Patent Publication Number: US-2022234184-A1

Title: Pneumatic fastener driver

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 17/403,974 filed on Aug. 17, 2021, which is a continuation of U.S. patent application Ser. No. 16/193,277 filed on Nov. 16, 2018, now U.S. Pat. No. 11,110,577, which claims priority to U.S. Provisional Patent Application No. 62/586,972 filed on Nov. 16, 2017 and U.S. Provisional Patent Application No. 62/590,687 filed on Nov. 27, 2017, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to pneumatic fastener drivers. 
     BACKGROUND OF THE INVENTION 
     There are various fastener drivers known in the art for driving fasteners (e.g., nails, tacks, staples, etc.) into a workpiece. These fastener drivers operate utilizing various means known in the art (e.g., compressed air generated by an air compressor, electrical energy, a flywheel mechanism, etc.), but often these designs are met with power, size, and cost constraints. 
     SUMMARY OF THE INVENTION 
     The present invention provides, in one aspect, a fastener driver including a housing having a handle portion. A motor is positioned within the housing. The fastener driver further includes an air compressor including a compressor cylinder and a compressor piston movable within the compressor cylinder in a reciprocating manner to compress air within the compressor cylinder. The fastener driver further includes a drive train converting torque from the motor to a linear force applied to the compressor piston, causing the compressor piston to move in the reciprocating manner. At least a portion of the drive train extends through the handle portion of the housing. 
     The present invention provides, in another aspect, a fastener driver including a housing having a head portion, a battery attachment portion, and a handle portion extending therebetween. A motor is positioned within the battery attachment portion. A battery pack is coupled to the battery attachment portion for providing power to the motor. The fastener driver further includes an air compressor including a compressor cylinder and a compressor piston movable within the compressor cylinder in a reciprocating manner to compress air within the compressor cylinder. The fastener driver further includes a drive train converting torque from the motor to a linear force applied to the compressor piston, causing the compressor piston to move in the reciprocating manner. The drive train includes a drive shaft extending through the handle portion. 
     The present invention provides, in yet another aspect, a fastener driver including a housing, and a motor positioned within the housing. The fastener driver further includes an air compressor including a compressor cylinder, a head coupled to the compressor cylinder, and a compressor piston movable within the compressor cylinder in a reciprocating manner by the motor to compress air within the compressor cylinder. A drive cylinder is in selective fluid communication with the compressor cylinder. The drive cylinder extends between a first end and a second end. A drive piston is slidably disposed in the drive cylinder. The drive piston has a drive blade attached thereto. A valve is positioned between the head and the first end of the drive cylinder. The valve is movable between an open position, in which the drive cylinder is in fluid communication with the compressor cylinder, and a closed position. A spring biases the valve toward the first end into the closed position. The valve includes a flange having a first side in facing relationship with the first end of the drive cylinder, and an opposite second side. A surface area of the second side of the flange exposed to the compressed air within the compressor cylinder is greater than a surface area of the first side of the flange exposed to the compressed air within the compressor cylinder, thereby maintaining the valve in the closed position. 
     The present invention provides, in still yet another aspect, a fastener driver including a housing having a handle portion. A trigger mechanism is mounted on the handle portion. The trigger mechanism includes a first trigger for initiating a fastener driving operation and a second trigger. Each trigger is movable between a first position and a second position. A circuit board is positioned within the handle portion. The circuit board includes a first switch configured to be actuated by the first trigger when moving from the first position to the second position, and a second switch configured to be actuated by the second trigger. The second trigger, when in the first position, blocks movement of the first trigger from the first position to the second position 
     The present invention provides, in another aspect, a fastener driver including a housing having a handle portion. A trigger is mounted to the handle portion. A magazine is coupled to the housing and configured to receive fasteners. The fastener driver further includes a nosepiece through which consecutive fasteners from the magazine are driven. The fastener driver further includes a dry-fire lockout mechanism having a latch pivotably coupled to the magazine, and a link is coupled to the trigger for movement with the trigger. The latch is pivotable between a first position, in which the latch is disengaged from the link, and a second position, in which the latch is engaged with the link and inhibits movement of the link, and therefore the trigger, in response to the trigger being depressed. The latch moves from the first position to the second position in response to a number of fasteners remaining in the magazine being less than a predetermined value. 
