Note: Descriptions are shown in the official language in which they were submitted.
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SYRINGE
Field of the invention
The present invention relates to a syringe, and more particularly, to one that
is
able to perform some functions automatically, for instance a self filling
function andlor an
automatic retraction of the needle.
Backs rai and
There has been an increased awareness concerning the potential for
transmission of diseases such as acquired immure deficiency syndrome (AIDS) by
way
of accidental needle sticks from contaminated used needles or through the
sharing of
used needles by drug-users.
Healthcare workers came into contact with spent needles possibly hundreds of
times, daily throughout the course of their work. There have been a lot of
efforts in
hospitals to educate hospital personnel to take every possible precaution to
prevent needle
stick injuries and to take appropriate medical treatment after a needle stick.
However, a
more fundamental solution to prevent such accidental injuries is to develop a
new syringe
with improved features, which eliminate the operation Procedures mostly
responsible for
such injuries. Furthem~ore, the Needlestick Safety and Prevention Act in the
USA requires
all healthcare a~orkets to use safety syringes to prevent accidental needle
stick injuries.
Therefore, most hospitals and clinics in the USA prefer to use automatically
retractable
~5 safety syringes, which retract the needle into the body of the syringe
after use and can be
used one-handed. These are more convenient and safer than the two-handed
manual
retractable syringes.
A number of difFerent devices have been proposed far disabling a syringe
aridlor
needle in order to minimise the risk of contamination from a used syringe.
In general, a typical syringe comprises a hollow syringe body with a needle
mounted at one end of the body. A plunger with a #piston at one end is
slidably mounted
into the syringe body such that the end of the plunger can be depressed into
and
withdrawn from the hollow body of the syringe.
1
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These are numerous devices for preventing a needle from coming in contact with
human skin. These devices generally fall into twa categories.
The first of the two categories invalves sheathing a needle with an extra
plastic tube.
This tube is slidable axially along the outside of the syringe body and can be
locked in the
desired position to prevent the sharp end of the needle from sticking whoever
is using or
disposing of the syringe.
The second category relates to a syringe having a device for retracting the
needle
into a syringe barrel after use, in order to eliminate the need for recapping
the needle after
the syringe is used.
US Patent No. 5,344,403, issued to Rahnfong Lee on 6 September 1994, relates
to a retractable safety syringe comprising a hollow body, a plunger and a
needle carrier.
A hub attached to an end of the plunger engages the needle carrier when the
plunger is
depressed, so that the needle carrier is retracted into the hollow body of the
syringe
along with the needle when the plunger is withdrawn. A sharp notch at the rear
of the
barrel catches the hub as the plunger is withdrawn, to allow the plunger shaft
to be
broken off. After the plunger shaft is broken off, the needle will remain
trapped within the
syringe.
International Patent Application Publication No. WO A-01!64,272, published on
7
September 2091 in the name of Teng Jun Piao, relates to a syringe having a
retractable
needle. The needle is mounted onto a needle carrier. The end of the syringe
plunger
~5 engages the needle carrier when it is fully depressed into the barrel of
the syringe. As
the plunger is withdrawn, it withdraws the needle carrier into the barrel of
the syringe at
an angle. This prevents the needle being pushed back gut again. instead it
catches on
a protruding surface and is deformed to be of no use. In addition, the plunger
includes a
fragile portion that .causes a portion of the plunger to break when the
plunger is
withdrawn. Thus, the syringe cannot be re-used.
H.o~re~res, for such syringes, the withdrawal of the needle into the barrel of
the
syringe is entirety manual and reduires a user to remember to make some
deliberate
movement to withdraw the needle into the syringe.
2
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A variation of this theme is to enable the needle to be retracted
automatically into
the barrel of the syringe.
US Patent No. 4,966,593, issued to James J, hennox on 30 October 1990,
~ relates to a single-use syringe having a needle which is automatically
retracted within the
barrel of the syringe after use. A release mechanism incorporating a spring is
used to
cause the needle to be retracted wholly into the barrel. However, a user is
required to
give an extra push to the plunger after administering the injection in order
for the release
mechanism to be actuated.
