Patent Publication Number: US-2019191856-A1

Title: Backpack having a vertical holding frame and a support cover

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national phase filing under 35 C.F.R. § 371 of and claims priority to International Patent Application No. PCT/FR2017/052125, filed on Jul. 21, 2017, which claims the priority benefit under 35 U.S.C. § 119 of French Application No. 1657525, filed on Aug. 3, 2016, the contents of which are hereby incorporated in their entireties by reference. 
    
    
     BACKGROUND 
     Some embodiments relate to the field of backpacks. More particularly, some embodiments relate to a backpack having a frame that allows it, once placed on the ground, to remain vertical and form a support. 
     The document US2014/0076942A1 describes a backpack including a frame that is fixed with respect to a storage envelope. This frame includes a base at the bottom and a panel at the top, the rear side of the base and the rear side of the panel being connected by two struts. The backpack can thus rest vertically on its base, the panel forming a seat. However, the significant overhang between the panel and the struts, the structure of the base, and the surface delimited between the bars of the base, result in low stability of the assembly and require relatively flat ground. 
     SUMMARY 
     The technical problem to be solved by some embodiments are therefore that of improving or enhancing a backpack that makes it possible to realize a support while giving it greater stability, especially in the case of uneven ground. 
     To this end, some embodiments are directed to a backpack including:
         a storage envelope having a bottom and a top,   shoulder straps at the front of the storage envelope,   a rigid cover covering the top of the envelope,   a fixed frame that is fastened to the cover and includes at least one lower bearing surface, known as the fixed lower bearing surface,   a movable frame hinged to the cover or to the fixed frame, including a lower bearing surface, known as the movable lower bearing surface, the movable frame being movable between
           a stowed position against the assembly formed by the storage envelope, the cover and the fixed frame, and   a deployed position in which the movable lower bearing surface is at a distance from the envelope,
 
the frames being arranged such that, in the deployed position, the lower bearing surfaces are arranged around the storage envelope such that the backpack can be placed in a balanced manner on these lower bearing surfaces, the frames forming the support for the cover.
   
               

     Thus, when the backpack is placed on the ground with the movable frame in the deployed position and on the lower bearing surfaces, the area delimited between the lower bearing surfaces is wider than the bottom of the storage envelope, since the movable lower bearing surface is at a distance from this envelope. The backpack is thus more stable and maintained vertically. 
     Moreover, by having an area delimited between the wider lower bearing surfaces, any unevenness of the ground has less impact on the balanced state of the backpack. 
     Furthermore, the cover forms a support, for example for setting down objects, or for sitting down. 
     Note that the fixed frame is the to be fixed because it is not movable with respect to the storage envelope. 
     Some embodiments may optionally have one or more of the following features:
         the fixed lower bearing surface is situated at the bottom and the rear of the backpack, and, in the deployed position, the movable lower bearing surface is situated at the bottom and the front of the backpack; thus, the movable frame is less bulky when against the user&#39;s back;   the frames and the cover are arranged such that the cover forms a seat when the backpack is placed in a balanced manner on the lower bearing surfaces; this allows the user to rest by placing his backpack on the ground and sitting on the cover, without needing to carry an additional chair;   the movable frame is hinged to a front edge of the cover; this makes it easier to produce the backpack;   the fixed frame and the cover form a single one-piece part; this makes it easier to produce the cover and its support and improves its strength;   the one-piece part may be formed by a shell, this shell having an upper portion forming the cover and a lower portion forming the fixed frame, the lower portion covering the rear of the storage envelope; the shell thus also forms protection for the rear of the backpack, especially with respect to impacts;   the outer surface of the upper portion and the outer surface of the lower portion are smooth; this allows the user to walk bent over under branches, allowing the latter to slide over the shell;   the lower portion and/or the upper portion include lateral returns at least partially covering the sides of the storage envelope; these returns make it possible to reinforce the upper portion and/or the lower portion; moreover, this also makes it possible to spread the branches better to the side when walking bent over;   the cover is arranged so as to be inclined with respect to the bottom of the storage envelope, the cover approaching the bottom of the storage envelope in a direction from the front to the rear of this storage envelope; this makes it possible to have a less inclined cover when the backpack is placed on the ground in the deployed position; for example, the frames and the cover can be arranged such that, when the movable frame is in the deployed position and when the backpack is placed in a balanced state on the lower bearing surfaces, the cover has a horizontal flat receiving part, thereby making it easier to sit down or to set down a measuring instrument or a camera; the receiving part can represent the greater part of the surface of the cover;   the storage envelope includes one or more access openings for accessing the inside of the storage envelope that are arranged on at least one of the sides of the storage envelope; this makes it possible to access the inside of the storage envelope without separating it from the cover; the cover can be thus be fastened inseparably to the backpack; this is particularly useful in the abovementioned case, in which a shell forms the cover and the fixed frame;   the storage envelope has several of the access openings:
           at least one first access opening being arranged on the left-hand side of the storage envelope, and   at least one second access opening being arranged on the right-hand side of the storage envelope and opposite the first access opening;
 
this makes it possible to access the inside of the storage envelope across its entire width, simply from one side or the other;
   
