Patent Publication Number: US-6655240-B1

Title: Insulating driver with injection molded shank and fluted working tip

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of U.S. Ser. No. 08/867,183, tiled Jun. 2, 1997 now abandoned and entitled “Insulating Driver with Injection Molded Shank.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to hand tools of the type which are relatively non-conducting electrically, so that they can safely be used in applications where they may come into contact with sources of electrical power. 
     2. Description of the Prior Art 
     Various types of electrically insulating hand tools have been available for many years. Such tools typically have a standard metal shaft/blade 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 shank may come in 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 of plastic material have been provided heretofore, but they have not been hand tools provided with a handle at one end. 
     U.S. Pat. No. 5,259,277, discloses an electrically insulating hand tool, with a shank formed of composite material and fixedly secured, as by a suitable adhesive, in an axial bore in one end of an associated handle, which is also formed of an electrically insulating material. This screwdriver works well in terms of electrical insulation, but the adhesive attachment of the shank to the handle has disadvantages, in terms of assembly steps and torque strength of the resultant product. Furthermore, the composite material of the tool shank, while affording excellent electrical insulation characteristics, must be produced through preform resin impregnation, which has certain disadvantages as compared to other types of molding. 
     SUMMARY OF THE INVENTION 
     It is a general object of the invention to provide an electrically insulating hand tool which avoids the disadvantages of prior hand tools, while affording additional structural and operating advantages. 
     An important feature of the invention is the provision of an electrically insulating hand tool which is of simple and economical construction, avoiding the use of adhesives. 
     Another feature of the invention is the provision of an electrically insulating hand tool of the type set forth, which provides improved torque strength. 
     Yet another feature of the invention is the provision of a hand tool of the type set forth, which can be formed by injection molding, while offering improved electrical insulation characteristics. 
     These and other features of the invention are attained by providing an insulating hand tool comprising: an insulating hand tool comprising: an elongated torque-transmitting shank formed of high-strength, injection-molded, electrically insulating material and having a handle end and a working end, a handle formed of electrically insulating material and carried by the handle end of the shank, and a working tip having a mounting portion fixed in the working end of the shank and a work-engaging portion projecting from the working end of the shank, the mounting portion including an anchor portion having angularly spaced flutes substantially filled with material of the shank. 
    
    
     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 perspective view of a hand tool in accordance with a first embodiment of the present invention, having an insert-molded socket for removably receiving a working tip; 
     FIG. 2 is a side elevational view of the hand tool of FIG. 1, in partial section and with a portion of the shank broken away; 
     FIG. 3 is a view similar to FIG. 2 of a second embodiment of the present invention; 
     FIG. 4 is a view similar to FIG. 2 of yet another embodiment of the present invention; 
     FIG. 5 is an enlarged sectional view taken generally along the line  5 — 5  in FIG. 4; 
     FIG. 6 is a vertical sectional view through an injection mold for forming the screwdriver of the present invention; 
     FIG. 7 is a bottom plan view of the top half of the mold of FIG. 6, indicating at  6 — 6  the plane at which the view of FIG. 6 is taken; 
     FIG. 8 is a view similar to FIG. 5, in partial section, of another embodiment of the invention; 
     FIG. 9 is an enlarged sectional view of the socket insert molded in the shank of FIG. 8; 
     FIG. 10 is an enlarged, fragmentary, sectional view of another embodiment of the invention; 
     FIG. 11 is a view similar to FIG. 10 of still another embodiment of the invention; 
     FIG. 12 is a side elevational view, in partial section of a shank and working tip in accordance with another embodiment of the invention; 
     FIG. 13 is an enlarged, side elevational view of the working tip of FIG. 12; 
     FIG. 14 is a further enlarged, fragmentary side elevational view of the left-hand end of the working tip of FIG. 13; 
     FIG. 15 is an end elevational view of the left-hand end of the working tip of FIG. 14; and 
     FIG. 16 is an enlarged cross-sectional view taken generally along the line  16 — 16  in FIG.  12 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, there is illustrated a hand tool in the nature of a screwdriver, generally designated by the numeral  10 , constructed in accordance with the present invention. The screwdriver  10  is of unitary, one-piece construction, and includes an elongated handle  11  having a forward end  12  with sloping shoulders  13  which join the handle end  14  of an elongated cylindrical shank  15 . While the shank  15  is illustrated as being circularly cylindrical, it will be appreciated that it could be tapered from the handle end  14  to a reduced-diameter working end  16 . A generally cylindrical tip holder or socket  20  is embedded in the working end  16  of the shank  15  coaxially therewith, the tip holder  20  defining an axial receptacle  21  therein which opens at the distal end of the shank  15 . A permanent magnet  22  may be seated in the receptacle  21  for removably retaining therein an associated working tip  25 , which may be in the nature of a tool bit, such as a flat blade screwdriver bit. Preferably, the receptacle  21  is non-circular in transverse cross section and is shaped for mateably receiving a similarly shaped bit shank to inhibit relative rotation of the parts. A hexagonal shape is commonly used. Also, it will be appreciated that the outer surface of the tip holder  20  may be non-circular in transverse cross section to inhibit rotation of the tip holder  20  relative to the shank  15 . 
