Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
2003-01-23
2004-05-18
Mayo, III, William H. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
C174S1170FF, C174S1170FF
Reexamination Certificate
active
06737586
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of manufacturing a flat electrical cable used e.g. for wiring public utility apparatuses, office automation apparatuses, electronic parts mounted in vehicles, and the like. In particular, the invention concerns devices used for the manufacture of such a flat cable. The invention further concerns a flat cable produced by such a manufacturing method or device.
2. Description of Background Information
FIGS. 1A and 1B
show how the prior art flat cables were manufactured in the past. According to a known method, a pair of insulator films
100
is prepared, so that each includes a base film
101
and an adhesive layer
102
, the adhesive layers facing each other. A plurality of rectangular conductors
103
are then arranged parallel to one another, and are flanked by the pair of insulator sheets
100
over their length. Subsequently, the insulator sheets
100
are thermally bonded e.g. by heated rollers.
In the above manufacturing method, the adhesive layers
102
of the insulator sheets
100
have to be sufficiently thick for each of the rectangular conductors
103
to be deeply embedded in the adhesive layers
102
, with the insulator sheets
100
firmly adhered and bonded. To obtain such a result, the base film
101
and adhesive layer
102
of each insulator sheet
100
must usually have an approximate thickness of 50 &mgr;m and 60 &mgr;m, respectively.
In such a construction, because the adhesive layers
102
must have substantial thickness, material costs are relatively high. In addition, as the adhesive layers
102
usually employ combustible agents, a flat cable including such a thick adhesive layer
102
raises the problem of inflammability.
Another flat cable manufacturing method is disclosed in Japanese Patent Application published under No.2000-502 833, according to which the rectangular conductors are initially arranged parallel to one another and sandwiched by two insulator sheets containing no adhesive layer, the insulator sheets being bonded to each other by ultrasonic welding.
However, ultrasonic welding alone does not allow the insulator sheets to be sufficiently well bonded, especially in the longitudinal zones extending between the rectangular conductors contained in the flat cable. When the insulator sheets are only loosely adhered, they may form air gaps therebetween, into which water or moisture from condensation may penetrate. Such a phenomenon creates a high risk of short-circuiting between the rectangular conductors.
In parallel, research is currently underway for a flat cable which requires a smaller space and weighs less. In this case too, the flat cable is manufactured by providing two insulator sheets, and interposing therebetween a number of mutually parallel rectangular conductor elements over the length of the sheets. According to one of the manufacturing methods, the insulator sheets flanking the conductor elements are bonded by ultrasonic welding.
According to one of the known ultrasonic welding methods, the side edges of insulator sheets which are positioned outside the parallel array of conductor elements are bonded intermittently by ultrasonic welding along the length direction of the sheets. However, in such a flat cable, electrically conductive material such as water tends to penetrate through non-bonded portions, thereby causing short circuits between the conductor elements.
The present invention aims at solving the problem caused by such an accident-prone flat cable, and provides a method for its manufacture, according to which the insulator sheets are intimately and firmly adhered through an adhesive layer, and, moreover, in which the adhesive layer can be made as thin as possible.
The invention also aims to provide a system for producing a flat cable, in which newly conceived ultrasonic welding units are used.
Further, the invention aims at manufacturing a flat cable, in which the conductor elements are efficiently prevented from short-circuiting.
SUMMARY OF THE INVENTION
To this end, there is provided a method of manufacturing a flat cable having a length and a width, the flat cable including first and second insulator sheets, and at least one adhesive layer interposed therebetween. The flat cable further includes a plurality of conductor elements arranged in parallel relation to one another over the length of the first and second insulator sheets. The method includes providing the adhesive layer on at least the first insulator sheet so as to face the second insulator sheet, interposing the conductor elements between the adhesive layer and the second insulator sheets, provisionally adhering the first and second insulator sheets including the conductor elements through the adhesive layer by means of heat pressing force exerted from outside the first and second insulator sheets, and bonding, by ultrasonic welding, the first and second insulator sheets through the zones extending along the length thereof and located outside the loci where the conductor elements are arranged.
Preferably, the adhesive-layer providing includes providing a first insulator sheet having a thickness of about 12 to about 300 &mgr;m and an adhesive layer having a thickness of about 1 to about 3 &mgr;m.
Preferably yet, the adhesive-layer providing includes providing an adhesive layer formed of the same type of material as that of the first insulator sheet, the adhesive layer containing no halogen-based flame-retardant.
Typically, the adhesive-layer providing includes providing the first and the second insulator sheets, so that one of them is at least about 1.5 times thicker than the other.
The invention also proposes a system for manufacturing a flat cable having a length and a width, the flat cable including first and second insulator sheets, and at least one adhesive layer interposed therebetween. The flat cable further includes a plurality of conductor elements arranged in parallel relation to one another over the length of the first and second insulator sheets. The system includes, along a production flow line from upstream to downstream, an adhesive application unit that provides the adhesive layer on at least the first insulator sheet so as to face the second insulator sheet, a conductor feed unit that interposes the conductor elements between the adhesive layer and the second insulator sheets, a provisional adhering unit that provisionally adheres the first and second insulator sheets including the conductor elements through the adhesive layer by a heat pressing force exerted from outside the first and second insulator sheets, and an ultrasonic welding unit that bonds the first and second insulator sheets through the zones extending along the length thereof and located outside the loci where the conductor elements are arranged.
Preferably, the above ultrasonic welding unit includes a horn that imparts ultrasonic oscillations, and an anvil located in opposition to the horn. The horn includes an oscillation-imparting portion, with which one of the first and second insulator sheets is placed into contact, and the anvil has a generally cylindrical form and includes an axis arranged perpendicularly to the production flow line, the anvil and being freely rotatable around the axis. The generally cylindrical body includes an outer cylindrical face including an appropriate number of arrays of protrusions, the protrusions being aligned in the circumferential direction of the outer cylindrical face and extending at a given interval therealong, such that the arrays of aligned protrusions can be placed into contact with the other of the first and second insulator sheets at both sides of each of the conductor elements. Preferably yet, the ultrasonic welding unit includes a horn that imparts ultrasonic oscillations, and an anvil located in opposition to the horn. The horn includes a plane, with which one of the first and second insulator sheets is placed into contact over the width hereof. The anvil has a generally cylindrical form that can rotate freely around an axis, the axis being pr
Fukumoto Koji
Inagaki Tomonori
Yamano Yoshiaki
Greenblum & Bernstein P.L.C.
Mayo III William H.
Sumitomo Wiring Systems Ltd.
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