Abrasive flap brush and method and apparatus for making same

An abrasive flap brush including a central core, a layer of adhesive disposed on the peripheral surface of the core by a coater, and a plurality of abrasive flaps adhered to the core by the adhesive. The adhesive is uniformly distributed around the core by providing either the core or the adhesive coater with spacing projections that maintain a predetermined minimum distance between the coater and the core when the adhesive is applied. A coater including the spacing projections is also disclosed, as is a method for making an abrasive flap brush.

TECHNICAL FIELD 
The present invention relates to an abrasive flap brush having a central 
core to which is adhered a plurality of abrasive flaps, and more 
particularly to a means, process, and apparatus for providing an 
adequately uniform layer of adhesive to the central core to adhere 
substantially all of the flaps. 
BACKGROUND OF THE INVENTION 
Abrasive flap brushes are surface conditioning tools that include a central 
core and a plurality of radially extending strips, or flaps, of abrasive 
material. The abrasive flaps are each adhered to the core at one end of 
the flap, such that an opposed end of each flap is presented for contact 
with a workpiece surface when the core is rotated. Flap brushes of this 
construction are useful in the surface preparation and conditioning of 
metals, wood, plastics, and other materials to prepare the surface for 
painting, plating, or other subsequent processes. Flap brushes are also 
useful for imparting a desired finish to a surface of a workpiece. 
FIG. 1 is a perspective view of a conventional flap brush 10, including a 
cylindrical central core 12, a layer of adhesive 16 coated on the outer 
peripheral surface 14 of the core, and a plurality of radially extending 
abrasive flaps 18. The cylindrical core 12 is typically a paper and 
phenolic resin composite or a polyester and glass fiber composite. The 
adhesive 16 may be, for example, an epoxy, and is coated over the outer 
surface 14 of the core to adhere the abrasive flaps 18 to the core 12. The 
abrasive flaps 18 may be nonwoven materials comprising staple fibers, 
abrasive particles, and a curable binder for bonding the particles to the 
nonwoven fibers. Flaps 18 are adhered at core end 20 to core 12 by the 
adhesive layer 16. The flaps 18 extend radially outwardly from the core 
12, and are typically tightly packed to minimize relative movement between 
adjacent abrasive flaps. For example, in an abrasive flap brush having a 
15.2 cm (6 in) outer diameter and including one hundred and twenty eight 
nonwoven abrasive flaps, the flaps 18 can be compressed at the core end 20 
to approximately 10% of their uncompressed thickness and at their outer 
end 22 to about 30% of their uncompressed thickness. In this arrangement, 
the outer ends 22 of each of the abrasive flaps together form a flap brush 
outer peripheral surface 24, which may be rotatively applied to a 
workpiece surface. An example of a flap brush 10 of the foregoing general 
construction is available from the Minnesota Mining and Manufacturing 
Company of St. Paul, Minn. under the designation Scotch-Brite.TM. Flap 
Brush and is shown in FIG. 1. 
The flap brush 10 shown in FIG. 1 is typically constructed by coating 
adhesive 16 over the outer surface 14 of a long central core 12 which can 
be 1.42 meters (56 in) long, for example, using art adhesive coater 50 as 
seen in FIG. 2. Coater 50 includes a cylindrical bore 52 having an inner 
diameter at wall 54 that is somewhat larger than the outer diameter of the 
core resulting in a gap 56 between the outer surface 14 and wall 54. 
Enough adhesive 16 to coat the core is held in funnel portion 58 of coater 
50. Valve 60 can be moved in the opposing directions indicated by arrow A, 
and initially rests against the inner wall of the funnel 58 where it joins 
the bore 52. This prevents the adhesive from flowing into the space 56 
between the bore wall 54 and the core 12. When valve 60 is lifted away 
from the wall of the funnel portion 58 to its open position, adhesive 
flows into space 56 between core 12 and bore wall 54, and bonds to outer 
surface 14 of core 12. Any suitable known means for maintaining the valve 
60 in its open position may be used such as a pin and groove interlock 
with a frame member (not shown). The first end 13 of core 12 is moved in 
direction B through the bore such that the adhesive is progressively 
applied to outer surface 14 along the full length of the core to second 
end 15 in a relatively uniform manner. The longitudinal axis 11 of core 12 
must be maintained sufficiently concentric relative to the longitudinal 
axis 53 of the bore of the coater, and the shape of the core must not be 
excessively out-of-round. In this manner, a sufficiently uniform coating 
of adhesive 16 will be applied around the entire outer surface 14 of the 
core 12 to adequately adhere substantially all of the core ends 20 of the 
abrasive flaps 18 to the core. In an attempt to maintain the core 12 
concentric with the bore 52 of the coater, the inner wall 62 of valve 60 
may be sized to be as close as possible in diameter to the outer surface 
14 of the core, allowing for manufacturing tolerances, while still 
allowing the core 12 to pass through the valve 60. The valve 60 is then 
held by a suitable frame member (not shown) to be concentric to the bore 
54, to keep the core 12 concentric with the bore 54. 
