Patent Publication Number: US-2023150102-A1

Title: Electric carpet stapler with optical switch assembly

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/904,040, filed Jun. 17, 2020, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     An electric carpet stapler is an electrically-powered tool for stapling carpet to wooden subfloor surfaces to prevent the carpet from moving, particularly on staircases. U.S. Pat. No. 3,209,180 to Doyle describes a prior art electric carpet stapler which includes an operating winding, an armature attached to a fastener driving element, an armature return spring, a switch, and a control circuit. In various ways, a switch like Doyle&#39;s may be used to produce a trigger signal to a control circuit, or to temporarily provide mains power to a control circuit. After being triggered, the control circuit begins a process that supplies power to the operating winding to magnetically actuate the armature. Examples of prior art control circuits are described in U.S. Pat. No. 3,141,171 to Doyle, U.S. Pat. No. 3,434,026 to Doyle, U.S. Pat. No. 3,662,190 to Naber, and U.S. Pat. No. 3,924,789 to Avery. 
     In the device of U.S. Pat. No. 3,209,180 to Doyle, as shown in  FIG.  1   , staples are sequentially supplied by a magazine assembly 28 into a drive track 24 of a nosepiece 26. The nosepiece 26 is narrow and able to penetrate the rows of carpet tufts down to the carpet backing, which is stapled to the subfloor surface. When the winding 16 is energized, the armature 20 and driver blade 22 are accelerated rapidly downward to drive the staple. After driving the staple, return spring 30 returns armature 20 and driver blade 22 to their normal position, ready for the next driving action. 
     To produce a trigger signal for a control circuit, trigger 80 is pulled, which through a series of actions results in switch operator 38a of switch 38 being depressed. Switch 38 is generally a “snap action” microswitch, which is mechanical and quite small in size, and which can fit in the handle 12 along with the control circuit (not shown). However, as shown in FIG. 5 herein, the mechanical components in the prior art microswitch 200 are quite small and delicate. The extreme recoil and vibration produced in the electric carpet stapler as it drives the staple into a subfloor can damage the microswitch. For that reason, replacement of microswitches is frequently required maintenance for existing electric carpet staplers. 
     Existing control circuits for an electric carpet stapler have generally depended on a mechanical microswitch that is separate from the control circuit element itself to cause the control circuit to supply power to the winding. In one design, when mains power is connected, power is supplied to the control circuit. The microswitch, which is wired to the control circuit, switches a lower voltage signal, which when in the closed condition signals the control circuit to begin a process to supply power to the winding. Since the electric carpet stapler is designed to operate on alternating current electricity available in homes, the control circuit is generally programmed to delay sending a control signal to a gate or SCR (“silicon-controlled rectifier”) until a zero crossing of the alternating current, at which time it supplies power to the winding. 
     To further describe the functions of the trigger assembly of a prior art electric carpet stapler, it generally has included a pivoting trigger, a trigger return spring, and the prior art microswitch. When the trigger is first pulled by a user, to prevent unwanted actuation, the trigger will pivot from a starting position and bias a trigger return spring before causing the microswitch to close, a process that will be referred to as “pre-actuation.” After the pre-actuation, the “actuation” occurs as the microswitch closes, which creates a signal to the control circuit to begin a process to supply power to the winding. At or just after the actuation, the assembly may mechanically produce a palpable signal to the user or “click” that indicates the point in the trigger&#39;s motion that corresponds to the actuation. The click signal is often produced by the mechanical microswitch at about the time it closes. This can be helpful for training the user to use the electric carpet stapler, when the stapler is preferably not connected to power. After the actuation, a “post actuation” permits further travel of the trigger in the pulling direction, conforming to the natural motion of the trigger finger, and eliminating an unergonomic hard stop. At any point after the trigger is first pulled by a user, a “reset” of the assembly involves the return of the trigger to its starting position, normally by the trigger return spring, and the opening of the microswitch. 
     Beyond producing the actuation, the design of the trigger assembly should ensure that, for any one pulling of the trigger, at most one actuation can possibly occur. In existing trigger assemblies, this is partly ensured by the single acting “over center” closing action of microswitch. It is also ensured by the action of the trigger return spring, which ensures that the trigger once released will only rotate back to the trigger starting position, preventing the microswitch from closing again on its own. 
