Expandable shelter system providing collective protection

A lightweight, free-standing, expandable shelter (10) providing protection against chemical and biological agents and against nuclear fallout. The shelter (10) has a frame comprising a series of U-shaped ribs (12) spaced and held parallel by a series of reinforcing members (16) connecting each adjacent pair of ribs (12) on each side of the shelter (10). A cover (11) made of flexible material which is resistant to chemical and biological agents is attached to the frame. An airtight floor (18) is attached to the cover material (11) so that the shelter (10) can be pressurized to a pressure of about one inch water gauge above ambient pressure, to prevent reverse air flow of contaminated air into the shelter (10). A blower (20) for pressurizing the shelter (10) and a filter (22) capable of filtering out chemical and biological agents are connected to the shelter (10). The shelter (10) incorporates an internal chamber (26) which serves as a protective air lock entrance and purge chamber and contains an indicator (30) showing when the air lock (26) has been purged and it is safe to enter main chamber (28) of the shelter (10). Air lock (26) is pressurized to one-half inch water gauge above ambient pressure to prevent air flow for air lock (26) into main chamber. The main chamber (28) is equipped with a pressure sensing device (52) and indicator lights (54, 56, 58) indicating either high, correct, or low pressure in the shelter (10) and an audible warning device (60) to warn of dangerously low pressure within the shelter (10).

TECHNICAL FIELD 
The present invention relates generally to portable shelters and more 
particularly to a metal frame, soft side, expandable shelter which is 
sturdy, self-contained, quickly erectable and strikable, and provides 
protection against chemical and biological agents and nuclear fallout. 
CROSS REFERENCE TO RELATED APPLICATIONS 
This application is related to U.S. patent application Ser. No. 611,851, 
filed May 18, 1984, which was a continuation-in-part of U.S. patent 
application Ser. No. 525,001, filed Aug. 19, 1983, which was a 
continuation-in-part of U.S. patent application Ser. No. 410,521, 
"Expandable Soft Side Shelter," filed Aug. 23, 1982, now abandoned. 
BACKGROUND OF THE INVENTION 
In the past, a wide variety of portable shelters have been used to include 
tents and similar structures, inflatable structures, geodesic domes, and 
various types of prefabricated structures. Tents have the advantage of 
being quick to erect, while pre-fabricated structures have the advantage 
of being sturdier, more permanent, and more capable of withstanding 
weather. The ideal portable shelter would be free-standing and quick and 
easy to erect, yet sturdy and capable of withstanding windy and stormy 
weather. Portable shelters, at least those used by the military services, 
would preferably have one further characteristic: they would provide 
protection not only against the weather, but also optionally provide 
protection against chemical and biological agents and nuclear fallout. 
None of the known prior art devices disclose a portable shelter having 
these ideal characteristics. 
U.S. Pat. No. 3,666,174 to Brylka at et discloses a blower apparatus for 
air supported structures. The Brylka device is a larger trailer which 
contains a blower and filters for a double walled air-supported structure. 
The Brylka device has the same disadvantages as all air-supported 
structures, that is, a blower must be operating and consuming power 
constantly to keep the shelter erect. In addition, the requirement for 
operating a gasoline engine or electric generator at all times reduces its 
usefulness for military units operating in forward areas in a combat 
situation. 
Another double wall shelter is disclosed in U.S. Pat. No. 2,649,101 to 
Suits. This shelter is also a pressure supported structure in that it uses 
a negative pressure to create rigid arches to support the structure. It 
consists of a double-wall shelter that is inflated only to create the 
desired shape, then the space between the walls, which has a blanket of 
insulating material, is evacuated to compress the insulating material and 
create a rigid arch. The inflating air can then be turned off and the 
structure will support itself as long as the arches remain under 
sufficient negative pressure. 
A third prior art patent, U.S. Pat. No. 3,660,951 to Cadwell, shows a 
double walled air-inflated shelter protecting against shock waves from 
nuclear explosion. A triple wall structure that has varying degrees of 
pressurization is used to reflect and offset the shock wave pressure. 
Obviously, the pressures discussed in this patent are orders of magnitude 
higher than the pressure used for protection of personnel from 
contaminants. Moreover, this is not a portable shelter of the type 
contemplated by the present invention. 
Another prior art device is U.S. Pat. No. 3,006,352 to Hozak, which 
discloses and claims a Door Frame and Roll-up Door Mechanism for Air 
Locks. The Hozak device is an air supported structure which has a frame 
inside the cover of the structure. The frame supports the cover of the 
structure when the pressure in the structure drops below ambient pressure. 
