US3669512A - Impact tool and compound handle-retaining wedge therefor - Google Patents

Abstract

A COMPOUND WEDGE ADAPTED TO BE PRESSED INTO THE CONFORMABLY SLOTTED DISTAL END OF A FRESH WOODEN IMPACT TOOL HANDLE IN ORDER TO SPREAD SUCH END AND COMPRESS THE WOOD THEREOF OUTWARDLY AGAINST THE WALLS OF THE EYE IN THE HEAD OF THE IMPACT TOOL AND THUS PERMANENTLY TIGHTEN THE HANDLE AND HEAD TOGETHER. THE WEDGE EXERTS A SPREADING ACTION IN BOTH LATERAL DIRECTIONS AND IT IS COMPRISED OF A RESILIENT COMPRESSIBLE PLASTIC MATERIAL HAVING A MODULUS OF ELASTICITY WHICH SUBSTANTIALLY MATCHES THE SHRINKAGE AND EXPANSION FACTOR OF THE WOOD WHICH IT DISPLACES SO THAT, AS THE MOISTURE CONTENT OF THE WOOD EVAPORATES AND AND SHRINKAGE TAKES PLACE, THE RESTORATIVE PROPERTY OF THE WEDGE COMPENSATES FOR SUCH SHRINKAGE. CONVERSELY, AS THE SHRUNKEN WOOD ABSORBS MOISTURE AND REGAINS SIZE, THE WEDGE IS FORCIBLY CONTRACTED. THUS, IN ANY CONDITION OF THE WOOD, THE HANDLE REMAINS TIGHT. AN IMPACT TOOL EMBODYING SUCH A WEDGE.

Description

June 13, 1972 w, c, P R s 3,669,512

IMPACT TOOL AND COMPOUND HANDLE-RETAINING WEDGE THEREFOR Filed Nov. 18, 1970 IIVVENTOR. WORTHEL 6. PARKS United States Patent Ofice 3,669,512 Patented June 13, 1972 US. Cl. 306-33 1 Claim ABSTRACT OF THE DISCLOSURE A compound Wedge adapted to be pressed into the conformably slotted distal end of a fresh wooden impact tool handle in order to spread such end and compress the wood thereof outwardly against the walls of the eye in the head of the impact tool and thus permanently tighten the handle and head together. The wedge exerts a spreading action in both lateral directions and it is comprised of a resilient compressible plastic material having a modulus of elasticity which substantially matches the shrinkage and expansion factor of the wood which it displaces so that, as the moisture content of the Wood evaporates and shrinkage takes place, the restorative property of the wedge compensates for such shrinkage. Conversely, as the shrunken wood absorbs moisture and regains size, the wedge is forcibly contracted. Thus, in any condition of the wood, the handle remains tight. An impact tool embodying such a wedge.

The present invention relates generally to portable impact tools and has particular reference to that class of impact tools which is exemplified by hammers, axes, hatchets, mallets, picks, and the like. More particularly, the invention relates to that type of impact tool which consist of a metallic head to which there is attached a manipulating handle of wood.

The problem of maintaining a wooden handle permanently in tight fitting relationship within the eye in the head of a claw hammer or similar impact tool has long plagued tool manufacturers. Considering, for example, a claw hammer having a hickory handle, it has heretofore been the practice to slot the distal end of the handle and to drive one or more wedges into the slot or slots in order to spread the slot-formed wooden tines apart and compress them against the opposite side walls of the eye in the hammer head. This procedure is not altogether satisfactory inasmuch as, upon drying out of the wood of the handle, shrinkage takes place with the result that the wedge and the adjacent portion of the handle become loose and, consequently, the handle and head are no longer securely maintained in connected relationship. In order to inhibit wedge dislodgment, wedges having serrated flat sides have heretofore been proposed, but the involved improvement is slight inasmuch as looseness of the handle in the head still takes place when usual shrinkage of the wood takes place. This is not surprising when it is considered that hickory, as commonly used for the ha11- dles of hammers and other impact tools, has a moisture content on the order of from 8% to 12% at the time of wedge installation. The users of claw hammers and other impact tools, in an effort to alleviate the shortcomings of the manufacturers, frequently augment the wedging action of the original wedge or wedges by driving one or more nails into the eye of the hammer head, or by fashioning makeshift wedges from wooden chips and driving them in place. Nails invariably work loose as further drying of the wood of the handle takes place, while wooden wedges are themselves subject to shrinkage in time. Furthermore, once any looseness, however small, takes place, repeated impact blows by the hammer on the work progressively increases such looseness.