     To reduce maintenance costs for the prior art electric carpet stapler related to the microswitch, it would be desirable to provide a more durable trigger and switch assembly, which could still perform the functions of the prior art trigger assembly, microswitch, and control circuit. 
     SUMMARY 
     Embodiments of the invention include an electric carpet stapler that comprises a trigger and switch assembly that has an actuation caused by a change of state of a sensor, which causes the sensor to send a signal to a control circuit to begin a process to supply power to a winding. In one embodiment, the trigger and switch assembly includes a trigger that moves in a trigger actuation direction to move a sensor actuator in a sensor actuation direction, causing a change of state in the sensor comprising a change from a sensor signal-on state to a sensor signal-off state, which causes the control circuit to begin the process to supply power to the winding. In another embodiment, the change of state of the sensor comprises a change from a sensor-signal-off state to a sensor signal-on state, which causes the control circuit to begin the process to supply power to the winding. 
     In one embodiment, the trigger and switch assembly includes a trigger that moves a sensor actuator comprising a slider, a sensor comprising a photo sensor, and the control circuit. The photo sensor includes a light emitter comprising a light emitting diode that emits infrared light and a light sensor that comprises a silicon photo transistor. As the trigger is pulled, it moves the slider to permit or prevent the infrared light from passing to the silicon photo transistor. In one embodiment of the control circuit, when light contacts the silicon photo transistor, the silicon photo transistor behaves as a switch that closes to conduct to ground. This causes the voltage on a conductor to the control circuit to drop to near-zero, which is referred to herein as a sensor signal-off signal. When the control circuit detects the sensor signal-off signal, it begins the process to supply power to the winding. Afterwards, when the trigger is released, the slider prevents light from contacting the silicon photo transistor. This causes the photo sensor to behave like a switch that opens to cause a sensor sensor-on signal, which increases the voltage on the conductor to the control circuit and thereby resets the control circuit to receive a next sensor signal-off signal. 
     In an alternative embodiment of the control circuit, when the slider permits light to pass to the silicon photo transistor, the silicon photo transistor conducts creating a signal on the conductor to the control circuit comprising an increase in voltage to signal the control circuit to begin a process to supply power to the winding. 
     In one embodiment, the trigger and switch assembly includes a trigger that moves from a trigger starting position in a trigger actuation direction to move a sensor actuator comprising a slider, and a sensor comprising a photo sensor that senses the passing of light from a light emitter to a light sensor. In one embodiment, the slider includes a slider aperture, and the motion of the trigger in the trigger actuation direction moves the slider in a slider actuation direction moving the slider aperture to permit light to pass from the light emitter of the photo sensor to the light sensor, causing a change of state of the photo sensor, from a sensor signal-on state to a sensor signal-off state, which signals the control circuit to begin the process to supply power to the winding. The point at which the trigger has moved far enough in the trigger actuation direction to move the slider aperture far enough to permit light to pass from the light emitter of the photo sensor to the light sensor is referred to as the trigger point of actuation. The point at which the trigger is stopped from moving any further in the trigger actuation direction at the end of the post-actuation is referred to as the trigger stop. In one embodiment, the slider aperture has a length permitting light to pass from the light emitter of the photo sensor to the light sensor in the entire travel of the slider as it is moved by the trigger from the trigger point of actuation to the trigger stop. 
     In another embodiment, the trigger and switch assembly includes a trigger, a photo sensor, and a sensor actuator comprising a slider, and the trigger instead moves the slider to prevent light from passing from the light emitter of the photo sensor to the light sensor, causing the change of state of the photo sensor which signals the control circuit to begin a process to supply power to a winding. 
     In another embodiment, the trigger and switch assembly comprises a trigger that moves a slider, and the slider moves in a horizontal axis of the handle portion of the electric carpet stapler. In another embodiment, the photo sensor includes an opening for the slider in the horizontal axis of the handle. In another embodiment, the photo sensor is positioned in a portion of the control circuit proximate the trigger. 
