Method for mass production assembly of fluidic devices

A method is disclosed for assembling fluidic spray devices wherein a fluidic element formed on the surface of a body member is expeditiously sealed to form the device. The essence of the invention is the injection molding of plastic around or through the body and a cover plate, or into a prefabricated housing into which the body member is inserted, to preload the parts and force them into a permanent sealed assembly. In one embodiment the preloading is achieved by shrinkage tension of injected plastic material surrounding or penetrating the parts. In a second embodiment the preloading is achieved by injecting plastic material into a gap or gaps in a product housing containing the body member so as to force the element surface against a sealing surface.

TECHNICAL FIELD 
The present invention relates to assembling fluidic devices and, more 
particularly, to an improved assembly technique whereby fluidic devices 
can be mass produced inexpensively and reliably. 
BACKGROUND ART 
It is by now well known that fluidic elements are particularly well suited 
for serving as spray nozzles. For examples, see U.S. Pat. Nos. 3,423,026; 
3,432,102; 3,458,888; 3,563,462, 3,638,866; 3,741,481; 3,973,558; 
4,052,002; 4,151,955; 4,157,161 and 4,184,636. These patents disclose 
fluidic spray nozzles which are fabricated by a variety of techniques. In 
most cases the fluidic element is defined in the surface of a body member 
and then sealed by a cover plate. Sealing is usually effected by adhesive, 
screws, ultrasonic bonding, or similar techniques. These techniques are 
generally time consuming and rather unsuitable for mass production. There 
have been a few prior art attempts to avoid these disadvantages. For 
example, in one technique the fluidic element is formed on one surface of 
a plate which is forced into a housing through a slot sized to hold the 
plate under compression while retaining the plate in the housing. In 
practice this technique has experienced fracture of the housing, leakage 
of spray fluid, and other disadvantages. 
Another attempt to solve the problem is found in the aforementioned U.S. 
Pat. No. 4,151,955 which discloses a particular type of fluidic oscillator 
which can be molded in one piece, thereby eliminating the need for a 
sealing plate and avoiding the requirement for an assembly step in the 
fabrication process. This technique has utility only for the particular 
fluidic oscillator disclosed and is also sensitive to dimensions in the 
mold which change with use and age. 
It is an object of the present invention to overcome the disadvantages of 
prior art techniques and provide an efficient method for mass producing 
fluidic spray devices. 
DISCLOSURE OF THE INVENTION 
In accordance with the present invention, a fluidic element formed in the 
surface of a body member is sealed against a sealing surface by 
pre-loading the body member against the sealing surface with injection 
molded plastic material. The injection molding may take place in a 
separate mold wherein the injected plastic material is permitted to 
surround a portion of the body member and cover plate within the mold 
cavity. Alternatively, the "mold" may be the final housing for the spray 
device whereby the plastic material is injected into a gap in the housing 
to force the body member against a cover plate or a housing surface to 
effect sealing. In another alternative, the plastic material may be 
injected through suitably provided holes of rivet-like cross-section in 
the body member and cover plate whereupon the plastic shrinks on cooling 
and binds the cover plate and body member together in sealing relation.

BEST MODE OF CARRYING OUT THE INVENTION 
Referring to FIG. 1, a fluidic oscillator 10 is shown as recessed passages 
defined in the top surface 11 of a body member 12. The recessed passages 
are sealed by means of a cover plate 13 disposed flush against surface 11. 
A pair of passages 14 and 15 conduct working fluid to and from the 
oscillator 10. Fluidic oscillator 10 may be any fluidic oscillator, such 
devices and their fabrication being well known. By way of example, the 
oscillator may take any of the forms illustrated and described in my U.S. 
Pat. Nos. 3,741,481; 4,157,161 and 4,184,636. 
Body member 12 and cover plate 13 are shown disposed between two 
schematically represented conventional mold halves 16 and 17 such that a 
continuous gap or space 18 surrounds portions of the abutting member and 
cover plate. Upon injecting plastic into space 18 and then letting the 
injected plastic solidify, a band of plastic is formed to match the 
contour of space 18. The band of plastic shrinks about the body member 12 
and cover plate 13, thereby forcing the cover plate and body member 
together to seal the oscillator 10. The finally assembled unit therefore 
is made up of the cover plate 13, the body member 12 and the plastic 
material injected into space 18. 
