Patent Publication Number: US-9429396-B2

Title: Electrode for electronic weaponry that dissipates kinetic energy

Description:
FIELD OF THE INVENTION 
     Embodiments of the present invention relate to electronic weaponry, electronic control devices, deployment units for electronic weaponry, electrodes used in deployment units, and methods of manufacturing such electrodes that provide a current through a human or animal target. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Embodiments of the present invention will now be further described with reference to the drawing, wherein like designations denote like elements, and: 
         FIG. 1  is a functional block diagram of an electronic weapon according to various aspects of the present invention; 
         FIG. 2  is a functional block diagram of a circuit that includes a target and an electrode of the electronic weapon of  FIG. 1 ; 
         FIG. 3A  is a functional block diagram of an electrode of the electronic weapon of  FIG. 1 ; 
         FIG. 3B  is a functional block diagram of another electrode for the electronic weapon of  FIG. 1 ; 
         FIG. 3C  is a functional block diagram of still another electrode for the electronic weapon of  FIG. 1 ; 
         FIG. 4  is a side plan view of an implementation of the electronic weapon of  FIG. 1  a moment after the launch of two electrodes according to any of  FIGS. 3A, 3B, and 3C ; 
         FIG. 5  is a cross-section view of the deployment unit of the electronic weapon of  FIG. 4 ; 
         FIG. 6  is a cross-section view of an electrode in an implementation according to  FIG. 3A ; 
         FIG. 7  is a view of the rear face of the electrode of  FIG. 6 ; 
         FIG. 8  is a perspective view of an electrode in another implementation according to  FIG. 3B ; 
         FIG. 9  is a perspective view of the rear portion of the electrode of  FIG. 8 ; 
         FIG. 10  is a perspective view of an electrode in still another implementation according to  FIG. 3C ; 
         FIG. 11  is a cross-section view of the electrode of  FIG. 10 ; 
         FIG. 12  is a perspective view of a portion of the electrode of  FIG. 10 , fully assembled; 
         FIG. 13  is a perspective view of a front portion of the electrode of  FIG. 10  prior to completing assembly; and 
         FIG. 14  is a perspective view of a rear portion of the electrode of  FIG. 10  as seen prior to assembly onto the front portion of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     U.S. patent application Ser. No. 12/983,163 filed Dec. 31, 2010, now U.S. Pat. No. 8,896,982 and U.S. patent application Ser. No. 14/301,594 filed Jun. 11, 2014 are incorporated herein by reference thereby making their disclosures a part of this application. 
     An electronic weapon, according to various aspects of the present invention, delivers a current through a human or animal target to interfere with locomotion by the target. An important class of electronic weapons launch at least one tethered electrode (e.g., dart, probe) toward a target to position the electrode in or near target tissue. A respective filament (e.g., wire with or without insulation) extends from the electronic weapon to each electrode at the target, thereby tethering the electrode to the electronic weapon. One or more electrodes may form a circuit through a target. The circuit conducts the stimulus signal. The circuit&#39;s return path may be through ground, through one or more additional tethered electrodes, or through a conductive path (e.g., liquid, plasma) formed by the electronic weapon to the target. The electronic weapon provides a stimulus signal (e.g., current, pulses of current) through, inter alia, the filament, the electrode, and the target to interfere with locomotion by the target. Interference includes causing involuntary contraction of skeletal muscles to halt voluntary locomotion by the target and/or causing pain to the target to motivate the target to voluntarily stop moving. 
     Conventional stimulus signals may be used. For example, a stimulus signal may comprise about 19 current pulses per second at a duty cycle less than 1/400, repeated for a period of from 5 to 30 seconds to facilitate arrest of the target or escape from the target. 
     An electronic weapon, according to various aspects of the present invention, may include a launch device and one or more field replaceable deployment units mounted to the electronic weapon. Each deployment unit may include expendable (e.g., single use) components (e.g., tether wires, electrodes, propellant), and storage cavities (e.g., bores, chambers). 
     A tethered electrode is an assembly of a filament (e.g., cord, wire, conductor, group of cords and/or conductors) and an electrode at least mechanically coupled to an end portion of the filament. A portion of the filament near the other end of the filament is at least mechanically coupled to the deployment unit and/or the launch device (e.g., one end fixed within the deployment unit), generally until the deployment unit is removed from the electronic weapon. As discussed below, mechanical coupling may facilitate electrical coupling of the launch device and the electrode prior to and/or during operation of the electronic weapon. 
     A launch device of an electronic weapon launches at least one tethered electrode of the electronic weapon toward a target. As the electrode travels toward the target, the electrode deploys (e.g., pulls) a length of filament from storage within the deployment unit. The filament trails the electrode. After launch, the filament spans (e.g., extends, bridges, stretches) a distance from the deployment unit to the electrode that is generally positioned in or near a target. 
     Electronic weapons that use tethered electrodes, according to various aspects of the present invention, include hand-held devices, apparatus fixed to buildings or vehicles, and stand-alone stations. Hand-held devices may be used in law enforcement, for example, deployed by an officer to take custody of a target. Apparatus fixed to buildings or vehicles may be used at security checkpoints or borders, for example, to manually or automatically acquire, track, and/or deploy electrodes to stop intruders. Stand-alone stations may be set up for area denial, for example, as used by military operations. Conventional electronic weapons such as the model X26 electronic control device and Shockwave™ area denial unit, each marketed by TASER International, Inc., may be modified to implement the teachings of the present invention by replacing the conventional deployment units with deployment units having electrodes as discussed herein. 
     An electrode, according to various aspects of the present invention, provides a mass for launching toward a target. The intrinsic mass of an electrode includes a mass that is sufficient to fly, under force of a propellant, from a launch device to a target. The mass of the electrode includes a mass that is sufficient to deploy (e.g., pull, uncoil, unravel, draw) a filament from storage and/or pay out a filament from storage on or in the electrode. The mass of the electrode is sufficient to deploy a filament behind the electrode while the electrode flies toward a target. The mass of the electrode deploys the filament from storage and behind the electrode in such a manner that the filament spans a distance between the launch device and the electrode positioned at a target. The mass of an electrode is generally insufficient to cause serious blunt impact trauma to a target. In one implementation, the mass of an electrode that draws a filament from storage in a deployment unit is in the range of 2 to 3 grams, preferably about 2.8 grams. 