     In another embodiment, the trigger and switch assembly includes a trigger that moves a sensor actuator, a sensor, and a toggle. At the actuation of the trigger and switch assembly, the toggle creates a mechanical instability, requiring the trigger to move either towards the trigger stop, or towards the trigger starting position, but will not allow it to remain at the trigger point of actuation. In one embodiment, at the actuation, the change of state in the sensor caused by the sensor actuator happens at the same point that the mechanical instability occurs in the trigger and switch assembly. In one embodiment, at or shortly after the actuation, the toggle creates a toggle signal to the user. In one embodiment, the toggle signal is produced mechanically. 
     In one embodiment, the trigger and switch assembly includes a trigger, a sensor actuator comprising a slider, a photo sensor, and a toggle comprising a point on the slider that contacts another point on the trigger and switch assembly. In one embodiment, the toggle comprises a rounded projection on the slider which comes into contact with an apex of a circular ball, and a ball spring that is biased as the ball is moved. A pulling motion of the trigger by a user from the trigger starting position produces motion of the slider in a pulling direction, causing the rounded projection of the slider to contact the ball, which lifts the ball up a leading section of the rounded projection, and which biases the ball spring. At the actuation, an unstable point-to-point contact between the apex of the rounded projection of the slider and the apex of the ball produces the mechanical instability. In one embodiment, at the actuation, the mechanical instability between the rounded projection of the slider and the ball occur at the same time that the slider changes the state of the sensor to cause the control circuit to begin a process to supply power to a winding. 
     In one embodiment, the trigger and switch assembly comprises a trigger that moves a slider having a slider aperture, a trigger return spring, a photo sensor, a control circuit, and a toggle comprising a rounded projection on the slider, a ball, and a ball spring. When the trigger is pulled and moves from the trigger starting position, the trigger return spring is biased to return the trigger to a trigger starting position. After the trigger is pulled in a trigger actuation direction far enough to move the slider aperture to permit light to pass from the light emitter of the photo sensor to the light sensor to cause the control circuit to begin a process to supply power to the winding, the apex of the rounded projection of the slider is in an unstable point-to-point contact with the apex of the ball and produces the mechanical instability. At this mechanical instability, the trigger is required to move either by being further pulled in the trigger actuation direction by a user towards the trigger stop, and in such case the slider aperture has a length permitting light to continue to pass as it is pulled by the trigger to the trigger stop, or else the trigger if released is required to return to the trigger starting position due the bias of the return spring, which moves the slider aperture to prevent light from passing from the light emitter of the photo sensor to the light sensor. When light is prevented from passing to the light sensor, this causes a change of state of a photo sensor which resets the control circuit for the next process to supply power to the winding. In the pre-actuation, whether the trigger is pulled or released, there will also be no change in state of the photo sensor, because the slider will not have moved enough to permit light to pass. For these reasons, any pulling of the trigger by a user should cause the control circuit to begin a process to supply power to winding one time only. 
     In one embodiment, instantaneously after the actuation, continued pulling motion of the trigger pulls the slider which permits the ball to move down a steep trailing section of the rounded projection, causing the ball to be accelerated by the ball spring to impact a surface, creating a toggle signal comprising a click that is produced mechanically. In one embodiment, when the electric carpet stapler is not connected to power, if the trigger is pulled, the mechanical click is an indication to a user that the actuation would occur at about the time of the click. 
     In one embodiment of the trigger and switch assembly, after the trigger is pulled from a trigger starting position, to any point in the pre-actuation, actuation, or post-actuation, a subsequent reverse motion of the trigger in a trigger reset direction is referred to as a reset. In one embodiment, if in the reset the trigger moves from the actuation or post-actuation to the pre-actuation, the trigger moves the sensor actuator to cause another change of state in the sensor comprising a change from a sensor signal-off state to a sensor signal-on state, and the sensor signal-on state sends a signal to the control circuit that resets it to receive a next sensor signal-off signal to supply power to the winding. In another embodiment, the change of state of the sensor is from a sensor signal-on state to a sensor signal-off state, which resets the control circuit to receive a next signal-on signal to supply power to the winding. 
     In one embodiment, during a reset after an actuation, the trigger is moved in a trigger reset direction towards a trigger starting position. This causes a slider having a slider aperture to move in a slider reset direction and thereby prevents light from passing from the light emitter of the photo sensor to the light sensor. This also causes another change of state of a photo sensor comprising a sensor signal-on state, resetting the control circuit to receive a next sensor signal-off signal to supply power to the winding. In another embodiment, the slider moves in the slider reset direction to permit light to pass from the light emitter of the photo sensor to the light sensor, causing the change of state of the photo sensor to reset the control circuit to receive a next signal to supply power to the winding. 
