U.S. patent number 3,893,578 [Application Number 05/458,884] was granted by the patent office on 1975-07-08 for system for injecting particulate material into the combustion chamber of a repetitive combustion coating apparatus.
This patent grant is currently assigned to Southwest Research Institute. Invention is credited to Elbert M. Hubbard, Rosser B. Melton, Jr..
United States Patent |
3,893,578 |
Melton, Jr. , et
al. |
July 8, 1975 |
System for injecting particulate material into the combustion
chamber of a repetitive combustion coating apparatus
Abstract
A repetitive combustion system for coating a work piece with
particulate material is disclosed which utilizes an encapsulating
tape having a plurality of discrete capsules each containing a
predetermined quantity of the particulate coating material. The
capsules are sequentially fed into a stripping chamber where the
tape is clamped between inlet and outlet manifolds which provide a
circumferential seal around the respective capsules so that
pressure can be applied to an inlet face of the capsule. The inlet
face is so configured as to admit air into the interior of the
capsule which then swells and bursts the outlet face or otherwise
passes through the outlet faces. The air pressure then injects the
particulate material into the combustion chamber while the pressure
in the combustion chamber is near the peak produced by combustion.
A number of different tape configurations are disclosed and also a
number of different stripping stations designed to enhance
scavenging of all of the particulate material from the capsules
without entraining any of the material forming the capsules and to
position the capsules to the station at a high rate. The coating
apparatus includes a sequencing means which feeds the tape at a
continuous rate through the stripping station and initiates
introduction of a fuel-air mixture to the combustion chamber,
ignition of the fuel-air mixture, and injection of the particulate
material from the stripping station in the proper sequence. High
speed rotary manifold systems for positioning these capsules at the
stripping station are also disclosed.
Inventors: |
Melton, Jr.; Rosser B.
(Helotes, TX), Hubbard; Elbert M. (Dallas, TX) |
Assignee: |
Southwest Research Institute
(San Antonio, TX)
|
Family
ID: |
23822473 |
Appl.
No.: |
05/458,884 |
Filed: |
April 8, 1974 |
Current U.S.
Class: |
414/412;
89/35.01; 206/484; 206/820; 222/94; 414/416.1; 221/74 |
Current CPC
Class: |
C23C
4/129 (20160101); B05B 7/144 (20130101); B05B
7/0006 (20130101); Y10S 206/82 (20130101) |
Current International
Class: |
B05B
7/00 (20060101); C23C 4/12 (20060101); B65g
065/04 () |
Field of
Search: |
;214/300,152,309,310,304,305 ;221/74 ;222/94 ;53/381R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Spar; Robert J.
Assistant Examiner: Oresky; Lawrence J.
Attorney, Agent or Firm: Hubbard, Thurman, Turner &
Tucker
Claims
What is claimed is:
1. A system for injecting predetermined quantities of particulate
coating material into a chamber of hot gases which comprises:
an elongated tape forming a plurality of discrete capsules each
containing a predetermined quantity of particulate coating
material, each capsule having an inlet face and an outlet face,
an inlet manifold and an outlet manifold for sequentially clamping
the tape to seal the inlet face from the outlet face,
the outlet manifold having a chamber configured to permit expansion
of the outlet face of each capsule and including an outlet port
having an area less than the area of the outlet face of the
capsule,
the inlet manifold including valve means for applying a pneumatic
pulse to the inlet face of the capsule of sufficiently higher
pressure to pass through the inlet face and burst the outlet face
thereby stripping the particulate material from the tape and
propelling the particulate material out through the outlet
port.
2. The system of claim 1 wherein the outlet manifold is configured
to restrain deformation of the outlet face of the capsule to limit
bursting of the outlet face of the capsule except over the outlet
port.
3. The system of claim 1 wherein
each capsule is elongated, and
the inlet manifold has an inlet port offset longitudinally of the
elongated capsule from the outlet port of the outlet manifold.
4. The system of claim 1 wherein the inlet manifold includes means
for piercing the inlet face of the capsule to permit the pneumatic
pulse to enter the capsule.