           the movable frame is formed by a framework; this is a simple and robust embodiment;   the movable frame is formed by a U-shaped bar with a transverse portion including the movable lower bearing surface and lateral ends hinged to the cover or to the fixed frame; this is a simple embodiment;   according to one or the other of the two preceding points, the backpack can include:
           catches mounted at the top and bottom of the movable frame,   a textile arranged in front of the movable frame and stretched between these catches, the catches being arranged between the textile and the movable frame so as to stretch the textile away from the movable frame;
 
the catches and the textile allow the user to keep his back away from the movable frame, thereby improving comfort;
   
           the catches mounted at the bottom of the movable frame can be arranged above and at a distance from the movable lower bearing surface; this allows the textile not to touch the ground when the backpack is put down on its lower bearing surfaces;   the backpack includes a strap fastened to the front of the storage envelope at one end and to the movable frame at the other end, so as to limit the spacing apart of the movable frame from the storage envelope in the deployed position;   the strap is an abdominal strap of the backpack; this limits the number of straps;   a slide is arranged on the storage envelope, the strap passing through the slide such that, as a result of the strap being pulled, the latter causes the movable frame to move toward and/or be clamped against the storage envelope; this makes it easy to pass from one position to another;   according to the preceding point and when the strap is the abdominal strap, the latter is also connected to at least one closing fastener of the abdominal strap, the abdominal strap also being designed to slide with respect to this or these fasteners, such that by pulling on the abdominal strap, the latter is tightened around the abdomen at the same time as the movable frame is clamped against the storage envelope; this simplifies the hand movements that may be necessary to move the movable frame from one position to another;   the slide is a ring including an annular element and a central strut connected to this annular element; this is a simple and strong embodiment of a slide;   the strap includes:
           a first end connected in a sliding manner to a fastener of the abdominal strap, then   a first strap portion passing in one direction through the ring and between the central strut and the annular element, then between the central strut and the front of the storage envelope, and then passing in the other direction through the ring and between the central strut and the annular element, then being fastened to the movable frame;
 
this constitutes one way of producing a mover for moving the movable frame into the stowed position;
   
           according to the preceding point, the first strap portion can also be doubled by an additional strap portion fastened to the movable frame on one side and to the strap between the central strut and the first end on the other side, such that the first strap portion and the additional strap portion can slide on either side of the central strut, the fastening of the additional strap portion to the strap forming a stop; this limits the amplitude of the spacing apart of the movable frame from the storage envelope;   the annular element is pressed securely against the storage envelope and the central strut is offset forward with respect to the annular element; this improves the robustness of the fastening of the strap, the pressing of the movable frame and the sliding of the strap;   alternatively, the slide is a loop, in particular stitched onto the storage envelope; this is a very simple embodiment.       

     In some embodiments, the front of the backpack is the side placed against the user&#39;s back when wearing the backpack and the rear is the opposite side. The right and the left of the backpack are defined with respect to this orientation. This orientation is also the vertical orientation of the backpack. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Further features and advantages of some embodiments will become apparent upon reading the detailed description of the following nonlimiting examples, for an understanding of which reference will be made to the appended drawings, in which: 
         FIG. 1  shows a perspective view from the side and front of a backpack according to an exemplary embodiment of the presently disclosed subject matter, the pack being shown in a vertical position, the movable frame being in the stowed position; 
         FIG. 2  shows the backpack according to  FIG. 1  but with the movable frame in the deployed position; 
         FIG. 3  shows  FIG. 2  but in a side view and with the backpack placed vertically on the ground, in a balanced state; 
         FIG. 4  shows the backpack from  FIG. 3  in a similar view but with access to the inside of the storage envelope open, the shoulder straps of the backpack not being shown; 
         FIG. 5  shows the backpack from  FIG. 1  in a perspective view from the side and rear; 
         FIG. 6  shows the backpack from  FIG. 1  but without the shell or the storage envelope, and in a perspective view slightly from the side and the rear; 
         FIGS. 7 and 8  show the position of the strap in the deployed position of the movable frame, in a perspective view from the rear and a perspective view from the front, respectively; 
         FIGS. 9 and 10  show the position of the strap in the stowed position of the movable frame, in a perspective view from the rear and a perspective view from the front, respectively; 
         FIG. 11  shows an example of a slide of the backpack from  FIG. 1 ; 
         FIG. 12  shows a cross-sectional view of the slide from  FIG. 11 ; 
         FIG. 13  shows a side view of the shell of the backpack from  FIG. 1 ; 
         FIG. 14  shows the hinging of the movable frame to the shell of the backpack from  FIG. 1 ; 
         FIGS. 15 to 19  correspond to  FIGS. 6 to 10  but according to a variant embodiment; 
         FIG. 20  shows a backpack according to another exemplary embodiment but without the storage envelope or the shoulder straps, and in a perspective view slightly from the side and the front, the movable frame being stowed; 
         FIG. 21  shows the backpack from  FIG. 20  but without the shell or the storage envelope or the shoulder straps, and in a perspective view slightly from the side and the rear. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIG. 1  shows an exemplary embodiment of a backpack  1  according to the presently disclosed subject matter. 