This device is a relatively inefficient and low pressure structure which 
does not have and does not need or suggest many of the features and 
capabilities of the present invention, as will be shown below. 
Still another prior art device is U.S. Pat. No. 2,910,994 to Joy. This 
patent discloses a very low pressure, air supported structure which has no 
frame or supports. As in the case of the Hozak patent mentioned above, the 
Joy patent is a portable shelter but otherwise bears little similarity to 
the present invention, which has a number of features and capabilities not 
found in the Joy device. The Joy device suffers from the known 
inefficiences and disadvantages of conventional air supported structures, 
as will be shown and discussed more fully below. 
Yet another prior art patent is U.S. Pat. No. 1,326,011 issued by Great 
Britain to Andrews. This British patent has a frame which, at first 
glance, bears some similarity to the frame of the present invention but 
yet is quite different, as an examination of the Andrews structure will 
show. In Andrews, the framework is inside the cover as in Hozak, while the 
present invention has a support framework which is outside the cover, 
making the present invention much more useful as a portable, quickly 
erectable and strikable shelter. The Andrews patent is nt pressurized and 
is a much less sophisticated structure than the present invention. It does 
not need and does not show or suggest many of the advanced features of the 
present invention and needed by the present invention in order to provide 
a lightweight portable shelter which protects military personnel and 
others against chemical and biological agents and against nuclear fallout, 
as will be disclosed in detail below. 
Therefore, it is a general object of this invention to provide a 
lightweight, sturdy, free-standing, quickly erectable and strikable 
all-purpose utility structure which also provides protection against 
chemical and biological agents and nuclear fallout. 
It is another object of this invention to provide a lightweight portable 
shelter having a very lightweight cover made of chemical agent resistant 
material. 
It is a further object of this invention to provide a lightweight, 
free-standing portable structure which is substantially air tight and with 
a filtered air pressure source for pressurizing the main chamber of the 
shelter to a pressure sufficient to prevent reverse air-flow of 
contaminated air into the structure but not high enough to deform the 
integral fabric floor of the shelter. 
SUMMARY OF THE INVENTION 
The present invention is suitable for a wide variety of recreational, 
military, and business uses whenever a sturdy yet quickly erectable 
portable shelter is needed. This shelter is, of course eminently suitable 
to a large number of uses by the military services, including personnel 
quarters, command and administrative quarters, vehicle and weapons 
maintenance, storage of supplies, and for field hospitals. The present 
shelter is designed to also provide whenever needed the additional 
capability of collective protection against chemical and biological agents 
and against nuclear fallout. 
In accordance with the invention, there is provided an expandable utility 
shelter comprising a plurality of inverted U-shaped structural rib members 
aligned in a parallel relationship with a series of reinforcing members 
connecting each adjacent pair of ribs on each side of the shelter. A 
substantially air tight enclosure, enclosing a main chamber of the 
shelter, is attached to the inside of the rib members, said enclosure 
comprising (1) A flexible cover comprising a chemical agent resistant 
material attached to the rib members and (2) an integral fabric floor 
attached to the flexible cover. A pressurizing means is connected to the 
flexible cover for optionally pressurizing said main chamber of said 
shelter to a pressure substantially one inch water gauge more than ambient 
pressure, said pressurizing means comprising power means for optionally 
turning on and operating said pressurizing means to insure that, when said 
pressurizing means is turned on, air enters said shelter only from said 
pressurizing means and that all other air flow is out of said shelter.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a preferred embodiment of the present invention, indicated 
generally by numeral 10, which is an improved version of the low cost and 
lightweight, yet sturdy expandable free-standing shelters, which were 
disclosed fully in U.S. patent application Ser. No. 611,851, filed May 18, 
1984, which was a continuation-in-part of the U.S. patent application 
525,001, filed Aug. 19, 1983, as mentioned above. The present invention 
retains other features which were disclosed in the earlier applications, 
namely, features which make the shelters easily repairable and capable of 
being connected together to form complexes. The present invention is a 
modification of the above-mentioned invention in that the present 
invention also provides protection against chemical and biological agents 
and protection from nuclear fallout. The present invention has a fabric 
cover assembly 11 which incorporates the "chemical and biological 
resistant camouflage material" of the type which was disclosed and claimed 
in U.S. patent application Ser. No. 309,899, filed Oct. 9, 1981, now U.S. 
