Abstract:
An improved electric weapon immobilizes a target by conducting a current through an electrode and through the target. The weapon includes a circuit that outputs a pulse pattern having a first pulse, a second pulse of opposite polarity compared to the first pulse, and a period of no output between the first pulse and the second pulse. The period is in a range from 50 microseconds to 1000 microseconds. The electric weapon repeats the output of the pattern at a rate of 19 repetitions per second. A method for immobilizing a target is performed by an electric weapon. The method includes delivering a first pulse in a first polarity, operating a switch to reverse the polarity of delivery; and delivery the second pulse in a second polarity. The method may further include awaiting lapse of a period between delivery of the first pulse and delivery of the second pulse wherein the period is in the range of from 50 microseconds to 1000 microseconds.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a non-provisional patent application that claims the benefit of: (a) U.S. Patent Application Ser. No. 60/587,140, filed Jul. 13, 2004, by Kroll, entitled “Improved Trajectory Taser Style Device”; (b) U.S. Patent Application Ser. No. 60/587,142, filed Jul. 13, 2004, by Kroll, entitled “Multiple Voltage Taser Style Device”; and (c) U.S. Patent Application Ser. No. 60/587,141, filed Jul. 13, 2004, by Kroll, entitled “Improved Waveform For Taser Style Device”. Each of these U.S. Patent Applications is incorporated herein by reference. 

   FIELD OF THE INVENTION  
   This invention relates generally to the field or non-lethal weapons and more specifically to such a weapon having two projectiles for electrically immobilizing a live target for capture. 
   BACKGROUND  
   Beginning in the late 1970&#39;s, law enforcement agencies began to employ electric weapons as a firearm substitute in certain confrontational situations that could otherwise have justified the use of deadly force, for example against knife wielding assailants at close range. These agencies have also employed electric weapons successfully to avoid injury to peace officers, assailants, and innocent bystanders in situations where the use of conventional firearms would have been either impractical or unjustified. 
   The electric weapon&#39;s characteristic, near instantaneous, incapacitating power has been employed to disable an assailant holding jagged glass to a hostage&#39;s throat without any physical injury occurring to the hostage. It has also been used to prevent a raging parent from hurling his infant from a high rise, preventing a suicidal man from leaping from a high rise, and subduing unarmed combatants all without serious physical injury to the peace officer or assailant. 
   Currently manufactured ballistic weapons that output electrical pulses to immobilize and capture human and other animal assailants (e.g., electric weapons including TASER® electric weapons marketed by TASER International, Inc.) have a lower lethality than conventional firearms. An electric weapon launches a first electrically conductive dart and a second electrically conductive dart. Each of the darts remains connected to the weapon after launch by a first and a second electrically conductive wire, respectively. The launched darts strike a target and each dart couples to the target and remains coupled to the target for a period of time. Such coupling can be achieved by a first and a second barbed metallic (conductive) needle (each being positioned at a front of the first and second darts, respectively) the imbed into the target and remain imbedded in the target. Electrical pulses from a pulse generator on-board the weapon travel through the first wire to the first dart, from the first data through the target, and into the second dart. Next, the electrical pulses return to the weapon via the second wire. Thus, a complete circuit is formed of the pulse generator, the first and second wires, the first and second darts (and their respective first and second barbed metallic needles), and a target, e.g., a human, animal, device, or other such target. 
   It is the delivery of the electrical pulses through the portion of this circuit that comprises the target that results in the incapacitation of the target, provided the electrical pulses are selected to effect incapacitation. The nature of such pulses as heretofore employed is described, inter alia, in, for example, U.S. Pat. No. 7,102,870 to Nerheim, incorporated herein by reference. Electric weapons are described, inter alia, in, for example, U.S. Pat. Nos. 6,575,073 and 5,841,622 to McNulty and U.S. Pat. No. 6,636,412 to Smith, each incorporated herein by reference. McNulty describes an electrical discharge weapon with improved range and an electrical restraint device that outputs 14 to 17 pulses per second for a 3 to 5 second duration. Nerheim describes electronic disabling devices that output from 9 to 19 pulses per second for a 5 second duration or for a duration as long as the trigger switch is held “on”. Smith describes an apparatus for preventing locomotion that outputs 2 to 40, preferably, 5 to 15 pulses per second for a duration of 6 to 7 seconds. These current pulses through target tissue cause contraction of skeletal muscles and make the muscles inoperable, preventing use of the muscles in locomotion by the target. 
