JP7512025B2 - Belt Mechanism - Google Patents

Description

The present invention relates to a belt mechanism.

A known lifting and conveying device is, for example, a pair of endless belts made of multiple toothed belts with both ends connected in a loop by a connector, which are wound around two pairs of toothed pulleys arranged opposite each other above and below, and a loading platform is fixed between the pair of endless belts (see JP 2018-185044 A).

In this lifting and conveying device, one toothed pulley is driven, and the remaining toothed pulleys are driven synchronously via an endless belt made up of toothed belts. When an object is placed on the platform and the toothed pulley is rotated in the forward or reverse direction, the pair of endless belts run, and the object is raised or lowered.

In addition, the lifting and conveying device described in the above publication uses a toothed belt with a belt strength equal to or greater than a predetermined value, making it possible to convey heavy objects.

JP 2018-185044 A

When transporting heavy objects in the vertical direction, the teeth of the toothed belt and the toothed pulley that meshes with it are likely to experience a large impact when the transport begins and a large amount of friction during transport. This impact and wear can cause chipping in the teeth of the toothed belt and accelerate wear of the teeth. For this reason, when transporting heavy objects using the lifting and transporting device described in the above publication, the life of the toothed belt that makes up the endless belt is likely to be shortened.

The present invention was made in consideration of these inconveniences, and aims to provide a belt mechanism that is less likely to shorten the life of the toothed belt even when transporting heavy objects.

The belt mechanism according to one aspect of the present invention includes a flat pulley, a toothed pulley, and an endless belt wound between the flat pulley and the toothed pulley, and an object fixed to the surface of the endless belt can be moved in both directions between the flat pulley and the toothed pulley by the rotational drive of the toothed pulley. The endless belt has a plurality of toothed belts connected in a loop shape, and the toothed belt includes a belt body, a plurality of teeth arranged at equal intervals in the length direction on one side of the belt body, and a plurality of core cords spaced in the width direction of the belt body and embedded in the belt body along the length direction. The plurality of toothed belts are connected so that the toothed belt in contact with the flat pulley is located on the outer surface side of the endless belt, and the toothed belt in contact with the toothed pulley is located on the inner surface side of the endless belt.

In this belt mechanism, one of the pulleys around which the endless belt is stretched is a flat pulley, and the teeth of the toothed belt are located on the outer surface so as not to come into contact with the flat pulley. In this configuration, the belt body comes into contact with the flat pulley. In this case, even if an impact is applied to the endless belt, for example, when conveyance begins, the belt body of the toothed belt and the flat pulley slide appropriately to absorb the impact, preventing damage to the toothed belt that constitutes the endless belt. In addition, since friction between the belt body of the toothed belt and the flat pulley is relatively small, the toothed belt is less likely to wear out. Therefore, in this belt mechanism, the life of the toothed belt that constitutes the endless belt is less likely to be shortened.

It is preferable that the flat pulley is a driven pulley and is disposed above the toothed pulley. By making the flat pulley a driven pulley in this way, the flat pulley rotates along with the endless belt without resisting external forces, and it is easy to absorb changes in the movement of the endless belt transmitted from the toothed pulley, which is the driving pulley. This makes it difficult for the toothed belt that constitutes the endless belt to break or wear out. In addition, by making the flat pulley above where the gravity of the endless belt is likely to be applied, the gravity of the endless belt is relatively less likely to be applied to the toothed pulley, so it is possible to reduce the impact and friction that occurs between the teeth of the toothed belt that constitutes the endless belt and the toothed pulley. This makes it possible to further extend the life of the toothed belt.

The endless belt preferably has two toothed belts. In this belt mechanism, adjacent toothed belts are connected by a connector. For this reason, a flat pulley or a toothed pulley cannot rotate the endless belt beyond the connector. Therefore, by making the number of toothed belts two, the number of connectors required can be reduced, and the range in which the endless belt can be rotated, i.e., the range in which an object fixed to the surface of the endless belt can move, can be made wider.

It is preferable that the toothed belt does not have an interface between the belt body and the multiple teeth. In this way, the toothed belt does not have an interface between the belt body and the multiple teeth, that is, the belt body and the multiple teeth are integrally molded, so that peeling between the belt body and the teeth is less likely to occur, and the life of the toothed belt can be further extended.

