Abstract:
A staple driving tool and a method for clamping and stapling together two or more steel workpiece layers as in light gauge steel framing for residential and commercial buildings, truss assembly, and the like. The stapling tool has a guide body and a jaw assembly supporting an anvil. The jaw assembly is pivoted to a mounting bar extending along and beneath the tool magazine. The jaw is pivotable between a normal open position and a closed position wherein it clamps the steel workpiece layers to be joined between the anvil and the guide body prior to stapling. The jaw is pivotable by an air cylinder actuated toggle mechanism. An air valve normally connects the air cylinder to atmosphere. When actuated, the air valve connects the air cylinder to a source of pressurized air, shifting the jaw to clamping position. The air valve may be actuated by one of the tool safety and the tool trigger. Thereafter, the tool operator may release the trigger or safety to reposition the tool, or the operator may complete actuation of the trigger to drive a staple through the clamped steel layers, causing the anvil the clinch the staple against the steel layers. As the staple approaches the steel layers to be joined, a member enters between the staple legs to prevent buckling thereof until the staple penetrates the steel layers, whereafter the member is shifted by the staple crown and driver from between the legs to accommodate the staple crown and driver.

Description:
TECHNICAL FIELD 
     The invention relates to a staple driving tool and a method of use thereof, and more particularly to such a tool and method wherein the tool is used to clamp together at least two workpieces of relatively light gage metal and to hold the workpieces in place during the driving of a staple therethrough. 
     BACKGROUND ART 
     While not intended to be so limited, the tool and method of the present invention are particularly well adapted for use in light gage steel framing for residential and commercial buildings. An example of another use for the tool and method of the present invention is the assembly of trusses and the like. 
     Today, most light gauge steel framing for residential and commercial buildings is done with an electric screw driving tool using self-drilling and tapping screws. The parts to be joined together are manually held in place while the screw is driven. Screws are easily dropped and lost. The use of the tool and method of the present invention provides a more flush surface on which to apply dry wall. The method of the present invention is easier than the use of self-tapping screws and is less time consuming. The staple driving tool clamps the metal framing members together prior to stapling and, if necessary, this clamping can be readjusted prior to stapling. Staples are cheaper than screws and are self contained in strips or “sticks”. Thus, staple loss and waste is much lower than with screws. The staple driving tool is provided with a safety and the clamping mechanism is actuated either by the safety or by the manual trigger of the tool. 
     As indicated above, in the typical prior art light gauge steel framing techniques employed, the individually hand driven self-tapping, screws are driven with the aid of an electric screw driver. This approach is time consuming. Pneumatically driven steel framing pins have also been used, but it has been found that pins generally do not perform as well as screws in cyclic loading conditions. The present invention will allow for forced entry fastener installation using electric or pneumatic tools, not effected by vibration or cyclic loading to the extent that typical forced entry framing pins are. Another advantage of the present invention is the reduction in cost of assembly when using light gauge steel framing members. 
     The pivotal clamping jaw, the link, the toggle elements and the air cylinder of the present invention, to be described hereinafter, are affixed to a mounting bar which extends along and beneath the tool magazine. This assembly may be applied (with minor modification) to a number of existing staple driving tools. In FIG. 1 to be discussed hereinafter, this mechanism is shown affixed to a staple driving tool manufactured by Senco Corporation of Cincinnati, Ohio and sold under the designation SNS-45. 
     DISCLOSURE OF THE INVENTION 
     According to the invention there is provided a staple driving tool and a method for clamping and thereafter stapling together two or more light gauge steel workpiece layers as in light gauge steel framing for residential and commercial buildings. The stapling tool has a handle portion, a main body portion and a guide body, together with a staple containing magazine. The tool is further provided with a jaw assembly supporting an anvil. The jaw assembly is pivoted to a mounting bar extending along and beneath the tool magazine. The jaw is pivotable between a normal open position and a closed position wherein it clamps the steel layers to be joined between the anvil and the guide body prior to stapling. The jaw is shifted between open and clamping positions by an air cylinder actuated toggle mechanism. The air cylinder, in turn, is operated by an air valve mounted on the tool. 
