Syringe needle abstract
A hypodermic syringe needle destroying apparatus and method using
electrical resistance heating between electrodes which are convergent
either geometrically or by virtue of relative movement to conduct
incinerating currents first throughout the entire length of the
contaminated needle and thereafter over progressively shorter lengths
until the entire needle is destroyed. Any remaining needle stub
can be removed or deformed while in its heated state by impacting
it against a deforming barrier.
Syringe needle claims
What is claimed is:
1. Apparatus for destroying and sterilizing hypodermic needle assemblies
having a needle shaft, a needle shaft supporting hub and a body
portion carrying the hub, comprising,
first and second electrodes having a power source connected thereacross,
said electrodes having complementary positions spaced apart by a
distance corresponding approximately to the full length of the needle
shaft to be destroyed,
said electrodes being convergent to a point of close proximity,
the first electrode being adapted to be electrically connected
to the needle shaft at a point closely adjacent one end of the needle
shaft, and the second electrode being adapted to engage the needle
adjacent the other end to establish a flow of current through substantially
the full length of the needle shaft and, as the electrodes converge,
to progressively destroy the needle, whereby electrical resistance
heating of the needle shaft occurs along the full length of the
needle and what remains thereof at substantially all times current
is flowing between the electrodes during each destruction cycle.
2. Apparatus as set forth in claim 1 said first and second electrodes
being relatively moveable toward each other to a point of minimum
spacing.
3. Apparatus as set forth in claim 1 said electrodes being elongated
and convergent geometrically whereby the needle shaft when displaced
laterally causes the needle shaft to be destroyed in stages successively
inward from the tip to the hub.
4. Apparatus as set forth in claim 3 including a housing for said
electrodes said housing having an elongated slot parallel and complementary
to the first electrode for receiving the needle shaft and hub, and
a slide track on the housing to engage the body portion of the needle
assembly, said track being spaced from the first electrode by a
distance which supports the needle shaft in a position in which
the first electrode is electrically coupled to the hub end of the
needle shaft, whereby as the body is slid laterally along the track
the first electrode maintains electrical contact with the needle
shaft adjacent the hub.
5. Apparatus as set forth in claim 4 in which the hub is an electrical
conductor and grasps the needle shaft in electrical contact therewith,
said slide track being positioned to maintain the first electrode
in lateral contact with the hub to establish the said electrical
contact with the needle shaft in the interior of the hub.
6. Apparatus as set forth in claim 1 including wiper barrier means
to be engaged by the innermost end of the needle at the completion
of the destroying cycle.
7. Apparatus as set forth in claim 6 said wiper barrier means being
part of the second electrode.
8. Apparatus as set forth in claim 7 adopted for use with needle
assemblies in which the hub is metallic, said wiper barrier means
being adapted to engage the needle shaft at its point of entry into
the hub, said first electrode means being adapted to engage the
metallic hub above the point of emergence of the needle shaft.
9. Apparatus as set forth in claim 7 adapted for use with needle
assemblies in which the hub is non-metallic, said first electrode
being adapted to engage the needle shaft adjacent the point of entry
into the hub, said second electrode at its most proximate point
to the first electrode being spaced therefrom a predetermined distance
to define a needle shaft stub at the conclusion of the electrical
resistance heating cycle which has a corresponding predetermined
length, whereby the needle stub is heated to incandescence, and
means closely adjacent the electrodes to engage and destroy the
needle stub.
10. Apparatus as set forth in claim 9 said means to destroy the
needle stub comprising stub deforming barrier means closely adjacent
the second electrodes to be engaged by the heated needle stub to
bend and deform the stub.
11. Apparatus as set forth in claim 4 said housing including a
removable expendable inner container to receive destroyed needle
parts, at least one of said electrodes being mounted in the inner
container.
12. Apparatus as set forth in claim 11 both of said electrodes
being mounted in the container and separable electrical contact
means carried by the container and adapted to couple to a power
source in the housing to energize the electrodes.
13. Apparatus for destroying and sterilizing a double ended needle
supported by a body portion which engages the needle between its
ends,
first and second electrodes adapted to have a power source connected
thereacross and respectively adapted to engage the needle ends simultaneously
to establish a flow of current through the full length of the needle,
said electrodes being convergent to a point of close proximity
adjacent the point of support by the body portion, and
means to provide relative motion between the electrodes and needle
to bring the needle and its supporting body into close proximity
with the point of proximate convergence of the electrodes, whereby
the needle is destroyed from its ends inward.
