FR2582372A1 - POLYETHYLENE PULLEYS FOR CABLES TRACTION TRANSPORT SYSTEMS - Google Patents

Abstract

THE INVENTION CONCERNS A PULLEY INTENDED TO SUPPORT A TENSIONED MOBILE CABLE, IN PARTICULAR FOR CABLE TRACTION TRANSPORT SYSTEMS. THE PULLEY IS IN POLYETHYLENE WITH VERY HIGH MOLECULAR MASS AND HAS A THROAT ANGLE CHOSEN DEPENDING ON THE FRICTION COEFFICIENT OF THIS MATERIAL, SO AS TO PREVENT THE CABLE 12 FROM GOING OUT OF THE THROAT OF THE LOW COENTROFFIC COEFFICIENT, THE COEFFICIENT OF THE MATERIAL. OF THIS MATERIAL ALLOWING TO MAKE A VERY SHALLOW THROAT. THE INVENTION FINDS ITS PARTICULAR APPLICATION IN GUIDED TRANSPORT SYSTEMS ON AIR CUSHIONS.

Description

POLYETHYLENE PULLEYS FOR TRANSPORT SYSTEMS

A TRACTION BY CABLES.

  The invention relates to pulleys cooperating with cables, as found in funicular-type transport systems. Transport systems are known in which a vehicle is towed by a cable. For long runs, the cable must be supported approximately every 30 meters by grooved pulleys. Because of the twisting of the cable and the pull on the cable, the cable tends to rise along the throat of the cable.

pulley, and to get out.

  Steel pulleys are usually used. They are cheap and durable, and their surface hard and smooth

  reduces the tendency of the cable to come out of the throat. How-

  these pulleys cause a very high wear of the cable.

  In addition, rubber or rubber-coated steel pulleys are expensive and less durable than corresponding steel pulleys, but they are more

soft for the cable.

  The invention therefore aims to create a pulley, which is simultaneously cheap and durable, and tends to keep the cable in the groove without causing wear

cable.

  To this end, the invention relates to very high molecular weight polyethylene pulleys whose groove angle is reduced to a minimum as a function of

  coefficient of friction of the molecular weight polyethylene

very high.

  The invention will be better understood with regard to the

  description and the accompanying drawings, which represent

  FIG. 1 is a perspective view showing the pulleys according to the invention used in a cable traction transport system; and

  Figure 2 is an end view of a pulley

  of the pulleys of Figure 1.

  Figure 1 shows a transport system in which a cab 10 is attached to a cable 12, and

  thereby moves along a smooth guideway 14.

  The cabin moves on an air cushion, created by levitation systems 16. Pulleys 18, arranged approximately every 30 meters along the track, provide retensioning of the cable. The transport system of Figure 1 is representative of the "OTIS SHUTTLE."

  Figure 2 shows a pulley 18 consisting essentially of

  of a disc having two faces 20 and 22, and a peripheral edge 24. The edge 24 is not flat, but it is formed so as to receive the cable 12. As the pulley must rotate in response to the movement of the cable, it is fixed via a suitable axle 26, journalled to a suitable retaining means 28

placed on the track.

  The outer edge 24 of the pulley is generally V-shaped, is concave towards the center of the pulley and forms an angle A with an imaginary surface 29 which represents the side of a low cylindrical disk.

  width from which the pulley is made by machining.

  The groove 24 has two symmetrical sides, forming

  two cheeks 30 and 32. In its summit, the throat takes suddenly

  the approximate shape of a quarter circle in the

  zone 34, with a radius corresponding to that of the cable 12.

  In the Otis Shuttle, it is common to have cable voltages of 45,000 Newtons and speeds of 10 meters per second. In addition, the path does not always follow a straight and flat trajectory. Although the pulleys

  may be inclined to provide lateral support

  than vertical to the cable on the ramps and in the

  curves, the cable will always tend to want to escape

per pulley.

  The coefficient of friction of the pulley and the angle of the groove are the key factors to maintain the cable in the groove. The higher the coefficient of friction, the easier it will be for the cable to exit

  the throat. In the same way, the cable will be all the easier

  out of the throat that the throat will be shallower. It can thus be seen that on the one hand the groove of the pulley must be as deep as possible, but, on the other hand, it has the disadvantage that, for a pulley of a given size, the cheeks 30 and 32 become all the more fragile as the throat is deeper. There is no such limit for the

  reduction of the coefficient of friction. To speak clearly

  the situation will be even better than the throat

is more slippery.

  The invention lies in the use of a poly-

  very high molecular weight ethylene, such as HOSTALEN GUR, for the material of the pulley; in the selection of a throat angle determined according to the material of the

  pulley; and in the unforeseen benefits of this combination

  characteristics when they are applied

  towed by a cable. The HOSTALEN GUR is available from American Hoechst Corporation, Plastics Division, 289 North Main Street, Leominster, Massachusetts 01453 ', and is described in detail in "Designing with the toughest of all plastics, Plastics Design Forum, May / June 1978:" As applied to the pulley according to the invention, the very high molecular weight polyethylene exhibits exceptional characteristics and is extraordinarily tenacious, and despite this, its paraffin-like surface resists abrasion of the cable and exerts it is easy to machine and has a low coefficient of friction.For this coefficient, the inventors have selected a throat angle related to the coefficient of friction so as to reduce the tendency to a minimum cable out

throat.

  The coefficient of friction of HOSTALEN GUR is about 0.1. The slope of the gorge (its tangent) must therefore

  it should also be at least 0.1 to give a critical angle

  than throat "A" of about 6 degrees. A security factor

  of 4 would lead to a throat angle of about 25 degrees.

  As mentioned above, an increase in the throat angle has the disadvantage of weakening the cheeks. With very high molecular weight polyethylene, a much smaller throat angle can be used, which leads to a smaller pulley

better mechanical resistance.

  Of course, the invention is not limited to the embodiment described above and shown, from which we can provide other modes and other embodiments, without departing

of the scope of the invention.

Claims (5)

  1. Pulley intended to support a moving cable (12) under tension, characterized in that the pulley is   made of very high molecular weight polyethylene.   2. Pulley according to claim 1, characterized in that it has a V-shaped groove, placed on its circumference and intended to receive the movable cable   (12), the angle of the groove (A) being chosen according to the coefficient   friction of molecular weight polyethylene very high.   3. Pulley according to claim 2, characterized in that the coefficient of friction of the very high molecular weight polyethylene is about 0.1,   the throat angle (A) being at least about 6 degrees.   4. Pulley according to claim 3, characterized in   the throat angle (A) is about 25 degrees.   5. A transport system comprising a cable traction vehicle (10) (12), characterized in that the cable (12) is supported by pulleys (18) as described in claim 1.