Abstract:
A device for impacting a fastener in one embodiment includes a lever arm pivotable between a first position whereat a flywheel is spaced apart from a drive mechanism and a second position whereat the flywheel can contact the drive mechanism, a lever arm solenoid for pivoting the lever arm between the first position and the second position, a drive mechanism sensor for generating a position signal indicative of the position of the drive mechanism, a timer for generating a timing signal, a memory including program instructions, and a processor operably connected to the memory for executing the program instructions to (i) energize the solenoid to pivot the lever arm to the second position, (ii) de-energize the solenoid based upon the position signal, and (iii) de-energize the solenoid based upon the timing signal.

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of devices used to drive fasteners into work-pieces and particularly to a device for impacting fasteners into work-pieces. 
     BACKGROUND 
     Fasteners such as nails and staples are commonly used in projects ranging from crafts to building construction. While manually driving such fasteners into a work-piece is effective, a user may quickly become fatigued when involved in projects requiring a large number of fasteners and/or large fasteners. Moreover, proper driving of larger fasteners into a work-piece frequently requires more than a single impact from a manual tool. 
     In response to the shortcomings of manual driving tools, power-assisted devices for driving fasteners into wood have been developed. Contractors and homeowners commonly use such devices for driving fasteners ranging from brad nails used in small projects to common nails which are used in framing and other construction projects. Compressed air has been traditionally used to provide power for the power-assisted devices. Specifically, a source of compressed air is used to actuate a cylinder which impacts a nail into the work-piece. Such systems, however, require an air compressor, increasing the cost of the system and limiting the portability of the system. Additionally, the air-lines used to connect a device to the air compressor hinder movement and can be quite cumbersome and dangerous in applications such as roofing. 
     Fuel cells have also been developed for use as a source of power for power-assisted devices. The fuel cell is generally provided in the form of a cylinder which is removably attached to the device. In operation, fuel from the cylinder is mixed with air and ignited. The subsequent expansion of gases is used to push the cylinder and thus impact a fastener into a work-piece. These systems are relatively complicated as both electrical systems and fuel systems are required to produce the expansion of gases. Additionally, the fuel cartridges are typically single use cartridges. 
     Another source of power that has been used in power assisted devices is electrical power. Traditionally, electrical devices have been mostly limited to use in impacting smaller fasteners such as staples, tacks and brad nails. In these devices, a solenoid driven by electrical power from an external source is used to impact the fastener. The force that can be achieved using a solenoid, however, is limited by the physical structure of the solenoid. Specifically, the number of ampere-turns in a solenoid governs the force that can be generated by the solenoid. As the number of turns increases, however, the resistance of the coil increases necessitating a larger operational voltage. Additionally, the force in a solenoid varies in relation to the distance of the solenoid core from the center of the windings. This limits most solenoid driven devices to short stroke and small force applications such as staplers or brad nailers. 
     Various approaches have been used to address the limitations of electrical devices. In some systems, multiple impacts are used. This approach requires the tool to be maintained in position for a relatively long time to drive a fastener. Another approach is the use of a spring to store energy. In this approach, the spring is cocked (or activated) through an electric motor. Once sufficient energy is stored within the spring, the energy is released from the spring into an anvil which then impacts the fastener into the substrate. The force delivery characteristics of a spring, however, are not well suited for driving fasteners. As a fastener is driven further into a work-piece, more force is needed. In contrast, as a spring approaches an unloaded condition, less force is delivered to the anvil. 
     Flywheels have also been used to store energy for use in impacting a fastener. The flywheels are used to launch a hammering anvil that impacts the nail. A shortcoming of such designs is the manner in which the flywheel is coupled to the driving anvil. Some designs incorporate the use of a friction clutching mechanism that is both complicated, heavy and subject to wear. Other designs use a continuously rotating flywheel coupled to a toggle link mechanism to drive a fastener. Such designs are limited by large size, heavy weight, additional complexity, and unreliability. 
     Most mechanical designs (spring or flywheel) use a mechanical linkage to disengage the hammering anvil at the conclusion of the firing sequence to allow the tool to reset for a subsequent shot. These mechanical linkages are subject to wear and can be complex, leading to reduced life and unreliable operation. 
