US3578825A

US3578825A - Hand tool

Info

Publication number: US3578825A
Application number: US740178A
Authority: US
Inventors: George W Merrow; Robert F West
Original assignee: Stanley Works
Current assignee: Stanley Works
Priority date: 1968-06-26
Filing date: 1968-06-26
Publication date: 1971-05-18
Anticipated expiration: 1988-05-18
Also published as: GB1232514A; FR2011693A1; JPS5020698B1; SE357514B; DE1930234A1

Abstract

A hammer is provided with a glass fiber reinforced handle having a tenon-shaped end portion in pressuretight engagement with the eye of the hammer head. The handle, which is securely connected to the hammer head without the necessity for separate wedging members or materials, is spaced from the head at the inner end of the eye while being in intimate surface contact therewith along the plane of percussion for a distance of approximately twothirds the axial length of the eye. The shank and grip portions of the glass fiber reinforced handle are dimensioned to permit mounting of the handle by passing the shank and handle portions through the eye. Additionally, the handle is self-aligning within the eye by means of a pair of opposed handle aligning ribs which also serve to confine an auxiliary bonding material.

Description

United States Patent 2,917,349 12/1959 Sayloretal. 2,940,492 6/1960 Curry etal l45/29(X) l45/29(X) ABSTRACT: A hammer is provided with a glass fiber reinforced handle having a tenon'shaped end portion in pressuretight engagement with the eye of the hammer head. The handle, which is securely connected to the hammer head without the necessity for separate wedging members or materials, is spaced from the head at the inner end of the eye while being in intimate surface contact therewith along the plane of percussion for a distance of approximately two-thirds the axial length of the eye. The shank and grip portions of the glass fiber reinforced handle are dimensioned to permit mounting of the handle by passing the shank and handle portions through the eye. Additionally, the handle is self-aligning within the eye by means of a pair of opposed handle aligning ribs which also serve to confine an auxiliary bonding material.

mun TOOL BACKGROUND AND SUMMARY OF THE INVENTlON Thisinvention relates generally to handtools. More particularly it is directed to a new and improved connection between the handle and head of hammers and similar handtools.

lt has long been the practice to use wooden handles in handtools such as hammers, hatchets and other tools suitable for percussive use because of their excellent and natural shock absorbing characteristics coupled with their characteristically preferred balance, weight, durability and cost. Such wooden handles generally are provided with a gripping portion of comfortable hand size which usually exhibits an enlarged cross section relative to the eye of the tool head. As a result the handles are conventionally inserted into the outwardly tapered eye of a tool head from the inner end thereof. The handles are then secured within the eye by means of one or more wedges driven into the handle from the eyes outer end. Thereby, the wedge or wedges cause the handle to expand within the eye into interfering locking engagement with the diverging walls of the eye. Unfortunately, such handles and their traditional securing means have been known to provide less than fully satisfactory performance upon prolonged use due to their susceptibility to loosen under various adverse environmental operating conditions. For example, the separate wedges used to secure the handle have tended to work loose over extended periods of time as a result of the percussive and vibratory forces acting on the tool head. Additionally, adverse ambient moisture conditions have caused alternate expansion and contraction of the wooden handles, resulting in both the compressive destruction or crushing of the internalwood fiber structure and the alternate shrinking thereof. Eventually, the connection between the handle and the head loosened to the point of complete failure.