As explained above, this belt mechanism is unlikely to shorten the life of the toothed belt even when transporting heavy objects.

FIG. 1 is a schematic side view showing a lifting and conveying device including a belt mechanism according to an embodiment of the present invention. FIG. 2 is a schematic perspective view showing a first toothed belt of the belt mechanism of FIG. FIG. 3 is a schematic cross-sectional view showing the configuration of the second connector of FIG. FIG. 4 is a schematic enlarged partial view of part A in FIG. FIG. 5 is a schematic enlarged partial view of part B in FIG.

One embodiment of the present invention will be described in detail below with reference to the drawings as appropriate.

The lifting and conveying device shown in FIG. 1 has a pair of belt mechanisms 1. The pair of belt mechanisms 1 have the same configuration and include a flat pulley 10, a toothed pulley 20, and an endless belt 30 wound between the flat pulley 10 and the toothed pulley 20.

As shown in FIG. 1, the pair of belt mechanisms 1 are arranged so that the flat pulleys 10 of each of the pair of belt mechanisms 1 face each other in the horizontal direction, and similarly, the toothed pulleys 20 of each of the pair of belt mechanisms 1 face each other in the horizontal direction.

The belt mechanism 1 allows an object X, which is fixed to the surface of the endless belt 30, to be moved in both directions between the flat pulley 10 and the toothed pulley 20 by the rotational drive of the toothed pulley 20.

As shown in FIG. 1, the pair of belt mechanisms 1 are arranged such that the first connectors 33, which will be described later, face each other on the inner periphery of the endless belt 30 (the side closer to the other belt mechanism 1). The object X is stretched between the opposing first connectors 33, and has a base X1 fixed to each first connector 33, and a baggage X2 placed on the base X1.

In this configuration, when the toothed pulley 20 of the belt mechanism 1 located on the left side of the paper in FIG. 1 is rotated clockwise and the toothed pulley 20 of the belt mechanism 1 located on the right side is rotated counterclockwise, the object X moves downward. Conversely, when the toothed pulley 20 of the belt mechanism 1 located on the left side of the paper in FIG. 1 is rotated counterclockwise and the toothed pulley 20 of the belt mechanism 1 located on the right side is rotated clockwise, the object X moves upward. Note that the object X shown in FIG. 1 is an example, and the configuration of the object X fixed to the surface of the endless belt 30 is not limited to this configuration.

<Flat pulley>
The flat pulley 10 is a pulley that does not have teeth on its outer circumferential surface. In other words, the outer periphery of the flat pulley 10 is circular when viewed from the direction of its rotation axis. The flat pulley 10 is also a driven pulley, and is disposed above the toothed pulley 20.

By making the flat pulley 10 a driven pulley in this way, the flat pulley 10 rotates along with the external force without resisting it, making it easier to absorb changes in the movement of the endless belt 30 transmitted from the toothed pulley 20, which is the driving pulley. As a result, the tensile force caused by the difference in rotational speed between the toothed pulley 20 and the flat pulley 10 is less likely to become large, making it less likely that the toothed belt that constitutes the endless belt 30 will break or wear out.

In addition, by placing the flat pulley 10 on the upper side, where the gravity of the endless belt 30 is likely to be applied, the gravity of the endless belt 30 is relatively less likely to be applied to the toothed pulley 20. This reduces the impact and friction that occurs between the toothed pulley 20 and the toothed portion 31b (see Figure 2) of the toothed belt that constitutes the endless belt 30. This makes it possible to further extend the life of the toothed belt.

The flat pulley 10 can be cylindrical, or in other words, straight, but it is preferable that it be cylindrical, thick in the middle, and tapered at both ends, or in other words, crown-shaped. By making the flat pulley 10 a crown type in this way, it is possible to prevent the endless belt 30 from meandering.

The diameter (outer circumference) of the flat pulley 10 is appropriately determined based on the relationship between the conveying speed of the endless belt 30 and the rotation speed of the flat pulley 10, but it is preferable to set it to the same as that of the toothed pulley 20 described below.

<Toothed pulley>
The toothed pulley 20 is a pulley having teeth 21 (see FIG. 5) on its outer circumferential surface. The toothed pulley 20 is a drive pulley, and is disposed below the flat pulley 10.