     In one embodiment, the trigger and switch assembly further includes a trigger return spring that is biased after the trigger is pulled to return the trigger in the trigger reset direction to a trigger starting position of the pre-actuation. In one embodiment, at the starting position of the pre-actuation, the rounded projection of the slider no longer contacts the ball. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram and partial section views of an electric carpet stapler at the pre-actuation, with the trigger at a trigger starting position, in accordance with an embodiment of the invention. 
         FIG.  2    is a diagram and partial section views of the electric carpet stapler of  FIG.  2    at the actuation, in accordance with an embodiment of the invention. 
         FIG.  3    is a diagram and partial section views of the electric carpet stapler of  FIG.  3    in the post-actuation, in accordance with an embodiment of the invention. 
         FIG.  4    is a diagram and partial section view of the electric carpet stapler of  FIG.  4    showing the motion of trigger  10100 , in accordance with an embodiment of the invention. 
         FIG.  5    shows a prior art microswitch. 
         FIG.  6    is a circuit diagram of an embodiment of a control circuit, in accordance with an embodiment of the invention. 
     
    
    
     The figures depict various embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein. 
     DETAILED DESCRIPTION 
       FIG.  1    shows an end view of an electric carpet stapler  10000  that includes a plastic housing  10020  formed in a left half  10021  and right half  10031 , and an aluminum cap  10040 . Section A-A is taken at about the centerline between left half  10021  and right half  10031 . Section A-A shows that electric carpet stapler  10000  internally includes a trigger  10100 , a trigger return spring  10200 , a slider  10300 , control circuit  10400 , alternating current mains wires  10500 , winding supply wires  10600 , winding  10700 , armature  10800  which is connected to a staple driver blade  10810 , and armature return spring  10820 . In Section A-A, trigger  10100  is at a trigger starting position  10121  at the beginning of the pre-actuation. Trigger  10100  includes a trigger arm  10110  that extends through a trigger arm opening  10310  in slider  10300 . When trigger  10100  is pulled as by pressure from the user&#39;s finger at trigger surface  10120 , trigger  10100  will rotate counter-clockwise on pivot  10130 , causing trigger arm  10110  to rotate counter-clockwise, and causing slider  10300  to be pulled in a pulling direction connoted by arrow  10340 . 
     As shown in Section A-A of  FIG.  1   , trigger  10100 , trigger return spring  10200 , slider  10300 , metal sleeve  10330  (Section B-B), control circuit  10400 , ball  10900  (Section B-B) and ball spring  10910  (Section B-B) comprise the main components of a trigger and switch assembly  10050  for the electric carpet stapler  10000 . In the embodiment of Section A-A, photo sensor  10410  is a component of control circuit  10400 . In alternative embodiments, photo sensor  10410  could be part of a circuit separate from control circuit  10400 . Section A-A also shows that trigger  10100  is at a trigger starting position  10121  with a back side  10111  of a trigger arm  10110  against a trigger start surface  10022  (a feature of housing left half  10021 ). 
     Section G-G of  FIG.  4    provides an introduction to the motion of trigger  10100  and how its positions correspond to different functions of the trigger and switch assembly. Trigger  10100  has a trigger starting position  10121 , a trigger point of actuation  10123 , and a trigger stop position  10124 . As used herein to describe embodiments of the present invention, the following terms are defined as follows: the pre-actuation is the arc  10127  from the trigger starting position  10121  to just before the trigger point of actuation  10123 . The actuation is at trigger point of actuation  10123 . The post-actuation is the arc  10129  from just after the trigger point of actuation  10123  to the trigger stop position  10124 . Arc  10131  connotes the reset. At any point in the arc  10131  from just after trigger starting position  10121  to the trigger stop position  10124 , if the trigger is released, a reset of the trigger and switch assembly occurs, with the trigger return spring  10200  moving trigger  10100  back to the trigger starting position  10121 . As used herein, with regards to the motion of the trigger, the phrase “past the trigger point of actuation,” means continuing motion of the trigger after the trigger point of actuation  10123  that is in a direction away from the trigger starting position  10121 , but not necessarily to a trigger stop position  10124 , as some embodiments do not include a trigger stop, such as trigger stop  10024  (Section C-C of  FIG.  2   ). 
