WO2007070057A1

WO2007070057A1 - Drive belt with lateral surface protection

Info

Publication number: WO2007070057A1
Application number: PCT/US2005/045626
Authority: WO
Inventors: John P. Wesson
Original assignee: Otis Elevator Company
Priority date: 2005-12-16
Filing date: 2005-12-16
Publication date: 2007-06-21

Abstract

A drive belt (30) includes a body portion having at least a drive surface (32) adapted to engage a member (23) to be driven by the drive belt (30). At least a portion of at least one lateral surface (42) includes a protective layer (50). In a disclosed example, the body of the belt (30) is formed using a first polymer material and the protective layer (50) is formed using a second, different polymer material. The protective layer (50) can have different wear characteristics to resist abrasion, for example, and a different hardness or friction characteristic than the material selected to form the body of the belt including the drive surface (32).

Description

DRIVE BELT WITH LATERAL SURFACE PROTECTION

Field of the Invention [0001] This invention generally relates to drive belts. More particularly, this invention relates to a drive belt configuration including lateral surface protection.

Description of the Related Art

[0002] Drive belts are used for a variety of applications. Automobiles are one example that incorporate drive belts for providing rotary movement to a variety of components. More recently, drive belts have been proposed for use in passenger conveyor systems for driving the step chain, which was previously driven by a sprocket. Another recent innovative proposal has been to utilize a drive belt configuration for propelling a passenger conveyor hand rail. [0003] Depending on the application of a drive belt, there may be different needs for different material properties on various surfaces of the drive belt. For example, in the case of an automotive V-shaped belt, the two surfaces along the sides of the V need to have appropriate friction characteristics for proper engagement with the V-shaped pulley groove that they engage. In the case of a toothed or cogged belt, the teeth typically need an appropriate friction characteristic to provide the desired amount of engagement with the cooperating teeth that are driven by the belt or that are used to drive the belt, depending on the configuration.

[0004] Various and sometimes conflicting requirements place limitations on the materials that can be used to form such belts. For example, the belt material needs to be easily moldable to promote manufacturing. At the same time, the belt should have sufficient stiffness and tear strength to transmit driving forces. Low friction is required in many circumstances to minimize power dissipation and noise. It is also desirable to have low wear rates and good fatigue life so that the belt will have a sufficiently long operating life to make it economical. A selected material must also be able to deal with varying operating conditions such as temperature, humidity and exposure to various substances. Some or all of these considerations have to be balanced with reasonable cost of materials for a particular application.

[0005] Another situation arises in the manufacture of some drive belts. In some examples, drive belt stock is cut in a longitudinal direction to establish a desired width of the belt product. Some drive belt stock includes reinforcing members or tension members such as steel or synthetic fiber cords running generally longitudinally through the belt stock. During the cutting process, such cords may be exposed at the lateral edges of the belt. In some cases, the reinforcing members are wound helically through the belt stock. As the stock is cut into narrower belts, one end of each reinforcing member will be exposed on either side face. The typical approach in either case is to grind down or cut an exposed cord and to push it back into the edge of the belt material.

[0006] One difficulty encountered with such arrangements is that over time the cords exposed at the lateral edges of the belt can become lose as a result of normal operation or wear on the lateral surface of the belt. When this happens, it reduces the quality of the belt operation and can interfere with machinery in the vicinity of the belt. For example, if an exposed cord is snagged, it will pull out and the belt can be destroyed. Adding additional belt material simply to seal the side faces is not cost effective.

[0007] It is desirable to avoid conditions where the integrity of a drive belt is compromised to provide more reliable operation and longer belt life. At the same time, it is desirable to minimize the costs associated with making such belts. This invention provides an improved arrangement that allows for improving belt wear characteristics and staying within cost and other material considerations.

SUMMARY OF THE INVENTION

[0008] An exemplary drive belt includes a body comprising a first polymer material that establishes a drive surface for interacting with a member to be driven by the drive belt. A protective layer comprises a second, different polymer material on at least a portion of at least one lateral surface of the body.

[0009] One example includes the protective layer on each of two lateral surfaces of the body.

