Observers are protected from flying debris resulting from a failure of a vacuum or pressure chamber viewing port following an implosion or explosion by an optically clear shatter resistant safety shield which spaced apart from the viewing port on the outer surface of the chamber

Shimansky, R. A.

Spencer, R. S.

English

NASA Technical Reports Server

National Aeronautics and
Space Administration
Washington, D.C.
20546
Reply to A'tn of: GP-4
TO: NST-44/Scientific and Technical Information Division
Attn: Shirley Peigare
FROM: GP-4/Office of Assistant General Counsel
for Patent Matters/Nancy L. Fonseca
SUBJECT.:: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP-4 and
Code NS.T-44, the attached NASA-owned U.S. Patewnt is being
forwarded, for abstracting and announcement in NASA STAR.
The following information, is provided: .
»
U.S. Pa.t:ent No. :
Government or
Corporate. Employee
Supplementary Corporate
Source (vi.f applicable)
NASA Pa.t.ent Case No.
NOTE - E£ this' patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
YES / / NO
Pursuant to. Section 305(a) of the National Aeronautics and Space
Act, the- name of the Administrator of NASA appears on the first
page of: t±re patent; however, the name of the actual inventor
(author)' appe-.ars at the heading of column • Ho. . 1 of the
Specification, following the words "...with respect to an
inventi.Q.n: of. . . "
'(NASA-Case-GSC-V2513-1) SAFETY SHIELD FOR
VACUUfl/PBESSUBE CHAMBER VIEWING POET Patent
(NASA) 4 p CSCL 13L
00/31
Oiiclas
16549
https://ntrs.nasa.gov/search.jsp?R=19810010816 2020-03-21T09:26:16+00:00Z
United States Patent m
Shimansky et al.
[54]
[75]
SAFETY SHIELD FOR VACUUM/PRESSURE
CHAMBER VIEWING PORT
Inventors: Richard A. Shimansky, Marlow
Heights; Rodney S. Spencer, College
Park hoth of MH
1,521,393
1,686,942
2,736,231
3,369,836
3,393,485
4.006.973
12/1924
10/1928
2/1956
2/1968
7/1968
2/1977
[ii] 4,245,566
[45] Jan. 20, 1981
Ross
Thielker
Wright
Zanotti et al
109/21.5
. . 109/21.5
350/310
109/49 5 X
109/58.5 X
350/310
[73] Assignee: The United States of America as
represented by the United States
National Aeronautics and Space
Administration, Washington, D.C.
[21] Appl. No.: 53,571
[22] Filed: Jun. 29, 1979
[51] Int. CU E06B 9/00
[52] U.S. Q 109/49.5; 49/171;
109/58.5; 220/82 R; 220/89 A
[58] Field of Search 109/21.5,49.5,58.5;
49/171; 220/82 R, 89 A, 89 B; 350/310
[56] References Cited
U.S. PATENT DOCUMENTS
1,407,975 2/1922 Wolfe et al 109/21.5
FOREIGN PATENT DOCUMENTS
839017 3/1939 France 350/310
1088131 3/1955 France 49/171
Primary Examiner—David H. Corbin
Attorney, Agent, or Firm—Robert D. Marchant; John R.
Manning; John O. Tresansky
[57] ABSTRACT
A safety shield for protecting observers from flying
debris resulting from a failure of a vacuum or pressure
chamber viewing port following an implosion or explo-
sion includes an optically clear shatter-resistant safety
shield member spaced apart from the viewing port on
the outer surface of the chamber.
6 Claims, 3 Drawing Figures
14
U.S. Patent Jan. 20, 1981 4,245,566
4,245,566
1 2
of glass placed between a pair of spaced panes made of
SAFETY SHIELD FOR VACUUM/PRESSURE polycarbonate material.
CHAMBER VIEWING PORT While the described prior art vacuum and pressure
chamber viewing ports do allow higher pressures to be
ORIGIN OF THE INVENTION 5 sustained due to their "dual-window" or reinforced
_ . . .. ., . , , structure over those obtainable from single windowThe invention described herein was made by employ-
 viewj ^ ibuj sti,, exjsts th« such wm.
ees of the U.S. Government, workmg at the Nat.onal
 dows can shatter fo ^ these of afe
Aeronaut.es and Space Administration, and may be
 cost]y to manufacture and can restrict the view through
manufactured and used by or for the Government for ,0 ,he port due tQ doub,e refraction of light through the
governmental purposes without the payment of any
 dua, windows or interference by the reinforcing grid,
royalties thereon or therefor.
 It is therefore an object of the invention to provide a
BACKGROUND OF THE INVENTION safety shield for a vacuum or pressure chamber viewing
