Note: Descriptions are shown in the official language in which they were submitted.
~ 2 2 ~ ~ 3 3 ~ ~
~he valve arrangements for conventional breathlng
apparatus are relatively large and, for such breathing
apparatus as is intended to afford protection again~t a
hazardous environment, the ma~k extend~ to the upper regions
of the wearer's face and iDcludes an aperture, closed by a see-
throu~h panel. Because of the limited size of the mask the
see-through panel i8 relatively small and restricts the
wearer's vision.
A serious problem with helmeticonventional breathing
mask arrangements as defined above resides in the fact that the
helmet is completely independent of the breathing apparatus and
the helmet is ill-fitting and uncomfortable on the straps
supporting the breathing mask. Further, with the forward
regions of the mask supporting the valve arrangement and air
supply duct, the forward mask parts project forward of the brim
! of the helmet and the helmet affords little, if any, protection
for the ~aid forward parts of the breathing apparatus.
Further, as the mask is essentially flexible, the
forwardly projecting valve arrangement and air connections to
the mask are susceptible to dislodgement, particularly in poor
vi~ibllity and crowded condition8, and if di8lodged the
hazardous atmosphere can enter the breathable volume of the
mask, to the detriment of the wearer.
In more recent years 90 called "total" protective
helmets incorporating breathing apparatus have been proposed
and which helnets protect the whole of the head of the wearer
down to the neck level.
Such helmets, generally made from a plastics
material, conveniently include a large aperture, closed by a
see-through panel, uith a flexible seal extending from the
periphery of the see-through panel inwardly of the helmet to
- define a seal with the face of the wearer. Thus, the whole of
the face of the wearer is open to the enclosed volume defined
by the seal, the see-through panel and the face of the wearer.
Valve arrangements, often attached externally to the helmet,
duct breathable atmosphere to the said volume and some such
- 2~3~s~
-- 3 --
helmets may include an exhalation valve, generally pas~ing
through the see-through panel, and through which valve exhaled
air is exhausted.
An inherent disadvantage of with the prior art
"total" protection helmets is that whilst the helmet is being
worn the wearer is totally dependant upon a breathable air
~upply to the ~aid enclosed volume and, when the air supply
comprises a tank or reservoir carried by the wearer, the time
period for which the helmet can be worn is severely limited.
Further, as the helmet must be fitted before the wearer
enters a hazardous envlronment and must not be removed until
after the wearer has left the hazardous environment the actual
amount of time the wearer can be exposed to the hazardous
environment i5 restricted.
A further disadvantage of such helmet and integral
breathing apparatus combinations is that they are extremely
expensive.
In many rescue and/or fire fighting applications
personnel may be designated to areas of operation which do
not include a hazArdous atmosphere and, therefore, such
per~onnel do not require a breathing apparatus. In other
areaY of operation of operation personnel will be expected to
enter a hazardous envlronment, in which cases they will
require a breathing apparatus. In most rescue operations, and
again in particular in fire fighting, the conditions of the
environment in which personnel are to work may not be
determined until arrival at the site.
The present invention seeks to provide a safety helmet
capable of being selectively used with or without a breathing
apparatus.
According to the present invention there is provided a
safety helmet, adapted to totally encase the head of the wearer
and including a see-through aperture through its forward
regions, characterised by a rigid, closed frame engageable
with the interior of the helmet concentric with the said see-
through aperture, an annular seal having one continuou~ end in
,
' _ 4 _
sealed relationship with the frame and concentrlc there~lth and
its other continuous end arranged to engage the face of the
wearer across the forehead, down the cheeks and across the
chin, and quick-release means for selectively attaching a
breathing apparatus to said helmet.
Preferably the helmet includes a harness comprising
straps for supporting the helmet on the hefld of the wearer and
a padding engageable with the rear of the head of the wearer.
Preferably the said annular seal is resilient and the
said straps of said harness are adjustable to allow the front
to rear position of said padding to be adjusted relative to the
said annular seal.
In one embodiment the see-through aperture in the
helmet shell is totally closed by a see-through panel.
In one embodiment an exhalation valve is supported by
the said see-through panel.
In a preferred embodiment a nose cone extends from
the said see-through panel to engage the face of the wearer
with a continuous seal surrounding the breathing ducts of the
wearer, said exhalation valve is arranged to exhaust from the
volume defined by said nose cone and said nose cone includes
valve means for allowing air flow into said nose cone from the
volume defined by the said annular seal, the see-through panel
and the face of the wearer.