     An electrode provides a surface area for receiving a propelling force to propel the electrode away from a launch device and toward a target. Movement of the electrode away from the launch device is limited by aerodynamic drag and by a resistance force (e.g., tension in the filament) that resists deploying a filament from storage and pulling the filament behind the electrode in flight toward a target. 
     A forward portion of an electrode may be oriented toward a target prior to launch. Upon launch and/or during flight from the launch device toward the target, the forward portion of the electrode may orient toward the target. An electrode may have an aerodynamic form for maintaining the forward portion of the electrode oriented toward a target. The aerodynamic form of an electrode provides suitable accuracy for hitting the target. 
     An electrode includes a shape for receiving a propelling force to propel the electrode toward a target. A shape of an electrode may correspond to a shape of a portion of the launch device or deployment unit that provides a propelling force to propel the electrode. For example, a cylindrical electrode may be propelled from a cylindrical tube of a deployment unit. During a launch of an electrode by expanding gas, the electrode may seal the tube to accomplish suitable acceleration and muzzle velocity. A rear face of the cylindrical electrode may receive substantially all of the propelling force. 
     An electrode may include a substantially cylindrical overall shape. Prior to launch, such an electrode is positioned in a substantially cylindrical tube slightly larger in diameter than the electrode. A propelling force (e.g., rapidly expanding gas) is applied to a closed end of the tube. The force pushes against a rear portion of the electrode to propel the electrode out of an open end of the tube toward a target. 
     An electrode includes a shape and a surface area for aerodynamic flight for suitable accuracy of delivery of the electrode across a distance toward a target, for example, about 15 to 35 feet from a launch device to a target. An electrode may rotate in-flight to provide spin stabilized flight. An electrode may maintain its pre-launch orientation toward a target during launch, flight to, and impact with a target. 
     An electrode or major portion of an electrode may have a conical or frustoconical shape (e.g., cone, golf tee, series of axially nested cones) with the base of the shape receiving the propelling force. 
     On impact, an electrode mechanically couples to a target. Mechanical coupling includes penetrating target clothing and/or tissue, resisting removal from clothing and/or tissue, remaining in contact with a target surface (e.g., tissue, hair, clothing, armor), and/or resisting removal from the target surface. Coupling may be accomplished by piercing, lodging (e.g., hooking, grasping, entangling, adhering, gluing), and/or wrapping (e.g., encircling, covering). An electrode, according to various aspects of the present invention, includes structure (e.g., hook, barb, spear, glue ampoule, tentacle, bolo) for mechanically coupling the electrode to a target. A structure for coupling may penetrate a protective barrier (e.g., clothing, hair, armor) on an outer surface of a target. 
     An electrode may include an integral structure or separate part functioning as a spear (e.g., pointed shaft, needle). The spear penetrates target clothing and/or tissue up to the length of the spear (e.g. up to a face of the electrode). Penetration is arrested by friction (e.g., contact of the spear with target clothing or tissue, abutment of a face of the electrode and the target). A spear may extend away from a face of the electrode toward the target. The spear may include one or more barbs for increasing the strength of the mechanical coupling of the electrode to the target. The barbs may be arranged to accomplish suitable mechanical coupling at various lengths of penetration of clothing and/or tissue. 
     An electrode is mechanically coupled to a filament to deploy the filament from storage and to extend the filament from the launch device to the target. Mechanical coupling includes coupling a filament and an electrode with sufficient strength to retain the coupling during manufacture, prior to launch, during launch, after launch, during mechanical coupling of the electrode to a target, and while delivering a stimulus signal to a target. Mechanical coupling may be accomplished by confining the filament between surfaces of an electrode and/or confining the filament within a portion of the electrode (e.g., establishing a suitable stiction between a portion of the filament and one or more surfaces of an electrode). Confining may include enclosing, holding, retaining, maintaining mechanical coupling, and/or resisting separation. Confining may be accomplished by preventing or resisting movement or deformation (e.g., stretching, twisting, bending) of the filament. As discussed below, placing the filament in an interior and affixing a spear over the interior in one implementation confines the filament to the interior. 
     An electrode facilitates electrical coupling of the launch device and the target. Electrical coupling generally includes a region or volume of target tissue associated with the electrode (e.g., a respective region for each electrode when more than one electrode is used). According to various aspects of the present invention, one or more structures of the electrode accomplish lower current density in the region or volume compared to prior art electrodes. 
     For each electrode, electrical coupling may include placing the electrode in contact with target tissue (e.g. touching, inserting) and/or ionizing air in one or more gaps between the launch device, the deployment unit, the filament, the electrode, and target tissue. For example, a placement of an electrode with respect to a target that results in a gap of air between the electrode and the target does not electrically couple the electrode to the target until ionization of the air in the gap. Ionization may be accomplished by a stimulus signal that includes, at least initially, a relatively high voltage (e.g., about 25,000 volts for one or more gaps having a total length of about one inch). After initial ionization, the electrode remains electrically coupled to the target while the stimulus signal supplies sufficient current and/or voltage to maintain ionization. Ionization may not be needed, for instance when contact is accomplished by spreading involving direct conduction from a filament to the target. 
     Assembly of a tethered electrode, according to various aspects of the present invention, is reliably accomplished in less time and with fewer and/or different operations than employed by prior art techniques. Manufacturing cost savings may result. 
     An electrode for use with a deployment unit and/or an electronic weapon, according to various aspects of the present invention, performs the functions discussed above. For example, any of electrodes  142 ,  143 ,  600 ,  800 , and  1000  of  FIGS. 1-14  may be launched from weapon  100  toward a target to establish a circuit with the target to provide a stimulus signal through the target. 
