TECHNICAL FIELD

The present invention relates to a cable return pulley, and to a cable transportation system comprising such a pulley.

BACKGROUND ART

Known cable transportation systems comprise two turnaround stations, between which extends at least one haul cable. The turnaround stations each comprise a supporting structure; a pulley that rotates about an axis with respect to the supporting structure; and a drive member connected to the pulley by transmission means .

The turnaround station pulleys are of considerable size - roughly 4-6 metres in diameter - and therefore difficult to transport. So each pulley is normally divided into easy-to-transport sectors.

Document EP1584845, for example, describes a pulley comprising a polygonal hub that rotates about an axis; and a plurality of sectors, each with three coupling faces. One coupling face is coupled to the hub, and the other two are coupled to the adjacent sectors and extend radially with respect to the hub rotation axis.

Solutions of this type, however, call for a high degree of precision in fabricating the sectors. Any- machining errors may seriously compromise connection of the sectors to the hub and so make the pulley difficult to assemble. Very often, machining errors must be corrected on site, or even call for replacing the sector, with obvious drawbacks in terms of cost.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide a pulley that is cheap and easy to produce, and at the same time easier to assemble.

According to the present invention, there is provided a cable transportation system cable return pulley comprising :

- a hub, which is configured to rotate about an axis of rotation and has a plurality of lateral coupling sides lying along respective coplanar straight lines crosswise to the axis of rotation; and

a main body coupled to the hub and which comprises an annular seat for housing the cable; and a number of sectors equal to the number of lateral coupling sides of the hub; and wherein each sector is coupled to the hub and to the adjacent sectors solely along two of said straight lines.

The pulley is thus cheap and easy to produce, by fabrication of the sectors not requiring the same high degree of machining precision as for known pulleys . The solution claimed, in fact, requires only one dimensional check per sector, namely that the coupling edges of each sector extend along axes forming the same angle as that formed by the two straight lines along which the two respective lateral coupling sides lie. Such condition can be met easily, effectively and cheaply using a template .

Above all, the fact that the coupling edges of each sector lie along only two of the straight lines means the same sized hub can be used for pulleys of different diameters, with obvious economic advantages in terms of hub manufacture and storage. To produce pulleys of different diameters, larger sectors need simply be produced, with no alterations to the size or structure of the hub.

In a preferred embodiment of the cable return pulley, the straight lines are perpendicular.

The coupling edges of each sector are thus also perpendicular, making production and assembly easier.

In a preferred embodiment of the cable return pulley, the main body comprises at least two substantially identical sectors.

The sectors are thus easier to produce, due to the presence of sectors of substantially the same size.

In a preferred embodiment of the cable return pulley, all the sectors are substantially identical. The sectors can thus be mass-produced. Moreover, sectors of the same size are easier to transport and store than sectors of different sizes.

In a preferred embodiment of the cable return pulley, the sectors are four in number.

Dividing the main body into four sectors provides for optimum, even distribution of the component parts.

In a preferred embodiment of the cable return pulley, the annular seat has a bottom wall lined with a layer of elastomer material .

In this way, any outwardly non- flush joints between adjacent sectors (shown by the letter S in Figure 1) pose no problems, by being substantially cancelled out by an elastomer surface supporting the cable. This reduces production cost, as compared with that of known pulleys, by reducing the machining precision required for each sector. With this feature, in fact, machining errors in the order of millimetres can safely be tolerated.

In a preferred embodiment .of the cable return pulley, each sector has a curved outer edge in which the annular seat is formed; and an inner edge, which extends substantially along the two straight lines; the inner edge having at least one recess .

The at least one recess along the inner edge of each sector reduces the structural weight of the sector and makes it easier to handle and transport. Above all, the at least one recess reduces the amount of material needed to produce, and therefore the production cost of, each sector.

In a preferred embodiment of the cable return pulley, each sector has at least one hole.

Like the recess, the hole reduces the structural weight of each sector, making it easier to produce and assemble .

Another object of the invention is to provide a cable transportation system that is cheap and easy to produce .

According to the present invention, there is provided a cable transportation system as claimed in Claim 10.

BRIEF DESCRIPTION OF THE DRAWINGS

A non- limiting embodiment of the present invention will be described by way of example with reference to the attached drawings, in which :

Figure 1 shows a schematic underside view, with parts removed for clarity, of the cable return pulley according to the present invention;

Figure 2 shows a cross section, with parts removed for clarity, of a detail of the Figure 1 pulley;

Figure 3 shows an exploded underside view of the

Figure 1 pulley; Figure 4 shows a schematic underside view of a return pulley in accordance with a first variation of the present invention;

Figure 5 shows a schematic underside view of a return pulley in accordance with a second variation of the present invention;

Figure 6 shows a schematic underside view of a return pulley in accordance with a third variation of the present invention;

Figure 7 shows a schematic underside view of a return pulley in accordance with a fourth variation of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in Figure 1 indicates a cable return pulley of a cable transportation system (not shown in the drawings for the sake of simplicity) . Return pulley 1 may be either a drive pulley, or an idle pulley rotated by the cable .