     Referring back to  FIG.  1   , Section B-B of Section A-A shows trigger and switch assembly  10050  from the top of slider  10300  and shows rounded projection  10320  in relation to a ball  10900  and ball spring  10910  in the beginning of the pre-actuation. Ball  10900  and spring  10910  are held in an opening  10023  formed in left half  10021  of plastic housing  10020  ( FIG.  1   ). Attached to slider  10300  is a metal sleeve  10330 , which is formed as a u-shaped channel fitting onto an inner side  10305  of slider  10300 . Metal sleeve  10330  includes a slot  10331  for rounded projection  10320  to extend through. As slider  10300  is a small and complex shape, it is preferred to form it as a plastic molding. Metal sleeve  10330  mainly serves to protect slider  10300  from wear from ball  10900 , but also has a hardness that increases a click sound created by being impacted by ball  10900 , as described below in the discussion of the post-actuation. 
     In the beginning of the pre-actuation, as shown in Section B-B, ball  10900  is not in contact with rounded projection  10320 , but rests against an outer forward surface  10332  of metal sleeve  10330 . During the pre-actuation, as trigger  10100  ( FIG.  1   ) is pulled, trigger arm  10110  rotates counter-clockwise and pulls slider  10300  in the pulling direction of arrow  10340 , but not to a point where aperture  10350  causes a change of state of photo sensor  10410  (to be described below). This pulling motion in the direction of arrow  10340  also causes a forward section  10321  of rounded projection  10320  to contact ball  10900 . Gradually, rounded projection  10320  lifts ball  10900  up forward section  10321 , but not up to apex  10322  (which is shown in  FIG.  2   , Section D-D). This motion biases ball spring  10910 . Furthermore, as shown in Section A-A, as soon as trigger  10100  is pulled from the trigger starting position  10121 , trigger return spring  10200  is biased, putting force on trigger  10100  to move back in the clockwise direction. Therefore, at any point during pre-actuation, if trigger  10100  is released, trigger  10100  will move in the clockwise direction, and slider  10300  will move in the reset direction of arrow  10380 , and there will be no change of state of photo sensor  10410 . 
       FIG.  2    shows a section C-C of the electric carpet stapler  10000  with trigger and switch assembly  10050  at the actuation. The counter-clockwise rotation of trigger  10100  has moved slider  10300  to its position at the actuation. Section D-D shows trigger and switch assembly  10050  from the top of slider  10300 . As shown in Section C-C, as slider  10300  is pulled in the pulling direction of arrow  10340 , aperture  10350  moves to permit light to pass from the light emitter  10411  of photo sensor  10410  to light sensor  10412 , causing a change of state of the photo sensor  10410 , from a sensor signal-on state to a sensor signal-off state which signals the control circuit  10400  to begin a process to supply power to the winding  10700 . During that same motion of slider  10300 , as shown in Section D-D, rounded projection  10320  also moves in the pulling direction of arrow  10340 , causing the apex  10901  of ball  10900  to reach and contact the apex  10322  of rounded projection  10320 . 
     After the actuation, Section E-E of  FIG.  3    shows trigger and switch assembly  10050  of electric carpet stapler  1000  at the post-actuation. Pressure from the user&#39;s finger on trigger surface  10120  causes trigger  10100  to continue to rotate counter-clockwise and pull slider  10300  in the pulling direction of arrow  10340 . Section F-F of Section E-E shows trigger and switch assembly  10050  from the top of slider  10300 . Almost instantaneously after the actuation, as the apex  10322  of rounded projection  10320  moves past the apex  10901  of ball  10900 , the steep downward slope of the trailing section  10323  of rounded projection  10320  permits ball  10900  to be rapidly accelerated by ball spring  10910  and impact metal sleeve  10330  at trailing surface  10333 . The impact of ball  10900  on metal sleeve  10330  produces haptic feedback in the form of a click that a user can associate with the actuation. These motions of trigger and switch assembly  10050  producing the click are mechanical and occur even if power is not connected. As such, the click in the trigger and switch assembly  10050  is beneficial in training a user to use electric carpet stapler  10000  (Section E-E), which should occur with power disconnected. As shown in Section E-E, in the post-actuation, the user can continue pulling trigger  10100  until the front side  10112  of trigger arm  10110  contacts the trigger stop  10024 , which provides some travel for a natural motion of the trigger finger. 
