Improvements in or relating to the Manufacture of Insulating Tubing for Electric Conducting Wires.
Year: 1889

page_text: Date of Application, 6th Aug., 1889-Accepted, 26th Oct., 1889
COMPL LINE
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Improvements in or relating to the Manufacture of Insulating
Tubing for Electric Conducting Wires.
A communication from HENRY B. COBB, of Wilmington, County of New Castle,
State of Delaware, United States of America.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E., do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
My invention relates to the practice of a process and to the lead-press employed
therein for providing, in an expeditious, simple and comparatively inexpensive manner
metal-coated insulating tubing for electric conducting-wires, which tubing shall serve
as a means of affording a high degree of insulation to the wire, and of effectually
grounding induced currents, and which may, after undergoing the process of its
formation, hereinafter described, afford an equally effective means of insulation by
stripping it of its metallic casing, and thus adapt it for use where the metallic casing
is not required.
To practise my invention, I proceed in the manner hereinafter stated, employing to
that end suitable mechanical ineans such as that illustrated in the accompanying
drawings, in which—
Figure shows, in a diagrammatic view, a lead-press, represented in broken
sectional elevation as being fed, with the plastic (as soft rubber) tubing to be coated,
from a rotary pan having a central core, from which the tubing is unwound in feeding
it, and supporting a water-tank, a reel being also indicated, upon which to wind the
metal-coated tubing as it emerges from the press.
Figure 2 shows, in sectional elevation, means I may employ for vulcanizing the
coated plastic tubing, properly prepared for vulcanization, inside its metallic casing,
the said means comprising a vat containing melted paraffine heated to a vulcanizing
temperature and containing a reel having coiled upon it any desired continuous
length of the metal-coated plastic vulcanizable tubing filled with a fluid expansible
under the influence of heat.
Following is a description of the mechanism illustrated:
A (Figure 1) is a lead-press, having a metal column, r, supported on a suitable
base, (not shown) and surmounted by a metal block, r. Below the block, 1, and
secured to or cast with it, is a head, 2. B is a metal block having a chamber, q, in
one side, and semi-cylindrical channels, p, and o, in the same side and leading from
opposite directions into the chamber q; and around the chamber q is formed, in the
block B, a horizontal chamber, n, for steam. B is another block, having a
chamber, q', in one side, and semi-cylindrical channels, p and o₁, leading from
opposite directions, and, like the chanuels p and o, from the outer lateral sides of the
block, into the chamber q'; and a stoam-chamber,,is provided around the chamberq'.
A hollow plunger, C, extends from the side of the block B opposite that in which
he chamber q' is provided, the passage m in the plunger being cylindrical and
extending through it into the said chamber. The parts B and B are secured to the
ander side of the head and to each other in a inanner to cause the chambers q
nd q' and the channels p, p, and o o', to coincide, as shown. The upper end of the
assage m in the plunger is covered by a bridge, m', having openings, m², pre-
erably four in number and equidistant apart, between the edge of the bridge (which
may be integral with the block B) and edge of the mouth of the passage in, the
penings affording communication between the plunger-passage and chamber q'.
is a core-tube, tapering toward one end to the extremity thereof on its outer sido
nd tapering on the inside partway only toward the end, and cylindrical the rest of

page_text: the way, as shown. E is a die-tube, concave at one end and having a bore resembling
that in the tube D. The tubes D and E are inserted into the passage afforded by
the coincident channels o o' and p p¹, respectively from opposite ends thereof, and
meet at their respective tapering and concave extremities near the center of the
chamber qq, the tube D, thus entering the concave end of the tube E, and the bores
in both tubes coinciding. The tubes are not sufficiently long to extend to the outer
extremities of the passage provided to receive them, thereby leaving sufficient space
behind each, (and which is threaded, as shown) to receive hollow, externally threaded
plugs, D and E', which should flare, as represented, toward their outer ends.