Preferably the safety helmet is used in combination
with valve means and air ducts, arranged to supply pressure
air from an air source externally of the helmet to the volume
forward of the wearer's face and defined by the said annular
seal, the see-through panel and the face of the wearer bounded
by the said annular seal.
Preferably the said rigid closed frame is detachably
retained in said helmet shell by said quick release means.
In one embodiment said see-through panel and said
valve means and said air ducts are supported by said rigid
closed frame to be detachable therewith.
In one embodiment the helmet includes an internal
2a~3~
-- 5
cavity below the aperture and said valve means and air duc~s
are attached to the lower reglons of said rigld closed frame
and are housed in said internal cavity when the rigid closed
frame is fitted to the helmet shell.
In one embodiment the rigid closed frame is detachable
rom the helmet shell by releasing said quick release means and
said frame is interchangeable with a second rigid closed frame
supporting an annular seal extending to the face of the wearer
and whereby the volume defined by said annular seal is open to
the surrounding environment.
With such an embodiment the said second rigid closed
frame is detachably retained ~ithin the helmet by said quick
release devices and said annular seal is attached to said
second rigid closed frame to be detachable therewith.
Preferably said quick-release means comprise rotatable
devices adjacent the aperture through the helmet and arranged
in one rotational position for each device to securely clamp
the said rigid closed frame with the helmet shell, and in
another rotational position for each device to release the
said rigid closed frame from the helmet.
In another embodiment the helmet is characterised by a
duct connecting the volume deflned by the annNlar seal to the
atmosphere externally of the helmet.
Preferably the said duct comprises a flexible
connection between the volume within the annLlar seal and an
aperture through the helmet.
In one embodiment said duct is selectively closable by
an air supply assembly.
Preferably the said air supply assembly comprises an
air supply valve arrangement contained in a housing and an air
supply from a air reservoir to said air supply valve
arrangement and wherein said quick- release mean comprise means
for selectively connecting or disconnecting the air outlet from
said housing to said duct.
2 ~
-- 6 --
In one embodiment the said quick-release means
comprise cooperating interrupted screw means presented by said
housing and said duct.
~ he invention will now be described further by way of
example with reference to the accompanying drawings in which,
ig. 1 shows a cross section, on the central plane passing
front to rear of a helmet, with a breathing apparatus
attachment.
ig. 2 shows, diagrammatically, a view of the forward lower
regions of the mask, from the inside, with breathing
apparatus contained therein,
ig. 3 shows a croQs section in the same plane as that for
Fig. 1, of an open front helmet attachment for use
with the helmet illustrated in Fig. 1,
ig. 4 shows a plan view of a quick-releaqe device in
accordance with the invention,
7 ~ ~ 6 .5 ~
Fig. 5 ~how~ a side view of the quick-release device sho~n
in Fig. 4,
Fig. 6 show~ an underneath view of the quick-release device
shown in Fig. 4 and 5.
Fig. 7 shows one end view of the quick-release shown ln
Figs. 4, 5 and 6 and,
Fig. 8 shows, in perspective view, a fragment of the rigid
closed frame and annular seal ~ith an integral lug
engageable by the quick-release device.
Fig. 9 shows, a left side view of the lower forward region of
a safety helmet incoporating means for selectively
connecting a further embodiment breathing apparatus to
the helmet,
Fig. 10 shows a cross-section through the left side of the
helmet on the line II II in Fig. 9,
Fig. 11 9how8 a side view of a breathing apparatus connecting
means for u9e with the helmet shown in Figs. 9 and 10,
and
Fig. 12 shows a view of the breathing apparatus connecting
means in the direction of the arrow A.
The helmet illustrated in Fig. 1 conveniently
comprises a one piece helmet 11, made from a pla~tics material
conventionally by a moulding process, with an aperture 12 in
the forward regions thereof. The helmet 11 is of thickened
material, indicated at lla, around the neck aperture to ensure
a safety edge therefore.
The helmet 11 includes an internal harness comprising
a top pad 13, supported on each side by resilient straps
2 ~ o ~
-- 8
14, with each strap 14 pa~sing through a slot in an anchor
plate 15 secured by a screw 16 engaged in a nut (not ~hown)
moulded into the helmet shell.
The pad 13 is lntended to contact the head of the
wearer, thus to support the top of the helmet in spaced
relationship with the head of the wearer.
