Note: Descriptions are shown in the official language in which they were submitted.
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METHODS AND APPARATUS FOR MAKING PAINT ROLLER COVERS WITH
THERMOPLASTIC CORES
FIELD OF THE INVENTION
The present invention relates to methods and
apparatus for making roller covers by adhering a roller
fabric to a thermoplastic tubular form by means of an
extruded thermoplastic film that is spirally wrapped onto
the tubular form immediately prior to the roller fabric.
BACKGROUND OF THE INVENTION
It is generally known to make paint roller covers
with thermoplastic cores. Making the cores out of a
thermoplastic material has the advantage that the cores will
not delaminate even after prolonged soaking as is the case
with most cardboard cores. However, there may still be a
problem with the roller fabric prematurely separating from
thermoplastic cores, either because the adhesive does not
provide a very effective bond between the fabric backing and
cores, or the adhesive does not hold up after prolonged
soaking in certain types of solvents.
SUMMARY OF THE INVENTION
The present invention relates to methods and
apparatus for making paint roller covers which are
completely impervious to water and most solvents, even after
prolonged soaking.
In accordance with a broad aspect, the invention
provides a method of making roller covers comprising the
steps of spirally wrapping a continuous length of
thermoplastic core strip material around a mandrel while
positioning a spacer between adjacent edges of each
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successive wrap of the core strip material around the
mandrel to prevent such adjacent edges of the core strip
material from overlapping each other on the mandrel thus
forming a spiral seam between the adjacent edges of the core
strip material, applying a layer of adhesive on the spirally
wrapped core strip material, and spirally wrapping a fabric
strip over the adhesive layer to bond the fabric strip to
the core strip material.
In accordance with another broad aspect, the
invention provides an apparatus for making roller covers
comprising means for spirally wrapping a continuous length
of thermoplastic core strip material around a mandrel, a
spacer positioned between adjacent edges of each successive
wrap of the core strip material around the mandrel to
prevent such adjacent edges of the core strip material from
overlapping each other to provide a spiral seam between such
adjacent edges, means for applying a layer of adhesive over
the spirally wrapped core strip material, and means for
spirally wrapping a fabric strip over the adhesive layer to
bond the fabric strip to the core strip material.
In accordance with one aspect of the invention,
the roller cores are made of a thermoplastic material, and
the roller fabric is permanently bonded to the roller cores
by means of a thermoplastic film that is completely
impervious to water and most solvents, even after prolonged
soaking.
In accordance with another aspect of the
invention, the roller covers are made by spirally wrapping a
strip of hot thermoplastic film
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= ,r
onto an exterior surface of a thermoplastic tubular form and spirally
wrapping a strip of fabric having a thermoplastic backing onto the spiral
wound strip of thermoplastic film while the thermoplastic film is still
sufficiently hot to cause the thermoplastic film to flow into interstices in
the thermoplastic backing of the fabric and bond the fabric to the exterior
surface of the tubular form.
In accordance with another aspect of the invention, a continuous
strip of thermoplastic core material is spirally wrapped around a mandrel,
then a hot thermoplastic film is spirally wrapped around the spirally
wrapped core material, and a fabric strip is spirally wrapped around the
thermoplastic film while the thermoplastic film is sufficiently hot to bond
the fabric strip to the core material.
In accordance with another aspect of the invention, a spacer
member is positioned between adjacent edges of each successive wrap of
the core strip material around the mandrel to prevent the adjacent edges
of the core strip material from overlapping each other on the mandrel
thereby forming a spiral seam along the length of the core material.
In accordance with another aspect of the invention, the spacer
member is free to move to a limited extent in a direction parallel to the
longitudinal axis of the mandrel to compensate for slight changes in the
helix angle of the spiral wrap of core strip material on the mandrel.
In accordance with another aspect of the invention, adjacent edges
of the hot thermoplastic film are overlapped over the spiral seam between
adjacent edges of the thermoplastic core strip material to provide enough
film material to flow into the spiral seam and also into interstices in the
backing of the fabric to form a strong bond between the fabric strip and
core strip material along the length of the spiral seam.
In accordance with another aspect of the invention, the
thermoplastic backing may include relatively long nylon or other
thermoplastic filaments extending lengthwise of the fabric strip.
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In accordance with another aspect of the invention, a first driven
belt drivingly may engage the fabric strip to spirally advance the fabric
strip and underlying core strip material along the length of the mandrel.