1 CI
International Patent Application Publication No. WO-A-98/58,694, published on
3d
December 1998 #n the name of Teng Jun Piao, relates to a single-use syringe
using two
springs that are attached to an end of the syringe and to a plunger to induce
automafiic
withdrawal of the needle into the barrel of the syringe. The springs are in an
extended
15 state when the plunger is depressed. At this position the plunger engages
the needle
carrier holding the needle. When the plunger is released, the springs return
to their
neutral, non-extended state. This reverse spring force causes the plunger to
be withdrawn
automatically. As a consequence the needle carrier holding the needle is also
retracted
into the barrel. Further, a portion of the plunger can be easily broken off
after use to
20 prevent the syringe from being re-used by someone else.
However, the syringes described in the above-mentioned documents are either
too
complicated in their construction, or have too many precision components,
which increase
the overall cost of the syringe. An economic automatic retractable and non-
reusable
25 syringe is urgently required in the market.
Summary of the Invention
According to an aspect of the invention, there is provided a syringe
comprising: a
30 body, a plunger, a first sealing member and a second sealing member. The
body has a
first end for mounting a needle, a second end, and an internal bore extending
from the
first end to the second end. The plunger has a first end mounted slidably
within the bore
of the body, with a second end of the plunger extending out of the second end
of the
body. The first sealing member is on the plunger, extending into sliding
sealing
35 engagement with the bore. The second seeling member seals against the body,
positioned between the farst sealing member and the second end of the body,
and
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extending into sliding sealing engagement with the plunger. The first and
second sealing
members, the body and the plunger are arranged such that depressing the
plunger
within the bore, towards the first end of the body, generates a vacuum between
the first
and second seat members.
According to another aspect of the invention, there is provided a plunger for
a
syringe, camprising: a shaft portion, a first sealing member, a pushing
portion and a
second sealing member. The shaft portion has a first external diameter. The
first
sealing remember is fixedly mounted on a first end of said shaft portion, the
first sealing
member having a second external diameter larger than the first external
diameter. The
pushing portion is fixedly mounted on a second end of said shaft portion, the
pushing
portion having a third external diameter larger than the second external
diameter. The
second sealing member slidably mounted on said shaft portion, the second
sealing
member having a fourth external diameter substantially the same as the second
external
95 diameter.
According to another aspect of the invention, there is provided a method of
using
a syringe, composing depressing a syringe plunger into a syringe body. The
syringe
plunger carries a first seal member which slidably seals against the syringe
body. The
~0 syringe plunger sealably slides against ~ second sea! member. Depressing
the syringe
plunger into the syringe body moves the first and second seat members apart.
Moving
the first and second seal members apart generates a vacuum between the first
and
second seal members.
25 Brief Description of the i~lrawings
The invention wilt now be further described by way of non-limiting example,
with
reference to the accompanying drawings, in which:,
30 Figure 1 shows an exploded view of a syringe in accordance with a preferred
embodiment of the invention;
Figure ~a shows a sectional view A-A of the body portion of the syringe in
Figure
1;
Figure ~b shows a sectional view B-B of the plunger portion of the syringe in
35 Figure 1;
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Figure 3 is a flowchart showing the sequence of steps used in the operation of
the syringe of Figure 1;
Figure 4 shows the syringe of Figure 1 with the plunger fully retracted;
Figure 5 shows the syringe of Figure 1 at the end of an insertion stroke, just
before a fluid is withdrawn into the syringe;
Figure 6 shows the syringe of Figure 1 in a condition in which fluid has been
drawn into the syringe body;
Figure 7 shows the syringe of Figure 1 with the plunger fully depressed into
the
syringe body and the .needle carrier engaging with the piston, at the end of
an injection
stroke;
Figure 8 shows the syringe of Figure 1 with the needle fully retracted into
the
syringe body; and
Figure 9 shows the syringe of Figure 1 with a portion of the plunger broken
off.