     Electronic weapon  100  of  FIG. 1  includes launch device  110  and deployment unit  130 . Launch device  110  includes user controls  112 , processing circuit  114 , power supply  116 , and signal generator  118 . In one implementation, launch device  110  is packaged in a housing. The housing may include a mechanical and electrical interface for a deployment unit  130 . Conventional electronic circuits, processing circuit programming, propulsion technologies, and mechanical technologies may be used, suitably modified, and/or supplemented as discussed herein. 
     A user control is operated by a user to initiate an operation of the weapon. User controls  112  may include a trigger, a manual safety, and/or a touch screen user interface operated by a user. When user controls  112  are packaged separately from launch device  110 , any conventional wired or wireless communication technology may be used to link user controls  112  with processing circuit  114 . 
     A processing circuit controls many if not all of the functions of an electronic weapon. A processing circuit may initiate a launch of one or more electrodes responsive to a user control. A processing circuit may control an operation of a signal generator to provide a stimulus signal. For example, processing circuit  114  receives a signal from user controls  112  indicating user operation of the weapon to launch an electrode and provide a stimulus signal. Processing circuit  114  provides a launch signal  152  to deployment unit  130  to initiate launch of one or more electrodes. Processing circuit  114  may provide a signal to signal generator  118  to provide the stimulus signal to the launched electrodes. Processing circuit  114  may include a conventional microprocessor and memory that executes instructions (e.g., processor programming) stored in memory. 
     A power supply provides energy to operate an electronic weapon and to provide a stimulus signal. For example, power supply  116  provides energy (e.g., current, pulses of current) to signal generator  118  to provide a stimulus signal. Power supply  116  may further provide power to operate processing circuit  114  and user controls  112 . For hand held electronic weapons, a power supply generally includes a battery. 
     A signal generator provides a stimulus signal for delivery through a target. A signal generator may reform energy provided by a power supply to provide a stimulus signal having suitable characteristics (e.g., ionizing voltage, charge delivery voltage, charge per pulse of current, current pulse repetition rate) to interfere with target locomotion. A signal generator electrically couples to a filament to provide the stimulus signal through the target as discussed above. For example, signal generator  118  provides a stimulus signal to tethered electrodes  142 - 143  of deployment unit  130  via their respective filaments  140 - 141 . Signal generator  118  is electrically coupled via stimulus interface  150  to filaments stored in deployment unit  130 . The stimulus signal may consist of from 5 to 40 pulses per second, each pulse capable of ionizing air, each pulse delivering after ionization (if needed) about 80 microcoulombs of charge through a human or animal target having an impedance of about 400 ohms. 
     A deployment unit (e.g., cartridge, magazine) receives a launch signal from a launch device to initiate a launch of one or more electrodes and a stimulus signal to deliver through a target. A spent deployment unit may be replaced with an unused deployment unit after some or all electrodes of the spent deployment unit have been launched. An unused deployment unit may be coupled to the launch device to enable additional electrodes to be launched. A deployment unit may receive, via an interface, signals from a launch device to perform the functions of a deployment unit. 
     For example, deployment unit  130  may include one or more cartridges  132 - 134 . Each cartridge  132  ( 134 ) may include one or more filaments  140  ( 141 ), one or more electrodes  142  ( 143 ), and one or more propellants  144  ( 145 ). A deployment unit stores a filament for each electrode or group of electrodes. Each filament mechanically couples to an electrode or group of electrodes as discussed herein. Via launch signal  152 , processing circuit  114  initiates activation of propellant  144  ( 145 ) for one or more selected cartridges. Propellant  144  ( 145 ) propels one or more electrodes  142  ( 143 ) toward a target. Each electrode is coupled to deploy a respective filament from storage. As each electrode flies toward the target, each electrode deploys its respective filament out from its storage. Signal generator  118  provides the stimulus signal through the target via stimulus interface  150  and the filaments coupled to launched electrodes  142  ( 143 ). 
     Each propellant may serve to launch any number of electrodes. For instance, a deployment unit formed as a replaceable cartridge may include a housing, an electrical interface, two electrodes, one propellant for launching the two electrodes, and two filaments, one for each electrode. 
     An electrode, according to various aspects of the present invention, may perform one or more of the following functions in any combination: binding the filament to the electrode, deploying the filament, mechanically coupling the electrode to a target, enabling conduction of the stimulus current from the filament through the target, spreading a current density with respect to a region of target tissue, and diffusing a current into a volume of target tissue. Enabling conduction includes ionizing, spreading, and/or diffusing. Enabling conduction, may include ionization along or through insulative and/or composite material of one or more portions of the electrode. Enabling conduction may include ionization along or through insulative and/or composite material external to the electrode. Insulative materials include any material or substance (e.g., gas, liquid, solid, aggregation, suspension, composite, alloy, mixture) that presents, at any time or times, a relatively high resistance to current of the stimulus signal. Composite materials include insulative materials combined with conductive particles, layers, or fibers. 
     In operation with a target, an electrode conducts current in a circuit that includes the target and a signal generator. For example, circuit  200  of  FIG. 2  includes filament  140 , electrode  142 , target tissue  202 , and return path  204 . Return path  204  in one implementation includes a conductor common to the signal generator and the target (e.g., earth). The return path in another implementation, not shown, includes a second tethered electrode (e.g.,  134 ). Current of any conventional polarity or polarities may flow in one or more directions on any of the lines shown in  FIG. 2  at various times. 
     An electrode has mass, shape, and surfaces for being attached to a filament, for being propelled, and for deploying the filament to a target, as discussed above. Conventional mass, shape, and surfaces may be employed. For example, an electrode may have a substantially cylindrical shape, an interior with surfaces that abut and/or grip a filament, and external surfaces with suitable aerodynamic properties for efficient propulsion and accurate flight to a target. An electrode may employ conductive, resistive, composite and/or insulative material on an intended path of conduction or propagation of stimulus current. An electrode may employ resistive, insulative, and/or composite material to diminish stimulus current conduction on undesired paths. An electrode may be rigid. To avoid breaking on impact, an electrode may have portions designed to flex to absorb energy of impact and thereby reduce the risk of breakage. Conventional metal and/or plastic fabrication technologies may be used in the manufacture of an electrode as discussed herein. Plastics may be filled with other materials (e.g., conductive particles, fibers, layers) to form composite materials uniformly or in suitable portions of a part. 