Also, a second drive belt may drivingly engage the core strip material
upstream of where the hot thermoplastic film is applied to the core strip
material to assist in spirally advancing the core strip material and fabric
strip along the length of the mandrel.
In accordance with another aspect of the invention, different
diameter capstans may be used to drive both driven belts at different
speeds to compensate for the different outer diameters of the spiral
wraps of fabric strip and core strip material on the mandrel so that both
driven belts spirally advance the fabric strip and core strip material at the
same speed on the mandrel.
In accordance with another aspect of the invention, separate
electronically coupled drives may be used to drive both driven belts to
compensate for the different outer diameters of the spiral wraps of fabric
strip and core strip material on the mandrel so that both driven belts
spirally advance the fabric strip and core strip material at the same speed
on the mandrel.
These and other objects, advantages, features and aspects of the
present invention will become apparent as the following description
proceeds.
To the accomplishment of the foregoing and related ends, the
invention, then, comprises the features hereinafter fully described and
particularly pointed out in the claims, the following description and the
annexed drawings setting forth in detail certain illustrative embodiments
of the invention, these being indicative, however, of but several of the
various ways in which the principles of the invention may be employed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the annexed drawings:
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Fig. 1 is an enlarged perspective view of one form of paint roller
cover made in accordance with this invention;
Fig. 2 is an enlarged transverse section through the paint roller
cover of Fig. 1, taken generally along the plane of the line 2-2 thereof;
Fig. 3 is a schematic top plan view of one form of apparatus for
making the paint roller covers of Figs. 1 and 2;
Fig. 4 is an enlarged schematic fragmentary side elevation view of
the automatic tube feed mechanism of the apparatus of Fig. 3;
Fig. 5 is an enlarged fragmentary side elevation view of the
mandrel used in such apparatus;
Fig. 6 is an enlarged schematic side elevation view of the portion
of the apparatus of Fig. 3 at which the bonding film and fabric are spirally
wrapped onto the tubular core material;
Fig. 7 is an enlarged schematic side elevation view of the cutter
assembly and dead stop of such apparatus;
Fig. 8 is an enlarged fragmentary longitudinal section through
another form of paint roller cover made in accordance with this invention;
Fig. 9 is a schematic top plan view of another form of apparatus
for making the paint roller covers of Fig. 8;
Fig. 10 is an enlarged schematic top plan view of the core strip
edge spacer of the apparatus of Fig. 9 which prevents the adjacent core
strip edges from overlapping each other during spiral wrapping of the core
strip material onto the mandrel;
Fig. 11 is an enlarged schematic top plan view of a portion of the
apparatus of Fig. 9 showing the hot thermoplastic film being drawn from
an extruder die head and spirally wrapped around the outer surface of the
spirally wrapped core strip material with the adjacent edges of the hot
thermoplastic film overlapping each other over the spiral seam of the core
strip material;
Fig. 12 is a schematic top plan view of a modified form of the
apparatus of Fig. 9 which includes the same driven belt for drivingly
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engaging the fabric strip and a second driven belt for drivingly engaging
the core strip material upstream of the extruder die head;
Fig. 13 is an enlarged fragmentary schematic plan view of the
woven backing of one form of fabric strip used to make roller covers in
accordance with this invention; and
Figs. 14 and 15 schematically show two different drives for driving
two belt drives at different speeds to compensate for the different outer
diameters of core strip material and high pile fabric strip driven thereby.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings, and initially to Figs. 1 and
2, one form of paint roller cover in accordance with this invention is
generally indicated at 1 and includes a tubular thermoplastic core 2
having a uniformly thick layer of bonding film 3 on the exterior surface
thereof for permanently bonding a suitable fabric 4 to the core.
The core 2 may be made of any suitable crystalline or semi-
crystalline polyolefin polymer such as natural and filled polypropylene and
high density polyethylene. A presently preferred polyolefin polymer is a
polypropylene copolymer comprising anywhere from approximately 90 to
96% polypropylene and 4 to 10% ethylene monomer, with approximately
93% polypropylene and 7% ethylene monomer being preferred. Also, the
polyolefin copolymer used for the core material desirably has a melt flow
rate of between approximately .3 and .7 dg./min. Polypropylene has
excellent chemical resistance to solvents and water and has an overall
toughness. Ethylene monomer is added to the polypropylene in small
amounts for higher impact strength, to allow the core to be subjected to
low temperatures or sharp impacts without breakage, and for ease of
extruding the material into the desired tubular shape and precisely cutting
the tubing into the desired individual paint roller lengths.
