GB2478305A

GB2478305A - Breathing mask tensioning mechanism

Info

Publication number: GB2478305A
Application number: GB201003464A
Authority: GB
Inventors: Michael John Kelly; Philip Michael Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-03-02
Filing date: 2010-03-02
Publication date: 2011-09-07
Anticipated expiration: 2030-03-02
Also published as: GB201003464D0; GB201511494D0; GB2478305B; GB2524679A; GB2524679B

Abstract

A mechanism for mounting a pilot's breathing mask 2 to a pilot's helmet comprises a rotatable member 14 rotatably mountable to a pilot's mask 2 and first and second tensile members or straps 32, 34 each having a first end and a second opposite end. The first end of at least one tensile member 32, 34 is engaged with the rotatable member 14. The opposite end of each tensile member 32, 34 configured to be coupled to an attachment point on a respective side of a pilot's helmet. The rotatable member 14 is connected to an actuator 22 to enable a pilot to rotate the rotatable member 14 to draw in the at least one tensile member 32, 34 engaged with the rotatable member 14 and thereby adjust the length of the or each strap or tensile member 32, 34 between an attached mask 2 and a pilot's helmet to adjust the tension with which the attached mask 2 is held against a pilot's face.

Description

Mask Tensioning Mechanism

Description

The present invention relates to a breathing mask or an aircrew respirator for use by pilots and, in particular, to a mechanism for mounting and tensioning a breathing mask/respirator to a pilot's flying helmet.

Pilots of modern fighter aircraft are provided with breathing masks to supply breathable gas such as air or oxygen-enriched air to them during flight. These masks normally comprise a flexible oro-nasal mask within a solid shell having an inspiratory valve supplied with oxygen or some other breathable gas and an expiratory valve to allow the pilot to expel the air from the mask on exhalation. The breathing mask is generally mounted to the pilot's flying helmet by means of a harness incorporating a releasable fitting. The pilot may alternatively be provided with a respirator which generally comprises a breathing mask as described above, but with a visor portion mounted thereto in front of the pilot's eyes, and a hood portion sealed around the perimeter of the visor and breathing mask to provide the pilot with protection from ambient surroundings should he be in a hazardous atmosphere. For the purposes of the present application, only a breathing mask' will be referred to, although it should be understood that this invention is equally applicable for use with an aircrew respirator.

In a fighter aircraft, it is essential that the breathing mask makes an airtight seal with the pilot's face at all times. If the pilot is flying at high altitude, the atmospheric pressure within the cockpit will be lower that that at ground level and so the pilot will require breathable gas to be supplied to him via the breathing mask at a higher pressure than the air of his surroundings. In addition, if a pilot is flying a modern fighter aircraft capable of executing manoeuvres which subject the pilot to excessive G-forces, he will require the breathable gas to be supplied to him at an elevated pressure by a breathing gas regulator. Breathing gas regulators ate responsive to G-forces, such that when the G-force on the pilot increases, the pressure of the gas supplied to the mask is correspondingly increased. Thus, changes in the G-forces result in automatic changes in breathing gas pressure in the terior of the mask, Therefore, in such flight situations, it is essential to maintain the integrity of the seal bet\veen the mask and the pilot's face to prevent the seal leaking when pressurised breathable gas is supplied to the mask, otherwise the pilot will not receive enough oxygen and could black out. However, during normal, low-altitude and/or cruising flight, it is not always necessary for a pilot to wear the mask and for comfort reasons, it is desirable to be able to remove the mask from the pilot's face, either by loosening of the straps so that it can hang beneath the chin, or by detaching from one side of the helmet so it can hang down at the other side of the helmet out of the way. It is also desirable for a pilot to be able to quickly and io easily re-attach the mask to his face/die helmet should the need arise. For example, a pilot may suddenly find hlmself in a combat situation and very quickly need to re-attach his mask to the correct tension on his face to be prepared for high-G manoeuvres.

To maintain the integrity of the seal between the mask and the pilot's face, the mask /5 must be held in place with sufficient tension. This tension is maintained by tensile members such as wires/cables which secure the mask to the pilot's helmet. In known mask-niounting mechanisms, a cable extends from each side of the mask to an attachment point on a respective side of die helmet. The end of one or both the cables which is secured to the helmet includes an attachment nieans to enable die or each cable to be detachably secured to the helmet. Each cable also includes a fine adjuster to enable the length of each cable to be adjusted to a required tension to hold the mask on the pilot's face with a desired force. Such fine adjusters can comprise screw-barrel adjusters.

With known mask mounting systems, it can be difficult to detach die mask from the lielniet when the mask is held on the pilot's face under the pre-set tension, or difficult to re-attach the mask to the helmet to the pre-set tension. Furthermore, under certain conditions, if a pilot is to execute maximum-G manoeuvres, it may be necessary to temporarily increase the tension with which the mask is held on his face to prevent the mask moving under such extreme forces and breaking the seal with his face. However, known mask mounting systems cannot satisfactorily allow quick and easy increase of this tension. In addition, flying for extended periods with the increased mask tension would be uncomfortable, and so it is desirable to provide a means to qckly and easily reduce the extra-tension with which the mask is held on the pilot's face, back to the previous pre-set tension suitable for the majority of flight manoeuvres.

It is therefore an object of the present invention to provide a mechanism for mounting a mask to a pilot's helmet which substantially alleviates or overcomes the problems mentioned above, and a mask incorporating such a mechanism.

Accordingly, the present invention provides a mechanism for mounting a pilot's to breathing mask to a pilot's helmet comprising A mechanism for mounting a pilot's breathing mask to a pilot's helmet comprising a rotatable member rotatably mountable to a pilot's mask and, first and second tensile members each having a first end and a second opposite end, the first end of at least one tensile member being engaged with the rotatable member and, the opposite end of each tensile /5 member configured to be coupled to an attachment point on a respective side of a pilot's helmet, wherein the rotatable member is connected to an actuator to enable a pilot to rotate the rotatable member to draw in the at least one tensile member engaged with the rotatable member and thereby adjust the length of the or each tensile member between an attached mask and a pilot's helmet to adjust the tension with which the attached mask is held against a pilot's face.

