Airtight helmet

May 10, 1960

F. W. ANDREWS ET AL

AIRTIGHT HELMET

2,935,985

<img file="US2935985A_D0001.tif" />

<img file="US2935985A_D0002.tif" />

ATTORNEYS.

May 10, 1960 f. w. Andrews etal 2,935,985

AIRTIGHT HELMET

Filed Nov. 19, 1951

Sheets-Sheet 2

<img file="US2935985A_D0003.tif" />

ATTORNEYS.

May 10, 1960

F. W. ANDREWS ET AL

AIRTIGHT HELMET

2,935,985

Filed Nov. 19. 1951

Sheets-Sheet 3

<img file="US2935985A_D0004.tif" />

ATTORNEYS.

May 10, 1960

F. W. ANDREWS ET AL

AIRTIGHT HELMET '

2,935,985

<img file="US2935985A_D0005.tif" />

<img file="US2935985A_D0006.tif" />

ATTORNEY'S.

May 10, 1960

F. W. ANDREWS ET AL

AIRTIGHT HELMET

2,935,985

Filed Nov. 19, 1951

Sheets-Sheet 5

<img file="US2935985A_D0007.tif" />

May 10, 1960

F.W. ANDREWS ETAL

AIRTIGHT HELMET

2,935,985

<img file="US2935985A_D0008.tif" />

United States Patent Office Patented May 10, I960 ^{; 1}

2,935,985 /

AIRTIGHT HELMET ₅

Frederick W. Andrews and Wilbur A. Miller, Dover, Del·, and Walter L.Ludwig, Denton, Md., assignors to International Latex Corporation, Dover, Del., a corporation of Delaware

Application November 19, 1951, Serial No. 257,002

Claims. (Cl. 128—141) sure helmet having a comfortable seal between the lower portion thereof and the wearer’s neck.

Another object is to provide a helmet of the character described closely conforming to the contour of the wearer’s head and adapted for close fitting contiguous thereto, throughout the major portion thereof, while permitting freedom of movement of the chin.

Another object is to provide a pressure helmet permitting ready movement of the encased head when the helmet is pressurized. ^L

A further object is to provide a helmet having means to relieve the head of the wearer of uplift pressure when the helmet is pressurized. , . - ,^;h.'

Another object is to provide a combined crash and pressure helmet. ... ..,

Another object is to provide a crash helmet which can withstand high velocity air flow. , .

Further objects,'advantages and features of the invention will be understood from the following detailed ;0 description taken in connection with the accompanying drawings hereinafter referred to and in which. .

Fig. 1 is a side elevational view, partly in section, ana With certain parts omitted, for simplicity, showing a present embodiment of the invention in position for use;

&gt;- Fig. 2 is a similar view of the front portion of the device of Fig. 1 with its face piece and outer shell removed;

Fig. 3 is a similar view of the face piece detached from the remainder of the device of Fig. .1; , . ; . ..

Fig 4 is an enlarged (approximately full size) side ₁₀ elevational view of the front portion of the device of Fig. 1, showing certain parts in section to better illustrate certain details and certain parts omitted for simplicity; .

Fig 5 is a front elevational view of the device on the same scale as shown in Fig: 1, showing means through as which oxygen mgy be introduced and spent exhalation emitted, microphone mount and plug-in means which were omitted from Figs. 1-4; ,

Fig. 6 is a cross-sectional view taken on the line 6__6 _Of Fig. 5 showing further details of the face panel seal;. '

Figr 6α is a crossreectiohal view taken on line βα—οα of Fig. 5 showing further details of the plug-in and microphone mount;.

Fig. 7 is an enlarged cross-sectional view taken on 45 line 7—7 of Fig. 1 showing details of the zipper closure and outer shell joint; . ‘ .'

Fig. 8 is an enlarged cross-sectional view taken on line 8—8 of Fig. 1 with certain parts omitted to more clearly show the collar structure of the bladder; . &lt; .

Fig. 9 is a segment, in elevation, of the parts illustrated in Fig. 8;.

