WO1997035689A1

WO1997035689A1 - An improved striking tool

Info

Publication number: WO1997035689A1
Application number: PCT/US1997/005158
Authority: WO
Inventors: Todd Douglas Coonrad
Original assignee: Todd Douglas Coonrad
Priority date: 1996-03-28
Filing date: 1997-03-28
Publication date: 1997-10-02
Also published as: US5988019A; DE69731214T2; US6250181B1; US20030037641A1; JP3404048B2; US6131488A; AU720459B2; EP0932478B1; US6460430B2; US6615691B2; AU2596497A; DE69731214D1; US5860334A; CA2272914A1; EP0932478A4; EP0932478A1; CA2272914C; US5768956A; JP2001526592A; US20010010182A1

Abstract

A head-to-handle interface (19) for a striking tool having a plane of symmetry has a web (23) in the plane of symmetry and sidewalls (21A, 21B) around the periphery of the web except for the direction of joining the handle to the head, the web and sidewalls forming socket areas (16) on both sides of the web, such that a handle (37) shaped to engage the sockets is joined to the head in a manner that bending stresses are greatly alleviated at and near the head-to-handle interface. In one embodiment a variable weight system (35) provides for a user varying the weight of the head of a striking tool. In another aspect, a nail-pulling slot (34) is provided with significantly tapered inner walls.

Description

An Improved Striking Tool

By Inventor Todd D. Coonrad

Field ofthe Invention

The present invention is in the area of hand-held striking tools, such as hammers and pickaxes, and pertains more specifically to joining handles and heads for such tools, accommodating a demand for a variety of weights for such tools, and improving claw hammer versatility.

Background ofthe Invention

Hand-held striking tools, such as claw hammers, mallets, sledge hammers, ball peen hammers, masonry hammers, pickaxes, and the like, have been used by people in a variety of disciplines for centuries as leveraged devices to provide a striking force to accomplish a seemingly endless variety of tasks. For example, a claw hammer, commonly weighing from 7 to 32 ounces is used by people doing carpentry work to deliver sufficient striking force to drive a nail into wood. A claw hammer is also used for removing a nail or ripping apart lumber using it's claw. A sledge hammer, commonly weighing from 2 to 20 pounds, is used to deliver sufficient striking force for heavy work such as driving a stake, rawl drill, chisel, or driving a wedge into masonry, stone, wood, or other hard materials.

Another common hand-held striking tool is a ball peen hammer, which has a substantially flat surface on one end and a rounded surface on the other end of its head, and is used to deliver sufficient striking force for shaping and fitting metal, and for driving machine chisels, rivet sets, machine wedges, and other similar tools. A pickaxe is another example of a hand-held striking tool which is commonly used for loosening hard dirt and stones, and also used as a lever for prying heavy objects from the ground. Another common hand-held striking tool is a mallet, which is usually made of wood, plastic, rubber, or soft iron. A mallet provides a striking force to drive chisels or shape metal and other materials without significantly marring the material it strikes.

Hand-held striking tools, such as those described above, are commonly used as third-class levers used to provide a striking force to accomplish tasks such as driving a nail into a piece of wood, bending or forming metal, breaking a rock, and other similar tasks. Third class levers are levers where a fulcrum, also referred to as a pivot point, is at one end of a bar or rod. A load to be overcome is an object creating resistance at the opposite end of a bar or rod. An effort, or force, to be applied to a third-class lever is somewhere in between a fulcrum and load. In the case of a hand-held striking tool such as a claw hammer, the fulcrum is a wrist, the force is provided by deceleration of the movement of a hammer handle (bar or rod) at the wrist, and the load is a resistance presented by a piece of wood into which the nail is being driven. In another example, a hand-held striking tool such as a pickaxe, the fulcrum is also a wrist, the force is provided deceleration of the movement of a pickaxe handle (rod) at the wrist, and the load is a resistance presented by dirt or stones into which the shaφ point ofthe pickaxe is driven. The head of a hand-held striking device is commonly a significant distance from the fulcrum and moves faster than the movement being applied at a user's hand, which is near the fulcrum. The increased speed of the head multiplies the applied force with which a striking device head strikes a nail or digs into the dirt. The longer a claw hammer's handle, for example, the faster the head and the greater the force that strikes a nail and overcomes the resistance ofthe wood. This principle applies to all other hand-held striking devices, and is intensified in long-handled striking devices such as a pickaxe or an axe. Hand-held striking tools are also commonly used as first-class levers to provide a lifting or prying force to accomplish a variety of tasks. For example, some hand-held striking devices are used to pull nails out of a pieces of wood, tear apart pieces of wood or other building material, pry loose a large rock, lift a log, and the like. First class levers are levers wherein he load to be overcome is at or near one end of a rod or bar, the effort, or force is applied at or near the other end ofthe same rod or bar, and the fulcrum, or pivot, is somewhere along the rod or bar in between the applied force and load.

An example of a hand-held striking tool being used as a first class lever is a claw hammer being used to pull out nails, wherein the load to be overcome is the wood causing friction against an embedded nail. Another example of a hand-held striking tool being used as a first class lever is a pickaxe being used to pry out a rock or tree root embedded in dirt or rock, where the load to be overcome is the dirt or rock causing friction against an embedded rock or tree root. Whenever a hand-held striking tool is used as a first class lever, the force is applied at one end of a long handle. The fulcrum is typically near the other end ofthe handle which holds the head.