The fabric 4 may be a conventional roller fabric that preferably has
a heavy open weave thermoplastic backing 5 woven into the fabric to
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allow for a superior mechanical bond between the fabric backing and
bonding film 3. The fabric pile or nap 6 may be made of different
materials or blends and be of different heights depending on the particular
application. The thermoplastic bonding film 3 should be compatible with
both the core material and the fabric backing in order to achieve a
permanent bond therebetween. In the case where the core material is a
polypropylene copolymer, the bonding film is desirably made of
polypropylene and the fabric backing is made of a suitable thermoplastic
such as polyester or polypropylene. Also, the polypropylene bonding film
desirably has a melt flow rate of between approximately 30 and 45
dg./min. with a melt flow rate of approximately 40 being preferred and
with good melt strength, to allow the material to be extruded into a film
of the desired thickness and width and spirally wrapped onto the tubular
core material immediately prior to spirally wrapping the fabric onto the
core material to permanently bond the fabric to the core material as
described hereafter.
During the manufacturing process, hot bonding film 3 of the
desired thickness and width is drawn from an extruder equipped with a
coat hanger die and spirally wrapped around the extruded tubular core
material 2. Within approximately one turn of wrapping the hot bonding
film onto the tubular core material, a strip of the fabric material 4 having
substantially the same width as the bonding film is spirally wrapped
around the bonding film to permanently bond the fabric strip to the
tubular core material.
In order to be able to spirally wrap the hot bonding film and fabric
onto the exterior surface of the tubular core material and still maintain the
desired tubular shape and integrity of the tubular core material, the
tubular core material desirably has a wall thickness of between
approximately .030 and .070 inch, with a thickness of approximately
.060 inch being preferred. Also, the layer of bonding film on the tubular
core material desirably has a thickness of between approximately .010
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and .030 inch, with a thickness of approximately .020 inch being
preferred, to ensure that there is enough bonding material and latent heat
in the bonding material to allow the bonding material to flow into the
interstices in the fabric backing and obtain the desired mechanical and
chemical bond between the bonding film and fabric backing.
The first step in making paint roller covers shown in Figs. 1 and 2
in accordance with the present invention is to provide a supply of
extruded tubes 10 of the thermoplastic core material cut to the desired
length, for example, 65 inches. Before the fabric material is applied to
the extruded tubes, the tubes are stored in a vertical position for a
minimum length of time after manufacture, for example 24 hours, to give
the tubes sufficient time to normalize, crystallize, shrink and stabilize.
After the tubes 10 have been stored for a sufficient length of time,
they are loaded into a hopper 11, schematically shown in Fig. 3.
Connected to the hopper 11 is a vertical conveyor 12 schematically
shown in Fig. 4, for continuously feeding the tubes, one at a time, into a
plastic tube spiraling machine/apparatus 14. As the tubes are
continuously fed through the apparatus, the apparatus spirally wraps the
bonding film and fabric onto the tubes and permanently bonds the fabric
to the exterior surface of the tubes. Thereafter the fabric wrapped tubes
are sufficiently cooled to permit them to be separated from each other
and discharged from the apparatus as described hereafter.
The tubes 10 that are loaded into the hopper 11 are picked up by
the vertical conveyor 12 (see Fig. 4) and discharged into a track 16 that
feeds the tubes, one at a time, onto a trough assembly 17. From there
the tubes 10 are pushed axially onto a floating tube mandrel 18 by a
tube ram 19 that is movable axially along the length of the trough 17
from one end to the other.
The mandrel 18 supports the tubes 10 during the spiral wrapping
of both the bonding film and fabric onto the tubes as described hereafter,
and is desirably of considerable length, for example 195 1/4 inches, for
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supporting three 65 inch length tubes on the mandrel at any given time.
Moreover, the mandrel desirably comprises a plurality of tubular sections
made for example of extruded aluminum and suitably connected together
at their ends.
In the preferred embodiment shown in Figs. 3-6, the mandrel 18 is
made up of five sections 20-24 (see Fig. 5). The first two sections 20
and 21 (as viewed from the upstream end of the apparatus in the
direction of the downstream end) have a length of approximately 37 1/8
inches and 30 3/8 inches, respectively (for a combined length of
approximately 67 1/2 inches), and are connected together at their ends by
a bearing sleeve 25 that permits relative rotation between sections. The
third section 22 has a length of approximately 33 3/4 inches and is
connected to the second section 21 by a connector plug 26 that defines
a notch or groove 27 between such sections for releasable engagement
by a mandrel stop 28 (see Fig. 4) which when engaged prevents axial
movement of the mandrel.