     What is needed is a triggering system which can be used to control delivery of impacting force in a device which is reliable and safe. What is needed is a system which can be used to disengage the hammering anvil at the conclusion of the firing sequence using low voltage energy sources and which involves fewer moving parts to increase reliability and life. 
     SUMMARY 
     In accordance with one embodiment, there is provided a device for impacting a fastener which includes a lever arm pivotable between a first position whereat a flywheel is spaced apart from a drive mechanism and a second position whereat the flywheel can contact the drive mechanism, a lever arm solenoid for pivoting the lever arm between the first position and the second position, a drive mechanism sensor for generating a position signal indicative of the position of the drive mechanism, a timer for generating a timing signal, a memory including program instructions, and a processor operably connected to the memory for executing the program instructions to (i) energize the solenoid to pivot the lever arm to the second position, (ii) de-energize the solenoid based upon the position signal, and (iii) de-energize the solenoid based upon the timing signal. 
     In accordance with another embodiment, a method of impacting a fastener includes energizing a solenoid, initiating a count based upon the energization of the solenoid, pivoting a flywheel into contact with a drive mechanism using the energized solenoid, monitoring the output of a sensor configured to generate a signal based upon the position of the drive mechanism, and de-energizing the solenoid based upon the first of (i) the count arriving at a predetermined threshold, or (ii) the output indicating that the drive mechanism has reached a predetermined location. 
     In accordance with a further embodiment, a device for impacting a fastener includes a lever arm solenoid configured to pivot a lever arm between a first position whereat a flywheel is spaced apart from a drive mechanism and a second position whereat the flywheel contacts the drive mechanism, a trigger sensor assembly for generating a trigger signal indicative of the position of the trigger, a drive mechanism sensor for generating a position signal indicative of the position of the drive mechanism, a memory including program instructions, and a processor operably connected to a timer, the trigger sensor assembly, the drive mechanism sensor, and the memory for executing the program instructions to (i) energize the lever arm solenoid based upon the trigger signal, (ii) de-energize the lever arm solenoid based upon input from the timer, and (iii) de-energize the lever arm solenoid based upon input from the drive mechanism sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a front perspective view of a fastener impacting device in accordance with principles of the present invention; 
         FIG. 2  depicts a side plan view of the fastener impacting device of  FIG. 1  with a portion of the housing removed; 
         FIG. 3  depicts a top cross sectional view of the fastener impacting device of  FIG. 1 ; 
         FIG. 4  depicts a side cross sectional view of the fastener impacting device of  FIG. 1 ; 
         FIG. 5  depicts a front perspective view of the lever arm assembly of the device of  FIG. 1 ; 
         FIG. 6  depicts a rear perspective view of the lever arm assembly of the device of  FIG. 1 ; 
         FIG. 7  depicts a partial perspective view of the device of  FIG. 1  showing a trigger, a trigger sensor switch and a hook portion of a lever arm which can inhibit rotation of the trigger; 
         FIG. 8  depicts a schematic of a control system used to control the device of  FIG. 1  in accordance with principles of the invention; 
         FIG. 9  depicts a partial cross sectional view of the trigger assembly of the device of  FIG. 1  when the actuating mechanism is positioned as shown in  FIG. 2 ; 
         FIG. 10  depicts a partial cross sectional view of the trigger assembly of the device of  FIG. 1  when the work contact element has been pressed against a work piece and the trigger or manual switch has been repositioned by a user; 
         FIG. 11  depicts a partial cross sectional view of the fastener impacting device of  FIG. 1  with the lever arm rotated so as to engage a drive member with the flywheel; 
         FIG. 12  depicts a partial cross sectional view of the fastener impacting device of  FIG. 1  after energization of the solenoid rotates the lever arm into contact with a drive mechanism and the drive mechanism has been moved through a full stroke in accordance with principles of the invention; 
         FIG. 13  depicts a partial cross sectional view of a spring loaded switch that is activated by combined positioning of the actuating mechanism and manual switch of the device of  FIG. 1  so as to interact with a sensor assembly; 
         FIG. 14  depicts a side plan view of the plunger and stem of the spring loaded switch of  FIG. 13 ; 
         FIG. 15  depicts a partial cross sectional view of a fastener impacting device incorporating a solenoid mechanism with a knee hinge to provide a mechanical advantage in pivoting a lever arm assembly; 
         FIG. 16  depicts a partial cross sectional view of a device with a solenoid activated lever arm which is positioned using a sled sliding on a surface; and 
         FIG. 17  depicts a partial cross sectional view of a solenoid activated lever arm which is positioned using a sled provided with wheels that roll on a surface. 