The load for a hand-held striking tool being used as a first class lever, such as in a claw hammer or a pickaxe, is typically very close to the fulcrum. Whereas the force for a hand-held striking tool being used as a third class lever is typically relatively far away from the fulcrum. During prying or pulling tasks, the load applied is therefore moved less distance than the hand, which is at the opposite end ofthe lever, and applying the force. This multiplies the force in which the claw hammer head pulls against a nail, or a pickaxe pulls against a rock.

The weakest part of a hand-held striking device is the interface between the handle and the head. The conventional method of interfacing a striking device head and handle, which are typically made of distinct materials, such as metal and wood, allows striking and pulling stresses to promote head-to-handle loosening, damage, and separation. For example, the impact force at the head of a claw hammer, being used as a third class lever against a nail, is often as high as 300 pounds.

Because ofthe greater length of its handle and greater weight of its head, the striking force ofthe head of a pickaxe against the earth is many times greater.

The bending moment applied at the head-to-handle interface of a claw hammer being used as a first class lever to pull out a nail is often as high as 1,000 foot-pounds. The bending moment levied against the head-to-handle interface of a pickaxe pulling heavy rocks away from the earth is typically many times more.

The effect of these forces is exacerbated when a user occasionally misses his target and strikes the handle of such a tool against a hard object, such as the edge of a piece of wood, or a rock, at the head-to-handle interface just below the head. This causes further damage and weakens a head-to-handle interface.

Because ofthe inherent weakness in conventional head-to-handle interfaces, it is at this point that most failures in hand-held striking devices occur. Methods have been devised to make head-to-handle interface configurations capable of withstanding impacts and pulling stresses described above without damage. These methods include using a handle made with a material, such as high-impact plastic or heavy- gage rolled steel, that has particularly high strength and resiliency to withstand extremely high impacts and pulling stress. These types of handles are typically encapsulated in a resilient material, such as natural or synthetic rubber, leather, or plastic, to provide some protection from the shock from impact and to give a user a good grip on the handle. Many users of hand-held striking devices, however, still prefer the look and feel of wooden handles. As stated above, a problem with many conventional methods for increasing handle strength on hand-held striking devices is the inherent weakness in the design of interfaces. Current interfaces for hand-held striking tools typically comprise a handle whose end is shaped to make a tight fit through a shaped opening in the head. Such a shaped opening is often tapered so the fit can be tightened by driving the head in the direction against the taper. This interface is typically made secure by a variety of methods. In one conventional method, for example, wooden handles are often secured by metal or wooden wedges or cylinders forced into the top ofthe handle after the handle is inserted into the head. This expands the wood so it makes a tight fit against the inner surfaces ofthe opening. A tight fit, however, does little to increase the strength ofthe conventional head-handle interface.

In another method, metal handles may be made tight to a head with an opening by heating the head and/or cooling the handle significantly to create a relatively loose fit. This allows easy insertion of the handle into the hole in the head. After insertion of a handle into the hold in a head, the metal head and handle return to ambient temperature, and the opening in the head contracts and/or the metal handle expands to produce a tight fit. Another common method for securing conventional head-to- handle interfaces is by placing a bonding material, such as an epoxy adhesive, between the inner surface ofthe opening in the head and outer surface ofthe interface end ofthe handle.

The types of head-to-handle interfaces and methods of securing described above are commonly used on all types of hand-held striking tools, such as axes, sledge hammers, pickaxes, and the like. A problem with these conventional solutions is that the striking and pulling forces are concentrated over a short distance at the interface. The intensified stress at this small area is the cause of most hand-held striking tool failure. Head-to-handle interfaces made according to conventional art, regardless ofthe material ofthe handle or method of securing it to the head opening, often fail because of this concentrated stress.

As describe earlier, hand-held striking devices typically come in a variety of weights, depending upon the task at hand or the physical condition ofthe user. For example, claw-hammers used for general caφenter work, commonly referred to as a curved-claw nail hammer, are typically manufactured and sold in weights from 7 to 20 ounces. Claw hammers designed and used for rough work such as framing, opening crates and prying apart boards, commonly referred to as ripping hammers, are typically manufactured and sold in weights from 20 to 32 ounces. The primary difference between a curved nail hammer and a ripping hammers is that the ripping hammer has a substantially straighter and longer claw than a curved nail claw.

Another example of weight variations in hand-held striking tools are sledge hammers. These hand-held striking devices are used to apply heavy duty striking forces against objects. They are manufactured and sold in weights from 2 to 20 pounds. Many other striking tools, such as pickaxes, axes, mallets, and the like also are typically manufactured and sold in a range of weights to suit the needs of a user.