     An electrode may have any size and shape known in the art for suitably binding a filament and deploying a filament (e.g., substantially spherical, substantially cylindrical, having an axis of symmetry in the direction of flight, bullet shaped, tear drop shaped, substantially conical, golf tee shaped). In various implementations, an electrode may be formed of conductive, resistive, insulative, and/or composite materials, as discussed above. If insulative, a body portion of an electrode (i.e., all structures except those functioning as a spear, target retainer, or tip) may comprise composite material and/or be coated with insulative material. 
     A spear may perform mechanical coupling and/or be activated as discussed above. A spear may have any size and shape known in the art for suitably piercing material and/or tissue of a target, lodging in material and/or tissue of a target, and forming an ionized path from the tip of the spear to target tissue. In various implementations, a spear may be formed of conductive, resistive, insulative, and/or composite materials. A spear may be partially or entirely formed of a material that electrically insulates. When insulative, the electrode may comprise composite material and/or be coated with insulative material. Activation and use of a shaft and/or tip may reform paths along and/or through the insulative or composite material. 
     An insulator may be of a type (e.g., thickness, material, structure) that electrically insulates the spear against a current having a voltage below a threshold, but fails to insulate the spear against a current having a voltage above the threshold. An insulator may be formed (e.g., shaped, applied, positioned, removed, partially removed, cut) to establish a likely location on the spear where the insulator may fail to insulate against a current having a voltage above a threshold. An insulator may define a series of gaps between conductors of the spear or conductive portions of the spear. The gaps may act as switches operative to conduct in response to the applied voltage of the stimulus signal. 
     A tip (e.g., point, cone, apex comprising acute angles between faces, end of a shaft of relatively small diameter) operates to pierce an outer surface (e.g., layer) of a target and/or target tissue. A tip of a spear facilitates mechanical coupling by piercing and lodging. A tip when insulated may operate as a gap or switch interfering with current flow (e.g., blocking) until a threshold voltage breaks down the insulator and/or permits ionization near the tip followed by current flow through the tip. 
     A barb operates to lodge (e.g., retain) an electrode in clothing, armor, and/or tissue of a target to retain a mechanical coupling between the barb and the target. A barb portion of a spear resists mechanical decoupling (e.g. separation or removal from the target). A spear may include a barb near the tip. A spear may include a plurality of barbs arranged at increasing distance from the tip. A barb may include a continuous surface of the spear (e.g., a helical channel or ridge, a screw thread or channel, a surface having an undulation that increases friction between the barb and the target. 
     According to various aspects of the present invention, an electrode may comprise several structures that are coupled together to complete assembly of the electrode. These structures, when independent objects, are herein called parts, as opposed to portions of the same object. Receiving and conducting the stimulus signal is herein called activation. 
     A functional block diagram of an electrode, according to various aspects of the present invention, illustrates functional and structural cooperation. A carrying part and a piercing part may be mechanically coupled together. A carrying part carries a filament and/or retains a filament. A piercing part pierces clothing and/or tissue of a target to mechanically couple an electrode to a target. As shown in  FIG. 3A , electrode  142  performs mechanical and electrical functions discussed above. Electrode  142  of  FIG. 3A  may be activated via filament  140  (not shown) with current to and/or from signal generator  118 . Electrode  142  may be activated with current to and/or from target tissue  202  (not shown). Currents may pass via one or more paths through electrode  142  and via one or more paths through target tissue  202 . 
     Electrode  142  of  FIG. 3A  includes carrying part  302  and piercing part  304 . Carrying part  302  includes x-fastener  312 , filament retainer  314 , and shaft positioner  316 . Piercing part  304  includes y-fastener  322 , filament positioner  324 , and spear  306 . Spear  306  includes shaft  332 , target retainer  334 , and tip  336 . The total mass of electrode  142  may be distributed between carrying part  302  and piercing part  304  to accomplish desired deployment behavior and target retaining behavior. Conventional ballistics analysis techniques may be used. 
     A carrying part mechanically couples to a piercing part. For example, carrying part  302  includes x-fastener  312 . Piercing part  304  includes y-fastener  322 . The x-fastener  312  and y-fastener  322  represent mating fasteners of conventional technologies. Any fastening technology may be used (e.g., threading, snapping, hook and loop, friction fit, bayonet, latching). According to various aspects of the present invention, x- and y-fasteners may comprise surfaces suitable for any joining technology (e.g., gluing, welding, sonic welding). 
     Carrying part  302  includes filament retainer  314 . Filament retainer  314  mechanically retains the filament to enable electrode  142  to deploy the filament when electrode  142  is deployed. Retention may include any fastening technology (e.g., screw threads, bayonet type, snap, latch), binding technology (e.g., friction fitting, staking), and/or joining technology (e.g., sonic welding, adhesives), for example, as discussed above, that is suitable for reliably securing a filament to the carrying part. Binding by friction facilitates relatively low manufacturing cost, mechanical reliability, and ease of manual and/or automated assembly of electrode  142 . One end of a filament may be retained (e.g., fixed in place) to carrying part  302  by filament retainer  314  before assembling fastening part  302  with piercing part  304 . 
     X-fastener  312  and y-fastener  322 , according to various aspects of the present invention, may cooperate with the filament retainer  314  to accomplish retention. For example, compression required to assemble x- and y-fasteners to each other and/or resulting from fastening may exert a force that increases friction for suitable binding. 
     A carrying part may partially enclose a piercing part. In another implementation, a piercing part may partially enclose a carrying part. According to various aspects of the present invention, particular synergies are realized in an electrode  142  that is assembled by combining carrying part  302  and piercing part  304  on an axis. For example, when x-fastener  312  has a first axis and y-fastener  322  has a second axis, these fasteners may be aligned to an alignment axis and then moved together along the alignment axis to accomplish assembly of the two parts. 
