Flat cable and modular rotary anvil to make same

#1. Field of the Invention

#The present invention pertains to flat cable and an apparatus for making flat cable. The invention more particularly concerns flat electrical cable with exposed conductors without adhesive residue and a modular rotary anvil which is used to manufacture the flat electrical cable.

#2. Discussion of the Background

#A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

#FIG. 1 is a perspective view of the flat cable of the present invention;

#FIG. 2 is a side-elevation view of the preferred apparatus for bonding of the flat cable;

#Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1 thereof which shows a finished flat conductor cable 10 of a preferred embodiment of the present invention. The flat cable 10 has an upper layer 20 and a lower layer 30 formed of an insulating material. In a preferred embodiment, polyester insulator is used, such as that having a thickness of 0.001 inches. However, thicker insulator materials may be used to provide stronger bonds, such as where the seams are narrow. Intermediate the upper and lower layers 20, 30 are conductors 40. The conductors 40 are made of individual strands of metallic material which lie substantially parallel to one and another along the length of the cable 10. In a preferred embodiment, the conductors are formed of annealed copper having a dead soft hardness rating. However, any other conductor may be used such as copper clad steel. Furthermore, the conductor can be replaced with a fiber optic cable. The conductors 40 are separated by seams 50. The seams 50 are formed by the continuous bonding between the upper layer 20 and the lower insulator layer 30. A plurality of parallel spaced-apart seams 50 run continuously along the length of the cable 10. In a preferred embodiment, the spacing between the plurality of conductors 40 comprises the seams 50. In other words, the width of each seam 50 approximately equals the space between the adjacent conductors 40. In such a construction, the conductors 40 are trapped in a pocket or encapsulated between the seams 50 and the upper and lower insulator layers 20, 30 to avoid any shorting between the parallel strands of conductors 40. In a preferred embodiment, the seams 50 are ultrasonically bonded, which will be discussed further below.

#The cable 10 includes a raised surface 25 or ribs above the conductors 40 on the upper layer 20 of the insulator. The raised surface 25 provides for a ribbed texture along the upper surface 20 of the cable 10 and reduces the surface area of the upper layer 20 so that less friction is created when the upper layer 20 rubs against another surface. In an embodiment where the flat cable 10 is wound in a spool, the noise of the surface of the upper layer 20 of the flat cable 10 rubbing against the lower layer 30 will be reduced due to the ribs 25. In addition, in another embodiment, the lower layer 30 of the flat cable 10 has a pattern 35 adhered thereto. The pattern 35 acts to reduce the surface area of the most extraneous portions of the lower layer 30 in order to further reduce friction and noise of the lower layer 30 rubbing against another surface.

#In the preferred method of assembling the flat cable 10, the bonding of the upper and lower layers 20, 30 occurs only at the plurality of seams 50 and no bonding of the upper layer 20 or lower layer 30 occurs to the conductors 40. In such an arrangement, the conductors 40 are bounded on each side by the seams 50 but are loose in the compartment formed by the upper and lower layers 20, 30 which are not bonded in the area along the length of the conductor 40. This arrangement provides an advantage in that when the end of the cable 10 is stripped and the conductors 40 are exposed, the exposure operation is simplified in that there is no bonding between the conductors 40 and the upper or lower layers 20, 30. Therefore, there is no residue on the conductors 40 and cleaning of the conductors is not required in order to provide the desired level of conductivity. An edge 15 of the flat cable 10 is also bonded and has a continuous seam such as provided by an ultrasonic weld. This edge 15 may be provided by cutting the flat cable 10 via slitting station 89 shown in FIG. 4. The edge 15 produced by cutting is a smooth edge or surface. The smooth surface of the edge 15 results in a flat electrical cable which provides for quiet operation during use in a clockspring, even though the edge 15 contacts sound damping material of the clockspring housing.