Backpack with weight distribution features

0001This application claims priority on U.S. Provisional Application No. 60/870,513 filed on Dec. 18, 2006.

BACKGROUND OF THE INVENTION

00021. Field of the Invention

0003The invention relates to backpacks and to supports for transferring at least a portion of the weight of the backpack from the shoulders to the hips.

00042. Description of the Related Art

0005A backpack includes a bag-like enclosure that typically is formed from a flexible fabric. The backpack includes opposite top and bottom ends, a front surface that will face towards the person wearing the backpack, a rear surface that will face away from the person wearing the backpack and opposite left and right side surfaces. The bottom and front of the backpack generally are permanently closed, while the top of the backpack generally is configured to be opened. For example, many backpacks include a flexible top closure flap that is hinged at the upper end of the front surface of the backpack. Other backpacks include draw strings to close the open top, while still others use zippers across the top and sides.

0006Virtually all backpacks include one large enclosure that is accessible from the open top of the backpack. Many backpacks also include at least one small pocket on the rear surface and possibly small pockets on the left and rights side surfaces.

0007Left and right shoulders straps extend from a region of the backpack near the top end of the front surface to a region on the backpack at a lower position on the front surface. The shoulder straps generally are adjustable so that backpack can be accommodated on wearers of different sizes.

0008Many backpacks also include a belt that extends from lower regions of the left and right sides at or near the front of the backpack. Alternatively, the belt may extend from lower parts of the front surface of the backpack. A wearer of a backpack will mount the backpack over the shoulders. A belt, if provided, then can be tightening around the waist of the wearer. This typical backpack construction results in virtually all of the weight of the backpack being carried by the shoulders. The belt, if provided, generally is intended to prevent shifting of the weighted backpack during use.

0009The human spine is curved in a generally S-shape when viewed from the side. More particularly, the spine includes a rearwardly convex portion near the top of the back and a rearwardly concave portion lower on the back.

0010Backpacks can be used to carry very heavy loads, such as heavy books carried by students. The forces of these heavy loads generally are applied directly to the shoulders at or near the top of the upper curve in the spine. As a result, these heavy loads exert compressive forces on the spine and tend to urge the spine into a more pronounced curved S-shaped. Heavy loads carried by people of all ages can be damaging to the spine and can create both posture and disc problems. Heavy loads carried by school age children can be particularly problematic.

0011Efforts have been made to distribute at least a part of the load of a backpack to other parts of the body, such as lower areas on the back or the hips. These prior art efforts have included complex frames mounted externally of the backpack to lie between the backpack and the back of the person wearing the backpack. These cumbersome frames have been large, inconvenient and costly. Accordingly, it is an object of the subject invention to provide a backpack that is better able to distribute weight from the shoulders to the hips of the person wearing the backpack.

SUMMARY OF THE INVENTION

0012The invention relates to a load transfer device for a backpack and to a backpack that incorporates a load transfer device.

0013The load transfer device of the subject invention includes an elongate central support with opposite top and bottom ends. Front and rear surfaces extend along the center support from the top end to the bottom end. The front surface is intended for facing the person wearing the backpack with which the load transfer device is employed. The back surface is intended for facing the backpack. The front and rear surfaces of the central support are generally parallel to one another, but are nonplanar. In particular, portions of the front surface of the central support near the bottom end of the central support define a convex curved shaped. The curve preferably is generated about one or more left-to-right axes. Portions of the rear surface of the central support near the lower end of the central support preferably are approximately parallel to corresponding parts of the front surface, and hence preferably define a concave shape. The convex shape of the front surface of the central support near the lower end of the central support is intended to approximate the rearwardly concave curved shape of the lower regions of the back of the person who will wear the backpack with which the load transfer device is employed.

0014Upper areas of the central portion of the load transfer device may be substantially planar or may be curved slightly to define a concave surface facing forwardly. The central support may be substantially solid at all locations thereon. However, the central support also may include a plurality of openings passing through the central support from the front surface to the rear surface thereof. The openings reduce the cost and weight of the load transfer device and contribute to air circulation when the load transfer device is being used. Openings also contribute to resiliency for dampening forces caused by a shifting of the load.