Alternative securing means and handle materials have been employed in an attempt to overcome these deficiencies. However, none of the proposed alternatives have proven entirely satisfactory. For example, the expedient of providing a cushion within an annular space between the handle and the inside walls of the eye isolated the handle from the vibrations set up in the tool head during impact. This isolation prevented dampening of the vibrations by the handle and permitted the tool head to resonate in the manner of a tuning fork, causing stresses which resulted in the cracking or eventual failure of the tool head. The use of metal handles tended to transmit the, shock and vibratory forces back to the hand of the operator without substantial dampening while at the same time disadvantageously altering the weight, center of gravity and balance of the tool. Unfortunately, attempts to provide conventional connections for fiber glass reinforced handles which possess an ability to absorb at least a portion of the shock transmission and vibration, have met with failure. When internally wedged they tend to split and delaminate. When externally wedged, the fiber glass handles were found to fray and splinter at their points of contact with the edges of the tool head. This was particularly true when the tool head contacted the handle at the inner or grip end of the eye and the tool handle was subjected to leverage stresses such as when the tool head tended to cut into the glass fibers causing splintering, fraying and delamination coupled with weakening of the tool handle at the point of abrasive contact with the tool head and undesirable skin irritation to the user. it should also be noted that where the handle was not flush with the tool head at the outer end of the eye and the tool was used for pulling nails on finished work, the narrow edges of the head surrounding the eye tended to cause undesirable indentation in the work product.

Accordingly, the present invention has as an object the provision for a new and improved handtool of the type described which includes a firm, secure handle connection of prolonged operating life, the connection obviating the nccessb ty for separate wedging members or material and eliminating many of the deficiencies heretofore associated therewith while at the same time retaining the advantageous features thereof.

Another object of the present invention is to provide a new and improved handtool wherein the forces acting on the tool head upon percussive use thereof are selectively dissipated duringtransmission thereof to the tool handle thereby reducing the required dampening of shock transmission within the handle. Included in this object is the provision for secure intimate contact between the handle and the tool head over a short axial length of the eye localized at the percussive axis of the tool head, thereby restricting direct transmission of the shock forces through a shorter supporting distance on the handle while at the same time providing a smaller area of resistance to the vibratory motion of the head.

An additional object of the present invention is to provide a new and improved handtool of the type described which not only facilitates a lower shock transmission to the handle despite intimate contact with the tool head, but also facilitates the utilization of handles exhibiting improved dimensional stability under ambient conditions and greater tensile strength and resistance to compression.

Still another object of the present invention is to provide a new and improved handtool having a connection between the handle and the tool head which is devoid of separate wedging members and permits the use of fiber reinforced handles while substantially eliminating abrasive edge contact between the head and the handle and reducing potential areas of high stress concentration, thereby substantially obviating the undesirable fraying, splitting and delamination evidenced heretofore.

A further object of the present invention is to provide a small handtool of the type described which includes a handle having a self-locking tapered connection with the tool head, the connection including intimate'contact between the handle and the head at the axis of percussion of the tool head and positive spacing therebetween permitting limiting oscillation of the tool head. 7

A further object of the present invention is to provide a new and improved tool handle of light yet durable construction and of sufficient resilience to absorb shocks and jars incident to its use, yet being readily insertable and self-aligning within the eye of the tool head during assembly and providing a pressuretight self-locking connection therewith when assembled even in the absence of additional bonding means; the handle further providing positive interference to centrifugal and momentum forces to which the tool head is subjected during use while obviating points of stress concentration within the handle despite the leverage strains to which the tool is subjected.

Still another object of the present invention is to provide a handtool of the type described having a handle which extends through the full length of the eye and provides intimate contact with the surfaces of the eye at the curved outer end thereof to provide the back of the tool head with a smooth, flush surface which minimizes the concentration of forces and prevents formation of indentations or marks on finished work when using the tool for pulling nails or the like.

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The above and related objects are accomplished in accordance with the present invention by providing a tool handle with a flared or tenon head portion which fits within the eye of the tool head so as to provide full surface contact along the front and rear walls of the eye within the environs of the axis of percussion while at the same time providing a gap or space between the handle and the tool head at the inner or handle end of the eye. This construction facilitates the assembly of the handle on the head by passing the full length of the handle through the eye from the back of the tool head,

utilization of interference engagement without separate wedging members and the elimination of sharp edge contact between the handle and the hammer head. The connection is particularly well suited for use with fiber reinforced handles and provides for both alignment during assembly and auxiliary bonding between the sides of the handle and the sidewalls of the eye.