     The air valve is actuated by either the tool safety or the tool trigger. This actuation causes the workpieces to be clamped together. The tool operator may release the trigger or safety to reposition the workpieces, or the operator may complete operation of the trigger to drive a staple through the clamped steel layers. The anvil, supported by the jaw, causes the staple to be clinched against the steel layers being joined. The staple driving tool may also be provided with a member which is located between the staple legs as the staple approaches the steel layers to be joined. The member cooperates with the drive track of the guide body to prevent buckling the staple legs as they penetrate the steel layers. Thereafter, the member is shifted from between the legs by the staple crown and the driver, enabling the staple to be fully clinched. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a stapler provided with the anvil, jaw and toggle mechanism of the present invention. 
     FIG. 2 is a side elevational view of the anvil, jaw and toggle mechanism in closed position and affixed to the stapler magazine. 
     FIG. 3 is a top, left side, rear end prospective view of the magazine, anvil, jaw and toggle mechanism. 
     FIG. 4 is a front elevational view of the mechanism of FIGS. 2 and 3. 
     FIG. 5 is a rear elevational view of the assembly of FIGS. 2 and 3, without the air cylinder. 
     FIG. 6 is a fragmentary side elevational view of the magazine, guide body, and the anvil, jaw and toggle mechanism of the present invention in open condition. 
     FIG. 7 is a fragmentary side elevational view illustrating the elements of FIG. 6 in closed position, clamping a pair of workpieces. 
     FIG. 8 is a plan view of the anvil and its staple forming depression. 
     FIG. 9 is an elevational interior view of the forward portion of the guide body and drive track therein. 
     FIG. 10 is a cross-sectional view taken along section line  10 — 10  of FIG. 9, and illustrating the leaf spring of the guide body in its innermost position. 
     FIG. 11 is a cross-sectional view similar to FIG. 10, but illustrating the leaf spring in its forwardmost position. 
     FIG. 12 is a cross-sectional view similar to FIG. 10, but illustrating another embodiment of an anti-buckle device in its extended position. 
     FIG. 13 is a cross-sectional view similar to FIG.  12  and illustrating the anti-buckle device in its retracted position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is first made to FIG. 1, which illustrates an exemplary pneumatic stapler provided with the clamping and staple forming mechanism of the present invention. The stapler is generally indicated at  1  and comprises a main body portion  2  and a handle portion  3 . Beneath the main body portion there is a guide body  4  providing a drive track  5  for the staples (see FIGS.  9 - 11 ). The staples may be joined together by adhesive means, tape, wire or the like into “sticks” of staples, as is well known in the art. A stick of staples is insertable in the magazine  6  of the stapler  1 . The forward end of the magazine is mounted on the guide body  4  and is connected to the drive track  5 , in the usual manner. The rearward end of the magazine is supported by an extension  7 , which depends downwardly from handle  3 . 
     As is well known in the art, the main body portion  2  of stapler  1  contains a cylinder (not shown) with a piston (not shown) to which a staple driver (not shown) is affixed. The lowermost end of the staple driver is normally engaged in the uppermost portion of the drive track  5  of guide body  4 . The cylinder is surmounted by a main valve (not shown) which, when open, allows pressurized air to enter the cylinder and drive the piston and driver downwardly, causing the staple to pierce the metal pieces to be joined and to be clinched against the metal pieces by virtue of the anvil depression. The main valve is opened by a remote valve (not shown) actuated by a manual trigger  8 , as is well known in the art. The tool I may be provided with a safety, a portion of which is shown at  9 . The safety, when pressed against the workpieces to be joined, enables the operator to actuate trigger  8 . Such safeties are well known in the art. The rearward end of handle portion  3  is provided with a fitting  10  which may be a quick connect/disconnect fitting for an air hose (not shown) from a source of pressurized air (not shown). By virtue of this connection, portions of the main body  2  and the handle  3  constitute a reservoir for pressurized air, again as is well known in the art. 
     Reference is now made to FIGS. 2-6 wherein the anvil and clamping mechanism of the present invention is most clearly shown. The mechanism comprises a mounting bar  11  affixed to the bottom of magazine  6 , and extending substantially the length thereof. The mounting bar  11  has a rearward downwardly depending extension  12  and a somewhat larger forward downwardly depending extension  13 . Extension  12  is adapted to be flanked by bifurcations  14  and  15  affixed to the rearward end of an air cylinder  16 . Extension  12  and bifurcations  14  and  15  are provided with coaxial bores (one of which is shown at  17 ). These bores are intended to receive a pivot member  18  by which bifurcations  14  and  15  are pivotally affixed to extension  12 . Pivot member  17 , and other pivot members to be described hereinafter can be of any appropriate type including pivot pins, bolts, roll pins, headed pins with a nut or cotter pin at the free end thereof, or the like. 
