Apparatus and method for sterilizing, destroying and encapsulating medical implement wastes

Apparatus and method for sterilizing and encapsulating contaminated waste particularly medical implement waste in which a volume of thermoplastic compound having a melting point temperature-calibrated at a value which corresponds substantially to the temperature at which all biological contamination is rendered sterile substantially on contact, and impregnating a space containing contaminated waste items with the liquid compound and thereafter cooling the mass to its solidified phase while containing it against protrusion of any waste item.

The invention is directed to safe handling and disposal of hazardous waste 
such as medical implement waste from hospitals, health care facilities and 
dental and medical offices. It is particularly concerned with safely 
processing contaminated needles, scalpels and like sharp metal objects 
which have invaded the human body, as well as used hypodermic syringe 
barrels and glass vials, all of which are difficult and dangerous to 
handle, destroy or eventually store. 
BACKGROUND OF THE INVENTION 
Environmental protection laws at all levels of government are concerned 
with contaminated medical wastes. In most jurisdictions of the civilized 
world such wastes can no longer be put in the conventional channels of 
waste disposal. Nor can much of such wastes be reliably rendered safe in a 
practical, discernible way at the point of use. On-site sterilization, for 
example, of many medical implements is giving way to the use of disposable 
implements because sterilization is labor-intensive, subject to human 
error and all but impossible to verify. Used hypodermic syringes are 
possibly the most dreaded waste of all because they are inherently 
contaminated and dangerous to handle; they resist decay and can float on 
an ocean until a shore is found. And they are sought by the illicit drug 
trade. 
Until recently medical facilities were required to shear off the needle 
part from the syringe body immediately after the injection, but this 
procedure was found to spread disease by means of the air-borne aerosols 
generated by the mechanical shearing action. Also, the sharp, contaminated 
needle tip remained to be handled and disposed of. Current regulations 
call for dropping the contaminated syringe with needle intact into a safe 
container, called a "sharps" box, for custom delivery to an authorized 
repository. 
A state of the art device destroys the needle at the point of use by 
passing a large current at low voltage through the needle to reduce it and 
all attendant contaminants to a minute, sterile, incinerated residue. That 
invention protects the nearby medical personnel and the environment but it 
cannot cope with scalpels, glass or the left over hollow barrels of the 
syringes. Thus the medical facility, while performing a useful service to 
itself and society, is left with its other contaminated "sharps" and 
syringe bodies to ship to a safe repository. For its otherwise good 
efforts it has saved neither time nor cost. There is also in the prior art 
a technique for rendering sharp items less dangerous by potting in resin 
such as epoxy using a hardener. Encapsulated spores can, however, survive 
for years and the system is regarded as unsafe for lack of sterilization. 
The present ground rules for dealing with medical instrument wastes not 
destroyable safely on the site call for: (1) minimum handling at the point 
of use, that is the person performing the injection, for example, is 
expected to drop the used syringe directly into the "sharps" box; (2) 
containerizing the waste by means of a sealed "sharps" box marked 
"hazardous", and (3) logging and shipping the containerized, contaminated 
waste to a special repository under an umbrella of costly manifests which 
must circulate among the facility, the hauler and the repository and then 
kept available for audit for several years. The expense to society is 
enormous and the beaches of the world reveal the flaws in the system. 
The present invention is a fresh attempt to solve the problems. Its objects 
and features are: 
to provide a relatively inexpensive container to receive the medical 
instrument waste at the point of use, 
to provide a way to sterilize inexpensively the contaminated contents 
within the container while still at the medical facility, 
to render the syringe bodies in the container not only unusable but 
unidentifiable, 
to render the needles, the scalpels and the glass harmless against cutting 
or piercing personnel and to render them unrecoverable by any practical 
means, 
to provide a containerized sterilizing system which is reliable and 
virtually immune to human error, 
to provide a containerized sterilizing system which clearly indicates even 
to the casual observer whether the contents have been rendered harmless 
and safe, 
to provide a containerized medical implement waste disposal system in which 
neither the treated container nor its contents can float, 
to provide a reliable, relatively inexpensive method and apparatus to treat 
contaminated medical implement wastes at the point of use in a manner 
which renders them capable of being thrown out in the ordinary channels of 
waste disposal, and 
to provide a containerized sterilizing system for medical implement waste 
which if desired lends itself to recycling. 
BRIEF SUMMARY OF THE INVENTION 
In accordance with the invention a container similar in size and shape to 
existing "sharps" boxes is formed of a material having a high melting 
point and is provided with a lower portion containing a predetermined 
volume of a temperature-calibrated thermoplastic compound forming a 
stable, rigid base. The melting temperature of the compound is selected at 
a value at which sterilization of biological contamination is effected 
virtually upon contact. Used medical implement waste such as hypodermic 
needles, scalpels, glass vials and hypodermic syringes, with or without 
the needles, are accumulated in the container in the conventional manner. 