     The present invention provides, in yet another aspect, a fastener driver including a housing, a drive cylinder positioned in the housing, and a drive piston slidably disposed in the drive cylinder from a first position to a second position during a fastener driving operation. The drive piston has a drive blade attached thereto. A magazine is coupled to the housing and is configured to receive a collated strip of fasteners. The magazine includes a pusher positioned for biasing the collated strip of fasteners toward a first end of the magazine, and a base in which the pusher is supported. The base defines a plurality of slots. A cover is attachable to the base. The cover defines a continuous channel in facing relationship with the slots. The channel includes a back wall. A plurality of pins is slidably positioned in the magazine for movement with the pusher. Each pin is received within a respective slot, and each pin has an end extending into the channel from the slot. Each slot includes a slanted portion oriented at an oblique angle with respect to the back wall such that the end of each pin is positioned at the oblique angle relative to the back wall. 
     The present invention provides, in yet another aspect, a power tool including a housing that has a handle portion and a trigger mechanism mounted on the handle portion. The trigger mechanism includes a first trigger for initiating an operation and a second trigger, each of the first and second triggers being movable between a first position and a second position. The second trigger, when in the first position, blocks movement of the first trigger from the first position to the second position. 
     The present invention provides, in yet another aspect, a power tool including a housing that has a handle portion and a trigger mechanism mounted on the handle portion. The trigger mechanism includes a first trigger for initiating an operation and a second trigger, each of the first and second triggers being movable between a first position and a second position. The second trigger is movable from the first position to the second position before the first trigger is movable from the first position to the second position 
     The present inventio provides, in yet another aspect, a power tool including a housing including a handle portion, and a trigger mechanism mounted on the handle portion. The trigger mechanism includes a first trigger for initiating an operation and a second trigger, each of the first and second triggers being movable between a first position and a second position. The first trigger includes a first surface that is accessible to the user for actuating the first trigger and a second surface opposite the actuation surface. The second trigger includes a first surface that is accessible to the user for actuating the second trigger and a second surface. When the second trigger is in the first position, the second surface of the second trigger engages the second surface of the first trigger such that movement of the first trigger from the first position to the second position is blocked. When the second trigger is in the second position, the second surface of the second trigger is spaced apart from the second surface of the first trigger such that movement of the first trigger from the first position to the second position is permitted. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a pneumatic fastener driver. 
         FIG. 2  is a side cross-sectional view of the pneumatic fastener driver of  FIG. 1  taken along line  2 - 2  in  FIG. 1 , illustrating a compressor  30  and a motor  54 . 
         FIG. 3A  an enlarged, partial cross-sectional view illustrating the compressor  30  of the pneumatic fastener driver of  FIG. 2 . 
         FIG. 3B  is another enlarged, partial cross-sectional view illustrating a compressor piston in a bottom-dead-center position, a drive piston in a top-dead-center position, and a valve of the compressor in a closed position. 
         FIG. 3C  is yet another enlarged, partial cross-sectional view illustrating the compressor piston near a top-dead-center position as the drive piston remains in the top-dead-center position of  FIG. 3B . 
         FIG. 3D  is yet still another enlarged, partial cross-sectional view illustrating the valve in an open position and the compressor piston in the top-dead-center positon. 
         FIG. 3E  is another enlarged, partial cross-sectional view illustrating the compressor piston just below the top-dead-center position of  FIG. 3D , the drive piston in a bottom-dead-center position, and the valve returned to the closed position of  FIG. 3B . 
         FIG. 3F  is yet another enlarged, partial cross-sectional view illustrating the compressor piston returning to the bottom-dead-center position of  FIG. 3B  and the drive piston returning to the top-dead-center position of  FIG. 3B . 
         FIG. 4A  is an enlarged, partial cross-sectional view of the valve of  FIG. 3B  in the closed position. 
         FIG. 4B  is an enlarged, partial cross-sectional view of the valve of  FIG. 3D  in the open position. 
