US3506520A - Method of making and assembling a percussion head and handle joint - Google Patents

Description

April 1970 J. c. No RcRoss ,506,520

METHOD OF MAKING AND ASSEMBLING A PERCUS HEAD HANDLE 0 NT Original ed Nov. 1965 INVENTOR JOHN c. NOBCROSS ATT'Y United States Patent Int. Cl. B29c 27/16 US. Cl. 156-293 2 Claims ABSTRACT OF THE DISCLOSURE A method of permanently affixing the metal head of an impact tool to a non-metallic handle wherein a smoothwalled socket is formed in the head and an annular external groove is formed in the handle, the handle is inserted endwise in the groove so that a quantity of epoxy resin which is previously placed in the socket flows into the groove and, when hardened, establishes a generally D- shaped locking ring. One or more longitudinal grooves extend inwardly from the end of the handle and communicate with the groove so as to enhance the flow of the resin into the groove when the insertion is made.

This application is a division of my co-pending United States patent application Ser. No. 509,811, filed on Nov. 26, 1965, now abandoned.

The present invention relates to a novel method of making and assembling a percussion head and handle joint. Joints which are constructed and assembled according to the present invention may be employed in connection with a wide variety of percussion or striking tools such, for example, as mallets, claw and other hammers axes, sledges and the like, but for convenience of illustration and description herein, the improved joint for exemplary purposes only, is disclosed in connection with a simple form of mallet for use by carpenters and other artisans.

The invention is specifically concerned with a method of making and assembling a percussion head and handle joint of the type wherein the head is provided with a rela tively deep eye or socket into which one end of an elongated Wooden handle is frictionally driven or otherwise forced in endwise fashion. Such a joint is an extremely common one and it has long been the practice to insure the joint against looseness or separation of the head and handle by coating either the wall of the socket or the associated end region of the handle with a suitable glue or other adhesive. The coating operation is sometimes performed by dipping or with the aid of a brush or other applicator but it is also accomplished by pouring a small amount of the adhesive into the bottom portion of the socket and then relying upon the displacing action of the associated end of the handle as it is forced into the socket to force the adhesive around the sides of said associated handle and until the annulus that is established between the socket and the handle is filled with the adhesive. With the development of epoxy-type resins, it became instantly apparent that because of their strong bonding action, such resins would be admirably well adapted or suited for use as bonding agents in connection with percussion head and handle joints and they have been variously used for this purpose for quite some time.

Heretofore, regardless of the method that is employed in the application of an adhesive to the mating surfaces of a percussion head socket and its associated handle, difficulty has been encountered due to the hermetic seal which is automatically established when the adjacent end of the handle is initially introduced into the socket of the head. This is true regardless of whether such mating surice faces be simply coated with the adhesive or whether the adhesive be poured into the socket and the dry associated end of the handle then forced into the socket. If the mating surfaces of the head and handle are initially coated with theadhesive, the presence of the adhesive establishes suchlan air tight seal around the wall of the socket that air may not escape from the socket. The thus entrapped air in the bottom portion of the socket not only offers resistance to full inward motion of the associated end of the handle, but due to the compression thereof there is developed a high internal pressure which tends to force the handle back and out of the socket after inward pressure thereon has been relieved. Thus, during the drying or hardening time, the handle will creep outwardly to a position of looseness before the adhesive has had time to set or harden. If clamps are employed to hold the associated end of the handle in its innermost position within the socket during setting of the adhesive, the outward pressure of the entrapped air in the bottom portion of the socket is frequently stronger than is the adhesive bond so that, after the mallet or other tool has been put to use, the handle will spring out of the socket. When the adhesive is poured into the socket as previously described, some air may escape but the high viscosity of the adhesive, particularly in the case of an epoxy resin, will prevent the adhesive from flowing around the adjacent end of the handle regardless of the amount of applied inward pressure on the handle, and the net result will be a joint wherein the only existing bond is between the circular or other end face of the associated handle end and the correspondingly shaped bottom wall of the socket.