In a preferred embodiment, the first end of each tensile member is engaged with the

rotatable member.

A preferred embodiment comprises a locking mechanism to lock the rotatable member in a selected position.

Preferably, the locking mechanism is configured such that the rotatable member can be locked in a plurality of discrete positions corresponding to different extents to which the or each tensile member is drawn in.

The locking mechanism preferably comprises a ratchet and pa\\Tl mechanism.

The rotatable member is preferably rotatably mounted within a housing attachable to a pilot's mask, a saw-tooth ratchet surface is formed on an internal wall of the housing and the rotatable member includes a paw1 member engageable with the ratchet surface, The rotatable member preferably includes a biasing member to bias the pawl member against the ratchet surface.

The rotatable member is preferably rotatably mounted on a rotatable a shaft within the housing and preferably, an end of the shaft protrudes outside the housing and the actuator is a lever fixed to the protruding end of the shaft.

The shaft may include at least one cam element protruding from the shaft and configured to engage the pawl member to rotate the rotatable member upon rotation of the shaft in a first direction.

The at least one cam element may include an inclined surface configured to lift the pawl member out of engagement with the ratchet surface upon rotation of the shaft in a second direction opposite to the first direction.

The lever preferably includes a blocking means configured to block rotation of the lever in the second direction. The lever may be moveably mounted on the shaft in an axial direction thereof and, the blocking means may be configured such that rotation of the lever in the second direction is not possible until the lever is moved in an axial direction of the shaft.

The shaft may include two cam elements and the rotatable member may include two pa\vl members.

The locking mechanism may be configured such that the rotatable member can be locked in at least three different discrete positions and, in a preferred embodiment, the ratchet surface is configured such that the rotatable member can be locked in at least three different discrete positions and wherein a length of the or each tensile member drawn in when rotating the rotatable member from a first discrete position to a second discrete position is different to a length of the or each tensile member drawn in when rotating the rotatable member from the second discrete position to a third discrete position.

Alternatively, the locking mechanism may comprise clutch mechanism operable to lock the rotatable member in any selected position.

The locking means may further include a release actuator configured to unlock the rotatable member and, the rotatable member may further comprise a rotational biasing member to rotate the rotatable member in a first direction to draw in the or each tensile member.

A preferred embodiment comprises a housing attachable to a pilot's mask wherein the rotatable member is rotatably mounted within the housing. The rotatable member is preferably rotatably mounted on a shaft which is rotatably mounted within the housing. Preferably, the actuator comprises a lever fixed to the shaft.

In a preferred embodiment, the housing includes hollow guide members through which each tensile member extends from the rotatable member out of the housing.

The guide members may be rotatable relative to the housing.

In a preferred embodiment, the rotatable member comprises a spooi and the or each first end of said at least one tensile member is secured to the spooi, wherein the or each tensile member is drawn in by being wound around the spool upon rotation thereof.

In one preferred embodiment, the first end of one of the tensile members is secured to the spooi to be wound therearound and, the first end of the other tensile member is not attached to the spool.

Alternatively, the first end of both tensile members is preferably secured to the spool to enable both tensile members to be wound around the spooL In an alternative preferred embodiment, the rotatable member comprises a spur gear and the or each first end of said at least one tensile member includes a toothed rack in meshing engagement with the spur gear, wherein the or each tensile member is drawn in by rotation of the spur gear causing the or each rack to be driven past the spur gear.

In such an embodiment, the first end of one of the tensile members may include a toothed rack in meshing engagement with the spur gear and, the first end of the other tensile member may not be in engagement with the spur gear.

Alternatively, the first end of both tensile members may include a toothed rack in meshing engagement with the spur gear to enable both tensile members to be drawn in by rotation of the spur gear causing both racks to be driven past the spur gear.

A rack of a first tensile member is preferably disposed above the spur gear and the rack of the other tensile member is preferably disposed below the spur gear and in parallel with the rack of the first tensile member, such that rotation of the spur gear causes the two racks to be driven in opposite directions.

The or each rack is preferably slidably held within the housing.

A preferred embodiment further comprises hollow guide members through which each tensile member extends from the rotatable member toward the respective side of the pilot's helmet.

Preferably, the tensile members comprise inextensible cables.

In a preferred embodiment, each tensile member includes a screw barrel adjuster operable to fine-adjust the distance between a pilot's helmet and the mask on each tensile member independently The present invention also provides a pilot's breathing mask comprising a mechanism for mounting the mask to a pilot's helmet as described above.

The pilot's breathing mask preferably includes the actuator as the front-most element of the mask.

Preferred embodiments of the present invention will now be described, by way of to example only, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view of a mask incorporating a mounting and tensioning mechanism of the invention; Figure 2 shows an exploded view of the mask of Figure 1; /5 Figure 3 shows an enlarged view of the mounting and tensioning mechanism of Figures 1 and 2; Figure 4 shows an enlarged view of the spooi and locking means of the mounting and tensioning mechanism of Figures 1 -3; Figure 5 is a schematic front view of the mounting and tensioning mechanism of Figures 1 -4 showing three discrete positions of the actuator lever; Figure 6 is a cross-sectional of view of the mounting and tensioning mechanism taken along the line X-X of Figure 1, with the mechanism in a first, locked, position; Figure 7 is a cross-sectional of view of the mounting and tensioning mechanism taken along the line X-X of Figure 1, with the mechanism in a second, unlocked, position; Figure 8 is an enlarged view of a spur gear, racks and locking means of a mounting and tensioning mechanism according to another embodiment of the invention; Figure 9 is an enlarged view of the spool and locking means of a mounting and tensioning mechanism of yet another embodiment of the invention; and Figure 10 is an enlarged view of a spur gear, rack and locking means of a mounting and o tensioning mechanism according to yet another embodiment of the invention.

