GB2345864A

GB2345864A - Omni-directional treadmill

Info

Publication number: GB2345864A
Application number: GB0001334A
Authority: GB
Inventors: Andrew John Mitchell
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-01-20
Filing date: 2000-01-20
Publication date: 2000-07-26
Also published as: GB9901229D0; GB0001334D0

Abstract

An omni-directional treadmill arrangement for providing a continuously moveable surface, moveable in any direction within a defined area, comprises a set of longitudinal belts 12, each belt 12 being able to convey in a loop along its length in a first direction (up and down in fig 1), such that the set of belts 12 can also be moved together in a loop in a second direction not parallel to the first direction (left and right in fig 1). A drive means comprising two chains 40, 42 on a side of the set of belts 12 and a cog 18 per belt 12 can drive the belts 12. The cog 18 can be placed between the chains 40, 42, such that rotational movement of the cog 18 drives each belt 12 in the first direction, and linear movement of the cog 18 along the chains 40, 42 drives the set of belts 12 around the loop in the second direction (fig 4). Thus a single drive means can power the motion of the belts 12 in perpendicular directions. A set of gears, cogs and drive belts (fig 3) can convert the rotational cog 18 motion into belt 12 motion in the first direction. There may be more than one cog 18 per belt 12, and the chains 40, 42 may be on both sides of the belts 12. The chains 40, 42 may be a replaced by a single piece of material, eg a belt. In a second embodiment, the set of belts 12 are either hingedly connected to each other or are independently driveable, and only a single chain 40, 42 is used.

Description

OMNI-DIRECTIONAL TREADMILL The present invention relates to omni-directional treadmills, and in particular to means for driving belts on such treadmills.

More specifically, this invention relates to omni-directional treadmills of the general type disclosed in International Patent Publication WO 97/34663 (incorporated herein by reference)comprising a plurality of transverse belts each arranged to rotate in a first direction along their own length, and located adjacent to one another so as to provide a substantially continuous surface. The transverse belts are also confined to move in a loop in a second direction perpendicular to the first direction. A suitable combination of movement in the first direction and the second direction allows the surface defined by the transverse belts to move in any direction indefinitely.

A problem with such treadmills at present is that it is difficult to efficiently drive the transverse belts along their length. Essentially, there are at present two ways to drive the belts, as discussed in the above mentioned international patent publication. The first way to drive the belts is to provide each of the belts with its own driving motor. This driving mechanism is expensive, as a separate motor is required for each of the transverse belts, of which there will normally be ten or more. These motors also take up a lot of space and make the transverse belt assemblies higher in profile than they would ideally be, thus raising the treadmill surface relative to the ground. Furthermore, powering the motors is difficult since each motor must move with its associated belt about the loop in the second direction, necessitating the use of a brush system which leads to unreliability. Finally, it is necessary to ensure that all the belts travel at precisely the same speed, so either speed monitoring equipment is necessary or stepper motors must be provided, again increasing the cost.

An alternative way of driving the transverse belts is to provide one or more elongate drive cogs along the length of the active surface which drive the transverse belts. As the transverse belt assemblies move into position to form part of the active surface, cogs on the belts engage the elongate cog or cogs which then provide the necessary drive linkage between the motors and the transverse belts. However, a fundamental disadvantage of this driving mechanism is that means are required for engaging the teeth on the two sets of cogs, such as synchro-mesh, or a low power synchronizing driving mechanism is required on the transverse belts to bring them up to the same speed as the elongate cogs before they engage. This makes the transverse belts more complex and hence more expensive to manufacture, and also reduces the working life of the transverse belt units.

A mechanism is clearly required which allows all the transverse belts to be driven by the same driving mechanism while not requiring engagement and disengagement of cogs, thereby decreasing wear and friction.