The harness also includes a back pad 17, pivotably
connected at it~ upper regions to the rearmost regions of the
pad 13, and pad 17 is further supported on each side by a
resilient strap 18, which passes through a slot in an anchor
plate 19 secured to the helmet by a screw 20 engaged in a nut
(not shown) moulded in~o the hel~et shell.
The pad 17 had it~ lower regions 17a extending
adjacent to, and preferably projecting from, the neck opening
of the helmet 11 whereupon the wearer can manually displace
the lower regions of the pad 17 towards the rear of the helmet
11 to assist in donning and removing the helmet 11.
The pad 17 also includes side straps 21, attached one
to each side of the pad 17 near lts lowermost regions, each
~o ~trap 21 include a row of stud astener sockets 22a, 22b,
22c, 22d and 22e selectively engageable with the cooperating
part of a stud fastener (not shown) secured to the helmet and,
in the present example, located in the region of the fastener
22b as illustrated.
The helmet also includes a peak member 23, made from a
transparent material, secured to the shell immediately above
the aperture 12 and projecting downwardly to partially close
the aperture 12 and forwardly of the helmet to divert small
falling solids or liquids away from the aperture 12.
In the example illustrated in Fig. 1 the helmet is
provided with a breathing apparatus attachment comprising a
see-through panel 24 which closes the aperture 12, with a
resilient sealing element 25 interposed between the peripheral
regions of the see-through panel 24 and the helmet surface
adjacent the aperture 12. An annNlar seal 26 has one
continuous or radial end region 26a splayed outwardly and
contacting the peripheral regions of the inner surface of the
see-through panel 24 and t~e assembly is retained by a rigid
closed frame 27. ~he elements 24, 25, 26 9 and 27 are
concentric with the aperture 12 and preferably the elements 25,
24, 26a and 27 are bonded together as, for e~ample, by an
adhesive 90 as to form a composite assembly.
As will be seen from Fig. 1 the lower forward regions
of the helmet 11, that part of the helmet 11 below aperture 12,
i9 formed to provide enlarged internal cavity, generally
indicated by reference llb, and the frame 27 includes an
extension 27a extending into said cavity to support an air
supply and control valve arrangement 28 for a breathing
apparatus. ~he valve arrangement 28 is provided with pressNre
air via a duct 29 which extends from the valve arrangement 28
through the neck aperture in the helmet, conveniently to one
side of the neck aperture, and said duct 29 extends to a
pressure air reservoir (not shown) such as a cylinder carried
by the wearer of the helmet 11 as a back pack.
~he valve arrangement 28 includes a sensor duct 30,
2~ which pro~ects through the frame 27 and the seal 26 so as ~o be
open to the atmosphere within the annular sesl 26. The duct
30 19 open to a msnifold 31 which is open to a sensing port in
the valve arrangement 28 whereupon, on sensing a pressure
below a predetermined pressure via the sensor duct 30, the
valve 28 is arranged to open to alloR air flow from the duct
Z9 through the valve arrangement 28 to a m~n~ fold 32 from
which the air flows via an outlet 33 into the volume within
the bore of seal 26.
Ihe valve arrangement 28 may also include a manual
over-ride, generally indicated at reference 34, and Rhich can
be manually actuated by the wearer, or any other person in the
vicinity, pushing a finger up the nec~ aperture of the helmet
to press the over-ride button 34~ thu~ allowing air floR into
the volume within seal 26, if the wearer should ~xperience
breathing difficulties.
~he breathing assembly further includes an
2 ~ 6 ~ 3
exhalation valve 35 ~hich pas3es through the see-through panel
24 and supports, at its inner end, a nose cone, generally
indicated by numeral 36, and which includes two one-way valves
37 one on each of it~ sidesO Ihe nose cone 36 may be
forwardly and rearwardly displacesble by adjusting means, well
known in the art, included in the exhalation valve assembly.
l~he frame 27 further include~, at each of its
oppo~ite side edge regions, an integral lug 27b ~ith an
arcuate recess 27c in its peripheral edge region, as shown in
Fig. 8.
The sealing element 25, the see-through panel 24, the
annular seal 26, the valve arrangement 28, the manifold3 31 and
32 and the ducts 30, 33 and 29, are all supported by the rigid
closed frame 27 and the frame 27 and all the elements supported
by said frame 27 comprise an assembly detachable from the
helmet 11.