[00010] One example includes at least one tension member within the body and the protective layer covers over at least a portion of the lateral surface that is aligned with the at least one tension member.

[00011] An exemplary method of making a drive belt includes forming a belt body using a first polymer material such that the belt body has a drive surface adapted to engage a member to be driven by the belt. At least a portion of a lateral surface of the belt body is then coated with a second, different polymer material.

[00012] One example includes coating the entire lateral surface of the belt body. [00013] One example includes molding the belt body and overmolding the second polymer material onto the at least a portion of the lateral surface.

[00014] The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[00015] Figure 1 schematically illustrates a passenger conveyor including a drive belt designed according to an embodiment of this invention.

[00016] Figure 2 is a perspective, diagrammatic illustration of a portion of one example drive belt.

[00017] Figure 3 is a cross-sectional illustration of one example embodiment taken along the lines 3-3 in Figure 2.

[00018] Figure 4 is a cross-sectional illustration of another example embodiment from a similar perspective as that in Figure 3. [00019] Figure 5 is a cross-sectional illustration of another example embodiment.

[00020] Figure 6 is a cross-sectional illustration of another example embodiment.

DETAILED DESCRIPTION

[00021] This invention relates to drive belts and provides a protective layer on at least a portion of at least one lateral surface of the drive belt. Using such a protective layer allows for more freedom in material selections for establishing the body of the drive belt and improves the wear characteristics of the belt to enhance belt life and performance. In a disclosed example, the protective layer serves several functions including covering exposed reinforcing members on side faces of the belt, reducing friction along the side faces and hardening the side faces to reduce wear or abrasion. [00022] One example use of a drive belt designed according to an embodiment of this invention is within a passenger conveyor system. Figure 1 shows an example passenger conveyor 20 that is an escalator. The example includes a plurality of steps 22 that move with a step chain 23 to carry passengers between landings 24 and 26. The illustrated example includes a handrail 28 that moves in unison with the steps 22. [00023] An example drive belt 30 is used in the illustration of Figure 1 for driving or propelling the step chain 23 that causes the desired movement of the steps 22. Although not illustrated, another example drive belt 30 is used for propelling or driving the handrail 28. [00024] Figure 2 shows one example drive belt configuration having a body comprising a first polymer material such as an elastomer. In this example, the drive belt 30 includes a drive surface 32 that is adapted to engage a member to be driven by the drive belt 30. In the example of Figure 1, the drive surface 32 engages the step chain 23. The example drive surface 32 includes a plurality of teeth 36 that are oriented generally perpendicular to a longitudinal length of the belt 30. In this example, the teeth are generally perpendicular to the direction of movement caused by the drive belt 30.

[00025] An oppositely facing side of the example belt 30 is a driven surface 38 that is adapted to engage at least one member for causing desired movement of the belt 30. In this example, the driven surface 38 includes a plurality of teeth 40 to cooperate with an appropriately configured drive member (e.g., a toothed wheel). The teeth 40 in this example extend generally perpendicular to the longitudinal length of the belt 30.

[00026] The illustration in Figure 2 shows one of the lateral surfaces 42 on the example belt 30. The lateral surfaces 42 in this example extend along opposite lateral edges of the belt 30 parallel with the longitudinal direction or length of the belt.

[00027] Referring to Figure 3, the example belt 30 includes a central portion 44 between the teeth 36 of the drive surface 32 and the teeth 40 of the driven surface 38.

A plurality of reinforcing cords or tension members 46 are encased within the material used for forming the central portion 44. In one example, the tension members 46 comprise steel cords.

[00028] One feature of the illustrated example is that the lateral surfaces 42 include a protective coating 50 to provide desired wear characteristics on the lateral surfaces 42. In the example of Figure 3, the entire lateral surface 42 on both lateral sides of the belt 30 is entirely coated with the protective layer 50.