According to a presently preferred embodiment of the present invention, there is provided a looped member drive mechanism for an omni-directional treadmill having a plurality of transverse belts, each said transverse belt being moveable in a first looped path along its length and being mounted on a carrier means which is moveable in a second looped path perpendicular to said first looped path, and each carrier means having at least one rotatable drive imparting member rigidly connected thereto such that linear movement of said drive imparting member effects movement of the carriers means about said second looped path and rotational movement of said drive imparting member effects movement of the transverse belt carried on said carrier means about said first looped path, said drive imparting member being operatively connected to first and second independently operable drive means, whereby said first and second drive means can be operated to imparts varying degrees of linear and rotational motion to said drive imparting member The terms looped member and belt, when used in this document, are intended to encompass any arrangement forming a loop, such as a metal chain or a single, looped piece of material. The term belt is used for the transverse belts simply because it makes the concept of the omni-directional treadmill easier to understand, as a belt is standard treadmill terminology for the surface providing looped member.

The present invention relates to an omni-directional treadmill comprising a plurality of transverse belt means each movable over a looped path, and each comprising a transverse belt rotatable along its length.

According to a presently preferred embodiment of the invention, there is provided a differential drive mechanism for an omni-directional treadmill. More specifically, means are provided for driving said transverse belt means in a looped path, and longitudinal motion means are provided which provide an engageable surface which moves in the direction of the looped path of the transverse belt means, at least over the portion of the path over which they provide an omni-directional surface. The relative velocity of the transverse belt means and the longitudinal motion means over at least the active portion of the path is mechanically transformed into rotational movement of a rotatable member on each of said transverse belt means. Further means are provided which transfer the rotational movement of the rotatable member into movement of the transverse belt on each of the transverse belt members along its length.

According to a first form of the invention, the transverse belt means are each driven around their loop. A driving looped member on each side of the treadmill is provided which runs substantially in the same direction that the transverse belt means are transported over the active part of their path. The active part of the path of each transverse belt means is the part over which it might support an independently moveable object, such as a person. Rotatable members such as cogs are mounted on the transverse belt means which are engageable with the independently driven looped member. Relative motion of the driving looped member and the transverse belt means as they are transported across the active part of their path, causes the rotatable member on each transverse belt means to rotate. This rotation effects, through appropriately gearing, rotation of the transverse belts along their length. Thus, longitudinal transportation of the transverse belts and transverse rotation of the transverse belts along their length can be achieved in any combination by appropriately selecting the velocity of the first driving means and the velocity of the driven looped member relative thereto.

According to a second form of the invention, the transverse belt means are engageable with two driving looped member means, but can move relative to each of the driving looped member means.

According to one specific embodiment of the invention of this type, two independently driven driving looped members are provided on each side of the treadmill, each of which runs substantially constantly spaced and in the same direction as the transverse belt means over the active part of the path of the transverse belt means. Rotatable members, such as cogs, mounted on the transverse belt means, extend between the two independently driven looped members, so as to engage both looped members. The rotatable members, through their engagement with the looped members, move along with the looped members at a rate substantially determined by the average of the velocities of the two looped members. Thus the two looped members can be used to longitudinally transport the transverse belt means. In addition, the difference in velocity of the two looped members will impart rotational motion to the rotatable members, which, through appropriate gearing, is translated into transverse drive of the transverse belts. The driving looped members accordingly act as the above mentioned longitudinal motion means. Thus, longitudinal transportation of the transverse belts and transverse rotation of the transverse belts along their length can be achieved in any combination by appropriately selecting the velocities of the two independently drivable looped members.

According to a third form of the invention, a worm-gear is provided over the length of the active portion of the path of the transverse belt means. Rotation of the worm-gear about its axis provides the effect of longitudinal motion of the engageable surface of the worm-gear along its length. Cog means on each of the transverse belt means with appropriately angled teeth, and with their axes close to perpendicular to that of the worm-gear and substantially parallel to the active surface of the treadmill engage the worm-gear as they move onto the active part of their path.