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application which will be indicated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a fragmented side view, partially broken away, of a hammer incorporating the features of the present invention; and

FIG. 2 is a fragmentary sectional view taken along the lines 2-2 of FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing in greater detail, wherein like reference numerals indicate like parts throughout the FIGS., there is illustrated a claw hammer, generally designated by the numeral 10, which is constructed in accordance with the present invention to provide a secure pressure-tight connection between a hammer head 12 and a handle 14. The particular hammer head 12 used to illustrate the present invention is provided with a conventional poll and bell I6 and bifurcated claw 18 separated by a central portion 20 having a downwardly projecting shank or boss 22. The usual eye 24 of the hammer head extends through the central portion 20 and shank 22 along an axis generally perpendicular to the medial axis 26 of the poll and bell which, for the purpose of discussion, can be considered to be substantially coincident with the axis of percussion of the hammer head 12. The eye 24 is of generally rectangular cross-sectional configuration and extends from its inner or handle end within the shank 22,

through the entire hammer head I2 is an axially symmetrical manner, terminating at its enlarged outer end along the back 28 of the hammer head. As clearly seen in FIGS. 1 and 2, the eye 24 converges or tapers inwardly from its outer end along a major portion of its length and then progresses in a generally unchanging manner through shank 22. Thus, along a distance equal to approximately three-quarters and preferably twothirds the total length of the eye. front and rear

eye wall portions

32, 34, respectively, converge inwardly from the back 28 of the hammer head to provide an eye opening of mortise eonfiguration. The sidewall portions 36 of the eye also taper slightly along the same axial distance but the taper is negligible relative to that defined by

wall portions

32, 34. As mentioned, the inner or handle end portion of the eye within the shank 22 is not tapered in the same manner and, as in the embodiment illustrated, may have no taper whatsoever.

The tool handle 14 is preferably formed of a fiber reinforced material. The handle 14 is an elongated member of generally rectangular cross section and includes a rodlike grip end portion 40 shown as having an elliptical sectional configuration which is joined to a tenon-shaped head portion 42 by an integral shank portion 44 extending forwardly from the grip portion 40 toward the hammer head. The shank portion 44 is slightly enlarged relative to the grip end portion 40 and includes substantially flat top and

bottom surfaces

48, 50 which start to gradually taper in a diverging manner about midway along the shank until they reach the head portion 42 located within the eye of the tool head. As the top and

bottom surfaces

48, 50 diverge, the convex sidewalls 52 of the shank portion gradually assume a substantially flat configuration thereby smoothly blending into the flat sided, generally rectangular configuration of the head portion 42 and providing a cantilever beam construction at the important grip end of the eye. In accordance with the present invention the width and depth of the handle throughout the grip and shank portions are substantially smaller than the eye 24 and are configured so as to readily pass through the eye of the hammer head from the outer end thereofwithout substantial interference.

It is an advantageous feature of the present invention that secure pressure-tught interengagement is provided between the hammer head 12 and the head portion 42 of the handle This is effected by providing the handle head 42 with tapered top and

bottom surfaces

56, 58 angularly oriented so as to impart to the head a dovetail or diverging tenon configuration. As the handle is mounted within the eye 24, the

surfaces

56, 58 come into confronting relationship with the converging rear and

front walls

34, 32 respectively of the eye. Preferably the

surfaces

56, 58 define a self-locking included angle equal to or, slightly larger than the angle defined by the front and rear walls of the eye thereby assuring tight intimate contact between the head and the handle at the area of intersection by the axis of percussion 26 after pressure mounting of the handle on the head. This self-locking taper provided on the head 42 of the handle is preferably an included wedging angle of between about 8 and 12. In this regard it has been found that an angle of less than 8 results in undesirable variations in the ultimate handle length due to manufacturing tolerances of the eye while handle tapers greater than 12 may not be adequate to prevent disassembly under certain conditions of extreme use. Accordingly, in practice an included angle of approximately 9 is preferred for the handle head. As mentioned, the taper defined by the front and rear walls of the eye may coincide with the taper of head portion 42 of the handle. However, it is generally preferred that the angle defined by these walls be slightly less than the angle of the head portion of the handle, i.e., about 8-9, so that as the handle 14 is assembled therein under pressures of about 3 tons, a firm and secure locking engagement is provided between the handle and the walls of the eye.

