Abstract:
A paint ball gun includes an agitator mounted on the end of a rotary motor shaft. Rotational direction of the motor shaft is controlled by an electronic circuit responsive to a tilt sensor. The inclusion of tilt sensor provides an enhanced paint ball gun capable of operating optimally during periods of gun tilt. Several preferred magazine designs incorporating the tilt sensor are illustrated. An additional double-rotation of the motor is disclosed which enables short bursts of oppositely directed agitator rotation, which frees any jams that may occur. These short bursts may be triggered manually, electronically responsive to a sensed condition indicative of a jam, or through a timed interval. The paint ball gun is capable of rapidly firing more paint balls under otherwise sub-optimal conditions than previously known in the art.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains generally, though not exclusively, to paint ball guns used for recreational and training purposes. For the purposes of this disclosure, paint ball guns are specifically defined as apparatus that propel paint capsules from a barrel in rapid succession and at relatively high speeds. The paint ball capsules are designed to break upon impact with an object or person, thereby rendering an identifiable mark without injuring the person or object. The present invention more specifically pertains to an electronically controlled magazine that stores and feeds paint balls into a firing chamber. 
     2. Description of the Related Art 
     Paint ball guns can fire in rapid succession a relatively large number of paint balls in a short period of time. A magazine stores the paint balls until the balls are delivered to the gun firing chamber. The guns use compressed gas as the propellant, and are usually triggered by a user squeezing a conventionally shaped gun trigger. When the gun user repeatedly squeezes the trigger, the gun should continue to fire paint balls as rapidly as possible. Guns may be manually loaded before each shot, but most are either semi-automatic, where each time the trigger is pulled a paint ball is fired, or fully automatic, where the balls are fired as quickly as the gun is capable of for as long as the trigger is pulled. 
     Quite unlike conventional explosive-propelled munitions, current paint balls are relatively round and have an exterior formed from a semi-rigid gelatinous compound. The gelatinous compound is known to be affected by such variables as temperature and relative humidity, and is of course somewhat frangible. During a firing sequence, paint balls on occasion lodge against each other or other objects and block the passageway to the firing chamber, resulting in a jam. While jamming is not new, knowledge from explosive munitions magazines is of little use with the very different paint balls. 
     Basic paint ball magazines are little more than large hoppers with a feed tube extending therefrom, a sort of closed funnel through which paint balls are dropped into the firing chamber. Unfortunately, the passageway must ultimately taper to isolate single paint balls therein. Usually this is not a gradual taper, but a sudden transition, to reduce the likelihood of two balls getting stuck against each other. Unfortunately, when one paint ball does lodge against the other, the user must shake the gun to free the balls. 
     One method of preventing paint ball jams is proposed by Miller in U.S. Pat. No. 5,097,816. Therein, a large helical magazine is provided through which the paint balls pass in a single row, eventually leading to the firing chamber. Unfortunately, the Miller design does not use space efficiently, requiring a large helical path with the center portion thereof unused. The extra dimension is undesirable. Furthermore, because of the reduced slope of the surfaces heading into the firing chamber, actual feed rates may be reduced and paint balls may not be provided at speeds sufficient to meet the needs of the more rapidly firing guns. Cleaning of the Miller construction, which is necessary over time to ensure smooth feeding of the paint balls, is difficult also due to the inaccessibility of the central loops of the helix. 
     Farrell in U.S. Pat. No. 5,511,333 also illustrates a magazine designed not to jam. Unfortunately, the straight tube design severely limits the number of balls contained within a single magazine. When a rapid fire sequence is initiated, the gun may not jam, but it is highly probably that the magazine will empty, still rendering the gun temporarily disabled. 
     U.S. Pat. No. 5,282,454 to Bell et al, incorporated herein by reference, discloses a large magazine with sloping ends and side walls that lead downward to a tubular passageway referred to as a feed tube. Gravitational forces tend to urge the paint balls to the feed tube, as known in the prior art. The magazine is large, capable of holding many paint balls at a time. The feed tube is connected to the firing chamber of the gun, so that as the paint balls are carried through the tube, they are fed into the firing chamber. Occasionally, a pair of paint balls will simultaneously drop into the opening of the feed tube so that neither can pass, leading to a jam. 
