Pack frame

[57] ABSTRACT

A lightweight pack frame constructed of rigid polyvinyl chloride or like material including in one embodiment a molded U-shaped major support member, the legs of the “U” being joined by a curved, transverse extending support member which is adjustably mounted thereon to allow the size of the pack frame to be changed. A pair of flexible rods are end mounted to extend between the lower portion of the U-shaped major support member and the transverse support member such that they are bowed outwardly from the plane of the U-shaped support member to springingly hold a pack bag mounted on the frame away from the wearer’s back.

Claims, 9 Drawing Figures

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Patented May 22, 1973

3,734,366

Sheets-Sheet 1

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Patented May 22, 1973

3,734,366

Sheets-Sheet 2

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3,734,366

PACK FRAME

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to pack frames used to assist in the carrying of a load on a wearer’s back, and in particular, to lightweight, flexible pack frames suitable for recreational back packing.

2. Description of the Prior Art

Wooden pack frames comprising a pair of longitudinal supports interconnected by fixed transversely extending dowels are known. Pack frames of this type are generally quite heavy and this factor coupled with their rigidness and consequent failure to “give” in response to movements of the wearer make them less than satisfactory for use on long hikes or when carrying heavy loads. Additionally, pack frames of this type generally have no provision for maintaining the pack bag mounted on the pack frame away from the wearer’s back, consequently often allowing hard articles within the bag to dig into the back of the wearer.

Lightweight aluminum pack frames have substantially displaced wooden frames for use in recreational back packing, but the design of these frames has remained basically similar to the design of wooden frames in that generally a pair of longitudinally extending rods , are interconnected by a plurality of curved transverse rods welded or otherwise fixedly mounted therebetween. In some designs of this type pack, a pair of small diameter metal rods are threaded longitudinally through the central portions of the lateral supports to provide additional rigidity. The pack bag is thus held away from the pack frame wearer’s back by means of the web of longitudinal and transverse supports between the major longitudinal supports. While the lightweight nature of the aluminum tubing used in the construction of this type frame inherently provides a degree of flexure to the frame, frames of this type are easily bent or broken when dropped or otherwise heavily stressed.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a pack frame constructed of extruded plastic tubing material such as rigid polyvinyl chloride. In one embodiment, a length of polyvinyl chloride is molded to a substantially Ushape, with the legs of the U being curved to a flattened S-shape along their length. A single transverse support comprising a curved hollow tube having a pair of fittings including cylindrical portions extending transverse the tube is mounted on the legs of the U-shaped member near the open end of the U by sliding and fastening the cylindrical portions of the fittings onto the legs of the U. The transverse support may be mounted at selected points along the length of the legs to vary the operative vertical length of the frame to allow its comfortable use by wearers of differing size. A pair of flexible rods are end mounted to extend between the transverse support and the U-shaped support such that they are bowed outwardly from the plane of the pack frame to springingly hold a pack bag mounted thereon away from the back of the wearer.

The instant invention thus discloses a pack frame which maintains the pack bag away from the wearer’s back in a novel manner which is simple to construct, requires a small number of inexpensive easily fabri cated component parts, is size adjustable, and is more flexible and more durable than known pack frames.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a typical pack frame constructed according to the instant invention.

FIG. 2 is a section view along lines 2—2 of FIG. 1, including a pack bag shown in dashed line on the back of a wearer.

FIG. 3 is a section view along lines 3—3 of FIG. 1. FIG. 4 is a section view along lines 4—4 of FIG. 1. FIG. 5 is a perspective view of a typical pack frame constructed according to the instant invention, including a pack bag shown in dashed line mounted thereon.

FIG. 6 is a diagrammatic elevation view of a second typical embodiment of the pack frame of the instant invention wherein the pair of flexible rods are mounted to extend between the opposite legs of the U-shaped support member.

FIG. 7 is a diagrammatic elevation view of a third typical embodiment of the pack frame of the instant invention wherein the pair of flexible rods are bowed between spaced mounting points on each of the legs of the U-shaped support member.