   The TASER International model X26 electric weapon launches two darts at substantially equal velocities of about 150 feet per second from a replaceable cartridge attached to the electric weapon. A relatively high voltage is impressed across the darts to conduct a stimulus current in a circuit through the target that may include one or more air gaps. The high voltage forms an arc across these air gaps for each pulse of the stimulus current. The model X26 electric weapon may be used without a cartridge by pressing terminals against the target. The same stimulus signal is used because one or more arcs through clothing may be required to deliver the current through the target. The stimulus current includes a monophasic pulse repeated at typically 17 or 19 pulses per second for 5 seconds. The pulses constitute a current of 2.1 milliamps, or 111 microcoulombs of charge per pulse at 19 pulses per second. Other known electric weapons provide a stimulus current that includes a monophasic pulse repeated at a rate from 5 to 40 pulses per second. The reciprocal of a pulse repetition rate defines a pulse repetition period that for rates 5, 17, 19 and 40 pulses per second defines periods of 200 milliseconds, 59 milliseconds, 53 milliseconds, and 25 milliseconds respectively. 
   The present invention advantageously addresses the above and other needs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     Various aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
       FIG. 1  is a functional block diagram of an electric weapon, according to various aspects of the present invention; 
       FIG. 2  is a cross section of a cartridge according to various aspects of the present invention; 
       FIG. 3  is a graphical analysis of the trajectories of the darts of the cartridge of  FIG. 2 ; 
       FIG. 4  is a process flow diagram for delivery of high voltage stimulus and low voltage stimulus, according to various aspects of the present invention; 
       FIG. 5  is a schematic diagram of a biphasic waveform generator, according to various aspects of the present invention; 
       FIG. 6  is a perspective plan view of an improved immobilization device, according to various aspects of the present invention, having arms in a loaded position; 
       FIG. 7  is a perspective plan view of the device of  FIG. 6  having arms in a firing position; 
       FIG. 8  is a graph of the response of a target to a split unipolar waveform; and 
       FIG. 9  is a graph of the response of a target to a biphasic waveform, according to various aspects of the present invention. 
     Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the presently contemplated best mode of practicing the invention is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. 
   An immobilization device may include a housing, a first electrically conductive dart, a second electrically conductive dart, a barrel, an electric circuit (such as an electrical pulse generating circuit) mounted in the housing, a safety mounted on the housing, a trigger mounted on the housing, and a cartridge. The cartridge contains at least the first electrically conductive dart (e.g., a dart comprising a barbed metallic needle, or other electrode) and the second electrically conductive dart (e.g., a dart comprising a barbed metallic needle, or other electrode). The cartridge contains means for firing each dart through the air in the direction toward a target, e.g., a human, animal or device. A powder charge, compressed air, and/or other such known source of ballistic propulsion may be utilized as the means for firing to fire the first dart and the second dart, and are well known in the art. Each of the first and second darts is coupled to the cartridge by a respective first or second electrically conductive wire. The first and second wires are typically sheathed in an insulating material, such as is known in the art, and are typically coiled in the cartridge prior to firing. 
   The safety is mounted on the housing of the device. The safety controls the activation of the weapon prior to squeezing of the trigger. The trigger is also mounted on the housing near the safety so that an operator can release the safety and squeeze the trigger in a short period of time. 
   In operation, the cartridge is activated and the first and second darts with their respective ones of the first and second wires are fired (deployed) by the means for firing, for example, expanding gasses acting upon the first and second darts from within the cartridge when an operator manually slides the safety in a selected direction to release the safety and then squeezes the trigger. The trigger serves to actuate the cartridge and thereby initiate the firing of the first and second darts by the means for firing. The first and second wires are carried by the first and second darts, respectively, from the cartridge upon firing. Upon firing, the first and second wires unwind and straighten as each of the first and second darts travels through the air in a direction toward the target. 
   After firing, a series of pulses is generated by the electric circuit (e.g., an electrical pulse generator) located within the housing. The pulses are carried to the target by the darts and wires. The pulse pass through the target and back to the weapon. 
   The pulses of electrical potential are selected to have a magnitude, duration, and pulse repetition period that result in an immobilization of the target (preferably, in accordance with some embodiments, without a permanent injury to the target), of preferably sufficient duration (e.g., 5 seconds) to allow the target to be otherwise constrained and to eliminate any threat the target poses to others or to property. 