     To prevent jamming of this type, the Bell et al patent proposes an agitator paddle to stir the paint balls. The agitator paddle may slightly overlap the feed tube opening. In addition to directly clearing any jams at the feed tube opening, the agitator paddle also keeps other paint balls within the magazine moving and available for feeding through the tube. Even if the gun is tilted slightly, the agitator paddle will tend to stir the balls and encourage them to move around, with the increased likelihood that they will continue to pass into the feed tube. 
     Since the agitator paddle is driven by a small DC motor, batteries are required. Unfortunately, the battery drain is significant. To preserve the battery during periods of non-use, as well as ensure that a user may stay quiet absent the sounds of the motor and agitator, Bell et al disclose an optical sensor within the feed tube which detects an absence of paint balls at a point within the tube. When no ball is present, an electronic circuit triggers the motor to spin the agitator. As soon as a paint ball blocks the optical path, the motor is again stopped. 
     While the Bell et al design enhances the rate at which paint balls may pass into the feed tube and has enhanced the sport, improved guns and occasional mishaps have revealed limitations therein. 
     For example, the simple paddle shown in the Bell et al patent, while helpful, still does not ensure sufficient feed rates for newer model guns. To overcome this feed rate limitation, newer designs include higher power motors propelled by twice as many batteries. The standard model agitator is propelled by a single nine volt battery, while the enhanced version is propelled by two nine volt batteries. In addition, the paddle has been redesigned to have four flat surfaces extending longitudinally parallel with the motor shaft and radially therefrom, equidistantly spaced at 90 degree intervals. While this model improves the feed rate significantly, the added weight and cost of the additional battery is certainly undesirable. Furthermore, the added size of the battery compartment makes the gun an easier target for an opponent to hit. 
     Williams, in U.S. Pat. No. 5,505,188 discloses a coiled tube within the magazine chamber that is pressurized during the firing process to force balls into the feed tube. During rapid fire sequences, the magazine is certainly agitated by motion of the coiled tube. However, the coiled tube does not positively clear the feed tube opening and so can, in some instances, actually create a jam at the feed tube inlet. 
     Stevens, in U.S. Pat. No. 6,109,252, the contents which are incorporated herein by reference, discloses an improved paint ball carrier which receives paint balls in pockets around the periphery thereof. A guide assembly improves the orderly feeding of balls into an opening. 
     Anderson, one of the present inventors, in U.S. Pat. Nos. 5,791,325 and 5,947,100 incorporated herein by reference, discloses a paint ball gun including an improved agitator which delivers higher paint ball feed rates than other prior art agitators. Illustrated in those patents are various novel features, combinations, and sub-combinations, the listing herein in summary form not to be interpreted as defining, restricting or limiting the actual contents of those patents, but instead the contents and teachings of these patents are incorporated herein by reference. Such features and combinations are illustrated therein as an electronic circuit having a duration control which delays turning off the motor for a predetermined interval. The motor remains activated continuously during a rapid firing sequence. In addition, a magnetic, sound, pressure, shock or similar sensor is disclosed to trigger the electronic circuit into energizing the motor. The combination of sensor trigger, duration control and agitator design provide a greatly enhanced paint ball gun capable of operating without jamming or undesired noise during non-firing periods. Nevertheless, even further improved magazine paint ball feed rate and more enhanced performance under a variety of conditions are still desired. 
     SUMMARY OF THE INVENTION 
     In a first manifestation of the invention, a controller for a paint ball gun magazine agitator motor includes a tilt sensor which in response to the magazine being tilted generates an electrical direction indicator signal; a tilt duration detector timing the electrical direction indicator signal; and an electrical circuit for controlling a direction of rotation of the paint ball magazine agitator motor responsive thereto. 
     In a second manifestation of the invention, a tilt activated relay for powering a paint ball magazine agitator comprises means for detecting tilt of the paint ball magazine with respect to gravity, means for timing a duration of detected tilt, means for determining when the time exceeds a threshold; and means for selectively reversing a rotation of the paint ball magazine agitator motor responsive to the determining means. 
     In a third manifestation of the invention, a method of refilling a paint ball gun magazine feeder tube comprises the steps of detecting magazine tilt; initiating an electrical pulse responsive to the tilt; and activating a paint ball agitator responsive to the tilt and a demand for paint balls, to thereby move paint balls into the feeder tube. 