5. A system for injecting predetermined quantities of particulate
coating material into a chamber from an elongated tape forming a
plurality of discrete capsules, each encapsulating a predetermined
quantity of particulate coating material, each capsule having an
inlet face and an outlet face, said system comprising
an inlet manifold and an outlet manifold for sequentially forming a
seal between the inlet face from the outlet face of successive
capsules,
the outlet manifold having a chamber configured to permit expansion
of the outlet face of each capsule and including and outlet port
having an area less than the area of the outlet face,
the inlet manifold including valve means for applying a pneumatic
pulse to the inlet face of the pocket of sufficient magnitude to
pass through the inlet face and burst the outlet face thereby
stripping the particulate material from the tape and propelling the
particulate material out through the outlet port.
6. The system of claim 5 wherein the outlet manifold is configures
to restrain deformation of the outlet face of the capsule to limit
bursting of the outlet face of the capsule except over the outlet
port.
7. The system of claim 5 wherein
each capsule is elongated, and
the inlet manifold has an inlet port offset longitudinally of the
elongated capsule from the outlet port of the outlet manifold.
8. The system of claim 5 wherein the inlet manifold includes means
for piercing the inlet face of the capsule to permit the pneumatic
pulse to enter the capsule.
9. The system of claim 5 wherein
the inlet and outlet manifolds form an elongated chamber adapted to
receive an elongated capsule, and
the inlet manifold has an inlet port offset longitudinally from the
outlet port of the outlet manifold.
Description
The present invention relates generally to systems for coating work
pieces with particulate material, and more particularly relates to
an improved system for commercially distributing the particulate
material from the manufacturer, storing the particulate material in
a protected environment, handling the particulate material prior to
its use in a coating apparatus, and injecting a controlled quantity
of the particulate material at a precisely controlled instant and
location in the combustion chamber of a repetitive pulse coating
apparatus to produce a coating of improved quality.
Co-pending application Ser. No. 198,806, entitled "Method and
Apparatus for Applying Particulate Coating Material to a Piece of
Work", filed on Nov. 15, 1971 on behalf of Melton, et al., and
assigned to the assignee of the present invention, and U.S. Pat.
No. 2,972,500, disclose systems for applying particulate coating
material, such as tungsden carbide, to a work piece in a series of
pulses.
The system disclosed in the former utilizes a combustible fuel-air
mixture which is introduced to a combustion chamber having a
restricted outlet nozzle at a sufficient rate to increase the
pressure substantially above atmospheric pressure. The inlet valve
is then closed and the mixture ignited while the pressure is still
at a high level. The resulting combustion produces a still higher
pressure as a result of confinement by the restricted outlet
nozzle, and the hot gases of combustion then exit through the
restricted outlet nozzle at a high velocity during a blow-down
period. Particulate material is injected into the combustion
chamber, preferably near the end of combustion, and before the peak
pressure has been materially reduced. As a result, the particulate
material is both heated and propelled from the nozzle against the
work piece at a high velocity where the particulate material
flattens and adheres to the work piece to form the coating.
The system disclosed in U.S. Pat. No. 2,972,550 utilizes somewhat
the same technique, except that a detonatable mixture must be used
in a long, open-ended tubular combustion chamber designed to
sustain a detonation wave. The detonation wave results in a
substantially instantaneous pressure rise within the chamber as a
result of the very rapid combustion. Again, the hot gases heat the
particles, which must be injected just prior to detonation, and the
high pressure causes the gases to rush from the open end of the
tube thus propelling the particles at high velocity against the
work piece.
In each of these systems, the repetitive rate of the combustion
pulses is relatively high, on the order of 10 per second, for
example. Both the coating efficiency, i.e., the percent of
particles which adhere to the work piece, and the quantity of the
coat are highly dependent upon injecting the particles into the
combustion chamber in uniformly repetitive quantities at precisely
the right instant. One of the principal difficulties with each of
the previous systems resided in the particle injection systems
employed. Each system has utilized a bulk hopper for the
particulate material and some type of mechanical-pneumatic
dispensing system for measuring and injecting the very small
quantity of particulate material required for each "shot". Bulk
handling of the particulate material results in undesirable
segregation of large particles from small particles. Such systems
are also generally unreliable because the particulate material
tends to cake and feed unevenly from the bulk hopper. Further, the
high speed pneumatic transport of the highly abrasive particulate
material results in extremely rapid abrasion of the penumatic
valving and conduits which often fail. Further, many particulate
materials are subject to oxidation and other adverse effects as a
result of being subjected to humidity of the atmosphere, and
protection from oxidation is very difficult during bulk handling of
these materials at the coating site.