     In the post-actuation, as shown in Section E-E, because of the length  10351  (Section F-F) of aperture  10350 , light continues being permitted to pass from the light emitter  10411  of to the light sensor  10412  of photo sensor  10410 , causing no change of state of photo sensor  10410 . As a result, during the post-actuation, photo sensor  10410  cannot have a change of state or send a second signal to the control circuit  10400  to begin a process to supply power to the winding  10700  (Section E-E) a second time. 
     As shown in Section E-E of  FIG.  3   , by the post-actuation, trigger  10100  has strongly biased trigger return spring  10200 . As the user releases the trigger  10100 , the bias of trigger return spring  10200  ensures that trigger  10100  and trigger arm  10110  will rotate back in the clockwise direction, causing slider  10300  to move in the reset direction connoted by arrow  10380 . These motions continue until the elements return to their positions in Section A-A of  FIG.  1   . As shown in Section A-A of  FIG.  1   , aperture  10350  of slider  10300  passes beyond light emitter  10411  and blocks light from passing to the light sensor  10412 , producing another change of state of a photo sensor  10410  that produces the sensor sensor-on signal to the control circuit  10400 , which resets the control circuit  10400  to receive a next sensor signal-off signal for a next actuation. However, as shown in Section C-C of  FIG.  2   , no such actuation can occur until the trigger is again pulled by a user to the trigger point of actuation  10123  (Section G-G of  FIG.  4   ). 
     At the actuation, as shown in Section C-C of  FIG.  2   , features of trigger and switch assembly  10050  ensure that, for any one pulling of trigger  10100 , there will only be at most one actuation due to one change of state of photo sensor  10410  to the sensor signal-off state that comprises a signal to the control circuit  10400  to begin a process to supply power to the winding  10700 . By the actuation, trigger  10100  has been pulled in a counter-clockwise direction, and return spring  10200  is biased. At the actuation, as shown in Section D-D, slider  10300  has moved to position the apex  10322  of rounded projection  10320  in contact with the apex  10901  of ball  10900 , biasing ball spring  10910 , and creating a mechanical instability. At the mechanical instability, as shown in Section C-C, trigger  10100  is required to move, either by being pulled counter-clockwise by a user up the point that trigger arm  10110  contacts the trigger stop  10024 , in which case the length  10351  (Section D-D) of aperture  10350  (Section D-D) continues permitting light to pass to pass, resulting in no change of state in photo sensor  10410 , or else if trigger  10100  is released, it is required to move clockwise towards the trigger starting position  10121  (Section A-A of  FIG.  1   ) of the pre-actuation due to the bias of return spring  10200 . As shown in Section A-A of  FIG.  1   , when trigger  10100  moves clockwise, slider aperture  10350  of slider  10300  moves to prevent light from passing from the light emitter  10411  of the photo sensor  10410  to the light sensor  10412 , causing a change of state of a photo sensor  10410  to a sensor signal-on state, producing a sensor signal-on signal on the conductor to the control circuit, resetting the control circuit to receive a next sensor signal-off signal. At any point of the pre-actuation, whether trigger  10100  is pulled or released, there will also be no change in state of photo sensor  10410  from the sensor signal-on state, because slider  10300  will not be moved far enough in the pulling direction of arrow  10340  for aperture  10350  to permit light through. For these reasons, any motion of trigger  10100  by a user should at most cause the control circuit  10400  to begin a process to supply power to winding  10700  one time only. 