A user, particularly a professional, commonly may need a hand¬ held striking tool in two or more weights to accommodate a particular task at hand or his current physical condition. Assume, for example, a caφenter lying on his back inside an attic of a small alcove at a home construction site installing braces above him. He or she might prefer a light nail-pulling hammer, such as 16 ounces, to accommodate the fact that he or she must swing the hammer up against gravity with a small space for arm movement. The same caφenter, who later moves to a different home construction site to remove foundation forms and install floor joists may choose a heavier ripping hammer, such as 30 ounces. This will enable him or her to take advantage ofthe downward force of gravity and greater area to swing the hammer. A disadvantage in current art is, in situations like these, the caφenter must purchase and care for two or more separate hammers, which adds to his cost and maintenance. As described above, the common two types of claw hammers are the curved-claw nail hammer, used for light caφentry work, and the ripping hammer, which is typically used for heavy rough work with wood. A curved-claw nail hammer is well suited for pulling nails because the curve of its claw provides increased leverage because the nail (load) is placed close to the end ofthe handle near the lever's fulcrum. A curved-claw nail hammer is not well suited for ripping tasks because the curve of its claw makes it difficult to fit between planks and make a direct cutting blow to tear into materials, such as plaster wall. A ripping hammer, on the other hand, is well-suited for tearing apart planks and breaking into materials, such as a plaster wall, because its relatively straight claw fits more readily between planks and angles, and its cutting edge (wedge) points directly away from the hammer's head. A ripping hammer is typically not well-suited for pulling nails because the width of its claw to ensure adequate ripping strength preclude placing a nail pulling slot close to the fulcrum for increased leverage. A user, particularly a professional, often purchases one or more curved-claw nail hammer and one or more ripping hammer to accommodate his or her need to perform specialized nailing or ripping tasks. This adds to a user's costs and maintenance for their care.

What is clearly needed is a head-to-handle interface for hand¬ held striking devices that can minimize bending stresses at head-to- handle interface when using a wooden handle, or a handle made from any suitable material. What is also clearly needed is a method to change the weight of a hand-held striking device to accommodate a user's changing weight needs without purchasing two or more ofthe same type of striking device.

What is also clearly needed is a claw hammer that is equally suitable for pulling nails as it is for ripping boards and other materials to accommodate a user's changing needs without requiring the user to purchase two or more different claw hammers.

Summary ofthe Invention

In a preferred embodiment a head-to-handle interface is provided for attaching a handle to a head of a striking tool having a plane of substantial symmetry. The interface extends in the direction ofthe long axis of a handle to be attached, and comprises a central plate elongated in the handle direction. Sidewalls substantially orthogonal to the central plate extend on each side ofthe central plate around the periphery ofthe central plate except in the handle direction. The central plate and the sidewalls form socket areas on both sides ofthe central plate for accepting a shaped handle in a manner that stresses on the handle in operation will be spread over a considerably larger portion ofthe handle than in the prior art. The interface to a handle provided disperses stresses into a larger volume of handle material than in known prior art systems, providing extended life and physical integrity.

In one embodiment the head-to-handle interface further comprises a reinforcing rail joined to the central plate and extending in the handle direction, forming a reinforcement for a handle to be added. In another embodiment a striking tool is provided comprising a head portion having at least one impact end; a head-to-handle interface having a central plate elongated in one direction and sidewalls extending on each side ofthe central plate around the periphery ofthe central plate except in the first direction, forming sockets on each side ofthe central plate; and a handle engaged in the head-to-handle interface. The handle is adapted to fit into the sockets formed by the central plate and the sidewalls.

The striking tool can be a claw hammer having an impact head and a claw, or one of a pickaxe, a sledgehammer, a maul, or an axe. The handle may be a two-piece handle, the two pieces joined to one another enclosing and joining to the central plate, or a one-piece handle having a slot at one end adapted to enclose the central plate. In some embodiments there is a reinforcing rail joined to the central plate and extending in the handle direction, forming a reinforcement for a handle to be added. A handle can be molded around the reinforcing rail and the central plate, filling the sockets formed by the sidewalls extending from the central plate.

In another embodiment a striking tool is provided comprising a head portion having at least one impact head; and a variable weight apparatus positioned adjacent the at least one impact head, the variable weight apparatus comprising removable weights and an attachment apparatus for holding the weights securely to the striking tool. The striking tool can be a claw hammer having an impact head and a claw, any of a pickaxe, a sledgehammer, a maul, or an axe, or any other sort of striking tool. In yet another embodiment a claw hammer head is provided comprising an impact head; a claw extending from the impact head; and a head-to-handle interface having a central plate elongated in a direction away from the impact head and the claw, the interface having sidewalls extending from each side ofthe central plate around the periphery ofthe central plate except in the direction of extension ofthe central plate, the central plate and sidewalls forming sockets on each side ofthe central plate for accepting a hammer handle.

The claw hammer head may have a variable weight apparatus positioned adjacent the impact head, the variable weight apparatus comprising removable weights and an attachment apparatus for holding the weights securely to the claw hammer head. In various embodiments the claw hammer head has a central plane of symmetry, and the impact head and the claw are joined by webbing elements lying in the central plane of symmetry, and the central plate is coplanar with the webbing elements.

In yet another aspect a claw hammer has a central plane of symmetry and comprises an impact head centered on the plane of symmetry, the impact head having a length Ll in the plane of symmetry and a width Wl at right angles to the plane of symmetry. A curved claw extends a length L2 from the impact head, has width W2 substantially equal to Wl, a substantially constant thickness Tl along the curved length, and an outer surface to the outside ofthe curve ofthe claw. A nail-pulling slot at the end ofthe claw opposite the impact head has internal walls tapered away from the outer surface ofthe claw, the included angle made by the tapered walls equal to or greater than 40 degrees.

The tapered nail-pulling slot allows a user to fully engage a nail with the nail head close to the surface wherein the nail is embedded, and to pull the nail with a single stroke. The general assembly of the claw hammer according to many embodiments ofthe present invention is unique, in that the impact head and the claw are connected by webs in the plane of symmetry, and reinforcement is added by bracing wall elements of substantially the thickness ofthe webs extending substantially at right angles to the webs on both sides of the centrally located webs, not exceeding in overall height width Wl. The unique head-to-handle interface is formed by an extension ofthe webs and brace elements providing a pleasing and functional appearance.

