A spray coating apparatus is provided for rotating a workpiece relative to a spray station to obtain a uniform coating of the workpiece. In a typical example, the workpiece comprises a ceramic tile which is to be coated with a ceramic coating and the tile is to be used as a reusable component of the thermal protection system for a space shuttle. The apparatus for rotating the workpiece includes a base support having a first rotatable stage for rotation in the horizontal plane and a second rotatable stage for rotation in a second plane inclined at an angle, such as 45 degrees, to the horizontal plane and the workpiece is supported on this second stage. Thus the workpiece is rotatable in both of two planes of rotation

Katvala, V. W.

Porter, E. E.

Smith, M.

English

NASA Technical Reports Server

United States Patent [I91 [111 4,312,292 
Smith et al. [45] Jan. 26, 1982 
[54] SPRAY COATING APPARATUS HAVING A Primary Examiner-Shrive P. Beck 
ROTATABLE WORKPIECE HOLDER Attorney, Agent, or Firm-Darrell G. Brekke; John R. 
[75] Inventors: 
[73] Assignee: 
[21] Appl. No.: 
[22] Filed: 
Marnell Smith; Victor W. Katvala, 
both of San Jose; Ernest E. Porter, 
Saratoga, all of Calif. 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
945,040 
Manning 
PI ABSTRACT 
A spray coating apparatus is provided for rotating a 
workpiece relative to a spray station to obtain a uniform 
coating of the workpiece. In a typical example, the 
workpiece comprises a ceramic tile which is to be 
coated with a ceramic coating and the tile is to be used 
as a reusable component of the thermal protection sys- 
tem for a space shuttle. The apparatus for rotating the 
Sep. 22, 1978 workpiece includes a base support having a first rotat- 
[51] Int. ( 3 . 3  ....................... BO5C 11/00; B05C 13/02 
[52] U.S. c1. .................................... 118/320; 118/500, 
118/503; 118/505; 427/425 
[58] Field of Search ............... 118/500, 501, 502, 503, 
118/504, 505, 320; 427/421,425 
[561 References Cited 
U.S. PATENT DOCUMENTS 
1,368,338 2/1921 House .................................. 118/5OO 
1,544,120 6/1925 Zickos et al. ....................... 118/5OO 
2,755,507 7/1956 Heller ............................. 118/416 X 
3,390,660 7/1968 McDermott ........................ 118/6 X 
3,420,210 1/1969 Lindquist ........................ 118/500 X 
3,583,363 6/1971 Shrader ........................... 118/500 X 
3,828,727 8/1974 Bauerle ............................... 118/5OO 
3,912,249 10/1975 Vaca ............................... 118/500 X 
3,952,083 4/1976 Hetcher et al. .................. 264/66 X 
4,023,524 5/1977 Goldfarb et al. ............... 118/503 X 
4,068,792 1/1978 Dixon ............................. 118/505 X 
able stage for rotation in the horizontal plane and a 
second rotatable stage for rotation in a second plane 
inclined at an angle, such as 45 degrees, to the horizon- 
tal plane and the workpiece is supported on this second 
stage. Thus the workpiece is rotatable in both of two 
planes of rotation. The workpiece support is detachable 
from the first rotatable stage and the workpiece is 
readily detachable from the workpiece support to facili- 
tate off loading of the spray coated workpiece. The 
workpiece holder includes a spray guard extending 
around the periphery of the workpiece to shield that 
surface of the workpiece where no coating is desired. 
The two degrees of freedom provided in the rotation of 
the workpiece relative to the spray station permits the 
various facets of the tile to be sequentially rotated into 
an orthogonal relationship to the spray station for uni- 
form coating of the workpiece. 
2 claims, 3 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19820016616 2020-03-21T16:41:39+00:00Z
4,3 12,292 
I 
1 
493 
SPRAY COATING APPARATUS HAVING A 
ROTATABLE WORKPIECE HOLDER 
BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates, in general, to spray 
coating apparatus and more particularly to spray coat- 
ing apparatus for rotating a workpiece relative to a 
spray station to obtain uniform spray coating of the 
workpiece. 
This spray coating apparatus is designed for adaption 
to an automated spray station in an assembly line. 
(2) Description of the Prior Art 
Heretofore, spray coating devices have been pro- 
posed for spray coating of workpieces, such as shoes, 
wherein the workpiece was mounted for rotation in the 
horizontal plane about a vertical axis relative to a spray 
station so as to coat the workpiece uniformly on all sides 
facing the spray station. Such a spray coating apparatus 
is disclosed in U.S. Pat. No. 3,390,660 issued July 2, 
1968. 