Fig. 10 is a side elevational view of the device shovyn in Figs 1-9, on a somewhat ,reduced scale, with certain p?artsibxoken;away to show/iurther details of the interior 55 structure, more particularly the shock pads;

Fig. 11 is a plan view showing the arrangement ot . the pads of Fig. 10; : \ . ... . . ,

Fig. 12 is a diagrammatic side elevational View illustrating pressure distribution in the use of the device 60 shown in Figs. 1-11 and the resultant uplift pressure;

Figs. 13-14 are side and front elevational views, respectively, of the device shown in Figs. 1-1,1 Xwith certain parts Omitted for simplicity) showing further details of the means for resisting the uplift pressure; . _;

Fig. 15 is a diagrammatic side elevational view, similar to Fig. 12, illustrating the pressure distribution in. a ; modified device in which provision is made to equalize the' uplift pressure in the helmet, instead of externally resisting it as in Figs. T-14; : .- . .·

70^! Fig. 16 is a side elevational view, partly in section, showing, a modified form of helmet embodying the pnnciples diagrammatically illustrated in Fig. 15;

This invention relates to an airtight helmet or head 15 piece adapted to enclose the head of the wearer. Since the intended purpose of the invention is to provide a helmet which will permit a relative internal pressure to be attained and maintained at desired periods of use it will be designated a pressure helmet for convenience. 20 The internal pressure being relative to and greater than the external pressure, the degree of pressure will vary as to the environment in which the helmet is used.

- The particular embodiment to be described hereinafter, as illustrative of the invention, is intended particu- 25 larly for the use of aviators and aircraft personnel subjected to high altitude operations where the atmospheric pressure is drastically reduced. However, the invention is believed to be well adapted for other uses, .such as for divers. In fact, in its broadest aspects the invention is 30 useful wherever it is desirable to encase the human head in an airtight chamber or a chamber which is capable of maintaining a positive internal pressure to prevent ingress from the external, such as poisonous gases. The invention may either be used separately as a helmet or 35 may be attached to a suit of any of the well known forms for encasing the body, either an inflatable (pressure) suit or a tightly fitting suit, both of which types are known to those skilled in the art, ., ,

It is well known that at high altitudes the human body 40 must be encased in such a manner as to protect it from the extremely low pressure of the atmosphere and in order to facilitate breathing the oxygen supplied must be under pressure greater than the external air pressure and to relieve the head of the wearer from dangerous abnor- 45 mal lbw pressure. It is advantageous also to have the head of the wearer subjected to a pressure greater than , the external pressure and to supply the oxygen into the pressurized enclosure. For this reason it has been proposed to provide helmets to entirely encase the human 50 head; but many difficulties have been encountered.

One of the chief difficulties has been to provide a pressure helmet which meets the several requirements of aviators. Such a helmet must effect a sure seal around the neck, in order to provide a relatively small chain- 55 ber into which oxygen may be supplied for. inhalation and also to permit of pressurization to the desired extent. · Additionally, there must be a transparent front panel or face piece and this should be readily removable and replaceable with alacrity and certainty of re-establishing 60 sealed relationship. Further, comfort and freedom of head movement of the wearer are of . extreme importance. From the standpoint of storage and handling, as well as for comfort, the helmet hood preferably should be collapsible and flexible to a large extent.

An object of this invention is to provide an improved pressure helmet.. ~ .

Another object is to provide a helmet having a quickly and readily removable face panel and means for effecting a quick and sure seal between said panel and the helmet body. .··.,; ., -.

Another object of the invention-is’to provide a pres2,935,085.::

Fig. 17 is a cross-sectional view showing certain modified features of construction of the device shown in Fig. 16;

Fig· I? is a plan view of the modified structure shown in Fig. 17; and

Figs. 19-20 are cross-sectional views taken on lines 19—19 and 20—20 respectively of Fig. 16 showing further particulars as to the manner of attaching earphones.

Referring to the. drawings and more particularly to Figs. 1, 2 and 3; the helmet comprises in general a relatively flexible hood or body portion designated in its entirety as 1 to which is. secured a. relatively rigid frame 2, defining a face opening, and a face piece or panel 3 of transparent material removably secured to said frame in sealed relationship with said hood. Preferably, the hood is provided with interior padding and an exterior crash shell.