Brief Description ofthe Drawings

Fig. 1 A is a top view of the head of a conventional claw hammer.

Fig. IB is a left side view ofthe conventional claw hammer of Fig. 1 A, showing the head-to-handle interface.

Fig. 2 is a left side overview of a claw hammer according to an embodiment ofthe present invention. Fig. 3 A is a left side view ofthe head and head-to-handle interface of the claw hammer of Fig. 2.

Fig. 3B is a left side view ofthe head and head-to-handle interface ofthe claw hammer of Fig. 2 according to another embodiment ofthe present invention. Fig. 3C is a side elevation view ofthe head and head-to-handle interface of a claw hammer according to an alternative embodiment of the present invention.

Fig. 4 is a right side view ofthe head and head-to-handle interface ofthe claw hammer of Fig. 2. Fig. 5 A is a front view ofthe head and head-to-handle interface of the claw hammer in Fig. 2.

Fig. 5B is a isometric view of a weight according to an embodiment of the present invention.

Fig. 5C is a face-on view ofthe striking surface ofthe hammer of Fig. 2.

Fig. 6 is a rear view ofthe head and head-to-handle interface of the claw hammer in Fig. 2

Fig. 7 is a top view ofthe head and head-to-handle interface of the claw hammer in Fig. 2. Fig. 8 A is an exploded isometric view of a claw hammer head, handle, and head-to-handle Interface according to a preferred embodiment ofthe present invention. Fig. 8B is an exploded view of a claw hammer head, handle, and head-to-handle Interface according to another embodiment ofthe present invention.

Fig. 9 A is a left side view of a sledge hammer head and head-to- handle interface according to an embodiment ofthe present invention.

Fig. 9B is a left side view of a pickaxe head and head-to-handle interface according to an embodiment ofthe present invention.

Fig. 9C is a left side view of an axe head and head-to-handle interface according to an embodiment ofthe present invention. Fig. 10A is a top view of a claw hammer according to conventional art.

Fig. 10B is a left side view ofthe claw hammer of Fig. 10A.

Fig. IOC is an enlarged rear view ofthe claw hammer claw of Fig. lOA and 10B. Fig. l lA is a top view of a claw hammer according to a preferred embodiment ofthe present invention.

Fig. 1 IB is a left side view ofthe claw hammer of Fig. 1 IA.

Fig. 1 1 C is an enlarged rear view of a claw hammer claw ofthe claw hammer of Figs. 11 A and 1 IB.

Description ofthe Preferred Embodiments

The present invention in various embodiments overcomes an inherent weakness in conventional head-to-handle interface methods to provide a durable, long-lived head-to-handle interface for hand-held striking devices. It also provides a method and apparatus to facilitate changing the weight of a hand-held striking device. This feature accommodates a user's varying weight needs without requiring purchase of two or more ofthe same type of striking device. The present invention in various e- diments also provides a type of claw hammer that is well-suited f< th pulling nails and ripping boards and other materials. This o _*ates the need for a user to purchase and care two or more types of claw hammers.

Fig. IA and IB are top and side views of a conventional claw hammer, showing parts that are typical to hand-held striking devices, and parts peculiar to a conventional claw hammer. Parts common to many hand-held striking devices are an impact head 39 and a head-to- handle interface 41. Impact head 39 for a claw hammer typically has a substantially flat surface of sufficient size at its end for easily striking a head of a nail.

Impact heads of many sizes and shapes are manufactured and sold to suit the peculiar use of a hand-held striking device. For example, a ball-peen hammer impact head typically has one substantially flat head at one end, and a substantially rounded impact head on the other end. This combination provides a user with flexibility to strike a material, such as metal, a variety of ways at angles to conform the material to a desired shape. A pickaxe typically has two elongated impact heads that are pointed at their ends so they will penetrate dirt, rocks, or any desired surface. An axe commonly has one or two impact heads that have shaφ wedges to allow a user to cut into wood or other materials.

Head-to-handle interface 41, shown in Fig. 1 A and IB, is a common configuration for many types of hand-held striking devices. It comprises interface opening 46 in hammer head 36, and retaining wedges 42. Interface opening 46 is a substantially rectangular opening of suitable size and shape to insert, and make a tight fit for, a similarly shaped hammer handle interface end 44. Retaining wedges 42 are driven into the handle interface end 44 after assembly ofthe head to the handle to expand handle interface end 44 so its outer surface fits tightly against the inner surface of interface opening 46. This is a conventional method for holding a hammer head to a handle.

In the conventional arrangement of Fig. IA and Fig. IB, use of the hammer for either striking or pulling concentrates stress in a relatively small region, which is region 48 shown in Fig. IB. A concentration of high bending moments is generated as head 36 strikes a nail or other surface, which causes a force reaction in the direction opposite to the head movement. There are also instances wherein a hammer head misses the intended target, and the target is struck at or near the interface area. This happenstance creates an even greater bending moment at the interface than the usual striking action. Also, in pulling nails and the like, bending moments are concentrated at the head-to-handle interface. The combination of these stresses degrades the integrity of a head-to-handle interface over time. Looseness and eventual separation result, and in some instances the handle fails at the interface. Most people have - 12 - experienced such a broken handle in one or another ofthe various types of striking and pulling tools.

