Metallic cable and method and apparatus for making same

A metallic cable comprises a strand of identical helical shaped filaments positioned beside and against each other such that each filament of the strand is in line contact with at least one other filament of the strand. The helixes of the filaments of the strand are sloped in a first direction. A single filament is twisted with the strand in a direction opposite to said first direction. An apparatus and a method for manufacturing the metallic cable are also disclosed.

BACKGROUND OF THE INVENTION 
The present invention relates generally to metallic cables, and more 
particularly to metallic cables that are useful for reinforcing 
elastomeric articles such as tires, hoses and belts. A method and 
apparatus for manufacturing a metallic cable according to the invention 
are also disclosed. 
One of the problems that may be encountered in elastomeric articles 
reinforced with metallic cables is the propagation of corrosion along the 
length of the cable in the event that the article is cut or torn so that 
the cable is exposed. One approach to solving the problem of corrosion 
propagation has been to make a cable very compact with no interstices 
between the filaments and strands of the cable, therefore leaving no 
pathway along which corrosion may spread. A second approach has been to 
make a cable with a very open construction, such that the elastomeric 
material in which the cable is embedded can penetrate the cable and 
substantially surround each individual filament. The present invention is 
concerned with the latter approach.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, there is shown a side elevation view of a metallic 
cable 10 in accordance with the invention. The cable 10 comprises a 
plurality of identical helically shaped untwisted filaments 11,12,13 
positioned beside and against each other such that each filament is in 
line contact with at least one other of the untwisted filaments. The 
helixes of the plurality of filaments are twisted in a given direction, 
depending upon the wishes of the engineer designing the elastomeric 
article which will be reinforced by the elastomeric cable. 
As used herein, a filament refers to an individual metallic wire; a 
"strand" refers to a group of filaments combined together to form a unit; 
and a "cable" refers to a structure comprising two or more strands, or a 
combination of at least one strand with at least one filament. The 
plurality of untwisted filaments 11,12,13 may be properly referred to as a 
strand. While three untwisted filaments are shown in FIGS. 1 to 6, it is 
understood that two or more untwisted filaments may be used in a metallic 
cable according to the invention. 
A single filament 14 is twisted with the plurality of filaments 11,12,13 in 
a direction that is opposite to the direction of the helixes of the 
plurality of filaments. 
As used herein, the direction of twist, lay, or a helix refers to the 
direction of slope of the spirals of a strand or filament when a cable is 
held vertically. If the slope of the spirals conform in direction to the 
slope of the letter "S", then the twist is called "S" or "left hand". If 
the slope of the spirals conform to the slope of the letter "Z", then the 
twist is called "Z" or "right-hand". "Lay length" is the axial distance 
required for a filament or strand to make one 360 degree revolution in a 
strand or cable. "Pitch length" is the axial distance required for a 
helically disposed filament to make one 360 degree revolution. 
Put another way, a metallic cable according to the invention comprises a 
strand of identical helical shaped untwisted filaments 11,12,13 positioned 
beside and against each other such that each filament is in line contact 
with at least one other filament of said strand, the helixes of the 
filaments of said strand being sloped in a first direction, and a single 
filament 14 twisted with said strand in a direction opposite of said first 
direction. 
FIGS. 2 to 6, which are cross-sectional views of a cable according to the 
invention taken along lines 2--2 to 6--6, respectively of FIG. 1, 
illustrate the open structure of a cable according to the invention. This 
open structure allows each filament to be substantially surrounded by an 
elastomeric substance when the cable is embedded in an elastomeric article 
to provide reinforcement. A substantially thorough coating of each 
filament not only retards the spread of corrosion if the elastomeric 
article is damaged, but also acts as an insulation to retard fretting, or 
abrasion, between the filaments which could result in the breaking of 
filaments or the cable itself. Abrasion of metallic filaments against one 
another could also generate heat to weaken the adhesion of the surrounding 
elastomeric material to the filaments and the cable itself. 
The individual filaments of a cable according to the invention may have 
diameters in the range of 0.05 mm to 0.5 mm, and preferably in the range 
of 0.15 mm to 0.35 mm. Preferably, the single filament has the same 
diameter as the filaments of the plurality of filaments. 
The helixes formed by the plurality of filaments have a pitch length in the 
range of 5 mm to 30 mm, but preferably in the range of 12 mm to 18 mm. 
