Abstract:
A dead blow hammer has a skeleton including a cylindrical head tube and a cylindrical neck tube fixed to the head tube and projecting laterally therefrom and receiving therein a disk-like plastic spacer and the working end of an elongated plastic handle core, which is adhesively secured in the neck tube. The head tube contains shot and the ends thereof are closed by end caps having cylindrical, longitudinally-slotted flanges press-fitted in the ends of the head tube. The entire skeleton is encapsulated in an overmolded plastic sheath which includes an inner covering and a flexible and resilient grip further overmolded on the inner covering adjacent to the distal end of the handle member.

Description:
BACKGROUND 
     This application relates to impact tools, such as hammers and, in particular, relates to hammers of the type designed to minimize rebound, commonly referred to as “dead blow” hammers. 
     Dead blow hammers are typically provided with a head which is at least partially hollow and contains a rebound-inhibiting material, which may be a flowable material and can be in the form of rigid pellets, such as steel shot, for example. However, many such hammers have handles which extend through the head, thereby inhibiting the flow of material back and forth between impact ends of the head. 
     It is known to provide dead blow hammers formed from a skeleton head and handle framework, partially or fully encapsulated or encased within an outer covering which may be overmolded on the skeleton. However, such prior encapsulated hammers have had complicated or expensive skeleton constructions and/or have been characterized by less than optimal weight distribution between the handle and the head. 
     SUMMARY 
     There is disclosed in this application a hammer construction and method of forming same which avoid the disadvantages of prior constructions and methods while affording additional structural and operating advantages. 
     An important aspect is the provision of a hammer which is of simple and economical construction. 
     Another aspect is the provision of a dead blow hammer with improved non-rebound characteristics and weight distribution. 
     Still another aspect is the provision of a hammer of the type set forth, which minimizes wear between adjacent parts. 
     Still another aspect is the provision of a hammer of the type set forth, which is characterized by a comfortable ergonomic design. 
     Certain ones of these and other aspects may be attained by providing a hammer comprising: an elongated head having a longitudinal axis, a neck tube integral with the head and projecting therefrom and inclined with respect to the longitudinal axis, a handle including a member having a proximal working end received in the neck tube and a distal end, and a spacer disposed in the neck tube between the head and the handle member working end. 
     Other aspects may be attained by providing such a hammer wherein the head is a hollow tube with an open end, closed by an end cap having a cylindrical flange press-fitted in the open end of the head tube. 
     Other aspects may be attained by providing a method of making a hammer comprising: 
     providing a hollow tubular head and a neck tube integral with the head tube and extending therefrom, inserting a working end of a handle core member in the neck tube so that it is spaced from the head, and encapsulating the head and the neck tube and the core member in a plastic sheath. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of facilitating an understanding of the subject matter sought to be protected, there is illustrated in the accompanying drawings an embodiment thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated. 
     FIG. 1 is a side elevational view, in partial section, of a dead blow hammer; 
     FIG. 2 is a view in partial section of the skeleton of the hammer of FIG. 1; 
     FIG. 3 is a reduced, fragmentary view of the left-hand end of the hammer of FIG. 1, illustrating the skeleton in broken line; 
     FIG. 4 is a view in vertical section taken generally along the line  4 — 4  in FIG. 1; 
     FIG. 5 is an enlarged, bottom plan view of an end cap of the skeleton of FIG. 2; and 
     FIG. 6 is a sectional view taken generally along the line  6 — 6  in FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1-4, there is illustrated a dead blow hammer generally designated by the numeral  10 , which includes a head  11  and a handle  12 . The hammer  10  is made up of an internal skeleton framework  15  (FIG. 2) surrounded with an encapsulating sheath  17 . 
     Referring to FIG. 2, the skeleton framework  15  includes an elongated, circularly cylindrical head tube  20  having a central longitudinal axis and two open ends, respectively closed by end caps  21  which are of substantially identical construction. Referring also to FIGS. 5 and 6, each end cap  21  is circular in shape and has a slightly convex outer surface  22  and a substantially flat, planar inner surface  23  having a plurality of equiangularly spaced, generally wedge-shaped recesses  24  formed therein. Depending from the inner surface  23  is a cylindrical flange  25  having formed in its distal end a plurality of circumferentially spaced and axially extending slots  26 , each terminating just short of the inner surface  23 . Projecting radially outwardly from the outer surface of the flange  25  are a plurality of longitudinally extending beads or ribs  27  alternating with the slots  26  so that each bead  27  is disposed substantially midway between an adjacent pair of slots  26 . The outer surface of the flange  25  is beveled adjacent to its distal end, as at  28 . The flange  25  is coaxial with the cap  21  and has an outer diameter less than that of the cap  21 , so that the intervening portion of the inner surface  23  defines an annular shoulder  29 . 
     In assembly, each end cap flange  25  is dimensioned to be press fitted in an open end of the head tube  20 , the slots  26  cooperating to define a plurality of spaced fingers which have a slight flexibility to facilitate insertion in the head tube  20 , this insertion further being facilitated by the beveling at  28 . The beads  27  ensure a snug fit. The cap  21  is so dimensioned that, when fully inserted in place, the annular shoulder  29  will abut the adjacent end of the head tube  20  (see FIG.  2 ), the outer diameter of the cap  21  being substantially the same as that of the head tube  20 . 