Parts in Fig. 1 A and IB that are peculiar to claw hammers are a conventional claw 40 having a wedge shape 62, and conventional nail- pulling slot 43. Conventional claw 40 is either substantially curved or only slightly curved, depending on its primary use as a nail-pulling claw or a ripping claw. In both cases, the working end of claw 40 is wedge- shaped and usually has a nail-pulling slot 43. The height of nail-pulling slot 43 substantially conforms to wedge thickness along its length, such as at heights Dl 2 and D 13. As will be discussed later, this characteristic limits the ability of a user to grip and pull nails when the nail heads are close to the surface of a material into which the nails are embedded.

Fig. 2 is a left side view of a claw hammer 12 according to an embodiment ofthe present invention. Claw hammer 12 comprises a claw hammer head 11 and handle 37. Hammer head 11 comprises an impact head 13, an optional adjustable weight assembly 35, structural webbing areas 25, 27, and 31 , cross braces 29, a head-to-handle interface region 19, an optional side nail-pulling slot 17, a claw 20 having a chamfered claw end 33, and a tapered nail-pulling slot 34 (not shown, but described elsewhere). Claw hammer 12 has significantly greater head-to-handle interface integrity, plus versatility in weight and claw use than does the conventional claw hammer configuration already described.

Most hammer heads in the prior have a nearly constant width such as width Dl in Fig. 1 A. Hammer head 11 differs in that the several parts are distinct and connected by reinforcing webbing. This structure is shown in Fig. 3 A, but will be better understood by referring to Fig. 8A, to be fully described later, then returning to Fig. 3 A.

Impact head 13 of hammer head 11 is similar to the impact head of a conventional hammer, except in hammer head 1 1 , impact surface 15 is inclined at an angle of from 2 to 5 degrees with vertical when the long axis ofthe hammer handle is vertical. The inventor has found that this inclination provides for driving nails straighter than with hammers lacking such inclination. Another difference with conventional hammers is that the impact head extends from impact surface only a relatively short distance, usually about one inch or less, shown as dimension D2 in Fig. 3A. Yet another significant departure from conventional hammer design is in the claw. Whereas conventional claws are formed by tapering the width of the hammer head in gentle curvature, providing a claw with diminishing thickness toward the claw end, as shown in Fig. 1 B, claw 20 in the present embodiment is a curved section with substantially constant width D3. An edge for ripping and tearing is formed by a chamfered end 33.

Claw 20 in this embodiment has an optional side nail-pulling slot 17, and a tapered nail-pulling slot 34 (not shown here, but described later). Claw 20 in the present embodiment has greater strength and functionality for ripping and nail pulling tasks than does a conventional claw.

In hammer head 1 1 impact head 13 and claw 20 are joined to a head-to-handle interface region 19 by structural reinforcing webbing regions 25 and 27 and by brace elements 21 A and 21 B at right angles to webbing regions 25 and 27. Brace elements 21 A and 21 B are crossed in an integral arrangement to provide maximum strength while presenting also a pleasing and distinct visual effect.

Fig. 4 is a right side view of hammer head 11, and shows a structure similar to that ofthe left side view. Reinforcing web regions 25 and 27 are in the vertical plane of symmetry ofthe hammer head, which again may be better seen by referring to isometric view Fig. 8A. Portion 31 ofthe hammer head, substantially triangular in shape and enclosed on three sides ofthe triangle by claw section 20 and reinforcing braces 21 A and 21 B is open through the hammer head in some embodiments. In other embodiments a web 31 similar to webs 25 and 27 is provided coplanar in the plane of symmetry with webs 25 and 27. In the embodiment shown in Figs. 3 A and 4 web 31 is at one edge ofthe hammer head, opposite nail slot 17. In this manner web 31 forms an auxiliary striking surface on the side ofthe hammer head.

Braces 21 A and 21B cross (and are joined) at region 29 and extend in a gentle curvature in the direction handle 37 assumes in the long axis (see Fig. 2) forming and enclosed region 16 having also a central web 23. This region, designated by a bracket and element number 19 in Fig. 3 A, considering the two sides ofthe hammer head, forms a hammer-to-handle interface region having central web 23 and sidewalls on each side provided by braces 21 A and 2 IB. As with other features of hammer head 11 , the geometry of interface region 19 may be best understood by reference to Fig. 8 A as well as Fig. 3A and Fig. 4.

Claw hammer head 1 1 as described above with reference to the Figs, is, in a preferred embodiment, forged from high carbon steel, although some other materials are also suitable. In alternative embodiments casting processes are used, and materials such as stainless steel are utilized.

Hammer head 11 with head-to-handle interface region 19 described above is shown as a single casting or forging, can also be assembled from separate components and connected by welding, brazing, riveting, riveted, epoxy bonding, or any suitable manner without departing from the spirit and scope ofthe invention.

Most hammer heads in the prior art are, as described above, monolithic, and if a head of a different weight is needed or wanted, the user must purchase a second hammer. In embodiments ofthe present invention variable head weight is provided by an adjustable weight assembly 35, which a user may change to accommodate current need.

Fig. 5 A is a front view of a claw hammer head of Fig. 4, with a portion ofthe impact head cut away to show adjustable weight assembly

35, which is behind impact head 13 in this view. Fig. 5B is a isometric view of a weight, 18 according to an embodiment ofthe invention. Given this unique feature, a user may adjust the weight, and therefore the inertia in operation, of the hammer head by removing and adding weights 18. Weights of different sizes are provided in some embodiments.

