The present invention relates to an adjustable harness for use with self-contained breathing apparatus (SCBA) having an improved body length adjusting system.

SCBAs are generally used by emergency services personnel when they enter an environment which has reduced or no safe breathable air, such as the scene of a fire or a gas leak. SCBA harnesses generally comprise a back plate, a pair of shoulder straps and a waist belt. The back plate is provided with a first stage pressure reduction valve towards the lower end and a retaining strap. In use, a cylinder of breathable gas is attached to the first stage pressure reduction valve and is secured to the back plate by means of the retaining strap. One or more flexible hoses extend from the first stage pressure reduction valve to the shoulder straps so that breathing apparatus worn by the user may be conveniently connected thereto.

It is desirable for a SCBA harness, and in particular the back plate, to be adjustable in length. This allows it to be comfortably worn by users of different heights, who may have differing distances between their waist and shoulders. There are known harnesses which permit adjustment of the back plate length, which generally provide a number of incremental fixed adjustment lengths. However, these fixed lengths may not provide suitably fine adjustment for users whose body size falls between the fixed lengths provided, which can result in an uncomfortable or ineffective fit. However, in these previously considered harnesses, adjustment of the length of the back plate is a time-consuming and inefficient task which must be performed before the SCBA harness is donned. For example, if the adjustment is incorrect for the user, the SCBA harness must then be doffed, further adjusted, and then re-donned. This can waste valuable time at the scene which can delay an emergency response. In the alternative, if there is not sufficient time for the user to adjust the back plate, then this may result in them wearing an incorrectly-sized harness which could impair their effective use of the SCBA.

Therefore, it will be understood that it is desirable to provide an improved harness for an SCBA which enables quicker and easier length adjustment. According to a first aspect, there is provided a harness for a breathing apparatus comprising an adjustable back plate for accommodating a gas cylinder, the back plate being adjustable between a contracted position and an extended position, and a ratchet mechanism configured to permit contraction of the back plate towards the contracted position and inhibit extension of the back plate towards the extended position. The harness may further comprise a graspable element configured to enable a user to manually apply a force to move the back plate towards the contracted position while the back plate is worn by a user. The graspable element may comprise one or more grippable knobs or buttons, one or more straps. The graspable element may be arranged on a back side of the back plate which faces the user’s back in use. The graspable element may be arranged proximate a user’s lower back or kidney area in use. The graspable element may be attached to an upper element of the back plate and configured to be pulled downwards. In alternative examples, the graspable element may be attached to a lower element of the back plate and configured to be pulled upwards.

The ratchet mechanism may be releasable so as to selectively permit extension of the back plate. The ratchet mechanism may be manually releasable. The ratchet mechanism may automatically release when a fully contracted position of the back plate is reached. A release mechanism for the ratchet mechanism may be arranged on a back side of the back plate which faces a user’s back in use. This may prevent tampering with the ratchet mechanism while the harness is in use and may prevent damage to the ratchet mechanism.

The ratchet mechanism provides a plurality of intermediate positions for the back plate between the contracted and extended positions. There may be three intermediate positions, or five intermediate positions. The intermediate positions and the extended and contracted positions may be 5mm apart, 10mm apart, 15mm apart, 20mm apart, or 25 mm apart. The back plate may be adjustable over a range of at least 25mm, 50mm, 75mm, 100mm, or 125mm. In a particular example, the back plate may be adjustable over a range of 100mm-125mm. The adjustment range may be a length adjustment range. In a fully contracted position, the back plate may have a first length and, in a fully extended position, the back plate may have a second length which is longer than the first length by the total adjustment range. For example, if the adjustment range was 100mm and the fully contracted length of the back plate was 1000mm, then the fully extended length of the back plate would be 1 100mm.

The harness may further comprise a contraction stop mechanism configured to prevent contraction of the back plate beyond the contracted position.

The harness may further comprise an extension stop mechanism configured to prevent extension of the back plate beyond the extended position.

The back plate may comprise an upper back plate element for attachment to at least one shoulder support and a lower back plate element for attachment to a waist support. The upper and lower back plate elements may be moveable relative to each other between the contracted and extended positions to thereby adjust the length of the back plate. A portion of the upper or lower back plate element may be receivable within the other of the upper or lower component in a telescoping arrangement to thereby adjust the back plate.