F is a ram of ordinary construction in machines of the class to which the present
apparatus relates, and operated to be reciprocated vertically, preferably by hydraulic
pressure, in a manner that it is common to operate such machines; and G is a
receptacle, known as the "lead-cylinder" in lead-presses, the inside bottom of which
is synclinal in shape, and in the wall of the receptacle is a circumferential passage, l,
for steam. The receptacle G is supported on the ram F, in a position wherein the
plunger C coincides with the chamber-portion thereof.
The operation of the machine, as thus described, for the practice of that part of
my process which relates to the coating of the plastic vulcanizable tubing with metal,
thereby to prepare it for my improved manner of vulcanization, hereinafter explained;
is as follows:
The receptacle G is supplied with the substance of which to form the tubular
shield as molten glass, lead or other metal. As lead is the material I use for coating
the plastic tubing, the description will hereinafter be confined to the application of
lead, the operation of providing the coating with any other suitable substance in a
molten condition being, however, substantially the same.
The lead is introduced into the lead-cylinder in a molten state, after which it is
permitted to set for a few minutes (about four), when the ram is actuated to raise
the cylinder against the stationary plunger C, through which the pressure forces the
lead into the chamber q q'. The plastic tubing to be coated with the lead, and which
is properly supported, as by being wound, upon a suitable holder, hereinafter
described, is then inserted at one end through the core-tube D into the die-tube E,
and becomes coated with the lead forced by the pressure of the ram into the die-tube
around the plastic tubing, which is moved with its leaden shield out of the machine by
the pressure of the lead, the feeding of the tubing being controlled to correspond
with the speed of egress of the coated product by an operator at the holder
referred to.
When the plunger C reaches nearly to the bottom of the cylinder G, it compresses
the remnant of the contents of the cylinder into the form of the synclinal bottom of
the latter against the end of the plunger, as shown by the dotted lines at a, and
when the cylinder is lowered, inasmuch as the mass x not only sticks to the plunger
but is held by the core in the passage m, the cylinder may be entirely depleted of
its contents by withdrawing it from the plunger; and when, after replenishing the
cylinder, it is again raised for another operation, or to continue the operation, the
plunger, owing to its form will force out laterally all air in the cylinder, above the lead,
and thus prevent air from becoming mixed with the molten lead, which would
tend to produce flaws in the tubing.
As the metal-coated soft tubing emerges from the machine, it enters an inclined
trough, H, through which, a stream of cold water is constantly caused to flow, and
is thereby cooled to permit of its being handled to wind upon a reel, N, (Figure 2)
The advantage of having the mould stationary, instead of movable, as heretofore in
lead-presses, is due to the soft condition of the tubing to be coated, which would be
liable to break in feeding it to the mould if the latter were movable.
The holder I employ for the plastic tubing and from which to feed it to the lead
press, comprises a pivotally and horizontally supported pan, I, having a central core, I'
To adapt the holder to my purpose, I support upon the core a water-tank, K, having
a spout, k, containing a shut-off valve, k¹. The soft tubing, ready for vulcanization
by having mixed with its substance the proper proportion of sulphur, and which tubing

page_text: has previously been wound around the core, I', and should be filled with water con-
ficed in it by clamping the ends, or pinching them to cause them to stick together, is
connected, at the innermost end of the coil, to the spout, k, whence water is caused to
flow continuously through it. This flow of water tends to prevent injury to the
tubing from the heat of the molten lead in the chamber 7 q', if the feeding of the
tubing be stopped (as for recharging the chamber) in its passage through the machine,
and thus permits practically unlimited length of the tubing to be coated, and without
regard to the capacity of the receptacle G.