The present invention is designed to overcome the above-noted limitations that are attendant upon the use of conventional wedges in connection with handle-to-head securement and, toward this end, the invention contemplates the provision of a novel impact tool wedge which is formed. of a molded thermoplastic material having a modulus of elasticity which substantially matches the dehumidification shrinkage factor of the wood of the handle to the tool, and also matches the expansion factor thereof when water absorption takes place. In order to install the wedge in position within the eye of the head of the tool, the distal end of the handle (which is conformably shaped to the cavity which is presented or formed by the eye) is slotted two ways, i.e., by intersecting slots which extend at right angles to each other and the wedge is of a compound nature and is conformably X-shaped so that it will fit into the intersecting slots. The radial wedge arms are individually divergent from thin forward edges to relatively thick rear edges so that when wedge and slot registry is attained and the wedge pressed forwardly into the eye of the head, the four wooden tines which are established by the slotting operation are not only spread radially apart but they also are individually compressed on all four sides. Each wedge arm is formed with a recess in one side thereof and into such recess the opposed inside face of the associated wooden tine projects as the compound Wedge is pressed or driven home, thus affording a pronouncedly secure locking action which holds the wedge against dislodgment. By such an arrangement and procedure, as the moisture content of the wood of the handle evaporates and shrinkage takes place, the restorative properties of the plastic material of the wedge maintains the four wooden tines under compression, even after the handle is substantially devoid of moisture. Conversely, when the Wood of the handle absorbs moisture as the wood swells and tends to regain its original size, the resilient wedge is compressed. Such alternate plastic and wood displacements serve to maintain the eye of the head completely filled with material under compression. Furthermore, the long and the short transverse dimensions of the wedge match those of the eye so that, regardless of wood shrinkage, the eye remains devoid of cavities and at all times is completely filled to the end that there is no handle looseness.

The provision of a wedge of the character briefly outlined above and possessing the stated advantages constitutes the principal object of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood by a reading of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by the claims at the conclusion hereof.

In the accompanying single sheet of drawings forming a part of this specification, one illustrative embodiment of the invention is shown.

In these drawings:

FIG. 1 is an exploded side elevational view of a carpenters claw hammer embodying the present invention and showing the hammer head, handle and the novel wedge aligned with one another preparatory to pressing the handle and wedge together within the eye of the hammer head;

FIG. 2 is a transverse section on the line 2-2 of FIG. 1;

FIG. 3 is a top perspective view of the wedge;

FIG. 4 is a bottom perspective view of the wedge;

FIG. 5 is a top plan view of the wedge;

FIG. 6 is a bottom plan view of the Wedge;

FIG. 7 is a side elevational view of the wedge;

FIG. 8 is an end elevational view of the wedge;

handle and hammer as represented by the line 10 of FIG. 1; and

FIG. 11 is an enlarged sectional view taken on the line 1111 of FIG. 10.