The upper and lower back plate elements may be movable relative to each other in a longitudinal direction and, in particular a longitudinal direction with respect to the back plate (i.e. a vertical direction of the back plate in use). The upper back plate element may be an upper yoke. The lower back plate element may be a back plate frame or a major structural component of the back plate.

The upper and lower back plate elements may each comprise complimentary longitudinally-extending features for being slidably engaged to thereby slidably adjust the back plate between the contacted and extended positions.

At least one of the upper and/or lower back plate elements may comprise at least one longitudinally-extending rail for being slidably engaged with the other of the upper or lower back plate element to thereby slidably adjust the back plate between the contracted and extended positions.

The ratchet mechanism may comprise a pawl member provided on one of the upper or lower back plate element. The pawl member may be configured to engage with a plurality of tooth elements provided on the other of the upper or lower back plate element. Of course, the pawl member will engage with only one of the tooth elements at any time. The ratchet mechanism may comprise two pawl members, which may engage with a respective set of tooth elements. The pawl members may be configured to extend in opposing directions.

The pawl member may be a retractable projection, such as a latch or button. The tooth elements comprise a plurality of apertures into which the retractable projection can protrude. The tooth elements may comprise the lateral or side walls of the apertures. The pawl member or retractable projection may be biased into an extended position. The biasing may be provided with a spring.

The pawl member may comprise a chamfered portion configured such that during relative movement of the upper and lower back plate elements towards the contracted position, the lateral wall of the aperture contacts the chamfered portion so as to cause retraction of the pawl member. The chamfered portion may be formed on the upper surface of the pawl member such that a lateral wall of an aperture into which the pawl member extends can, on downward vertical movement, cause the pawl member to retract. In this way, movement of the back plate towards the contracted position causes the pawl member to move out of one aperture and then into the next aperture, and so on. The apertures may be vertically spaced.

The pawl member may comprise an abutment portion configured such that relative movement of the upper and lower back plate elements towards the extended position is inhibited or prevented by abutment of the abutment portion with the lateral wall. The abutment portion may be formed on the lower surface of the pawl member such that the tooth element, such as the lateral wall of an aperture into which the pawl member extends, abuts the abutment portion and prevents movement in that direction.

The upper back plate element comprises first and second longitudinally-extending rails and the lower back plate element comprises first and second complimentary longitudinally-extending channels for slidably receiving the first and second longitudinally-extending rails of the upper back plate element. The upper back plate element may further comprise a laterally-extending shoulder strap fixing portion for attachment to first and second shoulder straps at opposing lateral sides of the upper back plate element. The pawl member may be formed on the lower back plate element, and may extend laterally into one of the channels. A pawl member may be provided for each channel. The tooth elements, such as apertures, may be formed on or in the rails. The tooth elements may be vertically or longitudinally spaced along the rails. In some examples, only one rail and channel may be provided. In other examples, more than two rails and channels may be provided.

The harness may further comprise a biasing mechanism configured to bias the back plate towards the extended position.

According to a second aspect, there is provided a harness for a breathing apparatus comprising an adjustable back plate for accommodating a gas cylinder, the back plate being adjustable between a contracted position and an extended position; and a biasing mechanism configured to bias the back plate towards the extended position.

The biasing mechanism may comprise a spring element configured to bias the back plate towards the extended position.

The spring element may be configured to be extended by movement of the back plate in a direction from the extended to contracted position.

The spring element may be configured to be compressed by movement of the back plate in a direction from the extended to contracted position. According to a third aspect there is provided a breathing apparatus comprising a harness according to the first or second aspects, left and right shoulder straps, optionally wherein an upper end of each shoulder strap being attached to the upper back plate element, and a waist belt, optionally attached to the lower back plate element. Adjustment of the back plate adjusts a distance between the left and right shoulder straps and the waist belt to thereby permit the breathing apparatus to be worn by a plurality of different users having different back lengths without manual adjustment.

The breathing apparatus may be an SCBA (self-contained breathing apparatus) or a SCUBA (self-contained underwater breathing apparatus) or a CCBA (Closed Circuit Breathing Apparatus). The breathing apparatus may further comprise one or more of a breathing gas cylinder or cylinders, and breathing gas hoses.

