Magnetically opened diaphragm design with camera shutter and expansion tube application

Bengtson, R. D.

Oertel, G. K.

English

NASA Technical Reports Server

REPLY TO 
A T T N O F  GP 
NATIONAL AERONAUTICS A N D  SPACE ADM INlSTRATlON 
WASHINGTON, D.C. 20546 
March 27,  1971 
TO : USI/Scientific & Technical Information Division 
FROM r GP/Office of Assistant General 
Attention: Miss Winnie M. Morgan 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U.S. Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code U S I  memorandum on this subject, dated June 8 ,  1970, 
the attached NASA-owned U.S. patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U.S. Patent No, : 3,361,045 
Corporate Source : Lanqley Research Center 
Supplementary 
Corporate Source 
NASA Patent Case No.: XLA-03660 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710011585 2020-03-17T02:55:09+00:00Z
.o 
FAST-OPENING DIAPHRAGM 
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trigger pulse is applied to the spark gap switch causing 
it to fire. The resulting surge of current through the coil 
creates n magnetic field which applies a sufficient mag- 
netic pressure to the diaphragm to burst it. 
Other objects and advantages of this invention will fur- 
5 ther become apparent hereinafter and in the drawings, 
in which: 
FIG. 1 is a cross-sectional view of the physical relation 
of the coil to the diaphragm and the path that is blocked 
by the diaphragm; 
FIG. 2 is a schematic drawing of the electrical circuitry 
used in this invention; 
FIG. 3 is a schematic drawing of the use of this inven- 
tion in an expansion tube; and 
FIG. 4 is a schematic drawing of the use of this in- 
In describing the preferred embodiment of the inven- 
. 
The invention described herein may be manufactured 
and used by or for the Government of the United States 10 
of America for governmental purposes without the pay- 
inent of any royalties thereon or therefor. 
The invention relates generally to a fast-opening di- 
aphragm and more specifically concerns a diaphragm 
that is opened by the sudden application of a large mag- l5 vention as an optical shutter. 
netic field to it. 
In expansion tubes and in numerous optical applica- 
tions, it is desirable to have jitter-free, fast-opening, large 
diaphragms to act as gas valves or as high speed shut- 
ters. Previously, in expansion tube applications, a sudden 
rise in gas pressure caused by a shock wave was used to  
burst diaphragms and in optical applications either me- 
chanically operated shutters or Kerr cells were used. 
The use of gas pressure to rupture diaphragms, and to 
remove the ruptured diaphragms from the flow regions " 
causes loss of energy which results in a very inefficient 
operation of the expansion tube. As for the optical shut- 
ters heretofore available, the mechanical devices are quite 
slow and have considerable jitter. With this jitter, the 
shutters cannot be opened at a predetermined time with 
the accuracy needed for many modern applications such 
as magnetic compression experiments and other extremely 
bright transient events. The Kerr cells open quickly but 
they have a low transmission, a poor closed-open trans- 
mission ratio, and a small aperture (maximum of one-to- 45 
two inches wide}. 
I t  is therefore an object of this invention to provide 
a jitter-free, fast-opening diaphragm. 
Another object of this invention is to provide a jitter- 40 
free, fast-opening diaphragm suitable for use in expan- 
sion tube applications. 
It is a further object of this invention lo provide a 
jitter-free, fast-opening, diaphragm suitable for use as enclosure BI by any suitable means such as bolts to hold 
an optical shutter. 5 in place. Since there will 
Still another object of this invention is to provide an 45 be large stresses on diaphragm 15, it is necessary that it 
opening diaphragm that has a large aperture. be securely clamped between support piece 
A still further object of this invention is to provide an closure 1 to prevent tearing of the diaphragm. The 
opening diaphragm that has a good closed-open trans- thickness of the coil 63 must be much greater than the 
mission ratio. electromagnetic skin depth, and the thickness of the 
Yet another object of this invention is to provide a 50 diaphragm 65 should be equal to or larger than the 
diaphragm that can be opened at a predetermined lime electromagnetic skin depth. 
Referring now to FIG. 2, the coil 3 is shown connected with the accuracy needed for modem applications. 
'Yet another object of this invention is to provide an into an electrical circuit in series with a spark gap switch 
opening diaphragm that has a high transmission for all and a bank of capacitors 8. For efficient operation, 
wavelengths. e bulk of the system inductance in the circuit in FIG. 2 
In accomplishing these and other objects the present should be in the single tum coil 13. The bank of capaci- 
invention consists essentially of an electrically conductive tors 8 has a large capacitance and is charged by any 