After the adhesive has been applied to the core 12 by the coater, a 
plurality of abrasive flaps 18 which can be 1.32 meters (52 in) long, 5.08 
cm (2 in) wide, and 1.27 cm (0.5 in) thick, for example, are compressed 
inwardly toward the core 12 to contact the adhesive 16. The long abrasive 
flaps 18 may be placed in contact with the adhesive 16 on the core 12 one 
after another, or more typically may be collectively compressed against 
the adhesive 16 until the adhesive cures. When the adhesive has cured 
sufficiently to retain the abrasive flaps 18, the long assembled abrasive 
flap brush may be cut transverse to the length of the core to provide a 
plurality of abrasive flap brushes 10 of any suitable width. Each flap 
brush may have a width of, for example, 2.54 cm (1.0 in). The final width 
of the flap brush 10 can be chosen with respect to the particular desired 
application of the flap brush. 
When fabricating conventional flap brush 10, it has been observed that it 
is not always possible to maintain the core 12 concentric relative to the 
bore of the adhesive coater for all or a portion of the length. Even when 
the valve inner wall 62 is sized to guide the core 12, it is not possible 
to always maintain desired concentricity. This can be caused, for example, 
by tolerances between the core outer surface and the valve inner wall 62 
and by tolerances between the valve 60 and the bore 52. These tolerances 
can allow the core to be non-concentric relative to the bore, and this can 
be aggravated by the distance between the bottom of valve 60 and the top 
of the bore 52 when the valve is moved to its open position. Additionally, 
the core 12 may exhibit excessive out-of-roundness along all or a portion 
of the length of the core. Either or both of these conditions can cause a 
portion of the outer surface 14 of the core to come too close to or 
contact the wall of the bore of the adhesive coater as illustrated at C in 
FIG. 3. Under these conditions, the adhesive layer 16 may not have uniform 
thickness around the circumference of the core or along the length of the 
core, or both. When the adhesive layer 16 is not uniformly distributed 
over the outer surface 14 of core 12, those flap brushes 18a that contact 
little or no adhesive coating on the core are not adequately adhered to 
the core, and may leave a gap 26 between outer surface 14 and core end 20 
of flaps 18a as seen in FIG. 4. The compressive force between adjacent 
abrasive flaps 18 and 18a may be insufficient to maintain unadhered 
abrasive flaps 18a on the flap brush 10, thereby reducing the 
effectiveness and life of the flap brush. 
It is therefore desirable to provide an abrasive flap brush with a core 
having a sufficiently uniform coating of adhesive and a method and 
apparatus for making an abrasive flap brush having a uniform layer of 
adhesive disposed on the core to ensure adequate adhesion of the abrasive 
flaps to the core. 
SUMMARY OF THE INVENTION 
One aspect of the present invention includes a method of making an abrasive 
flap brush comprising the steps of: a) providing a central core including 
an outer surface, a first end, and a second end; b) placing said first end 
of said core in a coater including a bore, said bore including an inner 
wall configured to extend around said outer surface; c) introducing 
adhesive into said bore; d) moving said core from said first end to said 
second end through said bore thereby coating said outer surface with said 
adhesive; and e) adhering a plurality of abrasive flaps to said core with 
said adhesive; wherein at least one of said outer surface and said inner 
wall includes a spacing means for maintaining a predetermined minimum 
distance between said outer surface and said inner wall. 
Another aspect of the present invention includes an abrasive flap brush of 
the type including a core having a layer of adhesive applied by the 
operative surface of a coater, said abrasive flap brush comprising a core 
including an outer surface; a layer of adhesive provided on said outer 
surface; and a plurality of abrasive flaps adhered to said core by said 
layer of adhesive; wherein said core includes spacing means on said outer 
surface for maintaining a predetermined minimum distance between said core 
outer surface and the operative surface of the coater thereby allowing a 
sufficiently uniform layer of said adhesive to be applied to said outer 
surface such that substantially all of said abrasive flaps are adhered to 
said core. 
