Burst diaphragm flow initiator for installation in short duration wind tunnel

Davis, J. W.

Hill, O. E.

English

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
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U. S. Patent  No. 
Government o r  
Corporate Employee z Government 
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Source ( i f  appl icable)  : N. A. 
NASA Patent  Case No. 
NOTE - I f  t h i s  pa ten t  covers an invention made by a corporate 
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(CATEGORY) 
_d L. _- - -- 
https://ntrs.nasa.gov/search.jsp?R=19710008125 2020-03-17T02:37:30+00:00Z
S p t .  30, 1969 J. W. DAVIS ETAL 3,469,734 
BURST DIAPHRAGM FLOW INITIATOI? 
F i l e d  Dec. 28, 1967 7 C" ,,l,8:r; t ,--,';!;er;'- 1 
F I G ,  5 
JOHN +i DDVlS 
OLEN E HILL 
INVENTOR (51 
hn t ,  30, 1969 J. W. DAVIS  ETAL 3,469,734 
BURST D I A P H R A G M  PLOW I N I T I A T O R  
Fi led Dec. 28, 1967 3 Sheet--.':: .::-c 2 
W q d  H.RLr"ao, 
A T T O  E Y S  
&pt, 30, 1969 J, W. DAVIS ETAL 3,469?734 
BLJRST D I A P H R A G M  PLOW I N I T I A T O R  
Fi led Dec. 28, 1967 3 Sheets-Sheet 3 
FIG. 6 
. 39 
63' GLEN E. H I L L  
IN VENTOR.I.51 
Fie, 4 BY 
bJ 
United States Patent Ofi 3,469,734 ce Patented Sept. 30, 1969 
surized gas forces the light petals to the full open posi- 
3,469,734 tion in a period of a few milliseconds. 
BURST DIAPHRAGM FLOW INITIATOR Accordingly, it is a general object of the present inven- 
John W. Davis and Oleu E. Hill, HuntsvilIe, AIa., as- tion t~ provide an improved ultrarapid flow initiator. 
signors to the United Stales of An~erica as represented 
by the AdIuinistrator of the Aerol,autics and 5 A more specific object of the invention is to provide a 
Space Administration burst diaphragm flow initiator that is capable of initiating 
Filed Dec. 28, 1967, Ser. No. 694,340 the flow of gas from a relatively high pressure reservoir to 
Hut. el. B65d 25/00 a relatively low pressure receiver in a period of a few 
U.S. 61. 220---89 5 Claims milliseconds. 
10 Another object of the invention is to provide a flow 
initiator for use in short duration wind tunnels that has 
ABSTRACT OF THE DISCLOSURE ultrarapid opening response, is economical to use and does 
A flow initiator for installation in a short duration wind not shed undesirable particles during the flow initiating 
tunnel or other facility for instantaneously starting the Process, while being simple to fabricate and control. 
flow of gas from a high pressure reservoir into a lower 15 These and other objects and advantages of the inven- 
pressure receiver. A nlultiple element grid is disposed in a tion will become apparent upon reference to the following 
tube section with the grid elements extendine transverselv attendant and drawing. 
of the tube and supporting a Mylar d i a p h r a b  that closes 
the tube separating the high pressure gas from the lower ,, BRIEF DESCRIPTION OF THE DRAWING 
pressure gas. An air-actuated multibladed cutter is housed '" FIGURE 1 is an elevational view of a portion of a wind 
within the supporting grid, and shears the diaphragm into tunnel facility which portion incorporates a burst dia- 
several distinct petals. The higher pressure gas forces the phragm ultrarapid flow initiator; 
petals of the diaphragm to the full open position in a few FIGURE 2 is an end perspective view of a flow initiator 
n~illiseconds. such as incorporated in FIGURE 1 showing the cutting 
25 knife of the initiator in the extended position and the 
The invention described herein was made by employees burst diaphragm 
of the United States Government and may be nlanufac- FIGURE 3 is an end perspective view similar to  that 
tured and used by or for the Government for governmen- of FIGURE 2 but showing the sheared burst diaphragm 
tal purposes without the payment of any royalties thereon 30 s"bse9uent and the cutting knife re- 
or therefor. tracted; 
FIGURE 4 is a vertical cross-sectional view taken 
BACICGROUND O F  THE INVENTION along line 4--4 of FIGURE 3 with the burst diaphragm 
This invention relates generally to flow initiators and 
more particularly to a device for effecting ultrarapid flow 
initiation of gas from a high pressure reservoir to a lower 
pressure receiver. 
In connection with certain scientific and engineering ac- 
tivities, it is often desirable or necessary to produce an 
extremely rapid start of a flow of gas through a tube or 
conduit. One such field of work is that involving wind 
tunnel technology which constitutes a very important 
aspect of the aelospace field in the many types of testing 
performed by utilizing wind tunnels. In wind tunnel facil- 
ities designed for short duration tests it is essential that a 45 
means be provided for initiating the flow of gas from a 
high pressure trtbe into a lower pressure receiver within 
a few milliseconds. 
Prior devices for producing initiation of gas flow in 