     It is a significant aspect of the present invention that the screwdriver  10  is injection molded of a high-strength electrically insulating material. Suitable materials which have the requisite strength and electrical insulation properties, as well as being injection-moldable, include nylon, PVC, glass-reinforced nylon and glass-reinforced PVC. In a preferred constructional model of the invention, the screwdriver  10  is formed of glass-reinforced nylon material, which has been found to provide improved insulating properties. In particular, the glass-reinforced nylon material meets the IEC900 standard for insulating hand tools of 1,000 volts. The tip holder  20  may be formed of a suitable metal, and the magnet  22  may be a neodymium magnet. The tip  25  is formed of any suitable magnetizable metal material. 
     Referring to FIG. 3, there is illustrated another screwdriver  30  which is not of unitary, one-piece construction. The screwdriver  30  has an elongated handle  31  which is similar to the handle  11 , described above, and terminates in a flat, generally circular forward end  32 . An axial bore  33  is formed in the forward end  32  and receives therein the handle end  34  of an elongated shank  35 . The shank  35  may be provided with a pair of diametrically opposed wings  36  extending laterally outwardly therefrom, the handle end  34  being adapted to be press-fitted in the bore  33 , with the wings  36  embedding in the handle material for inhibiting rotation of the shank  35  relative to the handle  31 . The shank  35  has a working end  37  which has a tip, such as the tip  25 , insert molded directly therein coaxially therewith. 
     The shank  35  is substantially the same as the shank  15  described above, except that it is not unitary with the handle. More specifically, the shank  35  is injection molded of a suitable material, preferably glass-reinforced nylon, with the tip being insert molded in the shank  25  during the molding process. The handle  31  is independently formed of a suitable electrically insulating material, which may be the same as or different from the material of the shank  35 . While the shank  35  is shown with a working tip  25  insert molded directly therein, it will be appreciated that the working end  37  of the shank  35  could have insert molded therein a tip holder or socket  20 , as in the screwdriver  10 , for removably receiving an associated tip. 
     Referring to FIGS. 4 and 5, there is illustrated a screwdriver  40 , which is similar to the screwdriver  30 , except that the handle  41  has an axial bore  43  in the forward end  42  thereof which has an axial extent somewhat greater than that of the bore  33 . The screwdriver  40  has a shank  45  which is similar to the shank  35 , having an elongated handle end  44  adapted to be press-fitted in the bore  43  of the handle  41 . Preferably, the handle end  44  has equiangularly spaced apart therearound a plurality of radially outwardly extending ribs or splines  46 , which dig into the material of the handle  41  and inhibit rotation of the shank  45  relative to the handle  41 . The shank  45  has a working end  47  with an axial receptacle  48  formed therein, which may be circularly cylindrical in shape and is adapted for am receiving an associated working tip  50 . More particularly, the tip  50  may be provided with knurling  51  to afford a press-fitted engagement in the receptacle  48 , which will inhibit relative rotational movement of the parts. The tip  50  is illustrated as having a screw starting end  52 , but it will be appreciated that other types of working tips or bits could be utilized. Preferably, the shank  45  is formed by the same process and of the same material as the shank  35 , described above. 
     While each of the screwdrivers  10 ,  30  and  40  has been illustrated with a particular type of bit or tip-mounting arrangement, it will be appreciated that any one of these screwdrivers could be provided with either a bit-receiving socket insert molded in the shank, a bit directly insert molded in the shank or a bit press-fitted in an axial bore in the shank. Also, it will be appreciated that the shanks  35  and  45  could be insert molded in the handles  31  and  41 , respectively. 