Since the front and rear walls of the eye taper through only approximately two-thirds of the length of the eye while the top and bottom surfaces of the handles head portion continuously taper through the full axial length of the eye, a space 66 between the handle and the shank 22 is positively provided adjacent both the top and

bottom surfaces

56, 58 at the inner or handle end ofthe eye. Thus, it can be seen that direct and intimate surface contact is provided between the handle and the head of the tool at the axis of percussion and for a limited axial distance on each side thereof in order to provide for the direct transmission of shock forces to the handle. However, it is an advantage of the present invention that the contact is along only a limited length of the eye, the shank 22 being spaced from the handle at its free end to permit limited oscillation of the head relative to the handle. In this way the connection enables the utilization of handle materials which do not possess the full damping characteristics of wood while the taper and tight pressure fit provide locking interference to the centrifugal forces acting on the hammer head during use.

As best seen in FIG. 2, the head portion 42 of the handle is preferably of lesser width than the eye along a major portion of its length but is enlarged at 72 adjacent its free end to provide a snug fit with the hammer head about the outer perimeter of the eye. In this manner the present invention provides a handle connection which completely fills the outer end of the eye and exhibits a smooth, flush and continuous back surface on the head of the hammer thereby preventing undesirable indentation of the finished work product when the hammer is used to pull nails.

Spaced from the enlarged end portion 72 of the handle head toward the inner end of the eye and enclosed by the sidewalls of the shank 22 are a pair of transversely extending ribs 74 integral with and protruding from the sidewalls of the handle head. The ribs 74 are of sufficient thickness to contact the sidewalls of the eye upon insertion of the handle head therein and maintain the handle in full alignment until it is firmly secured within the eye. The ribs 74 in conjunction with the enlarged end portion 72 define a pair of side recesses which extend across substantially the full transverse dimension of the eye. Thus, although a bonding agent is not absolutely necessary in accordance with the present invention, the recesses defined by the side ofthe hammer head and eye are well suited for receiving a suitable bonding material, such as an epoxy resin, ifsuch is deemed desirable. The bonding material serves primarily to assist in retaining the handle within the eye of the hammer head. Thus, the ribs 74 facilitate not only the alignment of the handle within the hammer head during initial assembly and prior to pressure locking therein but also enable utilization of an auxiliary bonding material, such as epoxy, to be inserted within cavities located on each side of the handle. Additionally, a small locating bead 76 is provided on enlarged portion 72 at its inner end, the bead extending about three sides of the handle head 42 and being substantially sheared off or flattened upon pressure attachment of the handle to the tool head. As shown in FIG. 2, the ribs 74 permit the positive space 66 between the shank 22 and the handle to completely circumscribe the handle at the inner end of the eye. It will, of course, be appreciated that a minor amount of the adhesive material may unavoidably flow into a portion of the space 66 between the shank 22 and the handle without substantially interfering with the advantages of the present invention. Additionally, aesthetic considerations may require that the space 66 be filled with a resilient material such as a silicone resin or that a sleeve be provided to cover the open end of the space without interfering with the improved functioning of the connection.

As mentioned hereinbefore, the preferred handle material for use in the assembly of the present invention is molded fiber reinforced plastic. Such material is less susceptible than wood to dimensional variations under differing ambient humidity conditions and exhibits higher tensile strength and greater resistance to compressive forces than the heretofore conventionally employed wooden handles. Typical of the materials which have proven most effective are the glass fiber reinforced polyesters. Preferably nonwoven filaments of fiber glass extend continuously from the grip end 40 of the handle to the head portion 42 thereof and constitute approximately 60 percent by weight (about 40 percent through 45 percent by volume) of the handle. The continuous filaments or strands have an average diameter of approximately three-tenths mils and are embedded within and encompassed by the resin. As will be appreciated some of the fibers will be positioned adjacent the exterior surface of the handle and enhance the tensile strength of the handle. In practice a compression molding technique has been found to provide the desired structural integrity and aesthetically pleasing appearance for such handles. It will, of course, be appreciated that due to the variation in the cross-sectional area of the handle from the head portion to the grip portion, the fibers will form a greater part of the cross section of the grip end of the handle and fillers may advantageously be added to the handle head to enhance the shock absorption characteristics thereof.