0015The load transfer device further includes left and right supports extending respectively from the left and right extremes of the central support at positions near the bottom end of the central support. As a result, the load transfer device defines a generally inverted T-shape when viewed from the front or rear. The left and right supports are substantially mirror images of one other so that the entire load transfer device is substantially symmetrical about a vertical axis extending centrally through the central support. The left and right supports have opposite front and rear surfaces. The front surfaces of the left and right supports extend continuously from the front surface of the lower portion of the central support and the rear surfaces of the left and right supports may extend generally continuously from the rear surface of the central support.

0016The left and right supports define compound curved shapes intended to confirm generally to the shape of the lower back of the person who wears the load transfer device. In this regard, the front surface of the left and right supports preferably defines a convex curved shape when viewed through any vertical cross-section taken through the left or right supports. Thus, these curved shapes are generated about one or more axes that extend substantially horizontally in a left to right direction. The front surfaces of the left and right support also define a concave shape when view from above or below. Thus, the front surface of the lower parts of the load transfer device are curved about one or more vertical axes disposed in front of the load transfer device. The side-to-side concave curvature of the front surface of left and right supports of the load transfer device defines a flatter curve than the top to bottom convex shape of the front surface of lower parts of the load transfer device. These compound curved shapes conform generally to the compound curved shapes of the lower portion of a person's back so that the lower front surface of the load transfer device can nest comfortably against the lower back.

0017The left and right supports have top edges that slope gradually down from the left and right sides of the central support. Bottom edges of the left and right supports initially slope gradually down from the central support, but then curve gradually up towards the respective left and right extremes. As a result, the bottom edge of the load transfer device is concave near the center of the load transfer device, but then defines left and right convex edges spaced farther out from the center of the load transfer device. The extreme left and right edges of the load transfer device define smooth convex curves. The left and right supports can be substantially continuous at all locations along the front and rear surfaces. However, the left and right supports also can be configured similar to the central support with a plurality of apertures extending between the front and rear surfaces. As described above, the apertures reduce cost and weight and facilitate air circulation through the load transfer device. Furthermore, the aperture can contribute to resiliency for dampening force generated by shirts in the load.

0018The inverted T-shaped load transfer device preferably is made from a thermoplastic material and may be molded unitarily from a thermoplastic material. Alternatively, the load transfer device may be an assembly of a plurality of components that are adjustably or replaceably mounted to one another so that the dimensions of the load transfer device can be varied in accordance with the size of the person who will be using the load transfer device. For example, the central support of the load transfer device may be molded unitarily from a thermoplastic resin. The left and right supports then may be mounted adjustably or replaceably to the central support. As a further alternative, the central support may be formed from two or more components that are adjustable or replaceable relative to one another to change the vertical dimension of the central support. The optional replaceable feature of the left and right supports enables the use of a universal central support with left and right supports of appropriate selected size.

0019The load transfer device may be used with a backpack that can be of generally conventional design. In this regard, the backpack includes opposite top and bottom ends. The bottom end preferably is permanently closed. However, the top end of the backpack preferably is configured to be opened to access the interior of the backpack. The backpack further includes a front surface, a rear surface and opposite left and right surfaces, all of which extend substantially from the bottom end to the top end. Small pockets optionally can be formed in the rear surface and/or the opposite side surfaces. Additionally, a closure flap may be hinged to the top of the front surface to permit selective closing of the open top of the backpack. A left shoulder support preferably is looped from an upper left front area of the backpack to a lower left front area of the back pack. Similarly, a right shoulder support preferably is looped from an upper right front area of the backpack to a lower right front area of the backpack. The shoulder straps preferably are adjustable so that the backpack can be adjusted to the size of the person who will be wearing the backpack.

0020A left belt strap preferably extends from the lower left front area of the backpack, and a right belt strap preferably extends from the lower right front area of the backpack. The left and right belt straps are configured to be mated adjustably to one another so that the belt straps can be wrapped securely but comfortably about the waist of the person who is wearing the backpack for urging lower parts of the load transfer device into a comfortable nested relationship with lower parts of the back and rear areas of the hips. For example, the left and right belt straps can be provided with mateable buckles or Velcro type of connection members.