One form of quick-release device suitable for
supporting the rigid frame 27 and its supported assembly with
the helmet illustrated in Figs. 1 and 2 is shown in Figs. 4, 5,
~0 fi and 7 ~nd wherein the quick-release device comprlse8 a solid
body, generally lndicsted by numeral 40, with an aperture 41
therethrough by which the body 40 is pivotably attached to the
helmet via a pivot screw 42, secured in a nut (not shown)
embedded in the helmet 11. Ihe aperture 41 is counter-bored,
as at 41a, to receive the head of the screw 42 therein.
The body 40 includes, at its end regions st remote
from the aperture 41, a cylindrical element 43, having its
axis parallel to the axis of the aperture 41, and a roof-like
projection part 44 above the cylindrical element 43 extends
radially and terminates forwardly of the said element 43.
~hen two such quick-release devices 40 to 44 are
fitted to the helmet 11, one adjacent each side edge region of
the aperture 12, and with the pivot screws 41 secured in their
respective nuts, the said quick-release devices are pivotable
about their respective pivotable screws 42.
When a breathing apparatus assembly comprising a rigid
2 ~
frame 27 and its supported assembly 24, 25, 26 and 28 to 37 is
to be fitted, the qulck-release devices 40 to 44 are pivoted to
po~itions where their ends presenting the cylindrical elements
43 are most remote from the aperture 12, whereupon the
breathing apparatus assembly 24 to 37 can be entered into the
helmet 11 and located therein with the resilient sealing
element 25 in pre~sure contact with the helmet surface
surrounding the aperture 12. The quick release devices 40 to
44 are then pivoted 80 that their roof like projection parts 44
engage over the free side 27d of the adjacent lug 27b and the
cylindrical element 43 of each quick release device 40 to 44
engages ir. the adjacent arcuate reces~ 27c in the adjacent lug
27b.
The quick-release devices 40 to 44 are in pres Æ e
contact with their respective arcuate recesses 27c in the frame
27 and thus, with preYsure contact on its side edge reglons,
the frame 27 compresses the sealing element 25 between the
helmet surface and see-through panel 24, thereby effectively
sealing the opening 12 from the surrounding environment.
To remove the breathin8 apparatus as~embly 24 to 37
it i9 only neces~ary to rotate the quick release devices away
from thelr adjacent lugq 27b, whereupon the breathing apparatus
assembly is released from its locking contact with the helmet
11 and can be readily removed thr~ugh the neck opening of the
helmet.
To use the helmet 11 with the breathing apparatus
assembly 24 to 37 fitted it i9 only necessary for a person to
release the straps 21 from engagement with their respective
pres~ ~tud fastener~, manually di~place the rear pad 17 toward~
~o the rear of the helmet and the helmet can be donned. The
wearer will retain the rear pad 17 rearwardly until the free
edge region~ of the seal 26 are in a comfortable sealing
engagement with the face of the wearer and the rear pad 17,
can then be released to advance forwardly, via the resilient
straps 18. The weæer can then make final adjustments to the
fitting of the helmet 11, by holding the helmet 11 between the
- 12 _ ~ ~ 6 ~
hand~ and pushing back with the head against the rear pad 17 to
ensure a comfortable sealing fit with the seal 26, and the
helmet is then secured by pulling the straps 21 forwardly and
securing the appropriate press stud fitting 21a to 21e to the
re~pective press stud fastener.
With the helmet ll firmly, but comfortably, fitted to
the wearer the seal 26 i8 in sealing contact with the wearer's
face across the forehead, down the cheeks and across the chin
and the volume defined by the panel 24, annular seal 26 and the
face of the wearer, hereinafter called "the first volume" is
being continuously sensed by the sensor duct 30. When the
sensor duct 30 detects a pressure fall in the said volume,
below a predetermined pressure which i9 preferably ~lightly
above atmosphere, the valve arrangement 28 is actuated to
supply air via manifold 32 and duct 33 to said first volume.
When the pressure in the said first volume rises above the said
predetermined pressure the elevated pressure is sensed by the
duct 30 and the air supply though valve 28 is terminated.
Ihe breathing ducts of the wearer open to the volume
within the nose cone 37, herein~fter called "the second
volume," and on lnhallng alr flows from the said first volume
to the second volume vla the one way valves 37 and, on
exhaling, the valves 37 close and the exhaled air is exhau~ted
from the second volume via the exhalation valve 35.
