Note: Descriptions are shown in the official language in which they were submitted.
. ,, . . . , . . . I
6~6 ~)
~~ METEIOD OF COATING OBJECTS
,,
,. I
BACKGROU~lD OF THE INVENTION
,
- The invention relates generally to methods for coating
objects and particularly to methods for applying flock to all of
the surface of an object without leaving support marks.
, Whenever a three dimensional object is supported while
a coating of material is applied, there are invariably areas of
the object's surface that are not coated because they were
shielded by the support. The problem is not always serious. If
a first coat leaves gaps in coverage the object may be supported
elsewhere and a second coat may be applied to the surface area
that includes the gaps. This solution is suitable if the overlap I
of the first coat by the second that is bound to occur does not
detract from the overall appearance or function of the object~
i If the overlapping of coats that results from this method does
detract from the appearance or function of the object, the method
is obviously not suitable.
The gaps could be avoided altogether by supporting the
object without physically contacting its surface. However, tech
~ niques for this, such as air cushion supports, magnetic suspen-
sions, and electrostatic suspensions, are difficult and
;expensive, and not suitable or practical for many objects. The
"gaps can also be minimized, by using support structures such as
¦pins that greatly reduce the area shielded from coating. For
¦some purposes, the small gap in the coating that result may be
: I accept able.
¦ For some forms of coat ing, overlapping coats are not
¦suitable, and even minimal support marks are undesirable.
Il .
11
.. . .
~ ~ ~3~ ~ 6
.:
Flocking is an example of such a coating. In flocking, fibers
! are deposited by mechanical or electrostatic methods on an adhe-
sive coated surface, the ends of the fibers being imbedded in
the ~ncured adhesi~e. The adhesive is then cur~d or set. Since
the ~rocess has two steps, and the flocking has a texture,
overlapping "coats" of flocking would be unacceptable. Any gaps
; in floc~ing tend to be obvious, particularly where the flocked
fibers are long, since the texture of the surface created by the
flocking exaggerates the impression the gaps make. A fl~cked
1~ tennis ball, for example, may be prod~ced by automatic machinery
to provide an inexpensive substitute for the traditional tennis
ball in which the covering is applied by hand if the flock sur-
face can be obtained unmarred by defects caused by supports.
It is an object of this invention to provide a method for apply-
ing coatings such as flocking to three dimensional objects with-
out leaving unsightlv support marks. It is another object to
use electron beam curing to provide for applying coatings such as
flocking to objects in a wav that makes supporting the object
during the coating process simple and secure. ~ther objects of
the invention will be pointed out, or be inherent, in the follow-
ing description of the invention.
SUrl~ARY OF THE INVENTION
The invention comprises applving an electron beam
curable coatin~ to the surface of an object, supporting it at
a location, and applying ~n electron beam to oure the coating
'
'
-2-
~.. . .
,
66
except for a portion including the support location. Then the
object is supported at another location in the cured portion and
the remaining portion of the coating is cured by applying the
electron beam.
i
In preferred embodiments the method is used to flock
objects without leaving support marks, by first applying an
electron beam curable adhesive to the entire ~urface of the
object. The object is then supported by a support means con-
tacting a surface portion of a first side of the object at a
location remote from the second side. Fibers are then applied to
the second side and areas of the first side adjacent the second
side, and the second side is cured by directing an electron beam
at it. The object is then supported at a location on the second
side, fibers are applied to the remainder of the first side, and
an electron beam is applied to the first side to cure the pre-
viously uncured adhesive there, automatically completing the
coating process.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
Other objects, features, and advantages will be
apparent from the following description, including the drawings,
in which Figures l to 9 illustrate, diagrammatically, the steps
of flocking a tennis ball using the method embodying the inven-
tion. I
DESCRIPTION OF A PREFERRED EMBODIMENT
,I The figures show the application of flocking to arubber ball l0 to give it the textured surface that would allow,
~1 for example, its use as a tennis ball. The method of the inven-
! tion could be applied to a wide variety of objects, but theexample of a tennis ba11 ls particu1ar1y appropriate. In ordeF
3-
" , 11 , . : ., I
~ ~5~666
for a tennis ball to be flocked in this manner and function well,
the flocking must be applied evenly to the entire surface.
