially in a direction away from the fourth sheave 74 and toward the first sheave 71 (as viewed in FIG. 6B). Such movement results in a change in the speed ratio between the forward- direction drive belt 101 and the transmission belt 51. Specifically, the forward- direction drive belt 101 moves from a radially outer position in the forward pulley 104 to a radially inner position. The transmission belt 51 moves from a radially inner position in the transmission pulley 53 to a radially outer position. The speed ratio between the forward-direction drive belt 101 and the transmission belt 51 is decreased from the low speed condition and the driven transmission belt 51 moves faster for each degree of movement of the forward-direction drive belt 101. Accordingly, the speed of the vehicle 10 over the ground surface increases. In this condition, the variable speed pulley 50 is in a low torque, high speed condition. [0041] FIG. 7 A shows a high torque, low reverse speed condition where the reverse belt drive system 200 has placed a small tension in the reverse-direction drive belt 201. The reverse-direction drive belt 201 is engaged but in a radially outward position in the groove formed in the reverse drive pulley 203 in the variable speed pulley 50. The transmission drive belt 51 is in a radially inward position in the transmission pulley 53 in the variable speed pulley 50. The forward-direction drive belt 101 is disengaged.

[0042] Upon movement of the bracket 208 to place a greater tension in the reverse-direction drive belt 201, the fifth sheave 75 moves axially in a direction away from the sixth sheave 76 and toward the fourth sheave 74 (as viewed in FIG. 7B) against the biasing force of compression spring 88. Such movement results in a change in the speed ratio between the reverse-direction drive belt 201 and the transmission belt 51. Specifically, the reverse-direction drive belt 201 moves from a radially outer position in the reverse pulley 204 to a radially inner position. However, the transmission belt 51 remains in its radially inner position in the transmission pulley 53. The speed ratio between the reverse-direction drive belt 201 and the transmission belt 51 is decreased from the low speed condition, and the driven transmission belt 51 moves faster for each degree of movement of the reverse- direction drive belt 201. Accordingly, the speed of the vehicle 10 over the ground surface increases. In this condition, the variable speed pulley 50 is in a low torque, high speed condition. But the speed increase is not as great as that in the forward direction because the reverse belt drive system 200 does not affect the transmission pulley 53.

[0043] FIGS. 8 and 9 illustrate an alternate embodiment for tensioning the transmission belt 51. Instead of using idler pulleys as described above to tension the transmission belt, a compression spring 98 is used similar to the compression spring 88 used with the reverse drive pulley 203 is used. This would eliminate the need for the idler pulleys. One skilled in the art will understand that yet other means may be used to control the tension in the belts using sound engineering judgment. - [0044] While this invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, combinations, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of this invention, as set forth above are intended to be illustrative only, and not in a limiting sense. Various changes can be made without departing from the spirit and scope of this invention.