HAVING A FRICTION STABILIZER IN THE POLYMER JACKET MATERIAL

BACKGROUND

[0001] There are various uses for elongated flexible assemblies such as for elevator load bearing members or roping arrangements, drive belts for machines such as a passenger conveyor and handrails for passenger conveyors, for example. Such assemblies may be designed with a plurality of cords covered by a polyurethane jacket. For example, U.S. Patent Nos. 6,295,799 and 6,739,433 show belts for use in suspending an elevator car and counterweight within an elevator system. An example passenger conveyor handrail construction is shown in U.S. Patent No. 4,982,829. An example passenger conveyor drive belt is shown in U.S. Patent No. 6,540,060.

[0002] One aspect of such assemblies is that they interact with other system components. The coefficient of friction between the jacket and the other system components typically is chosen to achieve satisfactory performance. For example, some friction is desired to achieve sufficient traction between elevator load bearing members and a traction sheave for controlling movement of the elevator car. The surface roughness on the sheave, the jacket or both is one factor that influences the coefficient of friction between them. Another factor is the chemical composition of the jacket material.

[0003] Handrails for passenger conveyors have other friction characteristic requirements. One side of the handrail slides along a guidance. That movement of the handrail preferably occurs with limited or no friction between the handrail and the guidance. The other side of the handrail provides a gripping surface for passengers riding on the conveyor. The gripping surface requires different friction characteristics. The gripping surface is often engaged by rollers used for driving the handrail. It is necessary in such arrangements to maintain a sufficient amount of friction between the handrail and the drive arrangement to achieve the desired movement.

[0004] Over time, the coefficient of friction between such components tends to change. The surface roughness, surface chemistry or both can change, for example. Surface contaminants may accumulate that need to be removed. Cleaning solvents or lubricants may be used during maintenance procedures. Any of these factors can alter the surface roughness, chemistry or both, which further increases the variability in friction characteristics of the components. Additional efforts are required to try to maintain desired friction characteristics. Even when known attempts are made, the results are not consistent or precise enough. Maintaining consistent friction properties is desirable for maintaining a desired level of performance, for example.

SUMMARY

[0005] An exemplary assembly includes at least one elongated tension member. A jacket covers at least some of the tension member. The jacket comprises a polymer material including a friction stabilizer that facilitates maintaining a desired friction characteristic of at least an exterior surface on the jacket.

[0006] An exemplary method of making an assembly having at least one elongated tension member at least partially covered by a jacket includes mixing a friction stabilizer with a polymer base resin to provide a master batch of mixed material. The mixed material is then compounded with a base polymer material to yield a jacket material. The jacket material is then molded onto at least a portion of the tension member to form a desired shape of the jacket.

[0007] The various features and advantages of the disclosed examples 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

[0008] Figure 1 schematically illustrates selected portions of an elevator system including a load bearing member designed according to an embodiment of this invention.

[0009] Figure 2 is an end view schematically showing one example elevator load bearing member assembly.

[00010] Figure 3 is an end view schematically illustrating another example elevator load bearing assembly.

[00011] Figure 4 diagrammatic ally illustrates a passenger conveyor including a drive belt and a handrail designed according to an embodiment of this invention.

[oooi2] Figure 5 schematically shows an example drive belt configuration. [00013] Figure 6 schematically shows an example handrail configuration. [oooi4] Figure 7 schematically illustrates an example method of making an assembly designed according to an embodiment of this invention.

DETAILED DESCRIPTION

[oooi5] Figure 1 schematically shows selected portions of an example elevator system 20. An elevator car 22 and counterweight 24 are suspended by a load bearing assembly 26. In one example, the load bearing assembly 26 comprises a plurality of flat belts. In another example, the load bearing assembly 26 comprises a plurality of round ropes.

[00016] The load bearing assembly 26 supports the weight of the elevator car 22 and the counterweight 24 and facilitates movement of the elevator car 22 into desired positions by moving along sheaves 28 and 30. One of the sheaves will be a traction sheave that is moved by an elevator machine in a known manner to cause the desired movement and placement of the elevator car 22. In some instances, such as with flat belts, the traction sheave could comprise the shaft of the machine (i.e. not a separate component mounted to the shaft). The other sheave in this example is an idler sheave.

[oooi7] Figure 2 is an end view schematically showing one example flat belt configuration of the example load bearing assembly 26. In this example, the flat belt includes a plurality of elongated cord tension members 32 and a polymer jacket 34 that contacts the tension members 32. In this example, the jacket 34 encases the tension members 32. In one example, the tension members 32 comprises wound metallic cords, such as steel. The polymer jacket 34 in one example comprises a thermoplastic elastomer. In one example, the jacket 34 comprises a thermoplastic polyurethane.

[00018] Another example is schematically shown in Figure 3. An end view of a rope used as part of the load bearing assembly 26 includes at least one tension member 32 and a polymer jacket 34. In the example of Figure 3, the same materials can be used as those mentioned above.

[oooi9] The load on the example belt is carried by the tension members 32. The interaction between the jacket 34 and the sheaves 28, 30 requires a desired amount of friction to achieve sufficient traction, for example. Maintaining the desired coefficient of friction ensures consistent system performance. In each of the examples of Figures 2 and 3 the polymer material for the jacket 34 includes a friction stabilizer that facilitates maintaining a desired friction characteristic of at least an exterior surface on the jacket 34.

