Abstract:
A portable device for inserting fixing elements into predefined seats in a work piece, the portable device including a drive head; a drive rod extending downward from the drive head; a hollow nose piece slidably fit around a lower end of the drive rod, the nose piece being attached to the head and being movable vertically by a predetermined distance with respect to the head and the drive rod; a magazine mounted on the nose piece at a predetermined angle with respect to a lower face of the nose piece for feeding a first fixing element into a horizontal slot on the lower face the nose piece; and a drive mechanism providing a pulsating force produced by a pressurized fluid to an upper end of the drive rod when downward pressure is applied by a user on the drive head. The pulsating force on the drive rod drives the first fixing element into the predefined seat in the work piece.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a multi-blow pneumatic hand tool for inserting t-nuts, and in particular to a multi-blow pneumatic hand tool for inserting t-nuts having prongs.  
         [0003]     2. Description of Background Art  
         [0004]     The first commonly available t-nuts were stamped fasteners with a hollow shaft with an internal thread and a flange without prongs. These t-nuts had holes in the flange (usually three) that could accept small nails that would be used to hold the t-nut to the work piece. Later (late 1930&#39;s or early 1940&#39;s) t-nuts were introduced with prongs that were formed from the flange. These t-nuts would be located over the hole in a work piece and driven into the work piece with a hammer.  
         [0005]     In the late 1960s, an “auto-sta” octagonal flange 4-prong t-nut, designed to feed in a track of a machine, and a t-nut machine to drive these t-nuts into the work piece, was developed. Today while a significant percentage of t-nuts are inserted using machinery, a substantial market remains where t-nuts are driven into a work piece by hand using a hammer. Specific areas where t-nuts are inserted with a hammer are:  
         [0006]     Small Volume User: Traditional t-nut machines are generally only cost effective when the volume of t-nuts exceeds 50,000, for example.  
         [0007]     Assembly Line Insertion: Some companies believe it to be more cost effective to insert t-nuts on the line while the frame is being assembled.  
         [0008]     T-nuts in Large Work Pieces: Large work pieces are difficult to handle. In modern furniture production, frames are typically cut from large plywood sheets. When the components are large they can be too big and awkward to manipulate into a t-nut insertion machine.  
         [0009]     Work Pieces with Blind Holes: In some applications t-nuts are inserted in a blind hole, such as when used to mount a leveler on a chair leg.  
         [0010]     More recently, a pneumatically operated hand tool for inserting t-nuts has been introduced. This device has a magazine that accepts t-nuts that are collated into strips with a flexible adhesive tape, and uses a pneumatic stapler body with a reversed action. When the tool is at rest, the driver is fully extended in the down position and the tip of the driver sticks out the bottom of the nose piece. To operate the tool, the tip of the driver is first placed in the hole. Pressing down on the tool then releases the trigger safety. Squeezing the trigger initiates the following sequence: (1) The driver retracts, a t-nut is advanced into the nose of the tool by a feeder mounted on the magazine; and (2) When the trigger is released, the driver descends, driving the t-nut into the work piece.  
         [0011]     While the concept of this pneumatically operated hand tool provides some improvement, the tool disclosed therein requires a careful technique during use to ensure that the t-nut is set into the hole properly. A problem often occurs because the driver is used to locate the hole, and squeezing of the trigger retracts the driver. The recoil of that action often causes the tool to move slightly. As a result, the t-nut is very often driven into the side of the hole, making it very difficult to start a screw in the t-nut. By holding the tool a certain way, it is possible to compensate for the recoil and to drive t-nuts properly, but for many users and environments it has never worked satisfactorily. A further problem with conventional single-shot hand tools is that they typically require a secondary safety to prevent injury. Even with a secondary safety, conventional single-shot tool cannot completely eliminate the risk of injury to the operator. As a result of these problems, these single-shot devices such as this have not gained wide acceptance in the market.  