Figure 1 shows a pilot's breathing mask I incluthng a mask mounting and tensioning mechanism 10 according to a first embodiment the present invention. Only a rigid outer shell 2 of the mask 1 is shown, and a flexible oro-nasal portion which would contact the pilot's face in use, has been omitted.

The mask of Figure 1 is shown in Figure 2 with the mechanism 10 in an exploded view to illustrate the internal features. It can be seen that the mounting and tensioning mechanism 10 comprises a front plate 12a and a rear plate 12b, together defining a housing 12. A spool 14 is rotatably mounted on a shaft 16 which is itself rotatably supported within the housing 12 with a first end 16a extending through an aperture 18 in the front plate 12a and with an opposite, second end 16b located in a recess 20 in the rear plate 12b. An actuator in the form of a lever 22 is secured to the first end 16a of the shaft 16. It can he seen that the first end 16a of the shaft 16 is square in cross-section and the lever 22 includes a corresponding square recess (not shown) to receive the square end of the shaft 16 such that the lever 22 is not rotatable relative to the shaft 16 and that rotation of the lever 22 causes rotation of the shaft 16. The lever 22 is held on the shaft 16 by a securing bolt 24, Two cable guides 26 are held between the front and rear plates 12a, 12b of the housing 12, one on each side thereof. The cable guides 26 comprise hollow tubes with a bend formed approximate their mid-point and an outwardly-extending flange 28 formed at one end. Each cable guide 26 is held within correspondingly-shaped channels 30a, 3Db formed in the front and rear plates 12a, 12b respectively which, together, form a closed cylindrical aperture to enclose the cable guides 26. The flange 28 of each cable guide 26 is located within the housing at the inner edge of each channel 30a, 3Db and so prevents the cable guides from sliding Out of the assembled housing 12. The closed cylindrical aperture formed by the channels 30a, 3Db is preferably slightly larger in diameter than the outer diameter of the tubular cable guides 26 such that the cable guides are rotatable about the axis of the closed cylindrical aperture.

i pati of tensile members 32, 34 in the form of inextensible cables, extends into the housing 12, one through each cable guide 26. Each cable (comprising left-side cable 32 and right-side cable 34 has a first end 32a, 34a located within the housing and secured to the spool 14 and, an opposite, second end 32b, 34b coupled to an adjustable barrel adjuster 36 to enable the second end 32b, 34b of each cable 32, 34 to be coupled to a corresponding attachment point (not shown) on each side of a pilot's helmet.

The spooi 14 includes a circumferential groove 38 around its perimeter edge face to receive each cable 32, 34 when wound around the spool 14. The left-side cable 32 extends into the housing 12 from its respective cable guide 26, around the underside of the spooi 14, is partially wound around the spool 14 within the groove 38 and its first end 32a is secured withui a fnst slot 14a which is formed in the pool 14 in communication with the groove 38. The right-side cable 34 extends into the housing 12 from its respective cable guide 26, is so partially wound around the spool 14 withui the groove 38 and has its first end 34a secured within a second slot 14b which is formed in the spooi 14 in communication with the groove 38, further around the circumference of the spooi 14. The right-side cable 34 also passes over a guide roller 40 which is rotatably mounted in the housing on a pin 42 held between the front and rear plates 12a, 12b, which enables the right-side cable 34 to be directed around the spool 14 without rubbing on the inner edge of the cable guide 26, as would occur in the absence of the guide roller 40.

Each barrel adjuster 36 comprises a first portion 36a threadingly received within a second portion 36b. The second portion 36b is rotatably coupled to the second end 32b/34b of the respective cable 32/34 and includes a ridged portion 36c to facifitate a user rotating the second portion 36b. The remote end 36d of the first portion 36a is configured to be releasably coupled to a corresponding attachment point (not shown) on each side of a pilot's helmet. It will be appreciated that rotation of the second portion 36b relative to the first portion 36a will unscrew the first portion 36a into or out of the second portion 36b, thereby altering the distance between the second end 32b/34b of the respective cable 32/34 and the remote end 36d of the first portion 36a, thereby enabling fine adjustment of the cable tension bet\veen the mask 1 and the o pilot's huimet. This enables the pilot to accurately adjust and pre-set the force \vith which the mask I is held on his face. Also, being able to separately adjust each left and -10 -right barrel adjuster 36 allows the pilot to accurately set the left/right balance of tension so that the mask 1 is held in exactly the desired position and tension on his face.

The spool 14 includes a locking mechanism which is shown in greater detail in Figures 3, 4, 6 and 7 and includes a pair of diametrically-opposed rectangular holes 44 extending though the spool 14 in an axial direction thereof, radially displaced from the central rotational axis of the spooi 14. A pawl member 46 is disposed in each hole 44 and retained in place by a dual ended flat spring 48. The flat spring 48 is generally U, shaped and is secured to the spool 14 by a screw 50 extending though the mid-point of the flat spring 48 intermediate its remote ends 48a. Each remote end 48a of the flat spring 48 is disposed over one of the holes 44 and thereby biases the respective pawl member 46 in an axial direction of the spool 14 towards the rear plate 12b of the housing 12. Each pawl member 46 includes a first end 46a in contact with a respective remote end 48a of the flat spring, a second, opposite end 46b and, a notch 46c formed at the second end to create a step 46d between the first and second ends 46a, 46b of each pawl member 46.