The present invention is designed to overcome the above-noted limitations that are attendant upon a conventional or standard percussion head and handle joint and, toward this end, there is contemplated the provision of a novel method of making and assembling a joint wherein a wooden handle may be installed in the eye or socket of a percussion head with full assurance (1) that the adhesive will flow into, and establish its bonding action within a major volume of, the annulus between the surrounding wall of the socket and the adjacent end of the handle, and (2) that no air will become entrapped within the socket under pressure, either to resist initial handle insertion or to establish a residual air pocket tending subsequently to force the handle outwardly from the socket. The invention further contemplates the artificial creation of dimensionally thick localized regions within the annulus which is established between the wall of the socket and the adjacent end of the handle, these regions becoming filled with the adhesive according to the present invention as said adjacent end of the handle is forced into the socket. The adhesive which is preferably employed in connection with the improved joint is in the form of an epoxy resin which is capable of polymerization and hardens uniformly and simultaneously throughout its entire mass. Thus, upon polymerization of the resin, distance-bonds across these dimensionally thick regions are formed and, because the hardened resin is considerably harder than is the wood of which the handle is formed and is more shatterproof than an ordinary adhesive, such as glue, there is provided an extremely eifective joint that will withstand extremely rough use of the particular percussion or striking tool to which the present joint is applied.

The provision of a method of making and assembling a percussion head and handle joint such as has briefly been outlined above being among the principal objects of the invention, numerous other objects and advantages will readily suggest themselves as the following description ensues.

In the following single sheet of drawings forming a part of this specification, one exemplary form of the invention is shown.

In these drawings:

FIG. 1 is a fragmentary sectional view taken substantially centrally and longitudinally through a percussion or striking tool (mallet) embodying the novel joint resulting from the particular making and assembly method constituting the present invention;

FIG. 2 is a sectional view taken on the line 22 of FIG. 1;

FIG. 3 is an enlarged sectional view taken on the line 33 of FIG. 1;

FIG. 4 is an enlarged sectional view taken on the line 4-4 of FIG. 1; and

FIGS. 5, 6 and 7 are enlarged sectional views, schematic in their representation, illustrating progressive method steps which are employed in practicing the method of the present invention.

Referring now to the drawings in detail and in particular to FIGS. 1 to 4, inclusive, a percussion or striking tool in the form of a mallet 10 is provided with a metallic generally cylindrical impact head 12 and a wooden handle 14. The head 12 embodies removable striking elements 13 at its ends and is provided on its medial portion with a hollow laterally extending boss or holding portion 16. The latter is oval shaped in cross section and forms or defines a socket 18 of appreciable depth, the socket being designed for telescopic reception of the adjacent or proximate end of the handle 14.

Except for the treatment of the proximate end of the handle 14, the handle is of conventional construction and may be in the form of an ordinary hickory handle which is appropriately contoured or shaped for hand use. Adjacent to, but spaced a small distance from, the end face 20 of the proximate end of the handle, there is provided a continuous groove 22 which is preferably of shallow arcuate construction and of appreciable width. A plurality of longitudinally extending narrow grooves 24 communicate with the continuous groove 22 at equidistantly spaced regions therearound and open endwise onto the end face of the handle. Preferably there are four longitudinally extending grooves as shown in the drawings.

The proximate end region of the handle 14 is driven into the socket 18 with a fairly tight fit and the various grooves 22 and 24 are substantially completely filled with an epoxy resin 26. Additionally, residual webs of the epoxy resin arising from conditions that will be set forth presently, may be interposed between such surface regions of the handle 14 and the wall of the socket 18 as directly and closely oppose each other in face-to-face relationship.

From the above description, it will be appreciated that an extremely effective joint between the head 12 and the handle 14 is attained. It is well known that in most instance, a thick layer of ordinary adhesives such as glue, filler compounds, adhesive substances containing ketones and vinyl chloride and the like, are less effective as a bonding agent than is a thin layer of the substance. While the adhesive qualities of these substances may be satisfactory, the fracture characteristics are high and, although such adhesive substance may adhere to both surfaces which are undergoing joining, they are subject to internal fracture when applied in thick layers. Such is not the case with the epoxy resins which upon hardening present a solid mass of extreme hardness throughout and are not subject to fracture under ordinary tensile and compressional forces. For these reasons, the thickness-bond which occurs completely around the handle 14 in the region of the groove 22 in no way represents a region of relative weakness. Rather, it represents a region of strength in excess of the strength that otherwise would be present were the annulus not provided.