     The backpack includes a storage envelope  2 , which forms the envelope that separates the outside of the backpack  1  from its inside, thereby defining a storage volume inside which various objects can be stored. 
     The backpack  1  includes shoulder straps  6  attached at one end to the top of the backpack and at the other end to the bottom of the latter, so as to allow a user to carry the backpack on his back, the shoulder straps  6  passing over his shoulders. 
     The backpack  1  may also include, as illustrated here, an abdominal belt that is designed to be closed around the user&#39;s waist and includes at least one closing strap  5 . 
     The backpack  1  illustrated includes a shell  3 . This shell  3  includes an upper portion forming a rigid cover  30 , which forms protection for the top of the storage envelope  2 . 
     In the example illustrated, the cover  30  covers the entire top of the storage envelope  2  and includes a generally flat surface. 
     This shell  3  also includes a lower portion, which forms protection for the rear of the storage envelope  2 . 
     The shell  3  is fastened immovably to the storage envelope  2 . The lower portion  31  is thus fixed with respect to the assembly of the storage envelope  2  and the cover  30 . This lower portion thus also forms a fixed frame  31 . 
     According to some embodiments, the shell  3  can be fastened to the envelope  2  so as not to be removable, for example by bonding, riveting, thermowelding or further techniques. Alternatively, the shell  3  can be fastened to the envelope  2  so as to be removable, for example by touch-and-close tapes, press studs, or clip-fasteners. 
     The backpack  1  also includes a movable frame  4  hinged to the cover  30 , in this example to the front edge  33  of the cover  30 , as can be seen in  FIG. 13 . 
     This movable frame  4  is formed, in this example, by a framework situated on the front of the storage envelope  2 . Therefore, when the user carries the backpack  1  on his back, this framework  4  is situated between his back and the storage envelope  2 . 
     To improve the comfort of wearing the backpack  1 , the framework  4  can include a stretched textile  41 , also referred to as a stretched back  41 , that is intended to come into contact with the user&#39;s back. This stretched back can be formed for example by netting. 
     The storage envelope  2  includes a bottom  21 . When the backpack  1  is placed vertically on the ground S, as illustrated in  FIG. 3 , this bottom  21  is in contact with the ground S. 
     As illustrated in  FIG. 2 , the movable frame  4  opens to a certain angle. 
     According to some embodiments, the movable frame  4  is able to move from a stowed position, particularly against the storage envelope  2 , as illustrated in  FIG. 1 , to a deployed position, illustrated in  FIG. 2 . 
     In particular, in the example illustrated, by virtue of its hinging, the movable frame passes from its stowed position against the front wall  23  of the storage envelope  2  to the deployed position, by being spaced apart from this front wall  23 , for example by being rotated about an axis situated at the top of the storage envelope  2 . 
     The deployed position allows better stability of the backpack  1  when placed in a vertical position on the ground S, as for example in  FIG. 3 . 
     The movable frame  4  has a lower bearing surface  42 , known as the movable lower bearing surface  42 , intended to come into contact with the ground S when the backpack is placed vertically on the ground S. Similarly, the shell  3 , and thus the fixed frame  31  formed by the lower portion of this shell  3 , includes a lower bearing surface  32 , known as the fixed lower bearing surface  32 , which is intended to be in contact with the ground S when the backpack is placed vertically. 
     Thus, when the backpack is placed vertically on the ground, with the movable frame  4  in the deployed position, the backpack  1  is maintained vertically and in a balanced state by its movable frame  4  and the fixed frame  31 . This balanced state is stabilized by the supports on the lower bearing surfaces  42  and  32 . When the movable frame  4  is in the deployed position, the movable lower bearing surface  42  is situated away from the storage envelope  2 , thereby increasing the stability of the backpack  1 . 
     The lower bearing surfaces  32 ,  42  are distributed around the bottom  21  of the storage envelope and, between one another, define an area greater than that of the bottom  21  of the storage envelope  2 , thereby improving stability. 
     Moreover, in some embodiments of the presently disclosed subject matter in which the fixed frame  31  is formed by a shell  3 , for example as illustrated, this shell can be in the form of a plate, in particular a nonflat plate, the edge face of this plate forming the fixed lower bearing surface  32 . 
     Similarly, when the movable frame is realized as a framework  4 , it is the lower strut of the framework  4  which can directly form the movable lower bearing surface  42 . 
     By being formed by an edge face and a strut of the framework, the lower bearing surfaces  42 ,  32  can adapt more easily to various irregularities of the ground that may be situated between these lower bearing surfaces. 
     The bottom  21  adapts to the ground S. 
     Once the backpack  1  has been placed vertically on the ground S, the panel formed by the outer surface  35  of the cover  30  can serve as a support for various objects and also serve as a seat for the user of the backpack. In such a case, the weight is transferred directly to the frames  4 ,  31 , then is transferred to the ground S by the lower bearing surfaces  42 ,  32 . 
