Abstract:
The present invention is directed to a system that controls the automatic operation a laser in a sighting mechanism to detect a target. The laser is activated when the system detects vibrational motion that causes a piezoelectric strip to produce an electrical signal. The laser is deactivated after a predetermined time has elapsed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims benefit of U.S. provisional application Ser. No. 60/412,832, filed Sep. 23, 2002, the disclosure of which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to the activation of a laser beam for a sighting mechanism.  
       BACKGROUND OF THE INVENTION  
       [0003]     A variety of light beam assemblies have been disclosed as sighting aids for weapons. These assemblies are either mounted on or are an integral part of the firearm. An illumination source is provided that projects a narrow beam of light in a direction parallel to the weapon&#39;s bore-sight. When the light beam and bore-sight are properly aligned, the bullet or other type of projectile will hit on or very close to the location of the light beam on the target.  
         [0004]     Lasers are a preferred mechanism of generating light beams for sighting applications. Lasers can be focused into a narrow beam with a very small divergence angle, so that they produce a small bright spot on the target tens to hundreds of yards from the light source. As used herein the word “laser” is intended to include any form of a collimated light source.  
         [0005]     The control devices for activating and deactivating the laser sight may be located on various areas of the firearm such as on or near the handgrip, rifle stock, or located somewhere on the trigger guard, and are incorporated into the electronic circuit of the laser. These controls may be switches, waterproof buttons, levers, latches, or slides, etc., however, they may prove to be awkward and be distracting to a user when the user has to activate the laser sight. For example, the user may have to use one of his/her gripping fingers to press an activating button. Thus, the impulse to pull the trigger, which normally is implemented without physical displacement of the barrel, may impart an unexpected twist to the weapon when one of the gripping fingers has to hold or push a laser activator switch or button, thereby throwing the bullet off its intended course. This is particularly inconvenient to a user, such as a law enforcement officer, when suddenly confronted with a hostile and life threatening situation. The officer usually has to perform the following four steps when using a conventional laser-aimed weapon: 1) draw the weapon, 2) activate the laser, 3) aim, and if necessary, 4) fire.  
         [0006]     To bypass the manual activation of the laser sight, a tritium switch has been fitted into the trigger area of the weapon as described in U.S. Pat. No. 5,522,167. A vial containing the radioactive substance is mounted in the forward trigger guard housing and a photoelectric cell is mounted in the rear trigger housing so that it is aligned with the emission from the vial. Once the user picks up the weapon and places his/her finger on the trigger, the beam from the vial to the cell is interrupted and the laser sight module is activated. The tritium switch could be installed on any firearm that has a trigger guard and trigger.  
         [0007]     A mercury switch has also been incorporated into the laser&#39;s circuitry to alleviate a user&#39;s manual control of the laser sight as described in U.S. Pat. No. 5,177,309. The mercury switch is located, in the case of a pistol, in the handgrip of the firearm. The switch is responsive to the attitude of the weapon so as to be automatically activated, turns on the laser sight, when the weapon is leveled at a target, and deactivated, turns off the laser sight, when it is not leveled, e.g., when the firearm is substantially vertical in a belt holster.  
         [0008]     Both the tritium and mercury switches eliminate an entire step from an officer&#39;s list of activities needed to bring his/her weapon into action against a perpetrator. These switches, however, include substances that raise health and environmental issues.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention provides a control system to operate a laser in a sighting system for detecting a target. The control system is integrated in the laser sight&#39;s electronic circuitry and activates the laser by producing an electrical signal. The signal is generated when the system senses vibrations caused by motion.  
         [0010]     The above and other objects and advantages of the present invention will be made apparent from the accompanying drawings and the description thereof. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
         [0012]      FIG. 1  is an illustration of a motion detector.  
         [0013]      FIG. 2  is a circuit diagram of the circuitry included in the motion detector of  FIG. 1 .  
         [0014]      FIG. 3  is a representative schematic of a motion detector in a laser sight&#39;s circuitry.  