Relative motion of the transverse belt means and the longitudinal motion of the worm-gear acts to drive the transverse belts in a similar manner to the first embodiment.

This form is not a preferred form as it still suffers to an extent from the inherent friction and engagement problems of previously known mechanisms, the friction being due to the fact that the motion of the worm-gear is rotational rather than truly longitudinal, and the engagement problems being due to the fact that the worm-gear cannot follow the entirety of the path of the transverse belt means. The embodiment is primarily included to demonstrate that the effect of continuous longitudinal motion can conceivably be provided by means other than a looped member.

In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawing, in which: FIGURE 1 is a partial perspective side view of an omni-directional treadmill including a looped member drive system embodying the invention.

FIGURE 2 is a top view of two adjacent transverse belt assemblies of the treadmill of Figure I ; FIGURES 3A and 3B are enlarged views of the gearing mechanism for driving transverse belts on the transverse belt assemblies ; FIGURES 4A to 4E show how the gear system of the invention operates and show examples of different combinations of transverse and longitudinal motion of the transverse belts which can be achieved using the gear system of the first embodiment of the invention; FIGURES SA and 5B are side and end views respectively of the mechanism for driving the chains of the treadmill of the first embodiment of the invention.

Referring first to Figure 1, there is shown part of an omni-directional treadmill having a plurality of transverse belt assemblies 10 which are movable in a loop in a longitudinal direction.

For the sake of simplicity, only four transverse belt assemblies 10 are shown in Figure 1, but it is understood that a sufficient number oftransverse belt assemblies 10 should be provided to ensure that a substantially continuous flat surface can be provided by the treadmill. As can be seen more clearly in Figure 2, the transverse belt assemblies 10 are also arranged alternately offset from one another in the transverse direction, thereby ensuring that transverse belts 12 of transverse belt assemblies 10 substantially abut one another to provide a continuous surface.

According to this embodiment, each transverse belt assembly 10 is provided with rollers 32 which engage in rails 50,52 on each side of the treadmill so that the assemblies 10 are confined to move in the longitudinal direction in a looped path defined by the rails 50,52. There is furthermore provided at each side of the treadmill an inner 40 and an outer 42 drive chain, each chain extending about a looped path similar to that defined by the rails 50,52 and being engaged by cogs 18 carried on each of the transverse belt assemblies 10. As can be seen in Figure 2, a cog 18 is provided on each side of each transverse belt assembly 10, the two cogs 18 of each assembly 10 being associated with transversely aligned rollers 32.

Figure 3B shows a side view of one of the transverse belt assemblies with roller 32 engaging in rails 50 and 52. The rails can simply be flat, rigid strips of material or molded into the treadmill casing, such as for example molded plastic. Of course, other known railing systems could also be used. The rails define the path of the transverse belt assemblies. According to this embodiment, two sets of rails are provided, one inside the loop defined by the motion of the transverse belt assemblies and one outside the loop, so that the rollers are confined to only move along the loop defined, and are prevented from vertical movement when upside-down. Clearly the gap between the rails must be slightly greater than the diameter of the rollers so that the rollers can rotate.