5 
10 
15 
20 
292 
2 
onal relation to the spray station to obtain a uniform 
coating of the workpiece. 
In another feature of the present invention, the work- 
piece support structure includes a first detachable work- 
piece holder which is detachable from the first rotatable 
stage of the spray coating apparatus to facilitate han- 
dling of the coated workpiece. 
In another feature of the present invention, this inven- 
tion is designed to be incorporated into an automatic 
spray station in an assembly line. 
in another feature of the present invention, the work- 
piece holder includes upstanding lip portions for shield- 
ing the sides of the workpiece to prevent coating 
thereof in certain regions. 
In another feature of the present invention, the de- 
tachable workpiece holder includes a central aperture 
therein to facilitate removal of the workpiece from the 
workpiece holder. 
Other features and advantages of the present inven- 
tion will become apparent upon a perusal of the follow- 
ing specification taken in connection with the accompa- 
nying drawings wherein: 
It is also known from the prior art to place. a reusable 
surface insulation tile on a fixed pedestal and to spray 25 
the tile by moving the spray gun relative to the station- 
ary horizontal tile. Alternatively, it is known from the 
prior art to mount the tile to a model holding device 
and, while holding the tile on the model holding device 
in one hand, spraying the tile with the other hand. Reus- 30 
able surface insulation tiles are disclosed in U.S. Pat. 
No. 3,952,083 issued Apr. 20, 1976. 
A i‘’ strip along the bottom of each vertical side edge 
of the tile must be coating free. Therefore, masking tape EMBODIMENTS . 
was applied to that area before spraying. This masking 35 Referring now to FIGS. 1-3, there is shown a spray 
tape was ~ W I K N ~ ~  after the coating was dried but before coating apparatus 11 incorporating features of the pres- 
the coating was glazed. ent invention. The spray coating apparatus 11 includes 
In the prior art method wherein the tile rested in the a base support structure 12, such as a table, for provid- 
horizontal plane on the pedestal for spray coating, the ing support from a horizontal reference plane via the 
sides of the tile were vertical and the top of the tile was 40 intermediary of a stationary base plate 13. A turntable 
horizontal. A uniform coating of a specified thickness 14 is rotatably coupled to and supported from the base 
was difficult to achieve with this arrangement because plate 13 via a conventional vertical axle and ball bearing 
the coating slurries were of relatively low viscosity and assembly, not shown, vertically dependent from the 
often ran on the tile’s vertical sides while the coating turntable 14 and centrally disposed of the turntable. A 
deposited on the top of the tile was much thicker than 45 45 degree table 15 is fixedly secured to the turntable 14 
on its sides. via the intermediary of screws, not shown. The 45 de- 
When a hand-held holder was employed, it was cum- gree table 15 includes a major face portion 16 inclined at 
bersome to use and increased the possibility of handling 45 degrees to the horizontal plane and includes a cylin- 
damage to the coating. Neither of the prior art methods drical bore 17 axially aligned with the normal to the 45 
were amenable to large scale manufacturing of reusable 50 degree inclined face 16, 
insulation tile. In addition, the use of the masking tape to A second turntable 18 includes a dependent axle 19 
obtain an uncoated border along the bottom of the ver- which is received within the cylindrical bore 17 
tical sides of the tile was time consuming and when the through the major face of the 45 degree table 15 for 
masking tape was removed, the unfired.coating was rotation therein. The second turntable 18 includes a 
often damaged. 55 table portion 21 affixed to the axle 19 and having a 
major face 22 which is inclined at 45 degrees to the SUMMARY OF THE PRESENT INVENTION horizontal. 
The principal object of the present invention is the A detachable workpiece holder 23 is detachable cou- 
provision of an improved spray coating apparatus for pled to the second turntable portion 2P via the interme- 
spray coating of a workpiece and particularly suitable 60 diary of a plurality of dowels 24 depending from the 
for spray coating of reusable thermal insulation tiles. workpiece holder 23 and loosely fitting within aligned 
In one feature of the present invention, the workpiece bores 25 in the face 22 of the second turntable portion 
is mounted on a rotatable stage which is inclined at a 21. 
