阅读说明：本技术 带有动态带张紧机构的跑步机 (Treadmill with dynamic belt tensioning mechanism ) 是由 杰弗里·A·拜尔 史黛西·E·斯塔姆 杰伊·T·沃罗贝茨 布莱恩·R·布拉泽斯 安德鲁·詹姆 于 2018-05-31 设计创作，主要内容包括：本申请涉及带有动态带张紧机构的跑步机。一种用于跑步机的动态带张紧装置,包括基座,该基座具有第一端和与第一端间隔开的第二端。脚踏平台由基座可移动地支撑,以便在跑步机运行期间允许平台竖直移动。传动带具有固定周长并且位于平台的顶部部分上方。驱动辊枢转地安装在基座的第一端附近,并与传动带接合。张紧辊枢转地安装到基座,并且能够响应平台的竖直移动而进行一定范围的移动,以向传动带提供基本恒定的张力。(The present application relates to treadmills with dynamic belt tensioning mechanisms. A dynamic belt tensioner for a treadmill includes a base having a first end and a second end spaced apart from the first end. The footrest platform is movably supported by the base to allow the platform to move vertically during operation of the treadmill. The belt has a fixed circumference and is positioned over a top portion of the platform. A drive roller is pivotally mounted adjacent the first end of the base and engages the drive belt. The tension roller is pivotally mounted to the base and is capable of a range of movement in response to vertical movement of the platform to provide a substantially constant tension to the drive belt.)

1. A treadmill having a dynamic belt tensioning mechanism, the treadmill comprising:

a support structure;

a platform movably coupled to the support structure;

a drive roller rotatably coupled to the support structure;

a tension roller rotatably coupled to the support structure;

a belt extending over the drive roller, the tension roller, and the platform; and

a bell crank pivotally coupled to the support structure, wherein pivoting of the bell crank translates into movement of the tension roller.

2. The treadmill of claim 1, wherein the bell crank comprises:

a pivot point coupled to the support structure,

a first connection point coupled to the tension roller, an

A second connection point coupled to the platform.

3. The treadmill of claim 1, further comprising an idler roller rotatably coupled to the support structure, wherein the belt further extends over the idler roller.

4. The treadmill of claim 1, wherein the bell crank pivots in response to movement of the platform.

5. The treadmill of claim 1, wherein the bell crank is coupled to the tension roller by a linkage.

6. The treadmill of claim 1, wherein the platform and the tension roller displace in different directions as the platform moves.

7. The treadmill of claim 1, wherein the bell crank is coupled to the platform by a linkage.

8. The treadmill of claim 1, wherein the tension roller is slidably coupled to the support structure.

9. The treadmill of claim 1, wherein the support structure comprises a frame extending in a direction of movement of the platform, and wherein the bell crank is pivotally coupled to the frame.

10. The treadmill of claim 1, wherein the bell crank comprises a first bell crank, wherein the treadmill further comprises a second bell crank pivotally coupled to the support structure, and wherein the first bell crank and the second bell crank are positioned adjacent opposite sides of the support structure.

11. The treadmill of claim 1, wherein the bell crank pivots during movement of the platform to displace the tension roller to maintain a substantially constant tension on the belt.

12. A method of dynamically tensioning a belt on a treadmill, the method comprising:

driving the belt on a treadmill platform during which the treadmill platform displaces in a first direction;

rotatably pivoting a bell crank when the treadmill platform is displaced in the first direction; and

transmitting a force from the rotatably pivoted bell crank to a tension roller, the force comprising a second direction different from the first direction.

13. The method of claim 12, wherein the tension roller traverses along a sliding connection coupled to a treadmill support structure in response to the force.

14. The method of claim 12, wherein pivoting the bell crank comprises:

pivoting a pivot point of the bell crank coupled to the treadmill support structure,

pivoting a first connection point of the bell crank coupled to the tension roller, an

Pivoting a second connection point of the bell crank coupled to the treadmill platform.