Preferably, the pitch length of the helixes of the plurality of filaments 
is equal to the lay length of the single filament twisted with the 
plurality of filaments. 
Another advantage of a metallic cable according to the invention is that it 
may be manufactured rapidly using a continuous operation, rather than 
partially forming the cable, storing it on a spool, then finishing the 
cable in a subsequent operation. 
Referring to FIGS. 7 and 8, there are shown schematic side views of two 
embodiments of an apparatus for manufacturing a metallic cable in 
accordance with the invention. The apparatus 20 illustrated in FIG. 7 will 
be described in detail, and then the distinguishing feature of the 
apparatus 50 illustrated in FIG. 8 will be pointed out. 
A first member of the cable making apparatus 20 of FIG. 7 comprises first 
and second coaxial and interconnected flyers 21,22 spaced apart with 
respect to their axis of rotation. The rotating flyers have hollow 
bearings 23,24 that are rotatably attached to a means for support 25,26 
that rest upon a base 27. A series of flyer pulleys 43,44,45,46 are 
disposed at, or near, the radially outer edges of the flyers. A pair of 
rotating sunken pulleys 29,30 are attached to the inside of the hollow 
bearing 23 of the first rotating flyer, and a pair of rotating sunken 
pulleys 31,32 are attached to the inside of the hollow bearing 24 of the 
second rotating flyer. The walls of the hollow bearings have passageways 
therethrough in the regions of the sunken rotating pulleys to allow 
filaments, strands, or a cable to pass from the interior to the exterior 
of the hollow bearings. The rotating sunken pulleys guide metallic 
filaments through the hollow bearings in directions towards or away from 
the radially outer periphery of the respective flyer. A means for 
rotating, such as an electric motor 33 connected to the bearing of one of 
the flyers by a combination of pulleys and a belt 34 causes the flyers to 
rotate about their mutual axis. 
A second member of the cable making apparatus comprises a non-rotating 
cradle 28 swingably suspended from the hollow bearings of the flyers, and 
a bobbin means 35 attached to the cradle for supplying a metallic filament 
36. While a single bobbin means is shown attached to the cradle in the 
drawing, it is understood that the number of bobbin means actually 
employed is dependent upon the particular cable construction that is to be 
manufactured. Although the bobbin means illustrated in the drawing has a 
vertically oriented axis of rotation, it is understood that the axis of 
rotation of the bobbin means may be horizontal and perpendicular to the 
axis of the flyers, without deviating from the invention. An idler roll 42 
may be attached to the cradle to guide filaments along the axis of 
rotation of the flyers. 
A third member of the cable making apparatus comprises a plurality of 
bobbin means 37,38,39 attached to a stand 40 that is disposed at the end 
of the first member of the cable making machine nearest to the first flyer 
21. The plurality of bobbin means supply a plurality of metallic 
filaments. While three bobbin means are shown attached to the stand in the 
drawing, it is understood that the number of bobbin means actually 
employed is dependent upon the particular cable construction that is to be 
manufactured. Although the plurality of bobbin means 37,38,39 illustrated 
in the drawing have vertically oriented axes of rotation, it is understood 
that the axes of rotation of the plurality of bobbin means may be 
horizontal and perpendicular to the axis of rotation of the flyers, 
without deviating from the invention. 
A forth member of the cable making machine comprises a means for 
permanently forming the plurality of metallic filaments, supplied by the 
plurality of bobbin means of the third member, into helixes. In the 
embodiment illustrated in FIG. 7, this fourth member comprises a plurality 
of kill rolls 41 attached to the non-rotating cradle 34. As used herein, 
"kill rolls" are understood to mean a series of freely rotating pulleys 
aligned in two parallel rows such that the geometric centers of the 
pulleys of one row are positioned midway between the geometric centers of 
the pulleys of the other row. The distance between the two rolls of 
pulleys is adjustable to permit the manufacturing of various cable 
constructions. The "kill-rolls" function is to mechanically deform the 
filaments of a strand or cable to permanently fix the positions of the 
filaments with respect to one another and relieve the stresses in the 
strand or cable. 
A fifth member of the cable making machine comprises a means for collecting 
a finished cable such as a driven spool (not shown) and a means for 
drawing the metallic filaments supplied by the bobbin means of the second 
and third members past, around and through the components of the cable 
making apparatus, such as a capstan (not shown). 