         FIG. 5A  is an enlarged, partial cross-sectional view of a trigger mechanism of the pneumatic fastener driver of  FIG. 1  in a first position. 
         FIG. 5B  is an enlarged, partial cross-sectional view of the trigger mechanism of  FIG. 5A  in a second position. 
         FIG. 6A  is another perspective view of the pneumatic fastener driver of  FIG. 1 , illustrating a cutaway of a magazine and a rod of the trigger mechanism. 
         FIG. 6B  is an enlarged perspective view of the rod of  FIG. 6A  coupled to the trigger mechanism of  FIGS. 5A-5B . 
         FIG. 6C  is a partial cross-sectional view of the magazine, illustrating a dry-fire lockout mechanism. 
         FIG. 7A  is an enlarged, cross-sectional view of the dry-fire lockout mechanism of  FIG. 6C  including a latch in a non-interfering position relative to the rod. 
         FIG. 7B  is enlarged view of a portion of the dry-fire lockout mechanism of  FIG. 7A . 
         FIG. 7C  is an enlarged, cross-sectional view of the latch of  FIG. 7A  in an interfering position relative to the rod. 
         FIG. 7D  is enlarged view of a portion of the dry-fire lockout mechanism of  FIG. 7C . 
         FIG. 8A  is another enlarged, partial cross-sectional view of the latch in the non-interfering positon. 
         FIG. 8B  is yet another enlarged, partial cross-sectional view of the latch in the non-interfering positon. 
         FIG. 9A  is another enlarged, partial cross-sectional view of the latch in the interfering positon. 
         FIG. 9B  is yet another enlarged, partial cross-sectional view of the latch in the interfering positon. 
         FIG. 10  is an enlarged, partial cross-sectional of the magazine of  FIG. 6A , illustrating pusher pins within respective slots. 
     
    
    
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a pneumatic fastener driver  10  is operable to drive fasteners  164  ( FIG. 6A ) (e.g., nails, tacks, staples, etc.) held within a magazine  14  into a workpiece. The pneumatic fastener driver  10  includes an outer housing  18  with a handle portion  22 , and a user-actuated trigger  26  mounted on the handle portion  22 . The pneumatic fastener driver  10  does not require an external source of air pressure, but rather includes an on-board air compressor  30  ( FIG. 2 ) positioned within a head portion  36  the outer housing  18 . The on-board air compressor  30  is powered by a power source (e.g., a battery pack  34 ), coupled to a battery attachment portion  38  of the outer housing  18 . 
     With reference to  FIGS. 2 and 3A-3F , the pneumatic fastener driver  10  includes a drive blade  42  actuated by the on-board air compressor  30  to drive the fasteners  164  into a workpiece. The compressor  30  includes a compressor cylinder  46  and a compressor piston  50  in the compressor cylinder  46  ( FIG. 2 ). The compressor piston  50  is driven in a reciprocating manner by a motor  54  and a drive train  68  interconnecting the motor  54  and the compressor piston  50 . The drive train  68  includes a transmission  58  that receives torque from the motor  54 , a drive shaft  56  connected to the output of the transmission  58 , a gear train  60  driven by the drive shaft  56 , and a crank arm assembly  62  connected to the output of the gear train  60 . The gear train  60  is positioned within the head portion  36  adjacent the compressor cylinder  46 , and includes a first gear  64 A coupled for co-rotation with the drive shaft  56 , a second idler gear  64 B meshed with the first gear  64 A, and a third gear  64 C meshed with the second gear  64 B ( FIG. 2 ). The crank arm assembly  62  includes a crank shaft  63  coupled for co-rotation with the third gear  64 C, a crank arm  65  located on an opposite side of the crank shaft  63 , and a connecting rod  67  pivotably coupling the compressor piston  50  and the crank arm  65 . Each of the transmission  58  and the gear train  60  is configured to reduce a rotational speed of the motor  54 . As such, the transmission  58  may be a first speed reduction mechanism, and the gear train  60  may be a second speed reduction mechanism. 