Since the toothed pulley 20 is a drive pulley, its central axis is rotated by a drive device such as a motor. As shown in FIG. 1, the movable range of the first connector 33 is at most up to the point where it abuts against the flat pulley 10 and down to the point where it abuts against the toothed pulley 20. If the first connector 33 exceeds the above range, there is a risk of damage to the first connector 33 or the object X. Therefore, it is preferable that the belt mechanism 1 has a control unit that controls the drive of the drive device and controls the movement of the first connector 33 within the above range.

The diameter of the toothed pulley 20 (the diameter of the outer circumference excluding the teeth portion 21) is appropriately determined based on the rotation speed and torque of the drive device and the desired conveying speed for the object X.

<Endless belt>
The endless belt 30 has two toothed belts (a first toothed belt 31 and a second toothed belt 32) and two connectors (a first connector 33 and a second connector 34).

As shown in FIG. 1, both ends of the first toothed belt 31 and both ends of the second toothed belt 32 are connected by a first connector 33 and a second connector 34, respectively, and the endless belt 30 is connected in a loop shape.

(Toothed belt)
The two toothed belts have the same configuration. Taking the first toothed belt 31 as an example, the first toothed belt 31 includes a belt body 31a, a plurality of teeth 31b arranged at equal intervals in the length direction on one surface of the belt body 31a, and a plurality of core cords 31c spaced apart in the width direction of the belt body 31a and embedded in the belt body 31a along the length direction, as shown in Fig. 2.

[Belt body]
The main component of the belt body 31a is rubber or resin. Examples of the rubber include ethylene-α-olefin elastomers such as ethylene-propylene rubber (EPR) and ethylene propylene diene monomer rubber (EPDM), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), and hydrogenated nitrile rubber (H-NBR). The rubber may be one of these, or may be a blend of two or more of these. Examples of the resin include thermoplastic polyester, polyamide, and polyurethane. The main component of the belt body 31a is preferably a resin from the viewpoint of low dust generation, and among these, thermoplastic urethane, which has excellent abrasion resistance, is preferable. Here, the term "main component" refers to the component with the highest content, and preferably refers to a component with a content of 50% by mass or more, and more preferably 90% by mass or more.

The average thickness of the belt body 31a is determined appropriately depending on the strength required for the first toothed belt 31, and can be, for example, 1 mm or more and 10 mm or less.

The length of the belt body 31a is the length required for the endless belt 30 to be wound around the flat pulley 10 and the toothed pulley 20. For example, the length of the belt body 31a can be the distance between the flat pulley 10 and the toothed pulley 20 plus 1/4 of the circumference of the flat pulley 10 and 1/4 of the circumference of the toothed pulley 20. The distance between the flat pulley 10 and the toothed pulley 20 is determined according to the height to which the object X is moved. The second toothed belt 32 is the same length as the first toothed belt 31.

The belt body 31a may contain various additives. Examples of such additives include antioxidants, heat stabilizers, light stabilizers, anti-fogging agents, flame retardants, surface conditioners, pigments, fillers, waxes, etc.

[Tooth part]
The tooth portion 31b is a convex portion having a cross section of a trapezoid, a triangle, a semicircle, a mountain shape, a wave shape, a normal distribution curve shape, etc. The tooth portion 31b is arranged so that its ridge line (axial direction) coincides with the width direction of the belt main body 31a.

The average height of the tooth portions 31b and the pitch between the tooth portions 31b are appropriately determined depending on the weight of the object X, etc. The average height of the tooth portions 31b can be, for example, 1.0 mm or more and 10 mm or less. The pitch between the tooth portions 31b can be, for example, 10 mm or more and 30 mm or less.

For at least the second toothed belt 32, the average height and pitch of the teeth 21 of the toothed pulley 20 and the teeth 32b of the second toothed belt 32 are specified so that they mesh with each other (see Figure 5).

The main components of the tooth portion 31b can be the same as those of the belt body 31a. The tooth portion 31b may also contain the same additives as those of the belt body 31a.

The first toothed belt 31 does not have an interface between the belt body 31a and the multiple toothed portions 31b, that is, the belt body 31a and the multiple toothed portions 31b are preferably integrally molded. Since the first toothed belt 31 does not have an interface between the belt body 31a and the multiple toothed portions 31b in this way, peeling between the belt body 31a and the toothed portions 31b is less likely to occur. The life of the first toothed belt 31 can be further extended.