port which affords a high degree of protection from
The invention relates to the field of safety shields and
 15 flyjng fragments or debris resulting from accidental
more particularly to an optically clear safety shield to shattering of the port.
be positioned over a vacuum or pressure equipment jt js a further object to provide a safety shield for a
viewing port. vacuum or pressure chamber viewing port which does
Vacuum and high pressure chambers are designed not restrict the view through the port,
and constructed to handle large forces due to the pres- 20 It is another object to provide a safety shield which is
sure differential between the interior of the vacuum or easily manufactured and attached to a vacuum or pres-
pressure chamber and the exterior of the chamber (at- sure chamber viewing port,
mospheric pressure). It is common practice to include CITMMAB v OF THP INVPMTTON
one or more viewing ports in the chamber to allow an SUMMARY OF THE INVENTION
observer to watch an experiment being performed 25 These and other objects are achieved by the present
within the chamber or to enable a photographic record invention wherein there is provided a safety shield for
of the experiment to be made. These viewing ports are protecting observers from flying fragments or debris
normally formed integrally to and are airtight with the resulting from a failure of a vacuum or pressure cham-
surface of the chamber, the window itself being formed ber viewing port including a safety shield member,
from one or more thicknesses of an optically clear mate- 30 formed from a plate of optically clear shatter-resistant
rial, such as glass. material, and hardware for mounting the shield member
In a vacuum chamber, the interior of the chamber is to the viewing port while providing an air gap between
held at a pressure considerably lower than atmospheric the shield member and the viewing port. The shield
pressure. The forces acting on the walls and viewing member is not subject to the cyclic stresses imposed on,
ports of the chamber, therefore, will be directed in- 35 the v'ewing port window because of the air gap be-
wardly toward the center of the chamber. In a high- tween the shield and v™8 Port- Inu the event thf fhe
pressure chamber, conversely, the interior of the chanv ?lewln8 Port accidental y fails or shatters, any flying
her is held at a pressure higher than atmospheric pres- fragments or debris resultmg from an implosion or ex-
sure. Thus, the forces acting on the walls and viewing &°slon Wl11 be deflected b* the shleld awav from an
ports of the chamber will be outwardly directed. ° g^t^M
 {he safet shidd member is formed hav.
In many vacuum and pressure chamber systems the . , ._, .. . . ., . . . , . . , .
, , . i j • j- 11 u me a shape identical to the viewing port and is at least
chamber is cycled periodically to vary the vacuum or Jj £ ^
 vie The ^ ^.^ [& formed
pressure applied to the mtenor of the chamber. After a
 from *plexi , Lucife) or other shatter-resistant opti-
number of vacuum or pressure cycles, the sealing ar-
 4J ca,iy clear materials. The safety shie,d is mounted to the
rangement of the viewing ports can become weakened
 co)lar Qf a conventiona, vacuum or sure chamber
or the window itself can become weakened due to the
 viewjng by three Qr more threaded rods Locknut
cyclic stresses. If the seal or window becomes suffi-
 rs afe used {o attach the safc,y shje]d ,o {he
ciently weakened the port will crack and shatter and,
 threaded rods. The threaded rod and locknut assembly
depending upon whether the air pressure is lower or
 50 a,,ows the air gap between the viewing port and safety
higher than atmospheric within the chamber, implode
 shield to be readily adjusted. Advantageously, the view
or explode with considerable force. In either case, frag-
 into the vacuum or pressure chamber is not obstructed
tnents of the shattered port will be propelled at high
 by the optically clear safety shield,
velocities presenting considerable danger to personnel
in proximity to the chamber. In addition, any equipment
 55 BRIEF DESCRIPTION OF THE DRAWING