The breathing gas delivery system may be a compressed breathing gas cylinder or a closed circuit breathing system. The closed circuit breathing system may comprise a compressed oxygen cylinder and a carbon dioxide scrubber, such as a soda lime scrubber.

It should be understood that, except where mutually exclusive, any features described with respect to the harness of the first aspect could equally be applied to the harness of the second aspect, and vice-versa.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a front view of a harness, when the harness is in an extended position;

Figure 2 shows a back view of a harness, when the harness is in an extended position;

Figure 3 shows a back view of a harness, when the harness is in a contracted position; and

Figures 4A-4D show detailed views of a ratchet mechanism.

Referring to Figure 1 , the harness 100 comprises a back plate 102, a pair of length- adjustable shoulder straps 104, 106 and a length-adjustable waist belt 108. The upper ends 1 10, 1 12 of shoulder straps 104, 106 are fixed to an upper portion of the back plate 102 and the belt 108 is fixed to a lower portion of the back plate 102. A first stage pressure reduction valve 1 14 is provided at the bottom of the back plate 102. In use, a cylinder of breathable gas (not shown) is connected to the first state pressure reduction valve 1 14 and it is retained by the back plate 102 and a retaining strap 1 16. Two air supply hoses, or conduits, 1 18, 120 are connected to the first stage pressure reduction valve for supplying breathable gas, one to the breathing apparatus of the harness wearer and one to a pressure gauge. The hoses 1 18, 120 extend substantially longitudinally from the first stage pressure reduction valve 1 14 and pass through an opening in the back plate 102 to the inside (or‘back’) of the back plate 102. In addition, or instead, one or more of the conduits may be an electrical cable.

For the avoidance of doubt, this side of the harness 100 and back plate 102 will be referred to as the‘front’. In use, this side of the harness 100 will face away from the wearer’s back. The opposing side of the harness 100 and back plate 102, shown in Figures 2 and 3, will be referred to as the‘back’, as it faces the user’s back and is therefore not visible in use.

The back plate 102 of the harness 100 comprises two parts: an upper back plate element 122 and a lower back plate element 124, which will be referred to as an upper yoke 122 and a back plate frame 124 (or frame 124) respectively. The upper yoke 122 and back plate frame 124 are configured to be moveable relative to one another such that the total length of the back plate 102 is adjustable.

The upper yoke 122 comprises a pair of spaced-apart parallel rails 126, which extend in the longitudinal direction with respect to the harness 100 and back plate 102 (i.e. generally vertically). The rails 126 are connected at their respective upper ends to a laterally-extending fixing portion 128 for the shoulder straps 104,106. The upper ends 1 10, 1 12 of the shoulder straps 104, 106 are attached to the fixing portion 128 with releasable connections to permit their removal for cleaning and maintenance. It will be understood that the upper yoke 122 generally forms an‘n’ shape, with the rails 126 extending vertically downward from the shoulder strap fixing portion 128. The rails 126 comprise conduit channels formed therein for receiving the conduits 1 18, 120 and routing them to the shoulder straps 104,106.

The back plate frame 124 forms the major structural component of the back plate 102. The waist belt 108 is attached to a lower part of the back plate frame 124, the first stage pressure reduction valve 114 and other gas-handling components are provided on the back plate frame 124, and the cylinder of breathable gas (not shown) is secured to and supported by the back plate frame 124. It should be understood, however, that in alternative examples, some of these parts may be provided on the upper yoke 122. In this example, the lower ends 129, 130 of the shoulder straps 104, 106 are attached to the back plate frame 124, but in other examples, they may be attached to the upper yoke 122, or the waist belt 108. The back plate frame 124 comprises a pair of channels 132 which extend longitudinally with respect to the back plate 102. The channels 132 are spaced apart by substantially the same distance as the rails 126 of the upper yoke 122 and are sized so as to slidably receive the rails 126 therein. For visibility of the yoke 122 and the frame 124, in this example, the back plate 102 (i.e. the upper yoke 122 and frame 124) are shown in an extended position, whereby the rails 126 are mostly retracted from the channels 132 such that the back plate 102 has an enlarged length. It will be appreciated that the distal ends of the rails 126 remain within the channels 132 to prevent the back plate 102 from becoming inadvertently disassembled. An extension stop mechanism 134 is provided to prevent the rails 126 of upper yoke 122 from completely withdrawing from the channels 132 of the frame 124. This extension stop mechanism 134 therefore defines the maximum extension, and thus the maximum length, of the back plate 102. In this example, the rails 126 (and therefore the upper yoke 122) may extend from the frame 124 by around 125mm before the extension stop mechanism 134 is engaged.