The same is true for the second toothed belt 32, but it is particularly preferable that the first toothed belt 31 does not have an interface between the belt body 31a and the multiple toothed portions 31b. As described later, in the belt mechanism 1, the first toothed belt 31 that contacts the flat pulley 10 is used with the belt body 31a on the inner periphery. Since the belt body 31a is strip-shaped and has no notches, it is more susceptible to bending stress than when the discretely arranged toothed portions 31b are used as the inner periphery, and if it has an interface, peeling is more likely to occur starting from the interface. In contrast, by not having an interface between the belt body 31a and the multiple toothed portions 31b, the starting point of peeling is eliminated, and peeling between the belt body 31a and the toothed portions 31b can be effectively prevented.

The first toothed belt 31, which does not have an interface between the belt body 31a and the multiple teeth 31b, can be obtained, for example, by extruding a resin composition for forming the belt body 31a and the multiple teeth 31b around multiple parallel core cords 31c.

[Core cord]
The core cords 31c are linear bodies having a circular cross section. The core cords 31c are embedded in the belt body 31a. The core cords 31c are arranged parallel to the length direction of the belt body 31a and at a constant distance from the other surface of the belt body 31a (the surface on which the toothed portion 31b is not arranged). In other words, the core cords 31c are arranged in a plane, and the plane formed by the core cords 31c is parallel to the surface of the belt body 31a. The core cords 31c are also arranged at equal intervals. The strength, durability, driving accuracy, etc. of the first toothed belt 31 can be improved by the core cords 31c.

The main components of the core cord 31c are not particularly limited, but examples include steel, aramid, carbon, glass, polyester, etc.

The cross-sectional diameter of the core cord 31c is not particularly limited, but is generally 0.2 mm or more and 2.5 mm or less.

The lower limit of the average spacing between the core cords 31c (the distance between the central axes of the core cords 31c) is preferably 0.3 mm. On the other hand, the upper limit of the average spacing between the core cords 31c is preferably 4 mm. If the average spacing between the core cords 31c is less than the above lower limit, the flexibility of the first toothed belt 31 may be insufficient. Conversely, if the average spacing between the core cords 31c exceeds the above upper limit, the effect of the core cords 31c in improving the strength, durability, driving accuracy, etc. of the belt may be insufficient.

In addition, the lower limit of the average distance between the central axis of the outermost core cord 31c and the side of the belt body 31a adjacent thereto (also referred to as the "average distance between the core cord 31c and the side of the belt body 31a") is preferably 0.3 mm, more preferably 0.5 mm. On the other hand, the upper limit of the average distance between the core cord 31c and the side of the belt body 31a is preferably 1 mm, more preferably 0.7 mm. If the average distance between the core cord 31c and the side of the belt body 31a is less than the lower limit, the outermost core cord 31c may be exposed from the side of the belt body 31a during the manufacture of the first toothed belt 31. Conversely, if the average distance between the core cord 31c and the side of the belt body 31a exceeds the upper limit, the side edge of the belt body 31a may easily flutter when driven, and the effect of improving the accuracy of the drive by the core cord 31c may be insufficient. In addition, there are two outermost core cords 31c on both sides of the belt body 31a.

The number of core cords 31c is determined by the average width of the belt body 31a, the average spacing between the core cords 31c, and the average distance between the core cords 31c and the side of the belt body 31a, but the number of core cords 31c is usually 10 or more and 100 or less.

(Connector)
The first connector 33 and the second connector 34 connect the ends of the adjacent toothed belts, i.e., the first toothed belt 31 and the second toothed belt 32. As described above, one end of the base X1 of the object X is connected to the first connector 33.

The structure for connecting the ends of the first toothed belt 31 and the second toothed belt 32 will be described using the second connector 34 shown in Figure 3 as an example.

The second connector 34 shown in FIG. 3 has a pair of plates (first plate 34a and second plate 34b) that sandwich the first toothed belt 31 and the second toothed belt 32, and a number of fasteners 34c that fasten the pair of plates.

The first toothed belt 31 and the second toothed belt 32 are connected in a straight line by the second connector 34 so that their ends abut each other, as shown in FIG. 3.

