Patent Publication Number: US-6216566-B1

Title: Insulating composite breaker bar

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to hand tools of the type which are relatively non-conducting electrically so that they can be safely used in applications where they may come into contact with sources of electrical power. 
     Various types of electrically insulated hand tools have been available for many years. Such tools typically include a standard metal shaft which, in addition to being connected to a handle which is formed of electrically insulating material, such as wood or plastic, is also coated or covered with an insulating material. Such insulated tools work acceptably well as long as the insulating covering is intact and in good condition. But, if the insulation becomes damaged, such a tool may be dangerous if it comes into contact with a source of electrical power, the danger being the risk of electrical shock to the user or inadvertent shorting of electrical circuits with which the shaft may come into contact. Therefore, such insulated tools are not recommended for use on live electrical wiring, contacts, or the like. 
     Certain types of tools with elongated shanks or shafts are formed of electrically insulating material. One such tool is disclosed, for example, in U.S. Pat. No. 5,259,277. But such prior tools do not have work-engaging portions which are designed to be movable in use relative to the shaft. 
     SUMMARY OF THE INVENTION 
     It is a general object of the invention to provide an improved composite hand tool which avoids the disadvantages of prior tools while affording additional structural and operating advantages. 
     An important feature of the invention is the provision of an electrically insulating hand tool which accommodates movement in use of a metal work-engaging portion, while minimizing exposure of electrically conducting portions. 
     Another feature of the invention is the provision of a hand tool of the type set forth, which is of relatively simple and economical construction. 
     Another feature of the invention is the provision of an electrically insulating breaker bar with a swivel square drive spinner. 
     In connection with the foregoing features, another feature of the invention is the provision of a hand tool of the type set forth, which affords the strength of a steel tool, while having significantly lower weight. 
     Certain ones of these and other features of the invention may be attained by providing a composite electrically insulating hand tool comprising: an elongated non-metallic shaft having a longitudinal axis and first and second ends, a non-metallic handle fixed to the first end of the shaft, an axial non-metallic receptacle at the second end of the shaft, and a plural-position, work-engaging mechanism fixedly received in the receptacle and projecting therefrom, the receptacle having a lateral opening therein to accommodate movement of the work-engaging mechanism to and from different use positions. 
     Other features of the invention may be attained by providing a hand tool of the type set forth, which includes a non-metallic sleeve receiving in one end thereof the second end of the shaft and receiving in the other end thereof the work-engaging mechanism, the lateral opening being formed in the sleeve. 
     The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation, and many of its advantages should be readily understood and appreciated. 
     FIG. 1 is a side elevational view of a composite breaker bar constructed in accordance with and embodying the features of the present invention; 
     FIG. 2 is an enlarged, fragmentary, perspective, exploded view of the working end of the breaker bar of FIG. 1; 
     FIG. 3 is an enlarged, fragmentary, sectional view taken generally along the line  3 — 3  in FIG.  1  and illustrating in broken line alternative working positions of the tool; 
     FIG. 4 is a sectional view taken generally along the line  4 — 4  in FIG. 3; and 
     FIG. 5 is an enlarged view in vertical section taken generally along the line  5 — 5  in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1-5, there is illustrated a breaker bar, generally designated by the numeral  10 , constructed in accordance with the present invention. The breaker bar  10  has an elongated composite shaft  11  which is substantially cylindrical in shape, having a reduced-diameter end  12  and a working end  13 . The reduced-diameter end  12  is received in a complementary axial bore in one end of an elongated handle  14 . The working end  13  of the shaft  11  is coaxially received in one end of an elongated, hollow, tubular sleeve  15  formed of an electrically insulating material and having formed axially in the other or distal end thereof a slot  16 , which extends diametrically thereacross. 
     The shaft  11  is preferably formed of a pultruded glass/polyester composite material. The handle  14  may be formed of a suitable electrically insulating plastic material. The reduced end  12  of the shaft  11  may be fixedly secured in the handle  14  and the working end  13  of the shaft  11  may be fixedly secured in the sleeve  15  by a suitable means, such as with an adhesive  17  (see FIGS.  3 - 5 ). The sleeve  15  is formed of a composite, electrically insulating material, preferably tubing made of alternating layers of braided (±45°) and longitudinally extending glass fibers in an epoxy resin matrix. 