     Fixedly secured to the outer surface of the head tube  20 , approximately centrally along its length, and projecting radially outwardly therefrom is a cylindrical neck tube  30 , which may be fixedly secured to the head tube  20  by a suitable weldment  31 . Seated in the neck tube  30  against the outer surface of the head tube  20  is a circular, disk-shaped spacer  32 . The handle portion of the skeleton framework  15  includes a member in the form of an elongated handle core  33  which, in transverse cross section, is substantially in the shape of a square with angled or beveled corners (see FIG.  4 ). Formed in opposite sides of the core  33  and extending longitudinally thereof along the entire length thereof are channel-shaped grooves  34 . The core  33  is dimensioned to be freely received in the neck tube  30  and seated against the spacer  32 , being fixedly secured in place by suitable means, such as by a suitable adhesive  35  which fills the voids in the neck tube  30  (see FIG.  2 ). 
     In assembly, before or after the handle core  33  is fixed in the neck tube  30  against the spacer  32 , as described above, one end cap  21  is fitted in place to close one end of the head tube  20 . Then the head tube  20  is partially filled with a flowable, rebound-inhibiting material, which may be in the form of rigid pellets, such as steel shot  37 . Then the other end cap  21  is secured in place to completely close the head tube  20  and complete the skeleton framework  15  of the hammer  10 . 
     Then, the encapsulating sheath  17  is applied by overmolding the skeleton framework  15  with suitable moldable materials, such as suitable plastics, completely encapsulating the entire skeleton framework  15 , as best seen in FIG.  1 . The finished handle cross section may have a generally oblong or oval shape, as illustrated in FIG.  4 . The encapsulating sheath  17  includes an inner covering  38  of a first material, which completely covers the skeleton framework  15  and defines, in a grip portion adjacent to the distal end of the handle  12 , recesses  36  along the upper and lower sides of the handle  12 . The recesses  36  are filled, in a further overmolding process, with an outer layer of material forming outer grips  39 . 
     In a constructional model of the hammer, the head tube  20 , the end caps  21  and the neck tube  30  may be formed of suitable metals, such as suitable steels for the head tube and the neck tube and suitable zinc alloys for the end caps. The handle core  33  may be formed of a relatively lightweight, strong, non-metallic material, such as fiberglass. The spacer  32  and the inner covering  38  and the outer grips  39  may be formed of suitable moldable plastic materials, such as suitable urethanes. The outer layer forming the outer grips  39  may be of a softer, flexible and resilient material than the inner covering  38  to form a more comfortable grip. The inner covering  38  and outer grips  39  may be applied by injection molding. 
     The head tube  20  is designed with an appropriate wall thickness and diameter to produce the desired overall hammer weight. The zinc alloy of the end caps  21  is designed to be resistant to impact forces. The convex outer surface  22  of the end cap  21  is designed to be resistant to the injection molding pressures to which the head is subjected in applying the encapsulating sheath  17 . 
     As was explained above, the end cap slots  26  stop short of the inner surface  23 , so as to provide additional sealing within the head tube  20 . The flexibility of the end cap flange  25  afforded by the slots  26  facilitates press fitting, permitting proper assembly irrespective of tolerance variations in the inner diameter of the head tube  20 . The grooves  34  along the handle core  33  facilitate adequate positioning of the skeleton framework  15  in the injection molding dies, as well as serving to prevent the encapsulating sheath  17  from twisting or slipping around the handle core  33  during strenuous use. The spacer  32  serves to provide vibration absorption, to eliminate impact vibration or shock which would otherwise be transmitted down the handle core  33  upon hammer strike and then into the user&#39;s hand. The spacer  32  also serves to minimize unwanted wear which might be occasioned by direct engagement of the fiberglass handle core  33  with the steel head tube  20 . 
     The composite handle  12 , formed of relatively lightweight materials, together with the metal head tube  20 , facilitates an improved weight distribution in the hammer  10  without reducing the overall weight of the hammer. More specifically, weight has been transferred from the handle to the head and, as a result, the hammer&#39;s center of percussion is moved further forward, permitting the hammer  10  to deliver approximately 30% more force during use than prior designs. By attaching the fiberglass handle core  33  to the steel head tube  20  by means of an externally welded neck tube  30 , there is no extension of the handle core  33  through the head tube  20 , resulting in an unobstructed flow of steel shot within the head tube. The use of a skeleton framework  15  which is partially fiberglass and partially steel provides an improved result over prior all-fiberglass skeletons, by permitting the hammer  10  to be approximately 30% smaller than hammers with all-fiberglass skeletons of the same weight. As a result, the hammer  10  can be used in tighter, more restrictive areas. 
     From the foregoing, it can be seen that there has been provided an improved dead blow hammer which is of simple and economical construction, improved weight distribution and force-delivering capacity, and improved vibration resistance and ergonomic design. 
     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While a particular embodiment has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.