Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a conveyor roller
whose cylindrical body is made from a moldable polymer
concrete material. The invention further relates to a
conveyor roller provided with at least one encapsulated
labyrinth seal mounted on a shaft of the roller inside
each end of the roller body such that the seal is
contained within the roller body between a bearing o
the roller and an exterior side of the roller body.
Conveyor rollers are conventionally made of steel,
that is the conventional roller comprises a cylindrical
steel tube which rotates on a shaft by means of
bearings. The present invention relates to a conveyor
roller made of a moldable polymer concrete or resin
concrete material which has many advantages over steel
or metal constructions. A roller constructed of a
polymer concrete material can be more shock resistant,
more resistant to acids and caustic substances from low
pH to high pH, and easier to manufacture than a roller
constructed of steel or other metal materials.
A problem arising with conventional conveyor
rollers, however, i5 that the bearings of the roller
become contaminated with foreign matter (such as dust
particles) originating from the environment in which the
roller operates. Contamination of the roller bearings
is the primary reason for roller breakdown.
Contamination will damage a bearing due to mechanical
wear on the bearing caused by the interaction of the
foreign particulate matter and the bearing movements, and
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due to chemical wear, such as rusting. A damaged
bearing can d~cr~ase operating efEiciency, require
replacemen~, or lock up causing possible damage to a
conveyor belt. It is known to the inventors to make a
conveyor roller using a polymer concrete, however, the
known roller has no labyrinth seal provided inside the
roller body to protect the bearings ayainst
contamination.
It is therefore an object of the present invention
to provide a moldable polymer concrete conveyor roller
which is provided with encapsulated labyrinth seals
provided inside the roller body to protect the bearings
against contamination.
The object of the invention is achieved by a
conveyor roller comprising a shaft, a plurality of
bearings provided on the shaft, and a roller body having
a cylindrical side surface and two exterior end walls,
the body being fixed to the bearings, and being
rotatable on the shaft, wherein the roller body is made
with a moldable polymer concrete material, and contains
encapsulated labyrinth seal means which are connectad to
the shaft and are provided inside each end of the roller
body between the bearings and each exterior end wall of
the roller body.
Preferably the encapsulated labyrinth seal is packed
with a high viscosity heat resistant lubricant. It is
also preferable to separate each labyrinth seal from
each associated bsaring by means of a spacer ring having
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a diameter smaller than both the bearing housing and -the
labyrinth seal housing, so that the roller body material
can define a wall between the bearing and seal. The
spacer ring may have an inner diameter which is only
slightly greater than the diameter of the shaft, so that
the path through which contaminants must travel to reach
the bearings is further restricted.
The conveyor roller according to the invention is
further improved by providing the roller with a hollow
core through which heat, generated by the bearings and
transferred to the shaft, can be transferred from the
shaft through the hollow core to the roller body at a
position in the roller body proximal to the exterior
side surface thereof. This hollow core is
advantageously filled with air. The polymer concrete
may comprise as binding agent one or more products
selected from the group consisting of polyesters,
polyamines, polyethers, raw glass and poly- carbonates.
Advantageously, polymer concrete comprises a resin mix
that generates heat during curing, so that no heat needs
to be added during curing.
Advantageously/ the polymer concrete used to form
the roller body according to the invention, may be
obtained by mixing one or more resins, such as
unsaturated polyester resins (especially a flexible, low
reactivity, intermediate viscosity, isophthalic acid
based, unsaturated polyester resin, such as Reichhold
31-830 (TM) or Kopper 1201-5 (TM) ) in the pressnce of
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an appropriate catalyst (especially Cobalt/Methyl Ethyl
Ketone Benzoyl Peroxide systems or Benzoyl Peroxide,
such as superox 46-706 (TM) ) with a filler especially
in powder form.
Atlernatively, the aforesaid resins may be one or
more polyester resins, such as Polylite (TM) polyester
resin (Reichhold's 33-402) which is a rigid, medium
reactivity, premium chemical resistant, isophthalic
based polyester. This resin is low viscosity,
thixotropic and pre-promoted for room temperature cure
with the addition of Methyl Ethyl Ketone Peroxide or
Benzoyl Peroxide.