The cable making apparatus 50 illustrated in FIG. 8 is very similar to that 
illustrated in FIG. 7, with the exception that the fourth member, that is 
the means for permanently forming the plurality of filaments supplied by 
the bobbin means of the third member into helixes, is different. The 
fourth member of the cable making apparatus of FIG. 8 is a preformer 51 
disposed between the first member 52 and the third member 53. As used 
herein, a "preformer" is understood to mean a series of rollers or pins 
aligned in substantially the same manner as the kill-rolls 41 of the 
apparatus 20 of FIG. 1, such that the filaments of a strand passing 
through the preformer are permanently deformed into helixes. After forming 
the plurality of filaments into helixes the preformer guides them towards 
a sunken rotating pulley attached inside the hollow bearing of the first 
flyer. 
A metallic cable according to the invention may be manufactured by using a 
cable making apparatus of the type illustrated in FIG. 7. A plurality of 
metallic filaments are drawn from a plurality of bobbin means, 37,38,39 
false twisted, and formed into identical helixes of a given hand and 
pitch. The helixes are coaxial, and each filament is in line contact with 
at least one other filament. The plurality of metallic filaments are 
formed into helixes by guiding them around a rotating sunken pulley 29 
located in the hollow bearing 23 of the first rotating flyer 21 to impart 
a twist to the plurality of filaments in a first direction, then guiding 
the plurality of filaments towards the radially outer periphery of the 
first rotating flyer. A flyer pulley 43 of the first rotating flyer 
directs the plurlity of filaments towards the radially outer periphery of 
the second rotating flyer. A flyer pulley 44 of the second rotating flyer 
directs the plurality of filaments towards a rotating sunken pulley 31 
located in the hollow bearing of the second flyer. The plurality of 
filaments are guided next to and partially around the sunken rotating 
pulley 31 located in the hollow bearing of the second flyer to impart a 
second twist to the plurality of filaments in the first direction and 
direct the plurality of filaments through the hollow bearing of the second 
flyer in a direction going towards the first flyer. The plurality of 
filaments are passed through a series of kill rolls 41 to permanently form 
the filaments into helical configurations, then directed into the hollow 
bearing of the first flyer. This imparting of two twists into the 
plurality of filaments for each revolution of the flyers is referred to in 
the art as the "two for one twist principle". 
A single metallic filament 36 is drawn from a bobbin means 35 located on 
the non-rotating cradle of the cable-making apparatus. The single filament 
is guided through the hollow bearing 23 of the first flyer along a path 
parallel with the axis of rotation of the flyers. 
The plurality of metallic filaments and the single metallic filament are 
guided partially around a rotating sunken pulley 30 located in the hollow 
bearing of the first rotating flyer to twist the plurality of filaments 
with the single filament in a second direction that is opposite to the 
direction that the filaments of the plurality of filaments were twisted 
together. Therefore, the filaments of the plurality of filaments are 
partially untwisted from one another while retaining their helical 
configuration due to their passage through the series of kill rolls 41. At 
this point, the strand comprising the plurality of filaments and the 
single filaments are considered to be a cable. The cable is guided towards 
the radially outer periphery of the first rotating flyer and a flyer 
pulley 45 redirects the cable towards the radially outer periphery of the 
second rotating flyer. A flyer pulley 46 of the second rotating flyer 
directs the cable towards a rotating sunken pulley 32 located in the 
hollow bearing of the second flyer. 
The cable is guided partially around the rotating sunken pulley 32 located 
in the hollow bearing of the second flyer to further twist the plurality 
of filaments and the single filament in said second direction, 
simultaneously completely untwisting the filaments of the plurality of 
filaments from one another. The finished cable is then wrapped onto a 
means for collecting a finished cable, such as a driven spool (not shown). 
If a cable making apparatus 50 of the type illustrated in FIG. 8 is 
employed in the manufacture of a cable according to the invention, the 
plurality of cables supplied by a plurality of spools are formed into 
helixes by passing the plurality of filaments through a pre-forming 
apparatus 51 disposed between the bobbins of the third member 53 of the 
cable making apparatus and the first flyer 52. The plurality of filaments 
are then false twisted and twisted with a single filament, supplied by a 
bobbin means 54 attached to the non-rotating cradle, in the manner already 
described with the exception that no kill rolls are employed since the 
pre-former has already permanently formed the plurality of filaments into 
helixes. 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the invention, it will be apparent to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the spirit or scope of the invention.