Note: Descriptions are shown in the official language in which they were submitted.
2136359
METHOD AND APPARATUS FOR MANUFACTURING PAINT ROLLER
AND PRODUCT PRODUCED THEREBY
FIELD OF THE INVENTION
The present invention relates generally to the manufacture of composite
thermoplastic products and more specifically to an improved method of
manufacturing
paint rollers and the product produced thereby. More particularly, the present
invention
relates to methods for conditioning the surface of a thermoplastic tube to
receive a
variety of adhesives suitable for adhering a thermoplastic compatible fabric
strip to the
thermoplastic tube which, for purposes of illustration, will be a
thermoplastic paint roller
core.
BA K~~ROUND OF THE INVENTIQN
Currently in the manufacture of paint rollers, strips of pile fabric are used
which are
wound around a plastic or cardboard tube or core. More specifically, among the
devices
currently employed is a type of machine illustrated in Spanish Utility Model
No.293,980
filed on 6 May, 1986 and granted on 1 September, 1986, which includes a
rotating
cylinder over which the cardboard or plastic tube is mounted, and onto which a
strip of
pile fabric is applied through a guide oriented obliquely and situated on and
carried by a
carriage which is mounted in fixed fashion over a sliding apparatus. The
bonding of the
tube and strip of pile fabric is accomplished either by the application of
adhesive material
in the case of a cardboard
~. -2-
tube or, in the case of a plastic tube, gas flame heating by which gas burners
heat the
tube to bond it to the strip of pile fabric, thereby forming a single body.
In the first case, i.e., where conventional adhesive is used as the means of
bonding
between the cardboard tube and strip of pile fabric, the manufacture of paint
rollers
S presents significant problems, all resulting from the difficulty of applying
the adhesive
uniformly, plus the fact that very specific adhesives must be used to produce
the bond
between the cardboard tube and the strip of pile fabric so that, when the
rollers are
used, these adhesives do not separate due to the solvents contained in the
paint and in
the fluids used to clean the roller.
These problems considerably increase the cost of manufacturing paint rollers
because of the cost of the adhesives and the time needed for the adhesives to
harden.
The second system mentioned above, though a significant advance in the art
over
what had been earlier used, does present certain problems, all resulting from
the
increased safety costs' required by installations that use gas as a fuel
source for the gas
flame heating. Further, the heating of the plastic tube can produce
undesirable products
of combustion and high noise, both effects being potentially harmful for the
operators
and expensive to eliminate; all of this therefore has the result of raising
the cost of the
final product.
,~Y OF THE INVENTION
The object of the present invention is a procedure for manufacturing paint
rollers
and the product produced thereby, of the type in which a strip of pile fabric
is wound
helically over a plastic base structure, such as a tube or core, with a
thermoplastic
adhesive substance interposed there-between, with the result that the strip of
pile fabric
and the plastic base structure form a single, integral composite end product.
-3- 2136359
Specifically, an intermediate thermoplastic adhesive substance is applied onto
a
plastic tube in the area adjacent to the area of the winding of a fabric strip
on the tube,
the adhesive substance being heated. If the adhesive substance is molten it
may be
applied through a nozzle connected to a reservoir where the thermoplastic
adhesive is
heated, which nozzle is mounted on a carriage on which the pile fabric strip
applicator is
also located. Suitable adhesives include polypropylene, polyethylene, a
mixture of
polypropylene and polyethylene, any of a variety of polyamides, polyolefin
based
compounds, polyester based compounds, polyurethane based compounds, polyamide
"hot
melt" adhesives sold under the designations HB Fuller Hot Melt*6542-PEL and
HL2d21,
Hot Melt~'2167PL and other suitable adhesives compatible with a thermoplastic
tube,
such as a polypropylene tube, a polyethylene tube, a nylon tube, or a
combination of
polypropylene and polyethylene, and resistant to the anticipated solvents
found in the
paint, stain, shellac or varnish and the solvents used to clean the roller.
The anticipated
solvents include turpentine, mineral spirits, aliphatic compounds, ketones or
aromatics in
IS petroleum based solvents including naphtha, chlorinated hydrocarbons,
alcohol based
solvents, acetone, toluene and water including soapy water and ammoniated
water.