U.S. Pat. No. 3,461,268 discloses a system wherein particulate
material is encapsulated in pockets of a tape and positioned at the
outlet end of a high voltage spark chamber. The spark in the
chamber results in an explosion which propells both the heated
particles and the material forming the package against the work
piece to form a coating. While such a spark system may be suitable
for some types of coating, the entrainment of the material forming
the encapsulating tape materially and adversely affects the quality
of the type of coatings of interest in the present application.
The present invention is concerned with improved encapsulating
tapes, improved particulate powder injection stations adapted to
use the improved encapsulating tape, coating systems having an
improved control system which is responsive to the position of the
encapsulating tape, and methods relating thereto.
The system of the present invention utilizes a method which
comprises encapsulating the particulate material in an enclosure
having inlet and outlet faces, injecting air pressure through the
inlet face into the interior of the capsule to expand the capsule
and burst the outlet face, and directing the entrained particulate
material into co-mingling relationship with hot gases which heat
and accelerate the particulate material against a work piece.
In accordance with another aspect of the invention, the
encapsulating tape is formed of two film strips, one of which is
configured in such a manner as to facilitate the passage of
pneumatic pressure into the interior of the capsule so that the
outlet face can be burst by the pneumatic pressure. Preferential
pneumatic penetration points, either openings or weakened areas, in
the inlet face can be formed on the tape during manufacture or can
be initiated mechanically at the stripping station.
In accordance with another aspect of the invention, the stripping
station and tape are configured in such a manner as to facilitate
selective penetration of the inlet face of the capsule by the air
pressure and bursting of a preselected area of the outlet face so
as to establish a turbulent flow path within the capsule by the air
to encourage complete scavenging of the particulate material from
the capsule.
The invention further contemplates a control system wherein the
encapsulating tape is pulled past the stripping station with a
continuous uniform force. The position of a capsule as it
approaches the stripping station is sensed and a combustion cycle
initiated in response to the capsule arriving at the predetermined
point. The tape is momentarily clamped at the stripping station
while the particulate material is pneumatically stripped from the
interior of the capsule and injected into the combustion
chamber.
The invention also contemplates a rotary system for stationing the
capsules of the encapsulating tape at the stripping station to
permit high repetition rates of the combustion cycle, and special
tape configuration suitable for use with such systems.
The novel features believed characteristic of this invention are
set forth in the appended claims. The invention itself, however, as
well as other objects and advantages thereof, may best be
understood by reference to the following detailed description of
illustrative embodiments, when read in conjunction with the
accompanying drawings, wherein:
FIG. 1 is a schematic block diagram of a system for coating a work
piece with particulate material which utilizes the present
invention;
FIG. 2 is a timing diagram which serves to illustrate the operation
of the system of FIG. 1;
FIG. 3 is a plan view of an encapsulating tape in accordance with
the present invention;
FIG. 4 is a sectional view taken substantially along lines 4--4 of
FIG. 3;
FIG. 5 is a sectional view taken substantially along lines 5--5 of
FIG. 3;
FIG. 6 is a perspective view of the encapsulating tape of FIG.