     Referring now to FIGS. 6 and 7, there is illustrated an injection mold  60  of the type which may be used for forming the screwdriver  10  or the shanks  35  and  45  of the screwdrivers  30  and  40 . The injection mold  60  includes a lower half  61  and an upper half  62  which, in use, are joined together at a parting plane  63 . Formed in the mold  60  are cavities  65 ,  65 A and  65 B, each of which is formed partly in the lower half  61  and partly in the upper half  62 , so that, when the halves are joined, as illustrated in FIG. 6, the cavities  65  will be longitudinally bisected by the parting plane  63 . In the illustrated embodiment, the mold  60  has three cavities, the cavities  65  and  65 A being of the type for forming the shank  35  or  45 , and the cavity  65 B being of the type for forming a unitary, one-piece screwdriver  10 , the shanks being shown slightly tapered in this case. It will be appreciated that any number of cavities could be provided, and that the cavities  65 - 65 B are shown only for purposes of illustration. Preferably, there is mounted in the mold  60  adjacent to the distal ends of the cavities  65 - 65 B, insert holders  66  which are adapted to retain inserts  67  in predetermined positions coaxially in the associated cavities  65 - 65 B. It will be appreciated that the insert  67  may be in the form of a tip holder or socket  20 , a tip or bit  25 , or a pin designed to be removed after molding to form a receptacle  48 . 
     In operation, after the insert holders  66  are mounted in position for holding the inserts  67  in the appropriate location, the mold  60  is closed and the plastic material is injected in liquid form through an injection gate  64 , preferably at one end of the cavities  65 - 65 B. The plastic material, preferably glass-reinforced nylon, is injected under suitable pressure until it completely fills the cavities  65 - 65 B, flowing around the inserts  67 . The flow of plastic material then ceases, the mold is allowed to cool for a predetermined period of time and the mold is then opened to remove the molded parts with the aid of ejector pins  68 , all in a known manner. 
     Referring now to FIGS. 8 and 9, there is illustrated another embodiment of the invention in the form of a nut driver  40 A, which is substantially the same as the screwdriver  40  of FIG. 4, except for the working end of the shank, which is designated  45 A. A socket member  70  is disposed in the working end of the shank  45 A, preferably by insert molding. The socket member  70  is an elongated, generally tubular member, having an enlarged-diameter end  71  and a reduced-diameter end  72 , joined by a sloping shoulder  73 . A chamfer  74  may be formed on the reduced-diameter end  72 . The socket member  70  has an axial bore  75  extending therethrough and is provided in the large-diameter end  71  with an enlarged hexagonal receptacle  76  which communicates with the bore  75  and is shaped for driving an associated nut or similar fastener. Preferably, the outer surface of the ends  71  and  72  are knurled, as at  77 , to inhibit rotation within the shank  45 A. 
     The socket member  70  is disposed in the shank  45 A with the end face of the large-diameter end  71  substantially flush with the distal end of the working end of the shank  45 A, as illustrated in FIG.  8 . Preferably, an axial bore  78  is formed in the shank  45 A rearwardly of the socket member  70  and communicating with the bore  75  to provide clearance for associated screws, bolts, studs or the like with which a driven nut may be associated. While, in the illustrated embodiment, the socket member  70  is insert molded in the shank  45 A, as by use of an injection mold like that shown in FIGS. 6 and 7, it will be appreciated that it could be press fitted in a bore or receptacle in the working end of the shank  45 A. 
     It is significant that the tapered geometry of the socket member  70  provides for increased thickness of shank material in the region  79  surrounding the reduced-diameter end  72  of the socket member  70 . It has been found that this configuration serves to limit bending fractures to the region of the large-diameter end  71 , wherein the fractures are limited to the insert member itself and are retained by the surrounding shank material so as to prevent projectiles from occurring. Absent the reduced-diameter end  72 , bending fractures would tend to occur in the plastic material of the shank at the inner end of the socket member, which could result in relatively large and dangerous projectiles. 
     Referring also to FIG. 10, there is another embodiment of the invention in which a working tip  80  is insert molded in the distal end of a shank  35 A, which may be essentially the same as the shank  35  shown in FIG.  3 . In this case, the working tip  80  has an exposed blade end  81  and a reduced cross-section inner end  82 , which preferably has a non-circular shape. This arrangement, with the resulting increased thickness of shank material surrounding the reduced cross-section end  82  has been found to provide improved resistance to relative rotation between the working tip  80  and the shank  35 A. 