Referring now to the drawings in detail and in particular to FIGS. 1 and 2, a carpenters claw hammer which, except for the incorporation therein of the wedge of the present invention, is of conventional construction, is designated in its entirety by the reference numeral 10 and consists of a steel head 12, a wooden handle 14, and a wedge 16. The wedge 16 constitutes the principal feature of the present invention and is illustrated in detail in FIGS. 3 to -8, inclusive. Although a carpenters claw hammer has been selected as an exemplary impact tool to which the handle and wedge may be applied in accordance with the principles of the present invention, it should be distinctly understood that the handle and wedge may be associated with a wide variety of impact tools as, for example, an axe, adz, hatchet, sledge, mallet, or the like. Irrespective, however, of the particular use to which the invention may be put, the essential features thereof are at all times preserved.

The illustrated hammer head 12 is conventional and includes an impact head proper 20 having a circular impact face 22. The head proper 20 is connected to one side of the medial body portion 24 by a constricted portion 26 which may, if desired, be polygonal in cross section. The other side of the body portion 24 of the head 12 is connected to a claw portion 28, the latter being bifurcated as at 30 (see FIG. 9) in order to provide the usual diverging nail-removing claws 32. The medial body portion 24 is formed with a central opening having a straight-sided section 34 and a slightly tapered rim section 35, the opening extending completely through the body portion and establishing a pair of relatively thin side walls 36 and end walls 38. This generally rectangular central opening 34 is commonly referred to as the eye of the hammer head and it will be referred to as such throughout the remainder of this specification and in the appended claims.

Except for the provision of a pair of wedge-receiving slots 40 and 42 (see FIG. 2') which are formed in its distal end region, the handle 14 is conventional and, for purposes of discussion herein, it is stated to be formed of a good grade of hickory. Said handle 14 is provided with a rectangular eye section 44 and a hand grip section 46. The two slots 40 and 42 are formed in the free end part of the eye section 44 of the handle 14 and intersect each other. The slot 40 extends across the long dimension of the eye section 44 and the slot 42 extends across the short dimension thereof, the two slots thus defining four parallel tines 48 at the distal end of the handle (see FIG. 10). The depth of the slots 40 and 42 is preferably somewhat less than the over-all length or longitudinal extent of the Wedge 16 for purposes that will be made clear presently.

' Considering now the shape characteristics of the wedge 16, and referring particularly to FIGS. 3 to 8, inclusive, this wedge is formed by an injection molding operation from a particular thermoplastic material and it consists of a central axial hub portion 50 from which there projects radially outwardly in four directions a series of wedge arms. The latter consists of two aligned long arms 52 and two aligned short arms 54, the arms 52 and 54 extending at a right angle to each other so that the wedge, considered as a whole, is generally of X-shape in cross section. As best illustrated in FIGS. 7 and 8, each of the four arms is of individual wedge configuration, which is to say that it is substantially of isosceles triangular configuration in vertical section so that the wedge as a whole is provided with a relatively thick X-shaped top face 56 as shown in FIG. 3 and a relatively sharp X-shaped bottom edge 58 as shown in FIG. 4. Small parallel side areas 59 at the large end of each wedge arm may be provided if desired, but these areas detract only slightly from the isosceles aspect of the wedge configuration. The two long arms 52 of the wedge 16 define generally triangular outer end faces 60, while the two short arms 54 similarly define generally triangular outer end faces 62. The medial region of each of the four arms is formed with a semi-cylindrical concavity 64, the axis of which extends horizontally as viewed in FIGS. 7 and 8 with the various concavities facing in a generally counterclockwise direction as viewed in FIG. 6.

The plastic material from which the wedge 16 is formed is of a special nature and possesses physical characteristics which will be described presently after the mode of assembly of the claw hammer 10 has been set forth. In assembling the handle 14, the hammer head 12, and the wedge 16 in order to produce the claw hammer 10, the eye section 44 of the handle 14 is introduced into the eye 34 of the hammer head 12 to the fullest extent of which it is capable of being received and, when thus introduced, it substantially fills the eye 34 except for the voids which exist by reason of the intersecting or crossed slots 40 and 42. The distal end face of the handle 14 at this time lies substantially in the general plane of the rim of the eye 34 and there is a fairly snug fit between the walls 36 and 38 of the eye and the outer sides of the eye section 44 of the handle 14.