3;
FIG. 7 is a simplfied sectional view of the tape stripping station
of the system of FIG. 1, with the sectional view taken through the
center of the stripping station in a direction extending
longitudinally of the encapsulating tape;
FIG. 8 is a sectional view extending through the center of the
stripping station, and taken at right angles to the sectional view
of FIG. 7;
FIG. 9 is a sectional view similar to FIG. 8 illustrating the
operation of the stripping station;
FIG. 10 is a sectional view similar to FIG. 8 showing another
stripping station in accordance with the present invention;
FIG. 11 is a plan view of another encapsulating tape in accordance
with the present invention;
FIG. 12 is a sectional view taken substantially on lines 12--12 of
FIG. 11;
FIG. 13 is a sectional view of another stripping station in
accordance with the present invention for the encapsulating tape of
FIG. 11;
FIG. 14 is a perspective view of still another encapsulating tape
in accordance with the present invention;
FIG. 15 is a perspective view of yet another encapsulating tape in
accordance with the present invention;
FIG. 16 is a perspective view showing still another encapsulating
tape in accordance with the present invention;
FIG. 17 is a perspective view, partially broken away, illustrating
another encapsulating tape in accordance with the present
invention;
FIG. 18 is a sectional view similar to FIG. 7 illustrating another
stripping station in accordance with the present invention for use
with the encapsulating tape of FIG. 17;
FIG. 19 is a sectional view taken at right angles to the sectional
view of FIG. 18 and extending through the center of the stripping
station;
FIG. 20 is a view similar to FIG. 19 illustrating the operation of
the stripping station of FIG. 18;
FIG. 21 is a perspective view, partially broken away, of still
another encapsulating tape in accordance with the present
invention;
FIG. 22 is a sectional view similar to FIG. 8 illustrating a
stripping station for use with the encapsulating tape of FIG.
21;
FIG. 23 is a simplified side view, partially in section of another
stripping station in accordance with the present invention;
FIG. 24 is a sectional view taken substantially on lines 24--24 of
FIG. 23;
FIG. 25 is a plan view of another encapsulating tape in accordance
with the present invention;
FIG. 26 is a sectional view taken substantially on lines 26--26 of
FIG. 25;
FIG. 27 is a sectional view taken substantially on lines 27--27 of
FIG. 25;
FIG. 28 is a simplified plan view illustrating a stripping station
designed to utilize the encapsulating tape of FIG. 25; and
FIG. 29 is a sectional view taken substantially on lines 29--29 of
FIG. 28.
Referring now to the drawings, a system for coating particulate
material on a work piece 10 is indicated generally by the reference
numeral 12 in FIG. 1. The system 12 includes a combustion chamber
14 having a restricted outlet nozzle 16. A combustible fuel-air
mixture is formed by means of a carburator 18 which mixes fuel a
source 20 with compressed air from a source 22. The fuel-air
mixture is fed into the combustion chamber through an inlet valve
18 and is ignited by the spark plug 24 of an ignition system
26.
A particulate material injector system indicated generally by the
reference numeral 30 injects measured quantities of particulate
material into the combustion chamber 14. The injector system 30
includes a reel of encapsulating tape 50 which is fed through a
capsule sensor 52 past a stripping station 54 and over a tensioning
idler roller 56 to a take-up reel 58. A control circuit 60 responds
to a signal from the sensor 52 and initiates the proper sequence of
operation for each combustion cycle as will hereafter be described
in greater detail.
The encapsulating tape 50 is shown in greater detail in FIGS. 3-6,
and includes a relatively thick plastic film strip 62 and a
relatively thin plastic film strip 64. Each of the film strips may
conveniently be polyethylene or a similar plastic material
preferably of the type which can be heat welded. The relatively
thick film strip 62 is embossed with a series of elongated pockets
66 extending transversely of the tape. Each of the pockets has an
arcuate cross-section as illustrated in FIG. 4 with generally
flattened ends 66a as can best be seen in FIGS. 5-6. The effect of
the arcuate cross-section and flattened ends of the pockets 66 is
to provide a structure which is resistant to crushing under a
pressure load applied in a direction indicated by the arrows 68 in
FIG. 4 when the flat portion of the tape 62 is clamped between
inlet and outlet manifolds as will presently be described. A pair
of T-cuts 70 in each end of each of the pockets 66 extend
completely through the film strip 62 and form a pair of flaps which
can open when subjected to the air pressure represented by the
arrows 68, but which are normally resistant to movement in the
opposite direction by the curvature of the arcuate portions of the
pockets so as to retain the particulate material. The relatively
thin film strip 64 is sealed to the relatively thick film strip 62
by a thermal weld extending around the entire periphery of each of
the pockets 66 to form a capsule encapsulating a quantity of
particulate material 72.