Detailed Description
Figures 1 to 0 relate to a syringe according to an embodiment of the
invention.
Tho syringe has a hollow body 10 with an internal bore, a plunger 20 slidably
mounted in
the body and a needle 44 mounted at a first end of the body. A first sealing
member 30,
at a first end of the pl~tnge~ 20 and within the body, slidably .seals against
the body. A
second seating member 60 seals against the body and sli~ably seals against the
plunger
shaft 22, the second sealing member being positioned between the first sealing
member
and a second, opposing end of the body (although it does itself extend to that
second
end). Pushing the plunger 20 into the body 10 creates a vacuum between the
first and
25 second sealing members 30, 60. This can be used to draw liquid into the
syringe for
infection. Alternatively, the vacuum can be used to retract the needle ~4
automatically
into the body, if the plunger 20 is first pushed in a sufficient amount, A
portion of the
plunger 20 is easily broken off after use to ensure that the syringe cannot be
re-used.
30 Figure 1 shows an exploded view of a syringe of an embodiment of the
present
invention. Figures 2A and 2B show sectional views along the lines A+A and B-B,
respectively, of the syringe in Figure 1 with various parts assembled.
The syringe is made up of two main components, a body 10 and a plunger 20.
The syringe body 10 is hollow, with an internal bore and generally elongate
and
cylindrical in shape. The syringe body 10 has a neck 13 at a first, distal end
with the
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external diameter of the neck being smaller than that of the barrel of the
body 10 and the
internal diameter of the neck being smaller than that of the main bore of the
body 10.
The plunger 20 is .stidably mounted within the yringe body 10 through a hole
in the
second, proximal end of the syringe body 10.
An annular finger flange 11 is provided at the proximal end of the syringe
body
10. The finger filange 11 extends outwards from an external surface of the
syringe body
10, to provide a support surface for a user's fingers when using the syringe.
A shallow
annular stop flange 1~ projects inwardly into the hOllOw inside the syringe
body 10 from
an internal surface, near the proximal end of the syringe body 10.
An annular luer 50 is mounted internally on the neck portion 13 of the syringe
body 10. The luer 50 is hollow and generally cylindrical in shape and has a
hollow
tapered nozzle 55 and an outer wail portion 58. An annular cavity 54 is
defined between
an inner surface of the outer wall portion 58 and an external surface of the
nozzle 55.
The tuer 50 is mounted within the .neck 13 of the syringe body 10 by means of
annular lip
members 5~, 53 that are axially spaced on an external surface of the outerwalt
portion
58. The lip members 52, .53 engage with corresponding notches 131 on an
internal
surface of the neck 13. A tapered annular supporting lip 51, extending
outwards at the
~0 proximal end of the tuer 50, .engages with the internal surface of the
syringe body 10 at a
tapered section 15 between the neck 13 and the main hollow barrel portion of
the syringe
body 10. The annular lip members 52, 53 and the supporting tip 51 serve to
hold the luer
50 within the neck 13 and also to prevent fluid from leaking out of the
syringe.
A needle 44 is mounted on a needle carrier 40 at the distal end of the syringe
body 10. The needle 44 is mounted on the needle carrier 40. The needle carrier
40 is
hollow and generally conical in shape. An external annular rib 41 extends from
the base
of the needle carrier 40. The needle carrier 40 is fitted into the annular
cavity 54 of the
tuer 50 to allow fluid communication befween the needle 44, the needle carrier
40 and
the syringe body 10. The needle carrier 40 is held in place by frictional
farce between
the inner surface of the outer wall portion 58 of the tuer 5p and the rib 41
of the needle
carrier 40 and between the inner surface of the needle carrier 40 and the
outer surface of
the nozzle 55. The luer 50 serves to hold securely the needle carrier 40 at
the distal end
of the syringe body 10 and to sea! the needle carrier 40 to the syringe body
10. With the
needle carrier 40 mounted on the leer 50, a recess 2S5 extends forwards of the
distal
end of the luer nozzle 55 to the inner surtace of the needle carrier 40.