A similar notch or groove 29 is formed by the shaft 30 of a tube
guide 31 extending into the upstream end of the first mandrel section 20
for releasable engagement by another mandrel stop 32.
The fourth and fifth mandrel sections 23 and 24 are each
approximately 45 3/4 and 48 1/4 inches long, respectively, and are
connected together and to the third section 22 by bearing sleeves 25 to
provide rotatable connections therebetween, similar to the rotatable
connection between the first two sections 20, 21.
The mandrel 18 terminates immediately downstream of the zone A
(see Fig. 3) of the apparatus 14 at which the bonding film 3 and fabric 4
are spirally wrapped onto the tubing 10. Moreover, the mandrel 18
desirably includes a stepped portion 35 in this zone or area A having a
greater outer diameter than the remaining length of the mandrel to bring
the mandrel to a size that more closely matches the inner diameter of the
tubes to provide better support for the tubes at the critical point where
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the bonding film and fabric are applied to the tubes. This stepped portion
35 of the mandrel may, for example, have an outer diameter of
approximately 1.473 inches where the inner diameter of the raw tubes
is approximately 1.5 inches and an axial length of approximately 13
5 inches. The outer diameter of the remaining length of the mandrel
including a 6 inch length 36 at the downstream-most end of the mandrel
is desirably somewhat less, for example, approximately 1.437 inches, to
provide a greater clearance between the outer diameter of the mandrel
and inner diameter of the tubes over the majority of the length of the
10 mandrel to reduce the drag on the tubes when the tubes are driven both
rotationally and axially relative to the mandrel by planetary drive
assemblies as described hereafter.
In order to be able to push the tubes 10 onto the first two mandrel
sections 20, 21 by the tube ram 19, the upstream mandrel stop 32 must
be disengaged from the mandrel 18 so as not to interfere with the tube
movement onto such mandrel sections. At the same time, the
downstream mandrel stop 28 should engage the mandrel to prevent the
mandrel from moving axially. If the two mandrel stops 28, 32 should
ever be simultaneously disengaged from the mandrel, the mandrel may
start to travel down the line, in which event a metal detector 37 located
immediately downstream of the bonding film and fabric application zone
A (see Fig. 3) will sense the mandrel movement and automatically shut
the apparatus down to prevent any damage to the apparatus further
downstream of the metal detector.
Once a tube 10 is slid into place on the first two mandrel sections
20, 21, the upstream mandrel stop 32 is engaged and the downstream
mandrel stop 28 is disengaged to permit a tube stripper 38 to engage the
trailing (upstream) end of the tube and push the tube axially downstream
onto the third mandrel section 22 where the tube is engaged by one of
several planetary drive assemblies 39 that propel the tubes both axially
and rotationally through the apparatus.
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After the trailing end of a tube 10 clears the downstream mandrel
stop 28, the downstream mandrel stop 28 is reengaged and the upstream
mandrel stop 32 is disengaged to permit the next tube 10 to be pushed
onto the first two mandrel sections 20, 21. Thereafter the upstream
mandrel stop 32 is reengaged and the downstream mandrel stop 28 is
disengaged to permit the next length of tube to be pushed onto the third
mandrel section 22 and into abutting engagement with the trailing end of
the previous tube, and so on. Two such tubes 10 are schematically
shown in butting end to end engagement with each other in Fig. 6.
A plurality of axially spaced apart tube support rollers 40 support
the mandrel sections 20, 21 and 22 and surrounding tubes 10 upstream
of the first planetary drive assembly 39 (see Fig. 4).
Immediately upstream of the fabric and bonding film application
zone A are a series of alignment rollers 41 through which the tubing
passes just prior to spirally wrapping the bonding film and fabric strip
material onto the tubing (see Figs. 3 and 6). As the rotating and axially
advancing tubing passes through the fabric and bonding film application
zone A, hot bonding film 3 is laid down on the exterior surface of the
tubing at a desired helix angle by the die head 42 of an extruder 43
equipped with a coat hanger die as aforesaid. The axial and rotational
movement of the tubing causes the bonding film 3 to be spirally wrapped
onto the tubing with the side edges 44 of the bonding film in close
butting engagement with each other (see Fig. 6) while a constant tension
is applied to the bonding film to obtain the desired uniform thickness and
width of bonding film on the tubing.