     The rearward portion of extension  13  is adapted to support a pair of identical toggle elements  19  and  20  comprising a toggle assembly generally indicated at  21 . To this end, toggle elements  19  and  20  and the extension  13  are provided with coaxial holes (one of which is shown at  22 ) adapted to receive a pivot member  21   a  so that toggle elements  19  and  20  are pivotally mounted with respect to extension  13 . 
     Cylinder  16  has a piston rod  23  terminating in a portion  23   a  just nicely received between toggle elements  19  and  20 . Toggle elements  19  and  20 , together with piston rod portion  23   a  are provided with coaxial bores (one of which is shown at  25 ) so that they may be pivoted together by means of a pivot member  21   b.    
     The jaw assembly of the clamping mechanism is generally indicated at  27  and comprises two substantially L-shaped jaw members  28  and  29 . As is perhaps best shown in FIG. 2, the upright leg  29   a  (as viewed in that Figure) terminates in a rounded end  29   b . The substantially horizontal leg  29   c  terminates in a substantially horizontal surface  29   d  (as viewed in FIG.  2 ). It will be appreciated that jaw member  28  is identical to jaw member  29  and is of the same peripheral configuration, with an upright leg  28   a  with a rounded end  28   b , a substantially horizontal leg  28   c  with a substantially horizontal surface  28   d.    
     A T-shaped anvil support is shown at  30 . The upper portion  30   a  of the T-shaped anvil support  30  rests upon the horizontal end surfaces  28   d  and  29   d  of L-shaped members  28  and  29  as is shown in FIGS. 2 and 4. The anvil and clamping member  31  is a block like member which rests upon the top surface of support  30  and is bolted thereto by a pair of bolts, one of which is shown at  32  in FIG. 2, and the other of which is shown at  33  in FIGS. 4 and 5. The support  30  has a downwardly depending central portion  30   b  which is just nicely received between the ends of jaw elements  28  and  29  and is affixed therebetween by pin or bolt  30   c . The horizontal surfaces  28   d  and  29   d  prevent rocking of support  30  and thus of anvil and clamp member  31 . 
     The upper rounded ends  28   b  and  29   b  of the upright legs  28   a  and  29   a  lie to either side of the forward portion of extension  13 . Coaxial bores (one of which is shown at  34 ) are formed in the leg ends and the forward portion of extension  13  for receipt of a pivot member  27   a . As a consequence, the jaw assembly  27  is rockable about pivot member  27   a  between an unclamping position and a clamping position. Finally, the juncture between legs  28   a  and  28   c  and legs  29   a  and  29   c  have extending therebetween a link  36 . The link is pivoted to jaw elements  28  and  29  by pivot member  27   b  passing through coaxial bores in these elements (one of which is shown at  38 ). The overall clamping assembly is completed by pivotally attaching the other end of link  36  to toggle elements  19  and  20  by means of a pivot member  21   c  passing through coaxial bores (one of which is shown at  40  in FIG. 3) located in toggle elements  19  and  20  and the adjacent end of link  36 . As will be clear from FIGS. 1,  2 ,  3 ,  6  and  7 , when pressurized air is introduced in to the cylinder  16  to cause piston rod  23  to be extended, the overall jaw assembly  27  will clamp a pair of steel workpieces between the anvil  31  and guide body  4  as shown in FIG.  7 . When cylinder  16  is vented to atmosphere, the piston rod  23  will be retracted by virtue of a compression spring (not shown) within air cylinder  16 , and the jaw assembly  27  will return to its normal open position as shown in FIG.  6 . Referring to FIG. 1, the tool  1  is provided with an air valve  35 . Air valve  35  has an inlet  35   a  connected by a tube  36  to a branch  10   a  of quick connect/disconnect fitting  10 . Thus, the tube  36  and branch  10   a  are capable of connecting valve  35  to the source of pressurized air (not shown). 
     Air valve  35  has an outlet port  35   b  connected by tube  37  to the rearward end of piston  16 . 