     
    
    
     DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains. 
       FIG. 1  depicts a fastener impacting device  100  including a housing  102  and a fastener cartridge  104 . The housing  102  defines a handle portion  106 , a battery receptacle  108  and a drive section  110 . The fastener cartridge  104  in this embodiment is spring biased to force fasteners, such as nails or staples, serially one after the other, into a loaded position adjacent the drive section  110 . With further reference to  FIG. 2 , wherein a portion of the housing  102  is removed, the housing  102  is mounted on a two piece frame  112  which supports a direct current motor  114 . Two springs  116  and  118 , shown more clearly in  FIG. 3 , are positioned about guides  120  and  122 , respectively. A solenoid  124  is located below the guides  120  and  122 . 
     The motor  114 , which is fixedly attached to the frame  112 , rotatably supports a lever arm assembly  126  through a bearing  128  shown in  FIG. 4 . Referring additionally to  FIGS. 5 and 6 , the lever arm assembly  126  includes a flywheel  130  and a flywheel drive wheel  132  rotatably supported by an axle  134 . A plurality of grooves  136  are formed in the outer periphery of the flywheel  130 . A belt  138  extends between the flywheel drive wheel  132  and a drive wheel  140  attached to the output shaft  142  of the motor  114 . The lever arm assembly  126  includes two spring wells  144  and  146  which receive springs  148  and  150 , respectively. A pin receiving recess  152 , which is best seen in  FIG. 4 , is located on the lower surface of a tongue  154 . 
     Continuing with  FIGS. 3 and 4 , a free-wheeling roller  156  is rigidly mounted to the frame  112  through a bearing  158  at a location above a drive member  160 . The drive member  160  includes an anvil  162  at one end and a guide rod flange  164  at the opposite end. A permanent magnet  166  is also located on the drive member  160 . The drive member  160  is movable between a front bumper  168  located at the forward end portions of the guides  120  and  122  and a pair of rear bumpers  170  and  172  located at the opposite end portions of the guides  120  and  122 . The front bumper  168  defines a central bore  174  which opens to a drive channel  176  in the fastener cartridge  104 . A Hall effect sensor  178  is located forward of the free wheeling roller  156 . 
     Referring to  FIG. 2 , an actuating mechanism  180  includes a slide bar  182  which is connected at one end to a work contact element (WCE)  184  and at the opposite end to a pivot arm  186 . A spring  188  biases the slide bar  182  toward the WCE  184 . The pivot arm  186  pivots about a pivot  190  and includes a hook portion  192  shown in  FIG. 7 . The hook portion  192  is configured to fit within a stop slot  194  of a trigger  196 . The trigger  196  pivots about a pivot  198  and is aligned to activate a spring loaded switch  200 . 
     The spring loaded switch  200  is used to provide input to a control circuit  210  shown in  FIG. 8 . The control circuit  210  includes a processor  212  that controls the operation of the motor  114  and the solenoid  124 . Power to the circuit  210  as well as the motor  114  and the solenoid  124 , is provided by a battery  214  coupled to the battery receptacle  108  (see  FIG. 1 ). The processor  212  receives a signal input from the spring loaded switch  200 , the Hall effect sensor  178 , and a flywheel speed sensor  220 . The control circuit  210  further includes a timer  222  which provides input to the processor  212 . A memory  224  is programmed with command instructions which, when executed by the processor  212 , provide performance of various control functions described here. In one embodiment, the processor  212  and the memory  224  are onboard a microcontroller. 
     Further detail and operation of the fastener impacting device  100  is described with initial reference to  FIGS. 1-8 . When the battery  214  is inserted into the battery receptacle  108  power is applied to the control circuit  210 . Next, the operator presses the work contact element  184  against a work-piece, pushing the work contact element  184  in the direction of the arrow  234  shown in  FIG. 2 . The movement of the work contact element  184  causes the slide bar  182  of the actuating mechanism  180  to compress the spring  188  and to pivot the pivot arm  186  about the pivot pin  190 . With reference to  FIGS. 9 and 10 , as the pivot arm  186  pivots about the pivot pin  190  in the direction of the arrow  236 , the hook portion  192  of the pivot arm  186  rotates in the direction of the arrow  236  out of the stop slot  194 . This allows the trigger  196  to be rotated in the direction of the arrow  238  to the position shown in  FIG. 10 . In  FIG. 10 , the trigger  196  is pressed against the spring loaded switch  200 . 
