fig1 is a perspective view of a backpack frame , generally indicated at 10 , with two shoulder straps 12 , 14 and a waist belt 16 installed , and fig2 is an elevational view of the backpack frame 10 in isolation . the backpack frame 10 illustrated in these figures and others is one of the frames described in u . s . patent application publication no . 2013 / 0221051 , the entire contents of which are incorporated by reference in their entirety . this frame 10 is a unitary , resin - impregnated structure made of carbon fiber , although the general construction of the frame is not critical in all embodiments of the invention , so long as the frame in question has the basic features described here . relevant to the process of attaching and adjusting the shoulder straps 12 , 14 , the frame 10 has two generally vertical tracks 18 , 20 that are sloped slightly inwardly as they extend downwardly . the tracks 18 , 20 are fully open and go through the thickness of the frame 10 . these tracks 18 , 20 provide adjustable points of connection to the frame 10 for the two shoulder straps 12 , 14 , as shown in fig1 . as shown in fig1 and in the exploded perspective view of fig3 , each shoulder strap 12 , 14 has a cam - fastener 22 sewn into it . the top of the cam - fastener 22 is a generally rectangular bar 24 that , when installed in each strap 12 , 14 extends parallel to the width of the strap 12 , 14 . the bar 24 is also longer than the width of the tracks 18 , 20 . the rectangular bar 24 is connected at its center to a post or neck 26 , which is , in turn , connected to a base 28 . the base 28 of the cam - fastener 22 is at least about as wide as the bar 24 itself , and in the illustrated embodiment , is a round disc . in general , the cam - fastener 22 should be made of a lightweight but rigid material , such as abs plastic [ correct ? ], such that it can sustain the loads carried by the backpack . in other embodiments , the projecting portion of the cam - fastener 22 need not be a bar 24 ; rather , any non - uniform shape with at least one dimension wider than the width of the tracks 18 , 20 . the size and area of the base 28 and rectangular bar 24 are sufficient to distribute the load somewhat so as to avoid causing failure of the stitching or other materials in the straps 12 , 14 or a failure of the area around the tracks 18 , 20 . typically , the base 28 is sewn or otherwise fixed into its strap 12 , 14 , for example , with adhesives . the process of connecting the straps 12 , 14 to the frame 10 is illustrated in the sequential elevational views of fig4 - 5 . to connect one of the straps 12 , 14 to the frame 10 , the user places the strap generally perpendicular to its use position , so that the length of the rectangular bar 24 is parallel with the track 18 , 20 , and inserts the bar 24 through the track 18 , 20 before rotating the strap 12 , 14 upright into its use position , as illustrated in fig5 . in the use position illustrated in fig1 , the rectangular bar 24 is perpendicular to the track 18 , 20 so that it cannot pull out of the track 18 , 20 . fig6 is a perspective view of the frame 10 and one strap 14 , illustrating the opposite side of the frame 10 . the cam - fastener 22 provides a sliding connection between the strap 12 , 14 and the frame 10 and prevents pull out in the normal direction , i . e ., the direction perpendicular to the frame . in order to keep the straps 12 , 14 in a particular vertical position along the tracks 18 , 20 , the frame 10 and straps 12 , 14 use complementary patches of hook - and - loop fastener . more specifically , each strap 12 , 14 has a patch 30 of hook - and - loop fastener below the cam - fastener 22 . a complementary expanse 32 of hook - and - loop fastener is provided in the center of the frame 10 , below the tracks 18 , 20 on the side of the frame 10 that faces the straps 12 , 14 . the present inventors have found that when fully engaged , hook - and - loop fastener has sufficient strength in shear to fix the position of the straps 12 , 14 vertically . moreover , by providing a relatively long swath of hook - and - loop fastener , the user can adjust the vertical position of the straps 12 , 14 continuously , with each of the straps 12 , 14 in contact with a portion of the hook - and - loop fastener 30 , 32 . thus , as shown in the perspective view of fig7 , a single strap 14 can assume a variety of positions , labeled in fig7 as a , b , and c . as those of skill in the art will note , the attachment mechanism described above attaches the upper padded shoulder and chest portion 34 of each strap 12 , 14 to the frame 10 . in order to function successfully as a strap , the straps 12 , 14 must also be connected or coupled to the frame 10 at their respective lower edges as well . there are a number of potential ways of doing this . because the lower portions of the straps 12 , 14 are load - bearing but not necessarily body - contacting , they generally do not need to be padded along their entire lengths . for that reason , it is generally sufficient to connect the padded upper portion 34 of each strap 12 , 14 to a piece of webbing to act as a lower portion . the webbing 36 ( best seen in fig1 ) may be , for example , 1 inch webbing . this connection may be by means of a buckle 38 sewn to the bottom of the upper portion 34 of each strap if no waist belt 16 is provided , the webbing 36 that serves as the lower portion of the strap 12 , 14 may simply terminate by attaching to one of a number of small slots 40 that are provided in the frame 10 , or to slots that are specifically provided for that purpose . however , in the illustrated embodiment , the webbing 36 that serves as the lower portion of the straps 12 , 14 attaches and is sewn into the waist belt 16 . as shown in the exploded view of fig3 , the waist belt 16 has a large pocket 42 . the frame 10 of the illustrated embodiment terminates in a lower , rounded , generally u - shaped tongue 44 , and the tongue 44 slips into the pocket 42 . the buckle 38 can be used to lengthen or shorten the effective length of the webbing 36 to an appropriate length based on the selected vertical position of the upper portion 34 of the straps 12 , 14 , and any excess length can be tied off . generally , the webbing 36 has a length in excess of the minimum required , to provide enough length to go through the buckle 38 and allow for adjustment . while the invention has been described with respect to certain embodiments , the embodiments are intended to be exemplary , rather than limiting . modifications and changes may be made within the scope of the invention , which is defined by the appended claims .
an adjustable shoulder strap attachment assembly is disclosed , as are methods for adjustably attaching shoulder straps to a backpack frame . the backpack frame has a pair of generally vertically - oriented tracks . each strap has a cam - fastener with at least one dimension greater than the width of one of the tracks . to secure a strap to the backpack frame , the cam - fastener is inserted into the track and rotated into its use position . a desired vertical position of the strap is selected , and the strap is secured by using hook - and - loop fastener between the backpack frame and the strap .