Within approximately the next turn of the bonding film, a fabric
strip 4 having substantially the same width as the bonding film is spirally
wrapped onto the bonding film at substantially the same helix angle as
the bonding film and with the side edges 45 of the fabric strip also in
close abutting engagement with each other.
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In one form of the invention, where the tubing 10 is extruded out
of a polypropylene copolymer having an inner diameter of approximately
1.5 inch and a wall thickness of approximately .060 inch, and the fabric
strip 4 has a width of approximately 2 7/8 inches and a heavy open
weave backing 5 made of a compatible thermoplastic material, a
polypropylene bonding film 3 is drawn down from a width of
approximately 4 inches and a thickness of approximately .057 inch at the
extruder die opening to a width of approximately 2 3/4 inches and film
thickness of approximately .020 inch as the bonding film is spirally
wrapped onto the tubing. When the bonding film comes into contact
with the tubing and as the fabric is spirally wrapped around the bonding
film, the bonding film is still at a relatively high temperature, for example,
between approximately 475 and 500 F. At this temperature, the
latent heat in the bonding film is sufficient to cause the bonding film to
flow into the interstices in the fabric backing and permanently bond the
fabric to the tubing. Preferably, the fabric seams 46 are located between
the bonding film seams 47 when the fabric is spirally wrapped onto the
tubing.
The fabric 4 comes in various lengths, for example, 100 feet
lengths. Accordingly, the ends of the fabric must be spliced together in
order to provide a continuous supply of fabric to the tubing as the tubing
is continuously advanced through the apparatus. As the fabric is spirally
wrapped around the tubing/bonding film, a predetermined amount of
tension is maintained on the fabric to ensure that the fabric is tightly
wrapped around the tubing and the bonding film flows into the interstices
in the fabric backing to provide a permanent bond between the fabric and
tubing.
Air nozzles 50 (see Fig. 6) located adjacent the side edges of the
fabric direct a flow of air against the fabric side edges to cause the fabric
pile/nap 6 to stand up along the side edges. In addition, a helically
shaped fabric guide 52 extends approximately 360 around the tubing at
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the same helix angle as the fabric edge and picks up the fabric pile/nap 6
on the entry/upstream side and terminates at the butt joint where the
fabric edges come together. This helps to form the fabric into the desired
curl with the edges of the fabric pile/nap standing up so the pile/nap does
not get caught between or underneath the abutting fabric edges. The
helical fabric guide 52 is supported by a mounting bracket 53 connected
to the fabric guide on the underneath side thereof as schematically shown
in Fig. 6.
A set of elliptically shaped rollers 55, which may either be spring or
air operated, is located immediately downstream of where the fabric is
spirally wrapped onto the tubing to apply a preset pressure across the
entire width of the fabric to ensure an even, uniform adherence of the
fabric to the tubing over substantially the entire surface area of the fabric.
A third roller 56, which may also be air or spring actuated, is positioned
right where the fabric seam 46 initially comes together to ensure uniform
adherence of the fabric to the tubing along the fabric seam. This has the
benefit that when the tubing is subsequently cut into individual paint
roller lengths, if a cut should occur across a fabric seam, the edge of the
fabric will not pull away from the tubing.
As previously indicated, the tubing is internally supported by the
enlarged diameter stepped portion 35 of the mandrel 18 during the spiral
wrapping of both the hot bonding film 3 and fabric 4 onto the tubing.
Also, the spiral wrapped tubing is internally supported by the mandrel
during the application of a preset pressure to the fabric by the seam roller
56 and elliptical rollers 55 immediately after the fabric is wrapped onto
the tubing.
Beyond that point, the fabric covered tubing is no longer internally
supported. Instead, the fabric covered tubing is only supported on the
exterior by additional planetary drive assemblies 58 and roller guide
assemblies 59 strategically located along the length of the apparatus
downstream of the pressure rollers 55. In addition, a set of alignment
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rollers 57 for the fabric covered tubing are positioned downstream of the
pressure rollers 55 which cooperate with the tube alignment rollers 41
immediately upstream of where the bonding film and fabric are spirally
wrapped onto the tubing to assist in maintaining proper alignment of the
tubing during application of the bonding film and fabric to the tubing.