The second end 16b of the shaft 16 is provided with a plurality of cam elements 52 extending in a radial direction of the shaft 16. Each cam element 52 is approximately triangular in cross-section and includes an inclined surface 52a inclined with respect to the axis of the shaft 16, and a vertical surface 52b which extends in a plane parallel to the axis of the shaft 16. Each cam clement 52 also includes a thin edge 52c at the opposite side to the vertical surface 52b where the inclined surface 52a tapers down to its narrowest point.

The inner surface of the rear plate l2b includes a circular groove 54 around the recess 20, the groove 54 having a bottom surface configured in a saw-tooth' shape as a series of ramps ending in vertical walls, thereby forming a series of ratchet surfaces 56. The groove 54/ratchet surfaces 56 arc positioned such that the second ends 46b of the pawl members 46 locate in the groove 54 on the ratchet surfaces 56 and arc biased theieagainst by the flat spring 48.

A torsion spring 58 is provided at the second end 1 6b of the shaft 16 to provide a clockwise rotational biasing force on the shaft 16 in the direction shown by arrow A in Figure 4. The front and rear plates 12a, 12b are held together, also holding the various components of the tensioning mechanism 10 described above in place within the housing 12, by a number of securing bolts 60 which extend through apertures 62 in the front and rear plates 12a, 12b and are located in corresponding threaded apertures 64 in the front of the rigid outer shell 2 of the mask 1 and tightened therein.

The locking mechanism described above is operable to lock the spooi 14 in a plurality of different positions with the cables 32, 34 wound around the spooi 14 to differing extents. In the embodiment shown, the mask tensioning mechanism is operable to set thetables 32, 34 to three pre-set positions. In the loosest position, the cables 32, 34 are unwound from around the spooi to the greatest extent of the three positions whilst still being attached to the spool 14. To move from the loosest position to the next pre-set position, the lever 22 is rotated clockwise in the direction of arrow B in Figures 1 and 5 so that it moves to the vertically upright position shown as position II' in Figure 5, By moving the lever to this position, the shaft 16 is also rotated clockwise in the direction of arrow B'. As the shaft 16 rotates, the vertical faces 52b of the cam elements 52 abut against the paw1 members 46 and thereby push the spool 14 to rotate clockwise. As the spool 14 rotates, the cables 32, 34 are wound around the spool 14 and pulled though the cable guides 26. Also as the cam elements 52 push the pawl members 46, the second face 46b of each cam member travels round the groove 54 and rides up a respective ratchet surface 56, thereby deflecting the respective remote end 48a of the flat spring 48 against its biasing force.

The length of each ratchet surface 56 is configured such that as the lever 22 reaches the vertical position II' shown in Figure 5, each paw1 member 46 reaches and just edges past the top edge of the respective ratchet surface 56 and clicks over the vertical wall portion to the bottom of the next ratchet surface 56. Each pawl member 46 is biased against the bottom of the next ratchet surface 56 by the flat spring 48. Furthermore, the tension in the cables 32, 34 acting to pull the spool 14 in the unwinding direction biases the pawl members 46 against the vertical walls of the respective previous ratchet surface -12 - 56. It will be appreciated then that the pawl members 46 locked against the vertical wall portions of the ratchet surfaces 56 prevent the spool 14 from unwinding and so lock the cables 32, 34 in the pre-set position corresponding to position II' of the lever 22.

Any play in the lever 22/shaft 16 once in the second pre-set position, is taken up by the torsion spring 58 biasing the shaft 16 and associated cam elements 52 against the paw! members 46. The biasing force of the torsion spring 58 is not sufficient to wind the spool 14 any further, only to eliminate loose play in the shaft 16/lever 22.

To move from the intermediate tightness pre-set position corresponding to position II' of the lever 22 to the third pre-set (and tightest) position, the lever 22 is rotated clockwise in the direction of arro\v B in Figure 1 so that it moves to the angled position shown as position III' in Figure 5. The above-described process of the cam elements 52 pushing the pawl members 46 and thereby rotating the spool 14 is repeated, further winding the cables 32, 34 around the spool 14 and pulling them though the cable guides 26, until the pawl members 46 ride over the top of the next ratchet surface 56 and locate against the vertical wail thereof as described above.

In order to release the tension and unwind the cables 32, 34 from the spool, the lever 22 is rotated anti-clockwise in the direction of arrow C in Figures 1 and 5 so that it moves back to the angled position shown as position II' in Figure 5. In doing this, the shaft 16 is also rotated anti-clockwise and the thin edge 52c of each cam element 52 locates underneath the step 46d of the adjacent respective pawl member 46. This point of the movement is shown in the cross-sectional view of Figure 6. The spool 14 is still locked in position at this stage with the second end 46b of the pawl members 46 located on the ratchet surfaces 56 but it can be seen that the inclined surface 52a of the cam element 52 visible in Figure 6 is just located underneath and against the step 46d of the pawl member 46. It can also been seen from Figure 6 that the remote end 48a of the flat spring 48 is undeflected and fully locating the pawl member 46 in the direction against the rear plate 12b.

AS the shaft 16 rotates, the step 46d of each paw! member 46 is made to ride up the inclined surface 52a of the respective cam element 52 and so each pawl member 46 is 13 -lifted out of engagement \Vith the respective ratchet surface 56 against the biasing force of the flat spring 48. This position of the movement is shown in the cross-sectional view of Figure 7. Here, the spool 14 is not locked in position as it can be seen that the step 46d of the paw1 member 46 has ridden up the inclined surface 52a of the cam element 52 and thereby lifter the second end of the pawl member 46 out of the circular groove 54 and thereby out of engagement with the ratchet surface 56. It can also be seen from Figure 7 that that the remote end 48a of the flat spring 48 has been deflected away from the spooi 14 by this movement of the cam element 52 and pawl member 46.

It will be appreciated that the hatched end face of the can element 52 appears larger in Figure 7 than in Figure 6 because, in Figure 6, a portion of the cam element 52 is rotated out of the cross-section.