     The breaker bar  10  also includes a work-engaging mechanism in the form of a swivel yoke  20 , which has a substantially cylindrical barrel  21  provided with a chamfer  22  at one end thereof and having the cylindrical external surface thereof knurled, as at  23 . The barrel  21  is dimensioned to be press-fitted in the slotted distal end of the sleeve  15  for fixedly securing the yoke  20  to the sleeve  15 . The barrel  21  has a wide diametral slot formed axially therein at the forward end thereof, thereby forming a pair of clevis arms  24  and  25 , each having a part-cylindrical outer surface  26 . Formed through the clevis arms  24  and  25  diametrically of the barrel  21  is a bore  27  (FIG. 4) counterbored at one end thereof, as at  28  (FIG.  4 ). Preferably, the distal ends of the clevis arms  24  and  25  are rounded off along an arc coaxial with the bore  27 . 
     The swivel yoke  20  also includes a square drive member  30  having a generally cylindrical hub  31  receivable between the clevis arms  24  and  25 , the hub  31  having an axial bore  32  therethrough. Integral with the hub  31  and projecting radially therefrom is a square drive lug  33 , having a detent ball  34  projecting from one side thereof in a known manner (FIGS.  3  and  4 ). The hub  31  is receivable in use between the clevis arms  24  and  25 , with the bore  32  disposed in coaxial alignment with the bore  27  through the clevis arms  24  and  25  for receiving a pivot screw  35 , having an enlarged slot head  36  receivable in the counterbore  28 , as can best be seen in FIGS. 3 and 4. In this regard, the bore  27  may be internally threaded in the clevis arm  24  for threaded engagement with the screw  35 . Formed in one side surface of the hub  31  coaxially around the bore  32  is an annular recess  37  receiving therein a friction O-ring  38  (see FIG.  4 ). 
     In use, the square drive member  30  is dimensioned for pivotal movement relative to the clevis arms  24  and  25  about the axis of the pivot screw  35  among a plurality of use positions, illustrated in FIG.  3 . The O-ring  38  serves to frictionally inhibit pivotal movement of the square drive member  30  among its several positions, so as to effectively retain the square drive member  30  in a selected use position against accidental movement from that position, the frictional force being low enough to accommodate manual movement of the square drive member to a selected different use position. In the illustrated embodiment the square drive member  30  has three use positions, including an axially extending position illustrated in solid line in FIG.  3  and two laterally extending positions, illustrated in broken line in FIG. 3, respectively projecting from opposite sides of the sleeve  15  substantially perpendicular to the longitudinal axis of the shaft  11 . 
     It will be appreciated that the slot  16  is dimensioned to permit pivoting or swiveling movement of the square drive member  30  among its several use positions while, at the same time, protecting the clevis arms  24  and  25  from contact with electrically live surfaces in the vicinity of use. Thus, it will be appreciated that the only electrically conducting part of the breaker bar  10  which is exposed in use is the work-engaging portion of the square drive member  30 . 
     From the foregoing, it can be seen that the electrically insulating sleeve  15  provides a secure coupling between the working end of the shaft  11  and the swivel yoke  20 , while accommodating swiveling movement of the yoke  20  and minimizing exposure of electrically conducting portions thereof. 
     While the swivel yoke  20  is preferably press-fitted in the sleeve  15 , it will be appreciated that it could be fixedly secured by other means, such as a suitable adhesive. The insulating composite breaker bar  10  when used in conjunction with an associated socket tool, provides a means to apply high torque energies to associated fasteners in the vicinity of live electrical components, while minimizing any electrical hazard to the user of the components. Prototype constructional models of the breaker bar  10  have demonstrated both mechanical and dielectric strength values which exceed the applicable standards for such a tool. In particular, the breaker bar  10  has a mechanical strength comparable to that of a similarly-sized steel breaker bar. 
     From the foregoing, it can be seen that there has been provided an improved breaker bar which is electrically insulating, having no electrically conductive parts except for a work-engaging portion, and which accommodates movement of that work-engaging portion among different use orientations without adversely affecting the electrically insulating characteristics of the tool. 
     While particular embodiments of the present invention have 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 invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.