     With specific reference to  FIG. 2 , the motor  54  is positioned within the battery attachment portion  38  adjacent a first end  44  of the handle portion  22 , with the transmission  58  and the drive shaft  56  extending through the handle portion  22 . The gear train  60  operatively coupled to the drive shaft  56  is positioned proximate a second end  48  of the handle portion  22 . As such, a portion of the drive train  68  (e.g., the transmission  58  and the drive shaft  56 ) is positioned within the handle portion  22 . Furthermore, the transmission  58  or first speed reduction mechanism is positioned upstream of the drive shaft  56 , and the gear train  60  or second speed reduction mechanism is positioned downstream of the drive shaft  56 . In other words, the drive train  68  includes a split gearbox configuration, with speed reduction occurring both upstream of the drive shaft  56  (by the transmission  58 ) and downstream of the drive shaft  56  (by the gear train  60 ). Therefore, this configuration makes the fastener driver  10  more compact than it otherwise would be with all of the speed reduction occurring in a single gearbox. In addition, this configuration allows the user to hold the pneumatic fastener driver  10  at a small distance offset from the workpiece for easy, accurate use of the fastener driver  10 , which results in improved balance and manipulation of the fastener driver  10  during use. 
     The pneumatic fastener driver  10  also includes a drive cylinder  66  in selective fluid communication with the compressor cylinder  46  and a drive piston  70  slidably disposed in the drive cylinder  66 . As shown in  FIG. 3A , the smaller drive cylinder  66  is located inside the larger compressor cylinder  46  for a cylinder-in-a-cylinder configuration. The compressor piston  50  includes a bore  72  through which the drive cylinder  66  extends from a first end  76  to a second end  80 . The drive piston  70  further includes a body  74  and the drive blade  42  extending from the body  74  of the drive piston  70  within the drive cylinder  66 . The drive piston  70  is movable between a top-dead-center position ( FIGS. 3A-3C ) and a bottom-dead-center position ( FIG. 3D and 3E ). Specifically, the drive piston  70  is in the top-dead-center position when at the first end  76  of the drive cylinder  66  and in the bottom-dead-center position when at the second end  80  of the drive cylinder  66 . The drive cylinder  66  includes a cylindrical opening  88  positioned at the second end  80  of the drive cylinder  66  and formed therein to vent excess pressure in the drive cylinder  66  when the drive piston  70  moves towards the bottom-dead-center position. Specifically, the opening  88  is configured to vent air within the drive cylinder  66  and beneath the drive piston  70  during the movement of the drive piston  70  from the top-dead-center position to the bottom-dead-center position. Similarly, the compressor piston  50  is moveable between a bottom-dead-center position ( FIG. 3A and 3B ) and a top-dead-center position ( FIG. 3C-3E ). 
     With continued reference to  FIG. 3A , the compressor cylinder  46  includes an integral head  90  formed at a top end  94  of the compressor cylinder  46  (i.e., the head  90  and the cylinder  46  are formed as a single component). The integral compressor cylinder  46  and cylinder head  90  may be manufactured by, for example, a deep-drawing process or an impact extrusion process. The drive cylinder  66  may also be formed using either of the above-mentioned processes with an integral cylinder head. The illustrated head  90  includes a cover  92  adjacent an end of the head  90 . 
     A hole  106  defined by the head  90  is formed above the drive cylinder  66 . A valve  98  is positioned within the hole  106  and includes a flange  100 . The flange  100  divides the valve  98  into a guide portion  102 , which is positioned within the hole  106 , and a stem portion  104 . The stem portion  104  is positioned within the first end  76  of the drive cylinder  66 . A cylindrical insert  110  is positioned within the drive cylinder  66  at the first end  76 . A gap  112  is defined between the head  90  and the insert  110  in which the flange  100  is located. A spring member  114  is positioned between the cover  92  and the valve  98  within the hole  106 . Specifically, the spring member  114  biases the flange  100  of the valve  98  against the insert  110 . An O-ring  82 A is positioned between the flange  100  and the insert  110 , and an additional O-ring  82 B is positioned between the guide portion  102  and the head  90  within the hole  106 . The O-ring  82 A provides a seal between the compressor cylinder  46  and the drive cylinder  66 , whereas the O-ring  82 B provides a seal between the compressor cylinder  46  and the outside atmosphere. In particular, the cover  92  defines an opening  96  ( FIG. 3A ) in fluid communication with the hole  106  defined by the head  90 . As such, the guide portion  102  of the valve  98  is exposed to the outside atmosphere. In the illustrated embodiment, the O-ring  82 B is positioned between two retaining rings  97 . In addition, the O-ring  82 B and the two retaining rings  97  are positioned between annular flange sections  102 A ( FIG. 4A ) of the guide portion  102 . 