     The backpack according to some embodiments, and in particular according to the example illustrated, is thus particularly suitable for hikes, particularly in hilly areas. In particular, it is suitable for professionals who work outdoors, such as paleontologists, entomologists, primatologists, geologists, etc. These professionals have to travel under the best or better conditions to research sites that are particularly difficult to access, while also transporting fragile equipment. 
     Generally, in cases in which the fixed frame  31  and the cover  30  are formed by a rigid shell  3 , the latter makes it possible to protect the sensitive material stored inside the storage envelope  2 , and if desired in this embodiment to move around in dense vegetation, limiting the risk of the backpack getting caught on plants. This shell  3  is also able to form a seat for the researcher, this shell  3  and the movable frame forming a seat, in particular once at the work site. This shell  3  can also serve as support for various devices, such as a camera, a laptop computer, a GPS antenna. 
     In particular in the example illustrated, the shell  3  and the movable frame are arranged in such a way that, in the deployed position, the cover  30  is horizontal when the backpack  1  is positioned on approximately horizontal ground. 
     The stretched back  41  improves walking comfort. 
     Moreover, the outer surface  35  of the shell  3  can be smooth in order to reduce the risk of catching on plants. 
     In order to make this sliding easier, the backpack  1  can include, as illustrated in  FIG. 5 , a curve  37  connecting the cover  30  and the fixed frame  31 . This curve  37  forms a transition between the cover  30  and the fixed frame  31 . In particular, the curve  37  allows sliding when the user moves along bent over, the branches first of all sliding over the cover  30  and then along the fixed frame  31 . 
     The shell  3  may also include lateral returns  38 ,  39 . These lateral returns  38 ,  39  are in this example portions of the cover  30  and of the fixed frame  31  and are inclined slightly downward for the cover  30  and inclined slightly forward for the fixed frame  31 . These lateral returns improve the sliding of branches over the shell, without catching on the sides of the storage envelope  2 . 
     The lateral returns  39  of the lower portion  31  also confer on the fixed lower bearing surface  32  the shape of an edge face that is curved or has segments forming an angle between one another. These lateral returns  39  thus generally surround the rear of the storage envelope  2 , thereby further improving the stability of the support on the fixed lower bearing surface  32 . 
     According to some embodiments, and as illustrated in  FIG. 5 , the transition between the lateral returns  39  of the lower portion  31  and the rest of the shell  3  can form a rib  36 , making it possible to further reinforce the shell  3 , and thus also to reinforce the support of the cover  30  when the backpack  1  is in a vertical position on the ground S. 
     In  FIG. 5 , given the orientation of the backpack  1 , only the lateral returns  38  and  39  of the cover and of the lower portion  31  that are situated on the left are visible. However, the same type of lateral returns may be present on the right-hand side of the storage envelope  2 . 
     The shell  3  can have, as in this example, a vertical plane of symmetry that is oriented from front to rear. 
     The shell  3  forms a single one-piece part, which is easier to produce but also makes it possible to protect the entire top and rear of the backpack. To this end, it can also have a shape allowing it to match the volume that the storage envelope  2  can have once full. The back and/or the top of the storage envelope  2  can also be pressed against the shell  3 , in particular by bonding. 
     However, according to further embodiments that are not shown, the cover and the fixed frame can be produced in separate parts. 
     According to further embodiments that are not shown, it is possible for the fixed frame not to form a plate entirely covering the back of the storage envelope. The fixed frame can include two rear legs, leaving an opening at the rear between these two legs, in order to provide access to the rear of the storage envelope. 
     According to some embodiments, and as illustrated in  FIGS. 3 and 4 , the storage envelope  2  can include flaps  24  for closing the sides of the storage envelope  2 . These 24 flaps open, as illustrated in  FIG. 4  in order to provide access to two access openings  25 ,  26  for accessing the inside of the storage envelope. 
     In this example, the openings are a left-hand access opening  25  and a right-hand access opening  26  arranged opposite one another, such that when the flaps  24  are open on both sides, the backpack  1  is open all the way through from the left-hand access opening  25  to the right-hand access opening  26 . This makes it possible to access all of the inside of the storage envelope  2  through the sides. 
     This makes it possible to rapidly access the contents of the backpack  1  while walking, but also when it is placed on the ground. 
     This is all the more advantageous in the case of the example illustrated, in which the shell  3  completely covers the top and rear of the storage envelope  2 . 
     The backpack  1  may also include partitions, which are fixed or removable, in particular by way of touch-and-close tapes, so as to divide the inside of the storage envelope  2  into compartments. 
     Thus, in the example illustrated in  FIG. 4 , horizontal partitions  28  are arranged so as to form three compartments inside the storage envelope  2 , each of these compartments being accessible from both sides of the backpack. 
     The flap(s)  24  can allow access to all of the compartments, as illustrated in  FIG. 4 . 
     The number of partitions is not limiting. 