     OBJECTS OF THE INVENTION 
     While the prior art Anderson developments advanced the state of the art, the inventors have discovered that the magazines of the art are sensitive to gun tilt away from vertical, and that this sensitivity can be used advantageously to control paint ball feeding. Exemplary embodiments of the present invention solve inadequacies of the prior art by providing a tilt sensor and control system to change the rotational direction of the agitator responsive to sensed tilt. Additional combinations of magazine and agitator design further benefit the paint ball delivery system. 
     A first object of the invention is to improve magazine paint ball feed rate. A second object of the invention is to enhance magazine performance under the diverse conditions of a competition or field use. Another object of the present invention is to provide a retro-fit capability to existing guns, to allow upgrade of existing equipment. Yet a further object of the invention is to enable a jammed gun to be reversed, to thereby free the agitator for further use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, advantages, and novel features of the present invention can be understood and appreciated by reference to the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 illustrates a prior art paint ball gun in a ready position from side plan view. 
     FIG. 2 illustrates a partial cut-away view of a preferred embodiment paint ball magazine in accord with the teachings of the present invention. 
     FIG. 3 illustrates a top projected view of the paint ball magazine of FIG. 2, with the cover raised to reveal the agitator features of the preferred embodiment. 
     FIG. 4 illustrates a first alternative embodiment magazine by side cross-sectional view. 
     FIG. 5 illustrates the first alternative embodiment magazine from top cross-sectional view. 
     FIG. 6 illustrates by block diagram an electrical circuit for a sound triggered agitator, and 
     FIG. 7 illustrates by block diagram an alternative sound triggering circuit. 
     FIG. 8 shows the waveforms of various outputs from FIGS.  6  and  7 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A prior art paint ball gun  100  is shown by side view in a “ready” position in FIG.  1 . Gun  100  includes a barrel  105 , pressure valve and hand grip  110 , pressure tank coupler  115  and hose  120 . One hand of a user may support gun  100  at pressure valve cover  110 , while the other hand will grip handle grip  125 . One finger, usually the pointer, will wrap around trigger  130 , and may be used to squeeze trigger  130  to activate the firing process. When trigger  130  is squeezed, movable bolt stop  140 , slidable bolt  145  and slidable valve  150  may all be moved away from gun housing  135 . The exact sequence and operation of the pressure valve, bolt stop  140 , slidable bolt  145  and slidable valve  150  are unimportant to the present invention, well known in the field, and achievable through several known alternatives. 
     Magazine  200  attaches to paint ball inlet  155  through feed tube  215 . Surrounding feed tube  215  is an optical sensor pair  230  and  235 , which detect by light wave whether a paint ball is absent at this location within feed tube  215 . Connected to sensor pair  230 ,  235  is a battery, motor and electronics compartment  220  having a power switch  225  for energizing the optical sensors and electronics. 
     In operation, a user may dispense paint balls into magazine  200  through cover  205 , into magazine chamber  210 . A source for pressurized gas will be connected to pressure tank coupler  115 , and pressurized gas will be conducted through hose  120  into a pressure valve within the gun. Depending upon the particular sensor and circuitry used, the user may next activate the battery, motor and electronics compartment by switching on switch  225 . The gun is then in a “ready” state, whereby squeezing trigger  130  will start the firing process. The firing process, through the various techniques described in my prior patents incorporated herein by reference, will ultimately trigger a motor to turn. 
     FIG. 2 illustrates the magazine of the present invention by partial cut-away view. Within magazine chamber  210  are a number of paint balls  240 . Also within chamber  210  is paint ball agitator shaft  300 , which is caused to rotate by motor shaft  305 . Onto agitator shaft  300  are mounted a plurality of arms  325 . 
     Feed tube  215  forms a sharp transition with magazine chamber  210  at transition  245 . In the preferred embodiment, agitator arms  325  overlap with transition  245  slightly, such that if two balls  240  should drop into feed tube  215  simultaneously and get lodged against each other at transition  245 , agitator arms  325  will serve to clear one of the balls. Feed tube  215  has a gentle taper  250  therein, which, although not absolutely necessary, helps to maintain exact spacing between magazine  200  and paint ball inlet  155  and helps to support magazine  200 . 