wind tunnels include quick opening valves, pyrotechnic 50 
devices and metal diaphragms designed to burst under gas 
pressure. The meial diaphragm initiators and the quick 
opening valves do not respond as rapidly as desired in 
short duration wind tunnel tests and the metal diaphragms 
shed undesirable metal ~rarticfes upon bursting. Moreover, 56 
the quick opening valves are very expensive and not very 
practical in association with large diameter tubes and 
large pi.essures. The pyrotechnic initiators could probably 
provide file necessary quick response but are relatively 
expensive and hazartlous and also shed undesirable par- GO 
ticies iiiii'lng the horsiing process. 
G,U>:fP/IAIIk' OF THE INVENTION 
The i1;vtnliorr coi~iprises a lnuirlpie element grid sup- 65 
port disposed wiihirr a gas candrrcting tube with the grid 
support housing a reciprocating cutter. A diaphragm made 
of a plastic, such as h.lylar, is srrpported on the grid ele- 
ments normai io the gas flow with the diaphragm being 
stressed against the grid stlpport elements. When gas flow 70 
initiation is desired the cutter is actuated and shears the 
diaphragm into a plurality of distinct petals and the pres- 
removed; 
FIGURE 5 is a view, partially in cross-section, of a 
flow initiator wherein the burst diaphragm is mounted 
in a special clamping ring; 
FIGURE 6 is an end elevational view illustrating a 
modified flow initiator with the burst diaphragm removed, 
the initiator being particularly adapted for large diameter 
tubes. 
DESCRIPTION O F  THE PREFERRED 
EMBODIMENTS 
Referring to FIGURE 1, therein is shown a portion 
of a wind tunnel 11 that includes a supply tube 13 joined 
to one end of a nozzle 15 the other end of which is con- 
nected to a test section 17. Arranged between and inter- 
connecting the test section 17 and a receiver tube 21 is an 
ultrarapid burst diaphragm flow initiator 19. In operation 
of the wind tunnel 11 a model or specimen to be tested 
is arranged in the test section 17 and pressurized gas is 
introduced into the components to the left of the flow 
initiator 19 which means that pressurized gas is in the 
test section 17, nozzle 15 and supply tube 13. 
A diaphragm 25 (FIGURES 3 and 5)  is clamped be- 
tween the meeting ends of the test section 17 and the flow 
initiator 19 and seals the passage of gas from the high 
pressure zone to the low pressure zone which includes the 
receiver tube 21. At the instant when it is desired to 
initiate gas flow within the wind tunnel the diaphragm 25 
is bursted in a rnanner to be described subsequently. The 
diaphragnl 25 is made of a plastic such as Mylar and 
comprises muliiple layers with the number of layers de- 
pending on: the amount of pressure a particular diaphragni 
is to be subjected to prior to flow initiation. 
Referring to FIGURES 2, 3 and 4, the flow initiator 19 
comprises a tube or chamber section 27that  contains a 
grid support unit 29 having a plurality of grid elements 
31 radiating from a center cylinder 33. The grid elements 
31 are joined as by welding to the inside wall of the cham- 
ber section 27. 
3 4 
Each of the grid elements 3% has an end slot 35 that re- grid elements 85. Each of the grid elernenis 85 has an entl 
ceives a blade 37 of a reciprocating cqtter 39. The blades slot 87 therein illat receives ;I blade 89 of a cutter $1. 
37 are melded to a stem por-tion 41 that is integral with The end slots 87 extend less than haif tile n.,.diai Jir'len- 
a plunger 43 (FIGURE 4) .  The plunger 43 i s  arranged ' sion of ihe grid elements 85 aiitl (ht;s Liic blades 89, \,,hen 
axially within thc cylinder 33, and the cylinder has a re- extended, only shear the central portion of the diaphragn-r. 
duced diameter end portion 44 that acts as a guide for Tests kave shown, however, that when the diap111-agm is 
reciprocating action of the plunger 43. The end of the stressed against the grid elements in the manner pre- 
plunger opposite the blades 37 has an annular flange 49 viously described and sheared into distinct petals in the 
that provides as top for  the plunger when the plunger central region, the force of the pressilrized gas will cause 
shifts to extend the cutter 39. 10 the diaphragm to  rip along the lines establishzd by the 
Connected to the end of the cylinder 33 by bolts 51 is cuts made in the center of the diaphrngrn thus forcing 
an air cylinder 53 that includes a piston having a portion these petals to the full open position. 
55 fitted in an  opening 57 of the plunger 43, being secured We claim: 
by a dowel pin 59. The piston of the air cylinder 53 is 1. A burst diaphragm flow initiator comprising: 
actuated by a source of air pressure (not shown) sup- 15 ( a )  a chamber having an  entrance end and an exit 
plied through a tube 61 that extends through an end end; 
flange 63. ( b )  a burst diaphragm supporting unit in said cham- 
The entrance end of the initiator that receives the dia- ber having a supportin gsurface intermediate the 