Once each pawl member 46 is out of engagement with the respective ratchet surface 56, the spool 14 is free to rotate on the shaft 16 and so, under the tension of the cables 32, 34, rotates anti-clockwise in the unwinding direction. This rotation of the spooi 14 moves the associated pawl members 46 away from the cam elements 52 on the shaft 16 and so under the biasing force of the flat spring 48, the pawl members 46 are sprung back towards the rear plate 12b of the housing 12 and into contact with the adjacent ratchet surface 56. The spool 14 will continue to rotate anticlockwise and the pawl members 46 will ride down the respective ratchet surface 56 until the pawl members 56 reach the bottom of the respective ratchet surface 56 and abut the end vertical wall of the next ratchet surface 56. The spooi 14 is then held in that position and the lever 22, under the biasing force of the torsion spring 58, is held in position II' with the vertical face 52b of each cam element 52 against the adjacent pawl-member 46. The spooi is thereby returned to the intermediate tightness pie-set position.

In order to release the tension further to unwind the cables 32, 34 from the spool into the loosest position, the lever 22 is further rotated anti-clockwise in the direction of arrow C in Figures 1 and 5 so that it moves back to the angled position shown as position i' in Figure 5. The above-described process of the step 46d of each paw! member 46 tiding up the inclined surface 52a of the respective cam clement 52, releasing each pawl member 46 from engagement with the respective ratchet surface 56, rotation of the spool 14 undet the tension of the cables 32, 34 until the pawl members 56 reach the bottom of the respective ratchet surface 56, is repeated. The spooi 14 is then held in the loosest pre-set tension position and the lever, under the biasing force of the torsion spring 58, is held in position I' with the vertical face 52b of each cam element 52 against the adjacent pawl-member 46. It can be seen from Figure 5 that the outer surface of the front plate I 2a includes projecting stops 66 against which the lever 22 abuts in positions I and III and which thereby define the limits of rotation of the lever 22.

Operation of a mask 1 comprising the mounting and tensioning mechanism 10 of the invention described above, will now be described. A pilot first dons a helmet places the mask 1 over his nose and mouth and connects the remote end 36d of each barrel adjuster 36 into the respective attachment point on the sides of the helmet. He then moves the lever 22 to position II' to reel in the cables 32, 34 and lock the spool 14 as described above in the intermediate pre-set position, which would correspond to normal flight mask tightness. The pilot then uses the barrel adjusters 36 to adjust the length of each cable 32, 34 between the mask and the helmet so that the mask is correctly balanced and tensipned on the pilot's face for normal flight use. The cable guides 26 being rotatable in the channels 30a, 30b in the housing 12 allows the mask to pivot about the axis of the portions of the cable guides 26 held in the channels 30a, 30b to achieve the best mask seating on the pilot's face. The pilot is then ready for flight using the mask I If the pilot does not wish to use the mask at that time, he can move the lever 22 to position I' which would correspond to a loose' setting, which will release the spool 14 and allow the cables 32, 34 to be unwound therefrom by a pre-determined length (dictated by the length of the ratchet surfaces 56 between position II' and position thereby dictating by how much the spool 14 rotates in the unwinding direction bet\veen these two positions). The additional slack in the cables 32, 34 which would be caused by this loosening would allow the pilot to detach one barrel adjuster 36 from the attachment point on one side of the helmet and allow the mask to hang down on the other side of the helmet from the one remaining attached cable 32/34. It is preferable to provide this loose pre-set setting position I' so that that pilot doesn't have to struggle to overcome the tension in the cables 32, 34 which is present in the normal flight position <II' when detaching a barrel adjuster 36. Without this loose setting position I', it would be mote difficult to detach one of the barrel adjusters 36 from the attachment point on the helmet. Furthermore, although the loose setting position I' allows the pilot to detach one of the cables 32/34 from the helmet so that the mask can be removed from his face, it is also envisaged within the scope of the invention that the mechanism 10 may be configured such that when moving the lever 22 to the loose setting position I', the length of cables 32, 34 unwound from the spool 14 may be sufficient for the pilot to be able to move the mask to under his chin and off his face without having to detach one of the barrel adjusters 36 from the helmet.

If the pilot needs to use his mask 1, he can quicidy and easily re-attach it and tension it single-handedly. He simply needs to hold the detached barrel adjuster with one hand, pull it towards the attachment point on the side of the helmet (thereby placing and holding the mask in position over his nose and mouth) and couple the barrel adjuster 36 into the attachment point. With the one same hand, he can then move the lever 22 to position II to reel in the cables 32, 34 around the spool 14 as described above so that the mask is held on his face in the precise tension requited for normal flight, that he set previously using the t\vo barrel adjusters 36.

If during normal flight, the pilot suddenly finds himself in a situation where he is required to make high-G manoeuvres, such as a combat situation, he can quickly and single-handedly increase the tension with which the mask i is held against his face by moving the lever 22 from the normal flight position lI to III' which corresponds to an increased tightness position. As described above, this rotates the spool 14 to further reel in the cables 32, 34 and the spooi 14 is then locked in this tight position. Once there is no longer the requirement for increased tension of the mask on the pilot's face, he can move the lever 22 to position II' which will release the spool 14 from the locked position and it will unwind the cables 32, 34 by a predetermined amount (dictated by the length of the ratchet surfaces 56 between position III' and position JI', thereby dictating by how much the spooi 14 rotates in the unwinding direction between these two positions) until the spool 14 reaches the pre-set position for normal flight and the mask is held against his face with this reduced pre-set tension. -16-