     Carrying part  302  may further include one or more structural features that position a shaft of a spear. Shaft positioner  316  securely maintains a position of spear  306  with respect to a front face of electrode  142 . Shaft positioner  316  may retain shaft  332  at a particular length extending away from the front face. Shaft positioner  316  may be capable of retaining shaft  332  at one of a set of fixed lengths selected during assembly of electrode  142 . By permitting selection during assembly, different electrode designs may be manufactured from parts that are common to all designs (e.g., same carrying part, same spear). 
     A front face of an electrode resists further penetration of electrode  142  into a target. A front face having dimensions larger than the diameter of shaft  332  stops penetration of shaft  332  by abutting target clothing or tissue  202 . Consequently, a shaft positioner when implemented with a front face may determine a maximum depth of penetration of an electrode into a target. 
     Carrying part  302  may be implemented as an integral monolithic structure formed of one material. Forming may include molding, casting, extruding, and/or milling. When carrying part  302  is desired to be non-insulative (conductive, resistive, or subject to ionization along or through after an activation voltage is exceeded), conductive filler may be included in the material used to form carrying part  302 . 
     A piercing part pierces clothing or target tissue to form and to mechanically maintain the electrical circuit discussed with reference to  FIG. 2 . A piercing part may retain a filament as discussed above and may electrically couple a filament to the target by positioning the filament proximate to the target. A piercing part may be implemented as an integral monolithic structure formed of one material. A piercing part may include a spear as a separate part that is combined to form the complete piercing part. 
     For example, piercing part  304  performs the functions of an electrode discussed above in cooperation with carrying part  302 . Y-fastener  322  establishes and secures the assembly of the carrying part  302  and piercing part  304  through the mechanical stresses of launching, filament deployment, and electrode impact with a target. Filament positioner  324  maintains the filament in relation to piercing part  304  and thereby maintains the filament in relation to target tissue. A spear performs the piercing function of a piercing part of an electrode. A spear may also perform a retaining function to mechanically retain the electrode in contact with the target (e.g., by maintaining a relative position of the piercing part with respect to the target). 
     For example, spear  306  includes shaft  332 , target retainer  334 , and tip  336 . A shaft supports a target retainer and a tip. A shaft and tip cooperate to accomplish piercing to a desired depth. The shaft is generally suitable for penetration of clothing and/or target tissue. The length of the shaft may locate the tip a desired distance from a front face of the electrode, as discussed above, so that only the shaft and tip penetrate target clothing and/or tissue when the face abuts the target. The shaft may flex a suitable amount on impact to avoid breakage. 
     A target retainer resists removal of the shaft from the target. A target retainer may be implemented with one or more barbs arranged behind the tip. 
     A tip includes any structure that pierces target clothing and/or tissue. A tip may include one or more points front-facing toward the target. A tip may be formed with a target retainer immediately behind the tip (e.g., barb, rear-facing point). 
     The total mass of electrode  142  of  FIG. 3B  may be distributed between aft part  342  and fore part  344  to accomplish desired deployment behavior and target retaining behavior. Conventional ballistics analysis techniques may be used. 
     Another functional block diagram of an electrode, according to various aspects of the present invention, illustrates somewhat different functional and structural cooperation. Electrode  142  of  FIG. 3B  includes aft part  342  and fore part  344 . Aft part  342  includes x-fastener  350  and x-filament retainer  352 . Fore part  344  includes y-fastener  354 , y-filament retainer  356 , and spear  358 . In implementations according to this functional block diagram, electrode  142  performs the functions discussed above. Electrode  142  is assembled by mating x-fastener  350  with y-fastener  354  where x-fastener  350  and y-fastener  354  may include the structures and functions discussed above with reference to x-fastener  312  and y-fastener  322 . 
     The function of retaining a filament, as discussed above, is performed by x- and y-filament retainers  352  and  354  when assembly of electrode  142  is completed. In one implementation, x- and y-filament retainers bind a filament when abutted against each other. Any conventional two-part retention technology may be used (e.g., fastening, binding, joining) between an end of a filament, x-filament retainer, and y-filament retainer. 
     X-fastener  350  and y-fastener  354  may cooperate with x-filament retainer  352  and y-filament retainer  354  to distribute strain occurring between electrode  142  and a filament. Distributing strain may facilitate using smaller, lighter, and/or weaker technologies for these functions individually. 
     Spear  358  may include the structures and perform the functions discussed above with reference to spear  306 . In the absence of the need to cooperate with a shaft positioner, spear  358  may be structurally simpler than spear  306 . Spear  358  may be integral to fore part  344  (e.g., formed of the same material and/or formed at the same time). Spear  358  may be fixed to fore part  344  prior to assembly of aft and fore parts  342  and  344 . 
     According to various aspects of the present invention, electrode  142  of  FIG. 3B  may be assembled by combining aft part  342  and fore part  344  on an axis. For example, when x-fastener  350  has a first axis and y-fastener  354  has a second axis, these fasteners may be aligned to an alignment axis and then moved together along the alignment axis to accomplish assembly of the two parts. 
     Another functional block diagram of an electrode, according to various aspects of the present invention, illustrates somewhat different functional and structural cooperation. Electrode  142  of  FIG. 3C  includes aft part  362  and fore part  364 . Aft part  362  includes x-filament retainer  370  that also serves to retain aft part  362  and fore part  364  in an assembled configuration. Fore part  364  includes y-filament retainer  372 , mass  374 , target retainer  376 , and tip  378 . 
     In implementations according to the functional block diagram of  FIG. 3C , electrode  142  performs the functions discussed above. Electrode  142  is assembled by mating x-filament retainer  370  with y-filament retainer  372 . X-filament retainer  370  and y-filament retainer  372  may include the structures and functions discussed above with reference to x-fastener  350 , y-fastener  354 , x-filament retainer  352 , and y-filament retainer  356 , suitably designed to accomplish fastening and filament retaining without distribution of strain as discussed above with reference to  FIG. 3B . 