thin diaphragm located in the path of the flowing gas suitable means such as a generator 
when used in expansion tube operations and in the optical which is a well known type of switch is  triggered to its 
path of the camera when used as an opening shutter. '* nductive state or to its nonconductive state by a suitable 
When used as a shutter, a closing shutter must also be trigger circuit . It is only necessary that trigger circuit 
provided. A coil is located around the path close to the 2@ produce pulses that have amplitudes of approximately 
diaphragm with an insulator between the diaphragm and 20 kv. and rise times of approximately 10 billion volts 
coil. The coil is connected in an electrical circuit in series per second. 
with a spark gap switch and a bank of capacitors. The " In oper on, the bank of capacitors 
bank of capacitors is charged by a generator and then a generator . Then a pulse from trigger 
tion illustrated in the drawing 
be resorted to for the sake of 
intended to be limited to the 
and it is to be understood that 
all technical equivalents which operate in a similar man- 
ner to accomplish a similar purpose. 
Turning now to the specific embodiment of the inven- 
selected for illustration in the drawings, the number 
1 designates generally an enclosure of a pas- 
through which the gas of an expansion t 
the light to a camera is to pass. Enclosur is t 
is made from 
nolic. Enclosu 
spark gap switch 1'1 to its conductive state causing the 
bank of capacitors to discharge through the single turn 
3. The resulting magnetic field produced by coil 
13 cannot penetrate diaphragm 15 to any large extent be- 
cause the thickness of the diaphragm 15 is of the same 
order as the electromagnetic skin depth. This high mag- 
netic field produces a large magnetic pressure which 
pushes the diaphragm away from the coil thereby stressing 
it until it ruptures. 
As was mentioned earlier, the fast-opening diaphragm 
which constitutes this invention has at least two app!ica- 
tions: one as a gas valve in an expansion tube and the 
other as an optical shutter for a large aperture camcra. 
In FIG. 3 there is shown a schematic diagram as to  how 
this invention can be used as a gas valve in an expansion 
tube. An expansion tube 2 consists of three different 
compartments 22, 23, and 2 . Compartment 22 is a high 
pressure compartment which is supplied by a high pres- 
sure source 25 under the control of a valve 26. Low pres- 
sure compartment 23 is supplied by a low pressure source 
27 under the control of a valve 28. Compartment 24 is 
a vacuum which is created by the mearls of a vacuum 
pump 29 under the control of a valve 30. Compartments 
2 and 23 are separated by a diaphragm 38, and compart- 
are separated by the diaphragm 15 as 
shown in the FIGS. 1 and 2. In operation, initially com- 
partment 22 is at a high pressure, compartment 23 is at a 
low pressure and compartment 24 is a vacuum. Then by 
means not shown, diaphragm 31 is ruptured and the re- 
sulting high pressure in Compartment 22 creates a shock 
wave which passes through compartment 23. Immediately 
prior to this shock wave compartn:ent 23 reaching 
diaphragm 15, diaphragm is ruptured which allows 
the shock wave to pass into the vacuum compartment 2 
unobstructed. Previously, diaphragm 
the shock wave that passes through compartment 23. This 
resulted in a loss of energy which caused an inefIicicnt 
operation. With the present invention, the loss of energy 
of the shock wave has been eliminated. 
In FIG. 4 there is shown a schematic diagram of a 
camera which utilizes this invention. To the left of a lens 
that is to be photographed. 
stitutes this invention is lo- 
the camera. Also a closing 
3'1 are located in tile camera 
path. The image of the photographed object appears on 
the strip of film 38. To photograph the object, the dia- 
5 is ruptured thereby allowing light to pass 
through the initially opened optical shutter 36 and along 
the optical path of the camera to film strip 38. Then, 
closing optical shutter 36 is closed a predetermined length 
of time after diaphragm 85 is ruptured. Fast, electroniag- 
netic, jitter-free closing optical shutters are commercially 
available and will therefore not be disclosed in detail in 
this application. 
The advantages of this invention as a gas valve in ex- 
pansion tubes are that it provides a fast-opening gas valve 
that is jitter-free and that reduces energy losses. The ad- 
vantages of this invention as an optical shutter are that 
it provides a fast-opening, jitter-free shutter that can be 
initiated by an electrical pulse; that can have a very widc 
aperture; that is useful in a vacuum as well as air or any 
gas; that is useful for wavelengths down to the soft X- 
ray region; and that has the best possible closed-open 
transmission ratio. 
It is to be understood that the form of the invention 
herewith shown and described is to be taken as a preferred 
embodiment. Various changes may be made in the shape, 
size, and arrangement of parts. For example, equivalent 
elements may be substituted for those illustrated and de- 