     When air valve  35  is in its normal, unactuated state, it connects tube  37  and the interior of piston  16  to atmosphere. At the same time, it closes inlet port  35   a  from the source of pressurized air. When the cylinder  16  is connected to atmosphere, the compression spring (not shown) therein will cause piston  23  to retract shifting toggle assembly  21  and link  36  in such a way that the jaw assembly  27  will be in its normal, open position. When air valve  35  is actuated, inlet port  35   a  will be open so that the valve receives air under pressure from the source thereof. The outlet port  35   b  of air valve  35  will be closed from atmosphere and open to tube  37 , allowing the pressurized air to actuate cylinder  36 , causing piston  23  to shift forwardly against the action of the compression spring (not shown) within cylinder  16 . This, in turn, via toggle assembly  21  and link  36  will cause the jaw assembly  27  to assume its clamping position, clamping two or more metallic workpieces together to be stapled. 
     Air valve  35  may be actuated either by safety  9  or manual trigger  8 . When air valve  35  is actuated by safety  9 , the operator of tool  1  arranges the pieces to be joined and then presses the bottom end of guide body  4  against the workpieces, shifting safety  9  to its actuated position. This immediately actuates air valve  35  causing the workpieces to be clamped by the jaw assembly  29  against the bottom end of guide body  4 . Shifting safety  9  also enables trigger  8 . The safety having shifted to its actuated position, the operator can now actuate manual trigger  8  driving and clinching a staple through the workpieces to join them together. 
     When the manual trigger  8  is used to actuate air valve  35 , the operator of tool  1  will arrange the workpieces in position to be stapled and will bring the bottom end of guide body  4  to bear against the workpieces shifting safety  9  to its actuated position enabling manual trigger  8 . Manual trigger  8  will be operatively connected to valve  35  by a lateral extension or the like (not shown). Initial squeezing of the trigger will activate valve  35  causing the workpieces to be clamped by jaw  27  against the bottom end of guide body  4 . Further squeezing of the trigger will drive a staple through the workpieces and clinch the staple legs. 
     When both clamping and staple driving are accomplished by the manual trigger, the tool operator can first clamp the workpieces by partial actuation of trigger  8 . If the alignment of the workpieces to be joined is not correct, the operator can release the trigger and thus unclamp the workpieces. Thereafter the operator can realign the workpieces and re-clamp them. If satisfied with their alignment, the operator can fully actuate the trigger and staple the workpieces together. 
     Reference is now made to FIG. 8 wherein the anvil  31  is shown in plan. The anvil  31  has a top surface  31  a as viewed in FIG.  8 . This top surface is provided with a rectangular recessed pocket  41  having sides  41   a  and  41   b  and ends  41   c  and  41   d . Pocket  41  has a curved bottom extending from end  41   c  to end  41   d . The curved bottom is configured to redirect the free ends of the staple legs in a curvilinear fashion back against the workpieces being joined. The sides  41   a  and  41   b  extend downwardly and are perpendicular to top surface  31   a . In FIG. 8, a staple  42  is shown having a crown portion  42   a  and legs  42   b  and  42   c.    
     It will be noted that the pocket  41  is skewed with respect to the surface  31   a  in which it is formed. The axis of the staple crown  42   a  is parallel to the forward and rearward edges of surface  31   a . The sides  41   a  and  41   b  of pocket  41  lie at an angle A of about 30 degrees to the staple crown axis. This angularity can have a range of from about 10 degrees to about 30 degrees depending upon the size and gauge of the staple being used. As is clear from FIG. 8, this skewing of pocket  41  causes the staple legs to be formed at an angle to the staple crown and substantially parallel to each other. Therefore, during clinching, the staple legs  42   c  and  42   d  do not interfere with each other or with the staple crown. It would be within the scope of the invention to provide the anvil with two pockets, one for each staple leg, to accomplish the same result. 
     It will be noted from FIG. 9, for example, that the staples  42  of the present invention have a relatively short crown with legs which are greater in length than the crown. A “narrow crowned staple” (i.e. a staple with a relatively short crown) is advantageous in that it improves penetration in the metal workpieces without buckling. 
     Reference is made to FIGS. 9,  10  and  11 . FIG. 9 is an interior view of the forward portion  4   a  of guide body  4 . The forward portion  4   a  has a pair of parallel, spaced vertical surfaces  43  and  44 , which constitute the forward surfaces of guide track  5 . Edge elements  45  and  46  serve as the sides of drive track  5 . Drive track  5  is completed by the rear portion  4   b  of guide body  4  (see FIG. 10) which provides the rear surface  4   c  of the drive track  5 . Drive track  5  is adapted to receive the driving end of the tool driver (not shown). When the driver is in its retracted position, its lower end will be in the uppermost part of drive track  5 . When the driver is in its normal retracted position, the forwardmost staple of the stick of staples in magazine  6  is urged forwardly by a staple advancing mechanism (not shown) through an opening  47  in rear portion  4   b  of drive track  4  into drive track  5 . Thus, when the driver is retracted at the end of a cycle, the staple advancing mechanism will locate the next forwardmost staple of the stick in the drive track so that the next driving cycle can be initiated when desired. 