       SUMMARY OF THE INVENTION  
       [0012]     According to a one feature consistent with some embodiments of the present invention, a portable device for inserting fixing elements into predefined seats in a work piece is provided. The portable device including a drive head; a drive rod extending downward from the drive head; a hollow nose piece slidably fit around a lower end of the drive rod, the nose piece being attached to the head and being movable vertically by a predetermined distance with respect to the head and the drive rod; a magazine mounted on the nose piece at a predetermined angle with respect to a lower face of the nose piece for feeding a first fixing element into a horizontal slot on the lower face the nose piece; and a drive mechanism providing a pulsating force produced by a pressurized fluid to an upper end of the drive rod when downward pressure is applied by a user on the drive head. The pulsating force on the drive rod drives the first fixing element into the predefined seat in the work piece.  
         [0013]     According to another feature consistent with some embodiments of the present invention, the slot of the nose piece is arranged such that the first fixing element is disposed under a lower face of the drive rod and such that a part of the fixing element in the slot projects below the lower face of the nose piece, the projecting part of the first fixing element for locating one of the predefined seats into which the first fixing element is to be inserted.  
         [0014]     According to still another feature consistent with some embodiments of the present invention a method for determining multiple predefined seat locations in a work piece and inserting fixing elements into the seats is provided including automatically transferring a first fixing element into a nose piece of a multi-blow pneumatic hand tool, a barrel tip of the fixing element extending below a lower face of the nose piece, moving the nose piece over the work piece until the barrel tip of the first fixing element meets a first predefined seat; inserting the first fixing element into the first seat by applying pressure on the nose piece; automatically transferring a second fixing element from the magazine into the nose piece, a barrel tip of the second fixing element extending below the lower face of the nose piece; moving the nose piece over the work piece until the barrel tip of the second fixing element meets a second predefined seat; inserting the second fixing element into the second seat by applying the pressure on the nose piece; and repeating the steps above until the multiple predefined seat locations are found and filled with the fixing elements.  
         [0015]     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0017]      FIG. 1  is a line drawing of a multi-blow t-nut hand tool consistent with some embodiments of the present invention;  
         [0018]      FIG. 2  is a profile view of the multi-blow t-nut hand tool showing a finger hook of the magazine follower consistent with some embodiments of the present invention;  
         [0019]      FIG. 3  is an exploded drawing of nose and driver assembly of hand tool of the embodiment;  
         [0020]     FIGS.  4 ( a ) to  4 ( g ) illustrate views of an exemplary individual t-nut and a t-nut strip;  
         [0021]     FIGS.  5 ( a ) to  5 ( g ) are cut-away views showing an exemplary sequence of locating a hole and inserting a t-nut;  
         [0022]     FIGS.  6 ( a ) to  6 ( f ) are additional views of a nose piece consistent with some embodiments of the present invention;  
         [0023]      FIG. 7  is an exploded view of the cap, sleeve valve, cylinder cap, piston and drive rod of the hand tool consistent with some embodiments of the present invention;  
         [0024]     FIGS.  8 ( a ) and  8 ( b ) are 3-d views of the nose piece assembly of an alternative embodiment of the present invention;  
         [0025]     FIGS.  9 ( a ) to  9 ( c ) illustrate the functioning of the L-shaped fingers of the alternative embodiment shown in FIGS.  8 ( a ) and  8 ( b );  
         [0026]     FIGS.  10 ( a ) and  10 ( b ) provide exterior 3-d views of the nose piece assembly with an adjustable upper stop and a lower contact element consistent with some embodiments of the present invention,  FIG. 10 ( c ) provides a side view of the nose piece assembly with an adjustable upper stop and a lower contact element, and  FIG. 10 ( d ) provides a 3-d view of the lower contact element;  
         [0027]     FIGS.  11 ( a ) and  11  ( b ) are cutaway views of the nose piece assembly with the adjustable upper stop and lower contact element shown in FIGS.  10 ( a ) to  10 ( d ); and  
         [0028]     FIGS.  12 ( a ),  12 ( b ), and  12 ( c ) provide two exterior 3-d views and a side view of the nose piece assembly having a combination lower contact element and upper stop consistent with some embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0029]     The multi-blow pneumatic hand tool for inserting t-nuts consistent with some embodiments of the present invention of the present invention is described with reference to  FIGS. 1-3 .  
