Sharp instrument encasement system

A sharp instrument encasement system is disclosed for encasing the sharp points or edges of medical instruments. The system comprises a container having two fluid-tight compartments separated by a frangible membrane, one compartment containing a hardenable resin and the other containing a filler comprising a particulate material that is substantially incompressible. Upon insertion of a medical instrument through a penetrable top and through the frangible membrane, the contents of the compartments mix, creating a reaction that hardens the resin and particulate material mixture and encases the sharp portions of the medical instrument.

TECHNICAL FIELD 
The present invention relates to the safe disposal of medical instruments 
having sharp edges or points that may be contaminated by various 
infectious diseases. More particularly, the invention relates to an 
apparatus and method for rapid encasement of the sharp portions of medical 
instruments such as hypodermic needles, suturing needles, lancets, 
trocars, and scalpel blades, within a hard substance which permits quick 
disposal at the point of use of the medical instruments. 
BACKGROUND OF THE INVENTION 
The safe disposal of sharp, contaminated medical instruments is a major 
health care problem. Numerous infectious diseases can be transmitted to 
other persons through contact with the contaminated instruments during the 
disposal process. Hypodermic needles, trocars and other instruments that 
retain body tissue and fluids therein are particularly dangerous and are 
known to transmit such diseases as the AIDS virus, hepatitis, syphilis and 
tuberculosis. Disposing of the used medical instruments within the 
operating rooms, patient rooms and laboratories is a task that exposes the 
doctors, nurses and other hospital employees and visitors to inadvertent 
injuries and exposure to disease. Injuries frequently have occurred while 
trying to cap hypodermic needles in preparation for their transport and 
disposal through incineration or other means. Current procedures require 
the collection and removal of the dangerous "sharps" to another site for 
decontamination, encapsulation or other protective measures. This means 
that the unprotected medical instruments remain on the "hospital floors" 
while awaiting collection and transport permitting unauthorized retrieval 
of such equipment for improper uses. The greater the handling of the 
unprotected "sharps", the greater the opportunity for injury and 
infection. 
Two patents issued to Honeycutt, U.S. Pat. Nos. 4,816,307 and 4,900,500 and 
a patent issued to Donovan, U.S. Pat. No. 4,845,923 each disclose methods 
for encasing "sharps" in containers containing resins which harden and 
encapsulate the instruments. The processes identified in these patents are 
still slow reacting, do not provide a capsule that is resistent to 
crushing and in some cases require handling of chemicals by the staff at 
the point of use. It is clear that a device that accepts the instruments 
immediately after use and quickly encases the sharp portions of the 
instruments upon the simple insertion of the instrument into an individual 
container is needed. 
SUMMARY OF THE INVENTION 
Briefly, this invention comprises a container which is sized to receive at 
least the sharp portion of at least one instrument. The container has a 
flexible top that is penetrable by the sharp instrument and further 
comprises two fluid-tight compartments that are disposed one above the 
other with a frangible membrane therebetween. A filler that is comprised 
of a substantially incompressible particulate material is in one of the 
compartments and a hardenable resin is placed in the other compartment. 
Upon insertion of the medical instrument through the penetrable top and 
into the container, the frangible membrane is shattered permitting the 
contents of each of the compartments to mix with one another so that the 
resin and the filler adhere to and harden about the sharp portions of the 
medical instrument.