It should be understood that the upper yoke 122 is slidably attached to the back plate frame 124 in such a way that it can move longitudinally with respect to the frame 124 between the fully extended position shown in Figure 1 and the fully contracted position shown in Figure 2. The upper yoke 122 is generally freely slidable between the positions between the fully extended position and the fully contracted position, notwithstanding the biasing which will be discussed below. Accordingly, the total length of the back plate 102 can be adjusted in order to allow it to be comfortably worn by users of different heights or back lengths.

Referring now to Figure 2, the harness 100 is shown from the rear. In this view, like Figure 1 , the back plate 102 is in the fully extended position, in which the rails 126 of the upper yoke 122 are fully extended from the channels 132 of the back plate frame 124. In this configuration, the back plate 102 has its longest possible total length. Figure 2 also illustrates the configuration of the back plate 102 before it is donned by a user. As illustrated, the rails 126 each comprise a channel for housing a conduit 135.

At the upper portion of the back plate frame 124, a first end of each of a pair of tension springs 136 are secured to respective upper anchor points 138. The other end of each tension spring 136 is secured to a respective lower anchor point 140. The lower anchor points 140 are formed in a lower cross-plate 142 of the upper yoke 122 which is fixedly attached at a distal end 143 of each of the rails 126 and extends laterally across the back plate 102 between the rails 126. The springs 136 therefore form a biasing mechanism. In other examples, the lower anchor points may be formed at the distal ends 143 of the rails 126, in which case the cross plate 142 may be omitted. The tension springs 136 are configured such that they are in tension even when the upper yoke 122 and frame 124 are in this fully extended position. Therefore, the tension springs 136 constantly apply a resilient biasing force to urge the back plate 102 into its fully extended position by pulling the rails 126 longitudinally upwards out of the channels 132. The extension stop mechanism 134 (not shown in Figure 2) prevents the back plate 102 from extending beyond this fully extended position despite the force applied by the springs 136. It should be understood that in other examples, the tension springs 136 may instead be compression springs configured to extend to force the upper yoke 122 and the frame 124 apart. The springs 136 in this example are mechanical springs, but it should be understood that they may alternatively be pneumatic or magnetic springs.

The cross-plate 142 comprises a plurality of longitudinally spaced attachment points 144 to which the lower end of the springs 136 can be attached to form the lower anchor points 140 at different longitudinal locations on the upper yoke 122 to thereby adjust the extension of the springs 136 in this fully extended position of the back plate 102 (i.e. the shortest extension of the springs 136). This enables the biasing force applied by the springs 136 to be finely adjusted.

Also provided at the distal end 143 of each of the rails 126 is a grippable knob or button 146. The knobs 146 are therefore arranged at opposing lateral sides of the back plate 102 in the mid-to-lower back region of the user when the harness 100 is donned. The knobs 146 protrude from the rails (i.e. are proud of the rails in the direction of view of Figure 2) and are formed from a material having improved friction or grip, such as a rubberised or textured material. The user, when wearing the harness 102, can reach around to their lower back area and grip the knobs 146 to apply a downward force to the upper yoke 122. A strap 148 is also attached to the cross-plate 142. In this example, two straps 148 are attached at to the cross-plate 142 at opposing sides and hang below the back plate 102 for gripping by a user to apply a downward force to the upper yoke 122. The knobs 146 and straps 148 therefore provide two alternative means by which a downward force can be applied to the upper yoke 122 to counteract the biasing force of the springs 136 and urge the rails 126 longitudinally into the channels 132 to thereby contract the back plate 102. If a cross plate 142 is not provided, the knobs 146 and straps 148 may be attached to the rails 126 themselves, or to another suitable part of the upper yoke 122.