         [0030]     As can be seen, the multi-blow pneumatic hand tool  10  for inserting t-nuts  100  has a nose piece and magazine combination (nose piece  50 , angled magazine  60 ), the combination being slidingly attached to a multi-blow pneumatic drive head  12  and a butt  13  of the casing  14  of the multi-blow t-nut hand tool  10 . The magazine and nose piece combination and multi-blow pneumatic drive head  12  are described below.  
         [0031]     Magazine holding bracket  16  is slidably mounted on shaft  15  that extends downward from butt end  13  of the handle  12 . Magazine holding bracket  16  is also fastened to the magazine  60  by fasteners  16   s . Since a front end  60   e  of the magazine  60  is rigidly attached to the nose piece  50  and a rear end of the magazine  60  is attached to bracket  16 , the magazine  60  moves up and down together with movement of the nose piece  50 . The magazine  60  has a slot  60   s  for receiving a strip  150  of collated t-nuts  100  and a spring-loaded follower (not shown) that presses the strip  150  towards the nose piece  50 , advancing one of the t-nuts  100  in the strip  150  into the nose piece  50  after every insertion. In  FIG. 2 , the follower (not shown) includes a finger hook  60   f  that is used to pull the follower back against the force of the magazine spring during the process of loading a strip  150  of multiple t-nuts  100 . When pushed from the magazine  60  into the nose piece  50 , the orientation of the t-nut  100  changes from an angle in the range of 20° to 45° with respect to horizontal. A magnet  50   m  positioned in the front of the nose piece  50  draws the t-nut  100  into a horizontal position in the nose piece  50 .  
         [0032]     The multi-blow pneumatic drive head  12  of the present invention is based on a conventional “palm nailer”. A palm nailer is a tool that can be used to drive nails right up to large spikes without using a hammer. When connected to compressed air, a palm nailer responds to pressure against the driver. As long as pressure is applied, the palm continues to cycle, delivering blow after blow. As soon as pressure is removed, the driving stops. On the t-nut hand tool  10  of the present invention, the multi-blow drive head  12  may feature a cap  21   c  and an ergonomic handle  11  for user convenience and ease of use. In contrast to a conventional palm nailer, which uses a driver that is usually a short round rod that barely protrudes from the base of the tool, the t-nut hand tool  10  of the present invention uses a long drive rod  20  with a large diameter tip.  
         [0033]     In the multi-blow pneumatic hand tool for inserting t-nuts  100 , the magazine/nose piece combination is attached to the drive head  12  in such a way that the magazine  60  and nose piece  50  may slide up and down along an extension tube  30  which is mounted by screws  30   s  on the bottom of the drive head  12 . A mechanism prevents the nose piece/magazine from falling off the extension tube  30 . In some embodiments, the mechanism may include a vertical slot  57  machined into a side of the nose piece  50  through which a screw  50   s  is fastened to the extension tube  30 . The nose piece  50  is able to slide up and down the extension tube  30  only over the length of the slot  57 . One or more springs  40  may be fitted between the nose piece  50  and the drive head  12 , in order to bias the nose piece  50  away from the drive head  12 .  
         [0034]     FIGS.  4 ( a ) to  4 ( h ) provide views of an exemplary individual t-nut  100  and a t-nut strip  150 . FIGS.  4 ( a ) and  4 ( b ) shown perspective views on an individual t-nut  100 . As can be seen, the t-nut  100  includes a barrel  130 , flange  110  and multiple prongs P 1  to P 4 . FIGS.  4 ( c ) to  4 ( h ) show a strip  150  oft-nuts  100  collated and held in place by a strip of tape  100 T. FIGS.  4 ( c ) and  4 ( e ) are side views,  FIG. 4 ( d ) is a plan view,  FIG. 4 ( f ) is an end view, and FIGS.  4 ( g ) and ( h ) are perspective views of the strip  150  of t-nuts  100 . The multi-blow pneumatic hand tool of the present invention may accommodate t-nuts having various base sizes, for example, a small base: 0.625″×0.700″, a large base: 0.830″×0.885″, or other sizes smaller or greater than these.  
         [0035]     The tape  100 T is formed with adhesive on the side applied to the bottom of the t-nuts  100 . Any commonly known material may be used for the adhesive tape  100 T. Once the t-nuts  100  are collated into a strip  150 , the strip  150  is ready to be inserted into the magazine  60 .  