The general construction of the transverse belt assemblies is similar to that disclosed in WO 97/34663 and will not be discussed in detail here, except for a gearing mechanism provided on at least one end of each of the transverse belt assemblies, as shown best in Figure 3A, to provide a mechanical linkage between one of the cogs 18 on the transverse belt assembly and its transverse belt 12. Figure 3A shows a corner of one of the transverse belt assembly 10 with its belt 12 extending around a roller 14 which in turn is held by a rigid frame 16. This frame would normally extend the length of the transverse belt 12 and hold another roller 14 at the far end, as shown best in Figure 2. It might also hold a set of intermediate rollers or a flat, low-friction board which provide additional support for the transverse belt 12. Such support mechanisms are well known in the treadmill art. The gearing mechanism converts the rotation of cog 18 about its axis into rotation of the roller 14 about its perpendicular axis. The mechanism shown uses gears 22, 24,26 and 28 and belt 30 to transmit the torque. Cog 24 drives cog 22 which is directly connected via a shaft to cog 26. Rotation of cog 26 causes cog 28 to rotate via belt or chain 24, which in turn causes rotation of the roller 14, to which it is connected. Clearly other gearing mechanisms could be used without departing from the invention. This gearing mechanism is simply given by way of example. Important considerations in deciding suitable gearing mechanisms are the radius of cogs-ideally the radius of the gears should be less than that of the roller 14 in order to keep the profile of the whole treadmill low. Furthermore, the mechanism needs to be kept compact so as not to interfere with the adjacent transverse belt assemby 10 (see Fig 2). As shown best in Figure 2 and Figure 3B, each corner of the transverse belt assembly 10 is supporte by a roller 32 connected by a shaft to the frame of the transverse belt assembly These rollers run on rails 50,52. A further cog 18 is provided on each transverse belt assembly.

This cog is located on the opposite end of the transverse belt assembly 10 and transversely aligned with the other geared cog 18, but is not itself mechanically connected to the transverse belt assembly. Cogs are not provided on the shafts with the other two rollers for reasons discussed below. Corresponding rollers/cogs 32,18 at each end are aligned along the long axis of the belt assembly. The cog 18 is at the distal end of the shaft 19, although in other similar embodiments, the roller 32 could be at the distal end of the shaft.

Driving chains 40a and 40b are corresponding chains aligned on either side of the treadmill, as are chains 42a and 42b. Chains 40a and 40b follow an inner loop. Chains 42a and 42b follow an outer loop, as shown best in Figure 1. The chains constituting each pair on each side of the treadmill are substantially coplanar in a vertical longitudinal plane. A constant spacing is maintained between the two chains around the loops. The chains travel about a path substantially similar to that defined by rails 50,52, although at appropriate radii to allow engagement with opposing edges of the cogs 18. Each drive chain 40, 42 extends between a pair of cogs 60,70, shown best in Figures 5A and B. The cogs 60,70 at each end of the treadmill are preferably coaxial and the cogs 60 are arranged to be movable independently of cogs 70. Cogs 60 are driven by a first motor 80 and cogs 70 are driven by a second motor 90. It is envisage that the two cogs 60 disposed on opposite sides at one end of the treadmill will be driven about a common shaft by one motor, and no motor will be provided for the counterpart to each driven cog at the other end of the treadmill supporting the same chain. Cogs 70 would likewise only be driven at one end of the treadmill. However, further motors, or even the same motors, could drive the cogs at each end to provide a more balanced force on the chains. The driving mechanisms for cogs 60 and 70 would ideally be at opposing ends of the treadmill to one another so that they do not interfere with one another. Each of the four chains on each side should ideally be driven so that the drive to the transverse belt assemblies is balanced, rather than relying on transmission of the drive from one side of the treadmill to the other through the transverse belt assemblies.

As the chains travel about their respective end cogs 60,70, the cogs 18 on each of the transverse belt assemblies must engage the opposite side of the drive chain to cog 60 and the same side of cog 70 without the teeth interfering with one another. Looking in more detail at Figure SB, this is achieved in this embodiment by use of a chain of double width compared to the width of the cogs 60,70. The cogs 60 and 70 engage one of the side by side chains, and the cogs 18 engage the other. Alternatively, the cogs 60 and 18 could be provided with low profile teeth so that chain 40 could instead be a single chain engaged from both sides. As can be seen from Figure 5B, the two chains in each set engage with the smaller and larger radius cogs in such a way that the chain in each pair which is not wrapped around a cog are coplanar in plane A. Over the length of the chains not held by the cogs around which they are wound, the non-supported chain of each side by side pair can be prevented from moving radially inward or outwardly respectively by rails, not shown.