It will be appreciated that the essence of this first embodiment of the present invention is to provide a spool arrangement on the front of a pilot's mask to reel in and reel out again, the hein1et attachment wires/cables to adjust the tension with which the mask is held on the pilot's face. The exemplary first embodiment shown and described in Figures 1 -7 includes a locking mechanism which defines three discrete lock positions for the spooi 14. The amount by which the cables 32, 34 are reeled in when the spool is rotated from the first (loose) position corresponding to position I' of the lever 22 to the second (normal) position corresponding to position II' of the lever 22 can equal the length of the cables 32, 34 \vhich is reeled in when the spool is rotated from the second position corresponding to position II' of the lever 22 to the third (tight position corresponding to position III' of the lever 22. Alternatively, the amount by which the cables 32, 34 are reeled in when the spool is rotated from the first loose' position I' of the lever 22 to the second normal' position JJ of the lever 22 may differ to the length of the cables 32, 34 winch is reeled in when the spool is rotated from the second normal' position II' to the thd tight' position III' of the lever 22. In a preferred embodiment of the invention, the length of cables 32, 34 wound/unwound from the spool 14 when adjusting the mechanism 10 beveen the loose' position and the normal' position is around 10mm, and the length of cables 32, 34 wound/unwound from the spool 14 \vhen adjusting the mechanism 10 beveen the normal' position and the tight' position is around 5mm, although the invention is not limited to such specific dimensions.

An alternative embodiment of a mask tensioning mechanism of the invention is shown in the enlarged exploded view of Figure 8. In this alternative embodiment of the invention, like features from the first embodiment share the same reference numerals, and the invention includes a housing 12 comprising a front plate 12a and a rear plate 12b, a rotatable shaft 16, cable guides 26 to guide respective left and right cables 32, 34, a torsion spring 58 to bias the shaft to reduce slack therein. Also, pawl members 46 are provided biased against a ratchet surface 56 formed on the rear plate 12b by a flat spring 48. However, it can be seen from Figure 8 that the spool 14 of the first embodiment is not present and instead is replaced by a spur gear 114. As with the spool -17 - 14, the spur gear includes holes 144 therethrough in which the pawl members 46 ate slidably received. However, the first ends of the cables 32, 34 are not secured to the spur gear 114 to be wound therearound, but instead, each cable 32, 34 includes a toothed rack 132a, 134a which is in meshing engagement with the teeth 3a of the spur gear. The racks (which comprise a lower rack 132a and an upper rack 134a) are slidably mounted within channels (not shown) formed in the front and rear plates 12a, 12b of the housing 12. It will be appreciated that as the spur gear 114 is rotated clockwise, the lower rack is driven in the direction of arrow D, thereby pulling the first cable 32 through its cable guide 26. Simultaneously, as the spur gear 114 rotates, the upper rack io 134a will be driven in the direction of arrow H, thereby pulling the second cable 34 through its cable guide 26, In order that the cables 32, 34 are guided around the spur gear 114 so they can be pulled linearly in the direction of arrows D and H respectively, a number of additional guide rollers @ot shown) may be provided within the housing 12 similar to the single guide roller 40 supported on the pin 42 described above with respect to the first embodiment of the invention.

The locking mechanism incorporated in the alternative embodiment of the invention shown in Figure 8 includes all of the same features of the locking mechanism shown in Figures 2 -4 and 6 -7. Accordingly, operation of the locking mechanism of the alternative embodiment of the invention shown in Figure 8 is the same as already described and so a detailed description of the features and function will not be repeated. However, it will be appreciated that when the locking mechanism releases the spur gear 114, the lower and upper racks 132a, 134a are free to slide within the housing 12 in the direction opposite to arrows ID and E respectively, thereby releasing the tension in the cables 32, 34.

As mentioned previously, it is intended within the scope of the invention that the locking mechanism may be configured such that when the spool 14/spur gear 114 is allowed to rotate to the loose position, the cables 32, 34 may be unwound/released by such a length that is sufficient to enable the pilot to slide the mask down off his face and rest under his chin, without the need to disconnect either of the barrel adjusters 36 from the helmet. In such an embodiment, the length of cables 32, 34 \vhich would need -18 -to unwind from the spool 14/be released past the spur gear 114 to allow this to be performed would be significantly greater than the length of cables 32, 34 which can be wound around the spooi 14/driven past the spur gear 114 when increasing th tension with which the mask is held on the pilot's face from the normal' position to the tight' positIon.

The above-described embodiments of the invention comprises three discrete positions of the spool 14/spur gear 114 corresponding to three different lengths of cable 32, 34 between the mask and helmet and thereby thtee different tension configurations of the mask on the pilot's face. However, the invention is not intended to be limited to only three different tension settings, and the locking mechanism could be configured to include only two or more than three different tension settings. For example, the locking mechanism could include a greater number of individual teeth' of the saw-tooth' ratchet surface ramps, each of a smaller length, so as to allow a greater number of discrete tension settings and thereby finer control over the tension with which the mask is held on the pilot's face. In an embodiment where the mask is intended to be able to be moved off the pilot's face without the need to disconnect either of the barrel adjusters 36 (as described above), it is also intended within the scope of the invention that the locking mechanism may be configured such that there is a further loose position whereby the cables 32, 34 are unwound from the spool 14/released from the spur gear 114 by a length which is long enough to allow such mask removal to occur.

