Harness for use with breathing apparatus

CROSS REFERENCE TO RELATED APPLICATION

0001This is a utility application based upon United Kingdom Application No. 0623719.2 filed Nov. 28, 2006 entitled Automatic Shoulder-Strap Tensioning System for which priority is claimed.

BACKGROUND OF THE INVENTION

0002The invention relates to a harness for use with breathing apparatus. In particular, the invention relates to a harness of the type worn by professional fire-fighters, though it may be applied to other sorts of harness, such as a diving harness, also.

0003A known harness <b>1</b> for use with breathing apparatus is shown in <figref idref="DRAWINGS">FIG. 1</figref>. The harness includes a back plate <b>2</b>, a waist belt <b>3</b>, shoulder straps <b>4</b> and shoulder pads <b>5</b>. A gas cylinder <b>6</b> containing pressurized gas is mounted to the back plate <b>2</b>. The weight of the harness and cylinder is transferred to the hips of the user through the waist belt <b>3</b> and to the upper body of the user through the shoulder pads <b>5</b> and shoulder straps <b>4</b>.

0004In this regard, each shoulder strap <b>4</b> is attached in two places. Namely, at a first end to one of the shoulder pads <b>5</b> and at a second end to the lower part of the back plate <b>2</b>. Each strap thus forms a loop, which takes some of the weight of the harness/cylinder unit and helps to hug the harness to the wearer's body.

0005The constant tension on the shoulders from the shoulder straps <b>4</b> makes wearing the harness <b>1</b> noticeable and can cause fatigue. In addition, when the wearer lifts an arm into the air, the shoulder strap <b>4</b> goes into tension, restricting movement and causing the associated shoulder pad <b>5</b> to dig into the wearer's shoulder. This is a particular problem when climbing ladders, reaching for high objects or crawling.

0006Furthermore, when the wearer is crawling one shoulder drops as the other arm is stretched out and this can cause tension in the strap <b>4</b> on the shoulder which drops to be completely removed. The shoulder strap and associated pad <b>5</b> can therefore fall off the shoulder making the unit unstable.

0007A known harness designed to alleviate the above problems is described in U.S. Pat. No. 6,290,111. In this harness, the shoulder straps are attached to opposite sides of a rigid element provided at the lower part of the back plate. The rigid element is pivotally connected to the back plate at a central point between where the shoulder straps are attached. Thus, when the wearer raises one arm the tension in the associated shoulder strap causes the rigid element to rotate about the central point, helping to reduce the tension in the strap. Furthermore, rotation of the rigid element causes tension to be applied to the other shoulder strap, helping to prevent the tension in that shoulder strap from being removed. However, the above harness allows only a limited degree of movement in which tension in the straps is accommodated, and tension is not always maintained in both straps which can make the harness unstable.

0008It is therefore desirable to provide a harness which enables the wearer to perform a fuller range of movement, in comfort, and which prevents the harness from becoming unstable.

0009According to the present invention, there is provided a harness for use with breathing apparatus, comprising: a back plate; two support straps, each of which extends between an upper part of the back plate and a lower part of the back plate, the two support straps being disposed on opposite sides of a central axis of the back plate; and a tension equalizing mechanism connected to the support straps and being arranged such that, when tension is applied to a first strap of the support straps, it acts to transfer the tension to the other, second strap, thereby increasing the tension in the second strap, the tension equalizing mechanism being resiliently biased towards a neutral configuration.

0010The resilient biasing of the tension equalizing mechanism towards the neutral configuration ensures that the support straps move with the body and remain tense. In this way, the harness is prevented from becoming unstable.

0011Preferably, the tension equalizing mechanism is arranged such that, when tension is no longer applied to the first strap, it acts to increase the tension in the first strap by decreasing the tension in the second strap and transferring the tension to the first strap.

0012Thus, the support straps are stopped from going slack and are always kept under tension, ensuring that the straps do not come off the user's shoulder during use of the harness.

0013Preferably, the tension equalizing mechanism includes first and second tension accommodating means connected by a connecting element, wherein, when tension is applied to the first support strap, the first tension accommodating means acts to increase an effective length of the first support strap and to reduce the tension in the strap, and the tension is transferred via the connecting element to the second tension accommodating means, which acts to reduce an effective length of the second support strap and to increase the tension in the second support strap.

0014The independent action of each of the first and second tension accommodating means on the first and second support straps, together with the connection therebetween, enables the wearer to perform a fuller range of movement and in greater comfort than previously possible. In addition, it ensures that the harness is stable when the user is crawling.

0015By enabling the wearer to move more freely and with less restriction, the harness advantageously allows the wearer to concentrate on the task at hand without having to worry about pain and stress caused by carrying the weight of the cylinder in an uncomfortable manner.