disposed near the shattered viewing port will likely be These and other objects, features and advantages of
damaged. the present invention are presented ii the following
One prior art approach toward reducing the risk of a detailed description of the preferred emood.ment and
vacuum or pressure chamber viewing port or the like illustrated in the accompanying drawing figures
shattering under pressure is to fabricate a viewing port 60 wherein:
window of optically clear material which is supported FIG. 1 is a perspective view of a safety shield con-
by a metal grid to relieve stress on the window. In structed in accordance with the principles of the present
another prior art approach, an airtight viewing port is invention shown attached to a viewing port of a vac-
formed with two spaced-apart plates, one being flat and uum or pressure vessel;
the other being curved. Other prior art approaches 65 FIG. 2 is a front view of the safety shield shown in
include providing a gas venting arrangement to prevent FIG. 1;
shattering of a dual window viewing port, and forming FIG. 3 is a right side sectional view of the safety
an impact resistant window assembly including a sheet shield and viewing port taken along lines 3-3 of FIG. 2.
4,245,566
DESCRIPTION OF THE PREFERRED
EMBODIMENT
In FIG. 1, there is shown a chamber, generally desig-
nated by numeral 1, which can be a vacuum chamber or 5
a high-pressure chamber, having a view port assembly,
generally designated by numeral 3. A safety shield
member 5 is attached to the view port by threaded rods
7 which support the shield member in a spaced apart
relationship from view port assembly 3.
 10
As illustrated in FIGS. 2 and 3, view port assembly 3
includes a flange 9 formed integrally with vacuum/-
pressure vessel 1 and a concentric collar 11 attached to
flange 9 by a plurality of threaded rods 7, the rods being
disposed through a number of mating openings 10, 12
formed respectively through flange 9 and collar 11. An '5
optical window 13 is disposed between flange 9 and
collar 11 along an annular recess 15 which is formed
along facing portions of flange 9 and collar 11, respec-
tively. One or more O-rings 17 can be disposed along
recess 15 to perfect the seal between window 13 and 20
members 9,11. Collar 11 is compressed against window
13 by nuts 19 and 21 to seal the windows against the
surface of flange 9 and the O-ring 17 to form an airtight
viewing port assembly.
Safety shield 5, which has a shape similar to that of 25
the viewing port assembly (i.e., the shield is circular for
a circular viewing port), is slightly larger than viewing
window 13 so that a number of openings 14 can be
formed about the periphery of shield 5 to receive outer
portions of threaded rods 7. A bevel 29 can be formed ,„
along edge 27 of shield 5 to provide a smooth edge and
prevent accidental chipping of the shield material.
Shield 5 is fastened to threaded rods 7 by a plurality of
inner and outer locknuts 23 and 25, respectively, which
secure the safety shield in a spaced apart relationship
with respect to view port assembly 3. Locknuts 23 and
25 allow ready adjustment of the air gap or spacing
between shield 5 and window 13. Of course, other
mounting and adjustment arrangements could be used,
depending on the size and configuration of the view
port to which the safety shield is to be installed. 4°
Safety shield 5 may be formed from a wide variety of
optically clear shatter-resistant materials. Materials
such as methyl methacrylate and methacrylate resins
(Lucite, Plexiglas, etc.) are of particular utility because
of their optical clarity, ease of machining, and resistance 45
to shattering. A i inch thick plate of Plexiglas spaced
one inch from a vacuum or pressure chamber viewing
port has been found to be virtually shatter-proof when
subjected to bombardment by explosive fragments from
the shattered view port window. Of course, other types 50
and thicknesses of shatter-resistant materials can be
used.
In a typical installation, flange 9 and collar 11 respec-
tively include six sealing bolts disposed in equi-spaced
openings 10 and 12 arranged about the circular view
 55
