Patent Publication Number: US-6655241-B2

Title: Anti-skip fastener tightening and/or extraction device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to fastener driver tool bits and, more particularly, to fastener driver tool bits that include features that prevent or reduce the tendency of a tool bit end to “skip” or “slide out” from the slots in fastener heads. 
     2. Background of the Prior Art 
     Screwdrivers, tool bit fastener drivers, Phillips screwdrivers and the like, when inserting or extracting a fastener from a workpiece, will at times “slip” or “skip” from the slot in the head of a fastener while imparting rotary motion to the fastener. Generally, the bit end of the fastener driver skips from the fastener after the fastener has been completely inserted into the workpiece, or when attempting to remove a corroded or relatively “old” fastener from the workpiece. When the tool bit skips from the fastener, the end of the bit has a tendency to tear away or wear down a portion of the side walls forming the slot in the head of the fastener. Repeated skips can deform the slot side walls such that the tool bit is incapable of imparting rotary motion to the fastener. 
     Prior art driver bits have attempted to correct the skipping problem by including relatively small recesses in the side walls of the flutes or crossing members that form the tip or drive portion of the bit. The recesses form edges that grip or “bite” into the side walls of the slot to promote rotary motion transfer between the driver bit and fastener. The recesses are machined in each side wall of each crossing member such that a right angle is formed between the recesses and the longitudinal axis of the bit when taking a side elevation view of the bit. Further, recesses are machined radially across the flutes to form multiple concentric arc segments when taking a drive end elevation view of the bit as disclosed in U.S. Pat. No. 4,998,454. 
     The problem with prior art driver bits that include recesses that grip the side walls of the slot of the fastener, is that there are an excessive number of recesses which structurally weaken the bits causing the bits to routinely break or deform when rotary motion sufficient to rotate the fastener, is imparted upon the bit from a rotary driver. A need exist for a driver bit that is capable of gripping the side walls that form the slot in the head of a fastener, and that is sufficiently strong to impart, without deforming or breaking, required rotary motion upon the fastener. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a screwdriver type tool bit that will not slide out from the slots (anti-skip) in a fastener when a rotary force is imposed upon the tool bit while inserting or extracting the fastener from a workpiece. 
     A principal object of the present invention is to provide an improved fastener driver that “grips” a side wall forming a slot in the head of the fastener. A feature of the improved fastener driver is one or more recesses in predetermined side walls of crossing members of a “Phillips type” screwdriver. An advantage of the improved fastener driver is that engagement between the driver and the fastener is maintained while the fastener is inserted into or extracted from a workpiece. Another advantage of the improved fastener driver is that constant rotary motion is imparted from the driver to the fastener when the fastener is inserted into or extracted from a workpiece. 
     Another object of the present invention is to provide gripping capability to a fastener driver while maintaining the structural strength of the driver. A feature of the improved fastener driver is one or more recesses forming edges that engage or “bite” into walls forming a driver receiving slot in a fastener. Another feature of the improved fastener driver is one or more recesses disposed in one of two side walls of each crossing member, the fastener driver being comprised of four crossing members. An advantage of the improved fastener driver is that the bit end of the driver maintains engagement with the fastener while imparting rotary force thereupon without bending or breaking the bit end. 
     Yet another object of the present invention is to provide a fastener driver having one or more recesses in side walls of the crossing members, the recesses being inclined relative to the longitudinal axis of the driver. A feature of the improved fastener driver is longer gripping edges formed by the inclined recesses. An advantage of the improved fastener driver is that gripping capability is increased without decreasing structural integrity. 
     Still another object of the present invention is to provide an improved blade type or “standard” fastener driver. A feature of the improved standard screwdriver is one or more recesses machined in opposing side walls of the screwdriver. An advantage of the improved standard screwdriver is that the screwdriver is capable of gripping a corresponding fastener thereby maintaining engagement between the screwdriver and fastener while the fastener is inserted into or extracted from a workpiece. 