A further aspect of the present invention includes a coater for applying 
adhesive to the outer surface of a core passed therethrough, said coater 
comprising a bore including an inner wall configured to extend around the 
outer surface of the core; adhesive supply means for providing adhesive to 
said bore; and spacing means provided on said inner wall for maintaining a 
minimum predetermined distance between said inner wall and the outer 
surface of the core. 
A yet further aspect of the present invention includes a core of the type 
including an outer surface for receiving a layer of adhesive applied by 
the operative surface of a coater, said core comprising an outer surface 
and spacing means on said outer surface for maintaining a predetermined 
minimum distance between said core outer surface and the operative surface 
of the coater.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention includes an abrasive flap brush including a central 
core, a substantially uniform layer of adhesive disposed on the outer 
surface of the core, and a plurality of abrasive flaps adhered to the core 
by the adhesive. The present invention also includes a method and 
apparatus for making such a flap brush. In a first embodiment of the 
invention, the core is provided with spacing projections that project 
radially from the outer surface of the core. When the core is drawn 
through a bore of an adhesive coater to have the adhesive applied thereto, 
the spacing projections maintain the outer surface of the core a minimum 
distance from the wall of the bore, so that sufficient adhesive is 
provided over substantially the entire outer surface of the core. In a 
second embodiment of the invention, the bore of the adhesive coater 
includes spacing projections for guiding the core through the coater bore. 
In a manner similar to the operation of the spacing projections of the 
core in the first embodiment, the spacing projections of the bore maintain 
a predetermined distance between the wall of the bore and the outer 
surface of the core. This spacing ensures adequately uniform distribution 
of adhesive over the core. Thus, the abrasive flaps are consistently 
adhered to the core by a suitable amount of adhesive, in contrast to 
conventional abrasive flap brushes. 
The abrasive flap brush of the present invention may be constructed with 
any suitable components as known in the art. The core may comprise 
materials including, but not limited to, metal such as aluminum; plastics 
such as nylon 6,6; or composites such as polyester/glass fiber composites 
or phenolic/paper composites. The core is preferably a hollow cylindrical 
core, but other types of cores are also contemplated. For instance, the 
core may be solid rather than hollow. Also, it may be possible to use a 
core having a non-circular cross-section in applications where work pieces 
are moved relative to the flap brush. 
The adhesive may be any suitable adhesive, including but not limited to 
pressure sensitive adhesives, curable epoxies, phenolics, silicones, 
acrylics, and styrene-butadiene copolymers. One preferred adhesive is an 
epoxy having a cure time of about 30 minutes or less, commercially 
available from Minnesota Mining and Manufacturing Company, St. Paul, 
Minn., under the trade designation Scotch-Weld.TM. Brand 3501 B/A Epoxy 
Adhesive. Another preferred adhesive is a mixture of the following 
components: 500 parts of Shell Epon.RTM. Resin 828 (bisphenol 
A/epichlorohydrin based epoxy resin) available from Shell Oil Co., 
Houston, Tex.; 500 parts of D.E.N..RTM. 438 Epoxy Novolac (polymers of 
epichlorohydrin, phenol-formaldehyde novolac) available from Dow Chemical, 
U.S.A., Midland, Mich.; 1000 parts of Capcure 3-800 (mercaptan polymer) 
available from Henckel Corporation, Ambler, Pa.; and 30 parts Capcure 
EH-30 (2,4,6,-tri (dimethylaminomethyl) phenol) also available from 
Henckel Corporation. 
The nonwoven abrasive flaps may comprise a staple fiber such as nylon, 
polyester or polypropylene; a curable binder such as phenolic, epoxy, 
acrylic, or polyurethane; and abrasive particles that are bonded to and 
between the fibers by the binder such as silicon carbide, aluminum oxide, 
talc, flint, or a ceramic aluminum oxide composition available from 
Minnesota Mining and Manufacturing Company, St. Paul, Minn. under the 
designation Cubitron.TM.. Examples of suitable nonwoven abrasive flap 
materials are disclosed in U.S. Pat. No. 2,958,593 (Hoover et al.), the 
entire disclosure of which is incorporated herein by reference. Suitable 
material for the abrasive flaps is commercially available from Minnesota 
Mining and Manufacturing Company, St. Paul, Minn., under the trade 
designation Scotch-Brite.TM.. The abrasive flaps may also comprise coated 
abrasive flaps, or a combination of coated abrasive and nonwoven abrasive 
flaps. 