14. Apparatus as set forth in claim 13 for use with hypodermic
syringes in which the needle assembly is detachable from the syringe,
including a support for said body portion of the needle assembly
for holding it while the syringe is detached from the needle assembly,
said support being movable to comply with relatative movement of
the electrodes.
15. Apparatus as set forth in claim 14 including a spring supporting
the movable support.
16. Apparatus as set forth in claim 15 including a spring to support
the second electrode for yielding movement.
17. A method for destroying and sterilizing used hypodermic needles
comprising the steps of causing an electrical current to flow through
substantially the full length of the needle shaft from hub to tip
in an amount sufficient to heat the needle shaft to incandescence
and partial destruction, and thereafter progressively passing current
through what remains of the needle shaft from the hub outward until
substantially the entire needle shaft is reduced to sterilized bits
to a point adjacent the hub.
18. The method according to claim 17 including the step of mechanically
detaching any stub portion of the needle shaft remaining at the
hub by lateral engagement with an abutment while the stub is in
its heated state.
19. The method according to claim 18 including the step of mechanically
deforming any stub portion of the needle shaft remaining at the
hub while the stub is in its heated state.
Syringe needle description
This invention relates to hypodermic syringe needle destroying
devices and methods and more particularly to those utilizing electrical
resistance heating at the point of use to incinerate and sterilize
used needle parts prior to disposal through conventional waste channels.
BACKGROUND OF THE INVENTION AND PRIOR ART
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. 4628169
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.
SUMMARY OF THE INVENTION
The present invention overcomes the several disadvantages found
in the prior art designs by providing electrical resistance, point-of-use
needle incinerators having unique electrode configurations and associated
parts which accommodate a wide range of needle lengths, provide
time constants for complete sterilization, positively preclude exposed
needle stubs, and which in a variety of species can disinfect needle
parts in shielded or recessed portions of disposable or single use
syringe bodies.
In a broader concept of the invention two electrodes are provided
which are convergent, either geometrically or by virtue of their
ability to be relatively moved during the incinerating process from
maximum spacing to minimum while the needle remains in its syringe
mounting so that the syringe body with its needle can be moved as
one as the electrodes converge to destroy successively all parts
of the needle shaft and in the process afford time for the generation
and conduction of heat back into the syringe body by maintaining
electrical contact at the base of needle during the entire cycle.
In an embodiment particularly useful with dental syringes in which
the needle hub where gripped by the syringe body is metallic and
in which the needle is double ended, one electrode comprises an
elongated track which is continuously engaged in sliding contact
with the hub to conduct electricity into the needle at the point
of entry into the syringe body over the full incinerating cycle
during which the electrical circuit can open and close randomly
as parts of the needle shaft burn away. The other electrode comprises
a conducting ramp convergent toward the first electrode track so
that the needle is first heated over its entire length and as the
syringe is moved laterally to continuously close the circuit burned
open by the ongoing incinerating process, all portions are destroyed
back to a point adjacent the hub and sterilized even further. An
abutment is provided, which if desired can be part of the second
electrode itself, over which the incandescent and momentarily softened
stub end of the needle is drawn to detach it from the hub. The needle
residue is collected in a disposable container below, such residue,
however, being sterile and therefore non-hazardous. In embodiments
of the invention adapted for use with syringes in which there is
no metallic hub carrying the needle, which is typical of those used
in the medical profession, the needle stub can be rendered harmless
by bending it in its heated malleable condition at the instant it
is released from the electrode coupling to fold it back into the
then softened thermo-plastic tip of the syringe body. For situations
in which a second needle tip is disposed within the syringe body
such as double ended needles frequently used in the dental profession,
the convergent electrodes can take the form of a pair of relatively
movable electrodes preferably spring loaded and having a geometry
enabling them to enter confined areas. The normal preactivation
positioning of the electrodes should be such in accordance with
the invention that they are spaced apart by the maximum needle length
intended to be incinerated. As in the case of the fixed, convergent
electrode embodiments, the electrodes converge under movement of
the syringe to successively destroy the needle from its tip inwardly
toward the hub to reestablish the circuit as it is randomly burned
open.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view in perspective of a needle destroying apparatus
showing the basic housing part and removed therefrom a disposable
and sealable container for sterilized nonhazardous needle ashes
and bits, above which is shown a permanent, final cover portion;
FIG. 2 is a view in vertical section taken on the line 2--2 of
FIG. 1 looking in the direction of the arrows and showing the disposable
container open and in place within the housing;
FIG. 3 is a view in vertical section corresponding to the right
hand portion of FIG. 2 and as viewed along the line 3--3 of FIG.