     Fore part  364  may include substantially all of the mass of electrode  142  (e.g., greater than 80%, about 90%) Such a mass distribution may inhibit tumbling of electrode  142  during launching, deployment, and/or impacting a target. For example, mass  374  may comprise a material of greater density than materials of other portions of fore part  364 . In one class of implementations, mass  374  comprises a plastic carrier impregnated with particles and/or fibers of denser material (e.g., metal, carbon, graphite, brass, stainless steel). Mass  374  may be formed on or about a shaft portion of fore part  364 . A front face, as discussed above, for fore part  364  may be provided by mass  374 . 
     Fore part  364  performs the functions discussed above with reference to a spear by integrating the target retainer and tip in the structure of fore part  364 . Fore part  364  may include an integral shaft to position tip  378  a suitable distance in front of a face of fore part  364 . Fore part  364  may omit the shaft structure of the spear as discussed above. 
     According to various aspects of the present invention, an electrode  142  of  FIG. 3C  may be assembled by combining aft part  362  and fore part  364  on an axis. For example, when x-filament retainer  370  has a first axis and y-filament retainer  372  has a second axis, these retainers may be aligned to an alignment axis and then moved together along the alignment axis to accomplish assembly of the two parts. 
     Electrode  142  of  FIGS. 3A, 3B, and 3C  may be implemented to provide spreading. For example, an end of filament  140  may be positioned at or near a front face of electrode  142 . Either or both parts of each electrode design may support propagation of electricity from the filament to the target. For example, either or both parts may comprise non-insulative materials (e.g., conductive, resistive, insulative, composite). 
     Electrode  142  of  FIGS. 3A, 3B, and 3C  may be implemented to provide diffusing. For example, material forming a front face, spear, target retainer, and/or tip may comprise non-insulative materials. 
     An electronic weapon  100 , according to various aspects of the present invention, may launch two electrodes each of any type discussed herein with reference to electrode  142 , where one electrode serves in the return path, as discussed above. For example, electronic weapon  100  of  FIG. 4  is shown immediately after a user initiated launch of two electrodes from a deployment unit. Electronic weapon  100  includes a hand-held launch device  110  that receives and operates one field-replaceable cartridge  130  as a type of deployment unit. Launch device  110  houses a power supply (having a replaceable battery), a processing circuit, and a signal generator as discussed above. Launch device  110  may be of the type known as a model M26 electronic control device marketed by TASER International, Inc. Cartridge  130  includes a plurality  402  of tethered electrodes including electrodes  142  and  143 . Upon operation of trigger  401 , electrodes  142  and  143  are propelled from cartridge  130  generally in direction of flight “A” toward a target (not shown). As electrodes  142  and  143  fly toward the target, electrodes  142  and  143  deploy behind them filaments  140  and  441  respectively. When electrodes  142  and  143  are positioned in or near the target, filaments  140  and  441  extend from cartridge  130  to electrodes  142  and  143  respectively. The signal generator provides a stimulus signal through the circuit formed by filament  140 , electrode  142 , target tissue, electrode  143 , and filament  441 . Electrodes  142  and  143  mechanically and electrically couple to tissue of the target as discussed above. 
     A deployment unit may substantially simultaneously deploy a plurality of electrodes. For example, deployment unit  130  of  FIG. 5  includes the exterior dimensions, features, and operational functions, of a conventional cartridge of the type used with model M26 and X26 electronic control devices marketed by TASER International, Inc.  FIG. 5  is drawn to scale with the angle formed by the launch tubes being 8 degrees. For deployment unit  130 , two electrodes are simultaneously propelled from respective cylindrical launch tubes (e.g., bore, chamber) in a housing of the deployment unit. For example, deployment unit  130  includes housing  502 , cover  508 , filament storage (not shown), bores  504  and  506 , propellant system  144 ,  145  comprising several components, and tethered electrodes  142  and  143 . Each tethered electrode  142  ( 143 ) is mechanically coupled to a respective filament (one shown)  141 , to deploy the filament with the electrode. Spaces for filament storage are located on both sides of the plane of the bores of the housing, so that in the cross-section view of  FIG. 5 , one storage space is removed by cross section and the other is hidden. In use, the propellant explosively provides a volume of gas that pushes each electrode  142  ( 143 ) from the respective bore  504  ( 506 ). Acceleration, muzzle velocity, flight dynamics, and accuracy of hitting the target are affected by the fit of the electrode as it leaves the bore. Any diameter along the length of the electrode that exceeds a limit interferes for a period of time unnecessarily with propelling the electrode from the bore. 
     Portions and/or parts of an electrode, as discussed above, may be formed, according to various aspects of the present invention, of materials that are not highly conductive. These materials are discussed above as resistive, insulative, and composite. The structure of these materials may be uniform through a volume or nonuniform. When uniform, electrical activation may be in accordance with a resistance per unit length and one or more lengths of conduction (path lengths) needed to accomplish suitable activation. Nonuniformity may be accomplished by varying the blend of constituents of the material when molding the desired structure, or by arranging materials of different properties in series assembly. Nonuniformity may cause resistance to increase away from the target or to any desired nonlinear extent. Conductive and/or resistive materials may be combined with insulative materials in any conventional fashion. 
     Insulative materials include nonconductors. When exposed to ionization voltages, portions of insulative materials along paths of ionization may reform (e.g., wear, deform, mobilize, melt, vaporize, temper, congeal, crystallize, stratify, reconstitute) into resistive materials, voids, and/or pockets of component materials (e.g., liquids or gases). Reformed insulative materials are examples of resistive or non-insulative materials. Reformation may change a magnitude of voltage needed for a desired activation. Insulative materials may comprise plastic, nylon, fiberglass, or ceramic. Insulative coatings include lacquer, black zinc, a dielectric film, a non-conductive passivation layer, a polyp-xylylene polymer (e.g., Parylene), polytetrafluoroethylene (e.g., Teflon), a thermoplastic polyamide (e.g., Zytel). Conventional insulative technologies may be used. 