In Fig. 5 A it is seen that braces 21 A and 21 B taper away in the direction of the handle interface, starting with a combined height D4 of substantially the width ofthe hammer head and tapering to a width D5 of about one-fourth the width of the hammer head. This taper may be different in other embodiments.

Adjustable weight assembly 35 comprises a conventional bolt 14, a locking nut 16, and weights 18. Weights 18 in are one pair of a variety weights in different sizes that may be easily removed and added. Weights 18 in the embodiment of Fig. 5 A are cylindrical, but may be of any convenient shape without departing from the intent of the present invention. Although the weights are held in place by a bolt and locking nut in the embodiment shown, in other embodiments the weights may be fastened to the hammer head in a variety of ways. It is deemed important by the inventor that the weights be held securely, to avoid being jarred loose by virtue ofthe rather severe impacts experienced in use.

Fig. 5C is a view of just the face of impact head 39 in the same direction as Fig. 5A. This shape may vary in other embodiments, but has a semicircular lower aspect and an upper aspect with rounded corners. This shape allows a user to use the hammer in corners better than if the face were entirely circular.

Fig. 6 is a rear view of hammer head 1 1 of Figs. 3 A, 4, and 5 A, showing claw 20, nail slot 34, and chamfered end 33 from this vantage. Chamfered claw end 33, to be described in more detail below, provides a shaφ edge required for ripping tasks. Providing the ripping edge as a chamfer also allows claw 20 to be fashioned in substantially uniform thickness as described with reference to Fig. 3 A. This provides improved strength over conventional claw hammers, which is an advantage for nail pulling and ripping tasks.

Fig. 7 is a top view of hammer head 11 , showing connectivity of web 25, web 27, braces 21 A and 2 IB, and center web 31. As described above, the structure may be of a single piece, as with a forging or a casting, or may be fabricated by welding from separate parts.

Center web 31 is aligned in the embodiment shown flush with one side ofthe hammer head. In other embodiments this wall structure may be centrally located, as with webs 25 and 27. The location of this web, if used, should not block side nail-pulling slot 17. In some embodiments the head may be open through this area with no web 31. The placement of web 31 to the far side ofthe head from side nail- pulling slot provides a side striking surface for the hammer, which is convenient in many situations.

Fig. 8A is an exploded isometric view of hammer head 1 1 and a two-piece handle 37 comprising parts 49 A and 49B in an embodiment of the present invention. Handle 49A has a recessed area 28 with a height D6 and length D7. Height D6 and length D7 substantially correspond to thickness D5 and length D7 of interface web 23. The puφose of this recessed area is to accommodate web 23 in assembly while allowing the two portions ofthe handle to come together. The recess can be in either handle portion, and in some embodiments the recess may be in both handle portions, each with a depth of one-half the thickness of web 23.

Each of handle parts 49A and 49B has a nose region 48 shaped to fit a matching socket provided on each side of head-to-handle interface region 19 of hammer head 1 1. This shape includes, on each part, surfaces 50 to match the inside surfaces 50a formed by brace elements 21 A and 21 B on each side ofthe head-to-handle interface.

Handle parts 49A and 49B come together in the sockets on each side ofthe head-to-handle interface and are joined by fasteners 30 (see Fig. 2). In embodiments utilizing such fasteners, opening through web 23 are provided, even though these openings are not shown in Fig. 8A. The fasteners can be any of a number of conventional types, such as rivets or screw thread fasteners with large decorative heads. In some embodiments an adhesive filler may be used to assure a secure bond in joining the two handle parts to the hammer head.

As has been described above, and as may be better understood with reference to Fig. 2, bending moments are produced in planes parallel to the major axis of symmetry ofthe hammer as the hammer is used, either in impacting a nail or a surface with impact head 13 or in nail pulling or ripping operations with claw 20. In a conventional hammer (Fig. IB) these moments are concentrated in a small area 48. In the hammer of Fig. 2 these effects are spread over a the entire handle area in interface region 19, and absorbed by the inner surfaces of brace elements 21 A and 21 B along the length of region 19. Stress and strain are therefore very much less, and the hammer assembly may be expected to be much more reliable and durable than has been available in the prior art.

In those embodiments having a side nail-pulling slot 17 (see Fig. 7), the force applied to the hammer handle in pulling nails and in use of striking surface 31 is at right angles to the force applied in striking with impact head 13 and in nail pulling and ripping with claw 20 and nail- pulling slot 34. Bending moments produced in these operations are then at right angles to those produced in impacting with head 13 and in nail pulling and ripping with claw 20 (slot 34). The forces in this case are spread over the surface areas of web 23, and the stresses and strains produced are much lower than in the conventional case. Fig. 8B is another exploded view of claw hammer head 11 and a handle according to another embodiment ofthe present invention. In this embodiment the handle is a single piece having a slot 38 of height D9 and length D10, which corresponds dimensionally to height D5 and length D7 of interface region 19. Handle 37a in assembly simply slides into place, filling the sockets created by web 23 and sidewalls of brace elements 21 A and 2 IB, and is fastened by the expedients described above for the two-piece handle with reference to Fig. 8A.

In alternative embodiments ofthe present invention a center spine 22 is provided, welded or otherwise fastened to web 23 to provide a high-strength inner axis for a handle. In these embodiments, appropriate grooves may be provided in wooden handle parts to accommodate the inner spine, or a handle may be molded-in-place, still filling the interface region 19, which, even in this case, provides additional strength and durability.