5 and showing in progressive steps the position of a hypodermic
syringe body and needle in the process of destruction and sterilization;
FIG. 4 is a view in transverse section taken on the line 4--4 of
FIG. 3 looking in the direction of the arrows;
FIG. 5 is a top view of the apparatus shown in FIGS. 1 and 2;
FIG. 5a is a fragmentary view showing the upper electrode removed
from the apparatus and in its closed position prior to receiving
the needle;
FIG. 6 is a view corresponding to FIG. 5 and as viewed along the
line 6--6 of FIG. 7 showing another embodiment of the invention;
FIG. 7 is a top view of the apparatus of FIG. 6;
FIG. 8 is a top view with the cover removed of another embodiment
of the invention;
FIGS. 8A, 8B and 8C are views in vertical section taken along the
line 8--8 of FIG. 8 showing needle destruction in successive stages
of operation; and
FIG. 9 is a view in vertical section of another embodiment of the
invention .
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIGS. 1-5 an embodiment of the invention is disclosed
which is particularly adapted for destroying and sterilizing parts
of a used hypodermic syringe S having a hollow needle N attached
to a syringe body B (which can be of the autoclavable reusable type
or, as is becoming more common, is discarded after a single use).
The illustrated syringe needle is a type used in the dental profession;
it is double-ended and carried between its ends N-1 and N-2 by a
metal hub H gripped by the forward end of the syringe body either
in a detachable coupling as when the syringe body is sterilizable
for reuse, or permanently molded into an expendable syringe body
to be discarded as a unit after one use.
The needle destroying and sterilizing apparatus includes a housing
20 adapted to be self-powered or connected to conventional electrical
service mains (not shown) and preferably positioned near the point
of use of the syringe by the professional operator. The housing
20 is formed with a deep slot 21 bounded by depending side walls
21a and 21b. The surface of the housing is formed with a slide track
22 defined by lateral guide ribs 22a and 22b to receive the forward
end of the syringe body or barrel B and to position the needle N
correctly within the housing for carrying out the incinerating process.
The housing can include a viewing window with appropriate light
filtration to allow monitoring of the incinerating process or alternatively
the entire housing can be formed of a semi-transparent material
such as smoked plastic.
The housing 20 contains a high current, low voltage power source
23 which can take the form of a rechargeable battery capable of
delivering approximately 3 to 6 volts (across the load when the
impedance is relatively high) served by a low voltage DC battery
charging source through a power cord 24. If desired the power source
in the incinerating unit can include its own battery charging circuitry,
in which case it can be powered through the cord 24 directly from
the AC mains. Alternatively the power source can be a step-down
transformer, the primary winding of which is connected to the AC
mains by the power cord 24. The DC source or the transformer secondary
winding, the latter preferably developing an AC output not greater
than 12 volts, is connected across the two electrodes of an electrode
array (described below in several embodiments) through a fuse 25
which is preferably a bimetallic, automatic reset fuse via upper
and lower contacts 25a and 25b disposed in the housing 20. Currents
ranging from 9 to 25 amperes are adequate in most cases to incinerate
hollow hypodermic needles of conventional size ranging in size from
18 to 30 gage. The electrode array which engages the needle shafts
can be designed for periodic replacement and thus can be incorporated
in a disposable box 27 which slides like a drawer in and out of
the housing 20. It will be understood, however, one or both of the
electrodes can be made a permanent part of the housing 20 or they
can be removed from the used box and mounted in a replacement box.
When the expendable box 27 is ultimately removed from the housing
for disposal with its spent electrodes and a volume of incinerated,
sterile needle ash and discrete bits, it can be sealed in accordance
with the invention by the cover 31 taken from its duplicate replacement
box by reversing the cover lengthwise to bring its interior locking
cleats 31a into register with locking cleats 27a on the outside
of the box 27. The expendable box 27 is then able to be thrown into
conventional channels of waste disposal, free of hazardous contamination.