All of the planetary drive assemblies 39 and 58 (i.e., those
downstream of where the bonding film and fabric are applied to the
tubing as well as those upstream thereof) are driven from a common
power supply unit 60 by two input shafts 61, 62 (see Fig. 3), one of
which controls the axial speed of the tubing, and the other of which
controls the rotational speed. The ratio of these two speeds defines the
helix angle at which the fabric (as well as the bonding film) is wrapped
onto the tubing, which is critical in producing a good butt joint between
adjacent fabric wraps. Should a gap start to develop between adjacent
fabric wraps, this can be corrected simply by changing one of the speeds
of the two input shafts 61, 62 to close the helix angle. Conversely,
should an overlap start to develop between adjacent fabric wraps, this
can be corrected by changing one of the speeds of the two input shafts
61, 62 to open the helix angle.
The planetary drive assemblies 58 downstream of where the
bonding film and fabric are applied to the tubing may be substantially the
same as the upstream planetary drive assemblies 39 except that the
upstream planetary drive assemblies 39 include three sets of tires which
engage the exterior surface of the tubing and propel the tubing both
axially and rotationally, whereas the downstream planetary drive
assemblies 58 include three sets of pinwheels which grip the fabric to
propel the tubing both axially and rotationally.
After the fabric strip has been spirally wrapped and rolled onto the
tubing, the temperature of the fabric covered tubing is still relatively hot,
in the range of 350 to 400 F., which is too hot to separate the tubes 10
from each other by cutting through the fabric at the ends of the tubes.
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Preferably the tubes are cooled down to a temperature of no more than
approximately 200 F. before the tubes are cut apart. Thus, it is
important to cool the tubes down as rapidly as possible after the fabric
strip is adhered to the tubes to maximize the production output of the
apparatus.
In the form of the invention shown in Figs. 1-7, cooling of the
fabric covered tubing is accelerated by supplying cool/air conditioned air
to one or more manifolds 65 located between various planetary drive
assemblies 58 downstream of where the fabric is applied to the tubing as
schematically shown in Fig. 3. One or more air conditioning units 66 may
be used to supply cool air through air ducts 67 to the same or different
manifolds 65 as desired. The ends of the manifolds 65 are of course
open to allow for unobstructed movement of the fabric covered tubing
through the manifolds.
After the fabric covered tubing is sufficiently cooled, the tubing
passes through a cutter assembly 70 (see Figs. 3 and 7) that moves
axially at the same lineal speed as the tubing for a very short distance, for
example, approximately 1 inch, while making a cut through the fabric
between the ends of the tubes.
Operation of the cutter assembly 70 is controlled by a dead stop
71 which, as best seen in Fig. 7, includes a target 72 in coaxial alignment
with the tubing downstream of the cutter assembly. The target 72 is
spaced from the cutter mechanism 70 a distance corresponding to each
individual length of tubing 10 (in this case 65 inches). Accordingly, when
the downstream-most end of the tubing engages the target 72, both the
dead stop 71 and cutter mechanism 70 which is tied to the dead stop
through a tie rod assembly 73, are caused to move a very short distance,
for example approximately 1 inch, during which the cutter blades move
radially inward to cut through the fabric between a pair of tube ends.
After the dead stop 71 moves the short distance required for the
cutter mechanism 70 to cut through the fabric between a pair of tube
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ends, the target 72 pivots out of the way above the tube that was just
separated from the remaining tubing as schematically shown in phantom
lines in Fig. 7 to permit the leading end of the separated tube to move
past the target to the position also shown in phantom lines in Fig. 7
where the tube is free to be pushed sideways by an air actuated push rod
74 to cause the tube to be discharged down a chute 75 into a discharge
hopper 76 (see Fig. 3).
As soon as the target 72 pivots out of the way, both the dead stop
71 and cutoff mechanism 70 move back to their original starting
positions shown in solid lines in Fig. 7. Also, as soon as the separated
tube 10 has been discharged onto the discharge chute 75, the target 72
repositions itself for reengagement by the leading end of the next length
of tubing and the cutting cycle is repeated.
While the lengths of tubes 10 are in the discharge hopper 76, both
ends of the tubes may be inspected for any possible types of defects.
Following inspection, the tubes are taken out of the hopper and stacked
on end until the fabric covered tubes are uniformly cooled throughout
their length. It is important to cool the tubes at a uniform rate over their
entire length while the tubes are standing on end to ensure that the tubes
stay round during cooling. The tubes are desirably stood on end for a day
or two to allow the tubular core material to crystallize for strength before
the tubes are cut into individual paint rollers having a length for example
of nine inches.