         [0036]     Referring to FIGS.  5 ( a ) to  5 ( g ), the multi-blow pneumatic drive head  12  will be described. FIGS.  5 ( a ) to  5 ( g ) also show a sequence of using the hand tool  10  for locating a hole  210  in the work piece  200  and inserting a t-nut  100  into the hole  210 .  
         [0037]     As shown, the multi-blow pneumatic drive head  12  is provided with a cylinder  129 . A drive piston  88  is slidably disposed in the cylinder  129  and fixed to the top of drive rod  20  for cycling the drive rod  20  upward and downward under the influence of bursts of compressed air from air supply passage  118  alternately supplied to air chamber  156  below the piston  88 , and air chamber  144  above the piston  88 . Bursts of compressed air alternately enter air chamber  144  or air chamber  156 , depending on the position of sleeve valve  114 .  
         [0038]     In  FIG. 5 ( a ) the hand tool  10  is in a rest position, above the work piece  200 , and there is a gap between the bottom end of the drive rod  20  and the flange  110  of the t-nut  100  that is positioned in the nose piece  50 . In  FIG. 5 ( a ) tip of the barrel  130  of the t-nut is not yet inserted into the hole  210 . Piston  88  is in a rest position against the bottom of the cylinder  129 , thus blocking entry of compressed air in supply passage  118  from entering into air chamber  156  through ports  131 ,  136 . Further, sleeve valve  114  is in an up position, thus preventing compressed air from leaving air supply passage  118  and entering air chamber  144  through port  138 .  
         [0039]     In  FIG. 5 ( b ), the drive cycle of the hand tool  10  is triggered when the hand tool is pressed down on the flange  110  of the t-nut  100 . As the drive cycle continues, the tip of the t-nut barrel  130  is partially inserted into hole  210 . The upward pressure on the drive rod  20  pushes piston  88  upward and allowing air to flow into air chamber  156 .  FIG. 5 ( c ) illustrates an upward stroke of the drive rod  20  during the cycling of the drive rod  20 .  
         [0040]      FIG. 5 ( d ) illustrates the sleeve valve  114  moved away from port  138 , and a drive stroke initiated by a burst of compressed air that now enters upper air chamber  144  through port  138 . In  FIG. 5 ( e ), the drive stoke of the drive rod  20  moves to completion, port  138  is closed by the sleeve valve  114 , and simultaneously ports  131 ,  136  are closed off by the piston  88 .  FIG. 5 ( e ) also shows that the prongs P 1 -P 4  of the t-nut  100  partially inserted into the work piece  200 .  
         [0041]      FIG. 5 ( f ) illustrates the cycle finished, the sleeve valve  114  reset, and ready for the next cycle.  FIG. 5 ( g ) illustrates the t-nut  100  is fully inserted into the hole  210  and the cycling being stopped. The top of the nose piece  50  is pressed upward against the downward pressure of the spring(s)  40  to make contact with the flange  30   f  of the extension tube  30 , and the drive rod  20  is fully extended. The repetitive driving blows of the hand tool  10  stop when the t-nut  100  is not pressing up on the drive rod  20 , and no matter how much downward force the operator applies to the tool  10  the t-nut  100  cannot be driven further into the work piece  200 .  
         [0042]     Next, operation of hand-tool is described with reference to FIGS.  5 ( a ) to  5 ( g ). First, an operator loads a strip  150  oft-nuts  100  into the magazine  60  of the hand tool  10 . The spring loaded follower (not shown) pushes on the distal end of the strip  150 , bringing the first t-nut  100  into position in the nose piece  50 . Magnet  50   m  holds the t-nut  100  in place in slot  52  (see FIGS.  6 ( a ) to  6 ( f )). The barrel  130  of this t-nut  100  protrudes downward below the magazine  60  and the barrels of the other t-nuts  100  in the strip  150 . The operator then locates the tip of the barrel  130  of the first t-nut  100  into the hole  210  in the work piece  200 . The operator then presses down on the drive head  12  of the hand tool  10 , the drive head  12  moves downward against the spring pressure (of spring(s)  40 ) towards the nose piece  50  and magazine  60 .  