     Another object of the present invention is to improve the gripping capability of a standard screwdriver while maintaining structural strength. A feature of the standard screwdriver is one or more recesses extending across a portion of each side wall forming the bit end of the screwdriver. An advantage of the standard screwdriver is that substantially the same amount of bitting edge from the partially extending recesses (compared to a recess extending totally across each side wall) engage the side walls forming the corresponding slot of the fastener thereby providing gripping capability and maintaining the quantity of rotational force that may be imparted from the screwdriver to the fastener. 
     Another object of the present invention is to improve the gripping capability of a Phillips screwdriver when inserted into relatively shallow receiving recesses disposed in a fastener. A feature of the screwdriver is one or more recesses disposed relatively close to the bit end. Another feature of the screwdriver is a crowned bit end formed from arcuate crossing members. An advantage of the screwdriver is that the entire edge of the recesses engage corresponding side walls of the recesses in the fastener to maximize gripping capability. Another advantage of the screwdriver is that the arcuate crossing members allow the crown portion of the bit end to engage a center portion of the fastener while the crossing members accommodate a foreign material built-up in the corners of the fastener recesses thereby promoting complete engagement between the edges of the recesses in the bit end and the walls of the recesses in the fastener. 
     Briefly, the invention provides an anti-skip fastener tightening and/or extraction device comprising a tool bit end having a plurality of crossing members, each crossing member having at least one recess positioned in a side wall, said recesses forming edges that engage corresponding portions of a fastener to maintain engagement between said tool bit end and the fastener when forcibly rotating the fastener to drive the fastener into a workpiece, said recesses forming edges that engage corresponding portions of the fastener to maintain engagement between said tool bit end and the fastener when forcibly rotating the fastener to extract the fastener from a workpiece. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing invention and its advantages may be readily appreciated from the following detailed description of the preferred embodiment, when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective view of tool bit having recesses in a side wall in accordance with the present invention. 
     FIG. 2 is a front elevation view of the tool bit depicted in FIG.  1 . 
     FIG. 3 is a top elevation view of the tool bit depicted in FIG.  1 . 
     FIG. 4 is, a back elevation view of the tool bit depicted in FIG.  1 . 
     FIG. 5 is a top elevation view of a typical “Phillips type” fastener. 
     FIG. 6 is perspective view of an alternative embodiment of the tool bit depicted in FIG. 1 in accordance with the present invention. 
     FIG. 7 is a perspective view of an alternative tool bit having recesses in a side wall in accordance with the present invention. 
     FIG. 8 is a perspective view of an alternative tool bit for a fastener with relatively shallow tool bit receiving recesses. 
     FIG. 9 is a side elevation view of the end of the alternative tool bit of FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-5, an anti-skip fastener tightening and/or extraction device is denoted by numeral  10 . The device  10  includes a tool bit end  12  having a cross configuration when taking an end view, and formed from four substantially identical crossing members  13 ,  14 ,  15  and  16  that are radially separated a substantially equal degree of arc thereby configuring a typical screwdriver bit for a standard cross or “Phillips” head fastener  17 . Crossing members  13  and  14  have at least one, but preferably a plurality of parallel recesses  18  disposed in first side walls  20  and  21  such that an acute angle is formed (when taking a front elevation view of the device, see FIG. 2 ) between the recesses  18  and a mid-portion of an inclined edge  22  of first and second inclined walls  24  and  25  of members  13  and  14 . Crossing members  15  and  16  have at least one, but preferably a plurality of parallel recesses  26  disposed in second side walls  28  and  29  such that an acute angle is formed (when taking a back elevation view of the device, see FIG. 4) between the recesses  26  and a mid-portion of an inclined edge  30  of first and second inclined walls  32  and  34  of the second crossing member  16 . 