     The insert  110  further includes a plurality of ports  108  positioned at the first end  76  of the drive cylinder  66  and formed therein to vent air from within the drive cylinder  66  to the compressor cylinder  46 . An O-ring  86 , having a circular or non-circular cross-sectional shape, or other sealing member, is positioned around the outer periphery of the insert  110  and surrounding the ports  108 , only two of which are shown in  FIGS. 3A-3F . The O-ring  86  functions as a one-way valve to enable fluid communication between the compressor cylinder  46  and the drive cylinder  66  during return of the compressor piston  50  to the bottom-dead-center position. Likewise, as the compressor piston  50  nears its top-dead-center position, the gap  112  may also fluidly communicate the compressor cylinder  46  and the drive cylinder  66  when the valve  98  is unseated from the O-ring  82 A as described in further detail below. 
     In operation, the compressor piston  50  is driven from the bottom-dead center position to the top-dead-center position ( FIGS. 3B to 3D  in sequence) and the drive piston  70  is driven from the top-dead-center position ( FIG. 3C ) to the bottom-dead-center position ( FIG. 3D ) for driving one of the fasteners  164  into the workpiece. The drive piston  70  is then returned to the top-dead-center position as the compressor piston  50  returns to the bottom-dead-center position (sequence from  FIGS. 3D to 3F , and back to  FIG. 3B ) for preparing the pneumatic fastener driver  10  for a subsequent fastener driving operation. 
     More specifically, at the beginning of a fastener driving operation as shown in  FIG. 3B , the compressor piston  50  is in the bottom-dead-center position, while the drive piston  70  is in the top-dead-center position. When the user of the driver  10  depresses the trigger  26 , the piston  50  is driven upward and toward the top end  94  of the compressor cylinder  46  by the motor  54  and crank arm assembly  62  ( FIG. 3C ). As the compressor piston  50  travels upward, the air in the compressor cylinder  46  above the compressor piston  50  is compressed. The force of the compressed air F 3 A, F 3 B on the valve  98  keeps the valve  98  in a closed (i.e., sealed) position until the compressor piston  50  contacts the valve flange  100 , after which the flange  100  is unseated from the O-ring  82 A by the compressor piston  50  as it reaches its top-dead-center position ( FIG. 3D ), fluidly communicating the first end  76  of the drive cylinder  66  with the compressor cylinder  46  via the gap  112 . As such, the valve  98  is in an open position in which the drive cylinder  66  receives the compressed air from the compressor cylinder  46 . The compressed air also acts upon the drive piston  70  positioned within the drive cylinder  66 . 
     With reference to  FIG. 4A , the valve  98  is maintained in the closed position due to a combination of atmospheric force F  1 , spring force F 2  from the spring member  114 , and the force of the compressed air F 3 A on a first side  122 A of the flange  100 . In particular, the first side  122 A of the flange  100  has a surface area  123 A (i.e., the area exposed to the force of the compressed air F 3  on the first side  122 A). The flange  100  further includes a second side  122 B opposite the first side  122 A upon which the force of the compressed air F 3 B also acts. The second side  122 B is in facing relationship with the first end  76  of the drive cylinder  66  and has a surface area  123 B (i.e., the area exposed to the force F 3 B on the second side  122 B). The surface area  123 B of the second side  122 B of the flange  100  may also include the surface area of the stem portion  104 . When the valve  98  is in the closed position, the surface area  123 A of the first side  122 A of the flange  100  exposed to the compressed air within the compressor cylinder  46  is greater than the surface area  123 B of the second side  122 B of the flange  100  exposed to the compressed air within the compressor cylinder  46 . Therefore, the resulting force of the compressed air F 3 B on the second side  122 B of the flange  100  is less than the resulting force of the compressed air F 3 A acting on the first side  122 A of the flange  100  ( FIG. 4A ), thereby maintaining the valve  98  is the closed position, and preventing the compressed air in the compressor cylinder  46  alone from moving the valve  98  from the closed position to the open position. In addition, the spring force F 2  biasing the valve  98  toward the insert  110 , and the atmospheric force Fl applied to the guide portion  102  of the valve  98  further aids in maintaining the valve  98  in the closed position. 