To further minimize any vibrations which may be transferred to the hand of the user through the handle, the grip portion 40 thereof is provided with a circumscribing sheath or grip 78, preferably formed of rubber or like material, which is permanently bonded to the handle by a suitable adhesive. The outer surface of the circumscribing grip tapers inwardly to merge into the contour of the handle at the point of juncture 80 between the grip and shank portions thereof, the juncture 80 providing a smooth arcuate connection between the two portions thereby avoiding undesirable sharp edges within the fiber reinforced handle.

As will be appreciated, the circumscribing grip 78 is attached to the handle after the handle has been mounted within the eye 24 of the hammer head. The handle is mounted by passing the grip and shank portions thereof through the eye 24 and bringing the tapered surfaces on the handle and head into confronting relationship, the head portion of the handle having previously been treated, such as by roller coating, with a suitable auxiliary bonding material. The head portion 42 of the handle smoothly slides into the eye and is held in a fully aligned condition by the ribs 74 and the enlarged free end portion of the handle head. The handle is driven further into the eye under a pressure of about 3 tons to bring the front and

rear walls

32, 34 of the eye into compressive engagement with bottom and top surfaces of the handle head thereby securely locking the handle within the hammer head. Although an epoxy may be used to assist in the secure fastening of the handle within the eye of the hammer head, it will be readily appreciated that the use of such an auxiliary adhesive material is an optional feature of the present invention since the locking taper on the handle head suitable interlocks the handle in the eye of the hammer head.

Thus, it can be seen from the foregoing detailed description that the improved connection of the present invention between the tool handle and the head provides intimate surface contact substantially centered on the axis of percussion for the tool while limiting this contact to a distance approximately equal to twothirds the axial length of the eye of the tool head. it positively provides spaced. relationship between the handle and tool head adjacent the inner end of the eye and prevents sharp edge contact which might otherwise adversely affect tool handles made of fiber reinforced materials. Such a connection not only directly transmits the principal percussive forces acting on the hammer head during use but, in limiting the area of direct force transmission, also permits limited vibratory oscillations. This wedge-free construction not only enables the utilization of materials having greater dimensional stability than the conventional wooden handles but at the same time provides positive interference to disconnection through the tapered self-locking configuration of the handle head, This construction of the present invention additionally permits self-alignment of the handle within the eye of the tool head prior to the formation of a secure locking connection therebetween and enables the use of supplemental bonding materials.

As will be apparent to persons skilled in the art, various modifications and adaptations of the structure above described will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined in the appended claims.

We claim:

1. A tool comprising a tool head having a work performing portion and an elongated handle receiving aperture, and a handle positioned within said aperture and extending outwardly from one end thereof, said handle having a pair of elongated opposed surfaces disposed within the aperture and facing generally toward and away from the work performing portion of the tool head, said opposed surfaces being in secure contact with the tool head along a major portion of their extent to provide a tight fit between the handle and the head and being spaced from the head immediately adjacent the end of the aperture from which the handle extends.

2. The tool of claim 1 wherein the spaces defined by the opposed handle surfaces and the tool head gradually diminish inwardly of the end of the aperture and extend about onequarter the length of said surfaces.

3. The tool of claim 1 wherein said opposed surfaces diverge inwardly of the handle end of the aperture to provide tight locking interference to centrifugal forces and prevent removal of the tool head in the direction of divergence.

4. The tool of claim 1 wherein the handle is provided with shallow side recesses positioned within the tool head for confinably retaining therein a bonding material to assist in the assembled retention of the head on the handle.