     The recesses  18  in first side walls  20  and  21  form edges  36  that engage and grasp the fastener  17  by “digging” into corresponding first side walls  38  and  40  of fastener  17  to maintain engagement between the tool bit end  12  and the fastener  17  when forcibly rotating the fastener  17  to drive the fastener  17  into a workpiece (not shown). The recesses  26  in the second side walls  28  and  29  form edges  42  that engage and grasp the fastener  17  by “digging” into corresponding second side walls  44  and  46  of fastener  17  to maintain engagement between the tool bit end  12  and the fastener  17  when forcibly rotating the fastener  17  to extract the fastener  17  from a workpiece. The recesses  18  and  26  are relatively narrow and substantially horizontal when taking front or back elevation views. The recesses  18  in the first side walls  20  and  21  extend across the first side walls  20  and  21  from an inner edge  48  to inclined edge  22  of corresponding inclined walls  24  and  25 . The recesses  26  in the second side walls  28  and  29  extend across the second side walls  28  and  29  from an inner edge  48  to inclined edge  30  of corresponding inclined walls  32  and  34 . The recesses  18  and  26  are separated a distance relatively larger than their lateral dimension and include a relatively shallow “depth” relative to the thickness of the crossing members  13 - 16  of the tool bit end  12 . 
     The recesses  18  and  26  may be orientated perpendicular or parallel to the central axis of the tool bit and may be positioned at any portion of the first and second side walls  20 ,  21 ,  28  and  29  depending upon the size of the fastener  17  and the corresponding “depth” of the first and second side walls  38 ,  40 ,  44  and  46  into the fastener  17 . Generally, the deeper the first and second side walls of the fastener  17 , the greater the longitudinal dimension of the recesses  18  and  26  across the first and second side walls of the tool bit end  12 . The longitudinal dimension is increased by angling the recesses  18  and  26  to a more vertical position extending from the inner edge  48  to inclined edges  22  and  30 , respectively as depicted in FIG.  6 . Further, the recesses  18  and  26  may vary in quantity from one to a plurality of recesses depending upon the desired “griping” capability of the device  10  upon the fastener  17 . 
     Although the figures depict only the first side walls  20  and  21  of crossing members  13  and  14 , and the second side walls  28  and  29  of crossing members  15  and  16  having recesses therein, all eight side walls of the tool bit end  12  may include recesses to improve the gripping capability of the device  10 . More specifically, second side walls  56  and  58  of crossing members  13  and  14 , respectively, and first side walls  54  and  52  of crossing members  15  and  16 , respectively, may include recesses configured and disposed substantially identical to the recesses  18  and  26  in corresponding side walls. However, adding recesses in the tool bit end  12  weakens the metal forming the end  12  thereby reducing the amount of rotational force that can be applied to the device  10  without deforming the end  12 . Positioning recesses in opposing side walls of the same crossing member such that bottom portions are directly opposite, further reduces the rotational force that may be applied. To minimize metal degradation, recesses in opposing side walls of a crossing member may be staggered whereby the quantity metal separating opposing lower portions of corresponding recesses is increased. Thus, keeping the quantity of recesses to a minimum while adding optimum gripping capability to the tool bit end  12  and/or avoiding recesses in opposite side walls of one of the crossing members  13 - 16  increases the amount of rotary force that may be imparted upon a fastener  17 . 
     Alternatively, the tool bit end  12  may be designed to provide gripping capability in only one rotary direction. More specifically, the tool bit end  12  may be required to grip the fastener  17  to assemble a workpiece thereby requiring the recesses to grip the fastener  17  for insertion only. Recesses that are disposed to remove fasteners would not be included. Should the tool bit end  12  be required to only remove fasteners  17  from a workpiece, recesses that grip the fasteners  17  for extraction would be machined in the tool bit end  12 , recesses that insert fasteners  17  would not be included. 