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The needle carrier 40 and the lust 50 together form a needle holder for the
syringe.
The plunger 20 comprises a piston assembly 201, including a first sealing
member exemplified here as a gasket 30, a generally cylindrical shaft 22 and a
second
sealing member, exemplified here as a an annular seal 60 mounted on the shaft
22. A
flanged push-button 21 is provided at a proximal end of the shaft 22. The push-
button
21 serves as a support surface for the user to push on or pull on, to depress
or withdraw
the plunger 20. A pair of flat portions 242, arranged in a cross, extends in
the axial
direction from the distal end of the shaft 22 to the piston assembly 201, to
connect the
piston assembly 209 to the shaft 22.
A disc 25 of the piston assembly 201 is connected to only one of the pair of
flat
portions 242 and at only two points, to form a break portion 24. The break
portion 24. is
designed such that the shaft 22 can be easily dislodged from the piston
assembly 201
and thereby from the syringe after use. An engaging portion in the form of an
elongate
protrusion 261 having a pair of resilient members 262 at its distal end
extends forwards
from the disc 25. A tip gap 263 between the two resilient members 262 allows
the
resilient members 262 to be compressed together. The resilient members 262
have
defents 264 at their distal ends. The detents 264 have tapered front ends
extending
outwards in the rearward direction. The detents 264 extend rearwards a short
distance
before ending with a rearward facing laterally extending urface. A radial
flange 253
extends from the elongate protrusion 261, a short distance from the disc 25.
A gasket 30 is mounted over the elongate protrusion 261, which extends through
the centre of the gasket 30 and out through a gasket through-hole 33. The
gasket 30 is
mounted against the forward face of the disc 25. The gasket 30 is secured in
position by
means of an internal groove engaging with the radial flange 253 on the
proximal end of
the elongate protrusion 261. The gasket 30 is generalty cylindrical in shape
with a
tapering distal end and axially spaced extemai annular seals 31, 32. The
gasket 30, the
elongate protrusion 261 and the disc 25 together form the piston assembly 201.
The seal 60 is mounted on the shaft 22. The seal 60 is annular with a
cylindrical
outer surface of a slightly smatter diameter than the internal surface of the
proximal end
of the syringe body 10. A pair of axially spaced rib members 62, 63 extend
around the
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outside of the cylindrical cuter surface of the seal 60, to the same diameter
(or slightly
more) as the internal surface of the proximal end of the syringe body.
For ease cf assembly, the shaft 22 is made of two parts, a first portion 22A
and a
second portion 228. The seat fi0 is mounted over the proximal end of the
second portion
22B {as there are no protr~rsions for it to fit over?. After the seal 60 is
mounted onto the
second portion 22B, the first portion 22A is attached onto the second portion
22B by
means of a locating boss 223, on the proximal end cf the second portion 228
securely
fitting into a corresponding hole in the distal end of the first portion 22A.
1D
A stop member 23 is mounted on the outside of the shaft 22, a first distance
forwards of the push-bu#ton 21. The first distance is about a fifth of the way
along the
length of the shaft 22. The distance between the detents 264 and the stop
member 23 is
slightly more than the distance between the tapered section 1~ of the syringe
body 90
and the rear surface of the finger flange 11 of the syringe body 10. The
slight extra
distance is to allow for the thickness cf the annular shoulder 61 cf the seal
60. The stop
member 23 is connected to the outer surface of the shaft 22 through a thin,
base portion
231, which allows it to be broken off readily easily_
The syringe body 10, the shaft 20, the disc 25 and the elongate protrusion 261
are made of relatively stiff plastics materials, such as thermoplastic
polypropylene. The
tuer 50, the gasket and the seal 60 are made of eiastomeric materials, such as
rubber.