         [0043]     The operator continues pressing down until the tip of the drive rod  20  contacts the t-nut  100  in the nose piece  50 . The drive head  12  then cycles continuously as the operator maintains downward pressure, driving the prongs P 1 -P 4  of the t-nut  100  into the work piece  200  and breaking the tape  100 T that connects t-nut  100  to the remaining t-nuts in the collated strip. Since the drive rod  20  has a relatively short stroke and produces a low impact, the hand tool is inherently safe, with virtually no risk of injury. Further, as compared to a single blow hand tool, the multi-blow pneumatic hand tool  10  needs to deliver only a small amount of power in each of the multiple blows in order to insert each t-nut  100 . When the t-nut  100  is completely driven into the work piece  200 , the operator stops applying downward pressure and the drive head  12  stops cycling. The operator then lifts the hand tool  10  off the work piece  200 , the spring(s)  40  push the drive head  12  and the magazine  60  apart. When the nose piece  50  and magazine  60  are fully extended, the follower is able to push the next t-nut  100  into position in the nose piece  50  and the hand tool  10  in ready to insert the next t-nut  100  into the next hole.  
         [0044]     In some applications, foam may be injected around a wood or plastic work piece  200  after the t-nut  100  is inserted. In these cases, it is common for the flange  110  of the t-nut  100  to be covered with a tape in order to prevent foam from reaching the threads inside the t-nut  100 . Since the multi-blow pneumatic hand tool  10  for inserting t-nuts  100  of the present invention locates the hole  210  in the work piece  200  by actually placing the t-nut  100  in the hole  210 , the need in conventional devices or machines for a separate device to carry the t-nut  100  from the track or magazine to the hole can be eliminated. For this reason, the drive rod  20  of the hand tool  10  of the present invention has only a small locating nib  20   n  (hemispherically-shaped), as opposed to the long guide pin, typically found in conventional devices. If a flexible tape  100 T is used to collate the t-nut strips  150 , the nib  20   n  does not pierce the tape  100 T, leaving it intact on the flange  110  of the t-nut  100 . This can eliminate the need for a secondary taping operation for applications involving injected foam.  
         [0045]     FIGS.  6 ( a ) to  6 ( d ) include a perspective view, a side view, a bottom view, and a plan view, respectively, of nose piece  50 .  FIG. 6 ( e ) is a sectional view taken along line A-A of  FIG. 6 ( d ), and  FIG. 6 ( f ) is a sectional view taken along line B-B of  FIG. 6 ( d ). Note particularly that when the t-nut  100  is in position in the nose piece  50 , it is constrained by the slot  52  from moving upwardly by a roof  52   f  of the slot  52 , or from moving laterally by side walls  52   a ,  52   b ,  52   c  of the slot  52 . FIGS.  6 ( a ) to  6 ( f ) also show central bore  53 , one or more spring holes  54  for accommodating spring(s)  40 , vertical slot  57 , notch  50   n  for accommodating a front end  60   e  of the magazine  60 , screw hole  55  for accommodating screw  60   s  and rigidly attaching the front end  60   e  of magazine  60  to the nose piece  50 , spring holes  54 , bottom face  50   f  of the nose piece  50 , and bore  56  for insertion of a magnet  50   m  into the nose piece  50 .  
         [0046]      FIG. 7  is an exploded view of the cap  12 , sleeve valve  114 , cylinder cap  102  with ports  136  and  138 , piston  88 , and drive rod  20  of the multi-blow pneumatic hand tool  10  of one embodiment of the invention.  
         [0047]     FIGS.  8 ( a ) and  8 ( b ), and FIGS.  9 ( a ) to  9 ( c ), are exemplary illustrations of an alternative embodiment of the present invention. FIGS.  8 ( a ) and  8 ( b ) are 3-d views of the nose piece  50  assembly from the exterior. Whereas the embodiments described above used a magnet  50   m  to retain the t-nuts  100  in the nose piece  50 , this alternative embodiment employs L-shaped fingers  59  attached to the nose piece  50  to retain the t-nut  100  in the nose piece  50 . Further, the magnet  50   m  may also be used in conjunction with the L-shaped fingers  59 . The L-shaped fingers  59  in this embodiment are made of flexible spring strips, such as a flexible steel material, or other flexible material, and are attached to the nose piece  50  by means of fasteners  58 .  