With the incinerating box in place in the housing and locked in
position by a latch 29 with its top removed, the electrode array
is centered under the slot 21 and upper and lower electrode contacts
30a and 30b are in engagement with the contacts 26a and 26b, respectively,
to energize the electrodes. An on-off switch and pilot light are
not illustrated in the drawing but can be provided, if needed.
The disposable incinerating box 27 in the illustrated embodiment
incorporates the electrode array as renewable elements subject to
wear and designed to be discarded after use for, say, one thousand
incinerations. The upper electrode 32 forms a track adapted to engage
the metallic hub H of the syringe and to conduct electricity to
the needle at points closely adjacent the inner end of the needle
where it enters the syringe body. The upper electrode as best seen
in FIG. 5A can take the form of a number 10 springy wire of electrically
conducting material such as copper or aluminum having two elongated
parallel arms 33a and 33b normally spring biased together by the
action of the circular head 34 which defines an enlarged opening
to receive needle N at the entry point at the left hand end of the
track as viewed in FIG. 2. The conducting arms 33a and 33b rest
in groves 35 and 36 formed in the upper surface of the incinerating
box, with the free ends of the arms being splayed outward to center
the paired arms directly above the narrow elongated grove 37 in
the upper surface of the box. The upper electrode 32 is secured
in place by means of a mounting screw 38 which clamps a narrow extension
loop 39 to the box body and also secures contact spring 30a which
engages the transformer contact 26a.
The electrode array is completed by complementary second electrode
40 which is a metallic conducting plate electrically coupled by
the contact 30b to the lower contact 26b. The lower electrode 40
is supported in upwardly convergent relationship with the upper
electrode 32. The upper end 41 of the electrode 40 defines a wiping
barrier with its uppermost sharp corner which is spaced from the
upper electrode 32 by a distance corresponding to the amount by
which the hub A extends downward through the upper electrode arms
33a and 33b when the head of the syringe body B is in sliding engagement
with the track 22 as best seen in FIGS. 3 and 4. If desired the
barrier section 41 can be made more pronounced by forming it at
a steeper angle as illustrated by the barrier 41' of FIGS. 6 and
7.
The spacing between the electrodes at the left hand end of the
incineration chamber exceeds the length of the longest needle to
be accommodated by the unit. As best seen in FIG. 3 with the end
of the syringe body B seated on the slide track 22 the needle hub
H, when the syringe is moved from the enlarged electrode opening
38 will be engaged laterally by the spring loaded electrode arms
33a and 33b which will be forced apart in their support grooves
35 and 36. When the depending end of the needle N reaches the upwardly
convergent electrode 40 current will flow through the needle body
from hub to tip, quickly achieving incandescence. The needle will
typically burn through at a point between its ends where the cooling
effect of the electrodes is least felt, with maximum cooling typically
occurring near the hub end due to the relatively large metal masses
of the twin electrode arms. The ability of the heated needle to
bend will increase the time before the break, if any, occurs to
open the circuit, after which further sliding movement of the syringe
will quickly reestablish the circuit to resume the heating cycle.
By the time the needle reaches the barrier 41 the upper or hub end
of the needle will have been heated and reheated over a relatively
long time cycle of say 2 to 3 seconds causing heat to be conducted
upward into the syringe body to convey sterilizing temperatures
into the syringe body beyond the electrode coupling point. Any liquids
within the needle will be heated to sterilizing temperatures and
driven in a superheated state upward into the syringe barrel.
When the remaining needle stub, heated to incandescence and therefore
malleable, engages the barrier 41 it will be detached from the hub
H by the wiping action of the hub over the lip of the barrier and
will establish a fleeting direct electrical coupling between the
hub H and the electrode, generating additional heat. If necessary
the hub can be wiped back and forth over the barrier 41 to detach
the stub. The physical wiping action will also serve to clear the
barrier area of residue. After passing the barrier 41 the syringe
body, free of its sharp stub is lifted from the unit. If the syringe
is capable of being reused the hub H and internal needle part N-2
can be detached therefrom and further incinerated by the species
of the invention described below having reference to FIGS. 8 8A,
B, and C.