     In operation, a standard screwdriver bit  12  configured to insert or remove a Phillips head fastener  17  from a workpiece, is machined via techniques well known to those of ordinary skill in the art such that one or more recesses  18  are formed in the first side walls  20  and  21  of crossing members  13  and  14  for gripping the first side walls  38  and  40  of the fastener  17  during the extraction (counter-clockwise rotation) of the fastener  17  from a workpiece. Alternatively, one or more recesses  26  are machined in the second side walls  28  and  29  of crossing members  15  and  16  for gripping the second side walls  44  and  46  of the fastener  17  during the insertion (clockwise rotation) of the fastener  17  into the workpiece. Should the bit  12  be required to grip the fastener  17  for both extraction and insertion, recesses  18  and  26  would be machined in corresponding first and second side wall  20 , 21 , 28  and  29 . Should a relatively small amount of rotary force be imparted upon the fastener  17  by the bit  12 , and a relatively large gripping capability be required to insert and/or extract the fastener  17  from a workpiece, recesses  18  and/or  26  may be machined in corresponding first side walls  20 , 21 , 52  and  54  and/or second side walls  28 , 29 , 56  and  58  of the crossing members  13 , 14 , 15  and  16  (see FIGS.  1  and  3 ). 
     Referring now to FIG. 7, a standard “blade” screwdriver tip  60  is depicted having a plurality of recesses  62  machined in first and second sides  64  and  66  of the tip  60 . The recesses  62  are parallel to the edge  68  of the tip  60 , extend laterally across substantially half the tip  60 , and include a “depth” relatively shallow in comparison to the “thickness” of the tip  60  thereby substantially maintaining the structural strength of the tip  60 . The recesses  62  on each side  64  and  66  of the tip  60  are separated a distance relatively greater than the lateral dimension of the recesses  62 . Machining recesses  62  across half the tip  60 , maintains tip integrity but provides gripping capability in only one rotary direction. Extending the recesses  62  across the entire surface of the tip  60  would enable the tip  60  to grip the fastener in both rotary direction, but would decrease the structural strength of the tip  60  thereby reducing the amount of rotary force that may be imparted upon the screwdriver. Further, the recesses  62  may be inclined relative to the edge  68  or may be increased in quantity to increase the gripping capability of the tip  60 , but resulting in a corresponding decrease in structural strength and the amount of rotational force that may be imparted from the tip  60  to the fastener. Staggering or varying the distances between the recesses  62  of the first side wall  64  and the edge  68  of the tip  60  relative to the distances between the recesses  62  of the second side wall  66  and the edge  68  of the tip, avoids “back-to-back” placement of the recesses  62 , thereby substantially maintaining the structural integrity of the tip  60 . 
     Referring now to FIGS. 8 and 9, an alternative anti-skip fastener tightening and/or extraction device is denoted by numeral  100 . The device  100  of FIG. 8 is substantially the same as the device  10  of FIG. 1 except that the recesses  18  and  26  in the alternative device  100  have been disposed closer to the tool bit end  12  to engage corresponding side walls  38 ,  40 ,  44  and  46  of a fastener  17  having relatively “shallow” recesses  102  that form the side walls  38 ,  40 ,  44  and  46 . The device  100  further includes arcuate crossing members  13 - 16  that accommodate a slight grease, dirt and/or metal filing “buildup”  103  in corners  104  of the recesses  102  in the fastener  17 . Thus, the device  100  is allowed to insert into the fastener  17  until a slightly crowned portion  106  of the device  100  engages a center portion  108  of the fastener  17 , and the arcuate crossing members  13 - 16  engage and forcibly compress the grease and dirt buildup  103 . The arcuate configuration facilitates total engagement and maximum “gripping” capability between the recess  18  and  26  of the device  100  and the side walls of a fastener  17  with shallow recesses  102  that have a foreign material buildup therein. 
     The foregoing description is for purposes of illustration only and is not intended to limit the scope of protection accorded this invention. The scope of protection is measured by the following claims, which should be interpreted as broadly as the inventive contribution permits.