To remove the helmet it is only necessary to release
the straps 21, push the rear pad 17 towards the re æ of the
helmet using the fingers or simply pushing the helmet forward
on the head 90 that the head deflects the reOE pad 17
rearwOE dly, to release the face from sealing contact with the
3o seal 26, and the helmet can be readily removed.
Fig. 3 shows an alternative attachment for the helmet
- 11 when the breathing app OE atus assembly 24 to 37 had been
removed from the helmet 11.
The attachment illustrated in Fig. 3 comprises a
resilient sealing element 51, intended to contact the internal
surface of the helmet 11 surrounding the aperture 12, an
- 13
annular seal 52, which may be identical with the annular ~eal
26 illustrated in Fig. 1 and which include~ an outwardly
turned flange region 52a in contact with the sealing element
51, and a rigid closed frame 53, identical to the rigid frame
27 and which includes lugs 53b, identical with the lugs 27b of
the frame 27 shown in Fig. 1. The sealing element 51, the
flanged part 52a o~ the seal 52 and the frame 53 are secured
together, conveniently by an adhesive, to form a composite
assembly.
The attachment 51 to 53 is fitted to the helmet in
identical manner to the breathing apparatus a~sembly 24 to 37,
in that the ~ealing element 51 is located again3t the internal
surface of the helmet 11 surrounding the aperture 12 and the
quick-release devices 40 to 44 are rotated until each roof-
like elements 44 engage with the free surface 57d of the
associated lug 53a and the cylindrical element 43 i9 located in
the recess 53c of the adjacent lug 53b.
It should be noted that the sealing element 51 in the
attachment 51 to 53 is at least as thick as the combined
thickness of the sealin~ element 25 and the panel 24 in the
Flg. 1 embodiment 80 that the roof-like parts 44 of the quick-
release devices are in pressure contact with the free Æ face
53d on their respective lugs 53b and the cylindrical elements
43 are in pressure contact with their respective arcuate
recesses 53c, ~hereupon the rigid frame 53 causes the resilient
sealing element 51 to be in compression, thus to retain the
assembly 51 to 53 se ely with the helmet 11.
With the attachment 51 to 53 se ed ~ithin the helmet
11 the helmet 11 is donned in identical manner to that
described above with reference to the Figs. 1 and 2 eDbodiment,
the free edge of the seal 52 makes the same seal with the face
- of the wearer as described for the Fig. 1 embodiment but, in
this case, the volume forward of the wearer's face exposed
within the seal 52 is open to atmosphere.
Ihus, the seal 52, in combination with the rear pad
17, firmly locate the user's head front to rear with respect
- 14 _ 2 ~
to the helmet to en~ure the greatest protection for the
wearer's head.
The helmet arrangement described above, in combination
with the breathing apparatus attachment 24 to 37 and with the
inter-changeable attachment 51 to 53 available, i9 particularly
advantageous for fire fighting applicatlons where, on route
for a fire, all the fire fighting personnel may fit the
breathing apparatus attachment 24 to 37, to the helmet and
cement the air supply duct 29 to an air supply tank carried as
a back pack.
Cn arrival at the site those personnel to work in a
hazardou~ environment, or a potentially hazardous environment,
can simply fit the helmet, shoulder the back pack and move
immediately into action.
In the event there is not hazardous environment, or
for those selective personnel who are not to work in the
hazardous environment, it is a simple matter to release the
breathing apparatus asRembly 24 to 37 from the helmet, fit the
second attachment 51 to 53 to the helmet and the flremen can
then move Lmmediately away from the vehicle, leavlng the back-
pack with the breathlng as~embly 24 to 37 attached thereto.
In the cmbodlmYnt illustrated in Fig. 9 a helmet 51 i~
substantially identical to the helmet 11 illustrated in Fig. 1,
with the exception that the see-through panel 24, the annNlar
seal 26 and the rigid closed frame 27 are permanently secured
in the helmet 11 and the helmet shell includes an aperture 52
adjacent the left side edge of the see-through panel 24.
A sleeve 53 is located in the aperture 52 and said
sleeve 53 defines a cylindrical section 54 adjacent one end
3o region 53, a radial fl~nge 55 and a threaded section 56 on that
side of the flange 55 remote from the cylindrical part 54.
The sleeve 53 has a througn bore 57 with an
interrupted screw thread 58 in that end of said bore radially
aligned with the threaded section 56.