15. A belt tensioning mechanism for a treadmill, comprising:

a bell crank rotatably coupled to the pivot pin and including a first pivot connection and a second pivot connection;

a platform link pivotally coupled to the bell crank at the first pivot connection to apply a first force to the bell crank in a first direction; and

a tension roller link pivotally coupled to the bell crank at the second pivot connection to receive a second force from the bell crank in a second direction and caused by the first force applied to the bell crank.

16. A belt tensioning mechanism as in claim 15, wherein the bell crank comprises a first bell crank, wherein the belt tensioning mechanism further comprises a second bell crank.

17. A belt tensioning mechanism as claimed in claim 16, wherein the first and second bell cranks are mounted on a support structure such that they pivot in unison.

18. The belt tensioning mechanism of claim 15, further comprising a sliding connection coupled to the tension roller link.

19. A strap tensioning mechanism according to claim 18, wherein the sliding connection comprises a female sliding groove and a male sliding projection.

20. The belt tensioning mechanism of claim 15, further comprising a load cell sensor coupled between the tension roller link and the bell crank.

Technical Field

The present disclosure describes a dynamic belt tensioning mechanism for use with a treadmill.

Background

The treadmill has an endless belt powered by a drive roller. The belt is the surface on which the user engages in activities. The annular band enables a user to engage in activities within a relatively confined space.

Summary of The Invention

This summary is intended to introduce a selection of concepts in a simplified form that are further described below in the detailed description of the disclosure. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation as an aid in determining the scope of the claimed subject matter.

Briefly, and at a high level, this disclosure describes, among other things, dynamic belt tensioning devices/mechanisms for treadmills and methods of using the same. In one aspect, a dynamic belt tensioner comprises: a base having a first end and a second end spaced apart from the first end; a vertically movable foot platform; a drive belt having a fixed circumference; a drive roller mounted to the base, the drive roller engaging the drive belt; and a tension roller rotatably mounted on the base and adapted to move between different ranges of positions such that the tension roller is capable of providing continuous tension of the drive belt as the vertical position of the platform changes. The apparatus may include a movable member that transmits force from the platform to the tension roller so as to maintain a substantially constant tension on the drive belt by the tension roller.

In one aspect of the present disclosure, a dynamic belt tensioning device for a treadmill is provided. The device includes: a base positionable on a solid surface (solid surface) and having a first end and a second end spaced apart from the first end; a footrest platform movably supported by the base to allow the platform to move vertically during operation of the treadmill; a drive belt having a fixed circumference and positioned above the top portion of the platform to provide a moving foot-engaging surface during treadmill operation; a drive roller rotatably mounted near the first end of the base, the drive roller engaging the drive belt; and a tension roller rotatably mounted to the base and capable of a range of movement in response to vertical movement of the platform to provide a substantially constant tension to the drive belt.

In another aspect of the present disclosure, a dynamic belt tensioning device for a treadmill is provided. The device includes: a base positionable on a solid surface and having a first end and a second end spaced from the first end and including a first vertically disposed support frame and a second vertically disposed support frame mounted on opposite sides of the base adjacent the second end; a footrest platform movably supported by the base to allow the platform to move vertically during operation of the treadmill; a drive belt having a fixed perimeter and positioned above the top portion of the platform to provide a moving foot-engaging surface during treadmill operation; a drive roller rotatably mounted near the first end of the base, the drive roller engaging the drive belt; and a tension roller having a first end rotatably and slidably mounted to the first support frame and a second end rotatably and slidably mounted to the second support frame. The tension roller is capable of a range of movement in response to vertical movement of the platform to provide a substantially constant tension to the drive belt.

In another aspect of the present disclosure, a method of tensioning a belt on a treadmill is provided that includes a base having a platform mounted thereon such that the platform is capable of vertical movement. The method includes driving the belt, engaging a tension roller with the belt, and moving the tension roller to provide a substantially constant tension to the belt in response to vertical movement of the platform.