FIG. 8 is a diagrammatic elevation view of a fourth typical embodiment of the instant invention wherein the longitudinal support members comprise a pair of laterally spaced tube members interconnected by a vertically spaced pair of transverse supports.

FIG. 9 is a perspective view of a portion of the pack frame of the instant invention including a height adjustable auxiliary transverse member mounted thereon.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially to FIG. 1, a pack frame 10 is illustrated, basically comprising a U-shaped major support member 12 including leg portions 14 and 16 and curved base portion 18. Transverse support 20 is connected between legs 14 and 16 near the open end of the U-shaped member by means of fittings 22, which fittings include tubular recesses 24 in which member 20 is end mounted and hollow cylindrical portions 26 which are slidable on legs 14 and 16 and mountable at a selected position by means of pins 27 in a manner to be described more completely with reference to FIG. 3. Flexible rods 28 and 30 are end mounted in cooperatingly sized holes 32 and 34 in transverse support 20 and legs 14 and 16 respectively. Flexible rods 28 and 30 are bowed prior to their mounting in holes 32 and 34, and as best seen in FIG. 2, these rods remain bowed after mounting such that they act to hold pack bag 36 away from the back of the wearer. It will be understood that in FIG. 2, flexible rods 28 and 30 are shown substantially in the position that they assume upon mounting, and that these rods are compressed a portion of the distance toward the back of the wearer when pack bag 36 is loaded thereby allowing the load to be carried essentially vertically with the center of gravity of the pack.

Conventional shoulder straps 38 are mounted on the pack frame to extend between pin mounts 40 on transverse rod 20 and pin mounts adjacent bottom portion 18 of the U-shaped support frame. The pin mounts illustrated in FIG. 1, comprise a pin member which is insertable through aligned holes extending through the tubular pack frame at selected points and held therein

3,734,366 by means of a wire clip inserted through a hole in the shank of the pin.

Referring now to FIG. 3, a second form of pin comprising a head portion 44 and a split shank portion 46 having ridge portions 48 designed to prevent inadvertent or unintentional removal of the pin is disclosed. It will be understood that this pin fastener may be satisfactorily constructed from various plastic materials, including those from which the frame components themselves are constructed.

Conventional pads 50 are positioned at desired locations longitudinally along legs 14 and 16 and held thereon by means of buckles 52 or the like to cushion legs 14 and 16. As is best seen in FIG. 2, legs 14 and 16 are molded to what may be described as a flattened S-shape which conforms generally to the spine of a wearer. Pads 50 are generally positioned at the most likely points of contact between the wearer and legs 14 and 16, usually in the small of the wearer’s back and slightly below the shoulders as illustrated.

Referring now to FIG. 3, the means by which transverse support rod 20 may be adjusted to selected longitudinal positions on legs 14 and 16 is disclosed. As shown, leg 14, and leg 16 also although not shown, includes a plurality of aligned holes 52,54 and 56 extending therethrough and longitudinally spaced therealong. It has been found that three sets of holes spaced over a distance of three inches provides a range of adjustment sufficient for most users. Cylindrical portion 26 of fitting 22 includes a pair of aligned holes 58 having substantially the same diameter as holes 52, 54 and 56 in leg 14 and suitable for receiving the fastening pin. It will be understood that upon removal of the fastening pins, fittings 22 may be moved upwardly or downwardly on leg 14 until holes 58 are aligned with one of the sets of holes 52, 54 and 56 as desired, at which time the connecting pin may be inserted. This construction provides easy adjustment as well as ease of original fabrication.