         [0048]     FIGS.  9 ( a ) to  9 ( c ) illustrate the functioning of the L-shaped fingers  59  showing the cutaway drawings of the nose piece  50  during three successive stages of insertion.  
         [0049]      FIG. 9 ( a ) illustrates the t-nut barrel  130  (slightly inserted into the hole  210 ) prior to insertion of the prongs P 1 -P 4  into the work piece  200 . The L-shaped fingers  59  can be seen retaining the flange  110  of the t-nut  100  in the nose piece  50 .  
         [0050]      FIG. 9 ( b ) illustrates shows the t-nut  100  is being pushed past the L-shaped fingers  59 , the fingers being forced open to allow the flanges  110  of the t-nut  100  to pass.  
         [0051]     In  FIG. 9 ( c ) the insertion of t-nut  100  is complete. The t-nut  100  is fully inserted into the work piece  200 , and the drive rod  20  in a fully extended position.  
         [0052]     Next, referring to FIGS.  10 ( a ) to  10 ( d ),  11 ( a ),  11 ( b ), and  12 ( a ) to  12 ( c ), additional features of the invention will be described. These FIGS. illustrate exemplary means for (1) adjusting the stoke of the nose piece/magazine assembly, and for (2) adapting the tool to accommodate t-nuts having barrels of different heights. Note that to improve clarity, the spring(s)  40  between the nose piece  50  and the extension tube  30  (shown earlier in  FIGS. 1 and 3 ) are not shown FIGS.  10 ( a ) to  10 ( d ),  11 ( a ),  11 ( b ), and  12 ( a ) to  12 ( c ).  
         [0053]     FIGS.  10 ( a ) and  10 ( b ) provide two exterior 3-d views of nose piece assembly with (1) an exemplary adjustable upper stop  50 U to control the range of movement of the nose piece/magazine on the extension tube  30  that is mounted to the housing of the drive head  12 , and (2) an exemplary lower contact element  50 D.  FIG. 10 ( c ) is a side view of the nose piece assembly with the adjustable upper stop  50 U and the lower contact element  50 D.  FIG. 10 ( d ) is a 3-d view of the lower contact element  50 D. the  
         [0054]     Adjustable upper stop  50 U and lower contact element  50 D are used to control the depth to which the t-nut  100  is driven (for example, if the user would like the upper surface of the flange  110  of the t-nut  100  driven flush with the work piece  200 , or to have the flange  110  remain above the surface of the work piece  200 ) and also to configure the hand tool  10  to work with t-nuts  100  having barrels  130  with different lengths. Common t-nuts have barrel lengths in the range of ¼″ to ⅝″. However, the hand tool  10  of the present invention may be configured to accommodate t-nuts with barrel lengths in the range of 3/16″ to ⅞″, or lengths outside this range.  
         [0055]     The adjustable upper stop  50 U is generally rectangular in shape and may be formed with a side slot for adjusting upper slot  50 U up and down by the length of the slot against the side of the nose piece  50 . The adjustable upper stop  50 U may be held in place by one or more screws  58 .  
         [0056]     As can be seen in  FIG. 10 ( d ), the lower contact element  50 D generally is an L-shaped element  50 D, and includes a lower portion  50 L which extends under the lower face  50   f  of the nose piece  50 . As such, the lower portion  50 L of the lower contact element  50 D extends the length of the nose piece  50 , enabling the nose piece  50  to accommodate t-nuts having barrels  130  of different lengths. The lower portion  50 L of the lower contact element  50 D is formed a slot  52 ′, the slot  52 ′ having sides walls  52   a ′,  52   b ′, and  52   c ′. Slot  52 ′ of lower contact element  50 D has lateral dimensions substantially equal to those of slot  52  of the nose piece  50 . The lower portion  50 L of the lower contact member  50 D has a predetermined thickness t, the thickness t being set to accommodate t-nuts  100  having barrels  130  of different lengths. As with the upper stop  50 U, the lower contact member  50 D may be held in place by one or more screws  58 . Optionally, the lower contact element  50 D may be provided with a side slot (not shown) to allow for up and down adjustment.  