     Division into compartments by way of horizontal partitions  28 , regardless of the number thereof, allows the backpack to form a rack once placed on the ground. It makes it easier to access the contents and to store them, in particular during professional expeditions. In order to improve this function, the horizontal partitions  28  can be rigid. For example, they may include a rigid core surrounded by a flexible material, such as a foam glued to this core, in order to protect the fragile materials. 
     The lowest horizontal partition  28  can be arranged at a distance from the bottom  21 , the access opening(s)  25 ,  26  being level with or above this horizontal partition. Thus, the storage envelope  2  does not have an access point between this partition and the bottom  21 . This makes it possible to protect objects from impacts, especially when the backpack is set down. 
     The flaps  24  may include flaplets  27  that open through one of these flaps  24  in order to access individual compartments. 
     In an embodiment that is not shown, the storage envelope may include a flap only on one side of the storage envelope. 
     The storage envelope  2  may also include a vertical partition, not shown, that extends from right to left behind the front wall  23  of the storage envelope  2 , for example in order to form a storage compartment for a laptop computer. 
     In general, the inside of the storage envelope  2  can be covered with a padded lining made in particular of foam. 
     According to embodiments that are not shown, instead of a flap, there are simply flaplets that open into each of the individual compartments. 
     The flaplets  27  and/or the flaps  24  can be opened using a zip fastener. 
     According to some embodiments, and as illustrated in  FIG. 4 , in order to improve the user&#39;s comfort, the backpack  1  includes an upper catch  44  and a lower catch  47 , which are situated at the top and the bottom of the framework  4 , respectively. The textile of the stretched back  41  is fastened between the upper catch  44  and the lower catch  47  so as to be stretched away from the framework  4 . 
     As can be seen in  FIG. 6 , the upper catch  44  and/or the lower catch can each be formed by a plate  45 ,  48  that is directly fixed to the framework  4  by screwing or riveting. Fastened to each plate  45 ,  48  is a pad  46 ,  49 . The catches  44 ,  47  protrude laterally beyond each side of the framework  4  with their plates  45 ,  48  and their pads  46 ,  49 . This gives the stretched back  41  a certain width. As here, the lower catch  47  can be wider than the upper catch  44 , giving the stretched back  41  a flared shape that widens toward the bottom. 
     For example, and as here, the stretched back can cover the pads  46 ,  49  in front of the latter, in order to stretch the textile away from the framework  4 . 
     According to some embodiments, and as illustrated, the shoulder straps  6  can be formed by a single part, which may have in its center an attachment  61 , in this case a textile tongue  61 , intended to be fastened to the rear of the stretched back  41  in order to improve comfort. In particular, it can be stitched to the stretched back  41  and/or to the pad  46  of the upper catch  44 . These shoulder straps can also be attached at the bottom to the storage envelope  2 . 
     The arrangement of the abdominal belt and the hinge of the movable frame  4  will now be described in detail. 
     According to some embodiments, and in particular in the example illustrated, this belt makes it possible not only to keep the backpack on the user at their abdomen but also to limit the opening angle of the movable frame  4  with respect to the front wall  23  of the storage envelope  2 . 
     According to some embodiments, in particular as illustrated in  FIG. 14 , this hinge can be formed by a sheet-metal plate  43  shaped into a trough shape. The tops of this trough include curved edges that are fastened to the front edge  33  of the cover  30  and under the latter, in particular by screwing, riveting or bonding, preferably by riveting. A horizontal upper strut of the framework  4  is accommodated in the trough between the bottom of this trough and the cover  30 . This horizontal upper strut is cylindrical, with an approximately circular cross section, and thus pivots about an axis parallel to its length inside the trough. In this way, a simple hinge of this framework  4  with respect to the cover  30  is formed. The framework  4  can, as here, be formed entirely of tubular parts. 
     Here, the belt includes an abdominal strap  5  that forms the right-hand side of the abdominal belt at one of its ends and the left-hand side at the other end. 
     In another embodiment of the presently disclosed subject matter that is not shown, the abdominal belt could include a right-hand abdominal strap and a left-hand abdominal strap. 
     Thus, as can be seen in  FIG. 6 , the abdominal strap  5  includes a first end  50  connected to a first closing fastener, in this case a fastening buckle  7 . The abdominal strap  5  then passes into an abdominal pad  11  such that, when the abdominal strap  5  is fastened, the latter comes into contact with the user&#39;s stomach, then passes through a slide  8  fastened to the front wall  23  of the storage envelope  2 , then passes around the framework  4 , passes again through a slide  8 , which is also fastened to the front wall  23  of the storage envelope  2 , then passes again through an abdominal pad  11  and ends at a second end  59 , which is not visible in  FIG. 6  but is visible in  FIG. 1 . This second end directly forms a closing fastener that is fastened and clamped by sliding in the fastening buckle  7 . 
     According to embodiments that are not shown, each end of the abdominal strap can be connected to a fastening buckle, the buckles being fastened to one another, at least one of the ends being able to slide with respect to the buckle that it carries in order to tighten the abdominal belt. 
