HK1109383B - Sheave and assembly for use in an elevator system - Google Patents

Description

Pulley and assembly for use in an elevator system

Technical Field

The present invention relates generally to elevator sheaves and, more particularly, to a unique belt guide surface configuration on an elevator sheave.

Background

Elevator systems have become widely recognized and employed. Typical arrangements include elevator cars that move between landings of a building, for example, to carry passengers or cargo to different heights within the building. As the car moves through the hoistway, the weight of the car is typically carried by a load bearing member, such as a rope or belt.

The load bearing member typically moves over at least one sheave as the car moves through the hoistway. In some examples, the sheave is a drive sheave that is coupled to a motorized mechanism to produce the desired movement of the elevator car. In other examples, the pulleys are passive, moving in response to movement of the load bearing member.

Although elevator sheaves have been used for a long time, there remains a need to improve their design to maximize the useful life of elevator system components such as load bearing members. For example, flat belts are typically subjected to overload stresses as the belt moves over the pulleys. Furthermore, since the axis of the elevator sheave is typically not precisely aligned with the axis of the support mechanism, the belt tends to move sideways along the sheave as the sheave rotates. While crowned pulley surfaces have been used to improve belt travel performance, crowned pulley surfaces have an associated disadvantage in that overload is induced in at least some of the cords in the central region of the belt. Coated steel belts with polymer coatings embedded in the steel wire ropes are particularly susceptible to such strains because these belts are designed to be very stiff in the axial direction. Uneven loading is caused by uneven stresses to which the ropes are subjected. Furthermore, conventional drum designs do not adequately accommodate travel performance in all situations.

There is therefore a need for an improved elevator sheave design to optimize the travel performance of the load bearing member, reducing the overall stress on the load bearing member. The present invention addresses the needs described while avoiding the shortcomings and drawbacks of the prior art.

Disclosure of Invention

An exemplary disclosed pulley for use in an elevator system has a belt guiding surface that minimizes the stresses introduced onto the load bearing member while maximizing travel capacity.

An example sheave includes a sheave body having a central axis about which the sheave rotates. The belt guiding surface includes a surface profile extending along at least a portion of the belt guiding surface. The surface profile is preferably defined by an equation that approximates an nth order polynomial of the distance from a selected reference point on the belt guiding surface, where n is a number greater than 2.

In one example, the belt guiding surface includes a central portion that is disposed parallel to a central axis of the pulley. The side portions flanking the central portion are preferably defined by an equation that approximates an nth order polynomial of distance from a selected reference point on the belt guiding surface, where n may be any number. The latter example is particularly useful for embodiments where the width of the load bearing member or belt is greater than half the width of the belt guiding surface.

In another example, the first side portions on both sides of the central portion are defined by an nth order polynomial. The second side portion extends from the first side portion toward an outer edge of the pulley. The second side portion in this example has a linear profile. Accordingly, a pulley designed according to this example provides three distinct regions on each side of a plane of symmetry passing through the center of the pulley.

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

Drawings

Figure 1 diagrammatically illustrates an elevator sheave assembly designed according to an embodiment of this invention.

Fig. 2 is a schematic partial cross-sectional view of the embodiment shown in fig. 1.

Figure 3 illustrates selected features of an embodiment of the invention.

Fig. 4 shows a further exemplary embodiment in a schematic manner.

Detailed Description

Fig. 1 diagrammatically shows an elevator sheave assembly 20 in which a sheave body 22 cooperates with a load bearing member 24. In one example, the load bearing member 24 is a coated steel strip. The term "drive belt" used in this specification should not be interpreted in the narrowest sense. Assemblies designed according to this invention may employ flat belts, coated steel belts, or other synthetic core belts employed in elevator systems. Accordingly, the term "drive belt" should be understood in a broad sense to include various configurations of load bearing members that may be employed in an elevator system.

The belt 24 is seated on a belt guiding surface 26, the belt guiding surface 26 extending between edges 28 and 30 of the illustrated pulley. Raised edges 28 and 30 are not included in another example sheave. The belt rides along the surface 26 as the pulley rotates about the central axis 34. The belt guiding surface preferably includes a surface profile along at least a portion of the width of the belt guiding surface. The surface profile preferably provides an at least partially drum-shaped surface along which the drive belt will ride on the pulleys. As can be appreciated from fig. 2, the belt guiding surface 26 includes a surface profile that extends in an axial direction and is at least partially convex, as shown in a radial cross-section of the pulley 22.

In one example, the surface profile is approximated by a polynomial equation of higher order. This equation can be expressed as y ═ xⁿWhere n is a number greater than 2, y is along an axis perpendicular to the pulley's rotational axis 34, and x is the distance from a reference point 40 on the belt guiding surface 26 measured in a direction parallel to the pulley's rotational axis. In the illustrated example, the reference point 40 is centrally located along the width of the belt guiding surface 26.

The example surface profile maximizes belt 24 travel performance on the belt guiding surface 26 while minimizing stresses induced on the belt by the profile shape. The example surface profile maintains sufficient spacing between the edges of the belt and the sides of the pulley, thus improving travel robustness.

In the example shown in fig. 3, wherein the width w of the belt 24 is greater than half the width c of the belt guiding surface 26, the surface profile preferably includes a flat central portion 42. In the illustrated example, each point along the central portion 42 is equidistant from the central axis 34. In other words, the example central portion 42 is preferably arranged generally parallel to the central axis 34 of the pulley 22.