         [0057]     FIGS.  11 ( a ) and  11  ( b ) are cutaway views of a nose piece assembly with the exemplary adjustable upper stop  50 U and lower contact element  50 D, configured for a t-nut  100  with a longer barrel  130 .  
         [0058]      FIG. 11 ( a ) illustrates the lower contact element  50 D attached to the nose piece  50 , so that the lower face  50   f ′ of the lower contact element  50 D is flush with the lowest part of the first t-nut  100  in the magazine  60  (not the t-nut  100  in the nose piece  50 , as shown in  FIG. 11 ( b )). When the operator locates the hole  210  in the work piece  200  with the end of the barrel  130  of the t-nut  100  in the nose piece and presses down on the hand tool  10 , the pressure is applied to the lower contact element  50 D, and not the t-nut  100  in the magazine  60 .  FIG. 11 ( b ) illustrates the setting of the upper stop  50 U, which prevents further downward movement of the drive head  12  once the t-nut  100  in the nose piece has been inserted to the desired depth into the work piece  200 .  
         [0059]     FIGS.  12 ( a ),  12 ( b ), and  12 ( c ) provide two exterior 3-d views and a side view of the nose piece assembly with an exemplary combination contact element and upper stop  50 DU. As can be seen, the combination lower contact element and upper stop  50 DU has a lower portion  50 L″ which extends under the lower face  50   f  of the nose piece  50 . As such, the combination lower contact element and upper stop  50 DU extends the length of the nose piece  50 , enabling the nose piece  50  to accommodate t-nuts having barrels  130  of different lengths. The lower portion  50 L″ of the combination lower contact element and upper stop  50 DU is formed a slot  52 ″, the slot  52 ″ having sides walls  52   a ″,  52   b ″, and  52   c ″. Slot  52 ″ of the combination lower contact element and upper stop  50 DU has lateral dimensions substantially equal to those of slot  52  of the nose piece  50 . The lower portion  50 L″ of the combination lower contact member and upper stop  50 DU has a predetermined thickness t″, the thickness t″ being set to accommodate t-nuts  100  having barrels  130  of different lengths.  
         [0060]     In a manner similar to that shown in  FIG. 11 ( a ), and as can be seen in  FIG. 12 ( c ), the lower face  56   f ″ of the lower portion  50 L″ of the combination lower contact element and upper stop  50 DU is flush with the lowest part of the first t-nut  100  in the magazine  60  (not the t-nut  100  in the nose piece  50 ). When the operator locates the hole  210  in the work piece  200  with the end of the barrel  130  of the t-nut  100  and presses down on the hand tool  10 , the pressure is applied to the combination lower contact element and upper stop  5 )DU, and not the t-nut  100  in the magazine  60 .  
         [0061]     Additional alternative embodiments may include one or more of the following features.  
         [0062]     The multi-blow pneumatic hand tool of the present invention may be adapted to accommodate a wide variety of t-nuts, including t-nuts having different base widths and barrel lengths, and t-nuts with and without prongs. Also, t-nuts with any number of prongs may be accommodated. Further, the front end  60   e  of magazine  60  may be attached to the nose piece  50  by means other than screw  60   s . In addition, magazines and t-nut feeding devices of various sizes and shapes may be attached to the nose piece  50 . These magazines and t-nut feeding devices may accommodate strips of 15, 20, 50 or 100, or more t-nuts, depending on the base size of the t-nut and the particular magazine or t-nut feeding device used. Still further, while three springs  40  are shown in the nose piece  50 , one, two, or four springs may be used instead.  
         [0063]     Also, while slot  57  and screw  50   s  are used for limiting the up and down movement of the nose piece  50 , other mechanisms may be used. Further, while the L-shaped fingers  59  are shown separately from the adjustable upper stopper  50 U, L-shaped lower contact element  50 D, and the combination lower contact element and upper stop  50  DU, the L-shaped fingers  59  are compatible with any of the components  50 U,  50 D, and  50 DU.  
         [0064]     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.