It is desirable that the material selected for the thin film strip
64 tear, but not fragment, when subjected to a sudden blast of very
high pressure air to prevent pieces of the material from entering
the combustion chamber. Polyethylene film on the order of 0.0005
inches thick may be used for this purpose. The thicker film 62 may
also be polyethylene on the order of 0.004 inches thick. The total
width of the encapsulating tape may be on the order of 0.375 inches
and each pocket on the order of 0.280 inches and 0.080 inches wide.
Of course, the size and shape of the pockets may vary widely
depending upon the amount of particulate material which is to be
injected during each combustion cycle as will presently be
described.
Referring now to FIG. 7, the stripping station 54 includes an
output manifold 80 and an input manifold 82 which together form a
pneumatic stripping chamber 84. The output manifold 80 has a short
passageway 86 leading directly into the combustion chamber as can
be seen in FIG. 1. The input header 82 may be raised to permit the
successive capsules of the encapsulating tape 50 to be indexed into
position in the stripping chamber, then lowered to clamp the tape
around the periphery of the respective capsules as will presently
be described. A valve 88 admits high pressure air from the
compressed air source 22 to the stripping chamber 84. The injection
port 86 is continually open to the combustion chamber.
The input manifold 82 has a cavity configured to closely receive
each of the pockets 66 as illustrated in FIG. 8. The output header
80 has a cavity configured as illustrated in the sectional views of
FIGS. 7 and 8 to permit expansion of the outlet face to provide
free particle circulation within the expanded capsule, yet confine
the expanding force sufficiently to cause it to rupture over the
port 86. The input manifold 82 has a pair of orifices 90 and 92
disposed over the T-cuts 70 at the ends of the capsules. The output
manifold 80 has a pair of opposite shoulders 94 to guide the
encapsulating tape 50 as it is moved past the stripping
station.
In the operation of the system 12, the leader from the
encapsulating tape 50 is threaded through the sensor 52, through
the stripping station 54 and over the idler roller 56 to the
take-up reel 58. When it is desired to initiate coating, the
take-up reel 58 is actuated to begin pulling the tape 50 through
the stripping station 54 at a uniform rate. When the sensor 52
detects the presence of a capsule 66, the sequence of events
illustrated in FIG. 2 is initiated. The event 100a on the top line
100 represents when a capsule 66 is approaching the stripping
chamber. The inlet valve 19 begins to open as represented by event
102a on the time line 102. As the valve 19 is closing at event
102b, the voltage is applied by the ignition system 26 to the spark
plug 24 is represented by event 104a on time line 104. The
combination of the valve 19 opening and the spark from the spark
plug 24 results in a pressure within the chamber represented by
line 106. The gradually sloping segment 106a represents the period
while the pressure in the chamber rises due to the fuel-air mixture
being input through the valve 19, the sharp rising segment 106b
represents the pressure rise due to combustion of the mixture in
the chamber, and the declining segment 106c represents the period
during which the gases of combustion blow out through the nozzle
16.
At some time before application of the ignition voltage, the inlet
manifold 82 is moved downwardly to clamp the encapsulating tape as
represented by event 108a on time line 108. As soon as the tape has
been clamped, the injection valve 88 is opened as represented by
event 110a on time line 110. As a result, the very high pressure
air, represented by event 112a on time line 112, jets through the
orifices 90 and the pressure and impact deflects the flaps formed
by the T-cuts 70, and the capsule is pressurized. This pressure
stretches the thin film 64 downwardly against the lower face of the
stripping chamber formed by the outlet manifold 80 and the thin
film is stretched until it bursts over the outlet 86. The turbulent
conditions of the air within the capsule very effectively and very
instantly purge all of the particulate material from the capsule
and pneumatically convey it out through the passageway 86. The
coating period is represented by event 114a on time line 114.
As a result of the resistance of the arcuate pocket 66 to being
collapsed by the pressure applied to the top, and because of the
preferential entry of the pressure through the T-cuts into the
interior of the capsule, the two films cannot be held together by
the flow of air to trap particles between the films. The very low
volume of the cavity between the valve 88 and the stripping chamber
assures a very high response rate to the opening of the valve 88,
so that the particulate material 72 is injected into the combustion
chamber in a very short period of time. This assists in insuring
that all of the particles are heated to the same extent and are
propelled out of the combustion chamber at nearly the same velocity
so as to provide a high coating efficiency and a coating of
improved quality.