     As illustrated in  FIGS. 11 and 12 , the slide  8  is a ring including an annular element  80  and a central strut  81 , extending parallel to the straight parts of the annular element and situated roughly midway between each of the straight parts of this annular element  80 . However, as can be seen in  FIG. 12 , which corresponds to a cross section of this slide  8  in a plane perpendicular to the central strut  81 , the central strut  81  is offset forward or downward in  FIG. 12 . 
     In some embodiments the annular element  80  may include a flat rear face  83  which is pressed against the front wall  23  of the storage envelope  2 . This rear face  83  is in contact with the storage envelope  2 , the offset of the central strut  81  allowing the strap to slide more easily between the storage envelope  2  and this central strut  81 , as can be seen in  FIGS. 6 to 10 . 
     The annular element  80  can be fastened to the storage envelope  2  by studs  82  extending from this rear face  83 . These studs  82  can be pressed into the front wall  23  of the storage envelope by thermowelding and/or hot riveting. In particular, the ring  8  and the front wall  23  of the storage envelope  2  can be made of thermoplastic polymer(s). 
     For example, this front wall  23  can be formed of one or more polymer fabrics or a textile formed by a fabric, such as polyethylene (PE) coated and/or impregnated with polyvinyl chloride (PVC). 
     The slide  8  can be formed from polypropylene (PP), acrylonitrile butadiene styrene (ABS), or a mixture of both. 
     On each side of the framework  4 , the abdominal strap  5  includes a first portion  51  that is defined between the fastening of the abdominal strap  5  to the framework  4  and a stop  53 . The abdominal strap  5  includes a second portion  52  that extends from this stop  53  and the corresponding end  50 ,  59  of the abdominal strap  5 , and which therefore passes through openings in the corresponding stomach pad  11 . 
     As shown in  FIGS. 7 to 10 , the first portion  51  of the abdominal strap  5  passes in front of a first lateral straight part of the annular element  80 , then passes in one direction through the ring between the central strut  81  and the annular element  80 , then between the central strut  81  and the front wall  23  of the storage envelope  2 , then passes in the other direction through the ring and between the central strut  81  and the annular element  80 , then reaches the framework  4  to which it is fastened, in this example by being clamped between the plate  48  of the lower catch  47  and the framework  4 . 
     According to some embodiments, and as illustrated, the backpack  1  may include an additional portion of strap  55 , which is separate from the abdominal strap  5  and arranged between the abdominal strap  5  and plate  48  of the lower catch  47 . For example, rivets can pass through the plate  48 , the additional portion of strap  55 , the abdominal strap  5  at the framework  4 , and the lateral struts of the framework  4  itself. 
     The ends of this additional portion of strap  55  can be stitched to the strap  5  on either side of the framework  4 .  FIG. 8  shows one of the ends  54  of the additional portion of strap  55  pressed against the abdominal strap  5  and stitched thereto. In this example, the stitching thus forms the stop  53 . 
     This end  54  of the additional portion of strap  55  is stitched in such a way that the central strut  81  is accommodated between the first portion  51  of the abdominal strap  5  and this additional portion of strap  55 . 
     As can be seen in  FIGS. 9 and 10 , when the movable frame  4  is in the stowed position, the first portion  51  of the abdominal strap  5  is distributed on either side of the central strut  81  of the ring  8 , the abdominal strap  5  being tight. When the user undoes the closing fasteners  7 ,  59 , he can loosen this strap  5  by spacing apart the framework  4  from the front wall  23  of the storage envelope  2 , the first portion  51  of abdominal strap  5  slides between the annular element  80  and the central strut  81  until the stitching  53  reaches the central strut  81 , as illustrated in  FIGS. 7 and 8 . At that time, the stitching  53  forms a stop, which limits the angular opening of the movable frame  4 . 
     Conversely, tightening the abdominal strap  5  makes it possible to stow the movable frame  4  against the storage envelope  2  again. When the abdominal strap  5  slides in the opposite direction between the central strut  81  and the annular element  80 , the stitching  53  moves away from the central strut  81 , as illustrated in  FIGS. 9 and 10 . 
     As a result, the abdominal strap  5  has a double function: tightening the storage envelope  2  around the user&#39;s waist and stowing the movable frame  4 . There is therefore a need for a single hand movement for these two functions. This is particularly useful in dirty, in particular muddy environments. Specifically, limiting the number of hand movements reduces the soiling of the backpack. 
     In another embodiment that is not shown, the hinge of the movable frame can include an elastic element designed such that the passage from the deployed position to the stowed position increases the stress thereon. As a result, it exerts a restoring force to the deployed position on the movable frame. Thus, all that is desired in this embodiment is to loosen the abdominal strap in order for the movable frame to move into the deployed position. Therefore, there is one fewer hand movement. This elastic element may be for example a torsion spring, notably with the coils wrapped around the upper strut of the framework, one of the ends of the spring being fastened to the framework and the other to the shell. 