Referring to FIGS. 6 and 7 there is illustrated a point-of-use
needle incinerating device which is specifically designed to accommodate
a type of hypodermic syringe S' widely used in the medical profession
in which the hollow needle N' is carried by hub H' formed of plastic
and supported by the syringe body B, all of which are intended to
be destroyed after a single use. The needle N' is in most cases
single ended and is molded directly into the plastic hub H' (without
an interposed metallic hub part such as the hub H in FIGS. 1-5A).
The housing and basic electrode parts are substantially identical
to those described above having references to FIGS. 1-5A and are
identified by like reference numerals with the upper electrode 32
having elongated arms 33a and 33b adapted to be spread apart against
the inherent spring action of the head 34 by the thickness of the
shaft of the needle N' (as opposed to the greater thickness of the
metallic hub H in FIGS. 1-5A). The lower electrode 40 is convergent
upwardly toward the upper electrode 32 and can terminate in barrier
41 which is spaced from the upper electrode by a distance which
precludes unintended permanent short circuiting by bits of the burned
needle becoming fused therebetween. The spacing also defines the
length of the needle stub.
Immediately beyond the electrically conducting barrier 41 in the
direction of travel of the syringe the housing is formed with an
upwardly inclined barrier 42 to a peak 43 followed by a deforming
trough 44 of approximately the same width and contour as the lower
end of the syringe hub H'.
In operation the Syringe S' is inserted at the left hand end of
the track with the needle N' pointing down, until the lower shoulder
of the syringe body B' engages the slide track 22. The syringe is
then slid to the right as viewed in FIG. 6 until the tip of the
needle engages the lower electrode 40 and the shaft of the needle
is engaged by the electrode arms 33a and 33b close to the lower
end of the hub H'. The electrical circuit is thus completed to heat
the entire needle shaft to incandescence and destruction. Thus heated
it first bends to enlarge its contact area with the lower electrode
and in some cases breaks off as a fully sterilized but deformed
section. Meantime the syringe is moving in its track to maintain
continuous heating of the needle from the hub downward by electrical
resistance heating and from the hub upward into the body of the
syringe by conduction. In the process any contained liquids will
become vaporized and sterilized. The process continues over a finite
time interval of 2 to 3 seconds until all portions of the needle
shaft below the level of the top of the electrode barrier 41 are
destroyed. A heated shaft stub having a length corresponding to
the spacing between the electrode 32 and the top of the barrier
41 remains and is on the order of 2 mm. Immediately, the red hot
stub engages the inclined barrier 42 and begins a bending-over process
which reaches 90 degrees as the stub passes over the peak section
43 after which it drops into the contoured trough 44 which peens
it over. Under the impact with the base of the trough it is pressed
into the now softened thermoplastic hub H' to render it harmless
as well as sterile. The syringe body which remains can be disposed
of by conventional waste disposal means without requiring the use
of either hazardous or sharp protection containers. Needle residue,
sterile and harmless, is collected in the disposable box 27 which
in time due to filling as well as wear of the electrodes will be
sealed by a cover 31 as described above and discarded.
If desired the deforming process for the needle stub can take the
form of a shearing device or cut off wheel positioned to act on
the stub in its heated condition at the instant it leaves the electrodes.
Referring to FIGS. 8 8A, B and C there is illustrated another
embodiment of the invention which is adapted to dispose of a double
ended hypodermic needle assembly S-2 including an external sharpened
portion N-1 (shown in phantom lines and having previously burned
away) and an internal sharpened portion N-2 carried by the central
metallic hub H-2 attached to the plastic carrier body B-2. The needle
incinerator includes base 47 supporting a disposable outer container
48 having a detachable cover portion 49 within which the permanent
electrode array 50 is removably mounted. The electrode array 50
includes a three legged base portion 51 having a pedestal 52 extending
upwardly therefrom formed of electrically insulating material and
carrying at its upper end cup shaped first electrode 53 connected
to one terminal 54a (shown schematically) of a low voltage source
(not shown) in the base 47.