     As shown in Section E-E of  FIG.  3   , if left to its own in a reset that occurs after an actuation, the trigger and switch assembly  10050  should be able to change photo sensor  10410  only from the sensor signal-off state to the sensor signal-on state. Once the user pulls the trigger  10100  far enough counter-clockwise past the trigger point of actuation, where photo sensor  10410  produces the sensor signal-off state, trigger return spring  10200  is biased to turn trigger  10100  back in the clockwise direction to the trigger starting position  10121  ( FIG.  1   , Section A-A) of the pre-actuation. Once reaching the pre-actuation, as shown in Section A-A of  FIG.  1   , trigger  10100  has moved slider  10300  and aperture  10350  so that light from photo sensor  10410  is prevented from passing from light emitter  10411  of the photo sensor  10410  to the light sensor  10412 , and photo sensor  10410  can change only from the sensor signal signal-off state to the sensor signal signal-on state. As shown in Section B-B of  FIG.  1   , moving trigger  10100  (Section A-A) to a trigger starting position  10121  (Section A-A) causes ball  10900  to no longer contact rounded projection  10320  of slider  10300 . 
     As shown in Section G-G of  FIG.  4   , the electric carpet stapler  10000  has a housing  10020  that generally has a handle portion  10025  with a horizontal axis  10026 . Slider  10300  moves in a horizontal axis  10026  of the handle portion  10025 . Photo sensor  10410  includes an opening  10413  for the slider  10300  in the horizontal axis of the handle. In one embodiment, photo sensor  10410  is positioned at a portion  10401  of the control circuit  10400  proximate the trigger  10100 . 
       FIG.  6    shows a simplified circuit diagram of an embodiment of a control circuit including a photo sensor circuit  10450  that produces the sensor signal off signal that causes a logic circuit  10460  to begin a process to supply power to the winding  10700 . Photo sensor  10410  comprises a light emitter  10411  comprising a light emitting diode that emits infrared light, and a light sensor  10412  comprising a silicon photo transistor. Photo sensor  10410  is supplied by VCC  10451  on conductor  10452 , which powers the light emitter  10411 , and on conductor  10455 , which powers light sensor  10412 . At the actuation, light  10414  passing from light emitter  10411  contacts light sensor  10412  and causes light sensor  10412  to behave like a closed switch that conducts on conductor  10456  to ground  10454 . This creates a signal on conductor  10457  to the logic circuit  10460  comprising a drop in voltage to near zero, referred to herein as a sensor signal-off signal. When the logic circuit  10460  detects the sensor signal-off signal, it begins the process to supply power to the winding  10700 . 
     Afterwards, when the trigger is released the slider prevents light  10414  from light emitter  10411  from contacting light sensor  10412 . This causes light sensor  10412  to behave like a switch that opens to cause a signal referred to herein as a sensor signal-on signal, comprising an increase in voltage on the conductor  10457  to the logic circuit  10460 . This resets the logic circuit  10460  to receive a next sensor signal-off signal. 
     In one embodiment, logic circuit  10460  is a microchip programmed to sense changes in voltage on conductor  10457  and can supply a current on the gate  10461  to control a silicon-controlled rectifier  10462  to supply power to winding  10700 . In alternative embodiments to the photo sensor circuit  10450 , the light sensor  10412  conducts an alternative type of signal to the conductor to the control circuit, for example an increase in voltage that signals the logic circuit  10460  to begin a process to supply power to the winding. 
     Embodiments of the invention described herein employ an electronic sensor comprising a photo sensor that has a change of state in response to the motion of a sensor actuator. Other embodiments use other types of electronic sensors, including inductive sensors that create magnetic fields that when disturbed change the state of the sensor, or capacitive sensors that sense changes in capacitance. However, photo sensors advantageously provide low cost and very durable designs that can withstand vibration and that are also not affected by electrical interference produced by the winding. 
     As used herein, and as shown in  FIG.  6   , in one embodiment, the change of state in photo sensor  10410  that is caused by light  10414  passing from light emitter  10411  and contacting light sensor  10412 , and that causes light sensor  10412  to behave like a switch that conducts on conductor  10456  to ground  10454 , is an electronic change in state. Unlike the prior art mechanical microswitch 200 ( FIG.  5   ), the electronic change of state in photo sensor  10410  is caused by an electronic change of photo sensor  10410 , in this case a change in resistance, and not by a mechanical motion. Other embodiments using other types of electronic sensors may have other electronic changes in state. In some embodiments, a part of the electronic sensor is a semiconductor. 
     The foregoing description of the embodiments of the invention has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure. The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.