     As the trigger  196  presses against the spring loaded switch  200 , a signal is generated and sent to the processor  212 . In response to the signal, the processor  212  causes energy from the battery  214  to be provided to the motor  114  causing the output shaft  142  of the motor  114  to rotate in the direction of the arrow  230  of  FIG. 5 . Accordingly, the drive wheel  140 , which is fixedly attached to the output shaft  142 , also rotates in the direction of the arrow  230 . This rotational energy is transferred to the flywheel drive wheel  132  through the belt  138 . Rotation of the flywheel drive wheel  132  causes the axle  134  and the flywheel  130  to rotate in the direction of the arrow  232 . 
     The rotation of the flywheel  130  is sensed by the flywheel speed sensor  220  and a signal indicative of the rotational speed of the flywheel  130  is passed to the processor  212 . The processor  212  controls the motor  114  to increase the rotational speed of the flywheel  130  until the signal from the flywheel speed sensor  220  indicates that a sufficient amount of kinetic energy has been stored in the flywheel  130 . 
     In response to achieving a sufficient amount of kinetic energy, the processor  212  causes the supply of energy to the motor  114  to be interrupted, allowing the motor  114  to be freely rotated by energy stored in the rotating flywheel  130 . The processor  212  further starts the timer  222  and controls the solenoid  124  to a powered condition whereby a pin  264  is forced outwardly from the solenoid  124  in the direction of the arrow  266  shown in  FIG. 4 , and against the pin receiving recess  152 . The pin  264  thus forces the springs  148  and  150  to be compressed within the spring wells  144  and  146 . As the springs  148  and  150  are compressed by the expulsion of the pin  264 , the lever arm  126  rotates about the motor  114  in the direction of the arrow  266  of  FIG. 6  since the lever arm  126  is rotatably connected to the frame  112  through the motor  114  and the bearing  128 . 
     Rotation of the lever arm  126  forces the grooves  136  of the flywheel  130  into complimentary grooves  268  of the drive member  160  shown in  FIG. 11 . Accordingly, the drive member  160  is pinched between the freewheeling roller  156  and the fly wheel  130 . The fly wheel  130  transfers energy to the drive member  160  and the flange  164 , which is configured to abut the springs  116  and  118 , presses against the springs  116  and  118 , overcoming the bias of the springs  116  and  118  and forcing the drive member  160  toward the front bumper  168 . While the embodiment of  FIG. 11  incorporates springs, other embodiments may incorporate other resilient members in place of or in addition to the springs  116  and  118 . Such resilient members may include tension springs or elastomeric materials such as bungee cords or rubber bands. 
     Movement of the drive member  160  along the drive path moves the anvil  162  into the drive channel  176  through the central bore  174  of the front bumper  168  so as to impact a fastener located adjacent to the drive section  110 . 
     Movement of the drive member  160  continues until either a full stroke has been completed or until the timer  222  has timed out. Specifically, when a full stroke is completed as shown in  FIG. 12 , the permanent magnet  166  is located adjacent to the Hall effect sensor  178 . The sensor  178  thus senses the presence of the magnet  166  and generates a signal which is received by the processor  212 . In response to the first of a signal from the sensor  178  or timing out of the timer  222 , the processor  212  is programmed to interrupt power to the solenoid  124 . 
     In alternative embodiments, the Hall effect sensor may be replaced with a different sensor. By way of example, an optical sensor, an inductive/proximity sensor, a limit switch sensor, or a pressure sensor may be used to provide a signal to the processor  212  that the drive member  160  has reached a full stroke. Depending upon various considerations, the location of the sensor may be modified. For example, a pressure switch may be incorporated into the front bumper  168 . Likewise, the component of the drive member  160  which is sensed, such as the magnet  166 , may be positioned at various locations on the drive member. Additionally, the sensor may be configured to sense different components of the drive member  160  such as the flange  164  or the anvil  162 . 