Pat. No. 4,442,162 dated Apr. 10, 1984. This material, in addition to 
being resistant to chemical and biological agents, is also resistant to 
and provides protection against nuclear fallout. 
As may be seen in FIG. 1, the present invention has a plurality of inverted 
U-shaped rib members 12 which are equidistantly disposed longitudinally in 
a column. Ribs 12 may be pushed together to strike the shelter and may be 
pulled apart to extend the expandable shelter to its full size. In the 
embodiment of the shelter shown in FIG. 1, each rib 12 comprises two 
joints 13, two leg members 14, and one top member 15. Also in this 
embodiment of the invention, adjacent rib members 12 are interconnected 
and spaced on each side of the shelter by X-shaped reinforcing members 16. 
Reinforcing members 16 are formed by two reinforcing bars 17 pivotally 
connected together at their centers. 
The entire shelter unit is totally enclosed with an integral cover assembly 
11 and air-tight floor 18 which permit shelter 10 to be pressurized by a 
blower unit 20 having power cord 21. Blower 20 may be operated on an 
optional basis as desired by simply plugging in (or unplugging) power cord 
21 to a suitable power source. Power cord 21 may if desired be equipped 
with a line cord switch (not shown). Windows, entranceways, and other 
closures rae also made air-tight through the use of wide mohair fasteners 
or double- or triple-sewed seams. Blower unit 20 is connected to a gas 
particulate filter unit (GPFU) 22, which in turn is connected directly to 
the flexible cover system 11 by duct 24. CPFU filter 22, a known type of 
filter, provides protection against both liquid and gas chemical agents. 
FIG. 2 shows an alternate arrangement for interconnecting and spacing rib 
members 12 utilizing single reinforcing members 19 which provide a shelter 
structure which is lighter in weight than the arrangement shown in FIG. 1, 
yet is sturdy enough to remain servicable over a long period of time. 
As may be seen in the cut-away portion of FIG. 2, shelter 10 incorporates 
an internally sectioned area 26 which serves as a protective entranceway. 
This area, which is located in one corner of shelter 10, serves as both an 
air lock and a purge chamber. As may be seen readily by those skilled in 
the art, this internally-sectioned airlock 26 fits within the overall 
rectangular outline of the shelter 10 and therefore presents a better, 
more integrated appearance than is presented by some prior art shelters 
having an external, "tacked-on" airlock. Designed leakage from the main 
chamber 28 causes this purge chamber (or air lock) 26 to be pressurized at 
a value less than the main chamber 28 of shelter 10 but still above 
ambient pressure. This designed leakage from the main chamber 28 to the 
air lock 26 is accomplished by one or more pressure leakage holes 31 in 
the wall of air lock 26. The amount of leakage out of holes 31 may be 
adjusted by use of fabric flaps 33, which may be used to cover or 
partially cover holes 31. Thus, the pressure in air lock 26 may be 
adjusted as desired to be kept above ambient pressure. It has been found 
that a design pressure of substantially 1.0 inches water gauge (IWG) in 
main chamber 28 and substantially 0.5 IWG in air lock 26 provides shelter 
10 with near optimum pressurized protection. Incoming persons may enter 
purge chamber 26 and wait for the clean air flow to purge the contaminants 
out of the chamber before entering main chamber 28 of shelter 10. The 
arrangement described above unitizes the entry chamber (air lock) 26 and 
main chamber 28 of shelter 10 into a single air tight enclosure attached 
to the inside of the rib members 12. The air-tight enclosure, which is one 
large fabric cover assembly, comprises a flexible fabric cover 11 attached 
to ribs 12 and an integral fabric floor 18 attached to the cover 11. 
In attaching fabric cover assembly 11 to ribs 12 of the present invention, 
the fabric along the legs of ribs 12 is not attached to legs 14 as was 
disclosed in the earlier patent application. This is to enhance the 
folding characteristics of shelter 10 since a shelter with fabric attached 
to the legs is incapable of folding properly when it also has a 
permanently attached floor, as is required in the present invention. When 
the present invention is erected, fabric 11 is temporarily attached to 
legs 14 of ribs 12 and floor 18 of the shelter is tangent to the inside of 
legs 14 as shelter 10 is staked down. Staking the shelter down, using guy 
ropes 17a and stakes 23 is necessary to prevent the internal positive 
protective pressure from ballooning fabric floor 18, which would lift the 
framework off the ground and reduce the usable floor space. 