However, the rubber material used for the leer 50 is usefully tae harder than
65 degrees
so that the needle carrier 40 can be mounted properly and not fall off when
the luer 50 is
mounted onto the neck 7 3.
The first, distal end of the plunger 20 is inserted into the second, proximal
end of
syringe body 10. The engaging portion is of a small enough diameter to pass
into the
syringe body 10 without contacting it. The elastomeric gasket 30 is able to
deform into
the proximal end of the syringe body 10, over the stop flange 12. The .disc 25
is stiffer
than the gasket, but its circumference is tapered towards the front, which
allows it to clip
over the stop flange 12.
The seal 60 is securely mounted onto the syringe body 10 at the proximal end
of
the syringe body 10. The front face of the annular shoulder of the seal 60
abuts the
rearward face of the finger flange 11 of the syringe body 10. When inserting
the plunger
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2D into the syringe body 10, the piston assembly 201 is initially kept as
close to the seal
60 as possible, With the disc 25 in contact with the seal 60. This reduces the
amount of
air initially between the seal 60 and the gasket 3D. The second, proximal end
of the
plunger 20 extends out beyond the second, proximal end of the syringe body 1
D.
The plunger 20 carrying the piston assembly 201 is slidably mounted within the
syringe body 1D, from the second, distal end of the syringe body 10. The
plunger 20
moves forwards or backwards within the hollow syringe body 10 when the plunger
20 is
pushed or withdrawn, respectively. The axially spaced external rib members 62,
63 of
the seal fi0 seal against the inner surface of the syringe body 10, at the
proximal end of
the syringe body 10. The further axially spaced internal rib members 64, 55 of
the seal
60 siidably seal against the outer surtace of the shaft 22.
The a~i~ally spaced external annular seals 31, 32 of the gasket 30 slidably
seal
against the inner surFace of the syringe body 10. The gasket 30 and sea! 60
provide
hermetic seals. liVhen the plunger 2D is pushed into the syringe body 1 D, the
movement
of the piston assembly 201 away from the seat 80 generates a vacuum in a
vacuum area
2D2B defined between the piston assembly 209 and the seal 60. It is possibly
not a true
vacuum, as there may already be some air between the seal BD and gasket 30 as
a
result of the assembly of the syringe.
C?peration of the syringe is now described in brief with reference to Figures
3 to 9.
Figure 3 is a flowchart showing the sequence of steps used in the operation.
Figures 4
to 9 are cross-sectional views of the syringe at various points during use.
Initially, at the start step, the syringe is as shown in Figure 4, with the
gasket 30
close to the seal 5D. In a first step 5102, the insertion step, the user
pushes the plunger
20 into the syringe body, creating a vacuum between the gasket 3D and the seal
60. At
the position shown in Figure 5, the user stops pushing at a first position,
step S1 D4,
when the stop member 23 abuts the seal 60. The user inserts the end of the
needle 44
into a bottle of medical fluid, step S1 D6, and releases the pressure on the
plunger, at
step S1D8. The plunger automatically retracts, under the reduced pressure
between the
gasket 30 and the seal ~D, at step S11D, to the position shown in Figure 6.
This action
draws medical liquid into the syringe through the needle 44 and fills the
hollow of the
syringe body.
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The syringe is now ready to give an injection and, at step 5112, the user tips
the
syringe needle uppermost and empties it of air and then inserts the needle
into the
patient. Then at step S114, the injection step, the user pushes the plunger in
again, to
inject the medical fluid into the patient. The stop member 23 is pushed to
abut the seal
60, and the pushing continues beyond that, at which point the stop member 23
breaks
off, step S114. The pushing stops at a second position, at step S116, when the
syringe
is empty and the engaging means between the plunger and the needle holder
engage.
!n this case the detents 234 extend into the recesses 235 between the leer
nozzle 55
and the needle carrier 40, as shown in Figure ?.
