US 3115912 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Dec. 31, 1963 T. HARRls 3,115,912
l TOOL HANDLE Filed Oct. 28, 1960 f5 l 75 lg mms/Ton T/-loMn HARP/.9
3,115,912 TOOL HANDLE Thomas Harris, Gates Mills, Ohio, asslgnoil to Structural Fibers, Inc., Chardon, Ohio, a corporation of Ohio Filed Oct. 28, 1960,Ser. No. 65,822 3 Claims. (Cl. 145-61) This invention relates generally to tool handles, and, more specifically, to a reinforced wooden handle construction for hand tools.
The invention is particularly concerned with an improved wooden handle construction for hand tools of the type which, in normal use, are frequently subjected to` severe stresses, and are exposed to inclement conditions of humidity and dampness. Typical of such tools are percussive hand tools, such as hammers, axes, picks, Sledge-hammers and the like, having a construction including a metal impact head and an attached handle through which impact force is applied to the head. While the handle comprising the present inventionlis particularly well adapted for'use in conjunctionV with percussive tools, and is thus hereinafter specifically related to their manufacture, it is to be understood that the invention has application in the manufacture of handles for a wide variety of other tools which incur occasional breaking stresses, such as hoes, rakes, post hole diggers and the like.
The established and most commonly known and used handles for tools of the type described, and in particular for hammers and similar-percussive tools, are simply made of wood, which, in the usual case. is hickory. There are many reasons why wooden handle tools are preferred over tools having handles of other materials, one of the more important reasons being that wood possesses a certain amount of resiliency or give. This resiliency is most desirable since it dampens the shock of an impact blow which otherwise would be transmitted to the handle to produce an uncomfortable stinging sensation. In the hands of a skilled user, the resiliency or give of a wooden handle tool is of equal importance in damp'ening undesirable harmonic vibrations which make it difiicult to strike a series of rapid blows squarely on the desired point of impact.
Another significant advantage of wooden handles is that they can be relatively inexpensively formed to have the desired proportions and dimensions so that, when the finished handle is combined with a head, the resulting tool will have the correct balance. This inherent advantage of wood is important, since, as is well known, an improperly balanced tool is difficult to aim and swing with accuracy and force. An improperly balanced tool also relatively quickly tires the wrist of the user.
In spite of their many functional advantages, woodenr coatings in an attempt to preserve the wood. These coat-v ings, however, wear` off in a relatively short time to expose the wood to dampness and other inclement conditions. Changes in the dampness and conditions of humidity to which the wood is exposed frequently cause the food to dry, swell, and crack, and, in some cases, to rot. In addition to the general deterioration of the wood itself, considerable diiculties are involved in fastening the metal impact head ofthe tool to the handle so that, as the wood dries, the head will not loosen and eventually separate from the handle. The exposed wood is also subject to being impregnated with .oil or other greasy substances, which results in the handle being too slippery to hold in the hand with an effective, tight grip.
Another disadvantage of wooden handles is that, when nited States Patent O ice the tool either is struck anvoff-center blow, or the head entirely misses the desired point of impact so as to subject the handle to physical impact, the wood fractures, thus rendering the tool useless. Not infrequently,lthe head of the tool breaks entirely away fromthe handle and strikes and injures the user or a nearby person. Even in the hands of an experienced workman, the wooden handles are easily bruised, so as to damage the cells in the wood, thereby destroying the resiliency of the handles andcausing the heads to loosenI on the handles.
Many attempts have been made in the past to find a substitute material, or combination of materials, for tool handles; however, to the best of my knowledge, none of the substitutes has been accepted by'tradesmen and other skilled users even though the disadvantages of wooden handles have, in many instances, been obviated. The principal reason for this is that the handle constructions heretofore known have not possessed the desirable characteristics of wooden handles, such as resiliency andbalance. For example, it has been proposed to form handles of steel andto' make the Vtool head an integral part of the handle. In use, this construction has been found undesirablesince the shock of the impact blow is transmitted directly through the rigid handle to the hand. In addition, harmonic vibrations are easily set up in the -steel handle, thus rendering the tool difficult and awkwarLto use. Attempts to dampen the shock and vibrations o steel handle tools by wrapping la shock absorbing material around the handle and inserting a similar material between the head and handle have been largely unsuccessful. Moreover, these refinements frequently make the tool s0 expensive as to be economically unfeasible.
Another disadvantage of the steel handle construction is that it is difficult and expensive to machine, forge, cast provide a reinforced wooden handle construction which is characterized by high strength and by resiliency and balance when combined with a tool head.
A further object is to provide a reinforced wooden handle construction which lends itself to a relatively inexpensive and easily performed manufacturing process, and which, at the same time, may be formed to have the correct balance and weight.