Unsightly gaps in the flocking must be minimized.
The first step in flocking the ball 10, shown in Figure
1, is to dip the ball in a tank 12 containing liquid adhesive 14,
as shown in Figure 2. The adhesive 14 is applied to the entire
'surface of the ball 10. The adhesive is the kind used to bind
flock, and is curable by the application of an electron beam of
low energy. The adhesive would be radiation curable, perhaps
from the urethane family, compounded to adhere to the rubber ball ¦
and flock, and to be flexible enough to adhere even when the ball
is distorted. Such adhesives are available from many sources.
One example of such an adhesive is that sold by Hughson
Chemicals, of Erie, Pennsylvania, and designated by that company
as RD 3420-17.
Referring to Figure 3, it can be seen that the adhesive
covered ball 10 is then rested on a triangular support 16
extending upward from an arm 18 mounted on some outside support
for instance (not shown). The triangular support 16 is fairly
narrow, and supports a ball 10 at a location 20 on the bottom
side 21 of the ball. An imaginary equator 22 separates the top
; side 23 of the ball from the bottom side 21. The elements of the
support 16 are spread apart enough to form a stable platform for
the ball 10, but they are still spaced remotely from the equator
22 dividing the top and bottom sides of the ball.
¦ In the next step shown in Figure 4, ibers 26 are
applied electrostatically to the top side 23 and adjacent pox-
tions of the bottom side 21 of the ball 10. The method of appli-
~cation is conventional. A container 28 is loaded with a flock
,
I -4- ~
. . . . .
C ;` ~ D6~6
material 26 to be deposited on the ball's surface. An energizing
screen 30 is provided at the lower end of the container 28, and a
collecting member 32 is provided below the ball 10. The ball is
supported in position by the support 16. A high D.C. voltag~ is
;applied between the energizing screen 3q and the triangular sup-
port 16 and the bottom trough or collector 32 in order to orient
and propel the fibers 26 onto the adhesive covered ball 10.
'I
The entire surface of the ball is not covered with
fibers. The electrostatic field is controlled by suitably shaped
barriers of the appropriate voltages to direct the fibers pri-
marily to a portion of the surface of the ball 10. In the
illustrated embodiment, a metal baffle 33 extends outwardly from
a circular interior edge 33a adjacent the ball 10 below the
`~equator 22. The baffle 33 is either grounded or held at some
other voltage suitable for limiting the electrostatic field so
that the fibers 26 are directed to the top side 23 of the ball
~and portions of the bottom side 21 that are adjacent the top
side. In other words slightly more than half the ball has fibers
applied to it. ~he area including the location 20, where the ¦
20 ; support 1~ contacts the surface of the ball 10, is kept essen-
tially free of fibers.
In the next step, as shown in Figure 5, a portion of
the adhesive 14 c~vering the ball 10 and having fibers embedded
in it is cured. The ball 10 is placed, still on its support 16,
under an electron beam producing gun 34 scanning horn 35 and
¦¦power supply 36 within a radiation proof shielding enclosure 38.
In the embodiment shown here, the support 16 for the ball 10 i5
shown as rotatable, in the direction of the arrow 39, about the
joint with the arm 18. This allows the scarnirg horn 35 to be
_5_
~5~ i6
directed at the ball 10 from an angular position, making more
efficient use of the horn. The enclosure 38 includes an outlet
duct 40 with a fan 42 for dissipating ozone created by electron
beam, and a slit 44 for inserting the ball 10.
, The electron beam apparatus is conventional and may be
,any of the low voltage models, for example EPS-300-25-18-C, manu-
factured by High Voltage Engineering Corporation of surlington,
Massachusetts. Such a machine may be adjusted to produce an
electron beam with a nominal energy level of 250 kev. to 300 Kev
as well as an adjustable angle of exit or sweep of the electrons
from the scanning horn 35. The dosage required for curing is a
function of the adhesive used; the dosage received is determined
by the time of application of the electron beam and by the magni-
tude of the beam intensity.