It should be noted that the body member 12 and cover plate 13 may be made 
of plastic in which case it may be desirable for the injected plastic to 
have a lower melting temperature than that used for the body member and 
cover plate; this, however, is not an imperative feature and all three 
parts can be made of the same plastic material if desired. It should also 
be noted that the body member 12 and cover plate 13 need not be plastic 
but could instead be metal or other suitable material which retains its 
shape. 
A similar arrangement is illustrated in FIGS. 2 and 3 wherein the final 
product, instead of having an outlet tube, is provided with an outlet 
opening so that fluid may be sprayed into the surrounding environment from 
the device. Specifically, a body member 22 has a fluidic oscillator 20 
defined in its upper surface 21. Oscillator 20 may be of the same type 
described for oscillator 10. A cover plate 23 is disposed over surface 21 
and the two pieces are placed between mold halves 26 and 27. Body member 
22 includes a depending stem portion 24 through which a fluid supply bore 
25 is longitudinally defined. The oscillator 20 is defined in surface 21 
at a location where the oscillator outlet region 29 opens to the edge of 
the body member 22 whereby fluid from the oscillator can be sprayed into 
the surrounding ambient environment (after the device has been removed 
from the mold halves). 
The body member 22 and cover plate 23 are provided with a cut away portion 
in the form of a band 28 extending entirely about the body member and 
cover plate. This band 28 defines a gap between the mold halves 26, 27, 
surrounding the device but within the extreme outer confines of the body 
member and cover plate. This gap communicates with an injection molding 
inlet 30 defined in the mold halves (for example, mold half 27). Upon 
injection of molten plastic through nozzle 30, the plastic fills gap 28 
and solidifies upon cooling. The solidified plastic shrinks about the body 
member 22 and cover plate 23, binding these two elements together in 
sufficiently tight engagement to seal the fluidic oscillator defined in 
surface 21. 
Whereas the device of FIG. 1 is useful for connection in a fluid system to 
which tubes 14 and 15 are suitable for connection, the device of FIGS. 2 
and 3 is suitable for use as a spray nozzle. 
The technique illustrated in FIGS. 1-3 for assembling a body member and 
cover plate in pressure-sealing relationship can be employed without the 
need for mold or die cavity members. One example of this is illustrated in 
FIG. 4. An oscillator 40 is defined in a body member 42 and covered by 
cover plate 43. A housing 45 is provided with an internal cavity, open to 
ambient at one end, into which the abutting body member 42 and cover plate 
43 are inserted. Housing 45 includes a depending stem 44 in which a 
longitudinal inflow bore 46 is defined. Bore 46 aligns with a passage 41 
defined through body member 42 when the body member is fully inserted into 
the housing cavity. Passage 41 supplies fluid under pressure to oscillator 
40 when such fluid is applied to inlet bore 46. 
The body member 42 and cover plate 43 fill all but a relatively small flat 
space or gap 47 of the housing cavity. This gap is located adjacent the 
cover plate 43 and must be so located that it can be filled with injected 
plastic which, upon solidifying, compresses the body member and cover 
plate together to permanently seal the oscillator within housing 45. In so 
doing, the upper end of inlet bore 46 is urged against body member 42 to 
prevent leakage of inflowing spray fluid. A suitable injection passage 48 
is defined in housing 45 to permit the molten plastic to be injected into 
the gap. The resulting spray device includes the body member 42, cover 
plate 43, housing 45 and the injected plastic in what had been gap 47. 
Fluid to be sprayed is received via stem 44 and sprayed from the right end 
(as viewed in FIG. 4) of the oscillator in a spray pattern which depends 
upon the particular oscillator configuration. 
It is possible to provide a device according to the present invention which 
is similar to that of FIG. 4 but wherein the cover plate 43 can be 
eliminated. Such a device is illustrated in FIG. 5 wherein a body member 
52 is inserted into a cavity defined in a housing 55. A fluidic oscillator 
50 is defined in one surface of the body member and is disposed flush 
against one interior wall of the housing. The opposite interior wall of 
the housing is slightly spaced from body member 52 to define a gap 57. 
Injection inlet passage 58 is defined through housing 50 to permit molten 
plastic to be injected into gap 57. A housing stem 54 depends from the 
housing and has a fluid supply bore 56 defined longitudinally therethrough 
to communicate with oscillator 50. The housing may be provided with an 
apertured tab-like extension 53 to facilitate mounting to another body, if 
desired. 