As before, pushing the plunger 20 into the syringe body 10 creates a vacuum
between the gasket 30 and the seal 60. This time, however, when the user
releases the
pressure on the plunger 20, at step S118, and the plunger automatically
retracts, at step
S120, it also retracts the needle holder, including the needle ~4, the needle
carrier 40
and the luer 50 with it, as shown in Figure 8.
once the needle 44 is fully retracted, the user is able to snap the shaft 22
off the
piston assembly 201, and he does this, at step S122, by bending the shaft 22
down, as
shown in Figures 9, thereby rendering the syringe unusable. The process then
ends.
The use of the syringe, in particular the drawing of the medical fluid and the
retraction of the needle are both easily achieved one handed and
automatica!!y.
More specific details of the various points during operation of the syringe
are
described below, again with reference to Figures 4 to 9.
Figure 4 shows a cross-section of the syringe when the plunger 20 is in a
fully
retracted state {or not yet depressed state. Some air is trapped in a trapped
air area
202A between the piston assembly 201 and the seal 60. The amount of air in the
trapped air area 202A is typically of a negligible volume compared to the
entire syringe
body 10.
In this fully retracted state, only the piston assembly 201 and a small
portion of
the shaft 20 are within the syringe body 10. The plunger 20 is prevented from
retracting
further when the disc 25 on the piston assembly 201 comes into contact with
the
inwardly projecting stop flange 12 near the proximal end of the syringe body
10.
to
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!n order to use the syringe, the plunger 20 is pushed into the syringe body 10
to
expel most of the air in the syringe body 10 out through the needle 44. This
is typically
referred to as an insertion stroke. The user is required to exert a manual
pushing force
to cause the plunger 20 to depress into the syringe body 10. The external
annular seals
31, 32 on the gasket 3fl of the piston assembly 2131 move in sliding contact
with the inner
surface of the syringe body 10.
As the piston assembly 201 maws away from the seal 60, a vacuum is
generated in the vacuum area 202B defined betvueen the piston assembly 2fl1
and the
seal 6D.
The insertion stroke continues until the position shown in Figure 5. The stop
member 23 limits how far into the syringe body the plunger 20 should initially
be inserted.
The plunger 20 is depressed into the syringe body 1 Q until the stop member 23
contacts
the annular shoulder .61 of the sea! 60, at the f rst position. This marks
where the piston
has been depressed as far as it is allowed for the user to draw medical fluid
into the
syringe. At this point, the resilient members 262 protruding from the distal
end of the
piston assembly 201 are compressed together to fit into the proximal end of
the leer
2fl nozzle 55. However, the resilient members 262 do not extend fully through
the nozzle
55 and thereby can still be withdrawn.
When the pushing force exerted by the user is removed, the plunger 20 is
automatically retracted due to the vacuum generated in the vacuum area 202B.
This is a
low pressure area compared with the pressure on the medical fluid. As the
plunger 20 is
retracted, the medical fluid is drawn into the syringe body 10 through the
needle 44, the
needle carrier 4fl and the lust 50 into an area between the needle carrier
4.fl and the
piston assembly 201. Depending on the amount of medical fluid required, the
user may
allow the plunger 20 to retract t~ its fully retracted state or intercept the
retraction of the
plunger 20 so as to get a desired more limited volume of medical fluid. Figure
6 shows a
cross-sectional view of the syringe in a state when the syringe is filled with
the medical
fluid. The syringe is now ready for the administration of an injection,
through an injection
stroke.
When the plunger 20 is pushed forward again into the syringe body 10 at the
beginning of an ejection stroke, the medical fluid is discharged from the
needle 44,
11
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normally into a patient. During the injection stroke, a vacuum is again
generated in the
vacuum area 202B in the syringe body 10.
Figure 7 shows a cross-sectional view of the syringe at the end of an
injection
stroke. The plunger 20 is inserted into the syringe body 10 beyond a i'irst,
stop position,
defined by the stop member 23 contacting the annular shoulder 61 ofi the sea!