The full container is heated by appropriate means such as an oven to a 
temperature above the melting point of the temperature calibrated 
compound. When the compound liquifies pressure is applied to cause the hot 
liquid to flow into the space containing the pre-heated waste products, to 
flow over and around all bits and pieces and to fill all void spaces. The 
container is vented at the top and the flow continued preferably until the 
liquefied compound appears at the top. All biological life has then been 
killed. 
In a preferred embodiment, the container is collapsible from the bottom up 
to eliminate the space where the compound was originally stored. It is 
this feature which provides an error-free, highly conspicuous indication 
that the sterilizing and encapsulating steps have occurred within. If 
desired, the outside of the container can be color and word coded to show 
the hazardous made before the container is reduced in size and the safe 
mode thereafter. 
The container is held in its reduced-size condition until the compound has 
cooled and hardened to encapsulate and shield all sharp points and edges 
and to lock the container in its new geometry. Glass vials, if not broken 
upon insertion can be broken by the pressure, and the plastic of which 
disposable syringe bodies are made, having a melting temperature 
substantially below that of the compound, will be reduced to an amorphous, 
void-free mass. Thus there are no visually identifiable or usable syringe 
parts remaining in the final mass. The container is now hazard-free and 
can be disposed of in the conventional channels of waste disposal either 
at a land fill or an incinerator. It is also capable of recycling to 
retrieve the compound and the metals of which the medical implements were 
made, should such be desirable for any reason.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1-4 the invention is illustrated as embodied in a 
container 10 formed of a heat and puncture resistant material such as high 
melting point plastic, of which nylon and teflon are examples and which 
can be reinforced, or of metal. The container 10 is cylindrical and 
includes a rigid upper portion 11 defining a chamber or space 12 to 
receive waste implements such as hypodermic needles, glass vials, scalpels 
and like wastes produces which in the medical and dental professions are 
now known as contaminated "sharps". Syringe bodies, with or without the 
needles attached, can also be included, such typically being of the 
single-use, disposable type formed of thermoplastic. The upper portion 13 
of the container is preferably convergent to form a relatively small 
waste-receiving opening 14 having a depending cylindrical wall 15 and 
closed by a detachable vented cap 16. 
The lower or base portion of the container comprises a collapsible storage 
space 18 containing a thermoplastic medium 19 which is temperature 
calibrated as to its melting point selected to achieve sterilization of 
all known biological micro-organisms including vegetative bacteria, 
viruses and spore forms. A typical material for this purpose which is 
relatively harmless to the environment is linear, hydroxy terminated 
copolyester synthetic resin which can be formulated to afford full flow 
viscosity at temperatures from 160.degree. C. to in excess of 260.degree. 
C. Such products do not vaporize or generate toxic fumes until temperature 
in excess of 300.degree. C. are reached. They are marketed for other 
purposes under such trademarks as dynapol and Jet-Melt. 
Most medical researchers studying the effects of heat as a means of 
sterilizing refer to a temperature coefficient model in which death of the 
mirco-organisms being studied (death time) is plotted as a function of 
time and temperature. Research strongly indicates that no known 
micro-organisms can survive temperatures in excess of 160.degree. C. for 
longer than a fraction of a minute. See "Disinfection, Sterilization and 
Preservation", by Seymour S. Block, Lea & Febger, 1983. It should be 
understood however that there is a given range of times and temperatures 
below 160.degree. C. which effectively kill all known micro-organisms. It 
is therefor possible to design systems whereby plastics having melting 
temperatures less than 160.degree. C. are allowed to remain in contact 
with the micro-organisms for time consistent with the death times of the 
organisms. The preferred embodiment however makes use of plastics having 
temperatures high enough to kill the micro-organisms substantially on 
contact, and thereby provides a fail-safe degree of overkill. Also, the 
system of the present invention provides an inherent time constant 
representing the time for the liquid phase thermoplastic to revert during 
cooling to its solid final phase without requiring a timing function 
subject to human error. 
In dry gaseous media such as hot air having relatively lower specific heat 
characteristics, either higher temperatures or measurable time constants 
for heat exposure come into play. In the preferred embodiments of the 
present invention, liquid phase contact at temperature achieving rapid 
death to all biological contaminants in their most heat-resistant form, 
i.e. the spore form, is desirable because it eliminates the possibility of 
human error in the operation of the system and renders the successful 
operation visually discernible at a glance from a substantial distance, 
all of which are vital in policing the environment for human 
life-endangering contamination. 