FIGS. 5-7 and 9 illustrate one embodiment of a flap brush 110 in accordance 
with the present invention and an apparatus 150 for coating the core of 
the abrasive flap brush core in accordance with the present invention. 
Flap brush 110 includes core 112 which has an outer surface 114 and is 
preferably cylindrical and hollow, as shown, but could instead be solid 
and/or non-cylindrical. The outer diameter of core 112 may be any suitable 
dimension, and core outer diameters of between 1.91 cm (0.75 in) and 30.5 
cm (12 in) have been found to have utility. The length of core 112 may 
also be any suitable dimension, and core lengths of between 63 cm (25 in) 
and 230 cm (90 in) have been found to have utility. When a relatively long 
core is used to make an abrasive flap brush, the assembled flap brush can 
be cut transverse to the core to provide a plurality of smaller abrasive 
flap brushes. Thus, an assembled abrasive flap brush measuring 132 cm (52 
in) long may be sectioned into a plurality of 2.54 cm (1.0 in) wide, or 
1.27 cm (0.5 in) wide individual flap brushes, for example. 
Spacing means are provided to maintain a minimum distance between the outer 
surface of the core and the wall of the bore of the adhesive coater as the 
core is moved through the coater to apply adhesive progressively along the 
length of the core. Maintaining this minimum distance ensures a sufficient 
layer of adhesive is applied to the outer surface of the core to 
adequately adhere substantially all of the abrasive flaps to the outer 
surface of the core. 
In the first embodiment, the spacing means comprises radially projecting 
and axially extending spacing projections 118 extending from the outer 
surface 114 of the core 112. As seen in FIG. 6, projections 118 can 
comprise three evenly angularly spaced, rectangular extensions of the 
outer surface 114 of core 112. In one preferred embodiment, projections 
118 are each approximately 3.2 mm (0.125 in) wide in the circumferential 
direction, 1.6 mm (0.063 in) high in the radial direction, and extend for 
the full length of a 1.42 meter (56 in) long core. The cylindrical core 
112 can preferably have an inner diameter of 5.1 cm (2 in) and an outer 
diameter at surface 114 of 6.0 cm (2.375 in). Adhesive 140 is applied by 
the adhesive coater 150, and the spacing projections 118 ensure that a 
predetermined minimum distance between the outer surface 114 of the core 
112 and wall 154 of the adhesive coater 150 is maintained at all times 
during the coating process. If the full length or any portion of the core 
is not concentric with the bore, and/or if the core is out-of-round, the 
spacing projections 118, and not the outer surface 114 of the core, 
contact the side wall 154 of the coater bore 152 as seen at C in FIG. 6. 
Thus, adhesive 140 is provided over substantially the entire outer surface 
114 of the core 112. 
The spacing projections 118 are provided on the outer surface of the core 
during fabrication of the core. The projections may be integrally formed 
on the outer surface by molding a core with the desired projections. The 
core may also be fabricated integrally with the spacing projections by 
extrusion or pultrusion as is known in the art. Alternatively, the 
projections may be added to the core by adhesively or mechanically 
attaching the projections on a core. It is also possible to cut away or 
otherwise remove portions of the outer surface of a core to leave the 
desired projection. This can be accomplished by standard milling and 
machining techniques or by the use of a cutting method like that described 
in U.S. Pat. No. 5,247,740, Method and Apparatus for Cutting a Keyway in a 
Mill Roll (Curtis et al.), the entire disclosure of which is incorporated 
herein by reference. 