As shown in FIG. 3, the first plate material 34a has projections and recesses in the area where the first toothed belt 31 contacts it, which mesh with the toothed portion 31b of the first toothed belt 31, and has a flat surface where the belt body 32a of the second toothed belt 32 contacts it, in the area where the second toothed belt 32 contacts it.

On the other hand, the second plate material 34b has projections and recesses in the area where the second toothed belt 32 contacts, which mesh with the toothed portion 32b of the second toothed belt 32, and has a flat surface where the belt body 31a of the first toothed belt 31 contacts, in the area where the first toothed belt 31 contacts.

The first plate material 34a and the second plate material 34b are fastened together by a number of fasteners 34c. These fasteners 34c can be composed of bolts and nuts, for example.

In this way, the first toothed belt 31 and the second toothed belt 32 are connected by fastening the first plate material 34a and the second plate material 34b with the multiple fasteners 34c. At this time, the teeth 31b of the first toothed belt 31 mesh with the unevenness of the first plate material 34a, and the teeth 32b of the second toothed belt 32 mesh with the unevenness of the second plate material 34b, so that the first plate material 34a and the second plate material 34b can be prevented from slipping out of the second connector 34.

The first connector 33 can also connect the other ends of the first plate material 34a and the second plate material 34b in a similar configuration. The base X1 of the object X is also connected to the first connector 33, and this connection can also be achieved by using fasteners such as bolts and nuts.

The connection structure shown in FIG. 3 is one example, and does not exclude other connection structures. For example, some of the teeth 31b of the toothed belt 31 can be meshed with the same number of teeth 32b of the second toothed belt 32, and a pair of plate members can be abutted against the belt body 31a of the first toothed belt 31 and the belt body 32a of the second toothed belt 32, respectively, to fasten them together.

<Relationship between pulley and toothed belt>
In the belt mechanism 1, as shown in FIG. 4, the teeth 31b of the first toothed belt 31, which is a toothed belt that contacts the flat pulley 10, is located on the outer surface side of the endless belt 30.

In this case, the belt body 31a of the first toothed belt 31 abuts against the flat pulley 10. The surface of the belt body 31a is flat and without any irregularities. On the other hand, the surface of the flat pulley 10 is also without any irregularities, so the flat pulley 10 and the first toothed belt 31 come into contact with each other on their faces. Since the flat pulley 10 is a driven pulley, when the endless belt 30 moves due to the rotation of the toothed pulley 20, the first toothed belt 31, which constitutes part of the endless belt 30, moves, and the friction of this contact surface causes the flat pulley 10 to rotate along with it.

At this time, for example, if the first toothed belt 31 suddenly starts moving from a stationary state, there is only surface contact with the flat pulley 10. Therefore, even if the flat pulley 10 cannot follow the movement of the first toothed belt 31, slippage occurs between the flat pulley 10 and the first toothed belt 31, and the first toothed belt 31 is not pulled strongly. Therefore, the endless belt 30 of the belt mechanism 1 is less likely to be damaged.

In addition, even when the first toothed belt 31 moves at a relatively constant speed, this moderate slippage can prevent force from concentrating on a specific portion of the first toothed belt 31. As a result, the wear of the endless belt 30 is less likely to be biased depending on the position, and the belt wears relatively evenly. Since the lifespan of the endless belt 30 due to wear is determined by the position where wear has progressed the most, uniform wear results in a longer lifespan. In other words, the lifespan of the endless belt 30 of the belt mechanism 1 is less likely to be shortened.

On the other hand, in the belt mechanism 1, as shown in FIG. 5, the tooth portion 32b of the second toothed belt 32, which is a toothed belt that contacts the toothed pulley 20, is located on the inner surface side of the endless belt 30.

In this case, the toothed pulley 20 is in contact with the toothed portion 32b of the second toothed belt 32. The toothed pulley 20 has teeth 21 on its outer circumferential surface, which mesh with the teeth 32b of the second toothed belt 32. Since the toothed pulley 20 is a driving pulley, the rotation of the driven toothed pulley 20 is reliably transmitted as the movement of the second toothed belt 32, i.e., the movement of the endless belt 30, by the meshing of the teeth 21 of the toothed pulley 20 with the teeth 32b of the second toothed belt 32. Therefore, the transmission efficiency from the toothed pulley 20, which is the driving pulley, to the endless belt 30 is high, and energy consumption is reduced.