Brief Description of Drawings

Aspects of the present disclosure are described in detail with reference to the drawings, wherein like numerals refer to like elements, and wherein:

FIG. 1 depicts a top perspective view of a treadmill with a dynamic belt tensioning mechanism, in accordance with aspects hereof;

FIG. 2 depicts a side view of the treadmill of FIG. 1 in accordance with aspects hereof;

FIG. 3 depicts a top perspective view of the area indicated by numeral 3 in FIG. 1, illustrating one example of a dynamic belt tensioning mechanism in accordance with aspects hereof;

FIG. 4 depicts a side view of the area indicated by numeral 4 in FIG. 2, showing the treadmill platform in a raised position relative to the treadmill base in accordance with aspects hereof;

FIG. 5 depicts a side view similar to FIG. 4, but showing the treadmill platform in a lowered position relative to the treadmill base in accordance with aspects hereof;

FIG. 6 depicts a side diagrammatic elevation view of the dynamic belt tensioning mechanism of FIG. 1, with arrows indicating the displacement and rotational direction of various components, in accordance with aspects hereof;

FIG. 7 depicts a block diagram of an example process for dynamically tensioning a treadmill belt, in accordance with aspects hereof; and

fig. 8 depicts a block diagram of another example process for dynamically tensioning a treadmill belt in accordance with aspects hereof.

Detailed description of the invention

The subject matter of the present disclosure is described with specificity herein to meet statutory requirements. However, this description is not intended to limit the scope of the present disclosure. Rather, the claimed subject matter might be presented in other ways, to include different steps, combinations of steps, features, and/or combinations of features, similar to those described in this disclosure, and in conjunction with other present or future technologies. Moreover, although the terms "step" and/or "block" may be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps or blocks unless and except when the order is explicitly described and required.

1-7 depict example devices and mechanisms for dynamically tensioning a belt of a treadmill, and methods of using the same. Referring initially to fig. 1, in accordance with aspects herein, a treadmill 10 having a dynamic belt tensioning mechanism 12 is depicted. Treadmill 10 has a base 14 for supporting treadmill 10 on a suitable support surface. Treadmill 10 includes a platform 16 supported above base 14 and vertically movable to a plurality of different vertical positions in response to user interaction on an upper surface 18 of treadmill 10. More specifically, any suitable structure may be used to support the platform 16 above the base 14 to allow the platform 16 to move in an upward and downward manner relative to the base 14 (e.g., while a user is running on the platform 16). Thus, the upward and downward movement of the platform 16 accommodates the downward force exerted by the user on the upper surface 18 when performing, for example, running or walking exercises. For example, during a running exercise, when a user's foot strikes the platform 16, the platform 16 may be displaced downward (e.g., toward the base 14). In addition, when the user's foot is removed during the running motion, the platform 16 may be resiliently moved upward in preparation for another foot of the user to strike the upper surface 18. A suitable support structure for supporting the platform 16 for vertical movement above the base 14 is a scissor frame 20 as depicted in fig. 1. The scissor frame 20 includes a first scissor arm 22, the first scissor arm 22 being pivotally mounted to a second scissor arm 24 at a pivot point 26. The arms 22 and 24 are suitably mounted between the platform 16 and the base 14 to allow the platform 16 to be positioned at different heights above the base 14. The scissor frame 20 is but one exemplary embodiment that allows the platform 16 to move vertically relative to the base 14. Other structures and frames, such as, for example, linear bearings and/or rails, may provide the same type of vertical motion to the platform 16.