Another object of the present invention is the provision of a paint roller
which is
structurally integral as a result of the bonding of the thermoplastic adhesive
with the
strip of the pile fabric and the plastic tube.
BRIEF DESCRIPT10N OF THE DRAWINGS
The invention is illustrated more or less diagrammatically in the accompanying
drawing wherein:
Figure 1 is a side view, partially in section ' and with standard components
indicated diagrammatically, of a method of producing a plastic paint roller;
Figure 2 is a side view, partly in section of an alternative method of
producing a
paint roller;
*Trademark
.:~ -4- 2136359
Figure 3 is a side view of a plasma jet discharge head usable in the
embodiment
of Figure 1;
Figure 4 is a right end vi<:w of Figure 3;
Figure 5 is a top view of the current input box for the discharge head which
connects the discharge head to the power unit;
Figure 6 is a plan view of an alternative embodiment in which a plastic tube
is
mounted over a rotating roller and the strip of pile fabric is wound helically
and further
including a movable carriage on which are situated the applicator of the pile
fabric strip
and the nozzle for applying thermoplastic adhesive in a molten state;
' Figure 7 is a plan view of an alternative embodiment in which a plastic tube
is
mounted on a rotating roller which is moved longitudinally by means of a drive
unit, the
strip of helically wound pile fabric and the applicator of the thermoplastic
adhesive in a
molten state being located on a fixed carriage;
Figure 8 is a section view of either of Figures 6 or 7 showing a section of
the
roller already constructed, wherein the strip of pile fabric, the
thermoplastic adhesive
and the plastic tube form a single body; and
Figure 9 is a side view, p<~rtly in section, of a further embodiment of the
invention
in which, if desired, a supporting; mandrel may be dispensed with.
DETAILED LfES~RIPTION OF THE INVENTION
Referring first to the embodiment of Figure 1 a supporting mandrel is
indicated at
10, the mandrel being supported in suitable bearings, not shown. A self
sustaining plastic tube,
which forms the structural core of the final product, here a paint roller, is
indicated at 11, the core
being driven in the direction of arrow 12 by any suitable means, such as a
-s- 2i 36359
conventional Ford drive, indicated diagrammatically at 19, located near the
left end of
the processing sequence shown in Figure 1. The tube may be composed of any
suitable
thermoplastic material such as polypropylene, polyethylene, polyamides,
polyolefins or
mixtures thereof. For paint rollers polypropylene is the industry's material
of choice.
s The core may be either cold. or heated as it enters the processing steps to
be
subsequently described hereafter. If heated to the point where cooling to room
temperature will cause an internal dimensional contraction, the mandrel 10 may
be
slightly tapered in a leftward direction to accommodate the shrinkage. If
possible the
core should be heated so as to decrease the additional heat energy which must
be
supplied to complete the processing.
An adhesive substance, here a thermoplastic material in strip form which is
compatible in a bond and strength sense with the core and fabric which will
later be
added, is indicated at 1s. The adhesive substance, which may for example be
polypropylene or any one of the other substances above mentioned in
conjunction with
is the core, or slight modification thereof, is fed from a suitable source of
supply and is
wrapped around the core in such fashion that the laps butt snugly against one
another.
Preferably, though not essentially, the adhesive substance is at an elevated
temperature to facilitate bonding to core 11. In this instance a process is
illustrated in
which supplemental heat energy is added to the core to ensure good bonding
between
the core and the adhesive substance. The supplemental heat energy may be
supplied by
any suitable means such as flame burners, electrical resistance heating, radio
frequency,
infra red, quartz, induction, ultrasonic or plasma jet electrical discharge
means. Here the
latter has been illustrated, said plasma jet system consisting of a power
unit, indicated
generally at 16, and a discharge head, indicated generally at 17, the
discharge head being
2s connected to the power unit by leads 18. It should be understood that the
ultimate
objective of insuring a good bond between the adhesive substance and the core
is a
matter of proper selection of the: above described heating forms. Thus, if the
core 11
has a high heat content, as it would if it were freshly extruded at a location
just to the
right of the right end of Figure l, and the single layer of the adhesive
substance 1 S was
also either freshly
-6- 2136359
extruded, or freshly heated, the ;jet plasma or alternate heating system may
be omitted.