scribed herein, parts may be reversed, and certain features 
of the invention may be utilized independently of the u 'e  
of other features, all without departing from the spirit 
or scope of the invention as defined in the follov.inl: 
claim.?. 
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60 
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What is claimed as new and desired to be secured by 
Letters Patcnt of the United States is: . A fast-opening diaphragm for blocking the transmis- 
sion of a substance at a point along its path until a pre- 
determined time and then offering negligible resistance 
to the transmission of said substance at said point com- 
priaing: a thin electrically conductive diaphragm located 
to block the transmission of said substance at said point; 
means fixing said diaphragm against rotation relative to 
said path about any axis lying in the plane of the dia- 
phragm; a charged bank of capacitors; a coil around said 
path close to said diaphragm and electrically insulated 
therefrom; a normally opened switch connected in series 
with said coil and said charged bank of capacitors; and 
means for closing said switch at said predetermined time 
whereby said bank of capacitors discharge through said 
coil creating a magnetic force that ruptures said dia- 
phragm thereby allowing said substance to be transmitted 
unimpeded past said point. . A fast-opening diaphragm in accordance with claim 
wherein the thickness of said coil is many times the 
skin depth and the thickness of the diaphragm is approxi- 
mately equal to or larger than the skin depth. 
3. A fast-opening diaphragm in accordance with claim 
1 wherein said switch is a spark gap switch. 
4. A fast-opening diaphragm in accordance with claim 
wherein said means for closing said switch includes a 
trigger circuit that applies a triggering pulse to  said 
switch at said predetermined time to close the switch. 
5. A fast-opening diaphragm for blocking the path of 
a substance until some fixed time and then for unblocking 
said path comprising: a thin electrically conductive 
diaphragm blocking said path; a coil around said path 
close to said diaphragm; a large supply of electrical en- 
ergy; and means for connccting said supply of electrical 
energy to said coil at said fixed time whereby the result- 
ing current through said coil creates a magnetic field; 
and means positioning said diaphragm in such a man- 
ner as to produce rupture of said diaphragm by said mag- 
netic field. 
6. A fast-opening diaphragm in accordance with claim 
5 wherein said coil is a single turn coil whose thickness 
is several times the skin depth. 
7. A fast-opening diaphragm in accordance with claim 
5 wherein said means for connecting said supply of elec- 
trical energy to said coil includes a normally opened 
spark gap switch that is closed by a pulse from a trigger 
circuit at said fixed time. 
. An opening camera shutter comprising: a thin.elec- 
trically conductive diaphragm blocking the optical path 
of said camera; a coil around said optical path close to 
said diaphragm and electrically insulated therefrom; a 
large charge of electrical energy; and means for connect- 
ing said large charge of electrical energy to said coil 
whereby the resulting current through said coil creates a 
magnetic field; and means positioning said diaphragm 
in such a manner as to produce rupture of said diaphragm 
by said magnetic field thereby unblocking said optical 
An opening camera shutter in accordance with claim 
8 wherein said large charge of electrical energy is a 
charged bank of capacitors. 
10. A means for blocking the flow of a gas in an ex- 
p:.ri\ion tube until a fixed time and then offering negligi- 
ble resktance to the flow of the gas comprising: an 
electrically conductive diaphragm blocking the flow cf 
gas in said expansion tube; a coil around said expansion 
tube close to said diaphragm and electrically insulated 
therefrom; a bank of charged capacitors; and means for 
connecting said bank of charged capacitors to said coil 
at '.aid fixeJ time whereby the resulting current through 
haid coil create5 a maznetx f d d ;  and mean? poiitioiiing 
s;i:d diaphragm jn \itch a manner as to produce rupture 
of said diaphragm by said niiignctic field. 
1. A fast opening shutte for controlling communica- said path in response t 
in said coil. 
he prescnce of currcnt flow 
tion bctween two points on a path comprising: 
shutter means located on said path; 
a coi1 around said path; 
a supply of electrical energy; 
switching means to controllably connekt said electrical 3,185,063 5/1965 Ford _ _ _ _ _ _ _ _ _ _ _ _  350-269 X 
energy source to said coil to produce an electrical 3,191,516 6/1965 Corcoran _ _ _ _ _ _ _ _ _  35Q-269 X 
ebrences Cite 
UNITED STATES PATENTS 
current therein; and 
that said shutter means is completely removed from 10 
means positioning said shutter means in such a manner JOHN M. HORAN, Prinznry Exumincr. 


Fast opening diaphragm Patent

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