The cogs 18 on each of the transverse belt assemblies engage in and are therefore driven by both chains 40 and 42. Accordingly, the relative speeds of the chains 40 and 42 directly control the linear and angular velocities of the cogs 18, as shown in Figure 4A, allowing each to be varied independently of the other. Since the linear velocity of each cog 18 controls the longitudinal movement of the each transverse belt 12 and the angular velocity controls the transverse movement, it is hence possible to control movement of the surface of the treadmill in any direction. Driving the transverse belts at appropriate speeds allows the rate of movement of the cogs along the chains and the rate of rotation of the cogs to be controlled independently. Figures 4B-4E show four different extremes of motion which can be generated by driving the two driving chains at different speeds. The skilled person will clearly understand that any combination of movement can be achieved. Figure 4A clearly shows that the angular velocity (and accordingly the transverse speed of the transverse belts) is dependent on the difference in the speeds of the chains as follows : V, = VL + r# V, v-ro) where m is the angular velocity of the cog, VL is the longitudinal velocity of the cog, V, and V2 are the velocities of the two drive chains 42 and 40 respectively, and r is the effective radius of the cog being defined by the point of drive of the two chains.

However, w is directly proportional to VT, the transverse speed of the transverse belts, as the two are linked by the gearing mechanism. Hence : Vl = V, t k VT V2 = VL-k VT where k is a constant dependent on the gearing ratio in the transmission to each transverse belt, and the chain speeds V, and V2 can easily be calculated and generated for any required VL and VT.

For example, assuming k= I for simplicity, the following are examples of belt motions : All values are in units of m/s, although the unit is really irrelevant as the values are simply relative to one another:

Shown in V1 V2 VL VT Figure 4B 2 0 1 I Figure 4C 0 2 1-1 Figure 4D 1 I 1 0 Figure 4E 1 -1 0 1 It should be noted that the Cog/chain arrangement could be any engageably interconnecting mechanisms e. g., a toothed belt or simply high friction rollers and belts.

Also, the chains could be provided on one side of the treadmill only, although this would be very unbalanced and is not believed to be advantageous.

It will be clearly understood that the cogs 18 could be replaced by other gear units which can convert the differential movements of the chains 40,42 into linear and angular motions, for example an epi-cyclic gear system.

According to a second embodiment, each of the transverse belt assemblies are either hingedly connected to one another so as to form a continuous loop or are independently drivable around the loop, for example by being attached to a belt or chain. Suitable embodiments providing such a mechanism are shown in WO 97/34663. A similar gearing cog 18 and roller arrangement is provided as in the first embodiment, but in this embodiment, a single driving chain 40 is provided on each side of the treadmill either on the inside or the outside of the loop defined by the path of the cog 18 (i. e. replacing either chain 40 or chain 42 of the first embodiment). The chains 40 are driven by a first driving means, similar to the driving means described in the first embodiment. A second driving means drives the transverse belt assemblies around their loop. It will be apparent that the rate of movement of the transverse belt assemblies along their loop will be determined by the speed of the second driving means, and the rate of transverse movement will be proportional to the difference in speeds of the first and second driving means.

It should be noted that the chains or belts in each pair 40,42 of the first embodiment, or the center of cog 18 and chain 40 in the second embodiment, could be spaced in a non-vertical direction. The rotatable member 18 would then not be vertical and perpendicular to the length of the transverse belts but might, for example, be disposed horizontally with vertical axes as they move across the active part of their paths, and the same effect could be achieved. Spacing the belts vertically is believed to be substantially easier to achieve, and leads to less space being wasted in the width of the treadmill.

AH the alternative embodiments of the invention and modifications thereof described in International Patent Publication WO 97/34663 which could be used in conjunction with the drive mechanism of the present invention are intended to be included in the scope of this application, and would fall under the terms of the present invention.