' ’J sufficiently stretchable and elastic that it may be readily expanded to a diameter large enough to pass over the head of the wearer and when in position around the wearer’s neck return to a size to lie closely adjacent the wearer’s neck. For this reason we prefer to make the neck portion of a thickness of the order of .010-.015. From an operational standpoint it may be much thinner, but if too thin it will be subject to tearing in service. Likewise a thickness greater than approximately .020 will make it exceedingly difficult to stretch over the wearer’s head. Therefore, it is important to keep the neck portion within the limits of ,005-.020 thickness. The thickness of the flap Sc and the remainder of the bladder, other than the neck portion Sb, is not so critical. We have found that entirely satisfactory results have been obtained with a neck thickness of .010.015, a thickness of flap 5c of the order of .020 and the remainder of the bladder varying from .020 thickness to .045 at the top of the head: the greater thickness at the top being due to the fact that this point corresponds to the lower end of the dipping form.

Face frame

With the bladder 5 disposed within the fabric outer cover 4 and the flap 5c of the bladder extending beyond the beaded edge of the cover 4, the frame 2 is secured to the hpod in the manner now to be described. The frame 2 is concave in side elevation (Figs. 1 and 4) and is oval in front elevation (Fig. 5) and is so shaped and proportional as to pass across the forehead and rearwardly down along the temples, forwardly and downwardly across the checks and thence below and slightly forwardly of the chin.

The frame 2 is of rigid construction, the present em- ---------------------, ........ in the shape to be more particularly described below. The frame comprises an inner section 15 which in the present embodiment is made in one piece and an outer section 16 between which and the inner section 15 the outer _-------------r— be securely clamped. To facilitate clamping, the cuter section 16 comprises an upper part 16' and a lower part 16 which are adapted to be clamped together by suitable fastening means, such as machine screws 17 and 16 is preferably along a transverse plane intersecting the frame at its maximum width. The outer section 16 : (Fig. 6) at its lower end is provided with a concave recess 16a and a rearwardly extending portion 16b joined by a offset inwardly of the frame from the portion^ 16b. The inner frame section 15 is provided with respectively corresponding and cooperating portions 15a, 15b and 15c. The upper portion of the frame (Fig. 4) is similarly and 16c are directed upwardly as well as rearwardly; These portions gradually change direction from the top of. the frame to the bottom of the frame; , the important characteristic being that in the upper part of the frame, 16' and 16, the portions 15b and 16A and the adjacent portions 15« and 16α provide an overhanging downwardly extending flange for receiving the upper part of the face piece 3, while in the lower portion of the frame more nearly in a fore and aft direction. In assembling the frame and hood the beaded edge 4c and corresponding adjacent portion of the inner lining of bladder 5 are disposed within the groove provided by the recessed porin-position as shown best in Figs. 4 and 6, with the outer and inner hood members 4 and 5 intimately disposed between the frame sections. 15 and 16, and the parts are securely assembled by means of the machine screws 16

Hood

The main portion or body of the hood 1 comprises an outer cover 4 (Fig. 4) and an inner layer or lining 5. The outer cover will be described first. The outer cover 4 is made of relatively non-elastic material, such as nylon fabric, of a thickness and weave to resist stretching and is made to conform substantially to the contour of the 25 average size head. In order to provide a smooth contour the outer cover is composed of a plurality of pieces connected together as at seams such as S. To insure a close fit, cooperating lacing strips 6 and 7 extend in spaced apart parallel relationship from the lower edge binding 30 strip 8 upwardly on one side behind the ear position and thence forwardly and upwardly across the top to the rear of the forehead and downwardly on the other side along a corresponding path, the strips 6 and 7 being secured to --------- , „ v^uuvuvu, _luc pwsent em the fabric cover, and a lace 9, preferably made of nylon, 35 bodiment being made of sheet metal suitably formed ii is. passed alternately through loops provided on the re- ....

spective strips 6 and 7. This permits the hood cover to be adjusted to snugly fit a given head. The cover at the rear is provided with a centrally disposed slit extending ... -------- ------- .... ....... _oc._uull „ _{Ulc uuler} iron about the crown point designated 10 downwardly 40 and inner members 4 and 5 of the hood 1 are adapted to through the lower hood edge 8 and suitable slide fas- ’--------------’ ~ - — teners, such as 11 (Fig. 7), are secured to the edges of the hood at the slit and are cooperatively engaged by a slide 12 for closing or opening the hood at the rear. „ ,____...„_{o 3}._1CWS n _auu

To protect the timer lining or bladder 5 a flap 13 is pro- 45 18. The juncture between the outer frame parts 16' and

