Vulcanization method

A method of vulcanizing continuous lengths of elastomeric or plastomeric material which comprises driving the material through an enclosure, within which it is subjected to vulcanizing conditions, in the form of a helix, the helix convolutions in part contacting a drive mechanism and in part being freely suspended. Also an apparatus for vulcanizing continuous lengths of flexible material, comprising an enclosure, means for providing therein an atmosphere at an elevated temperature and pressure, spaced pressure-retaining inlet and outlet means for the continuous flexible material, and drive and support means for feeding the material through the enclosure in the form of a helix comprising partially unsupported convolutions. The invention is particularly useful in the vulcanization of hosing formed for example by extrusion or by helical winding or both.

This invention relates to the vulcanization of continuous lengths of 
elastomeric or plastomeric material or of structures comprising the same. 
In particular although not exclusively the invention relates to the 
vulcanization of hosing formed for example by extrusion or by helical 
winding or both. It will be understood that the expression "vulcanizing" 
means subjecting the recited material to an elevated temperature for a 
long enough period for the development of a cross-linked structure whether 
through the incorporation of vulcanizing agents or otherwise. It will also 
be understood that reference to "elastomeric" or "plastomeric" material 
includes for convenience reference to such material in which the recited 
properties are only potentially present and are developed as a result of 
the vulcanizing process. For example, the hose may originally comprise an 
unvulcanized rubber composition including a vulcanizing agent; the 
elastomeric properties of the rubber are only developed effectively by the 
vulcanization process. 
It has been the practice to use the so-called catenary method for the 
vulcanization (curing) of continuous lengths of rubber hose. However, this 
technique yields only a relatively low output from a given size of 
equipment. It is an object of the present invention to provide a 
continuous vulcanization process and apparatus affording a higher output 
than the catenary method. 
The invention consists in a method of vulcanizing continuous lengths of 
elastomeric or plastomeric material, hereinafter for convenience referred 
to as flexible material, which comprises driving the material through an 
enclosure within which it is subjected to vulcanization conditions, in the 
form of a helix the helix convolutions in part contacting a drive 
mechanism and in part being freely suspended. 
By feeding the continuous length of flexible vulcanizable material through 
an enclosure such as a steam vulcanization chest, as a helix partly in the 
form of festoons so that the material is exposed to the vulcanizing 
conditions obtaining within the enclosure, a higher production speed is 
made possible as a result of the greatly increased footage provided within 
the heater. At the same time, because the material is uniformly exposed to 
the atmosphere within the enclosure in the festoon portions, the 
vulcanization proceeds evenly. 
To drive the helix within the vulcanization enclosure, each convolution 
will generally be supported at spaced positions and may be driven from one 
such position, the material between adjacent positions being 
self-supporting i.e., festooned. Two such positions for each convolution 
will generally be sufficient, and may for example by provided by a coaxial 
assembly of pulleys or by a correspondingly channeled drum or roller to 
locate as well as support the length of vulcanizing material passing over 
it. 
In the case of a vulcanization chest operating with saturated or 
superheated steam under pressure, sufficiently steam-tight inlet and 
outlet ports for the continuous length of material will be provided. The 
inlet may be for material fed from a previously assembled store thereof, 
for example from a supply drum, or it may admit the continuous length of 
material directly from apparatus for the manufacture, thereof, for example 
from the head of a machine for applying the cover to a hose in the final 
stage of assembly thereof. Generally the cover will be applied to the hose 
which includes a flexible mandrel on the interior but in some instances, 
no internal support such as a flexible or rigid mandrel is present. In any 
event, the hose never includes an external sheath of any kind over the 
external surface of the hose such as a lead jacket or fabric wrap to 
provide a surface configuration or internal pressure resisting means. 
In a preferred arrangement two spaced supports are provided for the inner 
faces of the helix convolutions, one a rotary driving member and the other 
a rotary idler of smaller diameter. Each may be in the form of a coaxial 
set of pulleys or a circularly channelled drum or roller, or one may be 
uncontoured or carry a surface layer of compressible material such as e.g. 
a rubber or plastics foam material so that the contacting portion of the 
vulcanizing material is resiliently supported. 
The invention also consists in apparatus for vulcanizing continuous lengths 
of flexible material, comprising an enclosure, means for providing therein 
an atmosphere at an elevated temperature and pressure, spaced 
pressure-retaining inlet and outlet means for the continuous flexible 
material, and drive and support means for feeding the material through the 
enclosure in the form of a helix comprising partially unsupported 
convolutions. The inlet to the enclosure may be the outlet from apparatus 
for manufacturing the continuous lengths; the drive and support means may 
be as already described. As the hose is fed through the enclosure, the 
hose is not subjected to any significant tension so as to eliminate any 
flat spotting or other distortions which would occur if the hose was under 
tension prior to vulcanization of the elastomeric material of the hose.

The chest comprises a cylinder 1 with end walls (not shown) and a steam 
inlet 2 leading to a steam distribution pipe 3 within the cylinder 1 
(which is shown partly cut away). Journalled within an upper part of the 
cylinder is a roller 4 carried on bearings 5 (of which only one is seen) 
and driven by a suitable motor 6 through a suitable coupling 7. Journalled 
at 8 below the roller 4 is a second roller 9 of smaller diameter the 
surface of which is contoured as at 10 to provide a succession of 
semi-circular section circular channels. Unvulcanized hose 11 from a 
supply drum 12 is fed over a guide roller 13 through a pressure-retaining 
inlet port 14 into the interior of the chest 1. The hose is then led 
around the roller 4 and then wound in the form of a helix around the 
rollers 4 and 9 occupying successive channels 10 in the roller 9 whereby 
the convolutions of the resulting helix are maintained at a given spacing. 
From the end of the resulting helix 15 the hose is led out through a 
pressure retaining port 16 through a hauling device 17 past a guide roller 
18 on to a wind-up drum 19 on which the now vulcanized hose is eventually 
stored. 
The surface of the roller is left smooth, or it may be lined with a 
resiliently compressible material such as a heat-resistant plastics sponge 
for the purpose already indicated. Alternatively, the drive roller 4 may 
be channelled as already described for the roller 9, then the latter may 
be left smooth or lined with a resiliently compressible rubber sponge. It 
is however desirable that one of the rollers 4 and 9 should be contoured 
to locate the convolutions, and it will be understood that more than one 
idler roller 9 may be provided. Between the idler roller and the drive 
roller 4, the convolutions of the helix appear as festoons, that is to say 
they are unsupported and uniformly subjected to vulcanizing conditions 
within the steam chest 1. 
Where the drums are grooved, it is preferred that the radius of the 
semi-circular grooves should be slightly larger than the external diameter 
of the hose. 
It will be understood that the flexible vulcanizable material fed through 
the vulcanizing apparatus in accordance with the invention will in general 
be accompanied by other material, such as fibrous reinforcement and filler 
material. Thus for example, the hose to be vulcanized in the example just 
given may comprise an inner extruded tubular portion, balanced windings of 
fibre-reinforced rubber stock and an outer sleeve or cover.