         [0015]      FIG. 4  is a timing diagram illustrating the electrical behavior of the circuitry of  FIG. 2 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     As noted in the Background section, many types of firearms have laser sights or modules either mounted on an exterior surface of the firearm or incorporated within the firearm itself. Some of these firearms have control buttons or switches to activate the laser sight on the exterior surface of the firearm. The user of the firearm has to manually activate the laser thus adding an extra step to fire the weapon which may be awkward in a hostile situation. Other firearms have automatic switches that eliminate the manual activation of the laser by the user. These switches, however, may pose health and environmental problems to the user and society as a whole. The present invention is a system that incorporates an environmentally friendly motion detector that activates a laser sight on a firearm, and allows the user of the firearm to more efficiently aim the weapon at a target.  
         [0017]     The motion detector  10  of the present invention is shown in  FIG. 1  which is described in U.S. Pat. No. 5,612,670, and is expressly incorporated by reference herein in its entirety. The motion detector  10 , also known as a mechanical shock detector, includes a printed circuit board  12  and optionally may be encased within a plastic housing formed of two halves  14  and  16 . The housing halves may be secured together by an adhesive or by screws  19  that also allow the detector to be mounted on a firearm such as the bottom of a pistol grip or on a rifle stock. The circuit board  12  is preferably manufactured using surface mount technology, thereby minimizing the size of the motion detector  10 . The circuit board  12  may be mounted in a laser sight assembly for a firearm or when encased within a plastic housing elsewhere on or within the weapon itself.  
         [0018]     The circuit board  12  includes a number of surface mounted components  18  such as resistors, capacitors, diodes, transistors, and an integrated circuit containing four operational amplifiers, as is more specifically detailed in  FIG. 2 . Also included is a strip  17  of piezoelectric material, a light-emitting diode (LED) D 4 , and a potentiometer RP 3 . The circuit board  12  is integrated into the laser sight&#39;s electronic circuitry by connectors that are known to one skilled in the art. An example of such circuitry is shown in  FIG. 3 .  
         [0019]     The motion detector  10  activates the laser sight of the firearm by producing an electric signal produced by the piezoelectric strip  17 . The strip  17  has piezoelectric crystals incorporated into its structure. The crystals generate a pulse of electricity in response to vibrations produced by motions which are sensed by the circuitry on the circuit board. For example, in the present invention the motion detector  10  will activate a laser sight on a pistol, or any other firearm with a laser sight, when the weapon is raised by the user to a horizontal position to take aim at a target. As described more below, if this electrical signal exceeds a threshold (which is preset by adjustment of corresponding potentiometer RP 3 ), the circuitry on circuit board  12  activates the laser for a predetermined amount of time, for example from about 10 to 30 seconds.  
         [0020]     Three terminals  20 ,  24  and  26  lead from the circuit board  12 . These terminals are connected to a power supply, such as the battery  30  for a laser, and a laser sight circuit. As discussed in more detail below, when a motion condition is triggered by circuit board  12 , signals on these terminals relay the motion condition to the laser sight circuit. Furthermore, light-emitting diode D 4  is illuminated while the laser is activated, thus providing a visual signal of a motion trigger, which can be used during installation when adjusting potentiometer RP 3  to select the appropriate threshold levels.  
         [0021]     Referring to  FIG. 2  and  FIG. 3 , the circuitry  13  on circuit board  12  of the motion detector  10  is configured for connection to a power supply such as is typically found to operate lasers. Power for the circuit board  12  is obtained from the laser&#39;s battery  30  via connections to terminal  24  and terminal  26 .  
         [0022]     As illustrated in  FIG. 2 , a circuit  13  in accordance with principles of the present invention is configured for connection to and interaction with a laser sight assembly. In accordance with principles of the present invention, terminal  20  is connected to the laser control  40 . Inside of circuit  13 , transistor Q 3  is connected between terminal  20  and ground. When transistor Q 3  is active, the corresponding terminal  20  is connected to ground, activating the laser sight circuit. When transistor Q 3  is not active, resistor R 20  pulls terminal  20  to the positive power supply voltage.  
         [0023]     Transistor Q 3  is activated by analog circuitry which processes electrical vibration signals produced by sensor  17 , which may be for example a piezoelectric strip available as part number 10027941 from Amp, P.O. Box 3608, Harrisburg, Pa. 17105.  
         [0024]     Sensor  17  is connected differentially across the input terminals of an operational amplifier  42 . Amplifier  42  produces a low-pass filtered version  60  ( FIG. 4 ) of the vibration signals from sensor  17  (low pass filtering is provided by capacitor C 3  and resistor R 5 , the values of which, when multiplied together, produce a time constant of approximately 3 milliseconds).  