The appearance of the thermoplastic material at the vented cap will 
indicate that the entire space 12 has been impregnated with molten 
plastic. To provide for the possibility that the displacement factor of 
the waste items in the space 12 will have a range of values a surplus of 
thermoplastic can be provided together with an overflow reservoir 13a in 
the form for example of a visible, open cup surrounding the cap. To 
accommodate a situation in which the waste items 17 only partially fill 
the space 12 the conical upper portion 13 can be made collapsible under 
pressure int he encapsulating phase as described below. 
The temperature-calibrated thermoplastic medium 19 in the embodiment of 
FIGS. 1-4 is illustrated as solid although it can take the form of 
particular matter or granules. To hold the granules in place prior to 
melting a covering screen or perforate cover (not shown) can be secured to 
the container above the material. 
The wall of the base portion 18 of the container is made collapsible by 
corrugation or accordion pleating locked in its open position (FIGS. 1 and 
3) by the solid phase of the thermoplastic medium 19 and also locked in 
its collapsed position (FIGS. 2 and 4) by the same medium. If it is 
desired to make the container self-actuating (in the presence of heat) the 
collapsible wall can be made resilient with its stable or rest position 
collapsed. To this end a coiled tension spring (similar to the spring 37 
in FIGS. 5 and 6) can be included inside or outside the container if 
additional force is required. Additional force can also be derived from 
the use of heat shrinkable plastic in the container walls either on the x 
or the y axis or both. 
The sterilizing and encapsulating action in the illustrated embodiment are 
carried out by a special oven 20 shown in FIGS. 9 and 10 which provides 
the forces necessary to compress the container. The over 20 includes a 
compression spring 21 resting on a support 22 and carrying a perforated, 
corrugated plate 23 on which the filled container 10 (FIGS. 1 and 3) is 
seated. The spring 21 is compressed by the closed oven cover 24 pressing 
down on the container cap 16. A resistance heater 25 energized from the 
mains through a switch and thermostat 27 provides the controlled heat to 
liquefy the temperature-calibrated thermoplastic mass 19. As heat is 
applied, below the level to harm the container and above the level to 
liquefy the thermoplastic, melting will gradually occur at which time the 
liquefied thermoplastic at a temperature pre-selected to destroy the 
biological contaminants in the waste items 17 will begin to flow into the 
interstices around the preheated bits and pieces of waste in the space 12. 
The biological contaminants are destroyed substantially upon contact and 
all sharp edges and points become encapsulated. Also, the collapsible 
bottom 18 of the container will compress, thereby changing the geometry 
and appearance of the container. Gaseous by-products vent from the cap 16 
and through a suitable filter 26, including charcoal, for example in the 
cover 24 of the oven and, if desired an evacuation conduit 26a. 
Alternatively, or in addition the oven can be vented to the outside air, 
as is conventional in autoclave operation. The cooled container is thus 
rendered hazard-free and can be discarded in the conventional channels of 
commerce by conventional carriers. Thermoplastic syringe bodies in the 
container melt at temperatures below the calibrated temperature and are, 
therefore, melted down and destroyed as an unstable, irretrievable, 
unrecognizable part of the sterile, amorphous mass. 
The oven 20 can be operated by a position sensing switch actuator 28 which 
is activated by the carrier plate 23 to initiate heating when the plate is 
lowered and to terminate heating when it lifts (FIGS. 9 and 10). The 
actuator can also be coupled to the cover 24 to release a latch when the 
heating cycle is completed. The cover can be spring biased to an open 
position when released to hurry the cooling cycle, and residual 
compression in the spring 21 can expose more of the container to the 
atmosphere and also position it to be easily manually removed. 
The thermoplastic mass, when cooled, locks the container in its compressed 
condition to mark its sterile non-hazardous condition. If desired, as best 
seen in FIGS. 3 and 4, the concave or depressed portions of the base can 
be color coded in red to indicate the hazardous state and a word to that 
effect can be included. The outer edges can be marked so that when 
compression has occurred the word "safe" appears and the hazard indicator 
disappears. Because the thermoplastic mass 19 has been selected for a 
melting temperature close to or above that which sterilizes on contact, 
the system becomes error proof and visually verifiable. It will be 
understood that a certain margin for error is built into the system in 
that a finite time factor for killing by heat is inherent in the system 
representing the time for cooling down to the solid plastic. Thus it is 
not essential that the temperature of the thermoplastic liquid actually 
reach that which kills instantaneously, although it is preferred where 
possible to establish safety factors using both elevated temperatures as 
well as any time factor which is inherent in the time required for the 
temperature of the thermoplastic to drop to that at which the solid phase 
occurs. 
