TUBE

TUBING

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
A novel plastics tube is provided herein. The
tube has applied thereto a plurality of longitudinal strips
on the outer surface to increase the surface area thereof
to enable the tube to be gripped more readily during the
application of couplings and the like. A method of manu-
facturing such a tube is also provided, including the steps
of extruding the tube, contacting a substantially continuous
length of thermoplastics strip with the surface of the
tube after extrusion at a temperature at which the tube
and/or the strip is above its softening point, pressing
the tube and the strip together and thereafter cooling
to cause or allow fusion between the tube and the strip.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A tube of a cross-linked polyolefinic thermoplastics material
including one or more longitudinal strips on the outer surface there-
of to increase the surface area thereof, thereby enabling the tube
to be gripped more easily, wherein each longitudinal strip is formed
of a thermoplastics material separately of the tube and subsequently
united therewith after formation of the tube.
2. A method of producing a tube which method comprises; extruding
the tube of a cross-linked polyolefinic plastics material; contacting
a substantially continuous length of thermoplastics strip with the
surface of the tube after extrusion at a temperature at which at
least one of the tube and the strip is above its softening point;
pressing the strip and the tube together; and thereafter cooling
to produce fusion between the tube and the strip.

Description

1037~96
'l`rlis invcntioll r~ela~es Lo tuL):in~ and ~lcls particula~ re~erence
to plas-tics material tubing for use Ln -the supply of services and other
pipework in buildings and industry, Plastics ma-terial tubes are easier
to ins~all than me-tal tubes, are corrosion resistant and since they also
have smooth surfaces -they -tend -to accumulate less dirt and other materials
than their metal counterparts and are less likely to sus~ain permanent
damage due to the resilient nature of the plastics material itself.
Jointing of plastics material tubing is usually by means of
adhesive or by conven-tional screw threaded connections.
!~ Unfortunately, the smooth outside surface of plastics material
pipes in general results in some difficulties in installation since it
makes it difficult for fitters to grip the pipe in the manner necessary
to tighten up a screw union using a union spanner or torque wrench. In
particular the application of pressure -to -the pipe is likely to deform
the pipe but the flexible nature allied with the smooth surface merely
results in the pipe rotating under the torque applied via the union.
The use of gloves, rag ancl other likely methods of overcoming
and increasing the friction between à grip and the tube can assist but
1 does not entirely overcome the problem.
According to one aspect of the present invention, there is
provided a tube of a cross-linked polyolefinic thermoplastics material
including one or more longitudinal strips on the outer surface thereof
to incr~ease the surface area thereof, thereby enabling the tube to be
gripped more easily, wherein each longitudinal strip is formed of a
thermoplastics material separately of the tube and subsequently united
therewith after formation of the tube.
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~Q37;396
Eacll lorlg:i~uclir~cll strip mly be rormed seE~clrately of the
tube and united therew:i-th after t`ormcltion of the tube. The strips
may be of a plastic ma-terial different from -the plastics material
of the -tube and each strip itsel~ may have a plurality of longi-tudinal
surface projections.
The tube may be of cross-linked polyolefinic material;
alternatively the ~be may be formed of polyvinylchloride, polybutylene,
polypropylene or polye-thylene. The strip may also be of a -thermoplastic
material typically polyethylene or polypropylene.
The strips may be coloured with different pigments or
colouring matter to provide a means for identifying the nature of the
pipes and/or size or quality.
In accordance with another aspect of the present invention,
two or three longitudinal strips may be provided on the surface of a
tube and it has been found that the provision of these strips gives
a means of providing an improved grip on the pipe for the application
of unions and the like.
The present invention in ano-ther of its aspects also includes
a method of producing a tube which method comprises; extruding the
tube of a cross-linked polyolefinic plastics material; contacting a
substantially continuous length of thermoplastics strip with the
surface of the tube after extrusion at a temperature at which at least
one of-the tube and the strip is above its softening point; pressing
the strip and the tube together; and thereafter cooling to produce
fusion between -the tube and the strip.
In a particular embodiment of this aspect of the present
invention the strip may be at room -temperature
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J ~37~6 :~
and the tube te~perature may be of the o~der of 200 DC
The contact of the strip with the tube results in a partial
melting of the strip to produce fusion between the strip
and the tube.
In the acco~panying drawings,
Figure 1 is a perspective view of the tube in accordance
with one aspect of the present invention and
Figure 2 is a diagrammatic view of the apparatus
for the production of tubes in accordance with the method
of another aspect of the present invention~
In Figure 1, a cross linked polyethylene tube 10
has an outer surface 11 and on the outer surface are three
longitudinally extending strips 12, each formed of thermQ-
plastic polyethylene and fused with the cross-linked poly-
ethylene of the tube 10. Each strip is of a different ~
colour to identify the nature and quality of the tube. ;
Each strip is formed by a semi-circular strip having an outer
substantially hemi-cylindrical outer surface 13. -
The cross-linked polyethylene tube 10 is usually ,
produced by extrusion 'as seen in Figure 2. On leaving an
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extruder 20 the tube 21, which has a temperature of the order
of 200C, is passed over a table 22 having above it a platen l~
23. A roll 24 of strip materlal 25 of thermoplastic poly~
ethylene is fed onto a surface of the tube and passed under
platen 23 to~press the strip onto the surface. The effect -
of the strip 25 being pressed into contact with the hot
wall of tube 21 is to cause softening of that portion of
the strip juxtaposed the tube and to allow fusion there~
between. After leaving the table 22 and platen 23 the tube,
having strips on the surface, is pass~d through a cooling
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bath 26 for,cooling of the tube wall and the tube having
the longitudinal strip or strips in the surface thereof
passes from the cooling bath for winding on a spool or
drum (not shown).
It has been found that tubes having a strip or
strips and produced in a manner described above exhibit
the ability to be readily gripped by a tool or by hand
and the tendency of the tube to rotate under the application
of torque is markedly reduced.