60 (i.e. the
position at the end of the insertion sfiroke). The stop member 23 breaks off
from the
shaft 20 when the user continues to exert a pushing force on the plunger 20
beyond the
stop position. When the plunger 20 is inserted beyond the stop position, the
resilient
members 262 continue all the way through the lust nozzle 55 and extend out
through the
distal end of the lust nozzle 25. The resilient members are compressed when
they are
within the nozzle 55, however, once they emerge from the node due to the
pushing
force, the resilient members 262 revert back to a non-compressed state and the
detents
264 extend into the recess 265. if they are pulled rearwards, the detents 264
in the
recess 265 engage with the forward facing circumferential edge of the nozzle
55. Thus
the lust 5fl is connected to the plunger 20. Pushing stops at this second
position.
Figure 6 shows a cross-sectional view of the syringe when the needle is
refracted
into the syringe body. The vacuum generated in the vacuum area 202B during the
injection stroke causes the plunger 20 to retract automatically when the
pushing force
exerked by the user is removed, at the end ofi the injection stroke. Since the
lust 50 is
now connected to the plunger 20, the lust 50 together with the needle carrier
40 and
needle 44 is retracted into the syringe body 10 as the plunger 20 retracts.
The needle
carrier 40, together with the needle 44 is completely retained within the
syringe body 10.
No portion of the needle 44 is exposed for accidental contact. This
substantially
eliminates the problem of accidental needle sticks during disposal of the used
syringe.
After the needle 44 has been fully retracted into the syringe body 1 t1, the
shaft 20
is broken off at the break portion 24, as shown in Figure 9. This ensures that
the syringe
cannot be re-used by another person.
The automatic retraction of the needle 44 into the body 10 of the syringe by
means of a vacuum does not require the syringe user to remember to take an
extra step
to withdraw the needle into the syringe body or to shield the needle 44 with a
sheath or
the like. This greatly reduces, if not eliminates the problem of accidental
needle sticks.
12
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Also, the construction flf a syringe of the present invention does not require
complicated
or costly parts, thus, it can be produced at a relatively low cost.
It wit! be understood that most of the structure of the above example can be
changed without departing from the scope of the invention. For example, the
shaft 22
may be hollow. The needle carrier may be integral to the luer 50 instead of
being two
separate parts. The detents 264 may engage recesses within the luer 50,
instead of
beyond the lust 50. Engaging means other than detents and recesses may be used
between the plunger and the needle holder. The needle 44 can be non-central.
The
needle 44 can be pulled back into the syringe body 10, at an angle, to make it
less easy
to pull out. Various ribs, lips and external seals are mentioned in the above
description
as being axially spaced. They can be spiral if desired, as can corresponding
opposing
grooves where present, other shapes are also possible, as long as deals are
maintained
where needed. The plunger shaft is shown as circular in cross-section, but it
can be
elliptical, as tong as a seal is maintained with fibs seat member 60.
The above described embodiment shows both the drawing of the medical fluid
and the retraction of the needle being carried out automatically. The ability
for this to
operate automatically depends on the quality and size of the vacuum formed
between
the gasket and seal member. There may be embodiments and times where the
vacuum
is insu~cient for either or both operations. 'Therefore the user may have to
provide some
pull to the plunger. However it would be less than might normally ba required
and may
still, possibly tai provided one handed. Moreover, the user is not forced to
use the
syringe as described. He can use it as a normal syringe (whilst being careful
about how
far the plunger is initially depressed}_
Whilst the background of the invention particularly concentrates on avoiding
needle stick by retracting the needle, this invention is not limited to having
a retractable
needle. The invention may involve merely the automatic filling of the syringe.
This alone
may help prevent some needle stick incidents. Even if it does not, if is still
an
improvement over the prior art as it involves less effort to use, whilst being
very simple.
Many other variations are possible within the scope of the present invention
which is only
limited as defned in the claims or elsewhere as indicated.
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