Adhesive 140 is applied to the core 112 as follows. Core 112 is disposed 
within cylindrical bore 152 of adhesive coater 150 with first end 113 of 
the core inserted first. In the illustrated embodiment, the spacing means 
takes the form of three rectangular spacing projections 118 evenly spaced 
about the outer surface 114 of the core 112 to maintain a predetermined 
minimum distance between the core and the wall 154 of the bore. As seen in 
FIGS. 5-6, the adhesive coater 150 includes a cylindrical bore 152 and a 
funnel portion 158 which is sized to hold a sufficient amount of adhesive 
140 to coat core 112. Valve 160 is hollow, and inner wall 162 is sized to 
accept core 112 within the valve. As explained above, it is desirable to 
maintain the longitudinal axis 111 of the core concentric with the 
longitudinal axis 153 of the bore. The inner wall 162 of the valve 160 may 
be approximately the same diameter as the outer diameter of the spacing 
projections of the core to guide the core 112 through the bore 152 as 
described above. Valve 160 may be moved in the opposing directions 
indicated by arrow A, and initially rests against the inner wall of the 
funnel portion 158 where it joins the bore 152. This prevents the adhesive 
from flowing into the space 156 between the bore wall 154 and the core 
112. When valve 160 is lifted away from the space 156 to its open 
position, adhesive 140 can flow into the space 156 while core 112 is moved 
in direction B through the bore 152 to be coated with adhesive 
progressively along its entire length starting at first end 113 and 
continuing to second end 115. The valve 160 may be maintained in its open 
position by any suitable known means such as a pin and groove engagement 
with a frame member (not illustrated). Core 112 should be moved through 
the bore at a rate which provides adequate coating of adhesive 140, and a 
rate of approximately 0.3 m/see (1 ft/sec) has been found useful. Adhesive 
140 fills the space 156 between core 112 and the wall 154 of bore 152, and 
bonds to the outer surface 114 of the core 112. Wall 154 thereby acts as 
the operative surface of coater 150 for applying the adhesive 140 to outer 
surface 114. 
As the core 112 is drawn through bore 152, the adhesive 140 bonds to the 
core and is drawn out of the gap 156 with the core. Adhesive 140 in the 
funnel portion 158 will continuously flow into the gap 156 to replace the 
adhesive bonded to the portion of the core which has exited the bore. When 
the valve 160 is in its open position, it should provide an adequate 
opening to allow sufficient adhesive 140 to flow into the gap 156. A space 
of approximately 1.9 cm (0.75 in) between the bottom of the valve 160 and 
the inner wall of the coater 150 has been found useful in this regard. 
In one preferred embodiment, the coater 150 is held stationary and the core 
112 is passed through the bore 152 until the entire outer surface 114 of 
the core 112 has been coated with adhesive 140. Other forms of relative 
motion between the core 112 and the adhesive coater 150 are also 
contemplated, such as holding the core 112 stationary and moving the 
coater 150, and moving both the coater 150 and the core 112. The coater 
described herein is illustrative of a preferred coater having an operative 
surface for coating adhesive onto the outer surface of the flap brush core 
of the present invention. However, the present invention is not so 
limited, and the flap brush core of the present invention may have 
adhesive 140 applied by any suitable means having an operative surface for 
applying adhesive to the outer surface of the core. For example, the 
coater need not encompass the entire circumference of the core and may 
instead apply adhesive to one segment of the circumference of the core at 
a time. 
After the outer surface 114 of the core 112 has been coated with adhesive 
140, the abrasive flap brush 110 may be assembled by pressing abrasive 
flaps 130 into the adhesive layer 140 disposed on the core 112 and holding 
the flaps in place until the adhesive has set. Each abrasive flap 130 
includes a core end 132 and an abrading end 134. When the abrasive flaps 
130 have been adhered to the core 112, the abrading ends 134 together form 
a uniform peripheral abrading surface 136 of the abrasive flap brush 110. 
When core 112 is of the dimensions described above, it has been found 
useful to apply one hundred and twenty-eight nonwoven abrasive flaps 130 
to the core. Each flap can be 1.27 m (50 in) long, 5.08 cm (2 in) wide, 
and 1.27 cm (0.5 in) thick. 
The abrasive flaps 130 may be pressed into the adhesive 140 seriatim, or 
may be arranged and pressed into the adhesive collectively as shown in 
U.S. Pat. No. 4,275,529, High Flap Density Abrasive Flap Wheel (Teetzel et 
al.), the entire disclosure of which is incorporated herein by reference. 
In such a method as disclosed in U.S. Pat. No. 4,275,529, a sufficient 
number of flaps for the entire wheel are stacked side by side in a row 
with outer end 134 of each flap positioned face down. The entire stack is 
compressed by a press or other suitable means until the compressed length 
is equal to the final assembled circumference at core end 132 of the 
flaps. The core ends 132 are maintained in this compressed state by 
placing a suitable holding means on the core ends of the flaps, such as a 
strip of adhesive resin or a strip of adhesive tape. The flap assembly is 
then released from the press and flexed about the core and held against 
adhesive 140 in a manner know in the art until the adhesive 140 cures. 