     The valve  98  moves from the closed position to the open position only when the compressor piston  50  reaches its top-dead-center position and unseats the valve  98 , as shown in  FIGS. 3D and 4B . Subsequently, the compressed air from the compressor cylinder  46  flows into the drive cylinder  66  via the gap  112 . The surface area  123 B of the second side  122 A of the flange  100  exposed to the compressed air within the compressor cylinder  46  is now greater than the surface area  123 A the first side  122 B of the flange  100  exposed to the compressed air within the compressor cylinder  46 . Therefore, the force of the compressed air F 3 B′ on the second side  122 B of the flange  100  is now greater than the combination of the atmospheric force Fl, the spring member force F 2 , and the force of compressed air F 3 A′ on the first side  122 A of the flange  100  ( FIG. 4B ) such that the compressed air holds the valve  98  in the open position. In other words, the surface area  123 B of the second side  122 B that is exposed to the force of compressed air F 3 B′ is greater than the surface area  123 A of the first side  122 A that is exposed to the force of compressed air F 3 A′ when the valve  98  is in the open position, resulting in a larger force F 3 B′ applied to the second side  122 B of the valve  98  to maintain the valve  98  in the open position. 
     With reference to  FIG. 3D , the drive piston  70  is driven from the top-dead-center position to the bottom dead center position by the compressed air entering the first end  76  of the drive cylinder  66 . As the drive piston  70  is driven downwards, the drive blade  42  impacts the fastener  164  held in the magazine  14  and drives the fastener  164  into the workpiece until the drive piston  70  reaches the bottom-dead-center position. Just before the drive piston  70  reaches the bottom-dead-center position, any compressed air still acting on the drive piston  70  is vented from the drive cylinder  66  through the opening  88  to the atmosphere. 
     With reference to  FIG. 3E , to prepare for a subsequent fastener driving operation, the compressor piston  50  begins its return stroke and the valve  98  is closed (i.e., the flange  100  moves adjacent the insert  110 ) via the bias of the spring member  114 . In addition, an O-ring  116  positioned on the body  74  of the drive piston  70  blocks the opening  88  from further fluid communication to the atmosphere. 
     With reference to  FIG. 3F , the compressor piston  50  is driven downwards towards the bottom-dead-center position by the motor  54  and crank arm assembly  62  ( FIG. 2 ). As the compressor piston  50  is driven downward, a vacuum is created within the compressor cylinder  46  and the drive cylinder  66 , between the compressor piston  50  and the drive piston  70 . The O-ring  86  surrounding the ports  108  functions as a one-way valve through which air flows from the drive cylinder  66  to the compressor cylinder  46  in response to the vacuum developed in the compressor cylinder  46 . The vacuum draws the drive piston  70  upwards in the drive cylinder  66  toward the first end  76  due to the compressor cylinder  46  in fluid communication with the drive cylinder  66  via the ports  108  when the compressor piston  50  is driven downwards towards the bottom-dead-center position. Consequently, the drive piston  70  returns to the top-dead-center positon as the compressor piston  50  returns to the bottom-dead-center position such that the pneumatic fastener driver  10  is operable for a subsequent fastener driving operation. 
     With reference to  FIGS. 5A and 5B , the fastener driver  10  includes a trigger mechanism  118  having two triggers—the first or “primary” trigger  26  and a second or “auxiliary” trigger  120 . The auxiliary trigger  120  includes a nodule  124  that is capable of interfacing (i.e., depressing) with a lock-off button  128 , which is further engageable with a first switch  132  of a circuit board  136 . The auxiliary trigger  120  also includes an arcuate surface  140  that interfaces with (i.e., slides against) a corresponding arcuate surface  144  of the primary trigger  26 . The primary trigger  26  includes a projection  148  that is engageable with a second switch  152  of the circuit board  136 . The primary trigger  26  and the auxiliary trigger  120  are both moveable between a first position ( FIG. 5A ) and a second position ( FIG. 5B ). 