It- will be seen from Figs. 1 and 5 that the outer cover 4 closely conforms to the head contour from the front zone, which follows a path across the forehead down- _________., _{ίνυ JU!UCU} uy a wardly on opposite sides across the temples and thence 50 curved section to a rearwardly extending lip portion 16c beneath the chin, so as to enclose the remainder of the offset inwardly of the frame from the portion ISA The head and neck down to the binding strip 8 at the juncture of the neck with the shoulders. The portion of the cover 4 corresponding to the chin area is designated 4α and ----.. ,_s simnany the tubular neck portion is designated 4b. At toe face 55 shaped except that the portions 15b and 16b and 15c opening the cover 4 is provided with a reinforced and --beaded edge 4c (Figs. 4 and 6) formed such for example as by securing a wire member 4d within a turned over ^;^ed^°^f.^the cover fabric. . ««uawHum, vciug uml me upper part or me irame, lhe inner layer or lining 5 conforms to the shape of 60 say down to the point of juncture of the outer frame part the outer fabric cover 4 and is preferably made of highly .. --. - - elastic material, such as latex rubber, in the form of a bladder whose entire area is impervious to air under pr^sure. The preferred manner of making this bladder .... ...... ., ... .... _lu,,_{u puiuvu UL luc llame} is by dipping. The chin portion of the bladder 5 (Fig. 65 below said juncture the corresponding flange extends 4) is designated 5α, and the tubular neck portion is desig- ’ “ .. ..

nated Sb and is sufficiently long to provide an inturned collar portion 5b’ for purposes to be hereinafter described. The face opening of the bladder is outlined by

.. . ~ ~ ^J ...uuu .u. pivvmuu υγ LUC 1CCCSSVU UUla continuous marginal flap portion 5c which extends be- 70 tion 15a and the outer sections 16' and. 16 are placed vnnri th a μαοΚα/Ι α&lt;4&lt;ύα zfx» rv£ +ha λ __i _ j . - .., , - . . ·. __ F yond the beaded edge 4c of the cover 4 and is provided with a beaded edge. The marginal flap 5c serves as a sealing flap to effect a seal between the bladder 5 and; the face piece 3 in the manner to be described hereinafter. „____.,

It is especially important that the neck portion Sb be 7# and; 17. In assembled position the. sealing flap 5c exS tends ah appreciable distance beyond the recessed portions of the frame, it being noted that the flap 5c is additionally locked in position and is given a predetermined directiori more or less in the plate of the frame by means of a lip 16d formed on the outer edge of the frame section 16 and serving -to intimately clamp the sealing lip 5c between the portions 16 J and 15α of the frame, The position of the sealing lip 5c which is thus predetermined is best seen in Fig. 2 where the face piece 3 is removed.

Face piece fastening

When it is desired to place the face piece 3 in position the upper portion corresponding to the portion 16' of the outer frame section is placed against the sealing strip 5c and is then pushed upwardly behind the downwardly and forwardly projecting flange of the frame, above referred to, and the lower end of the face piece is then pushed inwardly within the flange at the lower portion of the frame (Fig. 4) until the sealing stnp assumes the position shown in Fig. 4, from which it will be seen that the strip passes over the marginal front face of the panel 3, around its peripheral edge and downwardly to the rear of its inner face. In this position the interior of the frame surface coinciding with the portion&amp;iclosely confines the strip against the front /=.=— — ----piece 3. To assist in centering the face piece with respect to the vertical axis of the frame a guide plate 20 (Figs. 4 and 5) is secured to the frame section 16 at its upper portion and is provided with a centrally disposed slot 21 for receiving the centering pin 22 rigidly secured to the face piece 3. A quick actuating catch is provided for locking the lower portion of the face piece in position, which mechanism comprises a lug 23 (Fig. 4) rigidly secured to the outer frame section 16 and extending downwardly therefrom; and a + member 24 having a rear cross bar 25 and side arms, such as 26 whose free ends are pivotally attached as at 27 to a mounting bracket 28 suitably rigidly secured to the face piece 3, the member 24 being urged to closed posi- . tion by a suitable spring 29, the upper end of which is anchored to the bracket 28 and the lower free end of which engages the member 24. To facilitate quick release of the catch a latch string 30 secured to the cross bar member 25 is provided at its lower end with a small weight 31. To assure quick -register of the catch member 45 24 with the lug 23 a pair of laterally spaced pins 32 are rigidly secured to and extend downwardly from the -outer frame section 16, the catch member 24 being slightly tapered to guide it into latching position.