Another preferred method and apparatus for assembling flaps 130 is seen in 
FIG. 7. Former 170 includes any suitable number of flap trays 174 
uniformly arranged around central axis 172. When making an abrasive flap 
brush having an outer diameter of approximately 15.2 cm (6 in) to 20.3 cm 
(8 in), it has been found useful to employ sixteen trays 174, each holding 
eight flaps 130 for a total of one hundred and twenty-eight flaps on a 
flap brush 110. The trays 174 are at least long enough to hold the flaps 
130, and may, for example, be 1.32 meters (52 in) long. Trays 174 are 
removed from former 170 and loaded with flaps 130. The flaps 130 are 
inserted into the trays 174 with core ends 132 extending from the tray and 
outer ends 134 held within the tray. The trays are then returned to former 
170. The trays initially are far enough apart from central axis 172 to 
allow a core 112 coated with adhesive 140 to be placed in the center of 
the former 170 along axis 172. Each tray is connected to a suitable drive 
means (not shown) which moves the trays radially into contact with the 
core, simultaneously compressing the core ends 132 of the flaps in the 
circumferential direction. The trays 174 may be rectangular in 
cross-section, in which case they must be flexible enough to be deformed 
to a wedge-shaped cross section when driven to hold the flaps against the 
adhesive. Such a configuration allows the flaps to be easily loaded onto 
the trays. Alternatively, the trays may initially be wedge-shaped as 
illustrated. When using one hundred and twenty eight nonwoven abrasive 
flaps of the size described above to fabricate an abrasive flap brush 
having an outer diameter of 15.2 cm (6 in), the flaps are compressed at 
their core ends 132 to about 10% of their uncompressed thickness, and are 
compressed at their outer ends 134 to about 30% of their uncompressed 
thickness. It will be recognized, however, that the flaps may be 
compressed more or less depending on several factors such as the intended 
application of the abrasive flap brush, on the size of the assembled flap 
brush, and on the number, type, grade and dimensions of the flaps. The 
trays maintain the flaps against the core until the adhesive 140 sets. An 
assembled abrasive flap brush 110 constructed in accordance with the 
foregoing embodiment is illustrated in FIG. 9. 
FIG. 8 illustrates another embodiment of the present invention, in which 
the spacing means is included in the adhesive coater. Bore 252 of the 
coater includes spacing projections 262 extending radially from the wall 
254 towards the center of the bore to guide core 212 as it is passed 
through the bore 252. In the illustrated embodiment, five triangular 
projections 262 are evenly spaced about the bore. In a manner similar to 
the spacing projections 118 provided on core 112 in the previously 
described embodiment, spacing projections 262 maintain a predetermined 
minimum distance between core outer surface 214 and the wall 254 of the 
bore 252 to ensure that a sufficiently uniform layer of adhesive 140 is 
provided on the outer surface 214 of the core 212. After the outer surface 
214 of the core 212 has been coated with adhesive 140, the abrasive flaps 
130 may be adhered to the core 212 in the manner described above with 
respect to the previous embodiment. 
In any of the embodiments described herein, the spacing means may be of any 
cross-sectional shape, provided that they maintain the necessary spacing 
between the inner wall of the bore which serves as the operative surface 
of the coater, and the outer surface of the core to ensure adequate 
adhesive is coated onto the outer surface of the bore, even when the core 
is not truly concentric in the bore, or when the core is out-of-round. 
However, the spacing means should not be so large individually or in total 
to interfere with coating an adequate amount of adhesive 140 onto the 
outer surface of the core. Examples of other preferred cross-sectional 
shapes of the spacing projections include scallop shaped projections as 
seen in FIG. 10, or mushroom shaped projections as seen in FIG. 11. 
Scallop shaped projections 121 include peaks 122 and valleys or adhesive 
reservoirs 123. The peaks 122 will maintain a desired minimum gap between 
the core 112 and coater bore 152 to ensure adequate adhesive is coated 
into the valleys 123. With mushroom shaped projections 124, the top 
surface 125 will contact the bore to maintain a desired minimum spacing, 
ensuring adequate adhesive is coated in adhesive reservoirs 127. To reduce 
the area of the spacing projection which contacts the wall of the bore, 
top 125 may be modified to have a more pronounced peak 128 as seen in FIG. 
12. An additional benefit of a projection such as the mushroom shaped 
projection is the presence of an undercut portion 126 that will provide a 
secure mechanical interlock between the core and the adhesive. Although it 
is possible to have a single spacing projection, there are preferably at 
least two spacing projections, and more preferably three or more 
projections are included. Also, the projections may be discrete (such as 
bumps) rather than continuous, and need not be linear along the length of 
the core or the bore (such as helical or wavy projections). The spacing 
projections may or may not be evenly spaced about the core in the first 
embodiment, or about the bore in the second embodiment. The spacing means 
may be included on either or both the core and bore. 
