Process and device for vulcanizing with continuity elastomeric material hoses

Elastomeric hoses are vulcanized by a process wherein the outer surface layer (sheath) is completely vulcanized while the remainder remains unvulcanized. The surface layer and part of the resistant structure are maintained in an elastic elongated state while vulcanizing the remainder of the hose. An apparatus for vulcanizing the hose in accordance with the process is disclosed.

This invention relates to a process for vulcanizing elastomeric hoses and, 
in particular, hoses having an elastomeric wall with a reinforcing 
structure embedded in the wall. The present invention also relates to a 
device for vulcanizing continuous lengths of elastomeric hoses. 
Various processes are known for continuously vulcanizing elastomeric hoses. 
These known processes can be grouped into two groups. 
In accordance with a first group of known processes for continuously 
vulcanizing elastomeric hoses, the external uncured elastomeric surface of 
the hose is covered with a sheath, generally of lead, and the hose is 
vulcanized while covered with the sheath by passing it through an 
autoclave into which there is introduced a pressurized fluid. The sheath 
is removed after the hose has been vulcanized. 
The processes involved in the first group produce theoretically, perfectly 
shaped hoses, which have an outer surface that is perfectly smooth and 
compact, i.e. free from any porosity. But, the production rate from these 
processes is extremely low, owing at least partially to the time required 
for forming the sheath around the hose. In the second place, it is 
practically impossible to obtain a perfect surface on the outside of the 
hose because of the inevitable scorings or incisions made by the knife or 
other sharp instrument used to remove the sheath. In the third place, the 
cost of vulcanizing the hoses is extremely high because of the two steps 
of forming the sheath and of removing it. 
In a second group of known continuous processes for vulcanizing hoses, the 
uncured elastomeric hoses are passed through a bath of hot liquid, for 
example, melted salts, to provide the necessary heat for vulcanizing the 
hose. 
The processes of the second group produce hoses at a high production rate 
but have the serious drawback that a large percentage of the hoses are 
porous. 
Moreover, none of the known processes produces hoses having a perfectly 
smooth inner bore. 
An object of the invention is to provide a process for vulcanizing an 
elastomeric hose which is devoid of the foregoing disadvantages. Another 
object of the invention is to provide a process for vulcanizing lengths of 
an elastomeric hose continuously. Still another object of the invention is 
to provide an improved process for vulcanizing at a high production rate 
an elastomeric hose having a substantially smooth external surface with a 
minimum risk of the smooth surface becoming damaged during the 
vulcanization process. A further object of the invention is to provide a 
vulcanized elastomeric hose having a substantially smooth surface about 
the bore through the hose and a process for making such a hose.

The foregoing objects and others are accomplished in accordance with this 
invention, generally speaking, by providing a process for vulcanizing an 
uncured elastomeric hose continuously and for embedding in the hose wall a 
stress resistant insert member wherein mechanical pressure is applied to 
the uncured external wall of the hose while the hose is heated to 
vulcanize the elastomeric component to avoid change in cross-section of 
the bore in the hose during vulcanization. The invention also provides a 
device for vulcanizing an elastomeric hose continuously having arranged in 
series in the direction in which the hose is advanced a first tubular 
member having a cross-section larger than the cross-section of the hose to 
be vulcanized and provided with a heating unit for heating the hose, a 
second tubular member having a heater and connected to the downstream end 
of the first tubular member, the cross-section of the bore of the second 
tubular member being substantially equal to the outer cross-sectional 
dimension of the hose and smaller than the cross-section of the hose of 
the first tubular member whereby the external surface of the hose is 
heated by the first and second tubular members of the device as the hose 
is passed therethrough and the external surface of the hose is compressed 
by the second tubular member, a third tubular member connected to the 
downstream end of the second tubular member having means for heating the 
surface of the hose about the bore and a draft gear disposed downstream of 
the third tubular member which draws the hose through the three tubular 
members. 
In its broader aspects, the invention contemplates continuously vulcanizing 
an elastomeric hose by a process wherein only the longitudinal stress 
resistant structure of the hose is elastically elongated while mechanical 
pressure and heat are applied through the external surface of the hose to 
vulcanize the elastomeric material of the hose. 
According to a preferred embodiment of the process of the present 
invention, the outer surface layer of the hose, is first completely 
vulcanized while maintaining uncured, the remaining elastomeric material 
of the hose. The vulcanization of the outer surface of the hose is 
achieved by applying mechanical pressure to the external hose surface 
while heating through its outer surface. 
In this way, the dimensions of the external surface of the hose are 
established and a smooth and compact external surface is obtained. 