.
The beam of low energy described above will penetrate
the flocking on the top side 23 of the ball 10 and cure the por-
-tion of the adhesive 14 there, the energy level required being
approximately equal to that required to cure the adhesive without
the flock present, as disclosed in my co-pending application pre-
viously cited. The beam will not penetrate into the ball 10
'-itself, and hence will not cure the adhesive 14 on the bottom
side 21 of the ball 10. As a result there is a band of uncured
adhesive with flock embedded in it between the cured, flocked,
adhesive on the top side 21 and the uncured, unflocked, adhesive
on the bottom side 23. This selective curing of the adhesive 14
¦¦is a unique characteristic of electron beam curing. It would not
jibe possible, for example, with thermal curing or curing derived
Ifrom catalyst-resin mixing.
il
,; .
;~
I I .
li . I
( i ;~
!~ ~15~666
~ In the next step, shown in Figure 6, another three
i point support 44, rotatable about a joint with an arm 45, is set
on the top side 23 of the ball 10. ~hen, as shown in Figure~7,
the two supports 16 and 44 and the ball 10 are rotated 180, and
the bottom support 16, brought around to the top, is removed.
,~ I
The ball is now supported by the triangular support 44 contacting I
it on the previously flocked and cured portion of the ball's sur- !
face.
In the next step the ball 10 is inserted in the
flocking apparatus and an electrostatic field is created to pro-
-pel fibers 26 toward the bottom side 21, now on top. The entire
,. !
~ball 10 will now be covered by fibers. By the nature of the
electrostatic application of the fibers they will be distributed
evenly. To the extent that fibers 26 are directed by the field
to portions already imbedded with fibers, the extra fibers so
directed will simply not take hold. Furthermore, there will be
no gaps in adhesive 14 left by the contact of support 16. The
adhesive selected is a self-leveling type~ so that once the
pressure of the support 16 is removed, the adhesive 14 will tend
to cover the surface where the support 16 is contacted.
Alternatively, additional adhesive 14 can be added to the loca-
tion 20 to cover any gaps left by the first support 16. The
~result of this second application of fibers 26, then, will be
,that the ball is entirely covered with adhesive 14 and fibers 26.
Only the top side 23, now on the bottom, has had its adhesive
~ ¦!cured. The bottom side 21, now on the top, is covered with
- ¦¦fibers but the adhesive in which they are embedded is not yet
¦¦cured.
ji,
I In the next step shown in Figure 9, curing of the adhe- ¦
30 ¦¦sive 14 i6 completed by placing the ball 10 in the electron beam
_7_ ~
~ 666
enclosure 38 and directing the electron beam from the scanning
horn 35 toward the bottom side 21 in the same manner as was done
in the previous step in which the top side ~3 was cured. The
remainder of the adhesive 14 is thereby cured and the ball 10 is
now completely covered with flocking held by the cured adhesive
'14.
The result of using the method described above is a
-ball completely covered with flocking uniformly distributed, and
with no gaps in the distribution of the flocking. The method
described for coating this ball 10 with a coating of adhesive and
flocking is illustrative of the invention. Various modifica- i
tions, alterations, and deletions to the illustrated method may
be made by those skilled in the art. For example, the adhesive
14 can be initially applied to an object by other methods besides
dipping, such as spraying. The support 16 and later the support
;44, were merely examples. Any support capable of holding an
object in some stable manner, such as a hollow tube, would be
~,satisfactory. The two step method of applying adhesive and the
,flocking was shown in the illustrated embodiment because its
,complexity makes the method of the invention particularly useful.
But the method of the invention may be used when only one coating
is applied to an object. Variations of the method illustrated
l¦are therefore contemplated and the scope of the invention is not
¦imeant to be limited by tbe embodiment shown but is to be defined
I l¦by the following claims.