Water is a desirable medium for use in maintaining the tubing, during the metal-
coating operation, in a cool condition. Obviously, however, any other liquid or
aeriform fluid that would serve the purpose of water, forms an equivalent thereof;
and if air be the fluid employed, it is not absolutely necessary that mechanical means
be used to force it through the tubing, since, the ends of the latter, in its passage
through the lead-press, being open, the heat will produce the desired flow of air
through it and prevent burning of the tubing during the coating operation and
collapse thereof in cooling.
The product of the described operation, which is tubing of plastic vulcanizable
material, (particularly soft rubber) incased in a close-fitting metallic shield, protecting
the tubing from injury while in its soft condition, is then ready to be subjected to the
process of vulcanization, forming a part of my present invention, and which is
hereinafter described, the mechanism for carrying it out being shown in Figure 2
and described as follows:
L is a vat containing a liquid (preferably hot paraffine), capable of being heated
to the proper temperature for vulcanizing without sealing the receptacle in which
it is contained; and the vat is mounted on a suitable heater, M. The vessel L
may have a removable cover, as shown, and may also have a controllable opening,
common in such vessels, for regulating the temperature, or may be entirely open.
The lead-incased tubing which is wound on the reel N as it emerges from the
lead-press, in the manner herein before described, is, previous to its immersion in the
vat L, filled with water or air, preferably under pressure, when each end is effectually
plugged to confine the fluid contents.
The reel is then immersed in the vat L, the paraffine in which is heated to a
vulcanizing temperature, which is insufficient to soften the lead coating, but which
heats the air or water in the tubing, causing it to expand and exert a pressure from
within the metal tube; while at the same time the heat of the paraffine, and of the
contained fluid, vulcanizes the rubber, the process of vulcanization being necessarily
moro rapid than the process of compression. The metal tubing offers sufficient
resistance to permit the plastic tubing to be greatly compacted from within without
necessitating the use of any other counter-pressure, the pressure I employ, with air,
being about forty pounds, which is raised by the heat to about one hundred and forty
pounds, though it may be less or more. This is very important, as it serves to enable
me to use an open vessel, or one which may be readily opened, for the vulcanizing
bath, the advantage of which will presently appear. Instead of paraffine, or other
liquid, sand may be used, or any other medium capable of holding, in an open or
unsealed vessel, a vulcanizing temperature.
While I prefer to produce the metal-coated plastic tubing, for the vulcanizing
treatment set forth, in the manner herein before described, my improved manner of
vulcanization can be employed, as well, if the metal-coated tubing be otherwise
produced.
By this manner of vulcanizing, any degree of flexibility or pliability may be given
to the vulcanized tubing, and the process of vulcanization stopped almost instanta-
neously at any stage. Separate pieces of the plastic tubing may be introduced, at the
same time with the coil, into the bath to serve, on removal and inspection, to indicate
the condition of the coil, as to its valcanization.
When the desired condition is reached, and thus indicated, the coil may be imme-
diately removed and cooled with water, or otherwise, when, if the flexible metal

page_text: coating is to be left on the tubing, the product is completed and ready for market.
If an uncased tubing is required, the lead may be removed and used again, leaving a
vulcanized rubber product with a bore of practically uniform diameter, and walls of
any desired density and having any desired amount of flexibility, results in them-
selves heretofore unattained, except with much greater expense than is involved in
my method.
The amount of the vulcanized tubing produced in a single bath is limited only by
the cubic capacity of the latter. A single bath may contain several reels of the
tubing, and each may be given a different degree of flexibility and compactness, or
they may all, when finished, be substantially the samne in this regard, which is a very
valuable result of any method, unattainable by any other method with which I ain
acquainted.
My manner of practising the vulcanization is to be carefully distinguished from a
method of forming fabric-covered, vulcanized tubing, by coating the interior of the
tubular fabric with rubber combined with sulphur, filling the bore with water, and
subjecting it to a vulcanizing temperature in a closed or sealed vessel, presenting an
external pressure to the tube. Such a proco lure will not produce the result attained
by nine, because of the difficulty of regulating the temperature and pressure in the
vessel and in the bore, and the impossibility of testing the character of the product
before its removal from the vessel. Under any circumstances, in such a procedure,
the removal cannot take place without destroying the ability of the apparatus to
carry on the method of withdrawing the heat and pressure therein.