Whether the spacing projections are present on the core 112 or the coater 
250, it is important that they be configured to allow a sufficiently 
uniform coating of adhesive to be applied to the outer surface of the 
core, even when the core is not concentric to the bore, or when the core 
is out-of-round, or both. When the spacing projections are provided on the 
core 112, the projections will ensure a substantially uniform layer of 
adhesive 140 is applied at least to the portions of the outer surface 114 
between the projections, even if the projections contact the bore during 
application of the adhesive. Those portions of the outer surface between 
the projections thus serve as adhesive reservoirs and are illustrated as 
adhesive reservoir 120 in FIG. 6; valley, or adhesive reservoir 123 in 
FIG. 10; and adhesive reservoir 127 in FIG. 11. Although little or no 
adhesive may initially be coated onto to the top of the projections which 
contact the bore, the adhesive applied in the adhesive reservoirs between 
the spacing projections will be forced onto the top of the projections 
when the flaps are pressed into contact with the bore. This will ensure 
adequate bonding of substantially all of the flaps. Similarly, if a 
projection 262 extending from the bore of the coater contacts a portion of 
the outer surface of the core, that portion will receive little or no 
adhesive in a local area. Pressing the flaps into contact with the core 
will force the adhesive to fill into the portions of the core contacted by 
the bore projections, allowing adequate bonding of substantially all of 
the flaps. 
It is preferred that the spacing means not all simultaneously contact the 
wall 154 of the bore 152 in the first embodiment, or the outer surface 214 
of the core 212 in the second embodiment, because little or no adhesive 
140 would adhere to the contact areas. Instead, it is preferred that the 
diameter of the bore, core, and spacing means be selected to allow 
clearance between the spacing means and the opposed surface when the core 
is centered within the bore and the core is not out-of-round. Under these 
circumstances, adhesive will be applied reservoir portions of the outer 
surface 114 and the outermost surfaces of the spacing projections on core 
112. It is also preferred that the adhesive 140 be selected to adhere to 
the core without dripping off or migrating along the core due to gravity. 
The adhesive 140 should have a sufficiently high viscosity and short cure 
time to prevent excessive movement of the adhesive 140 prior to the 
adherence of the abrasive flaps 130 to the core. The core optionally may 
be rotated about its longitudinal axis while adhesive is applied by the 
adhesive coater, to spread adhesive over the peripheral surface of the 
core. 
The operation of the present invention will be further described with 
regard to the following detailed examples. These examples are offered to 
further illustrate the various specific and preferred embodiments and 
techniques. It should be understood, however, that many variations and 
modifications may be made while remaining within the scope of the present 
invention. 
EXAMPLE 1 
An abrasive flap brush 110 was provided according to the present invention 
as follows. A glass fiber/polyester composite core 112 having an inner 
diameter of 5.1 cm (2 in) and an outer diameter initially of 6.0 cm (2.375 
in) was provided with 21 spacing projections 121 by machining 21 grooves 
parallel to the longitudinal axis of the core and evenly spaced about the 
circumference of the core, as shown generally in FIG. 10. The grooves were 
formed with a 1.27 cm (0.5 in) wide end mill having a 0.64 cm (0.25 in) 
cutting radius. The grooves were each approximately 0.24 cm (0.094 in) 
deep at the center. The finished core had a cylindrical inner surface and 
a scalloped outer surface with a thickness varying from peak to valley of 
the scallops of approximately 0.476 cm (0.188 in) to 0.238 cm (0.094 in). 
The peaks of the scallops were each less than 0.318 cm (0.125 in) wide in 
the circumferential direction. The core was 1.42 m (56 in) long. 
A funnel-shaped adhesive coater as described above comprising a funnel 
portion and a cylindrical bore portion was provided. The funnel portion 
was large enough to hold sufficient adhesive 140 to coat a core at least 
2.29 m (90 in) long. The bore of the coater was 6.4 cm (2.5 in) diameter. 
