Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a blasting mask and to a method
of making and using same.
A blasting mask in accordance with the invention comprises a
thin backing sheet which can be of plastic, such as a polyester
material, preferably Mylar, a registered trademark of DuPont, in
the order of a few thousandths inch thick. A hardened layer of
photosensitized material of predetermined size and shape is
adhered to the backing sheet with the backing sheet being totally
exposed or bare in those por~ions where the hardened material does
not exist. The edges of the hardened material are substantially
perpendicular to the backing sheet to provide clean lines for the
blasting grit. The photosensitive material is converted from a
monomer to a polymer by being exposed to triggering energy waves,
preferably in the form of ultraviolet light.
In the method oE making and using the grit blasting mask in
accordance with the invention, a shape which is to be reproduced
in grit-erodlble materlal such as stone, wood, glflss or plastic,
is first produced on or placed against a sui~able background and
a photograph taken thereof to produce a suitable light-control
sheet or negative. A blasting mask blank is provided which includes
a thin backing sheet preferably of polyester material such as Mylar
in the order of a few thousandths inch thick. This backing sheet
has a layer of photosensitive material thereon which is in a soft
or even liquid state but portions of which become harder when sub-
jected to ultraviolet light or o~her suitable triggering energy
waves. The light is then directed through the negative to the
blasting mask blank to cause the light to strike the photosensitive
Layer either within the area defined by the shape on the negative,
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if the shape is originally darlcer than the background, or in the
background around the shape, if the original shape is lighter than
the backgro~md.
The portion of the photosensitive layer which is not subjected
to the light remains in its original relatively soft or liquid
condition while the material struck by the light polymerizes and
becomes harder. The unsensitized material can then be removed
simply by washing it away with a solvent or liquid detergent.
This material is removed completely to provide a bare surface on
the backing sheet. The edges of the shape of the sensitized ma-
terial are substantially perpendicular to the plane of the backing
sheet, forming an abrupt offset therebetween to achieve a sharp,
well-defined shape on the grit-blasted surface of the grit-erodible
material in which the shape is to be formed.
The now-completed blasting mask is placed on the surface of
the grit-erodible mater.ial in the desired position. The back.ing
sheet can be placed contiguous to the surEace but the harder sen-
sitized material Eorming the shape can also be placed in contactwi.th the surface. In either event, the blasting mask can be ad-
hered to the surEace with a suitable adhesive to prevent shifting.
Blasting grit, which can be in the form of silica sand, steel shot,
or aluminum oxide, by way of example, is then directed toward the
blasting mask which destroys the bare plastic backing sheet, while
not having any significant effect on the polymerized photosensitive
material. The blasting grit is then applied until the backing
sheet is destroyed and the grit-erodible material is eroded to a
desired depth. Particularly where the grit-erodible material is
easily eroded by the blasting grit, the blasting mask can be placed
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with the harder sensitized material in contact with the surface
and adhered thereto by a suitable adhesive. The backing sheet can
then be peeled away and the blasting grit is then directed toward
the surface as before. However, with no backing sheet to be de-
stroyed, the blasting grit can be directed with somewhat greater
control toward the grit-erodible material. This technique is
particularly suitable for producing shapes in glass or mirrors
including where select portionS of the silver coating of the mirror
are to be removed by blasting.
The new blasting mask and method enable more intricate
designs or shapes, including even pictures, including photographs,
to be reproduced in grit-erodible materials, and smaller letters
can also be Eormecl than with the masks and the methods heretofore
employed. The blasting mask can also be macle much more quickly
than heretofore when maslcs were usually hand cut or sometimes die-
cut and then stripped by hand. Partl.cularly for more simple
shapes, the masks can be used over agaln by placing the harder
sensitized material Eorm:i.ng the shapes on a new backing sheet to
form a new blasting mask or directly on the surface of the grit-
- erodible material. In any event, the negative can be reused to
form new blasting masks with a relatively small amount of ti.me and
labor involved,
It is, therefore, a principle object of the invention to pro-
vide an improved blasting mask and method for forming a desired
shape in a grit-erodible material.