The sleeve 53 is secured in the aperture 52 by passing
the threaded section 56 from the inside of the helmet through
2~3~
- 15
said aperture 52 90 that said threaded 56 projects externally
of the helmet and the ~leeve 53 is secured by a nut 59 engaged
on qaid threaded part 56.
The nut 59 i9 firmly ~ecured on the thread 56,
whereupon the helmet shell 51 surrounding the aperture 52 i9
firmly trapped between the flange 55 ~nd the nut 59 and the
sleeve 53 is securely held against rotation.
A flexible tubular element 60 presents a cylindrical
section 61 into which the cylindrical section 54 of the
sleeve 53 is entered and secured, as by an adhesive, or by a
jubilee clip surrounding the cylindrical section 61. The mid-
region 62 of the tubul æ element 60 is of concertina form and
the end region 63 remote from section 61 iq cylindrical and
includes a radial flange 64 on its outer end. The flange 63
and the end region 63 enter through an aperture 65 in the
seal 26 and the annNlar flange 64 is bonded to the seal 26 to
define a gas tight seal therewith.
It will now be seen that with the embodiment described
thus ar the volume defined by the annular seal, the see-
through panel and the face o~ the wearer i8 in open
communication with the surrounding atmosphere via the open
bore of tubular element 60 and the bore 57 in the sleeve 53.
The breathing spparatus attachment for the helmet
comprises a valve housing 70 of generally cylindrical form
2~ with a concentric boss 71.
The boss 71 includes an interrupted screw thread,
defined by elements 72 and a duct 73 from an air supply source
(not shown) ducts air to the valve housing 70.
The external diameter of the screw thread elementq 72
3o is such that with the screw thread elements 58 and 72 out of
alignment the boss 71 can enter into the bore 57 of the sleeve
53.
Ihe housing 70 includes a con~entional breathing
apparatus demand valve, arranged to supply air to the bore 57
of sleeve 53, and via bore of the tubular element 60 to the
volume defined by the annular seal 26, the see-through panel
- 16
and the face of the wearer, when the pressure in 3aid volume
falls below a predetermined level.
Such breathing apparatus supply valves are well known
ln the art in many form~ and no further description of the
valve arrangement or the principal of operation i~ required
herein.
~he valve arrangement may also include a manually
actuable by-pas~ actuator button 75 arranged to by-pass the
demand valve, to supply air directly through the valve
arrangement when required.
To fit the housing 70-71 with its internal valve
arrangement it is only neces3ary to enter the boss 71 lnto the
bore 57 of the sleeve 53, with the interrupted screw thread~ 58
and 72 out of register, and then to rotate the housing 70-71
through ninety degrees to engage the interrupted threads 58,
72, and whereupon the housing 70-71 is locked with the helmet.
A resilient seal 74 is provided on the radial face of
the houYing 70 and surrounding the boss 71 and said member 74
is compressed between the nut 5g and the radial face of the
housing 70 when the housing 70-71 i8 locked with the sleeve
53.
~he radial position of the sleeve 53 is so selected
that when the housing 70-71 is locked with the sleeve 53 the
duct 73 is lying in its natural uhstressed position to extend
to the air reservoi., so that the duct 73 is not
circumferentially loading the housing 70-71 towards an
unlocked position or to an over-locked position, but in the
event, housing 70-71 may include a latch mechanism (not shown)
engageable with the sleeve 53, nut 59 or the helmet casing 51
to retain the housing 70-71 locked with the helmet when in
use.
- It will now be seen that with the housing 70-71
disconnected from the helmet 51 the wearer is breathing
atmospheric air via the bore 57 and the bore in the element 60.
When it is de~ired to attach the breathing apparatus it is only
necessary to insert the boss 71 into the bore 57, rotate the
2~6a30~
hou~lng 70-71 through ninety degrees to lock the housing 70-71
in the bore 57, and the bore of the tubular element and the
volume forward of the wearer's face bounded by the seal 26 and
~ee-through panel 21 are isolated from the ~urrounding
atmo~phere and air can be supplied to the wearer via duct 73
and the housing 70-71
To disconnect the breathing ~pparatus it i9 only
necessary to relea~e any latch mechani~m retaining the housing
70-71 with the helmet, rotate the housing 70-71 through ninety
degrees and the housing 70-71 can be disconnected from the
helmet 51, again to connect the volume forward of the we æer's
face with the surroun~1ng atmosphere.
