Abstract:
Biohazardous needles are destroyed by the application of an electrical arc that progressively destroys the needle and seals hollow needles. An elongate electrode that slopes up and away from the needle supports is used to strike an then progressively support the destructive arc.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the destruction of biohazardous needles and, in particular, to the electrical destruction of used hypodermic needles. 
     Increasing emphasis has been placed on protecting patients and health professionals from needle sticks that may spread such pathogens as hepatitis and HIV. Various disposal containers have been used. Needles with various shielding schemes have been employed. Devices that cut needles have been tried. 
     To destroy the needle itself, devices have been used that melt the needle by connecting the needle across a large current source. Such devices require an extreme amount of current because of the relatively low resistance of the needle. This makes portable use impractical and line-powered power supplies expensive. In addition, this destruction mechanism soon destroys the contacts of the device as well as the needles. 
     SUMMARY OF THE INVENTION 
     An apparatus for destroying a biohazardous needle having a proximal portion and a distal tip portion includes: an upper electrode adapted to contact the proximal portion; a lower electrode; and an electric arc supply connectable between the upper and lower electrodes. The supply is adapted to produce an electric arc between the lower electrode and the distal tip portion to destroy the needle. 
     A method for destroying a biohazardous needle having a proximal portion and a distal tip portion includes: providing an electric arc supply having an upper and a lower output contact; connecting the upper output contact to the proximal portion; and creating an arc between the distal tip portion and the lower output contact where the arc progressively destroys the needle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a needle destroying apparatus according to the invention. 
     FIG. 2 is a perspective view with portions cut away of an apparatus according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a needle destroying apparatus  10  includes an upper electrode  12 , a lower electrode  14 , an arc power supply  16  and a control  18 . 
     The needle  1  may be advantageously immobilized by a shutter effect between a stationary aperture  20  and an aperture  22  in the plate-like electrode  12  when the electrode  12  is moved along the direction A. The electrode  12  may be moved by various mechanisms, including, for example, a manually operated linkage or camming action or such other well-known techniques as an electrically-operated solenoid or motor and gear train or linkage. The upper electrode may be, for example, comprised of stainless steel. It would of course be possible to maintain the electrode  12  stationary and instead move the aperture  20  (i.e., a member containing the aperture  20 ) 
     The electrode  14  may advantageously be an elongate member lying generally in a plane through the needle  1 . The lower portion of the electrode  14  is located closer to the tip or distal portion of the needle  1  than is the upper portion of the electrode  14  with respect to the upper or proximal portion of the needle  1 . In the preferred embodiment, the electrode  14  is a straight rod of a heat-resistant electrical conductor. The electrode may be, for example, stainless steel, or for higher heat resistance, tungsten. The electrode  14  may be, for example, a circular rod as long or longer than the needle to be destroyed and between 0.020 and 0.060 inches in diameter, with 0.032 inches preferred. 
     The electrode  14  may be mounted on a carrier more fully described below. The electrode  14  may be moved along the direction B by various mechanisms, including, for example, a manually operated linkage or camming action or such other well-known techniques as an electrically-operated solenoid or motor and gear train or linkage. As more fully described below, movement of the electrode along the direction B facilitates the striking of an electric arc between the electrode  14  and the needle  1 , as well as the removal of “ash” from the end of the needle  1 . 
     The arc power supply  16  provides high voltage between the electrodes  12 ,  14  sufficient to establish an air arc between the needle  1  and the electrode  14  while the proximal portion of the needle  1  is in electrical contact with the electrode  12 . The arc supply  16  provides sufficient current in combination with the voltage to destroy the needle  1  using the heat of the arc to a point close to the electrode  12 . 
     The arc supply  16  may include, for example, a battery or line powered oscillator driving a step-up transformer. The output of the arc supply may be, for example, about 25 milliamps at 800 volts for needles in the range of 27-32 gauge. Larger needles of 18-26 gauge may require about 125 milliamps at 800 volts. In general, a maximum arc distance of about one-quarter inch has been satisfactory. In the preferred embodiment, the arc supply  16  includes a full-wave rectifier that provides direct current to the electrodes  12 ,  14  with the electrode  12  having a negative polarity with respect to the electrode  14 . 
     The control  18  controls the operation of the apparatus  10 . The control  18  may be, for example, simply a manual switch to control power to the arc supply  16  or it may be a more complex device as described more fully below. 
     In operation, the needle  1  of a syringe or other biohazardous needle is inserted into the aperture  20 . The electrode  12  is moved to contact the needle  1  trapping it between the walls of the aperture  20  and the aperture  22 . The arc supply  18  is energized and the electrode  14  moved against the distal tip of the needle  1 , temporarily shorting the arc supply  18 , and the electrode  14  is then pulled away from the needle  1  thereby striking an arc between the needle  1  and the electrode  14 . The resulting arc melts/burns the tip of the needle  1  and the arc continues up the portion of the electrode  14  closest to the remaining lower portion of the needle  1 , progressively destroying the needle as the arc travels upward. 