0016Preferably, first biasing means for urging the first attachment means to a central return position and/or second biasing means for urging the second attachment means to a central return position are provided, so as to resiliently bias the tension equalizing mechanism towards the neutral configuration. The biasing means may include an elastic return part such as a rubber return part or a spring.

0017Advantageously, the biasing means provide a small, controlled resistance to the movement of the wearer, making the adjustment of the shoulder straps feel more natural and secure to the wearer and ensuring that adequate tension is always provided in the straps.

BRIEF DESCRIPTION OF THE DRAWING

0018Reference is now made, by way of example only, to the accompanying drawings, in which:

0019<figref idref="DRAWINGS">FIG. 1</figref> shows a known harness;

0020<figref idref="DRAWINGS">FIG. 2</figref> shows a harness according to an embodiment of the invention;

0021<figref idref="DRAWINGS">FIG. 3</figref> shows a portion of the harness of <figref idref="DRAWINGS">FIG. 2</figref>;

0022<figref idref="DRAWINGS">FIG. 4</figref> shows a portion of a harness according to another embodiment of the invention; and

0023<figref idref="DRAWINGS">FIG. 5</figref> shows a return device as a biasing means in one of the attachment means shown in <figref idref="DRAWINGS">FIG. 4</figref>.

DESCRIPTION OF AN EMBODIMENT

0024<figref idref="DRAWINGS">FIG. 2</figref> shows a rear view of a harness <b>10</b> according to an embodiment of the invention. The harness <b>10</b> includes a back plate <b>11</b>, a waist belt <b>12</b>, shoulder straps <b>13</b> and shoulder pads <b>14</b>. Each shoulder strap <b>13</b> is attached to a respective one of the shoulder pads <b>14</b> at a first end, with each of the shoulder pads <b>14</b> being attached to an upper part of the back plate <b>11</b>. At a second end, each shoulder strap <b>13</b> is attached to a lower part of the back plate via a respective tension accommodating means <b>15</b> of a tension equalizing mechanism. Each tension accommodating means lies substantially in the plane of the back plate. The tension accommodating means <b>15</b> are linked by a link rod <b>16</b>, which floats freely between the two tension accommodating means. The link rod <b>16</b> may pass through a groove or recess <b>21</b> in the back plate, as can be seen in <figref idref="DRAWINGS">FIG. 3</figref>.

0025One of the tension accommodating means is shown in greater detail in <figref idref="DRAWINGS">FIG. 3</figref>. As can be seen, the tension accommodating means comprises an L-shaped member having first and second arms <b>17</b>, <b>18</b>. The first arm <b>17</b> is disposed substantially perpendicular to the second arm <b>18</b>. The shoulder strap <b>13</b> is connected to an end region of the first arm <b>17</b> and the link rod is connected to an end region of the second arm <b>18</b>. The L-shaped member is pivotally connected to a part <b>19</b> of the back plate <b>11</b> at pivot point <b>20</b>, which is positioned between its first and second arms. The L-shaped member can therefore rotate about the axis of the pivot (perpendicular to the plane of the back plate).

0026Thus, when a wearer lifts his left arm (the shoulder strap shown in <figref idref="DRAWINGS">FIG. 3</figref> being for the wearer's left side), the shoulder strap <b>13</b> is put under tension. The shoulder strap <b>13</b> in turn exerts a force on the pivot arm <b>17</b> urging the pivot arm upwards. Hence, the end region of the pivot arm <b>17</b> to which the strap <b>13</b> is attached is caused to move upwards and the L-shaped member rotates about the pivot point <b>20</b> accordingly. In this way, the wearer is able to lift his arm freely because the increased tension in the shoulder strap <b>13</b> is accommodated (relieved) by the upward movement of the pivot arm <b>17</b>, effectively lengthening the shoulder strap <b>13</b>.

0027Furthermore, the resultant clockwise rotation of the L-shaped member causes the end region of the arm <b>18</b> to which the link rod <b>16</b> is connected to move downwards and rightwards towards the back plate <b>11</b>. As the link rod <b>16</b> moves in this fashion, the tension in the shoulder strap <b>13</b> from the lifting of the wearer's left arm is transferred to the shoulder strap <b>13</b> on the wearer's right-hand side.

0028In other words, as can be seen from <figref idref="DRAWINGS">FIG. 2</figref>, the movement of the link rod <b>16</b> downwards and to the right causes the L-shaped tension accommodating means <b>15</b> on the other side of the back plate to undergo a clockwise rotation about its pivot point <b>20</b>. This rotation causes the end of the pivot arm <b>17</b> of the L-shaped member to which the shoulder strap <b>13</b> is connected to move downwards, shortening an effective length of the shoulder strap and thus increasing the tension in the shoulder strap <b>13</b> and pulling the associated shoulder pad <b>14</b> more firmly against the wearer's right shoulder. In this way, tension in the left shoulder strap is transferred to the right shoulder strap. Of course, the same occurs in reverse if the wearer lifts his right arm instead of his left arm. Hence, as the shoulder strap on one side of the harness effectively lengthens to reduce the tension caused by the wearer raising his arm on that side, the other shoulder strap effectively shortens to increase the tension on the other, dropped shoulder, due to the mirror-image arrangement of the tension accommodating means <b>15</b>.