     FIG. 3 shows a top view of agitator shaft  300 , wherein the arrangement of arms  325  are evident. From the perspective shown in FIG. 3, motor shaft  305  rotates in either a clockwise direction shown by arrow  355  or a counter-clockwise direction as illustrated by arrow  350 . The present invention is not limited to agitator shaft  300  and arms  325 , and may alternatively include a variety of other constructions or arrangements which will serve to accomplish the same function and which are too numerous to specifically mention. Nevertheless, the preferred agitators will be effective regardless of rotation direction, for reasons which will be better understood herein below. In the preferred embodiment, the entire agitator is either polymer or coated with a polymer protectant, which serves to protect the agitator from corrosion, softens impact with paint balls  240 , and may provide better surface characteristics therebetween. 
     Referring to FIGS. 4 and 5, there is shown a first alternative embodiment magazine constructed in accord with the teachings of the present invention comprising a generally cylindrical casing  4  having an inlet  6  and an outlet  250 , drive means comprising a motor and power source  220 , a rotor assembly  12  and a guide assembly  14 . The inlet  6  to the casing  4  has a removable lid  16 . Rotor assembly  12  is attached to a driving spindle  18  extending from motor  10  and comprises a carrier disc  20  and a guide disc  22 . The carrier and guide discs  20 ,  22  are held apart from one another by a spacer member  24 . Guide assembly  14  comprises a guide bar  26  and a squash plate  28 . A barrier plate  30  extends from an inner wall  32  of the casing  4 . In use, rotor assembly  12  is rotatable by motor  10  while guide assembly  14  is anchored at a fixed position within casing  4 . 
     Carrier disc  20  has a lower surface  34  and a generally circular lower portion  36 . Around the periphery of carrier disc  20 , between lower portion  36  and upper surface  38  are provided at least one, or, in the preferred embodiment, a plurality of pockets  40  that are preferably equidistantly spaced. Each pocket faces radially outwards of the carrier disc  20  and is shaped to receive a paint ball  42 . In the embodiment shown, carrier disc  20  has eight pockets  40 . A rear portion  44  of each pocket  40  has approximately the same radius of curvature as the outer surface of a paint ball  42  to receive a paint ball  42  therein. Guide disc  22  has an upper surface  46  and a lower surface  48  and, when viewed in plan, has the same shape as the upper surface  38  of the carrier disc  20 . Eight guide recesses  50  are provided. Guide disc  22  is positioned relative to carrier disc  20  by spacer member  24  such that guide recesses  50  are aligned with pockets  40 . 
     Radially extreme edges  51  of each pocket  40  curve upwardly and rearwardly from the lower portion such that a space  53  is defined between pocket edges  51  and casing  4 . It will be understood that the radial dimension of space  53  is less than the diameter of the paint balls  42  to prevent paint balls  42  from moving between pockets  40  in use, or becoming jammed between pocket edges  51  and casing  4 . 
     In use, a plurality of paint balls  42  are introduced into casing  4  via inlet  6 . Under the influence of gravity, the lowermost paint balls  42  are received into pockets  40 . The remaining paint balls  42  are either stacked above pockets  40  in spaces defined between guide disc recesses  50  and casing  4 , or remain above guide disc  22  in readiness to descend through a recess  50  to a pocket  40 . 
     Rotor assembly  12  is initially rotated by motor  10  to fill tube  215  with paint balls  42 . Taking the example of a single paint ball  42  retained in a pocket  40 , as carrier disc  20  rotates the paint ball  42  is moved into contact with guide bar  26 . Continued rotation of carrier disc  20  results in paint ball  42  moving out of pocket  40  and into feed tube  215 . The number of rotations required to fill tube  215  will depend on such factors as the length of tube  215  and the number of pockets on carrier disc  20 . Once feed tube  215  is filled, gun  100  is primed and ready to fire. Subsequent rotation of the rotor assembly  12  is carried out in combination with a control system linked to a trigger mechanism of gun  100  as illustrated in the aforementioned Anderson patents. 
     In the prior art, sensors  230 ,  235  were used to directly trigger a relay and activate the motor. This resulted in rapid starting and stopping of the motor during periods of rapid firing. As a result of the starting and stopping, and since motors draw more current and are less efficient during starting, the circuit tended to drain the battery more than is desired for the resultant feed rate. 