In general, the foregoing objects of the invention are attained by a novel handle construction wherein a conventional wooden handle is provided with a relatively thin, hard, resilient covering which, in the preferred embodiment, is bonded to the wood to form a permanent protective layer or skin By reason of this protective layer, the woodis protected against being bruised and' teriorating conditions encountered during normal use of the tool handle, the resin impregnated sleeve provides an advantageous safety feature of preventing the head of the tool and the handle from separating should the wood be fractured. For example, axe handles formed according to 4the invention will not separate even though the wood is fractured by a blow struck when the axe blade is not vertical or by the axe head missing the target and handle directly receiving the impact.
Another advantage of the foregoing manner of reinforcing tool handles is that the sleeve can be tensioned around the wooden handle and impregnated with resin relatively inexpensively and without destroying the balance of the tool. At the same time, the desirable resiliency of the wooden handle is not affected by the flexible reinforcing skin.
Other objects and advantages of the invention will become apparent when the same is considered in connection with the following detailed description and the accompanying drawing.
ln the drawing:
FIGURE l is a side elevational view, partially in crosssection, showing a hammer head provided with a handle formed according to the invention.
FIGURE 2 is an elevational view of the handle prior to being coated and impregnated with resin and assembled with the tool head.
Referring now to the drawing, the improved tool handle comprising the invention has been shown for illustrative purposes in combination with the metal head of a machinists ball peen hammer. It is to be understood, of course, that the handle is contemplated as being used in other percussive tools, as well as in applications involving the use of wooden shafts which are subject to occasional breaking stresses and/ or exposure to inclement conditions of dampness, water and so forth.
In FIG. l, reference numeral designates the hammer head having the customary eye 11 into which one end of the handle l2 is fitted. The union between the head and handle may be maintained by the usual wedge 13 or by other suitable means, such as a tapered shaft, screw or the like, as is well known in the art.
The handle 12 is comprised of a wooden core 17 having a filament-reinforced plastic skin 18 surrounding the sides and bottom end 19 of the core. Advantageously, the core 17 is simply a conventional wooden handle manufactured according to known procedures so as to have the correct proportions and to form a tool having the accepted balance when combined with an impact head. The particular wood from which the core 17 is formed is largely a. matter of choice depending primarily upon the expected stresses incurred during use of the handle, and ease and economy in shaping the wood. For example, hickory may be employed as is the usual case in non-reinforced wooden handles. Alternately, a softer and cheaper wood such as pine or the like may be used inasmuch as the skin 18 will contribute the needed strength and hardness which is required for the handles of most hand tools.
lin the preferred form of the invention, the skin 18 of the handle 12 comprises a fabric material 22 tightly surrounding the core 17, and a synthetic resin for impregnating and coating the fabric material and bonding it to the wood. A reinforcing fabric material which has been found desirable for the present application is nylon threads woven to form a tubular sleeve of sufficient length to cover the entire length of the wooden core 17. The elastic weave of the fabric sleeve 22 has been found particularly advantageous since it may be stretched to conform to the curved contours of the wooden core with a snug and smooth fit so as to form what is, in effect, an integral outer llayer on the wood.
While the preferred form of the invention has been disclosed as including a woven nylon sleeve, other fabrics and other materials also are suitable. For example, the reinforcing fabric may comprise a knitted, netted, or braided sleeve of sisal, cotton, fiber glass, and similar materials of relatively high strength. It also is contemplated that, instead of encasing the core 17 in aI onepiece fabric material, the core could be filament wound under tension in a helical pattern similar to that shown in FIG. 2.
The resin which is used to impregnate the fabric encased wooden core may be any synthetic resin which-will form a hard, tough, and fiexible layer on the handle. It
is preferred, however, that a thermosetting resin be employed which is settable at or above room temperature. Resins particularly adaptable to the present purposes are polyester resins, or epoxy resins which are combined with suitable setting agents, all being known in the art.
As shown in FIG. 2, the handle 12 is formed by first drawing the fabric sleeve 22 around the wooden core 17, and gathering and clamping the open, top end of the sleeve at the top of the core. The excess fabric is taken up, and the sleeve is stretched to ltightly bind the core, by forcing a portion of the closed end of the sleeve into a hole 25 in the bottom of the handle. The hole 25 may be permanently closed by means of a suitable plug 26.
When the fabric sleeve 22 is stretched around the core 17, the helical, angle of the fibers or strands Iwill vary throughout the sleeve length, with the helical angle being greater in the areas of minimum diameter of the core and relatively smaller in the areas of maximum diameter of the core. Thus, in the illustrated embodiment wherein the wooden core is shaped lto have a gripping area 28 of maximum diameter, a relatively smaller neck 29, an enlarged rib 30 at the upper end of the neck and an upper end 31 of smaller cross-sectional area, than the rib 30, the strands or fibers of the fabric will be more nearly parallel to the axis of the core 17 in the areas 29 and 31 than in the enlarged and stronger portions 28 and 30. Because of this varying angular disposition of the reinforcing filaments in which the strands in the thinner and weaker portions of the wooden core approach being normal to the shear stresses and bending moments applied to the reinforced handle during use of the tool, the reinforced handle of the invention successfully resists the exural breaking forces which normally cause breakage of conventional, unreinforced wooden handles of the type shown.