Breathing and audible means

Suitable ingress and egress to the space within the helmet is provided in the following manner. An elbow tube 33 (Fig. 5) is secured to the panel 3 in register with a hole provided therein and a suitable inhaling valve 55 (not shown) is employed for controlling the ingress and preventing egress -from the tube. The free end of the tube may be suitably attached, as by a flexible hose, to a source of oxygen under controlled pressure. An exhalation valve 33α, located to the left of tube 3-3, is 50 likewise secured to the face panel 3 in register with a hole provided therein/ A compensating tube 336 connects the two valves. . .

Suitable ear phones, designated m general as 34 and 35 (Figs. 4 and 5), and a suitable microphone, such as 85 36 may -be disposed within the helmet. Since these devices per se -are not a part of the present.invention they are merely referred to in general to indicate their ^u®^eand preferred location and mounting. Preferably the ear phones are supported from the crash pads-to be more 70 particularly described hereinafter with reference to Figs. 10 and 11. The microphone 36 (Fig. 6α) is earned on the outer end of an arm 36α whose inner end is piv10

2,085,085

15c, on the lower right hand side as viewed in Fig. 5. This mounting is so arranged that the parts do_not interfere with the sealing flap 5c of the bladder 5. The swinging arm 36α is resiliently held in speaking position by spring 36c which is fastened to the bracket 36b and has a free end which presses against a flat spot on the center hings of arm 36α. In this manner the swinging microphone may be adjusted in the correct position close to the mouth but is movable in both directions against the pressure of spring 36c; thus protecting the face of The wearer against damage in case of bumps or shocks. This mounting further permits the microphone 36 to be swung outwardly, as indicated by broken lines in Fig. 6α, so as to clear the mouth when the face panel 3 is removed. To facilitate service connections with the ear phones 34 and 35 and with the microphine 36 a jack designated generally as 37 is provided. The jack comprises a body portion 37α having a flange at its inner end a®⁰?*⁶® J® the inner frame member 15c interiorly of :the bladder 20 5. The neck of the body 37α extends outwardly through a tight fitting opening 5d provided in the bladder 5 and through a corresponding opening provided by a grommet 4g secured in the flexible covering 4. The body is held he nortion 5α closely in sealing engagement by means of a clamp collar 376. surface of the face 25 The jack 37 is suitably connected to the ear phones and surface of the _micro_Phone and is adapted to receive the input conductors all in the usual manner. This jack connection may also be used for other electrical connections where desired such as an electrical heating element (not shown).

When the device is in operative position, the lower: end of the collar portion 5b (Fig. 4) is disposed inwardly and the inwardly and upwardly turned end. is designated 5b'. When disposed in this position the intumed portion 56' is of such size and character to closely and mU^hapedroatch 35 timately seal against the neck of the wearer When P - pressure is introduced into the closed and sealed helmet the pressure is exerted between the collar portion 56 and the inwardly disposed and upwardly turned end thereof 56'-. The outer neck portion 46 of the fabric cover 4 restrains the outward expansion of the bladder neck portion 56 and the resultant force is exerted on the inturned tubular neck portion 56' to urge it mto positive sealing engagement with the neck of the wearer. pressure there is a tendency for the intumed portion 56to be urged downwardly into alignment with the outer portion 56. To maintain the parts in the desired position strips, such as 5d (Figs. 8 and 9), are disposed at spaced intervals peripherally of the collar, having their upper and lower ends secured respectively. The lower ends of the strips 5d are fastened to the inturned portion 56' somewhat below the sealing edge to avoid interference with a dependable seal. Additionally, after the helmet is in position on the wearer (Fig. 4) a restraining collar 40 of unyielding material, such as nylon, preferably is placed in position exteriorly of the. outermost part of the tubular neck 56. In this way it is npt necessary to have the outer cover at the neck, portion 46 to make such an accurate and perfect fit with the neck of the wearer and the outer portion 56 of the bladder neck is restrained by the collar 40. . , .

In the device described the panel 3 is subjected to substantial external pressure at times and for this reason the flange 15c is disposed and positioned as. shown best in Fig. 4 to reinforce the frame 2. A resilient pad 41, preferably made of latex foam, sponge rubber or the like, is disposed at the rear face of flange 15c and extends downwardly on opposite sides of the temple zones so as to rest across the forehead downwardly along the temples.