Another object of the invention is to provide a blasting mask
and shape-reproducing method having the advantages discussed above.
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Many other objects and advantages of the invention will be
apparent from the following detailed description of preferred
embodiments thereof, reference being made to the accompanying
drawings, in which:
Yig. 1 is a somewhat schematic view in perspective of art-
work in the form of a shape and background being photographed by
a camera;
Fig 2 is an enlarged, schematic view in perspective of a
negative, a blasting mask blank, and a light source for producing
an image on the blank corresponding to the shape on the negative;
Fig. 3 is a greatly enlarged view in transverse cross section
of the blasting mask blank, after exposure, taken generally along
the li.ne 3-3 oE ~ig. 2;
Fig. ~ is a schematic view in section showing a grit blasting
nozzle for di.recting grit toward the blasting mask located on the
surfflce of a gr:it-~rodiblc material; and
Fig. 5 is a schemcltlc view simi.lar to Fig. 4 but showing the
blastlng maslc on the surfa~e o~ grit-erodible material in a differ-
ent position.
l~eferring to Fig. 1, artworl~, in the form oE a shape or
design 10, shown Eor purposes of illustration in the form of a
cross, is drawn on or positioned against a plain backgro~md sheet
12. A thin border line 14 and a wider border line 16, with a space
18 therebetween, are located near the edges of the sheet. The cross
preferably is drawn on the background sheet or can be a separate
piece adhered to the background sheet or can be a separate piece
spaced from the background sheet. A camera 20 is used to photo-
graph the shape to produce a light-control shee~ or negative 22
(Fig. 2) of the same size as the shape to be reproduced on the grit-
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erodible surface. A positive instead of a negative can also be
made by using positive film. Negative, as used here, is intended
in the broad sense to be film with an image thereon corresponding
to the shape to be reproduced. The negative 22 can be produced
b~ other techniques, too, such as by drawing the shape or design
with an opaque substance on a light-transmitting sheet, by way of
example, or using a silk-screen process. A negative produced by
photography, however, provides a relatively easy way of producing
a light-transmitting sheet with a shape thereon, wherein either
the shape or the back~round area around the shape is light-trans-
mitting, depending upon which is to be eroded in the grit-erodible
material in which the shape is to be reproduced.
A source 24 of triggering energy waves, such as an ultra-
violet light, is then positioned on one side oE the control sheet
or negatlve 22 and a blasting mask blank 26 is positioned on the
other side of the negative 22. The blank 26 is positioned in con-
tact wi~h the negative 22 to produce a shape of the same size as
the negative 22, being spacecl apart here ~or purposes of illustra-
tion.
In this instance, the negative 22 has a transparent or more
light-transmitting area 28 corresponding in shape to the dark cross
10 of Fig. 1, and has an opaque or less light-transmitting area 30
around the area 28 corresponding to the light background sheet 12
of Fig. 1. The negative also has wider and narrower border lines
32 and 34 which are more light-transmitting, corresponding to the
dark border lines 14 and 16 of Fig. 1, with a space 36 therebetween,
which is less light-transmitting or opaque.
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The grit-blasting mask 26 comprises a thin backing sheet 38
(Fig. 3) of plastic material or even paper and a layer 40 of photo-
sensitive material, preferably commerci.ally-available photo-polymer
material. The backing sheet 38 can be of a polyester material such
as Mylar and can have a thickness preferably from 0.0005 inch to
0.015 inch. The layer 4Q of material is initially in a soft or
liquid state on the backing sheet and is polymerized or more fully
polymerized when subjected to triggering energy waves, commonly
ultraviolet light. This layer preferably is from 0.003 inch to
10 about 0.25 inch in thickness. The areas of the layer which are
subjected to the ultraviolet light for a predetermined period of
time become harder as polymers and remain on the backing sheet.