   Upon impact of the darts with the target, a distance between the first dart and the second dart at their point of impact with the target defines a spread. A minimum spread for reliably disabling (immobilizing) the target upon application of the pulses discussed above, is presumed to be 7 inches for human targets. The minimum spread causes enough motor neurons to be affected by the pulses to assure immobilization of the target. 
   Heretofore, a first bore (or first exit bore) within the cartridge is positioned along a horizontal plane of the electric weapon (defined by the barrel), and a second bore (or second exit bore) is positioned vertically below the first bore at an acute angle below the horizontal plane. The first dart is positioned within the first bore prior to firing, and the second dart is positioned within the second bore prior to firing. Upon firing, the darts leave their respective bores and continuously spread an increasing distance from each other as they approach the target. 
   This method of establishing the dart&#39;s divergence from each other has a serious drawback: it greatly limits an electric weapon&#39;s range. Both minimum and maximum ranges are limited. For example, the bore axes of heretofore known electric weapons intersect an angle of 12 degrees, with some models with 8 degrees. Using the 12 degree angle for illustrative purposes, for every 5 feet the darts travel toward the target, the darts will spread approximately 1 foot further apart from each other. If the darts contact a target within 2.8 feet along the flight path from the electric weapon, the resulting spread would not likely be effective for disabling the target. The presumed minimum effective spread of 7 inches between the darts would not yet have been achieved. If the darts contact the target at a distance of 15 feet from the electric weapon, the darts are spread approximately 3 feet apart and would not likely both embed in a human or small animal target to complete an electric circuit. Thus, the heretofore known electric weapons&#39; best operational range is from 3 to 12 feet from the electric weapon. 
   The spread between the darts at close range may be increased by increasing an angle between the first and second bores, i.e., by increasing an angle between the axes of the first and second bores, e.g., by increasing the number of degrees below horizontal of the second bore axis. This, however, causes a corresponding undesired increase in the spread of the darts at longer ranges. 
   Decreasing the spread between the darts at longer ranges decreases the darts&#39; spread at closer ranges. Thus, long range effectiveness is sacrificed for close range effectiveness and vice versa. The known electric weapons, therefore, have limited tactical application, due to these constraints on operational range. 
   When the darts strike a human target, an electric current flows between the darts and through the target for a brief period. The current may include short, high voltage pulses having low average current, and low average power. As a result of a physiological effect of the pulses of electric current upon the nerves for the skeletal muscle and/or the nerves for pain, the target experiences a temporary ambulatory incapacitation. 
   Once the darts have been deployed and the electric circuit is no longer delivering electric pulses through the target, the operator disconnects the cartridge from the barrel. The operator then manually loads into the barrel a new cartridge containing a new pair of darts and coiled wires. 
   A TASER model X26 performs the functions discussed above. Referring to  FIG. 1 , an improved electric weapon  100  includes the functional blocks of the TASER model X26, adapted for impendence measuring and testing, and reversing output polarity. Specifically, electric weapon  100  includes circuitry  114 , cartridge  120 , darts  122  and  124 , and terminals  132  and  134 . Circuitry  114  includes battery  101 , microcontroller  102 , safety  103 , trigger  104 , display  105 , and pulse generator  110 . 
   An immobilization device is improved upon by use of a cartridge  120  as in  FIG. 2 , wherein the angle  205  of the first bore  210  containing the first dart  122  and the angle  206  of the second bore  212  containing the second dart  124 , relative to the horizontal plane  220  as defined by the barrel, are selected as follows. The first dart  122 , located above the second dart  124 , is angled above the horizontal plane  220 . The second dart  124  is angled in a direction below the horizontal plane  220 . 
   In operation, the first dart  122  will follow a parabolic trajectory  300  of  FIG. 3  when fired (deployed), first rising above the horizontal plane  220 , and then descending below the horizontal plane  220  under the influence of gravitational force (provided sufficient distance from the electric weapon is achieved prior to impact with the target). A lower velocity of the first dart  122  will cause the first dart  122  to descend much sooner. For example, with 100 feet per second velocity, the first dart  122  will cover 20 feet in 0.2 seconds. With gravity, the first dart  122  will fall 16t 2 =16*(0.2) 2 =0.64 ft=7.7 inches. 