If on the other hand the core 11 is cold, that is, at room temperature at the
start of the
process, then the use of the plasma jet or alternate heating system will
probably be
essential. It may be most convenient to use the adhesive substance 15 in coil
form at
room temperature. In this event the adhesive substance 15 may have its outer
surface,
that is, the surface which will subsequently come in contact with the pile
fabric, heated,
or, if desired, just the inner surface, or both, heated. Any one of the
foregoing heating
systems may be used, the selection of which one dependent on operating
parameters
pertaining to each installation, including cost. In essence, the heating
sources used and
the extent to which they are used, can be tailored to the conditions which are
present in
each factory, and those basic operating conditions - space, power
availability,
economies of production inherent in a given location, etc. - will vary from
factory to
factory.
A pile fabric in strip forni is indicated at 20, the fabric being wrapped
about the
core-adhesive substance structure, indicated generally at 21, in such fashion
that the
individual wraps butt tightly against one another.
Again, the primary objective is to form a tight bond between the back side of
the
fabric and the structure 21. Although heating the back side of the fabric 20
may be
feasible in some cases, this is not usually preferred due to possible over
heating and
consequent degradation of the fabric pile. If the surface temperature of
structure 21 is
hot enough and, preferably, the surface of the wrapped adhesive soft enough to
be
flowable into the interstices on t:he back side of the fabric, no additional
heat may be
required and a good bond formed merely by the pressure contact between the
fabric and
structure 21. If the surface temperature of structure 21 is not hot enough,
heat from a
supplemental heat source, which may be any one of the above described means,
i.e.,
flame burners, electrical resistance heating, radio frequency, infra red,
quartz, ultrasonic,
or plasma jet electrical discharge, may be added to the surface of structure,
21 prior to
application of fabric 20. A press shoe or press roller may be used, if
required, to ensure
good pressure contact between t:he fabric and structure 21.
~.. -'- 2136359
If core 11 is part of a continuous process, as it would be if the core is
extruded
upstream from the processing steps illustrated in Figure 1, a conventional
traveling cut-
off mechanism may be used to separate the continuous formed structure 22 into
discrete
roller lengths suitable, if need be, for further processing such as edge
trimming; see
Figure 7. It should also be noted that if mandrel 10 is stationary and core 11
is to be
rotated, it may be more convenient to use a drive system, such as Ford urine
19; in cont~.ct
with the core 11 at -a location just to the right, i.e., upstream, of the
discharge head 17.
In this arrangement, any possible stretching of the core or other components
which might
occur from the illustrated placement of Ford drive 19 would be eliminated.
If, on the other hand core 11 is a discrete length as it would be if pre-made
and
stored until wrapping is requiredl, a cutting mechanism can be omitted or
performed
sequentially, but separately, from the illustrated forming process.
An alternative form of the invention is illustrated in Figure 2 in which the
adhesive substance is formed as a separate envelope, such as by extrusion
about the core.
A mandrel is illustrated at 30 and a core at 31. The mandrel may rotate,
carrying
the core 31 with it in the direction of the arrow 32. Alternatively, the
mandrel may be
stationary and the core, in effect, pulled in the direction of arrow 32 by a
drive
mechanism, such as a conventional Ford drive system indicated generally at 33
and
located near the end of the processing sequence and after fabric has been
applied.