     In an alternative embodiment, magazine  100  is triggered by sound. Each time paint ball gun  100  fires, a distinct set of frequencies of relatively large magnitude are generated by gun  100 . A relatively low cost microphone  234  may be provided instead of either optical pair  230 ,  235  or magnetic pair  232 ,  237 , as shown by block diagram in FIG.  6 . While  234  is identified herein as a microphone, it will be recognized by those familiar with the sound detection art that device  234  may encompass any type of device which is capable of converting sound waves into detectable electrical changes. Moreover, other wave detector types of devices such as pressure sensors or shock sensors could also be used. The purpose of the particular device, regardless of construction or embodiment, is to act as a firing sensor which senses or detects the firing of the gun. 
     While the firing sensor may take on many different constructs, a microphone is illustrated herein. Microphone  234  may be located directly on magazine  200 , for example adjacent to or within battery, motor and electronics compartment  220 , thereby eliminating any need for wires external of compartment  220 . The output  236  from microphone  234  will generally be too weak or of inappropriate character to directly use in other processing circuitry, so amplifier  510  may be provided. Amplifier  510  may perform a variety of additional functions incident to amplification, such as that of envelope detectors, comparators, limiting, buffering, and/or triggering of the nature of a Schmidt trigger. For example, if amplifier  510  is a high gain amplifier such as an op-amp type designated as a  741  style, or conceivably several of these in series, once a minimum peak threshold V t  is reached as shown in FIG. 8, amplifier  510  may drive output  512  to full supply voltage. When the envelope of microphone output  236  falls below threshold V t , amplified output  512  may be at a ground potential or negative supply, depending upon the type of amplifier circuitry selected. So while amplification is the primary function performed by amplifier  510 , a variety of additional functions may be performed which are incident thereto and beneficial, as is known in the amplification art. 
     An amplified microphone signal  512  is conveyed from amplifier  510  to timer  520 . Timer  520  then converts brief electrical impulses indicative of firing into longer duration pulse, for example of one-half second duration. This longer duration signal represents a demand for paint balls, since one ball has been used during firing, and relay  460  is then activated to provide full battery power to motor  470 . 
     Activation of relay  460  is most preferably controlled responsive to tilt sensor  600 , which may be a mercury tilt switch, an accelerometer, various gravity or force sensors, gyroscopic sensors, or other technique to determine orientation relative to gravity. In one conceived embodiment, tilt sensor  600  and device  234  can comprise a single dual-axis accelerometer. One axis serves as the firing detector, while the second axis detects tilt. As aforementioned, the angle of orientation of the magazine has a consequential effect on the rate and potential success of feeding paint balls. Most preferably, motor shaft  305  is rotated to feed paint balls toward feed tube  215 , rather than away therefrom. In other words, and with reference to FIG. 3, should magazine  200  be tilted to load the right side thereof with paint balls, motor shaft  305  will most preferably be rotated counter-clockwise, in the direction of arrow  350 . As the paint balls are swept from the right side of magazine chamber  210 , they will then be deposited directly into feed tube  215 . This results in a more efficient deposit of balls therein. In the event magazine  200  is then tilted in a direction opposite, to cause the balls to accumulate on the left side of magazine chamber  210 , motor shaft  305  will most preferably be rotated in a clockwise direction as illustrate by arrow  355 . Once again, this will sweep the paint balls  240  into feed tube  215  with a minimum of traversing and a maximum efficiency. The example with reference to magazine chamber  210  will be understood to be applicable to many other designs, including the first alternative embodiment casing  4 . 
     Switch-type sensors, and some other sensors known in the sensing art, have a designed minimum degree of tilt before the switch is activated. Whether this minimum threshold is achieved mechanically, as in the case of a mercury switch, or electronically, is not critical to the performance of the invention. However, incorporating a minimum tilt angle required for activation prevents reversals when the tilt angle is only minor and not significant enough to reflect a consequential movement of paint balls within a magazine chamber. 