     FIG. 3  graphically illustrates the improved trajectory for the inventive embodiment. Depicted are a first dart trajectory  300  and a second dart trajectory  302 . The first dart trajectory  300  corresponds to the path of a first dart  122  as it travels to a target. The second dart trajectory  302  corresponds to the path of a second dart  124  as it travels to the target. The first dart trajectory  300  has an enhanced parabolic shape due to a launch angle  205  of 4 degrees depicted in  FIG. 2  (i.e., above horizontal  220 , as defined by a barrel) and a reduced velocity. According to various aspects of the present invention, the first dart  122  velocity is reduced in relation to the second dart  124  velocity in order to create an enhanced parabolic trajectory  300 . A velocity of the first dart may be 63 feet per second when the velocity of the second dart is 150 feet per second. 
   A lower initial velocity of the first dart results in a greater effect on the acceleration by vertical gravitational forces acting upon the first dart  122 , thereby creating the substantially more pronounced parabolic shape to the trajectory  300  of the first dart  122 . The second dart  124  is positioned at a launch angle  206  so to maintain proper spacing with the first dart  122 . The first dart&#39;s launch angle  205  and second dart&#39;s launch angle  206  create a dart separation of 0.6 feet (7.2 inches) at a distance of 4 feet from the weapon. The dart spacing  304  at 21 feet from the weapon is only 1.4 feet and is half of the conventional dart spacing. 
   In operation, the improved dart bore angles  205  and  206  are selected to increase the effectiveness range of the weapon  100  by increasing the spacing between the first dart  122  and the second dart  124  at short distances by maintaining 8 degrees of total separation between the first and second dart trajectories  300 ,  302  while decreasing the spacing, at long distances from the weapon, between the first and second trajectories  300 ,  302  due to the parabolic shape of the first trajectory  300 . 
   Referring to  FIG. 4 , a flow diagram is shown depicting a method  400  for delivery of high voltage and low voltage waveforms. The method shown includes launching ( 402 ) a first dart  122  and a second dart  124 , delivering ( 404 ) a low voltage waveform, and measuring ( 406 ) an impedance (Z). The method  400  may be performed by the electric weapon  100  of  FIG. 1 . 
   In operation, first dart  122  and second dart  124  are deployed ( 402 ) along the trajectories  300 ,  302  illustrated in  FIG. 3  or a conventional trajectory. The first dart  122  and the second dart  124  strike (impact) the target creating a complete circuit (as described hereinabove) to which a low voltage waveform is initially applied ( 404 ) by the electrical pulse generator  110  by the generation of a pulse of low electrical potential. This pulse of low electrical potential causes a pulse of electric current to begin to flow through the first and second wires, through the first and second darts, and through the target. Next, an impedance (Z) is measured ( 406 ) via an output current delivered back to the electrical pulse generator  110  and microcontroller  102 . If the measured impedance (Z) is less than 20 ohms ( 408 ), a short is suspected and the operator is notified ( 410 ,  105 ) to eject the cartridge and insert a new cartridge, i.e., to reload ( 412 ) the electric weapon ( 100 ). Once the darts  122 ,  124  have been deployed and the electric circuit  110  is no longer delivering electric pulses through the target, the operator disconnects the cartridge  120  from the barrel. The operator then manually loads into the barrel a new cartridge  120  containing new darts and coiled wires. 
   If measured impedance (Z) is greater than 1000 ohms ( 408 ) a lack of direct contact is suspected and high voltage circuitry  110  initiates and delivers ( 414 ) a pulse train of higher voltage pulses to the target to jump through clothing ( 416 ). If measured impedance (Z) is within the range of 20 to 1000 ohms, then the electric weapon  100  continues to deliver ( 418 ) the low voltage waveform and to measure impendence ( 406 ) during delivery ( 420 ,  422 ) of the lower voltage waveform. 
   Referring next to  FIG. 5 , shown is a schematic diagram of a biphasic waveform generator, part of pulse generator  110 . Circuit  502  generates a series of pulses. Switches  512 ,  518  are closed to provide a positive phase pulse. Switches  512  and  518  are opened and switches  514  and  516  are closed to provide a negative phase pulse. Switches  510  (including  512 ,  514 ,  516  and  518 ) may be controlled by microcontroller  102 . 
   Referring next to  FIGS. 6 and 7 , shown in an improved immobilization weapon  600  with flip-out arms. Illustrated are a first arm  606 , a second arm  608 , a barrel  604 , a mounting mechanism  610 ,  612 , a first bore  607 , and a second bore  609 . The barrel  604  supports the first arm  606  and the second arm  608 , each rotatably mounted  610 ,  612  on the barrel  604 . The mounting mechanism  610 ,  612  secures the arms  606  and  608  to the barrel  604  and serves as a hinge. The first arm  606  contains the first bore  607 . The first bore  607  houses the first dart. The second arm  608  contains the second bore  609 . The second bore  609  contains the second dart. 