Referring now to fig. 1-2, the treadmill 10 also includes an endless/belt 28 that provides a moving surface for a user to engage during use of the treadmill 10. More specifically, the belt 28 has a fixed circumference and moves over the upper surface 18 of the platform 16. Thus, when the user is walking or running, for example, the belt 28 moves under the user's foot to allow walking or running at a single location. In addition to moving on the upper surface 18, the belt 28 also moves under the floor 30 of the base 14. More specifically, referring to fig. 1-2, the floor 30 is supported above the ground surface by a plurality of generally trapezoidal legs 32, the legs 32 also being part of the base 14. A leg 32 is positioned along each edge 34 of the plate 30. Only one of the edges 34 is depicted in fig. 1-2, the other being obscured. In addition, the legs 32 along each edge 34 are connected by support ribs 36 extending downwardly from a lower surface 38 of the bottom plate 30. The provision of support ribs 36 along each side of the base plate 30 defines a cavity 40 through which the strap 28 passes adjacent the lower surface 38 of the base plate 30. In this manner, the belt 28 is able to travel in a continuous loop along the upper surface 18 of the platform 16 and along the lower surface 38 of the floor 30 of the base 14.

Still referring to fig. 1-2, a belt drive mechanism 42 is depicted. The belt drive mechanism 42 is used to provide an endless motion to the belt 28 so that the user has a continuous running/walking surface as the user moves over the upper surface 44 of the belt 28. The belt drive mechanism 42 may be used to adjust the speed at which the user runs or walks. Any suitable control system may be used to adjust the speed of the belt drive mechanism 42 and, thus, the speed of the belt 28 shown in fig. 1-2.

The belt drive mechanism 42 includes a drive roller 46, the drive roller 46 being rotatably mounted to the base 14 by a pair of mounting brackets 48 located on opposite sides of the base 14. Only one of the mounting brackets 48 is depicted in fig. 1-2, the other being obscured. Mounting brackets 48 extend upwardly from the plate 30 of the base 14 and each provide a pivot bearing 50 for receiving a shaft 52 of the drive roller 46. The provision of a shaft 52 rotatably mounted in the pivot bearing 50 allows for the rotational movement of the drive roller 46. The drive roller 46 is coupled to any suitable power source to drive the rotational movement of the drive roller 46, thereby driving the belt 28. The power source is not depicted in the figures, but may be any suitable source, such as, for example, an electric or hydraulic motor drivably coupled to drive roller 46 by, for example, a belt or chain system. The power source may also act directly on the shaft 52 to effect rotational movement.

Still referring to fig. 1-2, treadmill 10 further includes a transition frame 54 for facilitating a smooth transition of belt 28 between base 14 and platform 16, particularly when platform 16 is displaced between a plurality of different vertical positions relative to base 14 during operation of treadmill 10. The transition frame 54 includes a support structure 56 fixedly mounted to the base 14 adjacent the belt drive mechanism 42. The support structure extends along the entire rear edge 58 of the base 14. The transition frame 54 also includes a bridge 60 for supporting the belt 28 as the belt 28 transitions from the drive roller 46 to the deck upper surface 18. The bridge 60 is slidably and pivotally mounted to the support structure 56 by a pin and slot arrangement 62 adjacent a rear end 64 of the bridge 60. The bridge 60 is pivotally mounted to the platform 16 by a pivot arrangement 66 adjacent a forward end 68 of the bridge 60. Thus, as the platform 16 moves relative to the base 14 during operation, the bridge 60 pivots and slides relative to the base 14 via the pin and slot arrangement 62. Furthermore, during vertical movement of the platform 16, the bridge 60 is pivoted relative to the platform 16 by means of the pivot arrangement 66. In this manner, the bridge 60 changes its angle relative to the platform 16 as the platform 16 is vertically displaced and thereby provides a smooth transition support surface for the belt 28.

Still referring to fig. 1-2, the platform 16 further includes an operator support frame 70, the operator support frame 70 including a pair of vertically extending posts 72, the posts 72 being fixedly mounted to opposite sides of the base 14 adjacent lower ends 74 of the posts 72. The operator support frame also includes a console 76 mounted between the upper ends 78 of the columns 72 and adjacent the upper ends 78 of the columns 72. A pair of support arms 80 extend rearwardly from opposite sides of the console 76 to provide lateral support and stability to a user engaged with the platform 16. If desired, the console 76 may include various sensors and displays to monitor or inform the user.