Claims

Claims 1. Apparatus arranged to provide a continuously moveable surface moveable in any direction within a defined area, comprising a plurality of belt assemblies each comprising a transverse belt forming a loop, each said belt assembly, when in a first configuration, holding said transverse belt to permit rotational movement of said transverse belt along its length; said transverse belt, when in said first configuration, having a substantially straight upper portion relative to said belt assembly, the direction of rotational movement of said upper portion oriented along the length of said belt assembly; wherein a changeable subset of said belt assemblies are arranged in said first configuration in a row with the length of each belt assembly proximal each immediately adjacent belt assembly along a substantial portion of its length, the length of said belt assemblies all oriented in a first direction, each belt assembly further comprising at least one rotatable member mechanically communicating with said transverse belt ; said apparatus further : driving means for driving each of said transverse belts of said subset of said belt assemblies in either direction along its length, and for transporting said subset of belt assemblies across said area, either in a second direction not parallel to said first direction or in a direction opposite said second direction, for removing a belt assembly from one end of said row when the upper portion of the belt no longer lies in said area, and for introducing a belt assembly, in said first configuration, onto the opposite end of said row, to form a new subset in said changeable subset of belt assemblies in a row ; : said driving means comprises at least one member arranged to provide a component of motion in said second direction or said opposite direction to said second direction ; and wherein said member mechanically communicates with the rotatable member of at least one of said belt assemblies in said row to impart a force with a tangential component on said rotational member while said at least one said belt assembly is in said row ; and wherein movement of said member providing said component of motion in said second direction results in an associated change in the rate of rotational motion of the transverse belt of each said at least one belt assembly in said row.
2. Apparatus according to Claim I wherein said member comprises a looped member with a portion of its length oriented in said second direction.
3. Apparatus in accordance with claim 2 wherein said driving means comprises first driving means for transporting said belt units across said area, the rate of said transportation being independent of the rate of movement of said looped member.
4. Apparatus in accordance with Claim 2 further comprising a second looped member arranged to move in a parallel path to said first looped member over a portion of its length in proxirnity to the same end of each of said belt units as the first looped member; said second looped member also engaging said at least one rotatable member, and said first and second looped members in combination holding said rotatable member between them; whereby said rotatable member moves with said first and second looped members at the average of the speeds of the first and second members, and whereby the rotatable member rotates at a rate dependent on the difference between the speeds of the first and second members.
5. Apparatus according to any of claims 2 to 4 wherein each looped member at said one end of said at least one belt assembly has a counterpart looped member at the opposite end of said at least one belt assembly mechanically communicating with a second rotatable member associated with said at least one belt assembly.
6. Apparatus according to any of claims 2 to 5 wherein said rotatable members in each consecutive belt assembly in said row mechanically communicating with said transverse belt are at alternating ends of said belt assembly.
7. Apparatus according to any of claims 2 to 6 wherein said looped member mechanically communicates with said rotatable member over the whole path of transportation of said rotatable member.
8. Apparatus according to any of claims 2 to 7 wherein said first looped member comprises a chain.
9. Apparatus according to any of claims 2 to 7 wherein said first looped member comprises a single piece of material.
10. Apparatus according to claim 1 wherein said member is a worm gear with its axis in said second direction.
11. Apparatus according to any preceding claim further comprising a rail, and wherein each belt assembly is provided with at least one roller, said roller resting on said rail and said rails ensuring that said belt assemblies move in said second direction.
12. Apparatus according to claim 11 wherein said roller on each belt assembly is coaxial with said rotatable member.
13. Apparatus according to any preceding claim wherein said plurality of belt assemblies form a continuous loop of belt assemblies, said subset of belt units being a consecutive set of belt assemblies in said loop, such that belts are removed from and introduced to said row by movement of said belt assemblies around said continuous loop of belt assemblies.
14. Any of the apparatus arranged to provide a continuously moveable surface substantially as herein described with reference to the accompanying drawings