     As should be apparent, it would be undesirable to design a system which attempts to rotate first in one direction and then another in too small a time frame. Such rapid switching would not only draw excessive power and potentially generate unwanted noise and vibration, but such movement would also potentially result in an effective stalling of motor shaft  305 , effectively completely disabling agitator  300 . Clearly, that is not the intent. Most preferably, delay between motor direction reversals will be designed into the system to reflect the time necessary for the tilt to have an effect on feed rate in a positive way. Said another way, there is a finite and measurable maximum reversal speed which will provide a beneficial increase in feed rate. This rate will depend upon a large number of variables, including the size and shape of the agitator  300  and magazine  210 , mass and geometry of the motor, type of motor winding and core, transit speed of the paint balls, and other diverse factors too numerous to mention. If not determinable theoretically or any other way, the system can be tested experimentally through builds where different reversal rates and the changing of the myriad of other variables can be tested using known test matrices, to optimize performance. 
     Delay between motor reversals is controllable through motor design, but is more preferably varied using electrical or electronic means and adjusted to accommodate a particular motor type and characteristic. In the most preferred embodiment, relay  460  is in fact an H-bridge circuit constructed from MOSFET transistors, and most preferably the MOSFETs are of the type which incorporate flyback diodes directly into their construction to prevent damaging spikes from being generated. The H-bridge construction is known in the field of motor control, and based upon the present teachings will be applied herein in the field of paint ball guns. The use of this type of electronic motor control enables an output  602  from tilt sensor  600  to be fed through additional electronic control circuitry which may either form a part of tilt sensor  600 , a part of relay  460 , or a separate component. This additional electrical motor control function will most preferably incorporate an optimum minimum time for the particular paint ball magazine design, during which time magazine  210  or casing  4  must remain tilted before the H-bridge output is reversed. This can be accomplished, for example, through the use of a typical R-C circuit and threshold detector, and can even be adjustable through the use of a variable resistor or rheostat. 
     The electronic components used to detect the minimum duration time will affect the behavior of the motor and agitator very directly, and should therefore be chosen carefully. More particularly, the R-C circuit mentioned or similar components will tend to act as an accumulator, averaging the tilt signal. Averaging of the tilt signal will permit the tilt signal to be discontinuous, permitted to occasionally, albeit briefly, turn off. Turning off briefly will only be interpreted by an R-C accumulator or the like as slightly lowering the average. Consequently, the time required to trigger a motor reversal may be longer, owing to the lower average due to the brief turn-offs of the tilt sensor, but the average will still indicate generally continuous tilt, and, with this type of circuit could consequently trigger a motor reversal. Said another way, if the gun operator tilts the gun in one direction for a vast majority of a time period, but during that time period one or more times jolts the gun or otherwise very temporarily disables the tilt sensor, an R-C or accumulator circuit will still identify this as an indication that the gun is tilted. Since this behavior is felt to most closely resemble the actual paint ball and magazine behavior, it is most preferred to use this type of minimum time duration measurement, and select an R-C time constant which most closely matches the movement of paint balls within the magazine. 
     Nevertheless, and as an alternative, it is conceived herein to use circuitry which requires the tilt signal to remain continuously on during the time period before reversing the motor. This type of circuit would most preferably be used where the sensor itself incorporates some delay, such as a sensor having a large hysteresis, or a high mass which is little effected by momentary or temporary jolts. There may, however, be times or situations where a designer deems it appropriate and most effective to require the sensor signal to be continuous, even when the sensor does not incorporate any inertia or hysteresis. Regardless of the technique used, the end result will be to reverse the output  524  from relay  460  when paint ball gun  100  has been tilted for a time deemed sufficient to warrant agitator reversal. 
     FIG. 8 illustrates the relationship between signals  236 ,  512 ,  522 , and  524 . Timer  520  may be a simple RC filter, or may comprise a more complicated circuit such as a  555  type timer or even a voltage controlled oscillator. The exact components used to fulfill the timing function are not critical to the invention, so long as the timing diagrams illustrated in FIG. 8 hold true to intent. As evidenced therein, when output  602  switches from a zero-voltage state to a positive V T  value, this will indicate gun tilt in a first direction. When this tilt occurs for a sufficient time T min , and presuming the gun is already not rotating in a direction appropriate for this direction of tilt, output  524  will reverse from a positive output shown to an inverse thereof, and thereby reverse the motor. Since many of these magazine motors are DC permanent magnet motors, this may, for example, be accomplished by shutting off the output  524  briefly, allowing the flyback diodes to dissipate any voltage spikes from the decay of the inductive field and the stopping of the motor, and then reversing the output  524  polarity. Later, when the gun is tilted back to an opposite direction for a sufficient time T min , the output  524  may once again be reversed, preferably again after a small delay. 