Referring to fig. 3-6, the exemplary dynamic belt tensioning mechanism 12 illustrated in fig. 1-2 is described in detail and the exemplary dynamic belt tensioning mechanism 12 is disposed near the front end 82 of the treadmill 10. The tensioning mechanism 12 provides an increased and/or substantially constant tension to the belt 28 as the platform 16 moves up and down relative to the base 14. More specifically, the band 28 has a fixed circumference. The spatial relationship between the platform 16 and the base 14 dynamically changes as the platform 16 moves up and down. Without the belt tensioning mechanism 12, there may be slack in the belt 28 as the platform 16 moves downward toward the base 14. This slack can result in possible disengagement of the belt 28 from the drive roller 46. In addition, the slack may result in an unstable running surface on the upper surface 44 of the belt 28. Thus, with the tensioning mechanism 12, the belt tensioning mechanism 12 provides a substantially constant tension in the belt 28 regardless of the relative vertical position of the platform 16 above the base 14.

The dynamic belt tensioning mechanism 12 includes a pair of support frames 84 mounted near the front end 82 of the treadmill 10. The support frame 84 is mounted on the upper surface 85 of the plate 30 of the base 14. As shown in fig. 1, support frames 84 are located on opposite sides of the plate 30 and extend upwardly from the upper surface 85. Each support frame 84 includes a bell crank 86 pivotally mounted thereto by a pivot pin 88. Each bell crank 86 includes a rear pivot connection 90, with rear pivot connection 90 being connected to a first end 92 of a platform link 94 by a pivot/ball joint 96. The second end 98 of the platform link 94 is pivotally connected to the platform 16 at pivot point 100 by pivot/ball joint 102. The pivot/ball joints 96 and 102 may allow rotation in all directions to minimize friction and binding. Pivot connection 90 is located at a rear end 104 of bell crank 86. The link 94 has a length adjustment turnbuckle 106 that can be used to adjust the length of the link 94.

The front end 108 of each bell crank 86 has a front pivotal connection 110 connected to a first end 112 of a respective tension roller link 114 by a pivot pin 116. A second end 118 of each tension roller link 114 is pivotally connected to a respective tension roller mount 120 by pivot pin 116. Tension roller mounts 120 are located on opposite sides of base 14 and serve to rotatably mount tension rollers 122 via bearing assemblies 124 associated with each mount 120. The arrangement of mount 120 and bearing assembly 124 allows tension roller 122 to rotate freely. The tension roller 122 has a cylindrical surface 126 that engages a lower surface 128 of the belt 28. It is this engagement between the surface 126 and the belt surface 128 that provides tension on the belt 28 as the platform 16 moves up and down relative to the base 14. Each tension roller link 114 has a load cell sensor 130, which load cell sensor 130 can be used to measure dynamic belt tension.

Each tension roller mount 120 is slidably connected to a front end 132 of a respective support frame 84 by a sliding connection 134. Each sliding connection 134 includes a female sliding channel member 136 as part of the tension roller mount 120 or mounted to the tension roller mount 120 and a male sliding protrusion member 138 as part of the front end 132 of the support frame 84 or mounted to the front end 132 of the support frame 84. With this configuration, the mount 120, and thus the tension roller 122, may have sliding linear motion capability relative to the front end 132 of the support frame 84. It is this sliding movement that assists in the dynamic tensioning of the belt 28.

In addition to the tension roller 122, an idler roller 140 is also rotatably mounted between the support frames 84 by a bearing arrangement 142. Idler roller 140 also has a cylindrical surface 144 that engages belt 28 below belt surface 128. Idler roller 140 remains stationary but is free to rotate during operation of tensioning mechanism 12. Idler rollers 140 are used to support belt 28 during operation and assist in the dynamic tensioning provided by linearly moving tension roller 122.