Fig. 8 is an enlarged fragmentary longitudinal section through
another form of paint roller cover 80 in accordance with this invention
which, like the paint roller cover 1 shown in Figs. 1 and 2, includes a
thermoplastic core 81 having an adhesive bonding film 82 on the exterior
surface thereof for permanently bonding a suitable fabric 4 to the core.
However, in the manufacture of paint roller covers 80 of the type shown
in Fig. 8, instead of using extruded tubes for the core as in the Figs. 1
and 2 embodiment, the core 81 is formed by spirally wrapping a single
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continuous strip or ply 84 of thermoplastic core material, preferably
polypropylene, around a stationary mandrel with the adjacent edges 85
of the core strip 84 in closely spaced but non-overlapping relation to each
other as described hereafter.
It is important that the edges 85 of the single ply core strip
material 84 not overlap each other, since overlapping edges would
produce an uneven inner core surface 86 making it difficult to support the
paint roller cover internally on a roller frame. Also overlapping core strip
edges would produce an uneven outer core surface 87 resulting in uneven
application of paint when the roller cover 80 is rolled on a surface such as
a wall or ceiling.
By the same token, it is important that not too much of a gap 88
be left between the core strip edges 85 during the roller cover
manufacturing process, since too wide a gap could adversely affect the
structural integrity of the core and greatly reduce the crush strength of
the roller cover 80.
To prevent adjacent edges 85 of the core strip material 84 from
overlapping each other during the manufacturing process but still ensure
the structural integrity of the core 81 so the roller cover 80 has good
crush strength when a rolling force is applied to the roller cover during
application of paint or other liquid coating to a wall or other surface, a
gap 88 preferably of no more than .050 inch and more preferably within
the range of .010 inch to .015 inch is maintained between the core strip
edges during the roller cover manufacturing process. This may be
accomplished in accordance with the present invention by positioning a
core strip edge tracking spacer or stylus 90 between adjacent edges 85
of each successive wrap 91 of the core strip material 84 around a
stationary mandrel 92 of a roller cover manufacturing apparatus 93 to
maintain a minimum gap 88 between the core strip edges as
schematically shown in Figs. 9 and 10. The spacer 90 may be a
relatively thin cylindrical pin or blade of the requisite diameter or
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thickness, and is supported adjacent the outer diameter of the mandrel 92
as by means of an angle bracket 94 that maintains a clearance space of
for example .005 inch to .008 inch between the tip 95 of the spacer and
the outer diameter of the mandrel (see Fig.10). If desired, the spacer 90
may also be threadedly connected to the angle bracket 94 to permit
limited movement of the spacer toward and away from the exterior
surface of the mandrel to adjust the clearance space therebetween.
To ensure that the spacer 90 will follow or track along between the
adjacent core strip edges 85 and compensate for any slight changes in
the helix angle of the spiral wrap of core strip material around the
mandrel, the spacer mounting bracket 94 is supported as by means of a
pair of guide rods 95 slidably received in guides 96 in a fixed support 97.
This allows the spacer to freely float or move in a linear direction parallel
to the axis of the mandrel a limited distance, for example, approximately
1 1 /2 inches.
During startup of the paint roller 80 manufacturing process
schematically shown in Fig. 9, a single strip 84 of thermoplastic core
material, preferably polypropylene, of the desired width and thickness, is
fed over the stationary mandrel 92 from one side at a desired helix angle.
Then a sufficient number of turns of the core strip material are manually
wrapped around the mandrel to extend beyond the core strip edge spacer
90 and an extruder die head 100 for the hot thermoplastic bonding film
82 a sufficient distance to allow the fabric strip material 4 to be
subsequently manually wrapped around the leading end of the core strip
material 84 at the same helix angle. The fabric strip 4 is preferably fed
under the mandrel 92 from the other side with the fabric backing side 5
up and is manually wrapped around the mandrel a sufficient distance to
allow a belt drive 102 to be tightly wrapped about the fabric strip on the
mandrel. Belt drive 102, when driven by driving one of two rollers 103,
104 about which the belt drive is also wrapped, will cause the fabric and
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core strips 4 and 84 to spirally advance along the mandrel 92 in a manner
well known in the art.