   In operation, the mounting mechanism  610 ,  612  allows for the rotation of the first and second arms within a horizontal plane, defined by the barrel, from a loaded position parallel to the barrel ( FIG. 6 ) to a firing position ( FIG. 7 ). 
   Referring next to  FIG. 7 , shown is an immobilization weapon  600  with flip-out arms in the firing position. Depicted are the first and second arms  606 ,  608 , barrel  604 , the first and second bore  607 ,  609 , and the mounting mechanism  610 ,  612 . Illustrated are the first arm  606  and the dart arm  608  rotated to the full extension. The first bore  607  housing the first dart and the second bore  609  housing the second dart are horizontally parallel to one another. The first dart and second dart are deployed from their respective bores in any conventional manner. The separation  706  between the axis  702  for bore  607  and the axis  704  of bore  609  is determined, in part, by the horizontal distance between the first bore  607  and the second bore  609 , and a length of the arms. The minimum spread is achieved by selecting the length of the first arm  606 , and the second arm  608 . 
   In operation of an electric weapon according to  FIGS. 1 ,  6 , and  7 , when the safety  103  is released, the arms  606  and  608  rotate to a position substantially normal to the barrel  604  of the weapon. The first and second arms  606  and  608  are then locked into place, the first bore  607  and the second bore  609  are aligned, i.e., their bore axes  702  and  704  are substantially parallel with one another, and the weapon is ready to deploy the darts. Upon firing (which is initiated, as described above, upon the actuation or pulling of the trigger  104 ,  603 ), the first dart is propelled from the first bore  607  by the means for firing, and the second dart is propelled from the second bore  609  by the means for firing. As the darts leave bores  607  and  609 , the darts continuously travel in a horizontally parallel relationship as they approach the target. The spacing  706  between the darts is held consistent from deployment until contact with the target for any desired range. 
   Referring next to  FIG. 8 , shown is the response to a split unipolar waveform. The graph depicts a superposition of the applied voltage waveform  802 ,  804 , motor neuron potential response  806 ,  808 , and cardiac membrane potential response  810 ,  812 . Each waveform is respectively scaled for clarity of presentation. The applied voltage waveform is split into a first rectangular pulse  802  and a second rectangular pulse  804 , each with duration of 50 microseconds respectively. 
   Referring next to  FIG. 9 , shown is the response to a biphase waveform according to various aspects of the present invention. The graph depicts a superposition of the applied voltage waveform  902 ,  904 , motor neuron potential response  906 ,  908 , and cardiac membrane potential response  910 ,  912 . Each waveform is respectively scaled for clarity of presentation. The applied voltage waveform is split into a first rectangular pulse  902  and a second rectangular pulse  904  each with duration of 50 microseconds respectively. The first applied voltage pulse  902  and the second applied voltage pulse  904  are of opposite polarity. The spacing between the first pulse and the second pulse is 100 microseconds. As shown in  FIG. 9 , the motor neuron time constant is 100 microseconds and the cardiac membrane time constant is 3.5 milliseconds. 
   In operation, for the first pulse  902  the motor neuron potential response  906  and the cardiac membrane potential response  910  behave in a manner similar to that shown in  FIG. 8 . For the second pulse  904 , the motor neuron potential response  908  is symmetrical to the motor neuron potential response  906 , but the cardiac membrane potential response  912  exponentially approaches zero. 
   A method of immobilizing a target may include delivering a multiple polarity waveform of electrical current so that minimal net charge remains on cardiac cell membranes of the target. 
   An electric weapon that outputs a unipolar pulse of a given pulse duration may be improved by modifying the weapon to output two unipolar pulses of equal charge and opposite polarity. The shape of each pulse may be arbitrary. The pulses may have different shapes. The pulses may be separated by 50 microseconds to 1000 microseconds, preferably less than 500 microseconds. For pulses of 50 microseconds duration, a separation of 100 microseconds may be used. 
   The present invention, in some embodiments, provides an improvement on the performance and safety of an immobilization weapon. It will be further appreciated that by solving the problems created by electrically conductive dart spacing, multiple voltages, and cardiac membrane potential, the present embodiments are capable of reducing the potential cardiac risk to the target along with increasing the rate of success of direct contact. 
   While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.