An alternative embodiment of the stripping station is indicated
generally by the reference numeral 112 in FIG. 10. The stripping
station 112 may utilize an encapsulating tape 50a which may be
identical to the encapsulating tape 50, except that the T-cuts 70
are eliminated. The station 112 may be substantially identical to
the station 54 and, accordingly, corresponding components are
designated by the same reference numerals followed by the reference
character a. The only significant difference in the station 100
from that of the station 54 is that a piercing device 114 is
provided to mechanically puncture the ends of the capsules of the
tape 50a, in lieu of the T-cuts. The piercing device 114 has a pair
of downturned sharp prongs 114a which pierce the capsules 66a as
the inlet header 82a is lowered to clamp the tape prior to opening
the valve 88a. The archshaped configuration of the capsules and the
particulate material provides sufficient resistance to crushing to
permit the prongs 114a to penetrate the relatively thick film. This
structure permits the high pressure air to gain access to the
interior of the capsule without crushing the upper film so that the
particulate material is scavenged from the interior of the pocket
as previously described in connection with FIG. 9.
Another encapsulating tape in accordance with the present invention
is indicated generally by the reference numeral 120 in FIGS. 11 and
12. The encapsulating tape 120 is formed by a relatively thick film
strip 122 which is embossed to provide a series of dome-shaped
pockets 122a and a relatively thin film 124 which seals a measured
quantity of particulate material 126 in each of the dome-shaped
pockets. The top of each dome-shaped pocket 122a is dimpled to
provide a very thin section 122b which will yield and be perforated
by high pressure applied to the surface of the dome before the dome
collapses.
The encapsulating tape 120 may be used in a stripping station, such
as station 54, having input and output manifolds 130 and 132,
respectively, configured as illustrated in FIG. 13. The manifolds
have circular cavities 130a and 132a, respectively, and inlet and
outlet orifices 130b and 132b, respectively. When high pressure is
applied through inlet orifice 130b, the high pressure penetrates
the thin dimpled section 122b so that the pressure enters the
interior of the capsule, expanding the lower film 124 downwardly
until it bursts over the outlet orifice 132b.
Another encapsulating tape in accordance with the present invention
is indicated generally by the reference numeral 140 in FIG. 14. The
encapsulating tape 140 may be identical to the encapsulating tape
120 except that the top of the dome is provided with a series of
line cuts 142 to facilitate entry of the high pressure air into the
interior of the capsule before the dome 144 collapses. The pie
shaped flaps formed by the line cuts 142 function somewhat as a
checkvalve to hold the particulate material inside the dome, yet
admit air pressure from outside the dome.
Still another encapsulating tape in accordance with the present
invention is indicated generally by the reference number 150 in
FIG. 15. Encapsulating tape 150 has a series of T-cuts 152 disposed
around the periphery of a generally flat surface 154 of a dome 156
impressed in a relatively thick film strip 158. Particulate
material is encapsulated inside the dome 156 by a relatively thin
film strip 159. The encapsulating tape 150 may also be used in a
stripping station having manifolds similar to that illustrated in
FIG. 13.
It will be noted that the T-cuts 152 are arranged so that when
subjected to high pressure above the dome, the flaps formed by the
T-cuts tends to divert the air tangentially around the interior of
the dome, thereby imparting a swirling motion to the air to
facilitate complete scavenging of the particulate material from the
interior of the dome. Further, the swirling motion of the air
imparts a swirling motion to the particles as they pass through the
outlet orifice 132b. The swirling trajectory of the particles cause
the particles to be sprayed outwardly within the combustion chamber
to increase retention time in the combustion chamber, and thus
heating.
Still another encapsulating tape in accordance with the present
invention is indicated generally by the reference numeral 160 in
FIG. 16. The encapsulating tape 160 is similar to the encapsulating
tape 150, except that V-shaped cuts 162 are made around the
periphery of the flat surface 164 rather than the T-shaped cuts 152
of the tape 150. The operation of the pie-shaped flaps formed by
the cuts 162 is substantially the same as that of the T-cuts
152.