     According to some embodiments, in order to reduce the risk of soiling of the stretched back  41 , the lower catch  47  can be arranged above and at a distance from the movable lower bearing surface  42 , as can be seen in  FIGS. 3 and 6 . For example, this distance may be between 20 and 50 millimeters (mm), in particular 40 millimeters. 
     Likewise, the stomach pads  11  can be stitched at a distance from the bottom  21 , in order to avoid touching the ground S. 
     Moreover, the framework  4 , the shell  3 , the stretched back  41  and the front wall  23  of the storage envelope  2  can be arranged such that, in the stowed position, the bottom  21  and the bottom of the framework  4  are at a distance from the stretched back  41 . This allows areas that are in contact with the ground when the backpack  1  is set down to come in contact with the walker&#39;s back when he carries the backpack  1  again. 
     According to some embodiments, and as illustrated, in order to avoid soiling, the flap  24  can be arranged, as here, at a distance from the bottom  21 . It can be designed to open around its entire perimeter, except for an upper portion which forms a hinge. For example, in  FIG. 4 , the zip fastener starts at the very top of the flap  24  and at the front, descends toward the rear, goes around the access opening  25 ,  26 , and then goes up to the top again, ending at a distance from its starting point, for example about halfway up the edge of the corresponding access opening  25 ,  26 . 
     The backpack  1  may include a removable accessory (not shown), formed by a plate including on one side clip-fasteners, such as studs, designed to be clip-fastened around the lower strut of the framework  4 . In this case, it is possible to clip-fasten this accessory in order to increase the area of contact of the movable frame  4  with the ground, this possibly being useful on soft, notably muddy terrain. 
     In addition, the bottom  21  can be reinforced, in particular lined with a waterproof layer, for example a textile coated with at least one polymer. This makes it possible to easily clean this bottom  21 . 
     In general, the entire storage envelope, or even the backpack as a whole, can be made of materials that are able to be wetted, or even washed with a water jet. 
     Of course, the embodiment illustrated is not limiting in terms of its dimensions. 
     However, by way of example, a few dimensions that are applicable, in particular to the exemplary embodiment illustrated, as shown in  FIG. 13 , may be mentioned. 
     For example, in order to form a good seat for the user of the backpack  1 , the length L 1  between the lower bearing surfaces  32  and  42  may be 357 mm for a flat surface level with the cover  30  having a length of 200 mm. This makes it possible to improve the stability on the ground by virtue of the difference between these two lengths L 1  and L 2 . 
     The movable frame  4  may have a length L 3 , from its hinge to the movable lower bearing surface  42 , of 405 mm. The opening angle β of the movable frame  4  in the deployed position may be 100°. 
     The height of the shell  3 , measured from the outer surface  35  of its cover  30  to the fixed lower bearing surface  32 , may be 400 mm. This allows a comfortable seat. 
     The curve  37  of the shell  3  can be designed such that a curve angle α is defined between a plane that includes the flat surface of the cover  30  and a plane passing through the part of the outer surface of the lower portion  31  of the shell  3 , this part being situated between the left-hand and right-hand lateral returns. The shape of the curve  37  from one of the planes to the other is continuous and regular. The curve angle may be 95°. 
     According to some embodiments, the cover  30  and/or the fixed frame  31 , or the shell  3 , can be made of a material selected from: aluminum, a polycarbonate (PC), a polypropylene filled with glass fibers or polymer material, ABS or PP. 
     For example, in the case of PC and filled PP, the shell  3  can be obtained by thermoforming. In the case of ABS and PP, it can be obtained by injection-molding. 
     More particularly, according to some embodiments, the shell  3  can be made of PC and/or have a thickness of between 3 and 8 millimeters (mm), in particular 4 mm. 
     The abdominal strap can be made for example of nylon or textile fiber. 
       FIGS. 15 to 19  illustrate a variant embodiment that differs from the backpack in  FIGS. 1 to 14  by way of its slide  108 . Since the other elements are unchanged, their references are retained and only the differences are described below. 
     According to this variant, the slide  108  is formed by a simple fabric loop. The loop includes a rear side  180  and a front side  181 . 
     The rear face  183  of the rear side  180  is flat and pressed against the front wall  23  of the storage envelope  2 . In particular, the rear side  180  can be stitched to the storage envelope  2 . 
     The slide  8  can be formed from the same material as that of the strap. 
     As in the preceding variant, the first portion  51  of the abdominal strap  5  is defined between the fastening of the abdominal strap  5  to the framework  4  and the stop  53 . However, in this case, this first portion  51  passes between the front face of the rear side  180  and the front side  181 . 
     The second portion  52  of the abdominal strap  5  extends, here too, from the stop  53  to the corresponding end of the abdominal strap  5 . 
     In this variant, too, the backpack can include an additional portion of strap  55 .  FIG. 17  shows one of the ends  54  of the additional portion of strap  55  pressed against the abdominal strap  5  and stitched thereto. In this example, the stitching thus forms the stop  53 . 
     Here, this end  54  of the additional portion of strap  55  is stitched in such a way that the front side  181  is accommodated between the first portion  51  of the abdominal strap  5  and this additional portion of strap  55 . 