In a second step of the vulcanizing process, the already vulcanized outer 
surface of the hose is subjected to elastic elongation and the same 
applies to the longitudinal component of the stress resistant structure of 
the hose by simultaneously providing heat to the hose through the outer 
hose surface. 
During this step, because of the elastic elongation of the outer surface 
layer of the hose, mechanical pressure is exerted over the elastomeric 
material of the hose that is still in its uncured state, and as a result, 
during vulcanization of the remaining part of the elastomeric material 
forming the hose, no porosity forms in the walls of the hose. 
In FIG. 1, a device for vulcanizing uncured elastomeric hoses according to 
the process of the invention is shown. 
As can be seen in FIG. 1, the device comprises a series of three tubular 
bodies, a first tubular body 1, a second tubular body 2 and a third 
tubular body 3, connected end-to-end in series. 
Upstream of the first tubular body, i.e. to the left side of the tubular 
body 1 as shown in FIG. 1, a frusto-conically shaped coupling member 4 is 
connected to tubular body 1 at its smaller base. A chamber 5 disposed in 
frusto-conical member 4 contains a lubricating oil adjacent to the larger 
base. 
A housing 6 is disposed around the first tubular body 1 to form between 
them a jacket 7 into which, through conduits 8, a warm fluid is 
circulated, for example, saturated steam, to heat the first tubular body 
1. 
A frusto-conically shaped coupling 9 connects the first tubular body 1 to 
the second tubular body 2. An electrical insulating gasket 10 is disposed 
between the flanged ends of body member 2 and connecting member 9. 
The second tubular body 2, is connected to electrical resistant circuit 11. 
An electrical current is passed through circuit 11 to heat the entire 
tubular body 2 a desired constant temperature. 
The bore of tubular body 2 has a diameter which is substantially equal to 
the diameter of the hose to be vulcanized. 
A third tubular body member 3 is disposed downstream of the second tubular 
body member 2. A frusto-conically shaped coupling member 12 connects 
tubular body 2 with tubular body 3. 
The frusto-conically shaped coupling member 12, is directly connected, 
through its larger base, to the third tubular body member 3 and is 
connected through its smaller base, to the second tubular body 2. An 
electrical insulating gasket 13 is disposed between tubular member 11 and 
coupling member 12. 
The third tubular body 3, is covered by a radially spaced housing 14 with 
an annular space 15 within which a heating fluid (example, saturated 
steam) is circulated by means of conduits 16. 
Downstream of the third tubular body 3, there is positioned a drawing 
device 17, formed by two endless belts 18 and 18A driven by rollers 19 and 
20, one of which is a driving-roller, while the other is a return-roller. 
The functioning of the described device is as follows: 
An uncured elastomeric hose, in which is present a fluid (e.g. pressurized 
air) enters, in a continuous manner, into the device through coupling 4 
and is pulled by assembly 17, by the end that is downstream of the third 
tubular body. 
The uncured, elastomeric hose, that is already prepared before it enters 
the device where it will be vulcanized, has, for example, the structure 
shown in FIG. 2. 
As can be seen in FIG. 2, the hose has, proceding from the inside towards 
the outside, a core tube 21, a plurality of circumferentially spaced 
longitudinally extending wires or cords 22 embedded in the core tube or in 
the surface of the core tube and disposed along the hose axis, and 
forming, as a whole, a structure resistant against elongation of the hose. 
Around the inner tubular layer or core tube 21, there is disposed a 
helically wound wire or cord 23, that constitutes the transverse resistant 
structure of the hose, and around the said transverse resistant hose 
structure, a tubular covering layer or sheath 24 of an elastomeric 
material is disposed. (see also FIG. 4). 
The angle of inclination of the helically wound wire, is larger than that 
established as optimum for the vulcanized hose. 
The uncured elastomeric hose, before entering the first tubular body 1, is 
preheated, and in particular, the external surface layer of the hose is 
preheated. 
Moreover, the uncured hose, as it gradually enters into the first tubular 
body 1, carries along with it the lubricant present inside the chamber 5, 
and because of the chamber of the frusto-conical coupling 4, the pressure 
of the lubricant carried by the hose rises inside the first tubular body, 
since the frusto-conical coupling is convergent towards the entrance 
opening of the first tubular body. 
The hose thus preheated by passing it through the first tubular body 1, now 
passes through the second tubular body 2, where it comes into contact with 
the surface of the inner cavity of the second tubular body. 
The external surface of the hose, is mechanically pressed by the wall of 
the bore through body 2 and the complete vulcanization of the outer 
surface layer of the hose takes place, while the remaining part of the 
hose remains in its uncured state. 