<Advantages>
In the belt mechanism 1, one of the pulleys around which the endless belt 30 is stretched is a flat pulley 10, and the teeth 31b of the first toothed belt 31 are located on the outer surface side so as not to come into contact with the flat pulley 10. In this configuration, the belt body 31a comes into contact with the flat pulley 10. In this case, even if an impact is applied to the endless belt 30 at the start of conveyance, the belt body 31a of the first toothed belt 31 and the flat pulley 10 slide appropriately to absorb the impact, and damage to the first toothed belt 31 and the second toothed belt 32 constituting the endless belt 30 is suppressed. In addition, since friction between the belt body 31a of the first toothed belt 31 and the flat pulley 10 is relatively small, the first toothed belt 31 is unlikely to wear out. Therefore, in the belt mechanism 1, the life of the first toothed belt 31 and the second toothed belt 32 constituting the endless belt 30 is unlikely to be shortened.

In addition, in the belt mechanism 1, the adjacent first toothed belt 31 and second toothed belt 32 are connected by the first connector 33 and second connector 34. Therefore, the flat pulley 10 and toothed pulley 20 cannot rotate the endless belt 30 beyond the first connector 33 and second connector 34. Therefore, by limiting the number of toothed belts to two in this way, the number of connectors required can be reduced, and the range in which the endless belt 30 can be rotated, i.e., the range in which the object X fixed to the surface of the endless belt 30 can move, can be made wider.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and can be embodied in various other forms in addition to the above-described forms with various modifications and improvements.

In the above embodiment, the endless belt has two toothed belts, but the number of toothed belts is not limited to two and may be three or more.

In the above embodiment, the flat pulley is disposed above the toothed pulley, but the flat pulley may be disposed below the toothed pulley. The flat pulley may be positioned differently in each of the pair of belt mechanisms, but from the viewpoint of conveyance controllability, it is preferable that the flat pulley be positioned the same in each of the pair of belt mechanisms.

In addition, in the above embodiment, the flat pulley is described as a driven pulley, but the flat pulley can also be a driving pulley.

In the above embodiment, the lifting and conveying device has a pair of belt mechanisms, but the lifting and conveying device may be composed of one belt mechanism or three or more belt mechanisms.

In the above embodiment, the belt mechanism of the present invention is described as being used in a lifting and conveying device, but the use of the belt mechanism of the present invention is not limited to lifting and conveying devices, and it can also be used, for example, in a horizontal conveying device.

The belt mechanism of the present invention is less likely to shorten the life of the toothed belt even when transporting heavy objects.

REFERENCE SIGNS LIST 1 Belt mechanism 10 Flat pulley 20 Toothed pulley 21 Toothed portion 30 Endless belt 31 First toothed belt 31a Belt body 31b Toothed portion 31c Core cord 32 Second toothed belt 32a Belt body 32b Toothed portion 33 First connector 34 Second connector 34a First plate material 34b Second plate material 34c Fastener X Object X1 Base X2 Baggage

Claims (4)

Flat pulley,
A toothed pulley;
an endless belt wound between the flat pulley and the toothed pulley,
An object fixed to the surface of the endless belt can be moved in both directions between the flat pulley and the toothed pulley by the rotational drive of the toothed pulley,
The endless belt has a plurality of toothed belts connected in a loop shape,
The toothed belt is
The belt body,
A plurality of teeth are disposed on one surface of the belt body at equal intervals in the longitudinal direction;
a plurality of core cords spaced apart in the width direction of the belt body and embedded in the belt body along the length direction,
At least the cross section, average height, pitch and main component of the tooth portions of the plurality of toothed belts are the same,
A belt mechanism in which the multiple toothed belts are connected in a straight line with their ends abutting each other, so that the toothed portion of the toothed belt that contacts the flat pulley is located on the outer side of the endless belt, and the toothed portion of the toothed belt that contacts the toothed pulley is located on the inner side of the endless belt. The belt mechanism according to claim 1, wherein the flat pulley is a driven pulley and is disposed above the toothed pulley. The belt mechanism according to claim 1 or 2, wherein the endless belt has two toothed belts. 4. The belt mechanism according to claim 1, 2 or 3, wherein the toothed belt has no interface between the belt body and the plurality of teeth.

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