Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an improved method
for manufacturing rollers or idlers.
The invention more particularly relates to an irnproved
method for manufacturing rollers or idlers having a resilient
cover.
Rollers and idlers, usually made from steel, are
commonly used in belt conveyors to support the belt. When the
belt conveyors a~e used in heavy duty operations, such as in the
mining industry to convey ore, it is preferable to cover the steel
rollers or idlers with a protective cover to prevent excessive
wear and built up on the surface. The cover usually employed
is a rubber sheet wrapped around or a rubber sleeve secured with
an adhesive or vulcanized to the cylindrical surface of the steel
xo]l, or an urethane or polyurethane -layer cast or mold onto the
rollersor idlers and subsequently cured or vulcanized, such invol-
ving a surface prepaiation such as sand 41asting. The above cover
. helps to improve the wear factor but still presents a high coef-
ficient of friction and sometimes bigger built-up than plain steel
rollers or idlers. Moreover, it also occurs that the adhesive
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fails and the cover pulls away from the roll surface. Frequent
roller replacement is therefore necessary.~ ~
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It is the~object of the present invention to prov~e ~ ~
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covered rollers or idlers for use in conveyors which rollers or
idlers do not fail as frequently as the~known covered rollers.
More particularly, it is the object of the present invention to
provide a method ~or manufactuxing such improved rollers or idlers.
In accordance with the present invent~ion, the roller
or idler is made by covering a ~teel core with a tubular, ultra
high molecular weight polyethylene cover. The tubular cover
used initially has an inner diameter slightly smaller than the
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outer diameter o~ the steel core. To place the cover on the
core, the cover is first heated, and then while warm, mechani-
- cally expanded or enlarged until its inner diameter is slightly
greater than the outer diameter of the core~ After being ~ J/
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mechanically expanded, and while still warm, the co~er is
slipped over the core and is then allowed to cool. The cover
as it cools, shrinks to provi~e a tight shrink fit on the core.
It is well known to shrink ~it two members together
by heating one member to expand it, and while expanded, placing
the one member over the other member, and allowing it to cool
to shrink fit tightly in place on the other member. However,
ultra high molecular weight polyethylene cannot be handled in
this manner. When heated to a temperature high enough to
expand sufficiently, it loses its desirable strength properties.
In accordance with the present invention, it has been
discovered however that an ultra high molecular weight poly-
ethylene cover can be mechanically expanded after being
slightly heated and the cover when allowed to cool, elastically
recovers to its original pre-expanded size without losing any
strength. Thus such a cover can be shrunk fit onto a core if
properly handled.
The present invsntion is therefore strictly restrict-
ed to a method for manufacturing an improved roller or idler
by properly applying an ultra high molecular weight poly-
ethylene cover to a steel core.
The invention is particularly restricted to a method
for covering a cylindrical metal roller core with a tubular
cover made from ultra high molecular weight polyethylene, said
tubular cover having an inner diameter slightly smaller than
the outer diameter of the metal roller core, said method com-
prising the steps of:
heating the tubular cover to a warm temperature
ranging between 120F and 150F for a period of time ranging
from 20 to 30 minutes;
mechanically enlarging the warm heated tubular cover
to increase its inner diameter until it exceeds the outer
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diameter of the metal roller core;
placing the mechanically enlarged, warm heated cover
over the metal roller core; and
allowing the warm heatéd cover to cool at ambient
temperature thereby shrink fitting said warm heated cover onto
the metal roller core.
The invention will now be described in detail having .
reference to the accompanying drawings in which: .
Fig. 1 is a schematic view of a conveyor incorporat- :
ing ~
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rollers,
Fig. 2 is a cross~section view o~ the two parts of
the roller used ~n the conveyor?
Fi~s, 3a and 3b a~e end ~iews of the rollex cover
being expanded;
Fiy, 4 is an ele~ation view showing installation of
the expanded roller cover on the roller core; and
Fig. 5 is a schematic view showin~ further treatment
of the newly manu~actured roller~
The conveyor 3 schematically illustrated on Fig. 1
comprises, as every conveyor~ at least one driving roller 2
and a plurality of-idlers 1, The idlers 1 and roller 2 support
and drive a belt 5 in closed loop, the belt 5 carrying material
such as ore which is to be transported from one place to another.
The covered idlers 1 each comprise a central, cylin-
drical core 7 and an outer, tubular cover 9. The cylindrical
core 7 is made from suitable metal, such as steel and has means
(not shown) at its ends 11 ~or rotatably mounting the idler 1
in the conveyor 3. The outer, tubular cover 9 is made ~rom a
suitable ultra high molecular weight polyethylene such as that
sold under the registered trademark GAR-DUR. The cover 9 has
an inside diameter 13 that is slightly smaller than the outside
diameter 15 of the core 7.
To mount the cover 9 on the core 7, the cover 9 is
first heated so that it can be mechanically expanded. The cover
9 is preferably heated to a temperature ranglng between 120F
and 1500F and held at this temperature for a time ranging
between 20 and 30 minutes.
The heated cover 9 i5 then mechanically expanded
to increase its inside di~meter 13 until it is slightly greater
than the outside diameter 15 of thè core 7. To this end,
the heated coVer 9 is placed over an expander 17, The expander
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17 comprises a cylind~ical base 19 extending yertically down
from a fixed frame 21~ The expander 17 has a set o~ movable
. exp~nder bars 23 mounted on th:e base 19. The bars 23 extend
parallel to the ax~s o~ the base 19 and to each other about the
cylindrical sur~ace.o~ the base 19, Suitable cam means (not
shown) are provided on th.e expand~r for moving the bars 23 ra-.
dially outwardly ~rom the base 19. The cam means can be
hydraulically operated or they can be operated by other suitable
means. Expanders o~ the above type, and their operation, are
well known. With the baxs 23 in a radially withdrawn pos.ition, .
as shown in Fig. 3a, the heated cover 9 can just slip up over
the expander 17. Once the heated cover is on the expander 17,
the expander 17 is operated to move the expander bars 23 radial- :
ly outwardly as shown in Fig. 3b thereby s.tretching and
enlarging the .cover 9. ~-:
. Once the heated cover 9 has been expanded to th~
- desired inner diametèr, it is removed from the expander 17
and placed over the core 7. The core 7 can be po~.itioned
beneath the expander, axially aligned with the base 19 as
shown in Fi~. 4. The expander bars 23 axe then moved radially
inwardly allowing the expanded cover 9 to drop down over the
core 7. As the cover 9 cools~ it shrinks and is retained on
the core 7 hy a ti~ht shrink ~it to ~orm a idler 1. The
cover 9 o~ the fabricated idler 1 can now be machined, if
desired, as-shown in Fig. 5 to provide a perfectly cylindricaI
surface on the idler.
. A main advantage~of the ~bove described method of
manu~acturing covered idlers or rollers lies in that the
covex~ owin~ to its ori~inall~ smaller diameter~ is strongly
- 3Q secured to the core ~ithout external means, such as adhesive
meanst Anothex advantage of the method lies in that the
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cover owin~ to it~ int~insi.c ~o~e~ties~ advanta~eousl~
provides each ~dler or roller with~a very smooth external
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~ suX~ace with a ve~y low coe~ficient o~ ~riction,
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