Patent Application
20170291236
A saw is a very useful tool for people working or recreating in the wilderness. Trees, branches, and deadfalls may be cut for firewood, to reduce the risk of wildfire or construct fire breaks, to construct shelter, especially in an emergency, or to clear a trail, and thus are often used by campers, soldiers, firefighters, search and rescue teams, and forest workers. Hunters quartering game for transport also find saws convenient for rapidly cutting bone. However, saws suitable for use in a less remote environment have numerous problems when they must be transported long distances on foot. Most notably, they are both bulky and heavy, and the exposed teeth can cause damage to other items being carried, or injury to the user, if not handled carefully. These problems are exaggerated if multiple saws are carried for multiple purposes.
Various solutions have been attempted but have rendered unsatisfactory results. Folding saws that resemble large pocket knives are limited in size and stiffness of blade. They are necessarily heavier than regular saws of comparable size due to large handles into which the blade folds. Because American saws typically cut on the push stroke, thin, lightweight blades cannot be easily used alone. Nor can a standard saw be rolled up to save space, both because it is thicker and because it would be useless if curved. Thicker, stiffer saw blades make a larger kerf, removing more material, and therefore require more effort to operate. Wire saws do roll up compactly and have a narrow kerf, but are tricky to pack and unpack because of a tendency to tangle, and are relatively prone to breakage on the trail, making them more suitable for emergencies than regular use.
A bow saw, such as a coping saw or hacksaw, can solve some of these problems. Because the blades are held in tension by the bow, they can be thin and lightweight, allowing different blades for different jobs (for instance, wood, bone, and metal) to be carried easily. Blades can be coiled for compact packing because the bow will pull them straight in use, and they are also typically stronger than wire saws. The bow can be designed exclusively for strength without any concern for the effect its thickness will have on the kerf or ease of use.
The major obstacle to the use of bow saws in a backcountry environment is their size and weight. The handle and bow typically have dimensions similar to a small handsaw, which negates many possible advantages. What is needed, then, is a bow saw that can be made compact for transport yet still be sturdy enough for aggressive use and large enough to perform a wide variety of jobs.
A modular bow saw.
A bayonet mount, best shown in
The female half 20 of a bayonet mount comprises a post-clearance hole 28 centered about an axis 30, a plurality of post-extension-clearance holes 32, and a post-extension-mating surface 34.
In use, the axes 24 and 30 are aligned with one another. The male and female halves 18 and 20 may then be rotated about their mutual axis 24, 30 until the post extensions 26 are aligned with the post-extension-clearance holes 32, as best shown in
As is typical in the art of bow saws, the blade 40 is held in place by tension. This tension is provided by a tensioning mechanism 42, best shown in
As depicted in
When assembled, the bow 12 and handle 10 lie substantially in plane 11. In a preferred embodiment, the axes 24, 30 are substantially perpendicular to this plane 11. It will be appreciated that when tension is applied to the blade 40, a torque is exerted about the axis 30, 24 of the bayonet mount. It is therefore necessary to stop the mutual rotation of the both halves of the bayonet mount at a chosen point. This may be achieved by various means, including limiting extent of the post-extension-mating surface 34 so that the post extensions 26 contact an impediment to rotation. However, that method leaves the relatively thin post extensions 26 to bear the force of rotation, which in the case of a bow saw can be substantial. Therefore, a preferred embodiment features a shelf 36 on the male half 18 of the bayonet mount and a corresponding shelf 38 on the female half of the bayonet mount. A most preferred embodiment, featuring a plurality of shelves 36, 38 on each half of the bayonet mount, is best shown in
The bow 12 comprises a mating attachment point 52, which is selected to correspond to the attachment point 16 of the handle 10. As discussed above, in a preferred embodiment, the attachment point 16 and the mating attachment point 52 are the two halves of a bayonet mount. In a preferred embodiment, the bow 12 further comprises a distal end segment 54, which is designed to attach to one end of the blade 40. The other end of the blade 40 attaches to the handle 10. The bow 12 may further comprise one or more intermediate segments 56, which serve to increase the distance between the distal end segment 54 and the handle 10, to allow for a longer blade 40. These intermediate segments 56 may be manufactured in different lengths for different blades 40, and more than one intermediate segment 56 may be used to minimize packing dimensions and allow for a longer blade 40.
In a most preferred embodiment, the distal end segment 54 has a half of a bayonet mount selected to mate with the half of a bayonet mount found on the handle 10. Each intermediate segment 56 has one female and one male half of a bayonet mount (20 and 18), on opposite ends. In this way, any intermediate segment 56, or a plurality of intermediate segments 56, may be interposed between the handle 10 and the distal end segment 54 without any need to search and find the “correct” combination. All combinations are functional. It does not matter, in this embodiment, whether the handle 10 or the distal end segment 54 has the male half 18, as long as the other one of the pair has the female half 20.
In another embodiment, best shown in
The bow 12 itself must be stiff for the saw to function. Traditional bow saws use steel bows for strength. However, steel is heavy. Titanium is quite desirable for its light weight, and is most preferred from a purely functional standpoint. However, aluminum is preferred when cost must be taken into account. In order to make an aluminum bow 12 stiff without unnecessary weight, a truss structure is helpful. Trusses are well known in the construction arts, and used for spanning large spaces in such diverse applications as warehouse roofs, radio towers, and automotive or railroad bridges. The truss structure comprises an outside stringer 58 and an inside stringer 60, the stringers running substantially parallel to one another and both lying substantially in the plane 11, with ribs 62 running between them. In a preferred embodiment the ribs 62 are not perpendicular to the rails, but rather form triangles. In this way the bow 12 is stiff but also lightweight. The bow 12 may be formed by any conventional means, such as welding, brazing, or riveting. In a preferred embodiment it is formed from a single piece of material. This may be accomplished by casting, machining, laser cutting, 3D printing, waterjet cutting, stamping, or any other means that gives sturdy results.
The foregoing description and drawings are presented only for the purpose of illustration. The invention is limited only by the claims, which follow.