Referring to FIG. 6, a body member 62, having a fluidic oscillator 60 
defined in a surface thereof, is inserted into a suitably provided 
through-slot or cavity in a housing 65. The body member includes inlet and 
outlet tubes 64, 66 provided as an integral part thereof and extending out 
from opposite ends of the housing slot. The side of the body member 
opposite oscillator 60 is provided with a recessed area which defines a 
gap 67 between the body member and housing wall. An injection inlet 
passage 68 communicates with gap 67. This arrangement is similar in 
assembly concept to the drevice of FIG. 5, the difference residing in the 
fact that the FIG. 5 device is a spray nozzle whereas the FIG. 6 device is 
a fluidic element adapted to be connected via tubes 14, 66 to a fluid 
system. 
Rather than surrounding the body member and cover plate with injected 
plastic in a mold, or injecting plastic into a gap in a permanent housing 
to urge the oscillator surface into compressed abutment with a sealing 
surface, the concept of the present invention may be employed to flow 
injected plastic through suitably provided holes in the body member and 
cover plate to provide a rivet-like joining of the two members. Such an 
embodiment is illustrated in FIGS. 7-10. A fluidic oscillator 70 is 
defined in a surface 71 of a body member 72. The oscillator 70 has an 
outlet opening 74 adapted to issue a sweeping third spray into the 
surrounding ambient environment. A cover plate 73 is integrally joined to 
body member 72 by means of a thin bridging member 75. An inlet stem 76 
depends from body member 72 and includes a fluid supply bore 77 defined 
longitudinally therethrough and through the body member to communicate 
with oscillator 70. The entire unit as thus far described may be 
fabricated as one piece in a molding process. For final assembly the 
bridging member 75 is folded so that cover plate 73 is placed flush on 
surface 71 of body member 72. Suitable holes 78 are defined through cover 
plate 73 at spaced locations along the cover plate. Holes 78 are wider at 
the side of the cover plate remote from body member 72, forming a 
generally funnel shaped hole configuration. Similar holes 79 are provided 
through body member 73 at locations which permit holes 78 and 79 to be 
aligned when the cover plate is folded over onto the body member. In order 
to facilitate alignment of the holes, collars 80 are provided to project 
from surface 71 concentrically about each hole 79 and are of such size and 
configuration as to be received without significant slack within holes 78 
when the cover plate is properly aligned on surface 71. Collars 80 also 
serve during injection to prevent the flowing plastic from flowing along 
the mating surfaces between members 72 and 73. The holes 78 are wider at 
the side of body member 72 remote from cover plate 73. 
Cover plate 73 on the surface remote from body member 72, has recesses on 
channels 81 defined therein which interconnect the holes 78 as they 
communicate with that surface. These channels 81 permit injected molten 
plastic to flow into holes 78 to holes 79. To this end, the abutting cover 
plate 73 and body member 72 are clamped between two mold halves 82, 83 
(FIGS. 9 and 10) which include an injection inlet opening 84. When plastic 
is injected into opening 84 it flows through and fills channels 81 and 
holes 78 and 79. Upon solidifying the plastic in the holes applies a 
shrinkage stress compression force which holds the body member and cover 
plate together. In this regard it is noted that the wide-to-narrow 
configuration of holes 78, 79 permits the solidified plastic therein to 
act like a rivet in joining the two elements together. Aiding this 
function is the expansion of collar 80 against the walls of hole 78 by the 
solidifying plastic. The final assembly (as seen in FIG. 8) is a compact 
one piece unit sealed by a simple plastic injection step. 
As briefly mentioned above, the parts to be assembled are preferably made 
of a thermo-set plastic such as a phenolic. The injected plastic material 
could then be any other injection moldable plastic. Alternatively, 
polypropylene or certain acetal plastics can be used for the assembled 
members and the same material or ABS (having a slightly lower melting 
temperature) can be injected as the sealer. In this regard it should be 
noted that the injected material comprises far less mass than the 
assembled parts so that "cold-shot" injection may be used wherein the 
injected material cools before the base materials melt. 
While I have described and illustrated one specific embodiment of my 
invention, it will be clear that variations of the details of construction 
which are specifically illustrated and described may be resorted to 
without departing from the true spirit and scope of the invention as 
defined in the appended claims.