     FIG. 11 discloses another alternative embodiment, in which a working tip  85  is insert molded in the end of the shank  35 A. In this case the working tip  85  has an axial bore  86  formed in the inner end thereof which fills with plastic material as at  87 , during the injection molding operation. Again, this configuration has been found to provide improved resistance to relative rotation of the parts. 
     While in the embodiments of FIGS. 10 and 11, the insert molded member is illustrated as being a working tip, it will be appreciated that the same principles could be applied to insert-molded tip holders. Also, while insert molding of the parts is disclosed in FIGS. 10 and 11, similar principles could be applied to parts which are press-fitted in bores in the end of the shank, in which case the bore could be formed to have a geometry similar to that of the part to be press-fitted therein. 
     Referring now to FIGS. 12-16, there is illustrated another embodiment of the invention, which includes an elongated shank  95 , which may be substantially the same as either the shank  35  of FIG. 3 or the shank  45  of FIG.  4 . The shank  95  has a reduced-diameter handle end  94  having equiangularly spaced apart therearound a plurality of radially outwardly extending ribs or splines  96 . The handle end  94  is adapted to be coupled to a handle, such as the handle  31  or  41 , in the manner described above, with the ribs or splines  46  digging in the material of the handle to inhibit rotation of the shank  95  relative to the handle. It will also be appreciated that, if desired, the shank  95  could be formed unitary with the handle in a one-piece molded construction, in the manner described above in connection with the screwdriver  10  of FIG.  2 . 
     The shank  95  has a working end  97  adapted to receive a working tip  100  fixedly therein. Preferably, the working tip  100  is insert molded in the working end  97  of the shank  95 , in the manner described above in connection with FIG. 3, but it will be appreciated that, alternatively, the working end  97  could have an axial receptacle  98  formed therein in which the working tip  100  is press fitted, similar to the embodiment of FIG. 4, described above. While the shank  95  is described as having a slight taper from the handle end to the working end, it will be appreciated that it could have an untapered cylindrical shape. 
     The working tip  100  has an elongated polygonal shank  101 , preferably hexagonal in transverse cross section, provided at one end with a work-engaging portion  102  including a work-engaging blade  103 , coupled to the shank  101  by a reduced neck  104 . Integral with the shank  101  at the other end is an anchor portion  105 , joined to the shank  101  as by a reduced neck  106 , and defining a plurality of equiangularly spaced flutes or recesses  107  alternating with blades  108 . In the illustrated embodiment, the work-engaging blade  103  is a flat blade for engaging a slot head screw, but it will be appreciated that it could have other shapes for engaging other types of fasteners or the like. 
     In the preferred embodiment, the anchor portion  105  is in the form of a fluted screwdriver tip of the type sold under the trademark PHILLIPS. It has been found that a no. 2 size of PHILLIPS-type fluted tip works well, but it will be appreciated that other tip sizes could also be used. The no. 2 size has four flutes resulting in a generally cruciform transverse cross section, with each blade  108  having a minimum thickness at the distal end  110  and a maximum thickness at a forward end  111 . Each blade  108  is also tapered in radial extent from a minimum at the distal end  110  to a maximum at a point  113 . Each flute  107  has a maximum depth in a transverse plane through the points  113 , the depth reducing therefrom, both forwardly and rearwardly. There results a transverse cross-sectional area of the anchor portion  105  which has a minimum value at the distal end  110  and a maximum value at the forward (right-hand, as viewed in FIGS. 12-14) ends of the flutes  107 . 
     In use, the anchor portion  105  and most of the polygonal shank  101  cooperate to form a mounting portion which is embedded in the working end  97  of the shank  95 , so that the flutes  107  are substantially filled with the material of the shank  95 , as can best be seen in FIG.  16 . This provides a firm interlock between the working tip  100  and the shank  95 , affording greatly increased torsional strength of the joint to resist relative rotation of the working tip  100  and the shank  95 . It has also been found that this tip geometry significantly reduces failures in the plastic material of the shank. 
     While, in the preferred embodiment, the working tip is in the form of a double-ended, commercially available bit, for reasons of economy, it will be appreciated that custom-design configurations could also be utilized. More specifically, while a PHILLIPS-type fluted anchor portion configuration is preferred, other types of fluted or recessed configurations could be utilized, as long as the flutes have a fairly substantial depth. 
     From the foregoing, it can be seen that there has been provided an improved electrically insulating hand tool and method of making same, wherein the tool can be fabricated without the use of adhesives in a simple and economical process which incorporates injection molding, the tool shanks being formed of a high-strength injection-moldable material, which affords improved electrical insulation characteristics. 
     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.