CABLE WITH RADIAL ELEMENTS FOR CONVEYING MATERIALS BEHAVING AS FLUIDS THROUGH DUCTS

Abstract: An apparatus for conveying materials behaving substantially as fluids through ducts comprises a cable (11) having a plurality of radially protruding interspaced elements (14) moulded in such a way as to each incorporate the protruding ends of a rivet (15) radially passing through the cable so as to act, in cooperation with the swelling in the cable due to the penetration of the rivet, as a means for preventing the elements from sliding along the cable. The moulded elements are also provided, at the point of incorporation of the cable, with tapered extensions (16) so as to avoid sharp variations in the rigidity of the cable which could give rise to fatigue failure.

Description: There are known cables having a plurality of equally spaced apart radial elements secured thereto, which act as apparatus for conveying materials behaving substantially as fluids through ducts, in which the cable slides through a tube. The cables normally used are of the metal wire type and consequently have a relatively discontinuous surface, due to the fact that they are formed by twisting the strands together. Disks, or similar conveying elements, are moulded from plastic onto the cable and are therefore relatively firmly secured, especially if they have a relatively wide base, so as to cover a reasonably long section of the cable. However, the sudden change in the rigidity of the cable, caused by the presence of the disk, gives rise to problems in the case of cable paths with a large number of curves or with curves having a relatively small radius, as is often necessary in complex systems. Due to the intrinsic relative rigidity of metal wire cables it is, in fact, necessary for the curves in the system to be made with a relatively wide radius in order to avoid excessive bending stress. In cable conveying systems it would sometimes also be desirable to use radial elements which are asymmetrical or off centre with respect to the cable. This requirement however conflicts with the torsional resistance of the metal cable, which prevents the elements secured to it from moving along the path according to the curves and the positions of the return pulleys. All this makes it highly desirable to use textile cables made of high-strength materials, such as those made available by current technologies. Their flexibility, flexural and tensile strength and tendency to accept axial torsion prove, in fact, to be highly satisfactory. However, the relatively continuous surface of these cables makes the problem of firmly securing the disks, or the like, to the cable extremely difficult. Moreover, cables made of textile fibre tend to become frayed when their surface threads snap as a result of mechanical stress and especially wear. This problem can be eliminated by using a continuous sheath of flexible material, with high abrasion resistance, which surrounds the cable and also protects it from becoming impregnated with the conveyed material. The use of a sheathed cable makes it practically impossible to firmly secure the disks moulded onto it, or secured to it by conventional methods, with the result that up till now it has not been possible to currently and satisfactorily use these cables in conveying systems, despite the fact that their mechananical properties can be considered to be ideal for this use, especially in terms of smoothness and durability. In the known technique, various possible solutions have been proposed for securing the radial elements to the cable, such as for example the one described in the patent application EP-A-156 419 on behalf of the same Applicant. The known coupling means made to date however are still unsatisfactory since they are either unreliable or excessively complicated and therefore expensive to make, especially in view of the usually considerable length of the cable and of the large number of conveying elements secured to it and, moreover, the need to avoid introducing causes which could lead to fraying and snapping of the cable. The general scope of this invention is to obviate the aforementioned problems by providing a cable, in particular for a system of the type described above, in which the conveying elements can be reliably, inexpensively and rapidly secured to any type of cable whatsoever, especially cables made of textile fibre and sheathed. This scope is achieved according to the invention by providing an apparatus for conveying materials behaving substantially as fluids through ducts comprising a cable having a plurality of radially protruding interspaced elements which incorporate a section of the cable, characterized by the fact that said elements incorporate the protruding ends of a rivet passing radially through said section of the cable. The innovatory principles of this invention and its advantages with respect to the known technique will be more clearly evident from the following description of a possible exemplificative embodiment applying such principles, with reference to the accompanying drawings, in which: figure 1 shows a partial cross-sectional view of a cable according to the invention, inside a duct; figure 2 shows a cross-sectional view of a coupling between the cable and a conveying element made according to the invention; figure 3 shows a further cross-sectional view of a coupling between the cable and a conveying element made according to the invention. With reference to the figures, as shown in figure 1, a cable 11, sliding axially along a duct 10 of a known distribution system, is advantageously composed of a rope core 12, if necessary covered with a plastic sheath 13 made of non-toxic material (for example, polyester), so as to protect the fibres of the rope from abrasion caused by the conveyed material. The cable is provided with a plurality of interspaced conveying disks 14. As can be more clearly seen in figures 2 and 3, the disks 14 are moulded onto the cable so as to incorporate the rivets 15, which are inserted radially into the cable in such a way that their ends protrude by a sufficient length to prevent the disk from slipping. The disk is moulded, in correspondence with a rivet, so as to incorporate the entire corresponding portion of cable. Advantageously, the diameter of the rivet is sufficiently large, with respect to that of the cable, as to cause a local enlargement of the section of the cable, as shown in figure 2. In this way the rivet and the swelling in the cable co-operate to ensure that the moulded disk is reliably locked in place. Each disk 14 has two extensions 16 disposed substantially coaxial to the cable and covering a certain portion of the cable beyond the swelling. The extensions gradually taper off from the disk, so as obtain decreasing rigidity, thus preventing sudden changes in the rigidity of the cable between its free portions and the portions made rigid by the presence of the disk, and abnormal areas in which fatigue failure could occur. Moreover, the fibres of the cable affected by the penetration of the rivet are protected by the presence of the disk, which causes local stiffening of the cable thus avoiding stress, and especially fatigue stress, on this area of the cable where the fibres may have suffered damage due to penetration of the rivet. It is clear therefore that obtaining a cable, according to the invention, with conveying elements secured thereto (which are described herein as disks but which can obviously be of any desired shape, even off centre, in order to adapt to particular types of ducts) is quick and simple and consists of simply inserting rivets into the cable at regular intervals, for example by means of an automatic riveting machine, and of subsequently moulding the conveying elements, according to the known technique, so as to incorporate the rivet. Various types of materials can be used. For example, the rope core of the cable can be made of nylon, while the disks can be moulded from hard plastic. Despite the fact that it is extremely simple and inexpensive to make, the coupling thus obtained is able to withstand considerable stress, far higher than that normally encountered in a distribution system of the aforementioned type.

Claims: An apparatus for conveying materials behaving substantially as fluids through ducts comprising a cable having a plurality of radially protruding interspaced elements which incorporate a section of the cable, characterized by the fact that said elements incorporate the protruding ends of a rivet passing radially through said section of the cable. An apparatus as claimed in Claim 1, characterized by the fact that the diameter of the rivet serves to cause substantial swelling of the area of the cable penetrated. An apparatus as claimed in Claim 1, characterized by the fact that each radial element is moulded directly in place on the cable. An apparatus as claimed in Claim 1, characterized by the fact that the radial elements incorporate a section of the cable substantially greater than the area involved by the penetration of the rivet. An apparatus as claimed in Claim 1, characterized by the fact that the cable comprises a braided textile core covered with a continuous flexible sheath. An apparatus as claimed in Claim 1, characterized by the fact that said radial elements are provided with tapered extensions in their portion which incorporates the cable. An apparatus as claimed in Claim 1, characterized by the fact that said radial elements are in the form of a disk.

Inventors: PIROVANO, CAMILLO
Applicants: PIROVANO, CAMILLO
Application year: 1990
Main classification: B65G19
IPC codes: B65G19