0021The lower front surface of the backpack preferably is configured to receive the above-described load transfer device. For example, the lower front surface of the backpack can be formed with a pocket or pouch dimensioned to receive the load transfer device. The pocket or pouch for receiving the load transfer device may be closeable by a zipper, snaps or Velcro-type attachment members. Alternatively, the pocket or pouch at the lower front surface of the backpack can be closed more permanently by sewing, adhesive, ultrasonic welding or the like after the load transfer device has been positioned properly in the pocket or pouch.

0022The load transfer device of the subject invention is positioned in the pouch or pocket at the rear surface of the backpack so that the above-described front surface of the load transfer device faces forwardly and away from the backpack, and hence towards the person wearing the backpack. The central support of the load transfer device is aligned vertically relative to the backpack and symmetrically between the left and right sides of the backpack. The left and right supports of the load transfer device extend respectively in left and right directions at or near the bottom end of the backpack. The load transfer device preferably is affixed permanently to the front surface of the backpack to prevent shifting during use or between uses. The secure attachment of the load transfer device to the backpack can be achieve by a rivet, staple, adhesive, welding, threads or other known attachments methods.

0023The backpack with the load transfer therein is worn in the conventional manner with both left and right shoulders strap and with the belt. The belt urges the left and right supports of the load transfer device into the concave portions of the lower back so that lower areas of the left and right supports are supported comfortably above top areas of the pelvic bone structures. The convex top to bottom shape of the lower portions of the front surface of the load transfer device enables the load transfer device to be nested comfortably against upper regions of the pelvic area without sharp edges that could bite into the lower back or the hips of the person wearing the backpack. Similarly, the concave shape of the front surface of lower portions of the load transfer device when viewed from above or below enable the load transfer device to be supported across a major area of a pelvic region in a left to right direction extending completely across the back of the wearer and onto the side areas of the hips or pelvis. As a result, a significant portion of the load of the backpack is shifted from the shoulders to the hips, thereby avoiding or reducing the compressive stresses exerted on spine and the bending moments imposed upon the spine. The shoulder straps then assume a significantly reduced weight carry role and are used more for alignment and stabilization.

BRIEF DESCRIPTION OF THE DRAWINGS

0024<figref idref="DRAWINGS">FIG. 1</figref> is a front perspective view of a first embodiment of a load transfer device in accordance with the invention.

0025<figref idref="DRAWINGS">FIG. 2</figref> is a cross-sectional view taken along line <b>2</b>-<b>2</b> in <figref idref="DRAWINGS">FIG. 1</figref>.

0026<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional view taken along line <b>3</b>-<b>3</b> in <figref idref="DRAWINGS">FIG. 1</figref>.

0027<figref idref="DRAWINGS">FIG. 4</figref> is a cross-sectional view taken along line <b>4</b>-<b>4</b> in <figref idref="DRAWINGS">FIG. 1</figref>.

0028<figref idref="DRAWINGS">FIG. 5</figref> is a rear elevational view of the load transfer device shown in <figref idref="DRAWINGS">FIG. 1</figref>.

0029<figref idref="DRAWINGS">FIG. 6</figref> is a right side elevational view of the load transfer device shown in <figref idref="DRAWINGS">FIGS. 1-5</figref>.

0030<figref idref="DRAWINGS">FIG. 7</figref> is a front elevational view of the load transfer device of <figref idref="DRAWINGS">FIGS. 1-6</figref> incorporated into a backpack.

0031<figref idref="DRAWINGS">FIG. 8</figref> is a left side elevational view showing the assembly of the backpack and load transfer device during use.

0032<figref idref="DRAWINGS">FIG. 9</figref> is a longitudinal cross-sectional view of the backpack in use.