After the core 17 has been tightly encased in the sleeve 22, the assembly is dipped into a liquid resin bath to thoroughly saturate the fabric, following which the assembly may be hung vertically to allow the excess resin to drain from the handle as the resin sets. When the resin has bonded to the wood and has set, the resulting reinforced plastic layer forms an inseparable and permanent skin over the wood.
The hardened resin also is effective to form a gripping surface on the handle which may have either a smooth or a textured finish. In those instances where a relatively rough, ltextured finish is desired, a fabric having an open or rough mesh is employed so that after the resin has impregnated the interstices of the fabric and coated the fibers, the skin will be formed with ridges corresponding t0 the fiber pattern of the fabric. Alterna-tively a tighter fabric mesh and/or a small amount of ller in the resin for filling up the in-terstices of the fabric will produce a relatively smooth finish. Thus, it will be seen that proper selection of the fabric mesh will result in the reinforcing skin 18 having the desired finish.
In'the final step of assembly, the clamped, top end of the fabric sleeve 22 is clipped off and the upper end 31 of the handle is inserted into the eye 11 of the impact head 10. The wedge 13 maybe then driven into the upper end of the handle to create a firm union between the head and the handle. Inasmuch as the entire wooden core 17, including the upper end into which the wedge is driven, has been coated with the resin, the wood is permanently protected from exposure which heretofore has been the primary cause of the heads of tools loosening on the attached handles and eventually separating therefrom. Accordingly` it is possible to attach the head of thc tool to a handle formed according to the invention without resort to the relatively expensive cmislructions involving the usc of the special houding materials.
ln addition to protecting the wond from exposure, the reinforced plastic skin affords a handle construction which is substantially indestructible during normal use of the tool. Even though the wooden core should be fractured by an unusually seyerc impact force, the skin will prevent the head from separating from the handle. In many instances, it has been found that the strength of the skin is sufficiently great to permit the tool to be used for long periods of time after the wooden core has completely broken. At the same time, the resin `impregnated fabric sleeve is sufficient exible so that the formed handle possesses substantially the same degree of resiliency as the wooden core.
Other applica-tions of the invention herein described will be apparent to those skilled in the art in light of the above teachings. Therefore, it is to be understood that. within the scope of the appended claims, the invention may be practiced otherwise than as specifically shown and described.
What is claimed is:
1 A resilient, reinforced wooden handle comprising an elongated wooden core having zones of varying crosssect-ional area along its length and a taut, one-piece fabric sleeve tightly encasing said core, said fabric sleeve being disposed about said core so that strands of said fabric run helically about the core from end to end thereof, and said strands in the zones of relatively small cross-sectional arca more closely approach being axially aligned with the longitudinal axis of said core than in the zones of larger cross section, said fabric sleeve being impregnated, coated, and permanently bonded to said wood by a, synthetic resin to form a tough, flexible, and water impervious skin, whereby the core is protected from exposure and is strengthened against flexural breaking forces.
2. In a percussive hand tool having an impact head, a handle-receiving eye through said head, and a resilient handle having one end firmly received and held within said eye, an impro-ved handle construction comprising a wooden core, said wooden core having zones of varying cross-sectional area along -its length, and a plurality of taut, reinforcing filaments helically wrapped around said core with the helical angle of said wrapped filaments being substantially greater in thc zones of relatively smaller cross-sectional area of said core than in the zones of lrelatively large cross-sectional area, said reinforcing filaments heini; imt'ircgnated` coated and permanently bonded to said wooden core by a synthetic resin, said impregnated and coated reinforcing filaments being wrapped around said core and permanently bonded thereto from end to end thereof, including the portion of its length within said eye.
3. In a hand tool including Ia head,
a handle-receiving eye through said head, and a reinforced handle having one end firmly received and held within said eye,
said handle comprising a wooden core and a fabric sleeve tightly enc-asing the entire length of said core, including the portion of its length within said eye,
said core being formed with zones of varying crosssectional area,
the strands of said sleeve in the zones of relatively small cross-sectionall area more closely approaching being normal to the sheer stresses and bending moments applied to said handle during use of said tool than in zones of larger cross-sectional area,
said sleeve being impregnated, coated and bonded to sa-id core by a synthetic resin to form a tough, permanent, protective skin having approximately the same degree of resiliency as said core,
whereby said corc is protected from exposure andphysical abuse, and whereby said head is prevented from loosening and separating from the said handle.
References Cited in the file of this patent UNITED STATES PATENTS 1,401,896 Ehrhart Dec. 27, 1921 2,201,706 Sukohl May 21, 1940. 2,535,033 Bergere Dec. 26, 1950 2,656,294 Hunt Oct. 20, 1953 2,837,381 Sarlandt June 3, 1958 2,940,492 Curry et al July 14, 1960 2,950,112 Dettman Aug. 20, 1960 2,955,642 Stark Oct. 11, 1960 v 3,025,062 Dufn Mar. 13, 1962 FOREIGN PATENTS 131,311 Sweden Apr. 10, 1951