     Thus, when the user loosens this strap  5  by spacing apart the framework  4  from the front wall  23  of the storage envelope  2 , the first portion  51  of abdominal strap  5  slides in the slide  8 , between the rear side  180  and the front side  181 , until the stitching  53  reaches the front side  181 , as illustrated in  FIGS. 16 and 17 . 
     Conversely, tightening the abdominal strap  5  makes it possible to stow the movable frame  4  against the storage envelope  2  again. The abdominal strap  5  then slides in the opposite direction, between the front side  181  and the rear side  180 , the stitching  53  moving away from the front side  181 , as illustrated in  FIGS. 18 and 19 . 
       FIGS. 20 and 21  illustrate another exemplary embodiment of a backpack according to the presently disclosed subject matter, this example having several additional variants. However, these variants can be applied independently of one another to the backpack according to some embodiments. The storage envelope  2  is not shown since it can be identical to that of the previous example. 
     The differences of these variants mainly relate to the movable frame  204 , in particular its fastening to the shell  203  and to the stretched back  241 . 
     Thus,  FIG. 20  illustrates second, third and fourth variants. 
     According to the second variant, the movable frame is formed by a U-shaped bar  204 . Thus, it includes a transverse part connecting the bottom ends of two lateral portions  204   a  and  204   b  of this U-shaped bar. 
     The top ends of these lateral portions  204   a  and  204   b  are hinged to the front edge  233  of the shell  203 . For example, two forked brackets  243  can be fastened to this front edge  233 , on each side of the cover  230 , in particular by screwing or riveting. The fork of each of these brackets  243  carries a pivot pin passing through the top end of the corresponding lateral portion  204   a ,  204   b  of the U-shaped bar from one side to the other. 
     According to the third variant, the bearing surface  242  can be covered with a layer  242 ′ of PVC, in order to protect the bottom of the movable frame from moisture, in particular mud. This layer  242 ′ can extend over part of the height of the movable frame  204 . 
     Similarly, according to the fourth variant, the bottom of the lower portion of the shell  203  may be fitted and/or bonded in a stiffener  233 . This stiffener  233  may, as illustrated, be formed by a bar with a U-shaped cross section and have a shape complementary to the lower edge of the shell  203 . The lower face of this stiffener  233  thus forms the fixed lower bearing surface  232  of the fixed frame  231 . This bar may be formed from a metal sheet. For example, it can have a length of about 330 mm. 
       FIG. 21  illustrates fifth and sixth variants. 
     According to the fifth variant, the upper and/or lower catch of the stretched back  241  at the top and/or bottom of the movable frame  204 , respectively, can include an upper catch strap  245   b  and/or a lower catch strap  248   b , respectively. Each catch strap  245   b ,  248   b  is fastened to the rear of a corresponding pad, namely a top pad  246  or a bottom pad  249 , so as to clamp the top of the movable frame  204  between the corresponding pad  246 ,  249  and the corresponding catch strap  245   b ,  248   b.    
     The upper and/or lower catch may also include a spacer  245   a ,  248   a . This spacer  245   a ,  248   a  has a width and a length allowing it to create housings  245   d ,  248   d  for the lateral portions  204   a ,  204   b  of the movable frame  204  on each side of the corresponding spacer  245   a ,  248   a . This type of housing  245   d ,  248   d  can also be used for the lateral bars of the framework  4  of the example illustrated in  FIG. 6 or 15 . 
     The spacer  245   a ,  248   a  can be formed by a pouch, the sides of which are stitched to form a spacer between the pad  246 ,  249  and the catch strap  245   b ,  248   b.    
     The upper catch strap  245   b  can be stitched directly to the top pad  246 . The spacer  245   a  may include a tab  245   c  protruding beyond the rear of the catch strap  245   b . The shoulder straps may be fastened to this tab  245   c . For example, the shoulder straps can include a textile tongue such as the one  61  in  FIG. 6 , this tongue being fastened directly to the tab  245   c , for example by press studs  245   e.    
     The lower catch strap  248   b  can be stitched to an abdominal strap  205 , itself stitched to an additional portion of strap  255 , itself stitched to the bottom pad  249 . These straps  248   b ,  205 , this portion of strap  255  and this bottom pad  249  can be stitched together by one and the same seam. 
     The additional portion of strap  255  is arranged with the abdominal strap  205  in the same way as described with reference to  FIGS. 1 to 19 , and may engage with a slide, such as the slides  8  or  108  in  FIGS. 11 and 12 or 16 to 19 . 
     According to some embodiments, in order to be more resistant, the straps and/or the spacers can be made of textile covered, coated or impregnated with polymer, for example a PE textile coated with PVC. 
     The shoulder straps can also include an outer layer made of these materials. 
     The pads may include casings formed of the same materials and containing a foam. They may include a reinforcement plate bearing against the movable frame. 
     The bottom of the storage envelope can also be reinforced by straps stitched on the inside or outside. 
     Generally, the movable frame can be made of steel.