At this point, the difference between air-supported structures, such as 
shown in U.S. Pat. No. 3,006,352 to Hozak and U.S. Pat. No. 2,910,994 to 
Joy (both described previously), and pressurized structures, such as the 
present invention, should be explained. Air supported structures are not 
substantially air tight and are not designed to be so. On the contrary, 
this type of structure is relatively leaky but is supported by a very 
slight pressure above ambient pressure (about 0.1 inch water gauge or 
less) and also by considerable air flow from inside to outside, provided 
by an air compressor which must run constantly to maintain the pressure 
and air flow. This arrangement is relatively inefficient because of the 
amount of work the compressor must do to maintain the air flow. See Joy, 
column 2, lines 47-59, where Joy explains that his structure is not 
substantially air-tight and is not designed to be. Joy also explains that 
the pressure required to support his structure is only 1/500 (or 0.002) 
p.s.i. Hozak, being an air supported structure, also has similar pressure 
parameters, as discussed above. For these reasons, Joy and Hozak are not 
"pressure chambers" or pressurized structures in the same sense as in the 
present invention, as will be discussed below. 
The present invention, on the other hand, is much more efficient because it 
is comparatively air tight and maintains considerably higher pressure. For 
example, in the present invention, the pressure in the main chamber of the 
shelter is designed to be pressurized to about 1 inch water gauge (about 
1/27 p.s.i.) above the ambient pressure, a pressure approximately 10 to 15 
times as great as the pressure maintained in typical air supported 
structures (about 0.1 inch water gauge or less or about 1/270 p.s.i. or 
less). The significance of this considerable difference in the pressure 
maintained in the present invention is that it eliminates any reverse flow 
of outside "contaminated" air into the structure, whereas the pressure 
maintained in the above-mentioned, typical, air-supported structures is 
insufficient to do this. Thus, air supported structures have some backflow 
of outside air into the structure and thus could not effectively keep out 
chemical and biological agents, as the present invention is designed to 
do. 
FIG. 3 shows a pressure sensing device 29 and an indicator panel 30 for the 
purge chamber mounted on the partition between the purge chamber 26 and 
the main chamber 28 and having a window 31 allowing a person in the purge 
chamber 26 to see into the main chamber 28. On the left side of panel 30 
are three indicator lights (32, 34, 36) showing whether the pressure 
inside the purge chamber of the shelter is O.K., high, or low. High 
pressure and O.K. indicator lights 34 and 32 are yellow and green, 
respectively, while a red indicator light 36 warns of low pressure. On the 
right hand side of the purge chamber panel is a blue-colored button 38 
marked "press to purge", a red light 40 indicating "wait" and a green 
light 42 indicating "enter". When a person enters purge chamber 26, he 
closes the outer door 44 and pushes "press to purge" button 38. "Wait" 
light 40 comes on and a timer 45 mounted behind panel 30 starts timing the 
purge cycle, which involves waiting the necessary elapsed time until the 
air in purge chamber 26 has been completely purged of contaminants. At the 
end of the proper present time interval, which may involve two minutes or 
more, "wait" light 40 turns off and "enter" light 42 is turned on. At the 
same time, audible signal device 46 sounds, to provide an additional 
indication that it is now safe to enter the main chamber 28. The person 
may then open door 48 into main chamber 28 of the shelter and enter. Even 
when door 48 between air lock 26 and main chamber 28 of shelter 10 is 
opened for a short period of time, any possible contaminants present in 
air lock 26 will not enter main chamber 28 of the shelter. This is because 
air lock 26 is arranged to be pressurized above ambient pressure but below 
the pressure of main chamber 28 of shelter 10. 
On a wall of main chamber 28 of shelter 10 is an indicator panel 50 which 
indicates the pressure range in the chamber. As may be seen in FIG. 4, 
indicator panel 50 (which is operatively connected to a known type of 
pressure sensing device 52) has three indicator lights 54, 56, and 58, one 
of which will normally be on at a given time. Yellow indicator light 54 
indicates "high pressure", green indicator light 56 indicates "pressure 
O.K.", while red indicator light 58 comes on if the pressure drops down to 
"low pressure." In addition to these visual indicators, an audible alarm 
60 will provide a warning of "low pressure." The alarm may be switched on 
or off by double-throw, single pole switch 62. Thus, pesons who are 
working or sleeping in the shelter will be warned of dangerously low 
pressures which would no longer provide adequate protection against 
chemical or biological agents. However, switching off alarm 60 by the use 
of switch 62 enables usage of the shelter in the unpressurized mode 
without the annoyance of having the alarm sound when it is not needed. 