5. The tool of claim ll wherein the tool head is provided with an axis passing through the aperture and the work performing portion, the aperture including an eye open at both ends and extending through the tool head at substantially a right angle to said axis, the handle being positioned within the eye along its entire length and terminating at one end thereof, said eye having opposed walls facing generally toward and away from the work performing portion of the tool head in confronting relationship to the opposed handle surfaces, said confronting walls and surfaces being in spaced relationship adjacent the end of the eye from which the handle extends and being in secure interengagement from adjacent the terminal end of the handle through their points of intersection with the axis of the tool head.

6. The tool of claim 1 wherein the handle is provided with handle aligning members for contracting the interior of the handle receiving aperture during initial assembly of the handle within the aperture.

7. The tool of claim 1 wherein the opposed handle surfaces within the aperture define a dovetail terminal portion of the handle preventing outward removal of the tool head from the handle.

8. The tool of claim 1 wherein the handle terminates at one end of the aperture and provides a fiush, continuous, curved surface with the tool head at said aperture.

9. The tool of claim 1 wherein the handle is a fiber reinforced member having elongated nonwoven fibers extending therethrough.

10. A percussive hand tool consisting essentially of a tool head and a fibre reinforced handle connection to the tool head, said tool head having an aperture therein, said fiber reinforced handle being positioned within said aperture in pressure-tight intimate contact with the head to provide the connection therebetween. said tool head having a plane of percussion passing directly through the fiber reinforced handle substantially centered on the area of pressure-tight intimate contact with the head, the handle having elongated nonwoven fibers extending therethrough; the fibers within the handle being predominantly continuous filaments extending substantially the entire length of the handle and into the aperture, said filaments within the aperture being spaced from the tool head at their point of entrance into the aperture to prevent fracture thereof upon use of the tool.

11. The hand tool of claim 10, wherein the pressure-tight intimate contact of the handle with the head is provided by a self-locking taper on the handle and a pair of converging aperture wall portions cooperating with the taper.

'12. The hand tool of claim 10 including side cavities between the handle and the head substantially parallel to the plane of percussion, and an adhesive within the cavities to assist the maintenance of the pressure-tight intimate contact between the fiber reinforced handle and the tool head.

Claims

2. The tool of claim 1 wherein the spaces defined by the opposed handle surfaces and the tool head gradually diminish inwardly of the end of the aperture and extend about one-quarter the length of said surfaces.

5. The tool of claim 1 wherein the tool head is provided with an axis passing through the aperture and the work performing portion, the aperture including an eye open at both ends and extending through the tool head at substantially a right angle to said axis, the handle being positioned within the eye along its entire length and terminating at one end thereof, said eye having opposed walls facing generally toward and away from the work performing portion of the tool head in confronting relationship to the opposed handle surfaces, said confronting walls and surfaces being in spaced relationship adjacent the end of the eye from which the handle extends and being in secure interengagement from adjacent the terminal end of the handle through their points of intersection with the axis of the tool head.

8. The tool of claim 1 wherein the handle terminates at one end of the aperture and provides a flush, continuous, curved surface with the tool head at said aperture.

10. A percussive hand tool consisting essentially of a tool head and a fibre reinforced handle connection to the tool head, said tool head having an aperture therein, said fiber reinforced handle being positioned within said aperture in pressure-tight intimate contact with the head to provide the connection therebetween, said tool head having a plane of percussion passing directly through the fiber reinforced handle substantially centered on the area of pressure-tiGht intimate contact with the head, the handle having elongated nonwoven fibers extending therethrough; the fibers within the handle being predominantly continuous filaments extending substantially the entire length of the handle and into the aperture, said filaments within the aperture being spaced from the tool head at their point of entrance into the aperture to prevent fracture thereof upon use of the tool.

12. The hand tool of claim 10 including side cavities between the handle and the head substantially parallel to the plane of percussion, and an adhesive within the cavities to assist the maintenance of the pressure-tight intimate contact between the fiber reinforced handle and the tool head.