         [0025]     The filtered output of amplifier  42  is fed to the non inverting inputs of operational amplifier  46 , which is wired as a comparator. The inverting input of amplifier  46  is connected to the wiper of potentiometer RP 3 .  
         [0026]     Thus, amplifier  46  compares the voltage of the filtered analog signal from amplifier  42  to a threshold voltage which is generated by adjusting potentiometer RP 3 . If the filtered vibration signal from amplifier  42  exceeds the threshold, the output of amplifier  46  saturates at the positive supply voltage.  
         [0027]     The output of amplifier  46  is not directly coupled to transistor Q 3 ; instead, the output of amplifier  46  is connected to a sample-and-hold circuit comprising two parallel diodes D 5 , a capacitor C 7  and a resistor R 19 . Operational amplifier  48 , which is wired as a comparator, compares the voltage of capacitor C 7  at its inverting input to a reference voltage at its non inverting input; the reference voltage is generated by resistors R 17  and R 18 , which are wired as a voltage divider and produce a voltage of approximately one-sixth of the power supply voltage.  
         [0028]     When the output of amplifier  46  is positive (indicating that the filtered vibration signal from amplifier  42  exceeds the threshold set by potentiometer RP 3 ), capacitor C 7  charges to a voltage near to the power supply voltage. Because this capacitor voltage exceeds one-sixth of the power supply voltage, the output of amplifier  48  saturates at the power supply voltage. Amplifier  48  is connected to transistor Q 3 ; thus, when amplifier  48  saturates at the power supply voltage, transistor Q 3  is activated, triggering the laser control  40  via terminal  20 .  
         [0029]     If the filtered vibration signal from amplifier  42  falls below the threshold set by potentiometer RP 3 , the output of amplifier  46  saturates at the ground voltage. In this situation, diodes D 5  turn off, and therefore capacitor C 7  remains charged near to the positive power supply voltage. Thus, even after the filtered vibration signal falls below the threshold, amplifier  48  will remain saturated at the power supply voltage, and transistor Q 3  will remain activated.  
         [0030]     If, however, the filtered vibration signal remains below the threshold set by potentiometer RP 3  for any period of time, capacitor C 7  will discharge through resistor R 19 . The rate of discharge is determined by the product of the values of resistor R 19  and capacitor C 7 , and has a time constant from about 10 to about 30 seconds. Thus, if the filtered vibration signal remains below the threshold for longer than the preset time constant, capacitor C 7  will discharge to a voltage less than one-sixth of the power supply voltage. When this occurs, amplifier  48  will as a result saturate at the ground voltage, and transistor Q 3  will deactivate and the laser will turn off.  
         [0031]     The activation of the laser  22  may be controlled by a laser control switch  40  as illustrated in circuitry  23  in  FIG. 3 . When the control switch  40  is in the on position, the laser  22  is in a continuous state of activation (continuously turned on) and deactivated (turned off) when the switch  40  is in the off position. When the switch  40  is in the auto position, the activation of the laser  40  is controlled by the motion detector  10 . The laser  22  is activated when the motion detector senses a vibration that creates an electrical signal that exceeds a preset threshold and deactivated after a predetermined time period.  
         [0032]     Referring to  FIG. 4 , in accordance with the forgoing, in response to mechanical shock producing a filtered vibration signal  60  from the piezoelectric strip  17  having a burst of large magnitude oscillation, the circuit of  FIG. 2  will produce an electrical ground connection on line  20 . (Trace  64  of  FIG. 4  illustrates logically the state of the transistor Q 3  which connects to the trigger  2  terminal  20 . An active transistor state, during which a ground connection is being made, is indicated by a high or logic “1” value in the trace  64  of  FIG. 4 ).  
         [0033]     As can be seen in  FIG. 4 , trigger terminal  20  will be connected (via transistor Q 3 ) to ground for a period beginning whenever the filtered vibration signal  60  exceeds threshold  52 , and continuing until the filtered vibration signal  60  has not exceeded threshold  52  for a period of time previously set.  
         [0034]     Other variations or embodiments of the invention will also be apparent to one of ordinary skill in the art from the above description. Therefore, various changes, modifications or alterations to these embodiments may be resorted to without departing from the spirit of the invention and the scope of the following claims.