0033<figref idref="DRAWINGS">FIG. 10</figref> an exploded front elevational view of a load transfer device in accordance with a second embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0034A load transfer device in accordance with a first embodiment of the invention is identified generally by the numeral <b>10</b> in <figref idref="DRAWINGS">FIGS. 1-5</figref>. The load transfer device <b>10</b> is molded unitarily from a thermoplastic resin and includes a central support <b>12</b> with opposite top and bottom ends <b>14</b> and <b>16</b>. Opposite left and right edges <b>18</b> and <b>20</b> extend from the top end <b>14</b> towards the bottom end <b>16</b> of the central support <b>12</b>. In this context, the terms left and right correspond to the respective left hand and right hands of the person wearing the load transfer device <b>10</b>. The central support <b>12</b> further includes a front surface <b>22</b> extending from the top end <b>14</b> to the bottom end <b>16</b> as shown in <figref idref="DRAWINGS">FIG. 1</figref> and a rear surface <b>24</b> opposite the front surface <b>22</b>, as shown in <figref idref="DRAWINGS">FIG. 5</figref>. Portions of the front and rear surfaces <b>22</b> and <b>24</b> near the top end <b>14</b> of the central support <b>12</b> are substantially planar in this embodiment. However, portions of the front surface <b>22</b> near the bottom end <b>16</b> define a convex curve <b>26</b> when viewed from the side or in the cross section shown in <figref idref="DRAWINGS">FIG. 2</figref>. Portions of the rear surface <b>24</b> opposite the convexly curved portion <b>26</b> on the front surface <b>22</b> have a correspondingly configured concave curved surface <b>28</b>. The curved surfaces <b>26</b> and <b>28</b> are generated about one or more generally horizontal axes disposed rearwardly of the load transfer device <b>10</b>. The radius of curvature and the extent of the curve are selected to permit the curve <b>26</b> on the front surface <b>22</b> of the central support <b>12</b> to nest comfortably in lower central portions of a person's back. In the illustrated embodiment, the front and rear surfaces <b>22</b> and <b>24</b> are substantially planar at locations closer to the top end <b>14</b> of the central support <b>12</b>. However, in other embodiments, upper parts of the central support may be nonplanar. For example, the front surface <b>22</b> of the central support <b>12</b> may be slightly concave near the top end <b>14</b> to confirm generally to the curved shape of a typical human spine between the shoulder blades. In the illustrated embodiment, the entire central <b>12</b> is substantially solid at all locations thereon. However, a plurality of apertures may be molded to extend through the central support <b>12</b> from the front surface <b>22</b> to the rear surface <b>24</b> at a plurality of locations to reduce the cost and weight of the entire load transfer device <b>10</b> and to accommodate air flow.

0035The load transfer device <b>10</b> further includes left and right supports that extend from the left and right extremes of lower parts of the central support <b>12</b>. The left and right supports <b>30</b>L and <b>30</b>R are substantially mirror images of one other so that the weight transfer device <b>10</b> is substantially symmetrical along a vertical axis extending centrally through the central support <b>12</b>. As a result, the load transfer device <b>10</b> resembles an inverted T-shape when viewed from the front or rear. Additionally, the left and right supports <b>30</b>L, <b>30</b>R are configured so that the load transfer device generally assumes the shape of whale's tail.

0036The left and right supports <b>30</b>L and <b>30</b>R each have a front surface <b>32</b>L, <b>32</b>R and an opposite rear surface <b>34</b>L, <b>34</b>R that extend substantially continuously and uniformly from the respective front and rear surfaces <b>26</b>, <b>28</b> of the central support <b>12</b>. The left and right supports <b>30</b>L, <b>30</b>R have compound curved shapes across their front and rear surfaces <b>32</b>L, <b>32</b>R, <b>34</b>L, <b>34</b>R. More particularly, the front surfaces <b>32</b>L, <b>32</b>R define convex curves when viewed from the side or through the vertical cross-section, as shown in <figref idref="DRAWINGS">FIG. 3</figref>. However, the front surfaces <b>32</b>L and <b>32</b>R of the left and right supports <b>30</b>L and <b>30</b>R define concave curves when viewed from above or below and as shown in the cross-section of <figref idref="DRAWINGS">FIG. 4</figref>. The concave shapes of the front surfaces <b>32</b>L and <b>32</b>R are generated about one or more axes extending generally vertically and in front of the load transfer device <b>12</b>. As shown by comparing <figref idref="DRAWINGS">FIGS. 3 and 4</figref>, the left to right concave curve defined by the front surfaces <b>32</b>L and <b>32</b>R have larger radii and hence flatter curves than the top to bottom convex curves on the front surfaces <b>32</b>L and <b>32</b>R, as shown in <figref idref="DRAWINGS">FIG. 3</figref>. The side-to-side concave curves defined by the front surfaces <b>32</b>L and <b>32</b>R of the left and right side supports <b>30</b>L and <b>30</b>R are configured to nest in a left to right direction across the lower back of a person wearing the load transfer device <b>10</b> to achieve a supporting relationship with the rear of the pelvic region.