[00020] Figure 4 schematically illustrates an example passenger conveyor 40. In this example, a plurality of steps 42 move in a known manner to carry passengers between landings 44 and 46. A handrail 48 is provided for passengers to grab onto while traveling on the conveyor 40.

[00021] As shown in Figure 6, the handrail 48 includes a plurality of tension members 32 such as steel cords at least partially covered by a polymer jacket 34. The polymer jacket in this example establishes the gripping surface and the body of the handrail 48. The polymer jacket material includes at least one friction stabilizer that facilitates maintaining a desired friction characteristic of at least an exterior, gripping surface on the jacket 34.

[00022] The example of Figure 4 includes a drive arrangement 50 for propelling the steps 42 in a desired direction. A motor 52 rotates a drive sheave 54 to cause movement of a drive belt 56. As shown in Figure 5, the example drive belt 56 has a plurality of elongated cord tension members 32 covered by a jacket 34. The jacket material establishes teeth 57 that interact with a corresponding surface on the drive sheave 54. A step chain 58 (Figure 4) is engaged by teeth 59 on the drive belt 56 to cause the desired movement of the steps 42.

[00023] Desired amounts of friction are useful to ensure a desired interaction between the drive belt 56 on the one hand and the drive sheave 54 or the step chain 58 on the other hand. In this example, the drive belt 56 includes a polymer jacket material with at least one friction stabilizer that facilitates maintaining a desired friction characteristic of at least an exterior surface on the jacket 34.

[00024] When a metal is used for the any of the example tension members 32, the metal material may be uncoated, coated, or plated with a protective metal. For example, a base ferrous metal may be coated or plated with zinc, tin or copper.

[00025] Figure 7 schematically illustrates an example method at 60 of making an assembly such as an elevator load bearing member, a passenger conveyor handrail or a drive belt such as that used for a passenger conveyor. A friction stabilizer 62 is mixed with a supply of base polymer resin 64 in a master batch mixer 66.

[00026] The friction stabilizer 62 is one of melamine-based, phosphate-based or both. Example friction stabilizers include non-halogen containing melamine salts. Some example melamine salt friction enhancers include melamine cyanurate and melamine-phosphate. Those examples are useful with a thermoplastic polyurethane jacket material.

[00027] Other example friction stabilizers include organic phosphates. One such example comprises hydrocarbon phosphate. Such a friction stabilizer is useful with jacket materials that comprise elastomeric alloys such as melt-processible rubbers.

[00028] The amount of friction stabilizer can be varied to achieve target friction characteristics. In one example, the amount of friction stabilizer mixed with the base polymer resin in the master batch mixer 66 is between 20% and 50% by weight. The resulting master batch of mixed material in this example is then compounded with a base polymer material 68 in a jacket material mixer 70. The resulting jacket material after the mixing at 70 may contain up to 20% by weight of the friction stabilizer. One example includes from 0.2% to 20% by weight of the friction stabilizer in the jacket material. In one example, the resulting polymer material in the jacket material mixer 70 comprises between about 0.2% and about 10% by weight of the friction stabilizer.

[00029] Referring to Figure 7, the jacket material in this example is formed in a jacket forming station 72 such as a molding device to provide the desired geometry of the jacket. In the illustrated example, a plurality of spools 74 supply tension members 32 to the jacket forming station 72 where the jacket is molded onto at least one exterior surface of the tension members 32 resulting in the desired assembly. In the case of Figure 5, the resulting assembly is an elevator load bearing member 26.

[00030] Providing a melamine-based or phosphate -based friction stabilizer in an amount up to 20% by weight of the jacket polymer material increases the longevity of the friction characteristic of the jacket material. The friction stabilizer minimizes or prevents changes in the friction characteristic over time.

[00031] The presence of the friction stabilizer in at least one embodiment does not interfere with or adversely change other properties of the jacket material such as the flexibility of the base polymer material so that the jacket functions as desired for its particular application (e.g., is able to follow a guidance when the assembly comprises a passenger conveyor handrail, is able to transmit a sufficient drive force when the assembly comprises a drive member such as a belt or is able to wrap around sheaves and achieve sufficient traction for moving an elevator car when the assembly comprises an elevator load bearing member). Additionally, the ability to mold the jacket into a desired shape and to maintain good adhesion between the jacket 34 and the tension members 32 is not compromised. In fact, adhesion between the material of the jacket 34 and the tension members 32 is improved by the presence of the friction stabilizer in the jacket material.

[00032] The example friction stabilizers provide unexpectedly increased stability of friction characteristics of the jacket compared to a polymer jacket material with out one of them. In some examples, the adhesion strength is at least twice that which could be attained without the example friction stabilizers.

[00033] With the example friction stabilizers, the jacket of an assembly also has good thermal stability, hydrolytic stability, low hydrophilic characteristics and good compatibility to interact with other components such as an elevator sheave or a passenger conveyor step chain. The disclosed friction stabilizers also provide flame- retardant properties to the jacket material.

[00034] 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.