The hose, enters the second tubular body through the frusto-conical 
coupling 9, which being convergent towards the entrance opening of the 
second tubular body, forces the lubricant that was present inside the 
first tubular body, to pass into the second tubular body, substantially 
increasing its pressure; thus guaranteeing the formation of a continuous 
film of lubricant around the hose, while it is in the second tubular body. 
Inside the second tubular body, the outer elastomeric material of the hose 
is plasticized and vulcanized completely while the outer elastomeric 
surface is under mechanical pressure from compression as it moves through 
the second tubular body. 
The hose, with its already vulcanized external surface layer, emerges from 
the second tubular body and enters the third tubular body through the 
frustoconical coupling 12 that diverges towards the third tubular body. 
During its passage through the coupling 12, owing to the divergence of the 
latter in the advancing direction of the tube the pressure of the 
lubricant that covers the hose is reduced as it passes into the third 
tubular body 3. This facilitates the passage of the lubricant inside the 
device. 
When the hose passes through the third tubular body 3, vulcanization of the 
remaining unvulcanized elastomeric material is completed and the hose is 
advanced by subjecting it to traction by member 17 placed downstream of 
the third tubular body 3. 
The hose portion passing through the third tubular body 3 is subjected to 
traction by member 17. 
From this traction by member 17, the hose length present in the third 
tubular body 3, is subjected to tractional stresses that provoke an 
elastic elongation of the longitudinal resistant structure of the hose, 
i.e., of the wires or cords 22, an elastic elongation of the outer surface 
layer of hose that is already completely vulcanized, and deformation of 
the transverse resistant structure of the hose, i.e., of the helical turns 
of wire or cord 23 that assume the angle B represented in FIG. 3, and is 
smaller than the angle represented in FIG. 2. 
As regards the values of the tractional stresses that provoke an elastic 
elongation of the longitudinal resistant structure of the hose and of the 
completely vulcanized outer surface layer of the hose they must be lower 
than the limit value provoking permanent deformation in the weakest of 
said components subjected to elastic elongation. 
As a result, the completion of the vulcanization of the elastomeric 
material of the hose takes place while the outer surface layer that is 
already vulcanized, and the longitudinal resistant structure of the hose, 
are in an elastically elongated condition. Under the action of the 
traction of the pulling member 17 on the hose through the third tubular 
body 3, and hence following the elastic elongation of the outer surface 
layer that is already completely vulcanized, a reduction in the outer 
diameter of the hose occurs which brings about the following three 
consequences (that explain the achieving of the aims proposed by the 
present invention): 
(a) it facilitates sliding of the hose into the third tubular body 3, 
allowing the hose to be drawn at high speeds through the vulcanizing 
device with a consequent high production output of the device, 
(b) a mechanical pressure is exerted on the inner elastomeric layer still 
in its uncured state, by the outer already vulcanized layer, for which 
reason, during the completion of the vulcanizing of the hose, there is 
obtained a hose with walls that are prefectly compact and devoid of 
porosity; 
(c) the internal diameter of the hose remains constant, the surface of the 
inner cavity of the hose is perfectly smooth and it is possible to form a 
circular or a polygonal inner hose cavity having a number of sides equal 
to the number of wires or cords that form the longitudinal resistant hose 
structure. 
In fact, since during the completion of the vulcanization, the hose 
structure which resists elongation is placed in a condition of being 
elastically elongated, slipping occurs between the resistant structure and 
the layer of the hose that is not yet vulcanized. 
Hence, once the total vulcanization of the hose is terminated and once the 
stresses have been removed in the longitudinal resistant hose structure, 
which is the situation presented downstream of member 17, elastic return 
of the longitudinal resistant structure of the hose occurs. 
With the elastic return of the longitudinal structure of the hose, the 
layer of elastomeric material 21 inside the hose, is compressed, and this 
causes compacting of the inner surface of the hose cavity and the 
formation of a polygonal form of the cavity of the hose. The polygonal 
form becomes circular when the longitudinal structure of the hose is 
formed by a plurality of side-by-side wires. 
From the considerations, it can be seen that with the process and the 
device provided the present invention, the proposed objects can be 
achieved. 
Although the invention has been described in detail for the purpose of 
illustration, it is to be understood that such detail is solely for that 
purpose and that variations can be made therein by those skilled in the 
art without departing from the spirit and scope of the invention except as 
it may be limited by the claims. Any hose having vulcanizable components 
such as a natural or synthetic rubber, such as Neoprene or the like, core 
tube and/or sheath may be vulcanized by the process and in the apparatus 
provided by the invention. Further, any hose having curable by 
cross-linking material components such as curable synthetic resinous 
material may be cross-linked, i.e. vulcanized with the process and with 
the apparatus provided by the invention.