Another encapsulating tape in accordance with the present invention
is indicated generally by the reference numeral 200 in FIG. 17. The
encapsulating tape 200 has a relatively thick film strip 202 which
is flat, and a relatively thin film strip 204 which is indented to
form a series of pockets 204a extending transversely of the tape.
The two film strips are bonded around the pocket 204a to form
discrete capsules each containing a particulate coating material.
The relatively thick film strip 202 has embossed areas 206 at each
end of each of the pockets 204a which are substantially thinner
than the remainder of the film strip 202. The embossed areas 206
are formed by a hot die applied to the thick film strip 202 before
the particulate material 208 is sealed in the capsules so that a
thickened ridge 206a is formed around the periphery of the
areas.
The encapsulating tape 200 may be used in the stripping station
indicated generally by the reference numeral 210 in FIG. 18. The
stripping station 210 has an inlet manifold 212 and an outlet
manifold 214. The inlet manifold 212 may be raised and lowered
relative to the output manifold 214, which may be stationary
relative to the combustion chamber. The inlet header includes a
valve 216, which controls the application of pneumatic pressure to
a pair of ports 218 which are best illustrated in FIG. 19. The
input manifold 212 may have side rails 220 and 224 to guide the
tape 200. The cavity 226 formed in the outlet manifold 214 is sized
somewhat larger than the pocket 204a.
The operation of the stripping station 210 and the encapsulating
tape 200 is illustrated in FIG. 20. The inlet manifold 212 is first
lowered against the outlet manifold 214 to clamp the encapsulating
tape 200 around the periphery of the capsule formed by pocket 204a.
Then the valve 216 is opened to admit air through the ports 218.
The high pressure, together with the impact of the high velocity
air, causes the embossed areas 206 to rupture and admit air into
the interior of the capsule. The air expands the relatively thin
film forming the pocket 204a until the film ruptures over the
outlet port 227. The particulate material is then swept out through
the port 227 and injected into the combustion chamber as previously
described. The indirect route the air must follow from inlet ports
218 to output port 227 causes considerable turbulence and complete
scavenging of the particulate material from the interior of the
chamber.
Still another encapsulating tape in accordance with the present
invention is indicated generally by the reference numeral 240 in
FIG. 21. The encapsulating tape 240 includes a relatively thick
film strip 242 and a thin strip 244 as heretofore described. The
thin film strip 244 is indented to form pockets 244a which are
elongated and extend transversely of the encapsulating tape as
heretofore described in connection with the encapsulating tape 200.
The relatively thick film strip 242 has a single aperture 246 cut
over one end of each of the pockets 244a, and the aperatures 246
are sealed by a second thin film strip 248 bonded to the relatively
thick film strip.
The particulate material 250 may be stripped from the encapsulating
tape 240 using a stripping station indicated generally by the
reference numeral 252 in FIG. 22. The stripping station 252 may be
very similar to the stripping station 210 except that a single
inlet port 254 is provieed in the inlet manifold 256, and the
outlet port 258 of the outlet manifold 260 is located at the
opposite end of the stripping chamber. As a result, when high
pressure air is applied to the thin film strip 248, the thin film
breaks first admitting air into the interior of the capsule. The
air pressure then expands the thin film forming pocket 244a until
it bursts over the outlet port 258. The offset between the inlet
and outlet ports results in longitudinal flow through the capsule
and high turbulence within the stripping chamber, thus completely
scavenging the particulate material from the capsule.