As also mentioned above, the unique head-to-handle interface has been described by the example of a claw hammer. A claw hammer, however, is not the only tool which might well benefit from such an interface. The interface is applicable to nearly all sorts of striking and pulling tools.

Figs. 9A, 9B, and 9C show different types of striking devices illustrating the versatility of applications for the present invention. Fig. 9A is an elevation view of a sledge hammer head 60 with a head-to- handle interface 55 according to an embodiment ofthe present invention. There are two opposite impact heads 51 A and 51 B, and weight assemblies 53A and 53B. In addition there are a center web 54, front web 59, rear web 61, interface web 56, brace elements 58 A and 58B.

The general construction of sledge hammer head 60 corresponds to the construction of hammer head 11 described in detail above, including head-to-handle interface 55 corresponding to head-to-handle interface 19 described above. There are also variable weight assemblies 53A and 53B corresponding to variable weight assembly 35 in the hammer embodiment. This feature is optional. Fig. 9B shows a pickaxe head 70 with head-to-handle interface

73 according to an embodiment the present invention. Pickaxe head 70 has impact heads 63A and 63B, variable weight assemblies 65A and 65B, a center web 64 (optional), a front web 67, a rear web 69, interface web 66, and brace elements 68A and 68B. Impact heads 63A and 63B have a substantially pointed or bladed surface to suit traditional uses of a pickaxe. Fig. 9C shows an axe head 80 with a head-to-handle interface 89.

Axe head 80 has impact heads 75A and 75B, variable weight assemblies 77A and 77B, a center web 76 (optional), front web 81 , rear web 85, interface web 83, and brace elements 91 A and 91B. Impact heads 75A and 75B have a wedges cutting edges to suit traditional uses of an axe. Figs. 10A, 10B, and IOC are top, left elevation, and enlarged rear views of a conventional claw hammer, showing a claw and nail pulling slot according to conventional art. Fig. 1 IA, 1 IB, and 1 IC are top, left elevation, and enlarged rear views of a claw hammer in an embodiment ofthe present invention, showing a claw and nail pulling slot according to the present invention.

Conventional claw 40 (Fig. 10A, 10B, and IOC) is either substantially curved or only slightly curved, depending on intention as a nail-pulling claw or a ripping claw. In both cases, the working end of claw 40 is wedge-shaped and has a nail slot 43 (Fig. 10C) whose height conforms to the thickness of wedge region 43 in Fig. IB, which may vary from a height of D12 to D13 along the wedge length D14 (Fig. 10A). In a conventional claw the sidewalls of the nail-pulling slot are vertical, so, when pulling nails, the underside ofthe nail head is held against opposite surface 52. Because of this, a nail with its head very close to a surface wherein the nail is embedded cannot be fully engaged and pulled with a single stroke. One must first engage the nail head with just the tip ofthe slot, then work the nail further into the slot as it is withdrawn incrementally from the wood or other material within which it is embedded. Figs. 11 A, 1 IB and 1 IC show a top view, a side elevation view, and a rear elevation view of hammer head 11 having claw 20 and nail- pulling slot 34. In contrast to a conventional nail-pulling slot, slot 34 has angled sidewalls such that the width ofthe slot at the undersurface of the claw is substantially greater than at the top surface, as seen in Fig. UC. That is, dimension Dl 5 is substantially greater than dimension D16. This taper is such that most conventional nail heads are held within slot 34 rather than against a surface ofthe claw. In a preferred - 19 - embodiment the included angle is equal to or greater than forty degrees. An advantage is that the claw can be of a grater thickness near the end having the nail-pulling slot than is possible with a conventional claw, providing increased strength and durability. Claw 20 is substantially straighter than the curved claw of a conventional nail-pulling claw hammer and more closely resembles the curvature of a conventional ripping claw. Claw 20 also has a substantially constant thickness D3 (Fig. 1 IB, 1 IC, and Fig. 3A)). A shaφ edge for ripping tasks is provided by chamfered claw end 33. In some embodiments ofthe present invention the brace elements shown as 21 A and 21B in Fig. 3 A do not provide sidewalls all around the periphery of web 23, but only on one edge of web 23. Fig. 3C is a side elevation view of a hammer head and a head-to-handle interface according to this embodiment. In this embodiment brace element 21 A extends the full length of web 23, and forms side walls orthogonal to web 23 on opposite sides of web 23, but web 21B extends only to web 21 A, and does not form a sidewall to web 23. In this instance web 23 and web 27 are contiguous.

The inventors have found that in some embodiments sidewalls are not really necessary on both edges of web 23 in the head-to-handle interface, and as long as a handle is securely joined to the web and abutts the one sidewall, sufficient strength is imparted for striking and other tasks to be performed by a tool having the interface.

It will be apparent to those with skill in the art that there are many alterations that may be made in the embodiments described above without departing from the spirit and scope ofthe invention. For example, the specific shape ofthe elongated, edge-walled head-to- handle interface described may vary considerably from the embodiment shown in the drawings of this disclosure without departing from the scope ofthe invention. Some ofthe curvature and shaping is for aesthetic effect. The novelty in the interface is the presence ofthe center web (element 23 in Fig. 8A) and the sidewalls on three sides provided by the brace elements (elements 21 A and 2 IB).

