Primary cable of ultra thin-wall for automotive service

Abstract: A primary cable of ultra-thin wall for automotive service characterized by a conductor geometrically formed by a copper wire nucleus joined in a bundle form of double torsion. This gives an exterior diameter that allows it to extrude with a concentric sheath of an insulator component of Vinyl polychloride free of lead. The manufacturing has three stages : stretching, in one-row or multi-row machines ; joint, in a joining machine, of simple or double torsion ; and extrusion with a standardized insulation thickness.

Description: BACKGROUND OF THE INVENTION The automotive industry oftenly requires the usage of new technologies not just in those of point but also in the ones that allow the constant innovation of its new aerodynamic models. Among this kind of necessary technological developments there are the processes focused on the manufacturing of the automotive primary cable of low tension. The quality, service, and prices must be competitive in world markets, this will only be achieved by staying in a changing area as the automotive industry does. The cable of ultra-thin wall is an example of these technological changes. Since they have competitive advantages in their manufacturing, with an adequate equipment, they offer a quality product with competitive prices. The cable has some advantages over a conventional cable, its objective is to lighten the vehicle weight. It increases the fuel efficiency and the production, it standardizes the numbers in the chemical-physical and mechanical tests, it reduces the wall thickness, it allows a bigger circuit integration in the harness offering more options of commodity and comfort, among others. Nowadays, most of the conductors used for a diameter smaller than 0,7mm (gauges smaller than 22) are made from a very refined electrolytic copper or alloys, which has a typical characteristic of elongation and switch intensity of 30 +% and 135,000 lb./pg. An inadequate intensity or rigidity conductor can produce stretching of the wire during the cut of circuits in the manufacturing of automotive harnesses. An inadequate rigidity conductor can provoke a loss of orientation of the wire during the last application. The intensity of the conductor is important in the extrusion operation and principally in the continuous crosslinking of the curing and insulation operations. The conventional materials of thermoplastic insulation of PVC that are now used, have a wire wall of 0,4mm (16 thousandth inch) thickness, to reduce these numbers, other PVC material or special mixtures are required. The reduced size wire needs improvements in the conductor manufacturing, more precision during the stage of extrusion of the insulation and improvements in the insulating material. The applicant has developed, for these new necessities, a primary cable of low tension. It is characterized by an ultra-thin insulation thickness. It is an automotive cable with a red copper conductor, smooth and annealed according to the ASTM B-3 norm, that permits to conduct electric current (ohmica) to any part of an automotive vehicle. DESCRIPTION OF THE INVENTION The invention is described above in a more detailed way according to the drawing of the fig. 1, making it more clear without restraining its reach, where the figure 2, is a sectional cut of cable in a transversal form. The principal characteristic of the cable of ultra-thin wall is the usage of constructions 11, symmetrical (7 wires) in each gauges from 0,7mm (22) to 1,2mm (18) AWL, as the joint cord and cable . It also uses a PVC ecological component (free of lead) PVL 185 LP (pm 2317) and resistant to the abrasion and pinch tests. It considerably reduces the indexes of leftovers for the usage of constructions 11, symmetrical of 7 wires, it permits more productivity because of the easy and quickly material handling, the wiring of the machine with just 7 wires, and the usage of ceramic in a standard measure. The innovating characteristic of the primary cable of ultra-thin wall 10 for automotive usage is that a geometrically formed conductor with copper wires 13, is used. They are joined in a bundle form that allows an excellent finish in the exterior diameter of the cord. As a result the cover 12 of an ecological insulation can be set in a concentric way, obtaining a standardization in the results of the chemical-physical test allowed by the insulating design. The process of the cable (cord) joining can be done in a joining machine of simple and double torsion, only if the same quality of joined cord is accomplished. There are other cords fabricated in 2 or more steps 15, (The step is the straight line to which a same wire of the cord appears in an analogous point, having gone over it in a helicoidal form to the cord ). The area is equal to π/4 x d 2 per number of wires MANUFACTURING The manufacture of the primary cable is made according to the following stages : STRETCHING.- With a diameter of 0,4mm (26 gauges) in a joint of seven wires a a cable of a diameter of 1,2mm (gauges 18) is fabricated, with a diameter of 0,3 mm (gauges 28) in a joining of seven wires, a cable of a diameter of 1,0 mm (19 gauges) is manufactured and with a diameter of 0,3mm (30 gauges) a cable of a diameter of 0,7 mm (22 gauges) is manufactured according to the American wire grange norm AWG. They are obtained by stretching in one-row or multi-row machines. These are the three wires required for this family of cables and the usage of individual wires is necessary for a better tension control in each of the wires. JOINT - In this second stage a joining machine of simple or double torsion is used (that permits the same quantity of joint cord) without a pre-twister and using geometrical constructions. EXTRUSION - Finally, as the third stage a cover or insulator of thermoplastic component of PVC (Vinyl polychloride) will be set in a concentric form so a thickness of standardized insulation can be achieved, and with this, results in the constant mechanical tests, resistant to the abrasion and pinched and ecological test, can be extruded in any extrusion machine for thermoplastics, achieving bigger indexes of production comparing them to a primary cable of asymmetrical construction. The cable ultra-thin wall is extruded in a linear speed of 1 000 metres per minute in an 1,2mm (18 gauges) AWG, as an average, in an extrusion machine of 10 mm capacity. Among the advantages that offers the primary cable of ultra-wall are: The usage of a substantially cylindrical conductor nucleus allows an excellent superficial finish, a bigger production in extrusion areas, more linear speeds and a reduction of leftovers for centering problems. As a result the harness weight is reduced in the assembling within other circuits to transmit the current to any part of the vehicle, the reason for what they have been made. This cable should be carefully fabricated so a control of equal tension when joining both wires is observed and each wire has to have the maximum electric resistance (ohmica) allowed, since it is the characteristic that rules the design of the cable. The cable of ultra-thin wall (reduced thickness) has some advantages over the other primary cables designed with asymmetrical constructions. Since a bigger standardization on the insulation thickness is achieved when the hollows 14 are reduced between every step of torsion of the filaments and with this, a standardization on the results of the chemical-physical and mechanical test is accomplished. These tests are obligatory because of its design, and the production indexes are bigger and the leftover indexes are smaller. This cable is used in the fabrication of an automotive harness where it will be exposed to work temperatures of -40°C to 105°C range of temperatures specified by the design of the electric automotive systems.