Referring to FIGS. 5 and 6 another embodiment of the container is disclosed 
in which the container 30 is formed of telescoping base and top sections 
31 and 32, respectively. As in the embodiment of FIGS. 1-4, the upper part 
33 of the top section 32 is conical. Normally solid phase thermoplastic 34 
fills the base 31 with waste items 35 filling the upper section, shown 
closed by a vented cover 36. If desired the two telescoping sections can 
be linked by a coiled tension spring 37 joined at its top to the section 
32 and its bottom to the base section 31. The container is adapted to be 
placed in an oven similar to that of FIGS. 9 and 10 to liquefy the 
thermoplastic and thereby set up the sterilizing and encapsulating 
functions, resulting in the configuration of FIG. 6. Hazard warnings in 
the cylindrical part of the upper section will, appropriately, be obscured 
by the lower section. It will be understood that heat destroyable warnings 
can also be used. 
Referring to FIGS. 7 and 8 another embodiment of the invention is disclosed 
in which the container 38 is formed of a single piece having a cylindrical 
bottom 39 and conical top 40 with a filling opening 41 shown closed by a 
vented cover 42. The bottom portion 39 is open and has fitted thereon a 
piston 43 with a sealing ring 44. The bottom is filled with a volume of 
thermoplastic 45 of the type described above and the open space 46 above 
is shown filled (diagrammatically) with and array of waste items 47. A 
tension spring or other internal or external pressure means corresponding, 
for example, to the spring 37 of FIGS. 5 and 6 can be used. The filled 
container is then heated by, for example, an oven corresponding to the 
FIGS. 9 and 10 to drive the liquefied thermoplastic into the waste items, 
all as described above, to achieve the end result shown in FIG. 8. 
Another embodiment of the invention is shown in FIG. 11 in which the 
container 48 is itself formed of the temperature-calibrated thermoplastic 
resin having a wall volume corresponding to the volume required to 
impregnate and encapsulate the waste items 49 contained therein. The 
container 48 is encased in a woven filamentary outer wrap 48a to contain 
and shield the liquid phase of the thermoplastic and the waste items 49. 
The filamentary wrap can impart deformability to the structure either in 
selected areas or throughout to allow the liquefied thermoplastic to be 
forced into the waste mass and, if desired, to adjust the container volume 
automatically to accommodate loads of different sizes and having different 
displacement characteristics. The wrap can be made puncture proof. It can 
also establish the pattern of change in the geometry between the treated 
and untreated unit to provide for the desirable visual verification of 
completion of sterilization. 
Referring to FIG. 12 the entire sharps container 50 is formed from 
temperature-calibrated thermoplastic with no outer wrap or outer 
container. When filled with waste items 51 the container 50 with a vented 
cover 52, which can if desired be weighted, is dropped into a potting 
container 53 having tapering walls with a smooth parting surface formed 
for example of Teflon. The assembly is then heated in an oven to melt the 
thermoplastic container 50 to a sterilizing temperature of liquification 
at which time the gravity pressure causes encapsulation and impregnation 
of the waste items 51. When cooled and solidified the amorphous sterile 
mass is removed from the potting container 53 for disposal as 
environmentally safe material via conventional disposal means. 
While the invention has been described having reference to preferred 
embodiments it will be understood that it can take other forms and 
arrangements. For example, the temperature calibrated thermoplastic 
compound can be materials other than plastic, so long as the material in 
its molten state is compatible with the temperatures required in the 
time/temperature death rate curve and has appropriate liquid and solid 
phases. It is also important that the molten material be brought into 
intimate contact with the contaminated waste material. In addition to the 
preferred embodiments herein disclosed it will be understood that this can 
be augmented by rolling, tumbling, shaking, vibrating, and air evacuation 
devices. Partial evacuation of the container can perform the manifold 
functions of aspirating waste gases, augmenting the flow of the 
liquid-phase plastic into all voids and of providing some or even all of 
the compression forces to cause the distortion of the container. This 
distortion forces the liquid into the mass of waste implements and, at the 
same time, provides for the easily viewed indication of successful 
completion of the sterilizing cycle. In the preferred embodiments the 
essential operational functions have been divided between the oven and the 
container. For example, the oven is the source of controlled heat as well 
as the pressure, i.e. the spring 21, to extrude the liquefied sterilizing 
medium into the mass of waste pieces. As disclosed, some or all of this 
pressure can be generated solely within the container itself by, for 
example, the internal spring 37 (FIGS. 5 and 6), the resilience of the 
base 18 (FIGS. 1-4) or the heat shrinking forces of certain plastics. It 
will be understood that it is possible to generate heat by different means 
such as chemically within the container itself or by means of microwave 
energy focused on the solid plastic. The latter can be rendered more 
susceptible to such heating by means of carbon dielectric fillers. It is 
also possible to establish more of the functions externally of the 
container by, for example, generating the liquefied sterilizing medium 
externally and injecting it into the waste filled containers, which can be 
partially evacuated to augment the liquid flow to create a void-free mass 
and which can also provide a force to deform the container to provide a 
visual indication that the process has been completed. The invention 
should not, therefore, be regarded as limited except as defined in the 
following claims.