     De-energization of the solenoid  124  allows the pin  264  to move back within the solenoid  124  as the energy stored within the springs  148  and  150  causes the springs  148  and  150  to expand thereby rotating the lever arm  126  in the direction opposite to the direction of the arrow  266  (see  FIG. 6 ). The flywheel  130  is thus moved away from the drive member  160 . When movement of the drive member  160  is no longer influenced by the flywheel  130 , the bias provided by the springs  116  and  118  against the flange  164  causes the drive member  160  to move in a direction toward the rear bumpers  170  and  172 . The rearward movement of the drive member  160  is arrested by the bumpers  170  and  172 . 
     The solenoid  124  and lever arm  126  are thus returned to the condition shown in  FIG. 4 . Accordingly, prior to re-energizing the motor  114  to initiate another impacting sequence, the signal from the from the trigger switch  200  must be interrupted by releasing the trigger  196 . 
     In the event that the fastener impacting device  100  is moved away from the work-piece after a fastener has been impacted and the trigger  196  has been released, the spring  188  forces the actuating mechanism  180  to return to the position shown in  FIG. 2 . In this position, the hook portion  192  of the pivot arm  186  is positioned within the stop slot  194  of the trigger  196  as shown in  FIG. 7 . In the configuration of  FIG. 7 , the hook portion  192  prevents rotation of the trigger  196  in the direction of the arrow  238  of  FIG. 9 . Accordingly, a fastener cannot be impacted before first pressing the WCE  184  against a work piece to allow operation in the manner described above. 
     In alternative embodiments, the processor  212  can accept a trigger input associated with the trigger  196  and a WCE input associated with the WCE  184 . The trigger input and the WCE input may be provided by switches, sensors, or a combination of switches and sensors. In one embodiment, the WCE  184  no longer needs to interact with the trigger  196  via an actuating mechanism  180  including a pivot arm  186  and a hook portion  192 . Rather, the WCE  184  interacts with a switch (not shown) that sends a signal to the processor  212  that indicates when the WCE  184  has been depressed. The WCE  184  may also be configured to be sensed rather than engaging with a switch. The sensor (not shown) may be an optical sensor, an inductive/proximity sensor, a limit switch sensor, or a pressure sensor. 
     In this alternative embodiment, the trigger switch can include a sensor that detects the position of the trigger such as the sensor  216  shown in  FIG. 13 . When the trigger  196  is repositioned, a spring  250  in the spring loaded switch  200  is compressed and a stem  252  moves outwardly from the spring loaded switch  200 . The trigger sensor  216  is positioned to detect movement of the stem  252 . 
     In this embodiment, the trigger sensor  216  includes a light source  256  and a photo sensor  258 . The light source  256  and the photo sensor  258  are positioned such that when the stem  252  is in the position shown in  FIG. 13 , a tail portion  260  (see  FIG. 14 ) of the stem  252  blocks light from the light source  256  from reaching the photo sensor  258 . When the stem  252  is moved to the right from the position shown in  FIG. 13 , however, a window  262  allows light from the light source  256  reach the photo sensor  258 . The photo sensor  258  senses the light and provides a signal to the processor  212  indicating that the spring loaded switch  200  has been repositioned. 
     This alternative embodiment can operate in two different firing modes, which is user selectable by a mode selection switch (not shown). In a sequential operating mode, depression of the WCE  184  causes a WCE signal, based upon a switch or a sensor, to be generated. In response, the processor  212  executes program instructions causing battery power to be provided to the motor  114 . The processor  212  may also energize the sensor  216  based upon the WCE signal. When the flywheel speed sensor  220  indicates a desired amount of kinetic energy has been stored in the flywheel  130 , the processor  212  then controls the motor  114  to maintain the rotational speed of the flywheel  130  that corresponds to the kinetic energy desired. 
     If desired, an operator may be alerted to the status of the kinetic energy available. By way of example, the processor  212  may cause a red light (not shown) to be energized when the rotational speed of the flywheel  130  is lower than the desired speed and the processor  212  may cause a green light (not shown) to be energized when the rotational speed of the flywheel  130  is at or above the desired speed. 
     In addition to causing energy to be provided to the motor  114  upon depression of the WCE  184 , the processor  212  starts a timer when battery power is applied to the motor  114 . If a trigger signal is not detected before the timer times out, battery power will be removed from the motor  114  and the sequence must be restarted. The timer  222  may be used to provide a timing signal. Alternatively, a separate timer may be provided. 