There are many other variations that may be made. There are, for example, many ways handles may be fastened to heads of striking tools in embodiments ofthe invention. Several fasteners and adhesive fastening are described above. Handles may be of wood in a preferred embodiment, and many professionals still prefer wooden handles. Other materials may be used, however, such as molded polymer materials. There are similarly many ways variable weights may be provided and held in place other than the specific embodiments described. The invention is limited only by the language ofthe claims which follow.

Claims

I claim:

1. A head-to-handle interface for attaching a handle to a head of a striking tool having a plane of substantial symmetry, with the long axis ofthe handle extending in a first direction, the interface comprising: a central plate elongated in the first direction; and sidewalls substantially orthogonal to the central plate extending on each side ofthe central plate around the periphery ofthe central plate except in the first direction.

2. A head-to-handle interface as in claim 1 further comprising a reinforcing rail joined to the central plate and extending in the first direction, forming a reinforcement for a handle to be added.

3. A striking tool comprising: a head portion having at least one impact end; a head-to-handle interface having a central plate elongated in one direction and sidewalls extending on each side ofthe central plate around the periphery ofthe central plate except in the first direction, forming sockets on each side ofthe central plate; and a handle engaged in the head-to-handle interface; wherein the handle is adapted to fit into the sockets formed by the central plate and the sidewalls.

4. A striking tool as in claim 3 wherein the striking tool is a claw hammer having an impact head and a claw.

5. A striking tool as in claim 3 wherein the striking tool is one of a pickaxe, a sledgehammer, a maul, or an axe.

6. A striking tool as in claim 3 wherein the handle is a two-piece handle, the two pieces joined to one another enclosing and joining to the central plate.

7. A striking tool as in claim 3 wherein the handle is a one-piece handle having a slot at one end adapted to enclose the central plate.

8. A striking tool as in claim 3 further comprising a reinforcing rail joined to the central plate and extending in the one direction, forming a reinforcement for a handle to be added, and wherein the handle is molded around the reinforcing rail and the central plate, filling the sockets formed by the sidewalls extending from the central plate.

9. A striking tool comprising: a head portion having at least one impact head; and a variable weight apparatus positioned adjacent the at least one impact head, the variable weight apparatus comprising removable weights and an attachment apparatus for holding the weights securely to the striking tool.

10. A striking tool as in claim 9 wherein the striking tool is a claw hammer having an impact head and a claw.

1 1. A striking tool as in claim 9 wherein the striking tool is one of a pickaxe, a sledgehammer, a maul, or an axe.

12. A claw hammer head comprising: an impact head; a claw extending from the impact head; and a head-to-handle interface having a central plate elongated in a direction away from the impact head and the claw, the interface having sidewalls extending from each side ofthe central plate around the periphery ofthe central plate except in the direction of extension ofthe central plate, the central plate and sidewalls forming sockets on each side ofthe central plate for accepting a hammer handle.

13. A claw hammer head as in claim 12 further comprising a variable weight apparatus positioned adjacent the impact head, the variable weight apparatus comprising removable weights and an attachment apparatus for holding the weights securely to the claw hammer head.

14. A claw hammer head as in claim 12 having a central plane of symmetry, wherein the impact head and the claw are joined by webbing elements lying in the central plane of symmetry, and wherein the central plate is coplanar with the webbing elements.

15. A claw hammer having a central plane of symmetry and comprising: an impact head centered on the plane of symmetry and having a length Ll in the plane of symmetry and a width Wl at right angles to the plane of symmetry; a curved claw extending a length L2 from the impact head, having width W2 substantially equal to Wl, a substantially constant thickness Tl along the curved length, and an outer surface to the outside ofthe curve ofthe claw; and a nail-pulling slot at the end ofthe claw opposite the impact head; wherein the nail-pulling slot has internal walls tapered away from the outer surface ofthe claw, the included angle made by the tapered walls equal to or greater than 40 degrees.

16. A claw hammer as in claim 15 wherein the impact head and the claw are connected by webs in the plane of symmetry, and reinforcement is added by bracing wall elements of substantially the thickness ofthe webs extending substantially at right angles to the webs on both sides of the centrally located webs, not exceeding in overall height width Wl .

17. A claw hammer as in claim 16 wherein an interface web in the plane of symmetry extends away from the impact head and claw in the direction of a handle of the claw hammer, and wherein the brace elements extend away from the impact head and the claw forming walls around the interface web on both sides ofthe interface web, except in the direction ofthe handle, the interface web and the brace elements forming thereby sockets on each side ofthe interface web adapted for receiving the handle.

18. A method for joining a handle to a head of an impact tool, comprising steps of: (a) forming a head-to-handle interface in the handle direction, the interface having a central web and sidewalls extending at right angles to the plane ofthe central web around the periphery ofthe central web except in the handle direction, the central web and the sidewalls forming socket areas on both sides ofthe central web;

(b) shaping the handle in two pieces divided along a plane along a long axis ofthe handle, with one end of each handle piece shaped to engage the sockets formed by the central web and the sidewalls, and one or both pieces shaped to accommodate the central web; and

(c) joining the two handle pieces enclosing the central web with the shaped ends ofthe handle pieces engaged in the sockets formed by the central web and the sidewalls.

19. The method of claim 18 wherein the joining is accomplished by fasteners through the two handle pieces and the central web.

20. The method of claim 18 where the joining is accomplished in part with an adhesive material applied between the two handle pieces and the central web.