     After the needle  1  is destroyed by the arc, the electrode  12  is released and the stub of the needle  1  withdrawn from the apertures  20 ,  22 . 
     The increasing distance between the electrode  14  and the needle  1  towards the upper proximal portion of the needle  1  helps ensure that the arc starts at the distal tip of the needle  1  and moves toward the proximal portion. This is due to a combination of air heated by the arc tending to push the arc upward balanced by the tendency for the arc to jump to the closest point between the electrode  14  and the needle  1 . The needle/electrode are not required to be in a vertical plane but the proximal portion of the needle  1  should be higher than the distal tip. The angle between the needle  1  and the electrode  14  may be, for example, between  10  and  15  degrees with 12 degrees being satisfactory. 
     In the case of hollow hypodermic needles, the apparatus  10  has the further advantage that the progressive melting of the needle  1  results in a melted bead of metal that both blunts and seals any remaining portion of the needle  1 . 
     By maintaining the electrode  12  negative with respect to the electrode  14 , it has been found that the majority of the heat from the arc is transferred to the needle  1  instead of to the electrode  14 , greatly improving the durability of the electrode  14 . 
     It has been found that the use of an air arc to destroy the needle, as opposed to destroying it with a short circuit, requires much less power and greatly improves the durability of the contact electrodes. The lower power required makes it possible to operate the device for small gauge needles such as insulin syringes on a few AA batteries for hundreds of needles. In this low power configuration, it is desirable to move the electrodes  12 ,  14  with a manually operated linkage that also operates a switch for the control  18 . 
     Referring to FIG. 2 a solenoid-based embodiment of the invention includes a carriage  24  carrying the electrode  14  at the bottom of a v-shaped groove. The carriage  24  may be, for example, an electrically insulating plastic or, for higher heat resistance, a ceramic material. The carriage  24  is mounted on the plunger of a solenoid  26  and the electrode  12  is mounted to the plunger of a solenoid  28 . A light emitting diode  30  and a phototransistor  32  are mounted about the needle  1 . 
     In this case, the control  18  uses the diode  30  and the transistor  32  to detect the presence of a needle  1 . The control  18  energizes the solenoid  28  to move the electrode  12  to contact and grasp the needle  1 . The control  18  also energizes the solenoid  26  to bring the electrode  14  into momentary contact with the needle  1  to strike the arc. 
     When operating with larger gauge needles, ash may be left in place of portions of the needle  1  resulting in interference with the progression of the arc. The solenoid  26  may also be energized by the control  18  to use the carriage  24  to periodically knock this ash loose. 
     For longer needle lengths, the electrode  14  can be advantageously increased in length also. This results in an electrode having an upper portion that would be much farther away from the needle  1  when the lower portion of the needle was in contact with or close to the distal tip of the long needle. This would then require a much higher voltage to sustain the arc at the proximal portion of the needle  1 . This would in turn negatively impact the required power, the dissipated heat and the required electrical insulation and electronic component working voltages. 
     As an alternative, the electrode  14  can be initially positioned in an intermediate position suitable for shorter needles. Then a longer needle can be sensed by the control  18  when the distal tip of the needle contacts the electrode  14  prior to the electrode  14  being moved to strike an arc. The control  18  can then energize the solenoid  26  (or another unshown solenoid) to move the electrode  14  further away to accommodate the longer needle. If the arc to the proximal portion of the longer needle extinguishes because of the further distance, the control  18  can energize the solenoid  26  to move back to the intermediate position and to then strike a new arc. Additional increments of movement by the electrode  14  can of course be employed to accommodate even a wider range of needle lengths. 
     The control  18  may include, for example, discrete logic or a microprocessor to perform the required control functions. 
     The present invention may be readily extended to neutralize not only biohazardous needles but also sharps in general such as sharp-edged surgical instruments like scalpels. Because of the large mass involved, the goal is to dull the cutting edge with an electrical arc rather than trying to destroy the whole blade. 
     In this case, rather than using an elongate electrode that roughly corresponds to the straight needle, a more localized (e.g., a point source) electrode is mechanically moved not just in one direction, but in two, to follow the contour of the cutting edge. Various edge tracking techniques can be used, but the preferred embodiment employs measuring the arc resistance to provide a measure of the distance between the electrode and the cutting edge. This measurement is then used to control servos that position the electrode. This device can of course also be used to destroy needles. 
     It should be evident that this disclosure is by way of example and that various changes may be made by adding, modifying or eliminating details without departing from the fair scope of the teaching contained in this disclosure. The invention is therefore not limited to particular details of this disclosure except to the extent that the following claims are necessarily so limited.