¹ Crash protection structure

In helmets of this character the wearer is often subjected to buffeting and some times to crash landings. In

2,938,968 to prevent serious damage the following provisions are made.

Supplementing the cushion 41, there is provided within the bladder 5 (Figs. 10, 11 and 4) a grid-like cushion comprising a central strip 42 which extends from adjacent the strip 41 rearwardly across the head and downwardly to a point approximately behind the wearer’s ears, a strip 43 extending laterally from the rear end of strip 42 on respectively opposite sides around the rear of the wearer’s head and terminating closely adjacent the wearer’s ears, and a transversely disposed strip 44 extending crosswise over the head and downwardly on respectively Opposite sides in substantial alignment and terminating slightly above the ears. These strips are preferably integrally formed one with the other and are relatively narrow. The grid-like cushion thus disposed is made of soft flexible material, such as foam or sponge rubber, covered with leather. For the reasons to be pointed out following, this cushion grid is built up around a metal frame or spider 38 which is embedded in the core nearer the. outer surface than the inner surface so that the major thickness of the padding is located on the underside of the spider towards the head. The spider serves to conform the grid padding to the head and serves the following additional functions. The forward end of the spider 38 is pivotally connected, as by a hinge 38α to the inner frame member 15 to thereby permit freedom of movement of the paddling grid assembly so as to allow adjustment thereof to conform to the shape of the wearer’s head without undue pressure or strain on the head. The lower ends of the spider arms embedded in the strip 44 carry adjustably secured thereto a pair of ear phone brackets, such as 386, which provide a convenient means of supporting the ear phones 34 and 35 so as to permit the desired vertical adjustment of the ear phones. It i is advantageous to have these pads within the bladder so as to avoid interference with the hood lacing and zipper. These pads are further useful in holding the bladder 5 away from the head when the bladder is not inflated, which is usually a large part of the time.

In order to more completely protect the head of the wearer the fabric outer cover 4 is preferably encased in an outer shell designated in its entirety as 39 (Figs. 1 and 7) preferably made of light stiff material, such as reinforced molded or pressed plastic. The shell 39 is preferably made in separable halves, such as 39α and 396, provided with complementary interlocking ribs by which the halves may be locked together by a curved channel strip 39c. The locking channel 39c has at its forward end a finger 39 d adapted to engage an undercut cooperating portion of the ribs of the sections 39α and 396 and at its rear end carries a latch 39e for releasably engaging a cooperating slot formed in the adjacent end of the rib portions of the sections 39α and 396. The forward margin of the shell carries a plurality of fingers, such as 39/, secured thereto for locking engagement in slots, such as 39g, provided in the rear frame section 15. The separate halves 39α and 396 are first locked at their forward margin to the frame member 15 and are thereafter brought together in a lateral direction into interfitting engagement and are locked in this position by the channel 39c.

In Fig. 12 there is diagrammatically illustrated the pressure distribution within a pressurized head enclosure of the general character described. From this it will be seen that the pressure acting outwardly is equalized in all directions except with respect to the area NA of the neck and the corresponding area UP on the top of the head. The differential in pressure between these areas results in an uplift which is appreciable. For example, assuming the average area of the neck to be 18 square inches and assuming a pressure of 3 pounds per square inch, the resultant uplight pressure will be 54 pounds. If this force is carried to the suit through the neck of the helmet secured thereto, the free movement of the wearer’s head will be considerably interfered with. '