One skilled in the art can determine easily the
particle size of the powder defining the filler. This
particle size may vary within a range so far as it can
be homogeneously mixed with the resin.
The preferred filler may be selected amongst three
different fillers to strengthen the body and also
increase the abrasion resistance:
1 - a mixture of silica sands and iron dust which gives
an abrasion of ll mg on the A.S.T.M. taber test C.S. 17;
2 - a mixture of silicon carbide and iron dust to achieve
a taber of 7 mg;
3 - pure silicon carbide which gives a taber of 3 mg.
In comparison, a steel pla~e of 40,000 psi will lose
238 mg in the same test.
The polymer concrete described may also have great
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compression resistance. Depending on the mixture used,
one can obtain a compression resistance between 19,000
psi to 74,0QO psi.
Preferably, in order to obtain a polymer concre-te
which is particularly able to resist impacts due to
material flex, the resin, Reichhold's 31-830 (TM) or
Kopper's 1201-5 (TM), is selected and the filler is
chosen to be silicon carbide. The ratio by volume of
silicon carbide powder (filler) to resin is 3:1.
Preferably, in order to obtain a polymer concrete
which is for standard conventional uses, the selected
resin consists of Reichhold's 31-830 polyester or
Kopper's 1201-5 equally mixed with Reichhold's 33-402,
the resulting resin is then mixed with silicon carbide
powder at the above mentioned ratio.
Other objects and advantages of the invention will
become clear by the following description of a preferred
embodiment with reference to the appended drawings in
which:
- Fig. 1 is a cross-section through the center of the
shaft of the conveyor roller according to the preferred
embodiment.
Fig. 2 is an enlarged cross-sectional view of the
preferred embodiment showing in detail an encapsulated
labyrinth seal.
Fig. 3 is an enlarged cross-sectional view of
another preferred embodiment showing in detail another
encapsulated labyrinth seal.
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In the preferred embodiment, the conveyor roller has
a body 9, a shaft 1, and bearings 5. The body 9 rotates
about the shaft 1 by means of the bearings 5. Cap 2 and
labyrinth seal 3 prevent dust, moisture and/or other
foreign matter from contaminating the bearings 5, in
order to prolong the life of the bearings 5. End plates
6 hold jacket lo which forms a hollow core 8. Spacer
ring 4 separates the tongue and groove arrangement 3
from the bearings 5 so that the material of the body 9
may support the bearings 5. Retainers 7 are secured to
the shaft 1 so that the body 9 may not move in the
direction of the axis of the shaft 1.
The body 9 is formed by molding a polymer concrete
material in a mold containing the components attached to
the shaft 1. In the preferred embodiment, the polymer
concrete is obtained by mixing three parts by volume of
silicon carbide with one part polymer resin or polymer
resin mix, and effective amount of a catalyst. The
polymer resin is preferably a flexible, low reactivity,
intermediate viscosity, isophthalic acid based,
unsaturated polyester resin, such as the commercial
products; Reichhold (T~ no. 31-830 and Kopper (TM) no.
1201-5. The resin may also consist of a mixture of at
least one resin with the above mentioned characteristics
and a rigid, medium reactivity, premium chemical
resistant, isophthalic based, low viscosity, thixotropic
resin, such as the commercial product: Reichhold (TM)
no. 33-402. The catalyst may be selected amongst
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cobalt~methyl ehtyl ketone benzoyl peroxide systems,
methyl ethyl ketone benzoyl peroxide and benzoyl
peroxide systems.
The primary reason for bearing breakdown in a
conveyor roller is contamination due to dust or
moisture. Fig. 2 shows an encapsulated labyrinth seal
3 used to prevent foreign matter such as dust or other
particulate matter from contaminating the roller
bearings 5. The seal 3 is packed with grease or any
suitable high viscosity heat resistant lubricant, to
provide a barrier to the migration of dust particles.
Cap 2 is shown in Fig. 2 connected to the roller body 9,
and provides a coarse barrier to larger dust particles.