In addition to the spool/spur gear locking mechanism described above, in an embodiment \vhere the mask can be moved off the pilot's face without the need to disconnect either of the barrel adjusters 36, the mask attachment and tensioning mechanism of the invention may include a separate spool/spur gear release actuator, such as a push button, and a torsion or coil spring connected to the spool/spur gear and configured to wind the spool/spur gear in the cable-tensioning direction. In use, a pilot could remove the mask from his face by pressing the release button which would operate the locking mechanism to unlock the spool/spur gear, and he could singlc_ handedly pull the mask from his face, unwinding the cables against the force of the biasing spring. He could then let go of the release button which would allow the -19 -locking mechanism to lock the spool/spur gear in the fully unwound state, allowing the mask to hang down under his chin with both barrel adjusters remaining coupled to the helmet. To don the mask again, the pilot could single handedly place the mask on his face and press the release button. This would operate the locking mechanism to unlock the spool/spur gear and allow the torsion spring to rotate the spool/spur gear in the cable-tensioning direction to take up the slack in the cables. It would be preferable that the torsion spring in such an embodiment would have a biasing force sufficient to wind the spool/spur gear to at least the first, loose, pre-set tension position so that the locking mechanism engages and locks the spool/spur gear in that position so that further tensioning of the mask can be performed as described above. It would thus be preferable that the torsion spring is not sufficiently strong to wind the spool/spur gear into the tightest setting of the spool/spur gear. In such an embodiment, the locking mechanism could also be configured such that movement of the lever in the anti-clockwise direction could provide the spool/spur gear release function described above to allow the pilot to pull the mask off his face with one hand.

In the embodiments of the invention described above and shown in Figures 1 -8, the mask is tightened by moving the lever 22 clockwise and loosened by moving the lever 22 anti-clockwise. However, it is intended within the scope of the invention that the lever 22 or locking mechanism may be configured with a blocking means such that the lever cannot be moved anti-clockwise without also performing an additional action. For example, the lever of locking mechanism may include a further ratchet or other locking mechanism which prevents the lever moving anti-clockwise until a lever-release button is pressed or, for example, the lever 22 is pulled out away from the mask. In such an embodiment, the lever 22 could be slidably mounted on the first end 1 6a of the shaft 16 and biased against the front plate 12a. The outer surface of the front plate 12a could include a number of ratchet teeth corresponding to the pre-set tension positions.

Therefore, the lever 22 would tide over the ratchet teeth and click into the next tighter position when tensioning the mask, but would need to be pulled away from the front 3o plate 12a out of engagement with the ratchet teeth to move the lever 22 anti-clockwise to loosen the mask. Such a mechanism would he provided to prevent inadvertent operation of the lever to loosen the mask, as a safety feature. It will be appreciated that if a pilot accidentally knocked the lever duting a combat situation and the mask loosened and the pilot lost the pressurised breathing gas supply, the pilot could lose consciousness with potentially fatal consequences.

The embodiments of the invention shown and described above all comprise two cables being adjusted by a rotatable member -i.e. a spooi or a /spur gear, either by being wound around the spool or by a toothed rack being driven by the spur gear, each cable puffing equally on either side of the pilot's mask. However, it is intended within the scope of the invention that the mask-tensioning function may also be achieved by only /0 providing one of the cables with a tensioning adjusting facility using the spool/spur mechanism described above, whilst the cable on the othet side of the mask remains fixed to the mask or, for example, to the housing or to the (rotatable) cable guide. Such alternative embodiments of the invention are shown in Figures 9 and 10. Figure 9 shows a further alternative embodiment of die invention similar to the spool /5 arrangement shown in Figures 1 -7, except that only one of the cables is secured to ±e spool to be wound therearound. Similarly, Figure 10 shows a yet further alternative embodiment of the invention similar to the spur gear arrangement shown in Figure 8, except that only one of the cables includes a toothed rack in meshing engagement with the spur gear to enable the cable to be driven and tensioned by rotation of the spur gear.

In both of die further alternative embodiments of the invention shown in Figures 9 and 10, it would be intended that both cables would still include barrel adjusters so that a pilot can fine adjust the length of each cable for a precise normal' flying position.

However, when using the mask-tensioning mechanism to set the mask tension to the loose' position, it will be appreciated that as only one cable is controlled by the spool/spur gear, the mask \vffi loosen on one side. The mask could then be slid off the pilot's face if the mask tensioning mechanising was configured to provide sufficient slack in the cable to allow this to occur. Alternatively, the pilot could detach one of the cables from the helmet to allow die mask to hang down on the other side of the helmet.

In this arrangement, it would be convenient for the pilot to detach die cable that has been loosened by the spool/spur gear as that side of the mask would have pivoted away from his face. Also, the donning process would then be done in a \vrapping' motion as the one loose side wire is reattached to the helmet, the side of the mask on the other fixed wire side would be held tighter against the pilot's face, and then the actuating of the lever would pull in the one adjustable cable to pull in the one loose side of the mask against the pilot's face.

The various exemplary embodiments described above include a locking means whereby the spool/spur gear is lockable in a plurality of discrete positions with the cables wound around the spool/driven by the spur gear to differing extents. However, it is intended within the scope of the invention that an alternative locking means may be provided which utilises a clutch-arrangement such that the spool/spur gear may be locked in any desired tension position within a given range of rotation, thus providing a continuous range of tension settings rather than discrete number of tension settings.

In the various embodiments described above, the tensile members are described as being wires or cables. Preferably, they are steel wires or multi-strand steel cables.

However, other suitable materials may be used provided they are substantially inextensible so that when wound around the spool/driven by the /spur gear, the tension of the mask on the pilot's face increases by the destied amount. -22

Claims

Claims 1. A mechanism for mounting a pilot's breathing mask to a pilot's helmet comprising a rotatable member rotatably mountable to a pilot's mask and, first and second tensile members each having a first end and a second opposite end, the first end of at least one tensile member being engaged with the rotatable member and, the opposite end of each tensile member configured to be coupled to an attachment point on a respective side of a pilot's helmet, wherein the rotatable member is connected to an actuator to enable a pilot to rotate the /0 rotatable member to draw in the at least one tensile member engaged with the rotatable member and thereby adjust the length of the or each tensile member between an attached mask and a pilot's helmet to adjust the tension with which the attached mask is held against a pilot's face.