0037The left and right supports <b>30</b>L and <b>30</b>R have top edges <b>36</b>L and <b>36</b>R that curve gently down at distances farther from the central support <b>12</b>. The left and right supports <b>30</b>L and <b>30</b>R further have bottom edges <b>38</b>L and <b>38</b>R with concave curved sections adjacent the central support <b>12</b> and convex curved sections farther out from the central support <b>12</b>. Extreme outer ends of the left and right supports <b>30</b>L and <b>30</b>R define smoothly curved left and right side edges <b>40</b>L and <b>40</b>R that continue as convex curves from the top edges <b>36</b>L, <b>36</b>R to the bottom edges <b>38</b>L, <b>38</b>R.

0038The load transfer device <b>10</b> is used with a backpack <b>42</b> as shown in <figref idref="DRAWINGS">FIGS. 7-9</figref>. The backpack <b>42</b> includes a closed bottom <b>44</b>, a top <b>46</b> that can be selectively opened and closed, a front surface <b>48</b>, a rear surface <b>50</b> and left and right side surfaces <b>52</b> and <b>54</b>. The structure for opening the backpack can take any of the known configurations, including a flap hinged at the top <b>46</b>, draw strings with or without a flap, a zipper extending across parts of the side surfaces of <b>52</b> and <b>54</b> and across the top <b>46</b>, and other known constructions or constructions that may yet be developed. The back surface <b>50</b> and the side surfaces <b>52</b> and <b>54</b> are shown without pockets therein for simplicity. However, pockets can be provided. The front surface <b>48</b> defines the part of the backpack <b>42</b> that will face the person wearing the backpack <b>42</b>, as shown most clearly in <figref idref="DRAWINGS">FIGS. 8 and 9</figref>.

0039Left and right shoulders straps <b>56</b> and <b>58</b> are provided on the front surface <b>48</b>. More particularly, the left shoulder strap <b>56</b> extends from a left top region of the front surface <b>48</b> to the left bottom region of the front surface <b>48</b>. Similarly, the right shoulder strap <b>58</b> extends from a right top region of the front surface <b>48</b> to a right bottom region of the front surface <b>48</b>. Although not shown, the shoulder straps <b>56</b>, <b>58</b> are adjustable, as known in the art, to accommodate people of different sizes.

0040The backpack <b>42</b> further includes left and right belts <b>60</b> and <b>62</b> extending from lower left and right regions of the front surface <b>48</b> of the backpack <b>42</b>. Regions of the belts <b>60</b> and <b>62</b> remote from the front surface <b>48</b> can be attached to one another to hold the backpack <b>42</b> close to the back of the person wearing the backpack <b>42</b>.

0041In the illustrated embodiment, the front surface <b>48</b> of the backpack <b>42</b> includes a pocket <b>64</b> with a zipper <b>66</b> for closing the pocket <b>64</b>. The pocket <b>64</b> is dimensioned to accommodate the load transfer device <b>10</b>. More particularly, the zipper <b>66</b> can be opened and the load transfer device <b>10</b> can be slid into the pocket <b>64</b> so that the curves <b>40</b>L and <b>40</b>R at the outer lateral extremes of the left and right supports <b>30</b>L and <b>30</b>R are nested tightly into the lower left and right corners of the pocket <b>64</b>, as shown most clearly in <figref idref="DRAWINGS">FIG. 7</figref>. In this mounted position, the top end <b>14</b> of the central support <b>12</b> is slightly below the zipper <b>66</b>. Portions of the central support <b>12</b> near the top end <b>14</b> preferably are affixed to portions of the front surface <b>48</b> rearward of the pocket <b>64</b>. This affixation is intended to prevent shifting of the load transfer device <b>10</b> in the pocket <b>64</b>. The affixation can be achieved by tacks, screws, rivets, adhesives, sewing, ultrasonic welding or the like. The zipper <b>66</b> then is closed. It will be appreciated that the zipper <b>66</b> is provided merely for a convenient way to enclose the load transfer device <b>10</b> into a concealed position adjacent the front surface <b>48</b> of the backpack <b>42</b>. Other techniques for enclosing the load transfer device <b>10</b> can be provided. For example, all or part of the pocket <b>64</b> can be attached to the front surface <b>48</b> of the backpack <b>42</b> after the load transfer device <b>10</b> has been mounted. This affixation of the pocket <b>64</b> can be achieved by sewing, adhesive, rivets, staples, ultrasonic welding or the like.