     In operation, a user grasps the handle portion  22  and pivots the auxiliary trigger  120  from the first position ( FIG. 5A ) toward the second position ( FIG. 5B ). By doing so, the arcuate surface  140  of the auxiliary trigger  120  no longer inhibits movement of the primary trigger  26 , while simultaneously depressing the lock-off button  128  with the nodule  124 . At this point, the primary trigger  26  is allowed to move between the first position ( FIG. 5A ) and the second position ( FIG. 5B ), and the first switch  132  of the circuit board  136  is depressed by the button  128 . With reference to  FIG. 5B , the projection  148  of the primary trigger  26  depresses the second switch  152  of the circuit board  136  once the primary trigger  26  is moved to the second position. After the triggers  26 ,  120  are depressed in sequence, thereby actuating the switches  132 ,  152  in sequence, a fastener driving operation is initiated. Specifically, the circuit board  136  sends a signal to supply power (via the battery pack  34 ) to actuate the compressor  30  for beginning the fastener driving operation as described above. 
     With continued reference to  FIGS. 5A and 5B , the circuit board  136  may be further configured to activate a work light  154  positioned on the pneumatic fastener driver  10  using the first switch  132 . Specifically, the movement of the auxiliary trigger  120  from the first position ( FIG. 5A ) to the second position ( FIG. 5B ) depresses the first switch  132  on the circuit board  136  as described above. Subsequently, the circuit board  136  sends a control signal to a power circuit board onboard the driver  10  to supply power (via the battery pack  34 ) to activate the work light  154 . As such, the combination of the first and second triggers  26 ,  120  is operable to initiate the fastener driving operation and activate a work light  154  of the pneumatic fastener driver  10 . 
     With reference to  FIGS. 6A-6C , the pneumatic fastener driver  10  includes a nosepiece  160  through which the fasteners  164  are driven into the workpiece, and the magazine  14  includes a pusher  168  for biasing the fasteners  164  in the magazine  14  toward the nosepiece  160 . In addition, the fastener driver  10  includes a dry-fire lockout mechanism  172  to prevent the pneumatic fastener driver  10  from operating when the number of fasteners  164  remaining in the magazine  14  drops below a predetermined value. 
     With continued reference to  FIGS. 6A-6C , the dry-fire lockout mechanism  172  includes a rod  176  that extends downwardly from the trigger  26 , which is actuated by the user when a fastener driving operation is initiated, as described above. The rod  176  is coupled to the trigger  26  via an arm  178  extending from the trigger  26  to the rod  176  ( FIG. 6B ). As such, the rod  176  translates upward (i.e., along direction  180  shown in  FIG. 6C ) as the trigger  26  is actuated by the user. 
     With reference to  FIGS. 7A-7D , the dry-fire lockout mechanism  172  also includes a latch  184  pivotably coupled to the magazine  14  having a front end  188  engageable with the fasteners  164  in the magazine  14  and a rear end  192 . The rod  176  defines a cutout  196  ( FIGS. 8A and 8B ) that is configured to receive the rear end  192  of the latch  184  when fewer than a predetermined number of fasteners  164  remain in the magazine  14 , thereby preventing further actuation of the trigger  26 . In other words, the rear end  192  of the latch  184  is pivotable between a non-interfering position relative to the rod  176  in which upward movement of the rod  176  (i.e., in the direction  180 ) is not inhibited ( FIGS. 8A and 8B ), and an interfering position in which the rear end  192  of the latch  184  is engageable with the rod  176  for preventing upward movement of the rod  176  and the connected trigger  26  ( FIGS. 9A and 9B ). 