port. In order to mount the safety shield of the present
invention, three equi-spaced bolts are removed and
replaced by threaded rods 7. Locknuts 23 are threaded
on rods 7 at a position depending on the spacing desired
between shield 5 and window 13. Shield 5, having three
equi-spaced peripheral openings 14, is mounted onto the w
threaded rods. Locknuts 25 are then threaded onto the
outer portions of threaded rods 7 to secure the shield
and complete the assembly.
An important feature of the present invention is that
safety shield 5 is not subject to the stresses imposed on 65
view port window 13 when window 13 is under pres-
sure. After repeated pressure cycling of chamber 1,
window 13 may become weakened and fail. Often, such
a failure results in shattering of window 13 and a resul-
tant implosion or explosion of window fragments.
When chamber 1 is at a pressure substantially below
atmospheric, for example, the shattering of window 13
and resultant implosion of window fragments into
chamber 1 can result in fragments colliding with the
walls of chamber 1 and rebounding back out the shat-
tered view port assembly 3. High-speed flying frag-
ments and debris can pose a lethal or injurious situation
to personnel who are in proximity to window 13 when
it shatters.
Unlike prior art "double-pane" or mesh reinforced
airtight viewing windows for vacuum or pressure
chambers, in the present invention pressure stresses
placed on window 13 do not affect shield 5, because an
air gap is always maintained between safety shield 5 and
window 13. Thus, if window 13 shatters, shield 5 de-
flects flying fragments or debris of the shattered win-
dow from personnel or equipment near the view port.
In addition, some of the energy of the flying fragments
is spent in elastic collision with the safety shield; thus
slowing any deflected fragments. The optically clear
safety shield of the present invention allows an unob-
structed view of the interior of the vacuum or pressure
chamber and is easily fabricated and attached to con-
ventional vacuum or pressure apparatus. Adjustment of
the air gap between the view port and safety shield is
simple using the threaded rods and locknut spacing
hardware.
While the safety shield of the present invention has
been described in considerable detail, it is understood
that various changes and modifications may occur to
persons of ordinary skill in the art without departing
from the spirit and scope of the invention as defined in
the appended claims.
What is claimed is:
1. A safety shield for a vacuum/pressure chamber
viewing port, comprising:
an optically clear safety shield member;
a plurality of threaded rods extending through said
optically clear safety shield member and said vacu-
um/pressure chamber so that said optically clear
safety shield member is axially aligned with said
viewing port;
a first pair of nuts threaded on each of said threaded
rods, said nuts bearing against opposite sides of said
vacuum/pressure chamber for securing said
threaded rods to said vacuum/pressure chamber;
and
a second pair of nuts threaded on each of said
threaded rods, said second pair of nuts bearing
against opposite sides of said optically clear safety
shield member, and said second pair of nuts being
adjustable along said threaded rods to adjustably
space said optically clear safety shield member
from said viewing port.
2. The safety shield of claim 1 wherein said shield
member is formed from an optically clear, shatter-resist-
ant material and has a shape corresponding to the shape
of said viewing port.
3. The safety shield of claim 2 wherein said shield
member is formed from a methacrylate resin.
4. The safety shield of claim 1 wherein said shield
member is larger than said viewing port.
5. The safety shield of claim 3 wherein said shield
member is of sufficient thickness to contain said viewing
port explosion fragments.
6. The safety shield of claim 5 wherein said shield
member is formed from a plate having a thickness of at
least I inch.


Safety shield for vacuum/pressure chamber viewing port

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server