DETAILED DESCRIPTION 
A preferred embodiment of the sharp instrument encasement system is 
illustrated in FIGS. 1-3 in which the apparatus, or encasement unit, is 
generally indicated as 10. FIG. 4 illustrates a second embodiment, which 
is indicated as 110, and all other reference characters for this 
embodiment correspond to those for FIGS. 1-3, incremented by 100. The 
apparatus is used to protect persons who are exposed to used and 
contaminated sharp medical devices that include, but are not limited to, 
hypodermic needles, trocars, and any other medical device with a sharp tip 
or edge that is connected to a hollow body that can house a bacteria or 
virus. Also, scalpels, lancets, and other medical instruments that have a 
sharp tip or edge may be disposed of in the same or similar apparatus. 
As seen in FIG. 1, the apparatus 10 comprises a container 12 suitably 
formed of a generally rigid synthetic resin and preferably one that is 
transparent or translucent, which container has a penetrable top 14 formed 
of a resilient, rubber-like synthetic resin and a frangible membrane 16, 
which divides the container into two fluid-tight compartments, a lower 
compartment 18 and an upper compartment 20. The container 12 may be made 
to any suitable size to accept the sharp portions of most sharp medical 
instruments. In this particular preferred embodiment only the sharp 
portions of the instrument are received within the container 12; however, 
larger containers could be made to accept the whole medical instrument if 
it were deemed desirable. The encasement of the sharp portions of a 
hypodermic needle 22 is illustrated in FIG. 5, with a corresponding unit 
for a scalpel 24 illustrated in FIG. 6. 
One compartment of the apparatus contains a hardenable resin 26, preferably 
a cyanoacrylate ester, and the other compartment contains a filler 28 that 
is comprised of a particulate material having a high modulus of a 
hardness, such as a fine grain silica sand, which is substantially 
incompressible. In the preferred embodiment a methyl cyanoacrylate is 
preferred over ethyl or purple cyanoacrylate, although the two latter 
materials can be used if desired. The viscosity of the resin may be easily 
adjusted, but a consistency generally similar to that of water is 
generally preferred to ensure rapid penetration of the voids between the 
grains in the filler 28 when the two components are combined. The grain 
size of particulate matter of the filler 28 may be sized to be received 
within the apertures of any of the medical instruments that are to be 
disposed of with this apparatus, particularly hypodermic needles. By 
filling the needle with resin and filler a better bond will be obtained. 
There should be enough filler 28 within the container 12 to ensure 
covering the sharp portions of the instrument, and there should be enough 
resin 26 to fill the voids of the filler 28. 
In the preferred embodiment an accelerator is used to speed up the 
hardening of the resin 26 and filler 28 mixture. The length of time that 
it takes for the resin 26 to harden is important. If the reaction is too 
slow, it becomes a safety problem, as the instruments may be removed from 
the container before the resin has hardened about the instrument's sharp 
edges. If the reaction is too fast, the resin will harden before it has 
substantially penetrated the voids of the filler 28, preventing a complete 
seal about the medical instrument. The type of resin and amount of any 
accelerator to be used generally determines the speed of reaction. In the 
preferred embodiment the accelerator is a strong base, such as sodium 
bicarbonate, which is mixed with the filler 28 in the proportions 
necessary for optimal hardening. Approximately a one to one ratio of 
sodium bicarbonate to sand by volume will provide a reaction time of two 
to three seconds, which is considered desirable. In other embodiments 
para-toluidine may be used as an accelerator, and it may be applied to the 
particles of the filler as a coating for even distribution of the 
accelerator. 
In one embodiment, to ensure complete mixing of the resin 26 with the sand 
filler 28, a pressure differential is established between the 
compartments, the compartment holding the filler 28 having a lower 
pressure than the compartment holding the resin 26. For example, as 
mentioned previously, in one embodiment the sand and sodium bicarbonate 
mixture is placed in the lower compartment 18, and the resin is placed in 
the upper compartment 20. When the frangible membrane 16 is breached by 
the instrument 22, as shown in FIG. 2, the liquid resin 26 is rapidly 
drawn by the lower pressure into the lower compartment 28, meeting less 
than normal resistance from trapped air, as the voids have been at least 
partially evacuated. In other embodiments, where there is no pressure 
differential between the compartments, gravity is relied upon to cause the 
liquid resin 26 to flow into the filler 28. In the embodiment illustrated 
in FIG. 4, the filler 28 is placed in the upper compartment 120 so that, 
when the frangible membrane 116 is broken, the sand/sodium bicarbonate 
filler mixture falls into the lower compartment 118 by gravity, mixing 
with the resin 26. 
The frangible membrane 16 is preferably made from thin glass; however, a 
frangible plastic with similar properties may work as well. The glass or 
plastic membrane 16 may be etched to provide increased frangibility. It is 
desirable that the membrane 16 shatter rather than puncture so that the 
materials will pass through the breach in the membrane 16 quickly. 
The penetrable top 14 is made of a flexible material such as rubber or 
other flexible synthetic resin that is well known and suitable for this 
purpose. Upon insertion of the instrument through the flexible top 20, the 
flexible material of the top 20 clings to the sides of the medical device, 
wiping off most of the attached tissue or other material 32 as shown in 
FIG. 2. This will both reduce contamination and improve bonding by the 
resin 26 to the instrument. 
For ease of handling a plurality of the containers 12 may be joined to one 
another by frangible connectors 36, as shown in FIG. 5, to form a grid 38. 
The individual containers 12 may be removed from the grid 38 by breaking 
the adjacent connectors 36. The containers 12 may alternatively, be joined 
to one another by inserting them into a tray 40 having a plurality of 
holes 42 therethrough. The holes are sized and configured to receive a 
container 12 in each hole. Individual containers 12 may be removed for 
disposal or held by the tray 40 until all are used. The grids 38 and the 
trays 40 may be fabricated as squares, rectangles, strips or in any other 
suitable configuration. 
With the apparatus of this invention described above, a typical mode of 
operation of one embodiment may now be described. For such operation the 
apparatus of the sharp instrument encasement system may conveniently be 
placed on the carts or at the work stations of the nurses and doctors 
where the instruments are being used. For example, after a nurse gives an 
injection, the hypodermic needle 22 is inserted immediately, point first, 
into a container 12, so that the needle shatters the frangible membrane 16 
and penetrates into the filler 28. As the needle is inserted into the 
container, much of the tissue, fat cells or other materials 32 clinging to 
the outside are wiped from the exterior of the needle by the penetrable 
top 14 as shown in FIG. 2. As the needle is inserted into the container, 
resin may flow into the needle to react with the granules of filler with 
accelerator that are forced into the needle aperture as the needle 
penetrates the filler. This will then cause the point to be blocked by the 
hardened resin. When the membrane 16 is shattered by the needle 22, the 
lower pressure in the compartment holding the filler rapidly draws the 
resin into the voids of the filler. The resin reacts with the accelerator, 
becoming hard within a few seconds, suitably two or three seconds. The 
reaction of the resin 26 with the accelerator creates a toxic, exothermic 
reaction that kills most bacteria and viruses that are present. A coloring 
agent, of a type well known in the art, may be added to the filler so that 
the filler changes color upon completion of the hardening of the resin, 
signifying that the encapsulated medical instrument is now safe for 
disposal. 
While the foregoing has described a particularly preferred embodiment and 
several additional embodiments of the sharp instrument encasement system, 
it is to be understood that this description is illustrative only of the 
principles of the invention and is not to be considered limitative 
thereof. Because of numerous modifications and variations of the disclosed 
apparatus, all within the scope of the invention, will readily occur to 
those skilled in the art, the scope of this invention is to be limited 
solely by the claims appended hereto.