The side portions 44 and 46 of the surface profile preferably extend between the edges 28 and 30 and the central portion 42 of the belt guiding surface, respectively. Each side portion 44 and 46 is preferably approximated by the equation y-xⁿWherein n is any number. In the example shown in fig. 3, n is 2. In one example, surface 26 has portions with different values of n. In another example, surface 26 has portions of different values of n on each side of its center, thus surface 26 is asymmetric about the center.

The drum design shown in figure 3 is preferably flat along the top portion of the drum, which is not accessible by the trailing edge of the belt 24. The width of the central portion 42 is preferably equal to the difference between the width c of the belt guiding surface 26 and the width w of the belt 24. The distance f shown in fig. 3 is preferably equal to w-c/2. Thus, whenever there is a space between the edge of the belt 24 and the edges 28 and 30 of the pulleys, respectively, neither belt edge will be located on the flat central portion 42.

Figure 4 shows another example in which the belt guiding surface 26 has a central portion 42 that is arranged parallel to the pulley axis of rotation 34. First side portions 44 and 46 extend away from opposite sides of central portion 42. In this example, first side portions 44 and 46 have a profile represented by a polynomial of order n, where n is any number. In one embodiment, n is greater than 2. In this example, the first side portions 44 and 46 do not extend all the way toward the ends 28 and 30 of the pulley.

The second side portions 48 and 50 extend between the first side portions 46 and 44, respectively, and the edge of the belt guiding surface 26. In this example, the second side portions 48 and 50 have a linear surface profile. In the illustrated example, the belt guiding surface 26 is symmetrical about a plane passing through the center of the pulley (i.e., a vertical plane extending into the page).

In the example shown in fig. 4, the second side portions 50 and 48 are preferably linear. Having a linear profile portion near the edge of the belt guiding surface 26 maintains the travel efficiency of a configuration having a curved surface extending between the central portion and the edge of the belt guiding surface 26. However, having a linear profile reduces the effect of the curved surface, which tends to compromise the useful life of the belt without restricting the efficiency of travel of the outermost portion of the belt guiding surface 26. This is due in part to the fact that the load carried by the belt portions riding on the outermost portions of the belt guiding surface 26 is significantly lower than the load carried by the belt portions riding on the central portion 42 and the regions of the first side portions 44 and 46 that are closer to the central portion.

In the drawings, the transitions between portions of the guide surface 26 are exaggerated to some extent for ease of illustration. In an example sheave, the guide surface is machined from a single piece of material and presents a continuous, uninterrupted surface across the entire sheave.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the foregoing disclosure will be readily apparent to those skilled in the art without departing from the spirit of the invention. The scope of legal protection given to this invention can only be determined by studying the following claims.

Claims (12)

1. A sheave for use in an elevator system, comprising:

a pulley body having a central axis and a drum-shaped belt guiding surface, the belt guiding surface including a surface profile extending axially along at least a portion of the belt guiding surface, the surface profile defined as an nth order polynomial of distance from a selected reference point on the belt guiding surface, where n is a number greater than 2,

wherein the surface profile is at least partially locally convex such that an edge of the surface profile is closer to the central axis than the reference point;

the belt guiding surface further comprises:

a central portion of the surface profile having a width and arranged parallel to the central axis; and

a first side portion on an opposite side of the central portion, the first side portion having a surface profile defined by the n-th order polynomial, and a second side portion extending from the first side portion toward an edge of the belt guiding surface, the second side portion having a linear profile.

2. The pulley according to claim 1, wherein the central portion is equally spaced from the central axis as a whole.

3. An assembly for use in an elevator system, comprising:

a drive belt having a width; and

a pulley supporting the belt and rotating about a central axis with movement of the belt, the pulley comprising a drum-shaped belt guiding surface having a width, the belt guiding surface extending between edges located on opposite sides of the pulley, the entire belt guiding surface being a single piece of material presenting a continuous, uninterrupted surface, the belt guiding surface having a central portion having a width, the belt guiding surface being arranged parallel to the central axis across the width so as to be at least partially equidistant between the central axis, and side portions extending from the central portion towards corresponding edges of the pulley, which are curved relative to the central axis,

a second side portion extending from the side portion toward the corresponding edge of the sheave, the second side portion having a linear surface profile.

4. The assembly of claim 3, wherein the width of the central portion of the belt guiding surface is approximately equal to twice the difference between the width of the belt and one-half of the width of the belt guiding surface.

5. The assembly of claim 3, wherein the central portion extends in opposite directions from a center point on the belt guiding surface, one half of the central portion being located on each side of the center point.

6. The assembly of claim 3, wherein the side portions of the belt guiding surface each have a curvature defined by an nth order polynomial of a selected reference point on the belt guiding surface.

7. The assembly of claim 3, wherein the entire central portion is equally spaced from the central axis, the distance between the central portion and the central axis being greater than the distance between the central axis and any point of the side portions.

8. The assembly of claim 3, wherein the width of the belt is greater than half the width of the belt guiding surface.

9. A sheave for use in an elevator system, comprising:

a pulley body having a central axis and a drum-shaped belt guiding surface, the drum-shaped belt guiding surface including a surface profile extending axially along at least a portion of the belt guiding surface, the surface profile having a central portion, a first side portion extending away from opposing edges of the central portion toward corresponding edges of the pulley, and a second side portion extending away from the first side portion toward the corresponding edges of the pulley, the central portion having a width, the surface profile being arranged parallel to the central axis of the pulley across the width, the first side portion having a curved profile, the second side portion having a linear profile.

10. The sheave of claim 9, wherein the entire central portion is equally spaced from a central axis of the sheave.

11. The sheave of claim 9, wherein the first side portion has a surface profile defined by an nth order polynomial of distance from a selected reference point on the belt guiding surface.

12. The sheave of claim 11, wherein n is a number greater than 2.