Claims: An ultra thin wall cable for automotive use comprising a smooth, annealed, substantially cylindrical conductor nucleus formed from a plurality of copper wires, each of the same quality, and an insulating PVC cover, wherein the cover is less than 0.4 mm thick, and the cable being fabricated by; i) stretching the copper wires through a drawing machine; ii) passing the wires through a single or double torsion joining machine; iii) positioning the cover concentrically around the nucleus; and iv) extruding the cover around the nucleus. An ultra thin wall cable according to Claim 1, wherein the cover is lead free, flame retardant, abrasion resistant, gasoline resistant and pinch resistant. An ultra thin wall cable according to Claim 1 or Claim 2, wherein the nucleus includes seven copper wires arranged symmetrically. An ultra thin wall cable according to any preceding claim, wherein the cable is able to operate over a temperature range of -40°C to 105°C. An ultra thin wall cable according to any preceding claims, where in the cable is fabricated without a pretwister prior to passing the wires through a torsion joining machine. An ultra thin wall cable according to any preceding claim, wherein the cover is extruded at a linear speed of 1000 metres per minute. An ultra thin wall cable according to any preceding claim, wherein the nucleus is annealed at 400°C in one or more steps.

Inventors: CORONA ARTEMIO M, GUTIERREZ CARLOS T, CORONA, ARTEMIO M., GUTIERREZ, CARLOS T., Corona, Artemio M., Serv. Condumex S.A. De C.V., Gutierrez, Carlos T., Serv. Condumex S.A. De C.V.
Applicants: SERVICIOS CONDUMEX SA, SERVICIOS CONDUMEX S.A. DE C.V.
Application year: 1998
Main classification: H01B7
IPC codes: H01B7