substantial angle to the horizontal. This rotatable stage The workpiece holder 23 can take any one of a num- 
is mounted on another rotatable stage which rotates in 65 ber of different configurations as depicted in FIG. 2 at 
the horizontal plane. Thus, the workpiece can be ro- 23, 2 3  and 23’. In the holder embodiments 23 and 23’, 
tated in two degrees of rotation, whereby the facets of the upper face of the workpiece holder includes a plu- 
the workpiece may be sequentially rotated into orthog- rality of upstanding pins 26 for insertion into the back 
BRIEF DESCRIPTION O F  THE DRAWINGS 
FIG. 1 is a perspective view of a spray coating appa- 
ratus incorporating features of the present invention, 
FIG. 2 is a view depicting the workpiece holder 
portion in exploded view and depicting alternative 
workpiece holder configurations, and 
FIG. 3 is a perspective view of the structure of FIG. 
2 taken in the direction of the arrow 3-3. 
DESCRIPTION OF THE PREFERRED 
4,3 12,292 
3 4 
face of the workpiece to be coated, such as a reusable As an alternative to employing dowels 24 and pins 26 
thermal insulation tile 27. A spray guard lip 28 extends for holding the workpiece holder 23 to the second turn- 
upwardly from the upper face of the workpiece holder table 21, and for holding the workpiece 27 to the holder 
23 for shielding the lower portions of the side edges of 23, the holder 23 with flat workpiece 27 in place Over 
the tile workpiece 27 from sprayed coating material. 5 the central aperture 34, may be held to the turntable by 
A spray coating station 29 is mounted to the reference vacuum. This is accomplished by boring a cylindrical 
base support, such as a table 31, via the intermediary of hole through the turntable 21 and axle 19 in axial align- 
a bracket 32 which Serves to clamp a spray gun 33 in ment therewith and coupling the bore in gas communi- 
position so that the spray from the spray gun is directed cation with a vacuum Pump via the intermediary of a 
at the workpiece 27 in the desired direction, i.e., normal 10 rotatable vacuum joint, not shown. Rotatable vacuum 
to the face of the workpiece 27 being spray coated. joints are commercially available from The Johnson 
Thus, in the preferred embodiment for spraying rect- Corporation of Three Rivers, Michigan as model 
angular tile 27, the central axis of the spray cone or fan #3100w ''IFree 
is directed at 45 degrees to the horizontal plane when 
horizontal. In this manner, the sprya is directed orthog- 
onally onto the surface being coated. The two turntable 
stages 14 and 21 permit successive facets of the rectan- 
gular workpiece to be sequentially rotated into spraying 
face being coated is perpendicular to the central ray of 
the spray cone emitted from the spray station 39. 
Once the workpiece 27 has been sprayed, the work- 
piece holder 23 is detached from the second turntable 25 
plane, is lowered onto a pedestal which passes up 
through a central aperture 34 in the workpiece holder, 
thereby separating the coated workpiece from the 
holder so that the next workpiece can be inserted into 3o 
the holder 27 and the process repeated. 
In a typical example, a 6" by 6' by 2" reusable surface 
insulation tile 27 is placed on the workpiece holder 23. 
The tile 27 is held in place by 4" long pins 26. The spray 
spaced away from the side edges of the tile 27 by 1/16 
inch. The workpiece holder 23, with the tile in place, is 
then set on the second turntable stage 21. The tile is then 
ready to be coated. Reaction cured glass coating for the 
space shuttle thermal protection is applied as a low 40 
viscosity slurry that is uniformly sprayed onto the tile 
27. A Binks model #69 spray gun with a type #66 noz- 
zle is used to spray the tiles. The spray gun 33 is held 
perpendicular to the surface being coated and at about 
6" to 8" away from the surface. The tile's sides are 45 
coated by moving the second turntable stage 21 so that 
each side surface faces the spray station 29 sequentially. 
The top surface is then moved to face the sprayer by 
rotating the first turntable stage 14. This procedure is 
repeated until the proper thickness of coating has been 50 
applied to the tile 27. Approximately 0.0012" to 0.0015" 
of coating is applied Per Pass. After coatin& the tile 27 
and tile holder 23 are removed from the second stage 
21. The tile is removed from the workpiece holder 23 by 
setting the tile 27 on a round pedestal projecting up 55 
through the center aperture 34 and lowering the tile 
holder away from the coated tile. This procedure takes 
less than 10 minutes per tile. 
The advantage in using the spray coating apparatus of 