An adhesive substance, in. this instance an envelope which has, preferably,
though
not necessarily, been extruded at the right end of the processing sequence, is
indicated at
34. The displacement of the adhesive substance envelope 34 away from the 'core
31 has
been somewhat exaggerated to indicate the recent formation thereof and its
capacity for
shrinkage about the core ~ 1 to form a good bond with the core. It should be
understood
that the envelope 34 may be quite structurally sound with only its interior
surface, at
least, heated, or it may be in a mushy or barely self supporting state
depending on its
heat content. Preferably the surface of core 31 is heated, as it would be for
example if it
'g' 2136359
was freshly extruded, or heat may be applied to a room temperature or
insufficiently hot
surface by flame burners, electrical resistance heating, radio frequency,
infra red, quartz;
induction, ultrasonic, the plasma jet system of Figure 1, or any other
suitable form of
heating or surface preparation including chemical priming of the type
disclosed in the
Chemical Priming for Extrusion Coating" by Roger Isbister on page 101-104 of
the May, 1988
issue of the TAPPI Journal:
After adhesion of the envelope 34, whether in structurally solid and strong or
in
near molten condition, to core 31, a base structure 36 is formed. Immediately
after
formation of base structure 36, fabric 35 in strip form is wrapped therearound
in such
fashion that the edges of adjacent wraps abut against one another to form a
peripherally
continuous fabric surface. Again a press roller or press shoe may be employed
to apply
pressure to the fabric-base structure junction. As mentioned above, the fabric
backing
may be heated, though this may not be expedient in all environments. Again, no
supplementary heat may be needed to ensure a good bond between base structure
36
and fabric 35 but it will usually be advantageous to apply supplemental heat
to the
exterior of base structure 36 just upstream of the junction of fabric 35 with
the base
structure to ensure a good bond., If envelope 34 was near molten or very hot
and tacky
when it came in contact with core 31, only a modest amount of supplemental
heat may
be needed to ensure a good bond. Again, the operating parameters will vary
from
installation to installation and the processing sequence disclosed herein will
have to be
adjusted accordingly. If supplemental heat is required, flame burners,
electrical
resistance heating, radio frequency, infra red, quartz, induction, ultrasonic
or jet plasma
heating may be employed, with or without chemical priming, to ensure the
primary
objective of a good bond.
The plasma jet heating system illustrated diagrammatically in Figure 1 is
illustrated in greater detail in Figures 3-S. The discharge head 17 includes a
head
40 having a discharge end 4f. A mounting plate is indicated at 42, the
mounting
plate having a connector 43 which receives the lead 18 which extends from the
power
unit 16. A junction box is indicated at 44, said junction box being secured to
mounting
3,,
~::~ -9- 213b359
plate 42 by bolts 45, and it has two pairs of sockets 46, 47 for auxiliary
uses. A blower is
indicated at 48. It will be understood that said plasma jet system may be of
conventional
construction such as those available from Corotec Corporation, Collinsville,
CT as model
nos. PJ-11, -12, -21, -22, all 120V and 2, 4 or 8 amps at 60Hz. PJ-11 has an
output/discharge of, for example, lOKV, 25mA, and 60Hz. The power unit
converts
incoming single phase 120 volt power to the high voltage necessary for plasma
discharge.
The discharge head utilizes a high performance brushless DC blower which moves
air
across the electrodes at a rate which is controlled and monitored by the power
unit.
Figure 6 illustrates a system having a rotating mandrel 50 on which the
plastic
tube 51 is mounted. A carriage is indicated at 52 which, in Figure 6, is
movable parallel
to the longitudinal axis of the rotating mandrel. The carriage 5 2 includes a
feed
mechanism not shown, for pile fabric strip 53 which is helically wound around
the plastic
tube 51.
Initially a pre-formed plastic tube 51 is mounted over the rotating mandrel 50
and
thereafter the strip of pile fabric; 53 is wound helically over the plastic
tube 51 through
the applicator located on the movable carriage 52.
The fundamental feature of the procedure illustrated in Figures 6-8 for the
manufacture of paint rollers consists of applying a thermoplastic adhesive in
a molten
state onto the area of the plastic: tube 51 where the strip 53 will be closely
wound. It will
be understood that the specific i:hermoplastic adhesive material applied to
the junction
region between the tube and fabric is not critical to the invention. However,
it must be
compatible with the plastic tube selected, the pile fabric and the solvents
contained in
the paint, stain, varnish or shellac as well as the solvents used to clean the
roller if the
roller is the reusable type. The thermoplastic adhesive is applied by the
outlet mouth of
a nozzle 54 mounted over the movable carriage 52, which nozzle 54 is connected
to a
reservoir where the thermoplastic adhesive is heated.
- lo- 2136359
In the embodiment of Figure 7, the plastic tube 51 is mounted over a rotating
roller 55. The plastic tube may be moved longitudinally by a drive unit 5 6
while the
carriage 52 and the rotating roller 55 remain axially fixed.