0042The backpack <b>42</b> is worn and used in the conventional manner. However, as shown most clearly in <figref idref="DRAWINGS">FIG. 8</figref>, lower edges <b>38</b>L and <b>38</b>R of the left and right supports <b>32</b>L and <b>32</b>R nest closely into the compound curves defined at lower side regions of a person's back. Thus, a substantial part of the weight of the backpack <b>42</b> will be carried by upper areas of the pelvic regions rather than by the shoulders. Portions of the central support <b>12</b> above the left and right supports <b>32</b>L and <b>32</b>R are spaced rearward from the person's back “B” by a distance “D” of about 2-3 inches on most people. The shoulder straps <b>56</b> and <b>58</b> will carry some load and will contribute significantly to the stabilization of the load. However, compressive forces on the spine and bending moments imposed upon the spine will be reduced significantly or eliminated. The top to bottom convex curved configuration of the front surface <b>32</b>L, <b>32</b>R on the left and right supports <b>30</b>L and <b>30</b>R ensures that the load is transferred to the pelvic region by a surface and not by an edge. As a result, the backpack <b>42</b> with the load transfer device <b>10</b> therein will comfortably transfer the load to the pelvic region of the person wearing the backpack. Additionally, the concave side-to-side curve existing on the front surfaces <b>32</b>L and <b>32</b>R of the left and right supports <b>30</b>L and <b>30</b>R ensure that the load is transferred over a large left to right region of the person's pelvic area, thereby avoiding a concentration of stresses or loads on the person wearing the backpack <b>42</b>.

0043<figref idref="DRAWINGS">FIGS. 1-9</figref> illustrate a load transfer device <b>10</b> that is formed unitarily from a synthetic resin. These load transfer devices <b>10</b> would have to be manufactured in different sizes to accommodate the size of the person wearing the backpack <b>42</b> and the size of the backpack <b>42</b>. <figref idref="DRAWINGS">FIG. 10</figref> shows an alternative load transfer device <b>70</b> formed from four components that are adjustable and/or replaceable. More particularly, the load transfer device <b>70</b> includes a central support <b>72</b> with an upper support leg <b>74</b> and left and right supports legs <b>76</b>L and <b>76</b>R respectively. The adjustable load transfer device <b>70</b> further includes an upper support <b>84</b> that can be adjustably mounted to the upper support leg <b>74</b> of the central support <b>72</b>. Additionally, left and right lower supports <b>86</b>L and <b>86</b>R can be mounted respectively on the left and right lower support legs <b>76</b>L and <b>76</b>R. The left and right lower support legs <b>76</b>L and <b>76</b>R are molded unitarily with resiliently deflectable locking latches <b>78</b>L and <b>78</b>R that can be locked respectively in one of several locking apertures <b>88</b>L and <b>88</b>R formed on the left and right lower supports <b>86</b>L and <b>86</b>R. As a result, the left and right lower supports <b>86</b>L and <b>86</b>R can be mounted at an appropriate position on the left and right support leg <b>76</b>L and <b>76</b>R to achieve a preferred overall width for the adjustable load transfer device <b>70</b>.

0044While the invention has been described with respect to certain embodiments, it is apparent that various changes can be made without departing from the scope of the invention as defined by the appended claims. For example, with respect to the second embodiment, the left and right lower support <b>86</b>L and <b>86</b>R can be mounted to the left and right support legs <b>76</b>L and <b>76</b>R at only one position. However, left and right lower supports <b>86</b>L and <b>86</b>R of different dimensions can be mounted selectively onto the lower support legs <b>76</b>L and <b>76</b>R.

0045In the second embodiment, an upper support <b>84</b> is illustrated as being mounted to the upper support legs <b>74</b>. However, the upper support may be formed unitarily as part of the central support <b>72</b>.