/5
2. A mechanism according to claim I wherein the first end of each tensile member is engaged with the rotatable member.
3. A mechanism according to claim 1 or claim 2 further comprising a locking mechanism to lock the rotatable member in a selected position.
4. A mechanism according to claim 3 wherein the locking mechanism is configured such that the rotatable member can be locked in a plurality of discrete positions corresponding to different extents to which the or each tensile member is drawn in.
5. A mechanism according to claim 3 or claim 4 wherein the locking mechanism comprises a ratchet and pawl mechanism.
6. A mechanism according to claim 5 wherein the rotatable member is rotatably mounted within a housing attachable to a pilot's mask, a saw-tooth ratchet surface is formed on an internal wall of the housing and the rotatable member includes a paw1 member engageable with the ratchet surface.
7. A mechanism according to claim 6 wherein the rotatable member includes a biasing member to bias the pawl member against the ratchet surface.
8. A mechanism according to claims 6 or claim 7, wherein the rotatable member rotatably mounted on a rotatable a shaft within the housing.
9. A mechanism according to claim 8 wherein an end of the shaft protrudes outside the housing and the actuator is a lever fixed to the protruding end of the shaft
10. A mechanism according to claim 8 or c-kim 9 wherein the shaft includes at least one cam element protruding from the shaft and configured to engage the pawl member to rotate the rotatable member upon rotation of the shaft in a first direction.
11. A mechanism according to claim 10 wherein the at least one cam element includes an inclined surface configured to lift the pawl member out of engagement with the ratchet surface upon rotation of the shaft in a second direction opposite to the first direction.
12. A mechanism according to claim 11 wherein the lever includes a blocking means configured to block rotation of the lever in the second direction.
13. A mechanism according to claim 12 wherein the lever is moveably mounted on the shaft in an axial direction thereof and, the blocking means is configured such that rotation of the lever in the second direction is not possible until the lever is moved in an axial direction of the shaft.
14. A mechanism according to any of claims 10 to 13 wherein the shaft includes two cam elements.
15. A mechanism according to any of claims 6-14 wherein the rotatable member includes two pawl members. -24-16. A mechanism according to any of claims 4 15 wherein the locking mechanism is configured such that the rotatable member can be locked in at least three different discrete positions.17. A mechanism according to any of claims 6 -15 wherein the ratchet surface is configured such that the rotatable member can be locked in at least three different discrete positions and wherein a length of the or each tensile member drawn in when rotating the rotatable member from a first discrete position to a second discrete position is different to a length of the or each tensile member /0 drawn in when rotating the rotatable member from the second discrete position to a third discrete position.18. A mechanism according to claim 3 wherein the locking mechanism comprises a clutch mechanism operable to lock the rotatable member in any selected /5 position.19. A mechanism according to any of claims 3 -18 wherein the locking means further includes a release actuator configured to unlock the rotatable member and, the rotatable member further comprises a rotational biasing member to rotate the rotatable member in a first direction to draw in the or each tensile member.20. A mechanism according to any preceding claim further comprising a housing attachable to a pilot's mask wherein the rotatable member is rotatably mounted within the housing.21. A mechanism according to claim 20 wherein the rotatable member is rotatably mounted on a shaft \vhich is rotatably mounted within the housing.22. A mechanism according to claim 21 wherein the actuator comprises a lever fixed to the shaft.23. A mechanism according to any of claims 20-22 wherein the housing includes hollow guide members through which each tensile member extends from the rotatable member out of the housing.24. A mechanism according to claim 23 wherein the guide members are rotatable relative to the housing.C25. A mechanism according to any preceding claim wherein the rotatable member comprises a spool and the or each first end of said at least one tensile member is secured to the spool, wherein the or each tensile member is drawn in by being wound around the spool upon rotation thereof.26. A mechanism according to claim 25 wherein the first end of one of the tensile members is secured to the spool to be wound therearound and, the first end of the other tensile member is not attached to the spool.27. A mechanism according to claim 25 wherein the first end of both tensile members is secured to the spool to enable both tensile members to be wound around the spooL 28. A mechanism according to any of claims 1 to 24 wherein the rotatable member comprises a spur gear and the or each first end of said at least one tensile member includes a toothed rack in meshing engagement with the spur gear, wherein the or each tensile member is drawn in by rotation of the spur gear can sing the or each rack to be driven past the spur gear.29. A mechanism according to claim 28 wherein the first end of one of the tensile members includes a toothed rack in meshing engagement with the spur gear and, the first end of the other tensile member is not in engagement with the spur gear.30. A mechanism according to claim 28 wherein the first end of both tensile members includes a toothed rack in meshing engagement with the spur gear to -26 -enable both tensile members to be drawn in by rotation of the spur gear causing both racks to be driven past the spur gear.31. A mechanism according to claim 30 wherein a rack of a first tensile member is disposed above the spur gear and the rack of the other tensile member is disposed below the spur gear and in parallel with the rack of the first tensile member, such that rotation of the spur gear causes the two racks to be driven in opposite directions./0 32. A mechanism according to any of claims 28 to 31 when dependent on any of claims 6 to 15, 17 or 20 to 24, wherein the or each rack is slidably held within the housing.33. A mechanism according to any preceding claim further comprising hollow guide members through which each tensile member extends from the rotatable member toward the respective side of the pilot's helmet.34. A mechanism according to any preceding claim wherein the tensile members comprise inextensible cables.35. A mechanism according to any preceding claim wherein each tensile member includes a screw barrel adjuster operable to fine-adjust the distance between a pilot's helmet and the mask on each tensile member independently.36. A pilot's breathing mask comprising a mechanism for mounting the mask to a pilot's helmet according to any preceding claim.37. A pilot's breathing mask according to claim 36 \vherein the actuator is the front-most element of the mask.38. A mechanism substantially as hereinbefore described with reference to the accotTnpaflyiflg drawings.-27 - 39. A pilot's breathing mask substantially as hereinbefore described with reference to the accompanying drawings.