The second electrode assembly 55 is adapted to be convergent toward
the first electrode 53 by virtue of its ability to be moved axially
downward on the pedestal 52 against a compression spring 56 connected
at its lower end to a second terminal 54b (also shown schematically)
of the low voltage power source. The second electrode assembly 55
comprises a metal cage having four lateral arms 55a, b, c and d
attached at their lower ends to a collar 57 surrounding the pedestal
52 and attached to the upper end of the compression spring 56. The
cage arms carry an electrode disc 58 having a central contoured
electrode ring 59 adapted to be engaged by the metal hub H-2 of
the needle assembly. A conical plastic shield 60 and a cylindrical
skirt 60' carried by the arms 55a, b, c and d shields the interior
of the container 48 at the radial space between the inner wall 49a
of the cover 49 and the electrode arms 58.
With the needle carrier body B-2 fitted over the upper cage arms
and the electrode disc 58 with the needle N-2 entering the ring
59 it will come to rest with the pointed end of the needle pointed
toward the inner electrode 53 and the metallic hub H-2 resting on
the upper electrode 59 to establish electrical contact therewith.
The carrier body B-2 is then pushed downwardly causing the inner
tip of the needle N-2 to engage the inner electrode 53 to establish
a flow of current through the needle portion N-2 which will incinerate
the needle in the manner described above as the electrodes converge.
Suitable stops are provided so that the electrodes 53 and 59 remain
out of contact at the extreme end of the incinerating motion as
shown in FIG. 8C. The remaining carrier body B-2 can then be removed
and discarded. It will be understood that the exposed needle portion
N-1 has been previously incinerated by following the same procedure
with the needle carrier body reversed. Any needle stubs remaining
at the end of the incinerating process can be sheared off by moving
the carrier laterally causing the ring electrode 59 to function
as a barrier similar to the action of the barriers 41 and 41' described
above to shear off the red hot stub. Also, it will be seen that
the relatively movable electrodes 53 and 59 in action are convergent
and duplicate the functions of the fixed convergent electrodes 31
and 40 of the species of the invention described above having references
to FIGS. 1-5A and FIGS. 6 and 7. In all cases the needle is heated
throughout the entire cycle from the hub outward to the needle tip
allowing time for heat to be conducted to interior parts not spanned
by the electrodes and assuring complete heating of all needle shaft
parts. Also, the embodiment of the invention shown in FIGS. 8 and
8A, B and C can be used to incinerate the medical needle designs
of the type shown in FIGS. 6 and 7.
When the needle parts are incinerated, the ash and pieces of sterilized
needle shaft will drop through the cage arms supporting the upper
electrode into the cavity within the container 48 surrounding the
pedestal 52 and spring 56. After a plurality of incinerations the
container 48 can be replaced with a fresh container, capped and
discarded after removing the electrode array 50 which is adapted
to be installed in the replacement container. Separable electrical
contacts (not shown) can be provided for this purpose. Alternatively,
the container 48 can be emptied into a non-hazardous waste disposal
container and reassembled with the electrode array.
It will be understood that the apparatus of FIGS. 8A-C can be reversed
in its mechanical action so that the lower electrode 53 is moved
upward toward the upper electrode 59 either by lever action or cocked
spring action completed, if desired, by speed control means to establish
a relatively slow rate of travel. In such arrangement the syringe
body is simply manually held or clamped at the lid with the upper
electrode 59 in engagement with the hub H-2 with the lower electrode
53 being supported by a vertically movable carrier to establish
convergent electrodes to destroy the needle shaft from the tip inward.
As in all embodiments, electrode contact adjacent the hub is continuous
throughout the cycle.
Referring to FIG. 9 there is illustrated another embodiment of
the invention which adapted to destroy double-ended needle assemblies
S-2 of the type frequently used by the dental profession. A base
61 including a power supply supports a detachable container 62 having
a removable cover 63. The cover carries an upper electrode 64 on
a support 65 and the container carries the complementary convergent
lower electrode 66 on a yielding spring arm 67 connected to an electrical
contact 68 (shown schematically) which couples to the power source
in the base 61. The upper electrode is energized from an electrical
contact 69 through a conductor 70 spring finger contact 71 and
conductors 72 and 73. The conductor 72 is bare and seated within
a groove 74 in which the spring finger contact 71 rides in sliding
contact with the conductor. If desired, the conductor 72 can be
covered by an insulator 75 at the upper end of the groove to break
the electrical circuit when the cover is lowered to the point of
complete needle incineration to open the circuit.