[00029] In one example, the protective layer 50 comprises a second, different polymer composition than the first polymer material used to form the body of the belt 30 (e.g., the teeth 36, the teeth 40 and the central portion 44). Using a different polymer material on at least one of the lateral surfaces 42 allows for providing a protective, wear resistant layer 50 on a selected portion of at least one of the lateral surfaces 42 to meet the needs of a particular situation. For example, the second polymer material may be more resistant to abrasion, harder and have different molding properties and friction characteristics than the first polymer material. At the same time, the material selection for forming the body of the belt 30 can be based upon considerations other than wear at the lateral surfaces 42. One advantage to this example is that it allows for a wider range of freedom in material selection while still accomplishing the sometimes competing goals of achieving appropriate friction characteristics on drive and driven surfaces of a belt, achieving desired wear characteristics for a variety of surfaces on a belt and maintaining material costs within desired limits for selected molding techniques, for example.

[00030] Figure 4 illustrates another example embodiment where the protective layer 50 covers over the lateral surfaces 42 of the central portion 44 and the teeth 40 of the example belt 30. Another example is shown in Figure 5 where only the central portion 44 includes a protective layer 50. Given this description, those skilled in the art will be able to select appropriate portions of at least one lateral surface on a drive belt upon which to provide the protective layer 50 to realize the benefits of the disclosed examples for meeting the needs of their particular situation. [00031] Example materials used for forming the body of the example belt 30 include castable polyurethane materials composed of polyether, polyester or polycaprolactone prepolymer combined with TDI, MDI or PPDI diisocyanate endblocks. These can be cured with commercially available curatives such as, but not limited to, MBCA or 1,4-Butanediol to give an elastomer with required properties. Examples include, but are not limited to, Crompton Adiprene L167 (ether-TDI) cured with MBCA or Crompton Vibrathane 8595 (ester-MDI) cured with 1,4 Butandiol. Other examples include two part or castable polyurethanes, vulcanized high performance rubber, such as Hypalon, thermoplastic polyurethane elastomers and thermoplastic polyester elastomers with satisfactory properties fro the application. [00032] Example materials for forming the protective layer 50 include polyurethanes having wear characteristics that render the material more resistant to wear than the material selected to form the body. Some polyurethanes include para- phenylene diisocyante as a building block to increase the toughness of the polyurethane. Other high performance TPU can also be based on MDI or NDI formulations. An example of a high performance ether PPDI-TPU is Crompton Adiprene PP 1095, which is a 1,4 butanediol cured ether-PPDI TPU formulation. Such materials are useful in some example embodiments. Some examples include a lubricant added to the second polymer material to reduce friction along the portions coated with the protective layer 50. Other example materials include solid or liquid fluoropolymer particles or droplets, MoS2 powder, solid lubricant powders such as

POM, graphite powder or short chopped polyester, fluoropolymer or carbon fibers where the fibers can be oriented preferentially to be parallel to the direction of travel.

[00033] In the example of Figure 5, the protective layer 50 is over the central portion 44 to protect against one of the tension members 46 near a lateral edge from protruding outward as a result of wear on the corresponding lateral surface 42, for example.

[00034] Figure 6 shows another example embodiment where the teeth 36 on the drive surface 32 extend in a longitudinal direction and have a so-called V-groove orientation to cooperate with an appropriately configured member to be driven by the belt 30. In that example, only a portion of each lateral surface 42 has the protective layer 50.

[00035] An example technique for making the embodiment illustrated in Figure 2 includes forming the body of the belt 30 to establish the drive surface 32, the driven surface 38 and the central portion 44 in a desired configuration. In some examples, a size of the belt stock will be wider and longer than the belt size needed for a particular application. The belt stock can then be cut to appropriate widths and lengths. The cut belt stock can then be coated with the protective layer 50 using an overmolding technique. [00036] One example includes placing the cut belt stock within a mold that is used to form the protective layer and secure it to the chosen portions of the appropriate lateral surface 42 of the cut belt stock. In another example, the overmolding includes rolling on the material selected to form the protective layer on the appropriate portions of corresponding lateral surface 42. Another example overmolding technique includes brushing on the material for forming the protective layer 50. Still another example includes spraying on the material for forming the protective layer 50.