     Insulative materials of a type herein called composite materials may include separated conductors. Conventional composite materials are manufactured and used for molding and overmolding. For example, a composite material may be formed from a liquid resin, plastic, or thermoplastic as a host material with solid fibers, spheres, ellipsoids, powder, or other particles as filler mixed into the host before the host cures to a solid. Host material may be plastic, nylon, PEEK (polyetheretherkeytone), thermoplastic elastomer (e.g., thermoplastic polyurethane (TPU)), SBS poly(styrene-butadiene-styrene) rubber. Particles of conductive (e.g., metal, stainless steel, tungsten) or resistive (e.g., carbon) material may be used as filler. Particles having a coating of conductive or resistive material may be used as filler. For example, insulative material of the type marketed by RTP Co. as thermoplastic polyurethane elastomer (TPUR/TPU) comprising nickel-coated carbon fiber may be used. Spheres or powder may have a diameter of from about 3 to about 11 microns. Fibers may have a similar diameter and a length of from about 5 to about 7 millimeters. Filler to host by weight may be from about 5% to about 40% to assure separation (nonoverlap) of particles. Composition may result in activation voltages of from about 50 volts to about 6000 volts for components of electrodes  142 . In operation at voltages expected to be sufficient for ionization between nonoverlapping particles, composite materials are also examples of non-insulative material. 
     A tethered electrode  600 , of  FIGS. 6 and 7 , in accordance with the functions discussed above with reference to  FIGS. 1, 2, 3A, 4, and 5 , retains a filament  601  in an assembly of a carrying part  602  and piercing part  604 . Electrode  600  is substantially cylindrical as shown in the rear view of surface  620  in  FIG. 7 . Carrying part  602  includes an x-fastener (surface  622 ) and a filament positioner (notch  612 ). Retention of filament  601  is accomplished by the cooperation of carrying part  602  and piercing part  604 . Piercing part includes a y-fastener (surface  624 ), a filament retainer (bore  702 ), a shaft positioner (two notches  630 ), and a spear  640  having an elbow  634 , a shaft  608 , a target retainer (barb  613 ), and a tip  614 . A filament positioner is omitted from piercing part  604 . 
     Carrying part  602  includes a cylindrical outer surface  642  and a conical inner surface  644  so as to accept piercing part  604 . Piercing part  604  has a substantially conical outer surface  652  and a substantially central bore  702 . 
     When unassembled, slot  704  opens to accept spear  610  and filament  601 . Spear  610  may be positioned for one of two lengths measured from front face  611  of electrode  600  to tip  614 . For a first length, as shown, elbow  634  of shaft  608  is located over notch  632  so that a portion of shaft  608  extends into notch  632 . For a second longer length, elbow  634  is located over notch  633  and is retained in piercing part  604  in a way analogous to the configuration of the first length. Filament  601  is then placed in bore  702  in abutting contact along a rear portion of shaft  608 . Filament  601  is extended past front face  611  and toward notch  612 . A portion of filament  601  may be uninsulated to facilitate electrical coupling of filament  601  and target tissue with little or no need for ionization. The uninsulated portion may include elbow  606  and further may include additional portions of filament  601  proximate to elbow  606 . 
     To assemble electrode  600 , carrying part  602  is threaded onto filament  601  and set aside. An axial opening for access to bore  702  in piercing part  604  is opened and shaft  608  is located in a suitable notch  630 . Filament  601  is laid on top of shaft  608 . Piercing part  604  is then compressed circumferentially with respect to an axis of circular symmetry to close the axial opening. Carrying part  602  is aligned on the same axis as piercing part  604  and the two parts are pressed together until surface  622  of piercing part  602  snaps over and latches against surface  624  of carrying part  604 . When assembled, a resistance to expand radially of carrying part  602  causes surfaces  644  and  652  to grip in friction fit against each other, to retain filament  601  in bore  702 , and to retain elbow  634  over the selected notch of notches  630 . The assembly is held together by the mechanical interference of surfaces  622  and  624  that form a fastener (e.g., latch, catch, snap). 
     Notch  612  may be dimensioned to retain filament  601  by friction fit. 
     Bore  702  may be dimensioned to retain filament  601  by friction fit in the absence of carrying part  602  and/or when assembled with carrying part  602  (e.g., bore  702  diameter reduced by radial pressure). 
     Another tethered electrode  800 , of  FIGS. 8 and 9 , in accordance with the functions discussed above with reference to  FIGS. 1, 2, 3B, 4, and 5 , retains a filament  808  in a coaxial assembly of aft part  802  and fore part  804 . Electrode  800  is substantially cylindrical as shown in the perspective views of  FIGS. 8 and 9 . Aft part  802  includes an x-fastener (tabs  832  and  834 ) and an x-filament retainer (notch  812 ). Fore part  804  includes a y-fastener (tab  842  and a symmetrically arranged identical tab not shown but diametrically opposite tab  842 ), a y-filament retainer (rear surface of fore part  804 ), and a spear  844  comprising a shaft  846 , a target retainer  848 , and a tip  850 . Fore part  804  may be formed of plastic or metal (e.g., brass, aluminum). Spear  844  may be formed of the same material (e.g., cast, machined) or a dissimilar material (e.g., stainless steel inserted into plastic rear portion). 
     In one implementation, shaft  846 , target retainer  848 , and tip  850  are formed of relatively more resistive or insulative (e.g. composite material) than the other portions of fore part  804  (e.g., activation at relatively higher voltage). 
     When unassembled, bore  908  or  FIG. 9  accepts filament  808 . Filament  808  is bent and pressed into channel  814  in face  906  of aft part  802 . Channel  814  retains filament  808  by friction fit. Friction is increased when fore part  804  abuts filament  808  when locked in assembled position against aft part  802 . 
     To assemble electrode  800 , filament  808  is threaded into aft part  802  and laid into channel  814 . The, aft part  802  is aligned on a common cylindrical axis with fore part  804 , and the two parts are pushed together until the fasteners (tabs  832 ,  834 ,  842 ) fasten to each other. Four tabs interdigitate:  902  and  904  with tabs  842  and its symmetrical opposite tab (not shown). The assembly is held together by the mechanical interference of the four tabs that form a fastener (e.g., latch, catch, snap). The force to operate the fastener conforms filament  808  to channel  814  and increases friction between filament  808  and abutting surfaces of the channel and fore part  804  to accomplish the filament retaining function. 