     FIG. 7 illustrates an additional filter  515 . This filter  515  may be a low, high or band-pass filter, depending upon the particular gun firing frequencies. Most typically, this will be a band-pass filter having a very narrow bandwidth, such that one or a few specific frequencies are selected which are only indicative of firing. The inclusion of filter  515  will help to prevent false triggering of motor  470  when other events occur that produce sound, such as when gun  100  is accidentally bumped against another object. While filter  515  is not essential to the proper functioning of circuit  500 , some frequency discrimination may be desired, particularly for higher level competitions or premium guns and magazines. Filter  515  may be provided prior to amplifier  510 , after amplifier  510  as illustrated, or integral therewith, particularly where operational amplifiers are used and gain may be readily combined with frequency selectivity. 
     An additional optional feature is illustrated in FIG. 7, by providing counter  525 . Counter  525  provides feedback to timer  520  which is used therein to effect a change in timing duration. More specifically, every n times a pulse indicative of firing occurs, counter  525  adjusts the timing control of timer  520  to change duration of pulses on waveform  522 . For example, as shown in FIG. 8, pulse  523  may be twice the duration of pulse  521 . In the preferred embodiment, n might be equal to four, so that every fourth shot, timer  520  provides a one second pulse instead of the normal one-half second pulse. The increased duration may be achieved through the use of a transistor or other switch connecting or removing an additional timing component into/from the circuit, as is known in the art, or may alternatively be the result of a voltage control signal applied to a voltage controlled oscillator. These and a myriad of other frequency control techniques are well known in the art of timing duration control, and that knowledge is recognized as incorporated herein. This change in duration ensures that every nth shot, the magazine is thoroughly stirred to help ensure balls remain available. The value of n is preferably equal to the number of balls that are retained within feed tube  215 , to ensure that feed tube  215  never empties, while still minimizing the duration of the majority of stir cycles to help conserve battery power. 
     By now, those skilled in the art of electronic circuitry and microprocessor control will recognize that the electronic circuitry can be implemented through a microprocessor or microcontroller and associated circuitry. Since microprocessors and micro-controllers are accompanied by a clock, timing measurement and control is readily accomplished. Where desired, accumulation is accomplished by simple measurement and repeated arithmetic summing. Finally, the digital output ensures clean electronic switching, a feature which is very important for improved battery performance. Certainly all logic comparisons and calculations are easily accomplished through the use of a micro-controller or microprocessor. 
     An additional benefit of the present motor control is obtained by providing a motor double-rotation function. This motor double-rotation will most preferably involve powering of the motor separate from any firing detection. Moreover, the power will be applied to most preferably rotate the motor in one direction for a brief interval, followed by reversal of the motor for a second brief interval. The initiation of motor double-rotation may be accomplished in one alternative embodiment through activation of a switch on the motor housing or magazine, such that if a gun should jam, the operator can press a button or otherwise trigger a switch, leading to a rapid reversal of the agitator and a consequent freeing of the jam. In another alternative embodiment, the motor current or other measure of rotation may be electronically monitored. In the event the motor stops rotation when power is applied or other monitored parameter indicates a jam, the direction of rotation may be automatically reversed to free the agitator automatically. In yet a third alternative embodiment, the motor may be periodically reversed for brief intervals, irrespective of the actual existence of such a jam. The intervals, in this third alternative, are such that the motor and agitator will primarily and substantially rotate in a single direction, but short bursts of rotation in the opposite direction ensure continued free movement of the agitator. The double-rotation, whether manually activated or automatic, results in tremendous resistance to jamming, while tilt sensing offers improved feed rates. The combination of features requires little additional circuitry over that previously required in the prior art, and yet provides substantial benefit not heretofore available. 
     The tilt sensor and motor direction control discussed herein above is illustrated as required by the patent statutes in combination with a preferred and alternative embodiment magazines. It will be understood herein that the tilt sensor and motor direction control will be operative independent of the magazine, and consequently has applicability with many very diverse magazine designs and constructs. While the foregoing details what is felt to be the preferred embodiment of the invention, no material limitations to the scope of the claimed invention are intended. Further, features and design alternatives that would be obvious to one of ordinary skill in the art are considered to be incorporated herein. The scope of the invention is set forth and particularly described in the claims hereinbelow.