The systems of Figures 6 ;end 7 each include a cutter 57 which produces the
roller
units in a condition ready for the subsequent assembly of the handle, axis and
cap. In
the embodiment of-Figure 6, the cutter 57 does not move horizontally when
cutting. In
the embodiment of Figure 7 it will be understood that the cutter 57 will be
arranged to
move in synchronism with the horizontal movement of the tube 51 when cutting.
The embodiment of Figure 9 illustrates a system in which a mandrel is not an
essential component, though it may be used as a precautionary measure. A
plurality of
pre-made cores are indicated at ti0 and are fed to the system by a suitable
race and
delivery system, not shown. A support for the continuous core forming station
is
indicated generally at 61, the support including a trough member 62 with which
each
core 60 makes initial contact. A welder is indicated at 63 which functions to
join
adjacent cold tubes 60a and 60b together by a butt weld at joint 64. The
welder may be
a sonic welder, a flame melt welder, or any other type capable of forming a
solid
junction. The welder is moved to the right during the welding process since
the core and
its subsequent accretions move continually to the right as indicated by arrow
65.
A drive system, here a conventional Ford drive, is indicated generally at 66.
Since the cores 60 will either be cold, i.e., at room temperature, or only at
a
slightly elevated temperature, a preheater or surface treater may be required.
Here such
a preheater or surface treater is indicated at 67. It may be any of the above
described
types since its purpose is to condition the surface of the now unitary core 68
to bond
tightly to an adhesive substance. A corona discharge or plasma jet system may
be
especially efficient.
-11- 2136359
An adhesive substance dispenser is indicated generally at 69. The dispenser
dispenses a suitable adhesive substance, such as liquified polypropylene,
polyethylene or
other bond forming substances compatible with the unitary core 68 and the
later applied
pile fabric. In this instance the adhesive substance is dispensed through a
ring type of
S extruder, indicated at 70, which forms a layer of the adhesive substance,
indicated at 71,
on the unitary core 68.
A strip of pile fabric is indicated at 72, the fabric being joined to the
coated core
while the layer 7lof the adhesive substance is still hot and tacky enough to
form a tight
bond with the backing of the falbric. It will be understood that supplemental
heat may
be applied downstream from the extruder 70 and upstream from the core-fabric
junction
if, without it, the outer surface of the layer 7I has cooled, too low to form
a good bo
Another support is indicated generally at 73, this support including a trough
74
which is slightly larger than trough 62 since trough 74 must accommodate the
larger
diameter composite product 75 which includes the layer of adhesive substance
71 and
pile fabric 72. A traveling cut-off is indicated at ~~ 8 .
All of the above describf;d systems produce a composite paint roller due to
the
bonding produced between the plastic tube and the strip of pile fabric,
together with the
interposition of a compatible adhesive substance which is capable of forming a
strong
bond. The exact temperatures used in the processes will of course vary
slightly from
material to material and other factors unique to a specific operation as will
be readily
apparent to one skilled in the art.
The preferred adhesive substances include polypropylene, polyethylene, a
mixture
of polypropylene and polyethylene, one preferred mixture having a
polypropylene:polyethylene ratio of about 80:20, polyanude or a mixture of
polyamides,
polyolefin based compounds, polyester based compounds, polyurethane based
compounds, polyamide "hot meld" adhesives sold under the designations HB
Fuller 6542
PEL and HL2021 and Hot Melv~'2167PL as well as other suitable adhesives
compatible
*Trademark
-12-
with a plastic tube which may be fabricated from polypropylene. Alternative
materials
for fabricating the core include other polymeric materials including
polyethylene, a
mixture of polyethylene and polypropylene, polyethylene with added talc,
polyester and
other plastics. The adhesive substance must also be compatible with the
plastic tube and
the pile fabric, and be resistant to the anticipated solvents used in
connection with
painting. These solvents include water, water with ammonia, soapy water,
mineral
spirits,' turpentine, aromatic compounds, aliphatic compounds, alcohols,
ketones, acetone,
toluene, chlorinated hydrocarbons and other solvents foreseeably used with
paint,
including both water and oil based paints, shellac and varnish.
Although several embodiments of the invention have been illustrated and
described, it will at once be apparent to those skilled in the art that
modifications and
improvements may be made within the scope of the invention. Accordingly it is
intended
that the scope of the invention not be limited by the foregoing exemplary,
description, but
only by the hereafter appended claims.