Referring now to FIG. 4, the mounting of flexible rod 30 in a cooperatingly sized hole 32 in transverse rod 20 is disclosed. During fabrication, one end of the flexible rod is merely inserted in one of the holes 32 or 34, and the rod bowed outwardly until the free end may be inserted in the remaining hole. As illustrated, rod 30 extends through hole 32 and abuts against the internal wall of tube 20 opposite thereto, and it will be understood that the compression force applied to bow rods 28 and 30 during fabrication of the pack frame maintains these rods firmly in holes 32 and 34. FIG. 4 discloses rod 30 to be constructed of thick walled hollow tubing, and while this configuration is preferred, a solid flexible rod may be substituted therefor with little additional pack frame weight gain. As illustrated, holes 32 are drilled through one wall of tube 20 on a line radial to the center line of the tube but at an angle to a vertical plane bisecting the tube longitudinally.

Referring now to FIG. 5, it will be seen that transverse support member 20 and the lower portion 18 of the U-shaped major support member are curved to generally correspond to the curve of the wearer’s back and waist or hips respectively, thus preventing shifting of the pack from side to side during climbing. Transversely extending members 18 and 20 impart a degree of lateral stability to legs 14 and 16, however, when bag 36 is heavily loaded the central portions of legs 14 and 16 tend to be bowed laterally outward. Pads 50 may be tightened to the point where they tend to draw legs 14 and 16 inwardly to counteract the loading force of the bag.

As illustrated in FIG. 5, legs 14 and 16 are provided with vertically spaced sets of holes 60, 62, 64 and 66 in addition to the holes provided for vertical adjustment of transverse member 20. Pack bag 36 is mounted on the pack frame by means of pins 27 which extend through appropriately sized grommets on the rear portion of the pack bag and thence through the three uppermost sets of holes 60, 62 and 64. While it is usually preferred to carry a pack bag high on a pack frame in order that the weight of the bag is thrown onto the wearer’s shoulders rather than the lower portion of the wearer’s back, it will be understood that the pack bag may also be mounted in a similar manner on sets of holes 62, 64 and 66 where it is desired to fasten additional materials to the top portion of the pack frame, such as when using height adjustable transverse support 68 discussed hereafter with reference to FIG. 9.

A conventional pack belt 70 is shown mounted on the pack frame in holes 66 by means of pins 27. As is known, belts of this type may be used to lift the weight of the pack onto the wearer’s hips and thus, at least partially, off of the wearer’s shoulders to increase the backpackers comfort during long hikes.

Referring now to FIG. 6, a second embodiment of the pack frame of the instant invention is disclosed wherein flexible rods 28 and 30 are bent to extend between holes 34 in the lower portions of legs 14 and 16 and holes 72 in the upper portions of legs 14 and 16 just below transverse support 20. It will be understood that in this configuration, flexible rods 28 and 30 are bowed laterally outward from the plane of the pack frame to hold a pack bag mounted thereon away from the wearer’s back in the same manner disclosed above with reference to FIG. 2.

FIG. 7 discloses still another embodiment of the instant invention wherein each of the flexible rods 28 and 30 are mounted in holes 34 in legs 14 and 16 and then bent in a semicircular configuration such that the distal end of each rod is mounted in hole 72 on the same leg 14 or 16 of the pack frame.

Referring now to FIG. 8, an additional embodiment of the instant invention wherein the pack frame comprises a pair of individual vertical support members 74 and 76 interconnected by a vertically spaced pair of lateral support members 20 and 78, is illustrated. While not shown in this view, it will be understood that legs 74 and 76 may be curved along their length to the flattened S-shape of legs 14 and 16. Flexible rods 28 and 30 are shown bowed in the configuration of FIG. 5, but it will be understood that the configurations of FIGS. 6 and 7 may also be used in this configuration. Further, other curvatures of rods 28 and 30 capable of satisfactorily carrying out the purpose of maintaining the pack bag away from the wearer’s back and usable with either of the embodiments of FIGS. 1 or 8 are considered to be within the scope of this invention.

As has been mentioned briefly hereabove, transverse rod 20, and also transverse rod 78, are mounted endwise in tubular recesses 24 in fittings 22. Members 20 and 78 are held within recesses 24 by means of regular thermosetting glue or plastic cement of a type suitable for use with the plastic material chosen to construct the pack frame.