[00037] Given this description, those skilled in the art will be able to select appropriate materials to meet the needs of their particular situation and to realize a good combination of materials that will provide good adhesion between the first polymer used to form the belt body and the second polymer used to form the protective layer 50. Sufficient adhesion will resist removal of the protective layer from the corresponding lateral surface under most expected operating conditions. Material selection and application technique will control the bond between the first and second materials.

[00038] The disclosed examples provide several advantages including allowing more freedom in material selection, which renders molding processes more economical and efficient in some situations. It also reduces the potential for defects in the belt stock.

[00039] A resulting belt has better performance and an increased operating life because of the presence of the protective layer 50, for example. The ability to use harder materials for the protective layer 50 provides better wear resistance and improved belt life. At the same time, it will not interfere with the desired operating characteristics of the material selected for forming the belt body.

[00040] Another advantage is that steel cords or other tension members within the belt can be covered at the lateral surfaces to prevent protrusion over time.

[00041] Another advantage of a disclosed example is that it improves the manufacturing processes and allows for selecting more economical materials so that overall cost for making a drive belt can be reduced.

[00042] The preceding description is exemplary rather than limiting in nature.

Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

Claims

CLAIMSI claim:

1. A drive belt comprising: a body comprising a first polymer material that establishes a drive surface for interacting with a member to be driven by the drive belt; and a protective layer comprising a second, different polymer material on at least a portion of at least one lateral surface of the body.

2. The drive belt of claim 1, comprising the protective layer on each of two lateral surfaces of the body.

3. The drive belt of claim 1, comprising at least one tension member within the body; and wherein the protective layer covers over at least a portion of the lateral surface that is aligned with the at least one tension member.

4. The drive belt of claim 1, wherein the drive surface comprises a plurality of teeth.

5. The drive belt of claim 4, wherein the plurality of teeth are oriented transverse to the lateral surface.

6. The drive belt of claim 5, wherein the protective layer covers the lateral surface of each of the drive surface teeth.

7. The drive belt of claim 4, wherein the plurality of teeth are oriented generally parallel with the lateral surface.

8. The drive belt of claim 1, wherein the drive surface comprises a plurality of teeth; the body establishes a driven surface facing opposite the drive surface, the driven surface being adapted for interacting with a member for driving the drive belt; and the protective layer covers over the at least a portion of the at least one lateral surface between the drive surface teeth and the driven surface teeth.

9. The drive belt of claim 8, wherein the protective layer covers over the at least one lateral surface of at least one of the drive surface teeth or the driven surface teeth.

10. The drive belt of claim 8, wherein the protective layer covers over the at least one lateral surface of the drive surface teeth and the lateral surface of the driven surface teeth.

11. The drive belt of claim 1, wherein the first polymer material comprises a first polyurethane and the second, different material comprises a second, different polyurethane material.

12. The drive belt of claim 1, wherein the first polymer material comprises a first friction characteristic and the second, different polymer material comprises a second, relatively lower friction characteristic.

13. The drive belt of claim 1, wherein the first polymer material has a first wear characteristic and the second, different polymer material has a second wear characteristic that is relatively more resistant to wear.

14. The drive belt of claim 1, wherein the first polymer material comprises a polyurethane elastomer; and the second polymer material comprises at least one of a thermoplastic polyurethane or a thermoset polyurethane and comprises at least one of graphite, fluoropolymer powder or MoS2.

15. A method of making a drive belt, comprising: forming a belt body using a first polymer material such that the belt body has a drive surface adapted to engage a member to be driven by the belt; and coating at least a portion of at least one lateral surface of the belt body with a second, different polymer material.

16. The method of claim 15, comprising coating the entire at least one lateral surface of the belt body.

17. The method of claim 15, comprising coating at least a portion of each of two oppositely facing lateral surfaces of the belt body.

18. The method of claim 15, comprising including at least one tension member within the belt body; and coating at least the portion of the at least one lateral surface that is generally aligned with the at least one tension member.

19. The method of claim 15, comprising molding the belt body; and overmolding the second polymer material onto the at least a portion of the lateral surface.

20. The method of claim 15, comprising including a lubricant in the second polymer material.