In assembling the impact or striking head 12 and the handle 14 according to the present method, the head 12 may be positioned in a suitable assembly jig with the socket 18 extending vertically and opening upwardly as shown in FIG. 5. An appreciable but measured quantity of the raw epoxy resin 26, suitably mixed with a hardening agent, is poured into the socket and seeks its normal level as indicated in the drawing. Thereafter, the proximate end of the handle 14 is inserted endwise and axially into the socket 18 and is then forced downwardly under high pressure as indicated in FIG. 6. In this view, the handle 14 is shown in elevation while the impact head 12 is shown in section and'it may thus be seen that as the end face 20 of the proximate end of the handle engages the pool or mass of epoxy resin that is contained within the socket 18, such resin will be forced upwardly through the various longitudinal grooves 24 and will enter the continuous groove 22. At the same time, depending upon the tightness of the fit between the proximate end of the handle and the wall of the socket, some of the epoxy resin may be forced upwardly into the thin cylindrical annulus which exists between the directed opposed surfaces of the handle and the wall of the socket. Such upward progression of the rein may not continue for long due to the relatively high coefiicient of viscosity of the resin. However, even a small amount of such upward progression will appreciably strengthen the bond between the socket and the handle. The problem of entrapped air within the socket does not arise during progressive entry of the proximate end of the handle into the socket inasmuch as such air as may be present initially passes outwardly through the grooves 24, enters the continuous groove 22, and then is dissipated by outward fiow around the body of the handle which, at the time, is not yet fully in coextensive contact with the wall of the socket.

In FIG. 7, the handle 14 is shown as having been fully introduced into the socket 18 under pressure. The epoxy resin, at this time, has substantially completely filled all the grooves 24 and 22 and some of the resin has been squeezed upwardly in the thin annulus which exists above the level of the groove 22 to establish a ring-like area of bond at such level.

As an alternative method of assembling the joint between the handle 14 and the impact head 12, the proximate end region of the handle may be either dipped in a pool of the resin or some of the resin may be applied to this region of the handle by brushing or otherwise spreading it thereon prior to introduction of the proximate end of the handle into the socket 18. The resultant bond will be substantially the same as that previously described except for the fact that, in the final joint, all closely opposed areas of the handle and the wall of the socket will have interposed therebetween a quantity of resin.

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. Furthermore, variations in the method steps that are employed may be resorted to within the scope of the invention.

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

1. The method of anchoring the proximate end region of an elongated handle in a relatively deep smooth-walled socket in the metal head of a striking tool, the cross sectional configuration of said end region conforming generally in shape and dimension to the cross sectional shape and dimension of the socket, said method comprising: providing around said end region an outwardly opening continuous groove of a width appreciably less than the depth of the socket and spaced from the extreme distal end of the handle a distance less than the depth of the socket, providing a second groove which communicates with said continuous groove and opens endwise onto the proximate end face of the handle, positioning said head so that said socket therein opens generally upwardly, introducing into said socket a quantity of flowable and epoxy adhesive in order to provide a pool of the adhesive therein, introducing said proximate end region of the handle endwise into the socket and forcing the same downwardly therein under pressure so as to immerse the 5 6 extreme proximate end region of the handle within the 2,263,198 11/1941 Valiton 287-2092 adhesive and thus cause the latter to flow upwardly 2,663,662 12/1953 Graf et a1. 156293 X through the second mentioned groove and into the con- 2, 73 353 5 1954 Reader. tinuous groove while air is expelled from the continuous 2 5 33 9 195g Curry et 1 3Q6 32 groove upwardly around the outer side of the handle, and 3 090 653 5/1963 Stump 306 32 X rausing polymerization of the adhesive. 5

2. The method set forth in claim 1 and wherein said REUBEN EPSTEIN, Primary Examiner second groove is linearly straight and extends longitudinally of the handle. US. Cl. X.R.

References Cited 10 156330; 30622 UNITED STATES PATENTS 1,516,975 11/1924 McArthur .o 306-33};

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