CA1147133A

CA1147133A - Method for manufacturing rollers or idlers

Info

Publication number: CA1147133A
Application number: CA000359292A
Authority: CA
Inventors: Denis Thibault
Original assignee: FORMOTHANE INC.
Current assignee: FORMOTHANE Inc
Priority date: 1980-08-29
Filing date: 1980-08-29
Publication date: 1983-05-31

Abstract

ABSTRACT OF THE DISCLOSURE

A method of manufacturing a covered roller or idler having a cylindrical metal core and a tubular ultra high molecu-lar weight polyethylene cover. According to this method, the cover which has a slightly smaller inside diameter than the outside diameter of the core, is heated and subsequently mecha-nically expanded to increase its inner diameter. The so heated, expanded cover is then slipped over the core and allowed to cool to provide a tight shrink fit.

Description

7~33 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 ,~
fails and the cover pulls away from the roll surface. Frequent roller replacement is therefore necessary.~ ~
.
It is the~object of the present invention to prov~e ~ ~
.
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 ::
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/

L7~L;33 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 ~,,~ '

2 ~

~1~7~L33 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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~ / :

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~ 2a ~7~33 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 ~ 3 ~

~7~33 .

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 . ~ 4 ~

..

~7~33 cover owin~ to it~ int~insi.c ~o~e~ties~ advanta~eousl~
provides each ~dler or roller with~a very smooth external .
~ suX~ace with a ve~y low coe~ficient o~ ~riction, , .

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. 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 comprising the steps of:
heating the tubular cover to a warm temperature ranging between 120°F and 150°F 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 diameter of the metal roller core;
placing the mechanically enlarged, warm heated cover over the metal roller core; and allowing the warm heated cover to cool at ambient temperature thereby shrink fitting said warm heated cover onto the metal roller core.

2. A method as claimed in claim 1, wherein the warm heated cover is mechanically enlarged by placing it over a cylindrical arrangement of straight bars and mechani-cally moving each bar radially outwardly against the inner surface of the warm heated cover.

3. A method as claimed in claim 2, wherein the warm heated core is placed in an axially disposed position relative to the metal roller core by:
vertically suspending the cylindrical bar arrangement from its top end;
placing the metal roller core under the cylindrical bar arrangement in axial alignment therewith; and moving the bars radially inwardly after expanding the warm heated cover to allow said warm heated cover to fall over the metal roller core prior to shrink fitting onto said metal roller core.

4. A method as claimed in claim 1 comprising the additional step of machining the cover after it is shrunk onto the metal roller core.