With the eye section 44 thus inserted into the eye 34, the assembly is then placed in a press and the wedge 16 is forced into the slots 40 and 42, the tapered long arms 52 entering the slot 40 and the tapered short arms 54 entering the slot 42. The handle and wedge are placed under approximately 3,000 pounds compression which is sulficient to drive the wedge to its home position wherein the thick X-shaped top face 56 thereof lies in the general plane of the rim of the eye 34. Since the over-all extent of the wedge in the longitudinal direction of the hammer handle is less than the depth of the slots 40 and 42 as previously stated, the wedge bottoms in the slots before it reaches its home position and, thereafter, it penetrates the wood of the handle at the bottom of the slots and becomes embedded therein. The wedge thus becomes submerged in the wood to such a depth that the aforementioned concavities 64 become substantially completely filled with wood at the time the wedge reaches its home position, the wood flowing into such concavities, so to speak, by reason of its inherent resiliency or elasticity.

It is essential that the wedge 16 be applied to the handle 14 by a pressing operation as described above inasmuch as it has been found that impact blows on the wedge, as is customary when driving conventional wedges in position, are inadequate for the purpose intended. Although the first few blows will be adequate partially to drive the wedge into the slots 40 and 42, as the wedge begins to tighten beyond a certain limit a bouncing action will take place wherein the wedge will pop out of the slots in between blows. After the wedge has thus been driven to its home position, the four concavities 64, which become interlocked with the wood, serve to retain the wedge in position against dislodgment by reason of certain physical phenomena that will become apparent after the nature of the plastic material of the wedge and the physical nature of the hickory or other wood from which the handle 14 is formed have been set forth.

As previously stated, the wedge 16 is injection-molded from aparticular thermoplastic material which is resilient and compressible and which possesses restorative properties whereby it will tend to assume its original state or configuration after deforming pressure is relieved. Furthermore, the modulus of elasticity of the plastic material of the wedge closely matches or is slightly in excess of the shrinkage factor of the wood from which the handle is formed. Thus, during pressing of the wedge 16 into the slots 40 and 42 under high pressure as previously described, compression resulting in a shrinking of volume of both the wedge and the eye section 44 of the handle 14 takes place while the density of both materials is increased. Specifically, as the wedge is being driven to its home position, inward centripetal force is applied to each time as adjacent tapered sides of adjacent arms 52 and 54 tend to force the tines toward the corners of the eyes. At the same time, each of the arms 52 and 54 is placed under inward compression. Thus, a reduction in volume of both the four tines and the wedge as a whole takes place and, when the wedge reaches its final home position, shrinkage due to compression of the tines 48 and the wedge 16 has taken place. The eye section 44 of the handle 14 is, therefore, securely wedged in position within the eye 34 of the hammer head 12.

It is to be noted at this point that, due to the existence of the four concavities 64 in the sides of the arms 52 and 54, the compressional forces acting on the opposed regions of the tines is not as great as elsewhere so that the wood of the eye section 44 enters these concavities and establishes an interlock between the wedge and the eye section 44 of the handle so that the wedge 16 will not work loose and become dislodged from the eye 34.

The compressional shrinkage just described in connection with the four tines 48 is not to be confused with the free physical shrinkage or contraction which takes place by reason of drying out of the wood of the handle 14 in point of time after the hammer has been marketed. Conventional hickory handles have a moisture content of approximately from 8% to 12% at the time the wedges are driven, and after a particularly dry period, this moisture content is reduced to as low as 4%, resulting in a very appreciable contraction.