3,734,366

While it has been found that a standard rigid polyvinyl chloride tube material, preferably of the schedule 40 type 2 class is most satisfactory for use in constructing the pack frames of the instant invention from the standpoint of both ruggedness and low cost, other materials such as ABS which has an attractive high gloss surface luster and is available in a wide variety of colors, as well as a tough but flexible polyethylene may also be used. The difficulty of gluing polyethylene thereby requiring the use of welding or machine fastening to join the separate members of the frame is, however, a disadvantage of this material. A polycarbonate material such as that sold under the trademark Lexan which resists deformation under long-term loading as well as having a high surface gloss and good temperature characteristics may also be most satisfactorily used, however the high cost of this material is a disadvantage from the marketing point of view. A polyvinyl chloride having a specific gravity of approximately 1.5, a tensile strength between 8,000 and 10,000 psi, an impact strength of about 15 ft. Ibs./in. notch and a hardness of about 83 Shore D has proven very satisfactory in constructing pack frames made according to this invention.

One advantage of all of the above materials for use in construction of a pack frame, is that their resistance to permanent deformation is much greater than that of the presently used aluminum thereby providing a pack frame having substantially the same weight as aluminum but which is significantly more durable. One frame constructed according to the teachings of the instant invention out of the above described rigid polyvinyl chloride has been loaded with a 40 pound pack bag and dropped repeatedly at a variety of angles from a height of 6 feet without suffering any damage. Additionally, frames constructed of the above materials will flex and twist with the wearer thus making these frames substantially more comfortable than previously known pack frames, particularly those capable of being constructed at the relatively low cost of the instant pack frame.

Referring now to FIG. 9, an accessory transverse support rod 68, whereby the size and consequent load carrying ability of the instant pack frame may be increased is disclosed. Curved transverse support 68 includes a pair of leg portions 80 and 82 which are sized to be insertable within the hollow legs 14 and 16 of the pack frame respectively after removal of end snap caps 84 (FIG. 5). As illustrated, transverse member 68 may be disposed in a first downward position wherein legs 80 and 82 are positioned substantially entirely within the top portion of legs 14 and 16 and in this position member 68 primarily acts to increase the transverse rigidity of the pack as may be desired, for example, when carrying exceptionally heavy loads. Transverse member 68 is held in position by means of pins 27 which extend through holes 60 in pack frame legs 14 and 16 and through cooperating aligned holes 86 in legs 80 and 82. To extend the vertical length of the pack frame, transverse member 68 may be moved upwardly such that holes on the lower portions of legs 80 and 82 may be pinned through holes 60 as shown in dotted line in FIG. 9. In this configuration, a sleeping bag or the like may be carried on top of a pack bag mounted as shown in FIG. 5.

In one embodiment of the instant invention, a section of rigid polyvinyl chloride tubing having a length of 76 % inches and an inside diameter of approximately five6 eighths of an inch was heat molded in a jig to the Ushape disclosed in FIG. 5. Prior to heat molding, a piece of rope was inserted within the hollow tubing to prevent collapse of the tube during heating. In like manner, a 13 inch length of tubing of like diameter was molded to form transverse support member 20. Member 20 was then glued within recesses 24 of standard fittings 22 and this element was slipped over the ends of legs 14 and 16 and fastened through one of the sets of holes 52, 54 or 56 in the manner discussed heretofore. These holes, as well as sets of holes 60, 62,64 and 66 may have a diameter of one-fourth to threesixteenths of an inch and may be formed in a conventional manner such as through the use of a set of ganged drills. Thick walled flexible tubing material having a length of 25 % inches and a % inch outside diameter was then mounted in correspondingly sized holes 32 and 34 and bowed to extend laterally outward from the plane of the pack frame to hold a pack bag mounted thereon away from the wearer’s back.

The invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein.