BACKGROUND
1. Field of the Invention
This invention relates to flexible frames for backpacks and the like.
2. Description of the Prior Art
Flexible backpack frames are known, one example being that described in U.S. patent application Ser. No. 11/141,354 (Pub. No. US 2006/0266781 A1), hereinafter referred to as the “prior backpack frame.”
SUMMARY OF THE INVENTION
Among the objectives of the present invention is the strategic narrowing of the prior backpack frame to thereby accommodate increased movement of the wearer's shoulders, scapulas and forearms, thus facilitating backward and sideward reaching.
Another objective of the present invention is to achieve the aforesaid narrowing while maximizing the useful load bearing area of the backpack frame.
Still another objective of the present invention is to increase load stabilization by minimizing the degree to which the load will sway from side to side as the wearer walks or runs.
These and other objectives, features, and advantages of the present invention will now be described in further detail with reference to the accompanying drawings, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a back perspective view of a backpack frame in accordance with the present invention;
FIG. 2 is a back plan view of the backpack frame;
FIG. 3 is a longitudinal sectional view of the backpack frame taken along line 3-3 of FIG. 2;
FIG. 4 is a side view of the backpack frame looking from left to right as viewed in FIG. 2;
FIGS. 5 and 6 are, respectively, top and bottom end views of the backpack frame;
FIG. 7 is a cross sectional view of the backpack frame taken along line 7-7 of FIG. 2; and
FIG. 8 is a front perspective view of the backpack frame, carrying a load, and showing the addition of control straps to minimize flexure.
DETAILED DESCRIPTION
With reference initially to FIG. 1, a backpack frame 10 in accordance with the present invention comprises an integral structure having a “front side” and a “back side”. The backpack frame has generally parallel base and top sections 12, 14 extending transversely across and spaced one from the other along a frame center line “X”. Side rails 16 are arranged on opposite sides of the center line to connect the base section 12 to the top section 14. A stabilizing rib 18 interconnects the side rails and extends transversely across the center line at an intermediate location between the base and top sections 12, 14. The side rails 16 converge inwardly from the base section 12 towards the center line X to the stabilizing rib 18, and diverge outwardly from the stabilizing rib and away from the center line to the top section 14.
With reference additionally to FIG. 6, it will be seen that the base section 12 has a substantially flat central area 12a with end segments 12b curving forwardly towards the front side of the backpack frame.
As shown by the radius “r1” in FIG. 5, the top section 14 has a forwardly concave central area 14a with end segments 14b also curving forwardly towards the front side of the backpack frame. Additionally, as shown by the radius “r2” in FIG. 3, the top section 14 is longitudinally concave, and as shown by the radius “r3” in FIG. 2, the upper edge of the top section is concave, resulting in a gradual tapering from either end 14b towards the center line X.
As can be best seen in FIG. 7, the stabilizing rib 18 has a central area 18a with end segments 18b that project laterally from the side rails 16 and curve rearwardly towards the back side of the backpack frame. The central area 18a may either be substantially flat, as shown, or slightly forwardly concave.
When the backpack frame is subjected to the torsional forces “F” depicted in FIG. 1, these forces tend to cancel each other out at a transverse axis “Y” hereinafter referred to as the “torsion flex node”. The stabilizing rib 18 is preferably located at or slightly above the torsion flex node, i.e., between the top section 14 and the torsion flex node.
As can best be seen in FIG. 2, the bottom edge of top section 14 and the top and bottom edges of the stabilizing rib 18 at their respective junctures with the inner and outer edges of the side rails 16 define concavities having radii r4 selected to distribute rather than concentrate torsional stresses, while also controlling the extent of twist by resisting torque. Similar concavities are defined at the juncture between the interior edges of the side rails 16 and the top edge of the base section 12. The radii r4 can range from 25 to 75% of the width “w” of the side rails, with 30 to 70% of the width w being preferable, and with 34 to 56% of the width w being most preferable.
As can best be seen in FIGS. 3 and 4, the intermediate portion of the backpack frame between the base and top sections 12, 14 defines a concavity facing the front side.
Optionally, as shown in FIG. 8, control straps 20 may be applied to the frame on opposite sides of the center line X. The control straps are woven through strategically placed slots 22 at the upper ends of the side rails 16 and the top section 14, and are passed downwardly across the back side of the stabilizing rib 18 and through openings 24 in the base section 12.
The laterally inward contour of the side rails 16 coupled with rearward curvature of the end segments 18b of the stabilizing rib 18 coact to provide increased room for the wearer's shoulders, scapulas and forearms to move, thereby facilitating backward and sideward reaching. This is particularly advantageous when the wearer is in a prone position.
The configuration and positioning of the stabilizing rib 18 provides additional significant advantages. More particularly the laterally projecting end segments 18b provide a wider base for stabilizing loads. The rearward curvature of the end segments 18b provide a functional cradle for the load as well as a structurally sound stabilizing support away from the wearer's back. By locating the stabilizing rib 18 approximately at the torsion flex node, lateral load shifting is minimized as the wearer walks or runs. Positioning the stabilizing rib slightly above the torsion flex node assists in keeping the load center of gravity closer to that of the wearer's body.
The tapered configuration of the top section 14 allows it to twist in relationship to the stabilizing rib 18 to facilitate walking while maintaining sufficient rigidity to stabilize the load. The dual concavity of the top section shown by radii r1 and r2 further assists in accommodating twisting while providing adequate rigidity. Of particular significance are the edge concavities with radii r4 which distribute torsional stresses while additionally controlling the extent of permissible twist. As the top section curves around the wearer's scapulas and progressively curves over the wearer's shoulders, this dual curvature resists any tendency of the load to peel the frame away from the wearer's back.
The optional flex control straps 20 shown in FIG. 8 serve to limit the maximum extent to which the frame can be flexed forward or backward, thus safeguarding the integrity of the frame when it is exposed to catastrophic impacts, excessive loading or intentional abuse.
Patent Application
20080149677