0029Thus, the wearer is able to lift his arms freely without hindrance from the harness, and is able to crawl without risk of either shoulder strap <b>13</b> falling off as his shoulders drop, because of the manner in which the tension in one shoulder strap <b>13</b> is transferred to the other shoulder strap.

0030<figref idref="DRAWINGS">FIG. 4</figref> shows a portion of a harness according to another embodiment of the invention, namely the back plate <b>11</b> and shoulder straps <b>13</b> of the harness. In the figure, the shoulder straps <b>13</b> are not connected to the upper part of the back plate <b>10</b> via shoulder pads <b>14</b>, though of course they would be in the fully assembled harness.

0031In this embodiment, each tension accommodating means <b>30</b> is a pulley having first and second arms <b>31</b> and <b>32</b> disposed substantially at a right-angle with respect to one another. Each first arm <b>31</b> is connected to a respective shoulder strap <b>13</b> and each second arm <b>32</b> is connected to a common wire <b>33</b>, which acts as a connecting element between the tension accommodating means <b>30</b>. In addition, each tension accommodating means is pivotally connected to the back plate <b>11</b> about a respective pivot point <b>34</b>, which is provided between the first and second arms of the tension accommodating means.

0032The embodiment of <figref idref="DRAWINGS">FIG. 4</figref> thus functions in a similar way to that of <figref idref="DRAWINGS">FIGS. 2 and 3</figref> described above. Namely, tension in one of the shoulder straps <b>13</b> causes the pivot arm <b>31</b> to which it is connected to be raised upwards, thus rotating the tension accommodating means <b>30</b> about its pivot point <b>34</b>. For example, the tension accommodating means <b>30</b> shown on the right of the figure will rotate anti-clockwise if tension is applied to its shoulder strap <b>13</b>. This rotation effectively lengthens the shoulder strap <b>13</b> and enables the tension in the shoulder strap to be reduced, enabling the wearer to move freely.

0033In addition, this rotation causes the arm <b>32</b> to rotate anti-clockwise also, which in turn pulls on the wire <b>33</b>. The wire <b>33</b> is therefore put under tension and transfers the force (tension) to the tension accommodating means <b>30</b> on the left of the figure, rotating it in the anti-clockwise direction also. As this tension accommodating means rotates, the shoulder strap <b>13</b> to which it is connected is pulled downwards, pulling the shoulder pad <b>14</b> more firmly against the wearer's shoulder on that side. In other words, tension is transferred from one of the shoulder straps to the other shoulder strap. Of course, the same happens in reverse if tension is applied to the other shoulder strap initially.

0034<figref idref="DRAWINGS">FIG. 5</figref> shows a return device <b>35</b> as a biasing means in one of the tension accommodating means <b>30</b> shown in <figref idref="DRAWINGS">FIG. 4</figref>. The return device has elastic properties and has a central hole through which a pivot pin <b>36</b> of the pivot point <b>34</b> passes, together with outer holes <b>37</b> on each of four arm regions. The outer holes <b>37</b> engage with corresponding protrusions on the underside of the tension accommodating means <b>30</b>.

0035The return device <b>35</b> acts to bias the tension accommodating means <b>30</b> towards a central return (neutral, rest) position. When the tension accommodating means rotates, due to tension in the shoulder strap <b>13</b> or from the wire <b>33</b>, it causes the arms of the return device to move also, through the engagement of its protrusions with the holes <b>37</b>. When tension is no longer applied to the shoulder strap <b>13</b> or wire <b>33</b> and the tension accommodating means is thus not caused to rotate further, the return device <b>35</b> acts to return the tension accommodating means to its original position. This occurs as the elastic arms of the return device seek to return to their original, un-deformed configuration.

0036A biasing means could be provided for the harness of the embodiment of <figref idref="DRAWINGS">FIGS. 2 and 3</figref> also. In addition, the biasing means need not be a return part of the type described above. Any part having suitable elastic properties could be used, such as a spring (e.g. coil spring). A spring could, for example, be attached between a part of the L-shaped member, such as one of the arms, and a portion of the back plate.

0037It is preferable that the tension accommodating means are disposed symmetrically about a central longitudinal axis of the back plate. In this way, a smooth and even adjustment of the shoulder straps is realized.

0038As described above, a harness embodying the invention enables free independent movement of the wearer's arms and shoulders and transfers tension effectively from one shoulder strap to the other. When the wearer is climbing a ladder or crawling, the shoulder straps tighten and loosen alternately in synchronism with the user's movement, as the tension equalizing mechanism is resiliently biased in a neutral configuration.