Pulley 1 is designed to rotate about an axis of rotation A, and is driven by a drive member 2 (of which only the shaft is shown in the drawings) connected to pulley 1 by transmission means.

More specifically, pulley 1 comprises a hub 3 coupled to drive member 3; and a main body 4 fixed to hub 3.

Main body 4 comprises a substantially circular outer edge 5 having a seat 6 (Figure 2) configured to house the cable (not shown in the drawings) .

As shown in Figure 2 , seat 6 comprises a bottom wall 7 and two lateral walls 8. Bottom wall 7 is lined with a layer 9 of elastomer material, preferably natural rubber. And layer 9 of elastomer material has a face 10 not contacting lateral walls 8 or bottom wall 7.

Face 10 of layer 9 preferably has a groove 11 for housing the cable (not shown in the drawings) .

As shown in Figures 1 and 3, hub 3 is coupled to the shaft of drive member 2, and is designed to rotate about axis of rotation A.

Preferably, hub 3 is substantially in the form of a square cross, and has four identical lateral coupling sides 14, which are coupled to main body 4 in use.

Lateral coupling sides 14 lie along respective coplanar straight lines a, Jb, c, d crosswise to axis of rotation A.

In the non- limiting example in Figures 1, 2 and 3, straight lines a, b, c, d are perpendicular.

Each lateral coupling side 14 preferably has a coupling flange 15.

Main body 4 comprises a plurality of sectors 20 coupled to one another.

In the non- limiting example described and shown herein, sectors 20 are four in number and substantially identical.

Each sector 20 has a curved outer edge 21, in which cable seat 6 is formed; and an inner edge 22.

Each sector 20 preferably has at least one hole 23; and two recesses 24 located along inner edge 22. Hole 23 and recesses 24 reduce the structural weight of each sector 20, making it easier to handle and transport, and cheaper to produce .

As shown in Figure 1, when sectors 20 are coupled to one another and to hub 3, hub 3 and recesses 24 in sectors 20 form four openings 25 in pulley 1, each located substantially in the centre of a respective quadrant of pulley 1.

Preferably, openings 25 are substantially right- triangle-shaped with rounded vertices.

With particular reference to Figure 3 , inner edge 22 has a first contact portion 28, a second contact portion 29, and a third contact portion 30. Preferably, first contact portion 28 and second contact portion 29 are separated by a first recess 24, and second contact portion 29 and third contact portion 30 are separated by a second recess 24.

First contact portion 28 and second contact portion 29 of inner edge 22 are aligned along the same axis D, and third contact portion 30 extends along an axis E. Axis D and axis E form an angle substantially equal to that formed by the straight lines along which lie the adjacent lateral coupling sides to which sector 20 is to be coupled. In the non- limiting example in Figures 1, 2 and 3 , the straight lines along which lie the lateral coupling sides of hub 3 being perpendicular, axis D and axis E are also perpendicular.

Each contact portion 28, 29, 30 has a respective coupling flange 31, 32, 33.

In actual use, coupling flange 31 is coupled to coupling flange 33 of the adjacent sector 20; coupling flange 32 is coupled to respective coupling flange 15 of hub 3; and coupling flange 33 is coupled to coupling flange 31 of the adjacent sector 20.

Coupling flanges 31, 32, 33 and 15 are preferably coupled by bolts (not shown in the drawings) .

In a variation not shown, the inner edge has no recesses, so therefore has only two contact portions, which in use extend along the two straight lines along which the respective lateral coupling sides lie.

Figure 4 shows a cable return pulley 1 in accordance with a second embodiment of the present invention, in which hub 3 has a substantially rectangular cross section, and four lateral coupling sides lying along respective coplanar straight lines a, b, c, d crosswise to axis of rotation A; and main body 4 comprises two pairs of identical sectors 20.

Figure 5 shows a cable return pulley 1 in accordance with a third embodiment of the present invention, in which hub 3 has a substantially equilateral-triangle-shaped cross section, and three lateral coupling sides lying along respective coplanar straight lines a, b, c crosswise to axis of rotation A; and main body 4 comprises three substantially identical sectors 20.

Figure 6 shows a cable return pulley 1 in accordance with a fourth embodiment of the present invention, in which hub 3 has a substantially regular- pentagon-shaped cross section, and five lateral coupling sides lying along respective coplanar straight lines a, b, c, d, e crosswise to axis of rotation A; and main body 4 comprises five substantially identical sectors 20.

Figure 7 shows a cable return pulley 1 in accordance with a fifth embodiment of the present invention, in which hub 3 has a substantially regular- hexagon- shaped cross section, and six lateral coupling sides lying along respective coplanar straight lines a, b, c, d, e, f crosswise to axis of rotation A; and main body 4 comprises six substantially identical sectors 20.

It is understood that the hub may have a polygonal cross section with any number of sides. The main body comprises as many sectors as the sides of the hub. When the hub cross section is in the form of an equilateral polygon, the sectors are identical; whereas, in the case of a non-equilateral polygon, the sectors differ in shape and size according to the size and location of the sides of the polygon.

Clearly, changes may be made to the pulley and system as described herein without, however, departing from the scope of the accompanying Claims.