The space between the cap 2 and the seal 3 can also be
packed with grease. The seal 3 shown in Fig. 2 has
concentric non-contacting tongues and grooves pr~jecting
in the direction of the shaft 1. The labyrinth seal
comprises a shaft mounted piece 12 and a roller body
mounted piece 14 each having concentric tongues and
grooves to form a non-contacting tongue an~ groove
arrangement. The seal 3 is encapsulated by a cap 16,
which increases the labyrinth path and contains the seal
3 during molding. The purpose of the seal 3 is to pose
a long and tortuous path through which any dust or
foreign matter would need to travel to reach the
bearings 5. The seal 3 can act as a trap for dust or
other foreign matter because of the path through which
foreign matter must travel as well as the centrifugal
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force ~xerted by the seal on any matter in the seal,
which prevents any matter entering the seal 3 from
returning to the shaft 1.
Fig. 3 shows a labyrinth seal 3 according to another
preferred embodiment. Tongues and grooves ar~ arranged
in the radial direction of the shaft 1. ~ sha~t mounted
piece 18 having three radial discs, and a roller body
mounted piece receiving the three discs form the seal 3.
The seal 3 shown in Fig. 3 has a smaller diameter,
making it more useful for smaller diameter rollers. The
priciple of operation of the seal 3 shown in Fig. 3 is
similar to that of the seal shown in Fig. 2. The cap 2
is shown mounted on the shaft l instead of the roller
body 9 as in Fig. 2. The shaft l is shown to have a
ridge retainer 7' instead of a ring retainer 7 as shown
in Fig. 2.
The labyrinth seal 3 placed inside t'he roller body
9 as shown in the Figures offers several advantages.
Among these advantages, there is the placement of the
seal 3 between the end of the roller body 9 and the
bearing 5 with ample space to allow the body 9 to
support a housing of the seal 3 made of piece 20 or cap
16 and piece 14, allows a construction to be made
wherein the seal 3 and the bearing 5 are sufficiently
secured by the body 9. Also, there is a composite
sealing which is preferably achieved by the end cap 2,
the space between the end cap 2 and the labyrinth seal
3, the space being advantageously filled with grease,
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the labyrinth seal 3 itsel~, and the separation between
the seal 3 and the bearing 5 provided by the spacer ring
4. The spacer ring has an inner diameter only slightly
larger than the diameter of the shaft. The combination
of such impediments provides a particularly preferred
improved seal against contamination by foreign matter.
In operation, the bearings 5 generate heat as a
result of friction. The heat is essentially transferred
from the bearings 5 to the shaft 1 to which the bearings
5 are mounted. The heat is conducted by the shaft 1 to
the ends of the shaft 1 ~here the heat is dissipated to
the outside of the roller. The heat is also conducted
by the shaft 1 to the hollow core 8 where the heat is
transferred to a jacket 10 of the core 8. From the
jacket 10 to surface 11 of the roller, the heat is
transferred relatively efficiently due to the large
transfer area, and from the surface 11 the heat is
dissipated to the outside of the roller. In the
preferred embodiment, the end plates 6 are made of a
good thermal conductor, so that the heat generated by
the bearings 5 at the radial outer surface of the
bearings 5 is efficiently conducted toward the surface
11 for dissipation to the outside. While t~le jacket 10
can be made of plastic or cardboard, it can also be made
of a good thermal conductor such as metal, so that the
heat conducted by the end plates 6 is transferred over
the whole surface of the jacket 10 for a more efficient
transfer to the surface 11 of the roller.
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Advanta~eously, there is at least 2.5 cm of resin
concrete between the jacket 10 and the surface 11.
As can be understood from the above description, the
invention provides a conveyor roller which offers the
following advantages; it is resistant to dus-t
contamination due to the cap 2 and the encapsulated
labyrinth seal 3 contained within the roller body 9 to
improve the isolation of contaminants from the bearings
5, it is resistant to shocks due to the use of a shock
resistant polymer concrete, it requires no lubricant
maintenance for the life of the roller, it is less
likely to lock up or break which can cause damage to a
conveyor belt, the polymer concrete can be made to be
resistant to caustic substances such as cleaning
solutions, and it is easy to manufacture in any size or
shape due to the moldable construction of the roller
body 9. Of course, the molding of the conveyor roller
is carried out in accordance with molding techniques
well known in the art.
It is to be understood that the above description of
the invention is not intended to limit the scope of the
present invention as defined in the appended claims.
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