According to the present invention, because of the fact that the modulus of elasticity of the plastic material of the wedge 16 substantially matches the shrinkage and expansion factor of the wooden handle 14 as previously stated, as the various tines 48 contract progressively under the influence of dehumidification thereof, the restorative properties of the then compressed arms 52 and 54 of the wedge 16 cause them to compensate for such wood shrinkage. Conversely, when a dried out handle assimilates moisture and exhibits its own restorative properties, the swelling thereof compresses the plastic material of the wedge and the hammer assembly tends to assume its original condition. Thus, at no time, regardless of the prevailing condition of humidity, will the eye section 44 of the handle become loosened in the eye 34.

Various thermoplastic materials may be found suitable for use in connection with the injection molding of the wedge 16, the only criterion being that the modulus of elasticity thereof substantially matches or slightly exceeds both the shrinkage and expansion factors of the hickory or other wood which is employed in the construction of the hammer handle 14 for the purposes herein described. One such material is manufactured and sold by General Electric Company of Schenectady, New York under the trade name Lexan, although other materials may be found suitable for the purposes intended. An additional advantageous property of the plastic material Lexan resides in its toughness and ability to withstand the installation pressure of wedge installation. The material also is shock-resistant and is not afiected by impact blows when the hammer is put to use.

It is to be noted from an inspection of FIGS. 7 and 8 that the two outer end faces 60 of the long arms 52 and the two outer end faces 62 of the short arms 54 are inclined toward each other so that the wedge as a whole is tapered in two directions. This tapering of the wedge is intended to match the taper of the walls 36 and 38 of the eye 34 inasmuch as these outer end faces 60 and 62 fit against these Walls at the time that the wedge, during pressing thereof into the slots 40 and 42, reaches its home position.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. For example, the specific wedge angle of the various arms 52 and 54 illustrated in the drawings measures an angle on the order of 10. It is obvious that a greater or a lesser wedge angle may be employed if desired, the optimum wedge angle depending upon numerous factors such as the dimensions of the eye 34 and of the eye section 44 of the handle 14, as well as upon the depth of the slots 40 and 42. Therefore, only insofar as the invention is particularly pointed out in the accompanying claim is the same to be limited.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. An impact tool comprising a head having a tapered, generally rectangular handle-receiving eye formed therein and presenting four inwardly sloping side wall surfaces, a wooden handle having an eye section at its distal end region and projecting into said eye, and a resilient compressible plastic wedge embedded in said eye section under compression for tightening the later within the eye, said eye section being pre-formed with a pair of intersecting slots which extend inwardly from the distal end face of the handle and define four generally parallel tines, said wedge being generally of X-shape in cross section and presenting a central hub portion and four radial wedge arms each with opposed planar side faces and each of which is of tapered configuration in the longitudinal direction of the wedge and presents a generally trianguar outer end face which bears coextensively against one of said side walls, each wedge arm being formed with a single semi-cylindrical concavity in one slanting side face thereof for interlocking engagement with the compressed wood of the eye section, each pair of adjacent wedge arms, in combination with an adjacent corner region of the eye, serving to displace and compress the wood of one of the tines and thus frictionally maintain the eye section of the handle tightly received within the eye, the modulus of elasticity of the plastic material of the wedge being at least equal to the dehumidification shrinkage and expansion factor of the wood which it displaces whereby, upon shrinkage of said tines due to dehumidification thereof, expansion of the compressed wedge will maintain the tightness of the eye section of the handle within the eye of the head.

References Cited UNITED STATES PATENTS 291,851 1/1884 Murphy 306-33 194,391 8/1877 West 306-33 477,082 6/1892 Thompson et al 306-33 532,366 l/1899 Duniap et a1 306-33 463,417 11/1891 Carver 306-33 3,341,261 9/1967 Fenlin 306-33 3,232,160 2/1966 Fork et a1 287-127 R 2,318,975 5/1943 Stanley 306-32 2,947,040 8/ 1960 Schultz 28720.92 R

FOREIGN PATENTS 996,400 6/1965 Great Britain -29 ANDREW V. KUNDRAT, Primary Examiner US. Cl. X.R. 287127

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