the present invention is that it allows resuable surface 60 
insulation tile substrate to be coated with no masking 
and demasking, no handling of the wet coating, and 
gives a repeatable, uniformly thick coating. The spray 
coating apparatus makes automation of the coating 
process feasible. Use of the spray coating device for 65 
coating reusable surface insulation tile requires less time 
to coat each tile, lowers the scrapage rate, and the coat- 
ing process requires fewer and less skilled personnel. 
What is claimed is: 
the tile 27 is rotated in a plane at 45 degrees to the 15 1. In a spray coating apparatus for rotating a 
relative to a spray station to obtain a uniform coating of 
the 
a base plate for disposition on a horizontal reference 
On its front face and side surfaces: 
support plane; 
plate and free to rotate in a horizontal plane about 
a vertical axis of rotation; 
a table secured to said first turntable, said table hav- 
ing a major face portion inclined to the horizontal 
plane; 
face portion and free to rotate in e plane parallel to 
said major face portion about an axis of rotation 
normal to said major face portion; said second 
turntable having a number of bores each with a 
longitudinal axis parallel to said second turntable 
axis of rotation; 
a detachable tile holder adapted to be supported by 
said second turntable, said tile holder comprising; a 
plate face adapted to support the back face of the 
ti!e to be coated, a plurality of erect pins secured to 
said first plate face and adapted to impale the back 
face of the tile to be coated, a guard lip extending 
upwardly from said first face of said plate for 
shielding the lower portions of the side walls of the 
tile to be coated, a plurality of dowels secured 
normal to said second plate face, said dowels being 
slightly smaller than said second turntable bores 
and disposed in alignment with said bores so that 
said dowels may rest within said bores, and said 
plate having an aperture to receive a pedestal for 
separating a coated tile from said detachable tile 
holder. 
2. In a spray coating apparatus for uniformly coating 
a base plate for disposition on a horizontal reference 
support plane; 
a first turntable supported by and parallel to said base 
plate and free to rotate in a horizontal plane about 
a vertical axis of rotation; 
a table secured to said first turntable, said table hav- 
ing a major face portion inclined to the horizontal 
plane; 
a second turntable rotatably coupled to said major 
face portion and free to rotate in a plane parallel to 
said major face portion about an axis of rotation 
normal to said major face portion; said second 
turntable having a number of bores each with a 
longitudinal axis parallel to said second turntable 
axis of rotation; 
a detachable tile holder adapted to be supported by 
said second turntable, said tile holder comprising; a 
position relative to the spray station 29 so that the sur- 2o a first turntable supported by and parallel to said base 
stage 21 and the 23, as in the a second iurntable rotatably coupled to said major 
guard Or lip 28 is 4 of an high and is 35 plate with first and second opposite faces, said first 
the front face 2nd side surfaces of a tile: 
4,3 12,292 
5 6 
plate with first and second opposite faces, said first 
plate face adapted to support the back face of the 
tile to be coated, a plurality Of  erect pins secured to 
said first plate face and adapted to impale the back 
face Of the to be coated, a guard lip extending 
upwardly from said first face of said plate for 
shielding the lower portions of the side walls of the 
tile to be coated, a plurality of dowels secured 
normal to said second plate face, said dowels being 
slightly smaller than said second turntable bores 10 
and disposed in alignment with said bores so that 
said dowels may rest within said bores, and said 
separating a coated tile from said detachable tile 
holder; and 
a spray gun mounted in proximity to said tile holder 
for spraying a tile in said tile holder, said spray gun 
of revolu- 
tion made by the axis of rotation of the second 
turntable when the first turntable is revolved 
whereby said spray axis is normal to the front face 
of a tile in said holder when said first turntable is 
rotated until the front face of the tile is directly 
facing said spray gun. 
having a spray axis that lies on the 
plate having an aperture to receive a pedestal for * * * * *  
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Spray coating apparatus having a rotatable workpiece holder

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