This is not my
process.
It is to be distinguished, also, from a process wherein a heating bath for solid
rubber is employed, in which no metal coating is necessary or desirable; the bath
containing sulphur for vulcanization (if desired, instead of combining the sulphur
with the rubber) and a metal mold being used, merely as a receptacle for the rubber
during vulcanization, and not to resist any pressure from the inside, nor to afford a
permanent coating therefor. It is to be distinguished from a process involving the
employment of inflexible metal tubing to receive the rubber, which, besides making it
impossible to vulcanize great lengths of rubber tubing, renders it difficult to obtain
any definite degree of flexibility in the rubber tubing, because of the impossibility of
access; and in this connection it may be said that, practically, the opportunity to
inspect the material undergoing treatment is of the highest advantage, whether
accurate theories as to the condition at a stated time are established or not.
What I clann as new and desire to secure by letters patent is-
1 The method of producing vulcanized gum tubing, which consists in incasing
plastic gun tube, prepared for vulcanization, in a flexible metal tube, introducing
and retaining an expansible fluid in the bore of the tube, and coiling and immersing
the whole in an open bath having a proper vulcanizing temperature, as set forth.
2-The method of producing vulcanized gum tubing, which consists in incasing
plastic gum tube, prepared for vulcanization, in a flexible metal tube, introducing
and retaining an expansible fluid in the bore of the tube, and coiling and immersing
the whole in a bath of paraffine, or similar oil, maintained at a vulcanizing heat, and
contained in an unsealed vessel, as set forth.
3-The method of producing flexible vulcanized gum tubing with a continuous
close coating of metal, which consists in forming a tube, of plastic gum containing a
vulcanizing substance, in a usual manner, covering the tube while soft with a con-
tinuous casing of flexible metal, and immersing the whole in an open bath having a
proper vulcanizing temperature, as set forth.
4-The method of producing flexible vulcanized gum tubing with a continuous
coating of metal, which consists in covering the formed plastic gum tube, having
mixed with its substance vulcanizing material, with a continuous casing of flexible
metal, introducing and confining an expansible fluid in the bore, and immersing a
coil of the tubing in an open bath having a vulcanizing temperature, as set forth.

page_text: 5. The method of coating the exterior surface of tubing formed of plastic material
and thereby preparing it for vulcanization, which consists in molding upon it a close-
fitting metal shield and passing a fluid through the tubing while the shield is
being formed thereon, substantially as described.
6 The method of coating with metal the exterior surface of tubing formed of
plastic material and thereby preparing it for vulcanization, which consists in melting
the metal, passing the tubing through a suitable die, forcing the metal into the die
around the tubing, and passing a suitable fluid through the tubing while the coating
is being formed thereon, substantially as described.
7-In a lead-press, the combination of a reciprocating lead cylinder, a stationary
hollow plunger in line with and above the lead-cylinder and a stationary mold above
the plunger and communicating therewith, substantially as and for the purpose set,
forth.
8-In a lead-press, the combination of a reciprocating lead-cylinder, having a
synclinal bottom, a stationary hollow plunger in line with and above the lead-
cylinder, and a stationary mold above the plunger and communicating therewith,
substantially as and for the purpose set forth.
9-In a lead-press, the combination of a reciprocating lead-cylinder, G, a stationary
hollow plunger, C, in line with and above the lead-cylinder, a stationary chamber q q',
above the hollow plunger and communicating therewith, tubes, D and E, loading
horizontally into the sides of the said chamber and coinciding at their bores near
the center thereof, the tube D extending into the adjacent end of the tube E, and
a bridge, m', in the chamber 7 q', over the opening in the plunger, substantially as
described.