The portions o:E the layer which do not receive the ultraviolet
light remain soft or liquid as monomers and can be subsequently
washed away by a suitable solvent or detergent. The soft material
in this instance is cotnpletely washed away to leave a bare surface
on the baclting sheet: 3~ so that :it can be Eully contacted and
quictcly worn away by blasting grit.
As shown in Fig. 3, a light-struck, harder area 42 of the
photosensitive mnl:erial convertecl to a polymer, shown cross-hatched,
corresponds in shape to the area 28 of the negative 22. Outer thick
and thin areas 44 and 46 correspond to the areas or lines 32 and 34
of the negative 22. A light-shielded, soft or liquid area 48 sur-
rounding the harder area 42 corresponds to the opaque area 30 of the
negative, the soft area remaining so as a monomer since it does not
receive the ultraviolet light which is blocked out by the opaque
area 30. Similarly, a thin outer area 50 between the areas 46 and
48 corresponds to the spacing 36 of the negative 22 and remains soft
or liquid since it likewise does not receive ultraviolet light which
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is blocked out by the opaque area 36. When the unpolymerized
areas 48 and 50 are removed, the edges of the polymerized areas 42,
44, and 46 are substantially perpendicular to the plane of the
backing sheet 38 to provide clean lines for producing the shape on
the grit-erodible material.
The now-completed grit-blasting mask 52 can then be positioned
on a body 54 of grit-erodible material such as stone, with the back-
ing sheet 38 placed in contact or contiguous relationship with the
surface of the body 54. The mask 52 is preferably adhered to the
body 54 by suitable adhesive to prevent shifting ~mder the force of
the blasting grit. Blasting grit is then directed over the mask 52
such as by a sui~able blasting nozzle 56. The blasting grit erodes
the bare backing sheet 38 while having substantially no effect on
the polymer:ized areas 42, 44 and 46. The blasting grit is applied
until the surface of the body 54 is eroded to a desired depth to
complete the shape or design in the body. It will be seen in this
instance that the dark cross lO oE F:ig. l will remain as the flat
surEace on the bocly 54, under the harclened area 42, while the light
background 12 and the space 1~ will be eroded into the surface,
leaving border ]ines flush with the surEace of the body 54 corre-
spotlding to the hardened areas 44 and 46. A light cross lO on a
dark background 12 will produce the opposite result.
The completed grit-blasting mask 52 can also be positioned on
the body 54 of grit-erodible material with the polymerized areas 42,
44, and 46 placed in contact or contiguous relationship with the
surface of the body 54 with the backing sheet 38 spaced from the
surface of the body. The mask 52 is preferably adhered to the body
54 by a suitable adhesive to prevent shifting by the grit. The
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blasting grit is then directed over the mask, as before, to erode
the bare backing sheet 38 while having substantially no effect on
the polymerized areas 42, 44 and 46. The blasting grit is applied
until the desired depth in the body 54 is reached.
Particularly with some sensitive material such as glass or
mirrors, as where the silver layer on the back of the mirror is to
be removed, it is preferable to remove the backing sheet 38 before
blasting. Otherwise, as the blasting grit is applied, it may erode
some portions of the backing sheet faster than o~hers and cause
undesirable excessive erosion in portions of the grit-erodible ma-
terial. In such instances, with the mask in the position of Fig. 5,
the hardened areas 42, 44 and 46 are adhered more strongly to the
surface than the adherance between the hardened areas and the backing
sheet. The backing sheet then can simply be peeled away from the
hardened areas aEter they have been adhered to the grit-erodible
surEace and the blasting grit applLed in the same manner as before.
The mask can be reused by repositionin~ the light-struck areas
42, 44 and 46 on ano~her gr:lt-erodible body or on another backing
sheet, iE desirable and practLcal. Otherwise, new blasting masks can
be readily made by s:imply reusing the e~isting control sheet or
negative 22 in combination with the ultraviolet light 24 arld a new
blasting mask blank 26.
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