The adhesive 140 was the above-described mixture of: 500 parts of Shell 
Epon.RTM. Resin 828 (bisphenol A/epichlorohydrin based epoxy resin) 
available from Shell Oil Co., Houston, Tex.; 500 parts of D.E.N..RTM. 438 
Epoxy Novolac (polymers of epichlorohydrin, phenolformaldehyde novolac) 
available from Dow Chemical, U.S.A., Midland, Mich; 1000 parts of Capcure 
3-800 (mercaptan polymer) available from Henckel Corporation, Ambler, Pa; 
and 30 parts Capcure EH-30 (2,4,6,-tri (dimethylaminomethyl) phenol) 
available from Henckel Corporation. The adhesive coater was held 
stationary, and the core was passed through the bore by hand at a speed of 
approximately 0.3 m/sec (1 ft/sec). The core was intentionally held 
off-center relative to the bore such that the spacing projections on one 
side of the core continuously contacted the wall of the bore. 
After the adhesive was applied, 128 abrasive flaps were provided. The 
abrasive flaps comprised a nonwoven abrasive material commercially 
available from Minnesota Mining and Manufacturing Company, St. Paul, 
Minn., under the trade designation Scotch-Brite.TM. type 7A Medium Cut & 
Polish Material. The flap material was cut to provide individual flaps 
approximately 1.27 m (50 in) long by 5.08 cm (2 in) wide by 1.27 cm (0.5 
in) thick. Eight flaps were inserted in each of sixteen trays and then 
compressed and held in contact with the adhesive with a former as 
described above until the adhesive was sufficiently cured. 
The resulting abrasive flap brush had a 15.24 cm (6 in) outer diameter and 
a core inner diameter of 4.58 cm (2 in). The assembled flap brush was cut 
into a plurality of flap brushes each 2.54 cm (1 in) wide. The flap 
brushes were visually inspected and used to abrade a surface, and all of 
the abrasive flaps were observed to be sufficiently adhered to the core. 
EXAMPLE 2 
The flap brush of Example 2 was fabricated by the same process as the flap 
brush of Example 1 except for the spacing projections provided on the 
core. A core having an inner diameter of 5.1 cm (2 in) and an outer 
diameter initially of 6.0 cm (2.375 in) was machined to remove about 1.6 
mm (0.063 in) of material from the outer surface except for three 
generally rectangular spacing projections 118 formed from the uncut 
material, as seen generally in FIGS. 5-7. The projections were each 
approximately 1.6 mm (0.063 in) high, 3.2 mm (0.125 in) wide along the 
circumference of the core, and extended for the full length of the core, 
1.42 meters (56 in). The projections were spaced approximately 120 degrees 
apart. The core was held off-center relative to the adhesive coater such 
that the top surface of two of the projections continuously contacted the 
bore of the coater and therefore were not coated with adhesive. However, 
sufficient adhesive was coated on the entire portion of the outer surface 
between the spacing projections. This provided sufficient adhesive such 
that when the abrasive flaps were pressed into place, adhesive was 
displaced and flowed about the entire circumference, such that all of the 
abrasive flaps were adequately adhered to the core. The long flap brush 
was then cut into a plurality of flap brushes each 2.54 cm (1 in) wide. 
The flap brushes were visually inspected and used to abrade a surface, and 
all of the abrasive flaps were observed to be sufficiently adhered to the 
core. 
EXAMPLE 3 
The flap brush of Example 3 was fabricated by the same process as the flap 
brushes of Examples 1 and 2, except for the spacing projections provided 
on the core. The projections of Example 3 were formed by pultrusion, using 
a die which formed eight spacing projections having a "mushroom shape" as 
shown generally in FIG. 11. The spacing projections each extended about 
1.22 mm (0.063 in) high from the outer surface of the core, were about 4.8 
mm (0.188 in) wide at their widest point, and extended the full length of 
the core. The undercut of the mushroom had a radius of curvature of about 
0.41 mm (0.016 in). The core was held off-center relative to the adhesive 
coater such that the projections on one side of the core continuously 
contacted the wall of the bore of the coater. The long flap brush was then 
cut into a plurality of flap brushes each 2.54 cm (1 in) wide. The flap 
brushes were visually inspected and used to abrade a surface, and all of 
the abrasive flaps were observed to be sufficiently adhered to the core. 
The present invention has now been described with reference to several 
embodiments thereof. The foregoing detailed description and examples have 
been given for clarity of understanding only. No unnecessary limitations 
are to be understood therefrom. It will be apparent to those skilled in 
the art that many changes can be made in the embodiments described without 
departing from the scope of the invention. Thus, the scope of the present 
invention should not be limited to the exact details and structures 
described herein, but rather by the structures described by the language 
of the claims, and the equivalents of those structures.