One important feature of the invention is the coupling of pressure sensor 
29 with the purge timer 45 (FIG. 3). This feature causes timer 45 to be 
reset to zero if the pressure in the purge chamber 26 drops to the low 
range during the purging cycle, thus preventing a false "purge complete" 
signal when improper purging pressures are present. 
When shelter 10 is being used with the option to provide protection against 
chemical and biological agents, blower 20 must operate, which requires a 
source of electrical power for the system. To make the shelter system 
extremely versatile so that it may operate under widely varying 
conditions, a universal power supply was developed and made part of the 
system. The system operates on 28 volts, D.C., which is the typical 
vehicular power presently available. However, the power supply will also 
utilize various other power inputs as follows: 110 volt 60 Hertz A.C. or 
220 volt 60 Hertz A.C. from U.S. commerical power lines or small 
generators, 230 volt 50 Hertz A.C. from European or other foreign 
commercial power lines, or 208 volt 400 Hertz A.C. aircraft power or U.S. 
Air Force A.C. generator. This system may be separately packaged as a 
blower which would supply air flow to a separate filter or designed into a 
unitized filter/blower unit. 
The capability of utilizing different power supplies is accomplished by 
providing the air flow with 28 volt D.C. blower motors. A single 
transformer 63 with a split primary and a 208 volt tap is used to 
transform the other power supplies to 28 volts. The means of switching 
from one power supply to another is automatically accomplished by the 
power cord used. A different power cord is supplied for each power supply. 
The 110 volts 60 Hertz power cord has a standard 110 volt plug on the end 
and when connected to the unit automatically makes the proper connections 
to operate on 110 volt power. In similar fashion, each of the other power 
cords has a unique plug for that particular voltage. This method of 
switching eliminates operator error so that the power cords fit only the 
proper supplied power and make the proper connections to the power supply 
to operate on that particular power. Thus, the possibility of making 
improper connections to the power supply is virtually eliminated. 
Looking now to FIG. 5a, a circuit diagram 64 for the universal power supply 
is shown. Connections for inlet plug 66 are shown on the left side of the 
diagram. Circuit breakers 68 are shown in the leads marked E and G. An 
on/off switch 70 is shown at the top of the diagram. Connections for 
outlet plug 72 are shown in the center of the diagram. An hour meter 74 to 
register the acccumulative running time for the supply is shown at the 
right hand side of the diagram. 
Input connections for the various power cords are shown in FIGS. 5b-5f, 
inclusive. FIG. 5b shows the input connections for the 28 volt D.C. power 
cord. FIG. 5c shows the input connections for the 110 volt 60 Hertz power 
cord. FIG. 5d shows the input connections for the 220 volt 60 Hertz power 
cord. FIG. 5f shows the input connections for the 208 volt 400 Hertz power 
cord. 
FIG. 6 shows the front panel for the universal power supply. At the upper 
left side of the panel are shown circuit breaker switches 76. Immediately 
below the circuit breaker is an on/off switch 78. At the lower right of 
the panel is a receptacle 80 for inlet plug 66 and at the lower center of 
the panel is the outlet plug 82. The transformer is mounted on the inside 
of the panel with four bolts 84 which show in the center of the panel. 
Hour meter 74, which shows the accumulated running time for the unit, is 
shown at the upper right portion of the panel. 
FIG. 7 shows the rear end of the shelter, as viewed from the inside of the 
shelter. The present invention is equipped with an emergency exit door 25 
having a zipper fastening 27 which is operable only from the inside of the 
main chamber of the shelter. Obviously, this door 25 may take several 
different configurations. However, in the preferred embodiment of the 
invention, this emergency door 25 is a "D" shaped zippered closure 27 in 
the center of the rear end of the shelter. This allows the occupants of 
the shelter to exit fast in case of an emergency, but prevents accidental 
opening of the shelter which would result in depressurization of the 
chamber with possible danger to the occupants. To open the emergency door 
25, zipper handle 27' is pulled to the right, then down, and then to the 
left. 
As herein disclosed, the present invention relates to a greatly improved 
expandable utility structure which is free-standing, sturdy, light in 
weight, easy to manufacture, easy to repair, quickly erectable and 
strikable, yet provides collective protection against chemical and 
biological agents and against nuclear fallout. The device has the 
advantage that it may be utilized as a portable, expandable shelter for 
conventional uses without the need for a blower or other devices requiring 
electrical power, yet may be used to provide collective protection when 
needed.