     It will be noted that the forward surfaces  43  and  44  of drive track  5  are joined by a recessed wall  48 , which extends downwardly from the top of forward portion  4   a  and ends at  49 . As is clear from FIG. 10, a similar recessed wall  50  has an upper end  51  spaced from the end  49  of wall  48  and a lower end  52  at the bottom of the guide body  4 . The wall  48  has a downwardly and inwardly sloping portion  52 . The wall  50  also has downwardly and inwardly sloping portion  53 . The reasons for the sloping portions will be apparent hereinafter. 
     As is best shown in FIG. 10, the forward portion  4   a  of guide body  4  has mounted thereon a leaf spring  54 . Leaf spring  54 , as viewed in FIG. 10, has a first vertical portion  54   a  which is attached and lies along the outside vertical surface of wall portion  48  of the front portion  4   a  of guide body  4 . Leaf spring  54  has a second portion  54   b  which lies along the downwardly and inwardly sloped portion  52  of wall  48  The leaf spring portion  54   b  extends through the opening defined by the bottom edge  49  of wall  48  and the top edge  51  of wall  50 . Leaf spring portion  54   c  terminates in a vertical portion  54   c , the inside surface of which is substantially coplanar with the wall surfaces  43  and  44  (see FIG.  9 ). Leaf spring portion  54   c  terminates in downwardly and inwardly sloping spring portion  54   d . The leaf spring portion  54   d , in turn, terminates in a vertical portion  54   e  which is substantially parallel to the rear drive track surface  4   c  defined by rearward guide body portion  4   b  (see FIG.  10 ). The portion  54   e  is located near this rear drive track surface  4   c , as is shown in FIG.  10 . 
     When a staple  42  enters the drive track  5  through opening  45 , and is driven downwardly by the tool driver (not shown), the staple  42  will be confined by side members  45  and  46 , forward surfaces  43  and  44  and rearward surface  4   c  making up drive track  5 . When the staple  42  reaches a point where its legs  42   c  and  42   d  are at the bottom of the drive track  5  and in contact with the steel layers to be stapled, it will be noted that the crown  42   a  of the staple  42  will be located between the rear drive track surface  4   c , the front drive track surfaces  43  and  44  and the portion  54   c  of leaf spring  53 . Meanwhile, the leaf spring portion  54   e  is located between the legs  42   c  and  42   d  of the staple  42 . As a result of this, when the staple  42  begins to penetrate the steel layers, the legs  42   c  and  42   d  will be prevented from buckling forwardly by front wall portions  43  and  44 , rearwardly by rear wall  4   c , laterally outwardly by side wall portions  45  and  46  and laterally inwardly by leaf spring portion  54   e.    
     Once the staple legs  42   c  and  42   d  have penetrated the steel layers, the crown of the staple will ride along downwardly and inwardly sloped leaf spring portion  54   d , causing the bottom part of the leaf spring to shift to the left as viewed in FIG. 10 to the position shown in FIG.  11 . While the leaf spring portion  54   e  is no longer between the legs of the staple, it is no longer needed for this purpose since the legs have already penetrated the steel&#39;s layers. The driver will drive the staple out of drive track  5 , the bottommost part of the driver passing between rear drive track wall  4   c  and the lower portion  54   e  of leaf spring  54 . At the end of the driving cycle, the driver will retract to its normal position, and the leaf spring  54  will return to its normal position shown in FIG.  10 . 
     The forward portion  4   a  of guide body  4  may be provided with a pair of parallel spaced bifurcations  55  and  56  (see FIG. 9) by which it is pivoted to the main body portion  2  of tool  1 . In this manner, the forward guide body portion  4   a  serves as an openable gate to the drive track  5  should a staple become jammed in the drive track. The provision of an openable gate is well known in the art. It will be understood that the gate will be provided with some form of latch mechanism (not shown) to keep it closed during operation of the tool, again as is well known in the art. 
     It will be understood by one skilled in the art that a non-flexible metal piece could be positioned between the staple legs by a resilient member which would enable the staple crown and driver to move the non-flexible piece out of the drive track during the final portion of the drive. Such a structure is shown in FIG.  12 . 