Referring to fig. 6, during operation of the treadmill 10, the spatial position of the platform 16 relative to the base 14 dynamically changes in a generally vertical direction (e.g., moves toward and away from the base 14). As platform 16 moves downward, a downward force is exerted on rear end 104 of bell crank 86. This downward force causes bell crank 86 to rotate in a clockwise manner via connecting rod 94. By the provision of tension link 114 and sliding connector 134, clockwise rotation of bell crank 86 results in substantially forward and upward linear movement of mount 120 and therefore tension roller 122. Clockwise rotation of bell crank 86 causes a generally forward and upward force to be applied to tension roller 122 via link 114. The female slide channel member 136 (shown in fig. 5) slides along the male projection 138 to allow linear movement of the tension roller 122. The downward movement of the platform 16 results in less space between the platform 16 and the base 14 so that the slack in the fixed perimeter band 28 will increase unless accounted for by the dynamic tensioning mechanism 12. The generally forward and upward linear movement of the tension roller 122 reduces slack and helps maintain a substantially constant tension on the belt 28.

Further, as platform 16 moves upward, bell crank 86 is rotated in a counterclockwise manner by link 94. This counterclockwise rotation of bell crank 86 results in a generally rearward and downward linear movement of tension roller 122 through the arrangement of link 114, mount 120 and sliding connection 134. Referring back to fig. 4, such upward movement of the platform 16 is depicted. The upward movement of the platform 16 results in a greater spatial relationship between the platform 16 and the base 14. Thus, the slack in the fixed perimeter band 28 may be reduced, and thus may be less pronounced. The linear movement of the tension roller 122 dynamically adjusts the tension in response to movement of the platform 16. As the platform 16 moves up and down relative to the base 14, the tension roller 122 also dynamically slides along the sliding connection 134 to provide a substantially constant or rather continuous tension on the belt 28.

Referring to fig. 7, according to aspects herein, a block diagram of an example method 700 for dynamically tensioning a treadmill belt is provided. At block 146, a treadmill is provided having a base (e.g., base 14 shown in fig. 1) with a platform (e.g., platform 16 shown in fig. 1) mounted thereon to provide vertical movement. At block 148, a belt (such as belt 28 shown in FIG. 1) is powered. At block 150, a tension roller (e.g., tension roller 122) is engaged with the drive belt. At block 152, the tension roller moves in response to the vertical movement of the platform to provide continuous contact tension to the drive belt.

Referring to fig. 8, a block diagram of another example process 800 for dynamically tensioning a treadmill belt is provided, in accordance with aspects herein. At block 810, a belt (e.g., belt 28 shown in FIG. 1) is driven. At block 820, a tension roller (such as tension roller 122 shown in fig. 6) is engaged with the belt. At block 830, the tension roller is moved in response to vertical movement of the treadmill deck (e.g., deck 16 shown in fig. 1), such as by using an assembly of components as shown in fig. 5 and 6, to provide a substantially constant tension to the belt.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is covered by and within the scope of the claims.

Although specific elements and steps are discussed in conjunction with each other, it should be understood that any element and/or step provided herein is contemplated as being combinable with any other element and/or step, whether explicitly stated or not, while remaining within the scope provided herein. Since many possible embodiments may be made of the disclosure without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The present application also relates to the following:

1) a dynamic belt tensioning device for a treadmill, the device comprising: a base positionable on a solid surface and having a first end and a second end spaced apart from the first end; a foot platform movably supported by the base to allow vertical movement of the foot platform during operation of the treadmill; a drive belt having a fixed circumference and positioned across a top portion of the tread platform to provide a moving foot-engaging surface during operation of the treadmill; a drive roller rotatably mounted near the first end of the base, the drive roller engaging the drive belt; and a tension roller rotatably mounted to the base and movable through a range of movement in response to vertical movement of the foot platform to provide a substantially constant tension to the drive belt.

2) The device of 1), further comprising a bell crank pivotally mounted near the second end of the base, wherein the bell crank has a pivot point mounted to the base and a first connection point connected to the tension roller and a second connection point connected to the tread platform, and wherein vertical movement of the tread platform causes movement of the tension roller to provide a substantially constant tension to the belt during operation of the treadmill.