phragm 25 has a flange 65 and a raised annular seat 67 circumferential wall of said chamber and adjacent 
over which the diaphragm 25 is arranged. The edges of 20 said entrance end of said chamber for a burst dia- 
the grid elements 31 are recessed a short distance from phragm to bear upon; 
the surface of the annular seat 67 so that when pressure is ( c )  a slot in said supporting surface opening toward 
applied against the diaphragm 25 this pressure will de- said entrance end of said chamber; 
form the diaphragm and stress it against the edge sur- ( d )  cutting means including a blade adapted for pass- 
faces of the grid elements 31. This causes the diaphragm 25 ing transversely through the plane defined by said 
to be in a taut or stretched condition when it is sheared supporting surface; 
assuring a very clean cut through the diaphragm and a ( e )  said blade being aligned with said slot in said 
quick separation of the petals formed by the cutter supporting surface; 
blades. ( f )  a clamp ring arranged contiguous and in align- 
When the flow initiator 19 is installed in a conduit sys- 30 ment with said entrance end of said chamber; 
tem such as the wind tunnel 11 (FIGURE 1) with the (g)  said clamp ring having a burst diaphragm mounted 
diaphragm overlying the cutting end of the initiator and therein; 
being pressed against the edge surfaces of the grid ele- ( h )  said diaphragm closing said entrance end of said 
ments 31 by the pressurized gas, air is applied to the air chamber. 
cylinder 53 at the instant flow initiation is desired. The 35 2. A burst diaphragm flow initiator con~prising: 
air cylinder piston 55 moves the plunger 43 and thus the ( a )  a chamber having an entrance end and an exit 
blades 37 to the extended position shoaln in FIGURE 2 end; 
thus shearing the diaphragm 25 into four distinct petals. (b )  a burst diaphragm supporting unit in said cham- 
The pressurized gas instantly forces the light Mylar petals ber having a supporting surface adjacent said en- 
to the full open position commencing the flow of gas in 40 trance end of said chamber; 
a period of a few milliseconds. ( c )  said supporting unit comprising a plurality of sup- 
FIGURE 5 shows a flow initiator 71 that is similar porting elements radiating from the longitudinal axis 
to the flow initiator 19, the difference being that the of said chamber toward said chamber wall; 
initiator 71 does not have a raised annular seat, such as (d )  each of said elements having a slot therein open- 
67, for receiving the burst diaphragm 25. Instead, the dia- 45 ing toward said entrance end of said chamber; 
phragm is mounted in a clamp ring assembly 73 adapted (e)  cutting means including a blade aligned with each 
to be installed between an end flange of the initiator 71 of said slots with each of said blades being adapted 
and the adjacent tube section 17. The clamp ring assem- for passing transversely through the plane defined 
bly 73 comprises an outer ring 75 counterbored at  77 for by said supporting surface. 
receiving an inner ring 79. The burst diaphragm 25 is 50 3. The invention as defined in claim 2 wherein said 
clamped between the inner and outer rings by screws 81 supporting unit further comprises a cylinder concentric 
closely and equally spaced around the clainp ring as- with said axis of said chamber, said cylinder containing 
sembly 73. a plunger, said plunger being connected to  each of said 
The clamp ring 73 permits a quick replacement of the blades. 
burst diaphragm from one test t o  the next where a series 55 4. The invention as defined in claim 3 including an air 
of tests are being made. Also the burst diaphragm may cylinder aligned with said plunger, said air cylinder hav- 
be more firmly and uniformly clamped in the clanlp ring ing a piston therein, said piston being connected io said 
73 than is possible with the raised annular seat 67 be- pltlnger. 
cause a proper number and size of clamping screws are 5. The invention as defined in claim 2 wherein said 
used rather than relying on the limited number of large slots in said extend less than half the radial di- bolts extending between the tube end flanges. mension of said elements. 
FIGURE 6 shows a modified form of the Bow initiator 
oarticular.lv adapted for large diameter tubes. The princi- References Cited 
a 1  diffetinces between the flow lnltiator ~lluslraied in 
FIGURE 6 and that previously described are that the UNITED ST4TES PATENTS 
?rid efen~ents are increased in number and are extended 3,101,733 8/f951 L o ~ d  - _ _ _ 117- 68 
12 radral length lo adequately ";upport the hiirst dra- 
pttracm over a l a g e r  area presented by a larger diameter RAPI-IAEL H SCHWAR PZ, i%rirnary PI i l i i i r x r  
tube. A tube 83 contains a grid support having eight 


Burst diaphragm flow initiator Patent

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