7S

Pressure restraining means

In Figs. 13 and 14 there is shown a novel means of securing the helmet to the wearer’s suit to accommodate this uplift pressure while at the same time providing for freedom of movement of the wearer’s head. The helmet has secured to its opposite sides at limited areas fastening means designated in general as 50 and 50'. These fastening means may be attached to either the outer crash shell 39 or the fabric hood cover 4, as desired. In the present embodiment they are shown attached to the fabric hood 4. Since these are identical it will only be necessary to describe one. The fastening means 50 (Fig. 4) comprises a bracket 50α whose upper end is securely fastened to the fabric and whose lower end is provided with a ball socket 506 into which is swiveled a ball 50c from which depends a shank having a yoke 50rf in which is journaled a pulley 50e. Harness cords, preferably in the form of a bridle having a pair of downward extending front portions 51—51' and a pair of rearwardly extending portions 52—52' pass over the pulleys of fasteners 50—50'. The portions 51—51' are interconnected at the lower ends so as to provide a loop which passes over laterally spaced pulleys provided by fastening means 53—53' suitably secured to the suit designated S and constructed and arranged as above described with respect to the fastener 50. Similarly the rear cords 52—52' are provided in the form of a loop which passes through a similar pulley provided in the fastening means 54 secured to the rear of the suit. The fasteners 50—56' are disposed in vertical and lateral alignment with the pivot point of the wearer’s head. This pivot point is provided by the articulated engagement of the occipital bone of the skull with the first cervical vertebrae or “atlas” of the spine. For convenience, the portions of the helmet in lateral and vertical alignment with said pivot point will be referred to as the helmet pivotal points. It will thus be seen that by arranging the holddown harness in the manner above described, it will permit freedom of forward and rearward movement and will facilitate other movements about said pivot point. It will also be appreciated that when the head is moved from side to side, in a rotary motion, the cords of the harness are permitted to freely slip through the pulleys of the fastening means to relieve any restriction of movement by the cords, and the same is true when the head is rocked from side to side.

Modification (pressure equalized helmet)

In the modification now to be described, the device is so constructed and arranged that the pressure within the helmet is equalized to thereby eliminate the uplift force. This is diagrammatically illustrated in Fig. 15 from which it will be noted that the neck area defined as NA is equalized by corresponding and preferably identical area EA at the top of the helmet, which is free of upward pressure. In general, this is accomplished by providing a supplemental or inner bladder, designated in general as 60, which is connected to a bladder disposed within the helmet hood, generally designated as 61, in such a way as to eliminate uplift pressure in the area EA. In this modification the holddown harness is not necessary; the grid padding described more particularly with reference to Figs. 10 and 11 is omitted; and the ear phone mounting is different: otherwise the structure has much in common with the embodiment of Figs. 1-9.

Referring more particularly to Fig. 16, it will be seen that the hood 61 is secured to a rigid frame 62 defining a face opening to which is detachably secured a face panel 63 and the hood comprises an outer cover 64 and an inner layer or bladder 65, all constructed and arranged as previously described with respect to the corresponding parts 1-5, inclusive of the embodiment disclosed in Figs. 1-9. The details of construction and arrangement of parts previously disclosed in full will not here be repeated since they are identical except in the particulars noted. On the top of the hood opposite area of the neck, the outer cover 64 and bladder 65 are provided with an opening to which

2,935,985 described more particularly with reference to Figs. 19 and 20.

The ear openings in the bladder body 70 are defined by thin marginal edges 100 which seal around the root of the ear. A sponge cushion 101 surrounds these openings and is spaced outwardly from the periphery of the thin edge· 100, so as to leave the edge relatively free for sealing purposes. A metal shell 102 is securely fastened to the sponge cushion 101 and is soundproofed by an inner layer of sponge rubber 103 extending over its entire inner surface and by an outer layer 104 of similar sponge rubber material extending over its outer surface co-extensive with the flange 105 of an ear phone 106. To prevent soundboard effect and to permit free passage of air into the sound chamber the metal shell 102 is provided with a multiplicity of holes, such as 107, and with the relatively large opening 108 disposed centrally of the ear phone.

In applying the modified device (Figs. 16-20) the following procedure is desirable. The inner bladder 70, with: the ear phones attached, is first stripped over the head, and adjusted for good fit to the ears and face and with the. neck portion 71 extending downwardly in the position· indicated in Fig. 16. The outer bladder 65 fastened in the· position shown in Fig. 16, but with the fastening means; loosened to relieve entrapped air, is next stripped over the: outer bladder and head of the wearer and during this step the zipper on the rear of the outer hood casing 64 is open. The neck 65b' of the hood bladder is placed in sealing position in the manner indicated in Fig. 4. The fastening 30 means, such as 75—77, are tightened to effect intimate sealing and the hood is now ready to have the face piece 63 locked in sealed position to completely close the helmet for pressurization. An outer hood shell identical with the shell 39 (Fig. 1) is secured in an identical manner to frame 62.

It is noted that the above arrangement places the ear phones inside the helmet hood 61 so that the phones may be pressurized and an airtight seal is provided around the ears in order to subject the ears to the same pressure which the mouth and nose are subjected to.