Since the extruder die head 100 is also shown located on the other
side of the mandrel 92 from the core strip 84, the extruder die head will
feed the hot thermoplastic bonding film 82 under the mandrel and onto
the core strip material immediately upstream of the point at which the
fabric strip 4 is spirally wrapped around the core strip material.
Fabric strip 4 may have a width substantially the same as the core
strip material 84. By contrast, the bonding film 82 desirably has a width
somewhat greater than the core strip material to allow the adjacent edges
105 of the bonding film to be overlapped outwardly of the spiral gap or
seam 88 that is formed between the adjacent edges of the spiral wrapped
core strip material as schematically shown in Fig. 11. This provides
additional bonding film 82 over the spiral seam 88 for flow of the bonding
film into the spiral seam as schematically shown in Fig. 8 as well as into
the interstices in the fabric backing 5 to form a relatively strong joint over
the spiral seam.
Typically the fabric 4 used to make roller covers with thermoplastic
cores has a backing 5 made of woven polyester filaments that are
relatively short both widthwise and lengthwise of the fabric. However,
the fabric 4 used to make the roller covers 80 shown in Fig. 8 preferably
has a fabric backing 5 made of relatively long thermoplastic filaments
108, preferably nylon, running along the length of the fabric strip and
relatively short polyester or other thermoplastic filaments 109 running
across the width of the fabric strip as schematically shown in Fig. 13.
The nylon filaments 108 are much stronger than the polyester filaments
109 and are of a much greater length, which greatly increases the
strength of the fabric backing, preventing the fabric backing from tearing
along the seam line 88 of the spiral wound core 81.
Fig. 12 shows a modified form of apparatus 93' for making the
roller cover 80 of Fig. 8 which is substantially the same as that shown in
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Figs. 9 through 11. Accordingly, the same reference numbers followed
by a prime symbol (') are used to designate like parts. The apparatus 93'
shown in Fig. 12 differs from that shown in Figs. 9-1 1 in that a second
belt drive 110 is provided between the spacer mechanism 90' and
extrusion die head 100' for directly driving the core strip material 84 to
assist in advancing the core strip material and fabric strip 4 along the
mandrel 92'. This second belt drive 110 is particularly helpful in
providing better control of the movement of the core strip material and
fabric strip along the mandrel especially when using relatively high pile
fabrics.
The different outer diameters of the core strip material 84 and high
pile fabric strip 4 on the mandrel 92' can be compensated for as by
making the drive capstan 1 1 1 for the core strip material belt drive 1 10
somewhat larger in diameter than the capstan 103' for the fabric belt
drive 102' so the core strip material and fabric can be driven by a
common drive motor 1 12 at the same speed as schematically shown in
Fig. 14. Alternatively, two separate drive motors 116, 1 18 may be tied
together electronically through a suitable controller 1 19 for driving
respective capstans 103' and 1 1 1 of the same diameter to synchronize or
match the speeds of the core strip material and fabric on the mandrel.
The belt drive 102', which drivingly engages the fabric strip 4
immediately downstream of where the fabric strip is spirally wrapped
around the bonding film 82, applies a uniform pressure to the outer
surface of the fabric as the fabric passes through the belt drive 102 to
ensure an even, uniform adherence of the fabric to the core strip material
over substantially the entire surface area of the fabric.
During manufacture of the roller cover 80 shown in Fig. 8, bonding
film 82 is only applied to the core strip material 84 after the core strip
material has been wound onto the mandrel 92 or 92' and just before the
fabric strip is wound around the bonding film. Thus, the entire roller
cover 80 is formed in a single step as the fabric is spirally wrapped about
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the bonding film. This eliminates the need to provide a completely
formed core before applying the bonding film and fabric to the core strip
material.
The core strip material 84 is internally supported by the stationary
mandrel 92 or 92' during the entire roller cover manufacturing process up
until the time the fabric covered core strip material is sufficiently cooled
and cut to the desired length, for example, 65 inches, using a flying shear
120 or 120' (see Figs. 9 and 12). Thereafter the fabric covered core
strip material is removed from the outboard end of the mandrel for further
finishing into individual paint roller covers having a length for example of
7 or 9 inches, in a manner well known in the art.
Although the invention has been shown and described with respect
to certain preferred embodiments, it is obvious that equivalent alterations
and modifications will occur to others skilled in the art upon the reading
and understanding of the specification. The present invention includes all
such equivalent alterations and modifications, and is limited only by the
scope of the claims.
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