Another stripping station in accordance with the present invention
which may be used to strip particulate material from the
encapsulating tape 50 is indicated generally by the reference
numeral 300 in FIGS. 23 and 24. The stripping station 300 includes
an output manifold 302 having a cavity 304 which communicates with
an outlet port 306 leading to the combustion chamber. A turret 308
is journaled on an axle 310 and has an outer surface which comes in
close proximity to the end of the outlet manifold 302. A plurality
of inlet manifold cavities 312 are formed in the outer surface of
the rim 313 of the turret 308 and are spaced to receive the
successive capsules 66 of the tape 50. The inside surface 314 of
the rim 313 provides a cylindrical sealing surface which mates with
an inlet header assembly 316 to provide a sliding seal. Each of the
cavities 312 communicate with the sealing surface 314 through a
pair of ports 320 which are best seen in FIG. 24. The header
assembly 316 has a port 322 which registers with a pair of ports
320 disposed at the stripping station and communicates through a
valve 324 to the high pressure pneumatic source. The entire turret
308 and input header assembly 316 may be moved toward the output
mandril 302 to clamp the tape and effect a peripheral seal or the
peripheral seal may be provided by the tape being wedged between
the outer surface of the rim 313 and the output manifold assembly
302. In operation, the turret 308 preferably rotates at a constant
speed with the combustion cycle initiated at the appropriate time
by the control system so that the capsule 66 will be positioned
over the stripping cavity 304 at the instant when the powder is to
be injected into the combustion chamber. The valve 324 is then
merely opened and the high pressure gases pass through the ports
320 and through the capsule as previously described in connection
with FIG. 9.
Another encapsulating tape in accordance with the present invention
is indicated generally by the reference numeral 350 in FIG. 25. The
tape 350 is comprised of a pair of film strips 352 and 354 which
may be heat welded together. The flat film strip 354 may be of
about the same thickness as film strip 354. The film strip 352 has
a series of deep draw pockets 352a having a generally rectangular
configuration extending transversely of the tape as illustrated in
FIG. 25, and an arcuate cross-section as illustrated in FIG. 26.
The end surfaces 352b are disposed at near right angles to the
plane of the tape 350 so that the deep draw pockets cause the end
surfaces to be relatively thin compared to the portion of the
pocket forming the arch. The end surfaces thus become preferential
pneumatic fail points when the tape is used in the stripping
station indicated generally by the reference numeral 400 in FIGS.
28 and 29.
In the stripping station 400, the tape 350 is passed between a
rotary turret 402 and a rotary back-up wheel 404. The rim of the
turret 402 is provided with a plurality of cavities 406 sized and
spaced to closely receive the capsules 352a of the tape 350. The
back-up wheel 404 may be spring biased toward the rim of the turret
402 to clamp the web of the tape 350 and form a peripheral seal
around each capsule. A pair of valve plates 410 and 412 are mounted
on opposite edges of the rim of the turret 402. An inlet header 416
has a port 418 which communicates with the high pressure air
source. The valve plate 410 has a port 420 associated with each of
the cavities 406. Similarly, the valve plate 412 has an outlet port
422 which communicates with each of the cavities 406. The outlet
manifold 424 has a port 426 which communicates directly with the
combustion chamber.
In operation, the turret 402 and the back-up wheel 404 are rotated
at a uniform speed. The combustion cycle of the system is initiated
at the proper point of travel of the turret 402 so that the port
420 will be aligned with the port 418 at the instant when it is
desired to inject the powder into the combustion chamber. Thus, as
each successive port 420 registers with the port 418, high pressure
air is valved into the sealed chamber formed by the turret 402 and
the back-up wheel 404. The high pressure on the weakened end faces
352b of the capsule burst as a result of the pressure and the
powder is blown through the port 426 and injected in the combustion
chamber.
From the above detailed description of preferred embodiments of the
invention, it will be appreciated by those skilled in the art that
a system has been described wherein particulate material can be
injected into a high pressure combustion chamber of a
combustion-type coating system over a very short interval of time
initiated at the precise instant required to optimize coating
efficiency. Additionally, the system promotes complete scavenging
of the capsule without entraining the material forming the capsule
in the pneumatic stream for injection into the combustion chamber,
thus assuring that the encapsulating material will not interfere
with the quality of the coat being applied to the work piece. Where
desired, the particulate material may be encapsulated in a
moisture-proof encapsulating tape at the material manufacturing
plant to protect the particulate material from moisture and
oxidation. The encapsulation also prevents segregation of the
different sizes of particulate material, and further insures an
even and controlled feed of the particulate material to enhance the
control which can be exercised in maintaining a uniform coating
thickness.
Although preferred embodiments of the invention have been described
in detail, it is to be understood that various changes,
substitutions and alterations can be made therein without departing
from the spirit and scope of the invention as defined by the
appended claims.
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