GB2173830A

GB2173830A - Composite cable for cable- drawn transportation system

Info

Publication number: GB2173830A
Application number: GB08608769A
Authority: GB
Inventors: William H Gibson
Original assignee: OTTIS ELEVATOR Co; Otis Elevator Co
Current assignee: OTTIS ELEVATOR Co; Otis Elevator Co
Priority date: 1985-04-15
Filing date: 1986-04-10
Publication date: 1986-10-22
Also published as: AU5540086A; DE3611259A1; GB8608769D0; ZA862009B; FR2580357A1

Abstract

The inner strands (21-27) of a cable are a lightweight, high-strength material, such as KEVLAR (Registered Trade Mark). The outer strands (28-39), which completely shield the inner strands (21-27) against abrasion from external sources, are conventional steel strands. Weight savings are thus realized, and efficiency increased. <IMAGE>

Description

SPECIFICATION Composite cable for cable-drawn transportation system The invention relates to cables, otherwise known as wire ropes, especially as applied to cable-drawn vehicles.

Transportation systems are known in which a vehicle is drawn by a cable. Sometimes referred to as funicular transportation systems, modern cable-drawn systems, such as the Otis Shuttle, are capable of velocities of up to 10 meters per second. Consequently, such systems are being considered for longer and longer runs. As run length increases, cable weight increases. Required cable tension increases in response to the cable weight increase, which requires a stronger, and bulkier, cable. For runs approaching 2 kilometers, a closed loop cable having a total length of 4 kilometers may reduce system efficiency to as low as 50 percent. Thus, the practical length of a cable-drawn transportation system is largely limited by the cable.

Therefore, it is an object of this invention to provide a low weight cable, thereby reducing efficiency losses.

According to the invention, the inner strands of a cable are a lightweight, high-strength material, such as KEVLAR . The outer strands, which completely shield the inner strands against abrasion from external sources, are conventional steel strands. Weight savings are thus realized, and efficiency increased.

In a complex cable layup, such as 7X19, meaning 7 bundles of 19 strands each, since the central bundle is surrounded by the other six bundles, it can have all KEVLAR strands so that even greater weight savings can be realized.

Other objects, features and advantages of the invention will become more apparent in light of the following description by way of example, of a preferred embodiment thereof with reference to the accompanying drawings wherein: Figure 1 is a perspective view of a cabledrawn transportation system wherein the cable of this invention may be used; Figure 2 is a cross section of a nineteen strand cable bundle utilizing the invention; and Figure 3 is a cross section of a seven bundle cable utilizing the invention.

Fig. 1 shows a transportation system wherein a car 10 is attached to a cable 12 and moved thereby along a smooth track 14 on a cushion of air as provided by hoverpads 16. Sheaves 18, are disposed every thirty meters, or so, along the track to accommodate cable sag.

The path described by the track is not always straight and level. It may turn to the left or right, and may incline. Although the sheaves may be oriented so as to provide both lateral and vertical support to the cable in such instances, the cable is under great tension, on the order of 45,000 Newtons, and may climb or jump out of a sheave. While for any particular sheave this may or may not result in degraded system operation, once the cable has jumped a sheave it is subject to abrasion by track components such as sheave supports, power rails, and the like. Repiacing an abraded cable would result in an undesirable system shutdown. Normally, the cable is one of the longer-lived components of the system.

Fig. 2 shows a cable bundle 20 of nineteen strands 21-39. A typical cable, known as 7X 19 cable is made up of seven such bundles, as shown in Fig. 3.

In each bundle 20, the strands are twisted.

Certain strands, namely the twelve outer strands 28-39 are always on the outside of the bundle. Other strands, namely the seven inner strands 21-27, are always at the inside of the bundle. In other words, the inner strands 21-27 are completely covered by the outer strands 28-39 and protected thereby against abrasion from external sources.

To reduce cable weight, while maintaining abrasion-resistance, the inner strands 21-27 of each bundle 20 are a lightweight, highstrength material such as KEVLAR, and the outer strands 28-39 of each bundle 20 are conventional steel strands. Although the KEVLAR inner strands 21-27 are almost as stiff and even stronger than the steel outer strands 28-39, they are not abrasion-resistant and would not fare well in the event that the cable jumped a sheave.

A composite cable made of such bundles 20 would provide a substantial weight savings over a steel cable of the same dimension, and a commensurate increase in efficiency. Additionally, the composite cable 20 would typically be stronger than its steel counterpart. Of course, it would also be more expensive, but the cable is a relatively low cost item in the context of the entire transportation system.

Such a cable as disclosed herein is readily manufactured using standard wire-rope manufacturing machinery by simply substituting KEVLAR strand stock at the appropriate feed stations. Carbon fiber strands could also be used.

Referring again to Fig. 3, it will be noted that the central bundle 20' is an inside bundle, while the other six bundles 20 are outside bundles. Additional weight savings could be realized by making the central bundle 20' completely from (nineteen) KEVLAR strands.

It should be understood that the invention has been described with respect to a particular embodiment thereof, and that various changes and additions could be made therein and thereto without departing from the spirit and scope of the invention. Particularly with regard to wire rope, there are many other lay ups, such as 1X19, 7X7, and 19X17 which would benefit from the teachings of this invention.

Claims

1. A twisted cable characterized by inner strands of lightweight, high-strength material and outer strands of steel.

2. A twisted cable according to claim 1 wherein the inner strands are KEVLAR.

3. A twisted cable according to claim 1 or 2 comprising seven bundles of nineteen strands each, each bundle characterized by seven inner strands and twelve outer strands.

4. A twisted cable according to claim 1 or 2 comprising a central bundle of nineteen inner strands, and six outer bundles of nineteen strands each, each outer bundle characterized by seven inner strands and twelve outer strands.

5. A twisted cable substantially as described with reference to the accompanying drawings.

6. A transportation system comprising a vehicle attached to and drawn by a cable as claimed in any of the preceding claims.