     If the trigger  196  is manipulated, however, the processor  212  receives a trigger signal from the trigger switch or trigger sensor  216 . The processor  212  then causes the supply of energy to the motor  114  to be interrupted, as long as the kinetic energy in the flywheel  130  is sufficient, allowing the motor  114  to be freely rotated by energy stored in the rotating flywheel  130 . The processor  212  further starts the first timer  222  and controls the solenoid  124  to a powered condition. In response to the first of a signal from the driver block sensor  178  or timing out of the timer  222 , the processor  212  is programmed to interrupt power to the solenoid  124 . Both the WCE switch/sensor and the trigger switch or trigger sensor  216  must be reset before another cycle can be completed. 
     Alternatively, an operator may select a bump operating mode using the mode selection switch. In embodiments incorporating a trigger sensor, positioning of the selection switch in the bump mode setting causes the trigger sensor to be energized. In this mode of operation, the processor  212  will supply battery power to the motor  114  in response to either the WCE switch/sensor signal or the trigger switch/sensor signal. Upon receipt of the remaining input signal, the processor  212  verifies that the desired kinetic energy is stored in the flywheel  130  and then causes the supply of power to the motor  114  to be interrupted and the battery power is supplied to the solenoid  124 . In response to the first of a signal from the driver block sensor  178  or timing out of the timer  222 , the processor  212  is programmed to interrupt power to the solenoid  124 . 
     In bump operating mode, only one of the two inputs must be reset. The processor  212  will supply battery power to the motor  114  immediately after the solenoid power is removed as long as at least one of the inputs remains activated when the other input is reset. When the reset input again provides a signal to the processor  212 , the sequence described above is once again initiated. 
     An alternative solenoid assembly is shown in  FIG. 15 . The solenoid assembly  280  may be used in a fastener impacting device which is substantially the same as the fastener impacting device  100 . The solenoid assembly  280  includes a solenoid  282  which is oriented with a pin  284  that moves along an axis somewhat parallel to the tongue  286  of a lever arm assembly (not otherwise shown) configured like the lever arm assembly  126 . The pin  284  is connected to a knee hinge  290  through a shaft  292  and a pin  294 . The knee hinge  290  includes an upper arm  296  which is rotatably connected to the tongue  286  through a pin  298  and a lower arm  300  which is rotatably connected to a frame portion  302  through a pin  304 . A stop  306  is located on the lower arm  300 . 
     Operation of a fastener impacting device with the solenoid assembly  280  is substantially the same as operation of the fastener impacting device  100 . The main difference is that when the solenoid  282  is controlled to a powered condition, the pin  284  is pulled into the solenoid  282  thereby causing the shaft  292  to move in the direction of the arrow  308  shown in  FIG. 15 . The shaft  292  pulls the knee hinge  290  in the direction of the arrow  308 . 
     Because the upper arm  296  of the knee hinge  290  is pivotably connected to the tongue  286  through the pin  298 , and the lower arm  300  of the knee hinge  290  is pivotably connected to the frame portion  302  through the pin  304 , the knee hinge  290  is forced toward an extended condition. In other words, the upper arm  296  pivots in a counter-clockwise direction about the pin  298  while the lower arm  300  pivots in a clockwise direction about the pin  304 . Extension of the knee hinge  290  causes rotation of the lever arm assembly  288  about a pivot in a manner similar the rotation of the lever arm assembly  126 . 
     An alternative solenoid mechanism is depicted in  FIG. 16 . The solenoid mechanism  310  includes a solenoid  312  with a solenoid pin  314 . The solenoid pin  314  is operatively connected to a sled  316  positioned on a slide  318 . An arm  320  is pivotably connected to the sled  316  at one end and to a lever arm  322  at the other end. 
     The solenoid mechanism  310  operates in a fastener impacting device in substantially in the same manner as the solenoid mechanism  280 . The main difference is that in place of a knee hinge such as the knee hinge  290 , the solenoid mechanism  310  includes the sled  316 . Accordingly, energization of the solenoid  312  causes the sled  316  to move across the slide  318 , thereby forcing the lever arm  322  to rotate. In a further embodiment, frictional forces are reduced by providing a sled  330  with wheels  332  as shown in  FIG. 17 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.