One-time use of hollow hypodermic syringe needles has become the norm in most health facilities because they cannot be reliably sterilized for reuse. The safe disposal of used needles has however, created a problem of its own; the cost to society is enormous and the end results have been less than satisfactory. Bulk incineration of accumulated syringes and needles at the point of use is an obvious but impractical solution because it cannot be accomplished easily, effectively or even safely. And once started toward the dubious but expensive channels of hazardous waste disposal prior to incineration or burial at a central facility the destiny of the syringes with their needles intact or of the needle assemblies per se seems to be all but uncontrollable.
Mechanical shearing devices have long been used at the point of use to sever used needles from their supports. While shearing goes far to prevent reuse of the needle particularly if it is sheared in sections, it is far from a sanitary solution. The severed parts remain sharp as well as contaminated and the shearing operation itself is believed to spread vaporized contamination as part of the shearing impact.
It has been known from the beginning of the electrical age that metallic electrical conductors having a low ratio of volume to surface area, of which a hollow needle is a classic example, will be incinerated when large electric currents are passed through them. A typical modern day device of this type is shown in U.S. Pat. No. 4,628,169 in which portions of the hypodermic needle are successively heated in relatively short sections from the tip inward to achieve incineration temperatures between fixed, spaced apart electrodes while the needle is still attached to the syringe body. No known prior art, point-of-use devices of this type, however, eliminate sharp needle stubs close to the syringe body and none is able to generate heat for a sufficient time to sterilize needle parts much beyond the points of electrode contact. Predetermined or optimized spacing of the fixed electrodes is not a solution to the problem because widely spaced electrodes, in which the spacing approximates the length of the exposed shaft of the needle, leave relatively long sharp stubs of needles attached to the syringe body, for reasons explained below. In addition, the time interval during which current can flow is minimal, with the circuit often being burned open before there is time for heat to be conducted to sections inward of the electrode coupling points to the needle shaft. Close electrode spacing, on the other hand, also restricts the time for the heat to flow along the needle to parts outside of the electrodes, such as those within the syringe body and, in addition, subjects the electrodes to becoming permanently short circuited by fused needle parts to shut down the entire process. And the most minimal practical electrode spacing nevertheless leaves a critical sharp needle stub requiring careful handling to overcome the latent contamination risks.