     In FIG. 12 a guide body  57  is shown, generally similar to guide body  4  of FIG.  10 . The guide body has a forward portion  57   a  and a rearward portion  57   b . The portion  57   b  has an opening  58  therein through which staples pass from the magazine  6  (not shown in FIG. 12) to the guide track  59 . 
     The forward portion  57   a  may be provided at its upper end with a pair of bifurcations, one of which is shown at  60 . These bifurcations are equivalent to bifurcations  55  and  56  of FIG.  9  and serve the same purpose. At its lower end, the forward portion  57   a  has a hollow chamber  61 . Chamber  61  communicates with drive track  59  through an opening  62 . Opening  62  is slightly smaller than the inside vertical dimension of chamber  61  creating retaining tabs  63  and  64 , the purpose of which will be apparent hereinafter. The opposite end of chamber  61  is closed by removable plate  65 . 
     As viewed in FIG. 12, the drive track  59  has a forward vertical surface  66  constituting the rear surface of guide body forward portion  57   a , a rear surface  67  constituting the forward surface of the rearward portion  57   b  of the guide body  57  and side walls, one of which is shown at  68 . The side walls may constitute an integral, one-piece part of either the forward guide body portion  57   a  or the rearward guide body portion  57   b.    
     The guide body  57  of FIG. 12 is completed by the provision of a plunger  69 . Plunger  69  has a main body portion  70  which just nicely fits within chamber  61  and is slidable therein. The main body  70  has a nose portion  71  which extends through opening  62  into drive tract  59 . The difference in size between the nose portion  71  and the main body portion  70  forms abutment surfaces  72  and  73  which cooperate with retainer portions  63  and  64  to determine the depth to which the nose  71  extends into drive track  57 . The nose  71  has an inwardly and downwardly sloping surface  74  which is equivalent to portion  54   d  of spring  54  of FIG.  10 . Nose  71  has a vertical surface  75  equivalent to the portion  54   e  of spring  54  of FIG.  10 . It will be noted that the surface  75  lies adjacent the rear surface  67  of drive track  59 . 
     Plunger  69  has a spring seat portion  76  extending from the opposite side of main body portion  70  as does nose portion  71 . The spring seat  76  has a circular periphery and is adapted to receive the compression spring  77 . One end of compression spring  77  abuts the main body portion  70  of plunger  69 . The other end of compression spring  77  abuts the removable plate  65 . Spring  77  serves to maintain the nose  71  of plunger  69  in the position shown in FIG.  12 . The nose portion  71  is of a width to be just nicely received between the legs of staple  42 . Only one leg  42   c  is shown in FIG.  12 . 
     The forwardmost staple  42  of a stick of staples (not shown) will be located in drive track  59  by the staple advancing mechanism of magazine  6 . The tool driver (not shown) will strip the forwardmost staple from its stick and will drive the staple downwardly within drive track  59 . As the staple approaches the bottom of drive track  59 , its legs will straddle plunger nose  71 . The nose  71  will be located between the legs at the time the staple is at the bottommost end of the drive track and in contact with the steel workpieces to be joined. As the driver drives the staple legs through the workpieces, it will be prevented from buckling by the forward surface  66  of the drive track, the rearward surface  67  of the drive track, and the drive track sides, one of which is shown at  68 . The legs cannot buckle toward each other due to the presence therebetween of the plunger nose  71 . Immediately after the penetration of the steel workpieces by the staple legs, the crown  42   a  of the staple will engage nose surface  74 . Nose surface  74  acts as a cam surface which cooperates with the staple crown and the staple driver to shift the nose portion out of drive track  59  and into its retracted position illustrated in FIG. 13, wherein like parts have been given like index numerals. Once the staple  42  is fully driven and clinched with respect to the workpieces, the driver will return to its retracted position allowing the plunger nose  71  to regain the position shown in FIG. 12, by virtue of compression spring  77 . Thus, when a staple is fully driven and clinched, the tool will be immediately ready for the next staple driving cycle. 
     Modifications may be made in the invention without departing from the spirit of it. For example, details of the present invention may be applied to electric staple driving tools, as well as pneumatic staple driving tools. The prior art has devised a number of electric staple driving tools employing a solenoid as the driving force, or a flywheel. In such an instance, it would be within the scope of the invention to consider element  16  of FIG. 1 a solenoid, and element  35  an electric switch to energize said solenoid. The electric switch, itself, may be switched between an “on” state and an “off” state by one of the safety and the manual trigger.