The back plate 102 also comprises a ratchet mechanism 150 which is configured to permit contraction of the back plate 102 and prevent extension of the back plate 102. The ratchet mechanism 150 is selectively releasable so that the back plate 102 can be extended from any partially or fully contracted position back to a more extended or fully extended position. The ratchet mechanism 150 provides a plurality of partially contracted positions and a fully contracted position in which the back plate 102 can be retained. Accordingly, although the springs 136 apply a biasing force to extend the back plate 102, the back plate 102 can be retained in a partially or fully contracted position by the ratchet mechanism 150, which position is illustrated shown in Figure 3.

As shown in Figure 3, when the back plate 102 is in a contracted position, the springs 136 are extended due to the increased distance between the lower anchor points 143 on the rails 126 and the upper anchor points 138 on the back plate frame 124. Accordingly, it will be understood that the springs 136 apply a biasing force to the extended position in all configurations of the back plate 102.

The ratchet mechanism 150 comprises first and second ratchets 152, which are provided at an upper portion of the back plate frame 124. The ratchets 152 face in opposing directions and are associated with each cooperating rail 126 and channel 132 pair. One of the ratchets 152 is shown in more detail in Figures 4A-D, which shows a detailed sectional view of the area A indicated in Figure 2 during a contracting movement of the back plate 102.

Referring to Figure 4A, the ratchet 152 comprises a pawl member 154 configured to move laterally with respect to the back plate 102 in a guide channel 156 in a sliding fashion. In Figure 4A, the pawl member 154 is shown in a fully protruded position, in which it protrudes laterally from the open end 158 of the guide channel 156 through the inner lateral wall 132a of the channel 132 of the back plate frame 124. As described above, the rail 126 is slidably received in the channel 132. In Figure 4A, a plurality of apertures 160 are visible in the inner lateral wall 126a of the rail 126. The apertures 160 are longitudinally spaced along the rail 126 and are each configured to receive the pawl member 154 when in its protruded position. The portions of the wall 126a between the apertures 160 form tooth elements 162 for engagement with the pawl member 154 as will be described below. To aid description of the operation of the ratchet 152, two of the apertures 160 are specifically denoted as a lower aperture 160a and an upper aperture 160b.

Referring still to Figure 4A, the pawl member 154 is biased into its fully protruded position by a spring 164. The pawl member 154 is prevented from extending further than this by stoppers 166 which interact with a finger-grip ridge 168 formed on a front face of the pawl member 154. In this position, the pawl member 154 protrudes into the lower aperture 160a of the rail 126. It will be understood that the springs 136 apply a biasing force to the upper yoke 122 which urges a lower tooth element 162 against a lower abutment surface 154a of the pawl member 154. As the abutment surface 154 is perpendicular to the direction of the biasing force of the springs 136 (i.e. the longitudinal direction of the back plate 102, the rail 126, and the channel 132), the rail 126 is prevented from upward movement relative to the channel 132, which would extend the back plate 102. Accordingly, when the pawl member is 154 is arranged in any of the apertures 160, extension of the back plate 102 is prevented.

In contrast, the pawl member 154 comprises an upper chamfered portion 154b which is formed at an angle to the longitudinal direction of back plate (i.e. to the biasing force direction of springs 136). Accordingly, when a force is applied to the upper yoke 122 which urges the rail 126 to move downward with respect to the channel 132 (as per arrow F), this results in the upper tooth element 162b applying a force on the chamfered portion 154b.

Referring now to Figure 4B, as the force of the tooth member 162b is not applied normal to the chamfered surface 154b, this force partially acts against the biasing spring 164 of the pawl member 154 and therefore urges the pawl member 154 to retract into the guide channel 156 as illustrated by arrow R. As the pawl member 154 retracts increasingly into the guide channel 156, the rail 126 moves downward with respect to the channel 132, resulting in contraction of the back plate 102.

As the rail 126 moves further downward, the upper tooth element 162b moves the pawl element 154 to its fully retracted position as shown in Figure 4C and blocks the pawl member 154 from moving out of the guide channel 156 back to its protruded position.