     A torsion spring  200  ( FIG. 6C ) biases the latch  184  toward the interfering position shown in  FIG. 8A and 8B ; however, sliding engagement of the front end  188  of the latch  184  with the remaining fasteners  164  in the magazine  14  maintains the latch  184  in the non-interfering position ( FIGS. 7A and 8A-8B ). Upon the front end  188  of the latch  184  disengaging the last of a predetermined number of fasteners  164  remaining in the magazine  14  ( FIG. 7C ), the torsion spring  200  pivots the latch  184  from the non-interfering position shown in  FIGS. 8A and 8B  to the interfering position shown in  FIGS. 9A and 9B , in which the rear end  192  of the latch  184  is received in the cutout  196  in the rod  176  to inhibit upward movement of the rod  176  and the connected trigger  26 . 
     In operation, with reference to  FIGS. 8A and 8B , the number of fasteners  164  remaining in the magazine  14  is not less than the predetermined number of fasteners  164  such that the rear end  192  of the latch  184  is not received within the cutout  196  of the rod  176 . Therefore, the movement of the rod  176  by the actuation of the trigger  26  is not prevented by the latch  184  ( FIG. 7C ). In other words, the rod  176  is able to move past the rear end  192  of the latch  194  when the number of fasteners  164  remaining in the magazine  14  is not less than the predetermined number of fasteners  164 . In some embodiments, the predetermined number of fasteners remaining in the magazine  14  is five or less. For example, in one embodiment, the predetermined number of fasteners remaining in the magazine  14  is zero. 
     With reference to  FIGS. 9A and 9B , the number of fasteners  164  remaining in the magazine  14  is less than the predetermined number of fasteners  164  such that the rear end  192  of the latch  184  is received within the cutout  196  of the rod  176 . Therefore, the movement of the rod  176  by the actuation of the trigger  26  is prevented by the latch  184  ( FIG. 9B ). As such, the dry-fire lockout mechanism  172  prevents actuation of the trigger  26  to initiate a fastener driving operation when fewer than the predetermined number of fasteners  164  remains in the magazine  14 . 
     With reference to  FIGS. 6A, 6C, and 10 , the magazine  14  includes a base portion  210  and a cover  214 . The base portion  210  defines a plurality of slots  218  configured to receive a plurality of guide pins  222  ( FIG. 10 ). The slots  218  including the guide pins  222  are positioned at specific heights relative to a bottom edge  226  ( FIG. 6A ) of the magazine  14  corresponding to common lengths of the fasteners  164 . The guide pins  222  in contact with the collated strip of fasteners  164  move with the movement of the pusher  168  under the biasing force of a spring (not shown). 
     With reference to  FIG. 10 , the cover  214  defines a single continuous longitudinal channel  230  in facing relationship with the slots  218 . The channel  230  is configured to receive each end of the guide pins  222 , which are slidable within the channel  230  with the movement of the pusher  168  toward the nosepiece  160 . In addition, each of the slots  218  includes a slanted portion  234  relative to the cover  214  such that the ends of the guide pins  222  are positioned at an angle A 1  relative to a back wall  238  defining the channel  230 . In the illustrated embodiment, the angle A 1  is about 50 degrees relative to the back wall  238 . In other embodiments, the angle A 1  is between about 40 degrees and about 60 degrees relative to the back wall  238 . Specifically, the angle A 1  of the guide pins  222  in the channel  230  may inhibit the collated strip of fasteners  164  from being separated by the drive blade  42  as the drive piston  70  is returning to its top-dead-center position, which might otherwise result in the fastener driver  10  jamming. In the example shown in  FIG. 10 , the guide pin  222 ′ immediately above the collated strip of fasteners  164  is temporarily pivoted within its respective slot  218  to be substantially perpendicular to the back wall  238  when the drive piston  70  is returning to its top-dead-center position. The slanted portion  234  prevents the end of the guide pin  222 ′ from exceeding an angle A 1  greater than ninety degrees, thereby preventing substantial movement of the collated strip of fasteners  164  that might otherwise cause separation of the collated fastener strip leading to jamming of the fastener driver  10 . In particular, the slanted portion  234  prevents the end of the guide pin  222 ′ from exceeding an angle A 1  greater than ninety degrees, thereby preventing substantial movement of the collated strip of fasteners  164  relative to the magazine  14  in a direction parallel with the drive blade  42 . 
     Various features of the invention are set forth in the following claims.