     Another tethered electrode  1000 , of  FIGS. 10-14 , in accordance with the functions discussed above with reference to  FIGS. 1, 2, 3C, 4, and 5 , retains a filament  140  in an assembly of aft part  1002  and fore part  1004 . Electrode  1000  is substantially cylindrical as shown in the perspective views of  FIG. 10 . Aft part  1002  includes an x-filament retainer comprising a channel  1120  formed with two latch arms  1206  and  1406 . Fore part  1004  includes a y-filament retainer comprising base  1310  having an irregular surface  1312  formed with anvil  1304  that cooperates with latch arms  1206  and  1406 . Fore part  1004  additionally includes a mass  1102  with a surface  1010  for propagating stimulus current to the target, a front face  1012 , a target retainer  1006  comprising a shaft  1007 , barb  1108 , and tip  1008 . Aft part  1002  may be formed of resilient material (any relatively soft plastic). Fore part  1004  may be formed of rigid material (e.g., any relatively hard plastic, composite material). 
     In the cross section view of  FIG. 11  taken along an axis of circular symmetry of electrode  1000 , surfaces of filament retainer  1002  and fore part  1004  are shown cooperating to retain filament  140  by friction in a channel  1120  that proceeds symmetrically in two directions from opening  1220 . Filament  140  is forced to conform to surfaces defining channel  1120  as aft part  1002  is fastened to fore part  1004 . Mass  1102  is overmolded onto shaft  1104  of fore part  1004 . Mass  1102  is formed of resistive and/or composite material with an exposed surface  1010  suitable for propagating current from an exposed end  1003  of filament  140  toward front face  1012 . 
     In the perspective rear view of assembled electrode  1000  of  FIG. 12 , filament  140  is shown threaded through opening  1220  with an exposed end  1003  trimmed flush to electrode  1000  after assembly of aft part  1002  and fore part  1004 . Exposed end  1003  is positioned within a suitable distance for ionization to occur between exposed end  1003  and surface  1010  for propagation of current as discussed above. Aft part  1002  is formed of resilient material (e.g., plastic). Aft part  1002  includes latch arm  1206  and an identical second latch arm  1205  diametrically opposite latch arm  1206 . Latch arm  1206  includes an opening  1202  that admits anvil  1204  of fore part  1004 . When aft part  1002  and fore part  1004  are assembled, latch surface  1208  interferes with a forward surface (not shown) of anvil  1204  to retain aft part  1002  fixed to fore part  1004 . Identical features and cooperation occur with respect to the second latch arm  1205  and a second surface (not shown) of anvil  1204 . 
     Filament  140  is retained in a channel  1120  as discussed above and as illustrated in  FIGS. 13 and 14 . Channel  1120  is defined across a diameter of the electrode that includes opening  1220  through which filament  140  enters channel  1120 . Channel  1120  is defined by irregular surface  1432  of aft part  1002  in cooperation with irregular surface  1312  that traverses base  1310 , and a respective inner surface of each of barriers  1422 ,  1424 ,  1426 , and  1428  all of fore part  1004 . Base  1310  comprises the integral combination of a surface for retaining filament  140  and surfaces for latching aft part  1002  with fore part  1004 . Anvil  1204  includes ends  1304  and  1305 . Each latch arm  1206  ( 1406 ) is held by a surface (not shown) of anvil  1204  at an end  1304  ( 1305 ) of anvil  1204  to maintain the assembly of aft part  1002  and fore part  1004 . 
     A barrier, according to various aspects of the present invention, defines a channel, assures proper assembly, and includes an irregular surface for retaining a filament. Aft part  1002  comprises four barriers  1422 ,  1424 ,  1426 , and  1428  that are symmetrical and arranged about opening  1220 . Each barrier provides surfaces with structure and functions analogous to surfaces  1434  and  1436  of barrier  1422 . Barriers  1422  and  1424  define half channel  1420  of channel  1120 . Filament  140  is shown in channel  1420  of  FIG. 14 . Filament  140  is retained in an analogous manner when located in half channel  1421  of channel  1120 . Surface  1436  guides either end  1304  or  1305  of anvil  1204  into proper orientation for operation of latch arms  1206  and  1406 . Surface  1434  prohibits filament  140  from leaving half channel  1420 . Consequently, when latch arms  1206  and  1406  catch on anvil  1204  as discussed above, filament  140  must conform to irregular surfaces  1432  and  1312 . Latch arms  1206  and  1406  and anvil  1204  are dimensioned so that surfaces  1432  and  1312  are separated by a distance suitable for retaining filament  140  under all conditions of electrode  1000  use including assembly, deployment, and impact with a target. 
     The foregoing description discusses preferred embodiments of the present invention, which may be changed or modified without departing from the scope of the present invention as defined in the claims. Examples listed in parentheses may be used in the alternative or in any practical combination. As used in the specification and claims, the words ‘comprising’, ‘including’, and ‘having’ introduce an open ended statement of component structures and/or functions. In the specification and claims, the words ‘a’ and ‘an’ are used as indefinite articles meaning ‘one or more’. When a descriptive phrase includes a series of nouns and/or adjectives, each successive word is intended to modify the entire combination of words preceding it. For example, a black dog house is intended to mean a house for a black dog. While for the sake of clarity of description, several specific embodiments of the invention have been described, the scope of the invention is intended to be measured by the claims as set forth below. In the claims, the term “provided” is used to definitively identify an object that not a claimed element of the invention but an object that performs the function of a workpiece that cooperates with the claimed invention. For example, in the claim “an apparatus for aiming a provided barrel, the apparatus comprising: a housing, the barrel positioned in the housing”, the barrel is not a claimed element of the apparatus, but an object that cooperates with the “housing” of the “apparatus” by being positioned in the “housing”. The invention includes any practical combination of the structures and methods disclosed. While for the sake of clarity of description several specifics embodiments of the invention have been described, the scope of the invention is intended to be measured by the claims as set forth below.