With yet further downward movement of the rail 126, the upper tooth element 162b eventually moves out of the way of the pawl member 154 as shown in Figure 4D. The pawl member 154 is then urged out of the guide channel 156 into the upper aperture 160b in direction P. In this position, extension of the back plate 102 back is prevented by the upper tooth element 162b abutting against the abutment surface 154a of the pawl member 154. If further contraction of the back plate 102 is required, then the contracting process shown described in Figures 4A-C can be repeated in order to move the pawl member 154 into the next aperture up the rail 126. Thus, each aperture 160 provides a position in which the back plate 102 can be temporarily locked at a certain total length. It should be understood that there are only a limited number of apertures 160 provided in the rail 126, so when the pawl member is located in the uppermost aperture 160, further contraction of the back plate 102 may be prevented. It should also be understood that the other ratchet 152 provided on the opposing lateral side of the back plate 102 and associated with the other rail 126 and channel 132 operates in a substantially similar fashion to that described in Figures 4A-D.

If the back plate is in a fully- or partially-contracted position, then the ratchet mechanism 150 can be selectively released in order to extend the back plate 102 back to a larger length as follows. Each of the pawl members 154 of the ratchets 152 is provided with a finger-grip ridge 168 as described above. Via this ridge 168, the user can manually apply a force to retract both of the pawl members 154 into their respective guide channels 156 (i.e. to the position shown in Figure 4C). In this position, the pawl members 154 will no longer engage with the tooth elements 162, so the biasing springs 136 will urge the rails 126 upwardly with respect to the channels 132 to extend the upper yoke 122 from the back plate frame 124 to thereby extend the back plate 102 back to an extended position. The back plate 102 can therefore be extended back to the fully-extended position as per Figures 1 and 2, or can be stopped midway through expansion in an intermediate position if desired. Once the user releases the pawl members 154, they will once again be biased to protrude into an aperture 160 of the rail 126 where possible. In an example in which the biasing springs are not provided, the user can retract the pawl members 154 and manually apply a force to extend the back plate 102.

When a user is required to don the harness 100, if the back plate 102 is not already in the fully extended position, the user first retracts the pawl members 154 and the back plate 102 will automatically extend to the fully extended position shown in Figures 1 and 2. In this position, the back plate 102 will be large enough to fit any user, but it will be understood that this configuration may be too large for some users.

However, the user now dons the harness 100 in this extended position. Once the shoulder straps 104,106, and waist belt 108 are secured, for all but the tallest users, the user will find that the back plate 102 is too long for his or her body size in its fully extended position. However, the user can reach around the harness 100 and, using the knobs 146 or the strap 148, apply a force to urge the upper yoke 122 towards the back plate frame 124, thereby contracting the back plate 102. Once the appropriate back plate length has been reached, the pawl members 154 will settle in the closest aperture 160 and the back plate 102 will be‘locked’ in the correct position by the ratchet mechanism 152. Over-contraction of the back plate 102 is prevented by the user’s body itself, which defines a minimum distance possible between the shoulder straps and waist belt.

Therefore, with the harness 100, the user can easily and quickly adjust the back plate 102 to fit their body without the need for lengthy manual adjustment prior to donning. With prior systems, is not possible for the back plate height to be adjusted without doffing the harness, so if the user was to manually adjust a back plate to the wrong height then delays would ensue.

In the illustrated example, the back plate 102 features a particularly advantageous arrangement comprising both the biasing mechanism provided by springs 136 and the ratchet mechanism 150. It should be understood however that other examples may omit one of the biasing mechanism or the ratchet mechanism and still provide technical advantages.

For example, if the back plate features only the biasing mechanism, then it is possible that, instead of using the ratchet mechanism to retain the back plate in a partially contracted position, an alternative locking mechanism could be used, or the appropriate fastening of the shoulder straps and waist belt to the user may apply sufficient force to overcome the biasing mechanism. Accordingly, the back plate would still provide the advantage that it is large enough to be donned by any size user then adjusted into position while being worn.

Alternatively, if the ratchet mechanism is provided but the biasing mechanism omitted, then the user could simply manually extend the back plate 102 to the fully extended position prior to donning, then use the ratchet mechanism to contract and lock the back plate to the correct height setting once donned as described above. Thus, such a harness would also provide the advantage that it is large enough to be donned by any size user then adjusted into position while being worn.