A floating carrier assembly 76 having an inner annulus 77 and an
outer annulus 78 joined by radial spokes 79 rides on a light compression
spring 80 seated on an abutment 81 and secured against rotation
by a vertical rib 82 on the inner wall of the container received
in a slot 83 in the outer edge of the annulus 78. The inner annulus
77 is a seat for holding the base B-2 of the needle assembly, which
is identical to that described above having reference to FIG. 8A.
The body B-2 rests on radially yieldable fingers or alternatively
on a yieldable 0-ring 84 and is constrained against rotation by
elements 85 which engage the upper side of the body B-2.
Attached to the annulus 78 of the floating carrier 76 is a transparent
sleeve 86 forming a finger gripping surface for stabilizing the
floating support 76 when the needle assembly S-2 is mounted therein.
If desired, an optional upper coil spring 87 can be secured to underside
of the cover 63 to rest releasably on the upper edge of the sleeve
86 to apply balancing forces against the lower coil spring when
the cover 63 is lowered, as described below. This force balance
relieves the needle part N-2 of most of the bearing load necessary
to lower the support 76 and the needle assembly carried thereby
into rubbing engagement with the lower electrode 66.
Also, by appropriate selection of springs 80 and 87 the system
can be tuned so that the upper and lower electrodes both converge
toward the upper and lower ends of the hub at the same time, provided
however that the upper spring is stronger than the lower. If for
example, needle part N-1 is twice as long as N-2 a spring strength
ratio of 2 to 1 favoring the upper will bring the two electrodes
to the hub H-2 at the same time. Omitting the upper spring will
bring the upper electrode to the hub before substantial movement
of the needle assembly occurs, thus delaying complete incineration
of the lower needle part and removal of its stub, if any by the
barrier 66a.
In operation, when the dentist has finished with the hypodermic
injection of a patient, with the cover 63 removed the syringe barrel
(not shown) with its detachable needle assembly S-2 is placed vertically
into the annulus 77 and the syringe barrel unscrewed from the expendable
needle assembly. With the syringe barrel removed, the cover 63 is
placed on the container and slowly lowered to bring the upper electrode
64 into contact with the upper needle part N-2 and the lower needle
part N-1 into contact with the lower electrode 66. The floating
support 76 then moves downward as necessary to establish the current
flow through the needle through wiping action on the inclined electrode
surfaces.
The needle will immediately be heated to incandescence and will
sterilize and destroy itself as the cover is slowly lowered to cause
the electrodes 64 and 66 to coverage to points of close proximity
to the top and bottom of the hub H-2. This point can be signalled
by a releasable detent (not shown). Further smart pressure on the
cover 63 will drive the body portion B-2 downward through the yieldable
means 84 and in the process will force the lower electrode downward
on its spring arm 67 until the body falls into the repository below.
Any stub remaining from the needle part N-1 will be broken away
by the barrier 66a on the edge of the electrode 66. The momentary
dead short across the electrodes by the metal hub H-2 can, if necessary,
be overcome either by the circuit breaker or by the insulator 75.
As the hub H-2 snaps over the barrier lip 66a on the electrode 67
any stub remaining from the needle N-1 will be removed. It will
be understood that the lower end of the container 62 (shown foreshortened
in the drawing) is subject to many design variations including,
if desired, a removable drawer configuration similar to the drawer
27 in FIG. 1.
While the invention has been illustrated as applied to embodiments
found in the field of dental hypodermic syringes it will be understood
that the principles of the invention can be adapted to other syringe
needle structures having exposed or imperfectly concealed needle
portions. Also, additional shielding against the escape of sparks
from the relatively small openings can be provided by movable iris
vanes or by flexible filaments adapted to yield with the movement
of the syringes such shields preferably being disposable with the
collection boxes for destroyed needle parts. It will also be understood
that dampers can be included to control the rate of syringe motion
under hand power or mechanical drives can be used to replace the
hand driven motion of the syringe bodies to provide for precision
timing of the incineration process. Also, while the lower electrode
40 is shown as being upwardly convergent toward the upper electrode
32 the upper electrode can be contacted downwardly and mounted
in a sloping wall part of the housing. The invention should not
therefore be regarded as limited except as defined in the following
claims. |