3) The apparatus of 1), further comprising an idler roller rotatably mounted near the second end of the base, the idler roller engaging the drive belt.

4) The device of 2), wherein the first connection point of the bell crank is pivotally attached to the tension roller.

5) The device of 4), wherein the first connection point is attached to the tension roller by a link.

6) The apparatus of 2), wherein the second connection point of the bell crank is pivotally attached to the foot platform.

7) The apparatus of 6), wherein the second connection point is attached to the foot platform by a linkage.

8) The device of 2), wherein the tension roller is slidably mounted to the base to provide linear movement of the tension roller to impart a substantially constant tension to the drive belt.

9) The apparatus of 8), wherein the base includes a vertically disposed support frame, and wherein the support frame pivotally mounts the bell crank via the pivot point and slidably mounts the tension roller.

10) The apparatus of 9), wherein the base includes two vertically disposed support frames mounted on opposite sides of the base and two bell cranks pivotally mounted to the two vertically disposed support frames, respectively.

11) The device of 10), wherein a first end of the tension roller is rotatably mounted to a first one of the support frames and a second end of the tension roller is rotatably mounted to a second one of the support frames.

12) The device of 11), wherein the first end of the tension roller is connected to a first connection point of a first one of the bell cranks and the second end of the tension roller is connected to a first connection point of a second one of the bell cranks.

13) The apparatus of 12), further comprising an idler roller, wherein a first end of the idler roller is rotatably mounted to the first one of the support frames and a second end of the idler roller is rotatably mounted to the second one of the support frames.

14) The device of 2), wherein the bell crank converts a substantially vertical force exerted on the foot platform into a substantially horizontal force exerted on the tension roller.

15) A dynamic belt tensioning device for a treadmill, the device comprising: a base positionable on a solid surface and having a first end and a second end spaced apart from the first end and including a first vertically disposed support frame and a second vertically disposed support frame mounted on opposite sides of the base adjacent the second end of the base; a foot platform movably supported by the base to allow vertical movement of the foot platform during operation of the treadmill; a drive belt having a fixed circumference and positioned across a top portion of the tread platform to provide a moving foot-engaging surface during operation of the treadmill; a drive roller rotatably mounted near the first end of the base, the drive roller engaging the drive belt; and a tension roller having a first end rotatably and slidably mounted to the first vertically disposed support frame and a second end rotatably and slidably mounted to the second vertically disposed support frame, wherein the tension roller is capable of a range of movement in response to vertical movement of the foot platform to provide a substantially constant tension to the drive belt.

16) The apparatus of 15), further comprising a first bell crank pivotally mounted to the first vertically disposed support frame and a second bell crank pivotally mounted to the second vertically disposed support frame, wherein each bell crank has a pivot point mounted to its respective support frame and a first connection point connected to the tension roller and a second connection point connected to the tread platform, wherein vertical movement of the tread platform causes movement of the tension roller to provide substantially constant tension to the drive belt during operation of the treadmill.

17) The apparatus of 15), further comprising an idler roller, wherein a first end of the idler roller is rotatably mounted to the first vertically disposed support frame and a second end of the idler roller is rotatably mounted to the second vertically disposed support frame.

18) The device of 16), wherein the first connection point of each bell crank is pivotally attached to the tension roller, and wherein the second connection point of each bell crank is pivotally attached to the foot platform.

19) The device of 18), wherein the first connection point of each bell crank is attached to the tension roller by a link, and wherein the second connection point of each bell crank is attached to the foot platform by a link.

20) A method of tensioning a belt on a treadmill, the treadmill comprising a base with a platform mounted to the base such that the platform is vertically movable, the method comprising: driving the belt; engaging a tension roller with the belt; and moving the tension roller to provide a substantially constant tension to the belt in response to vertical movement of the platform.