Safety syringe abstract
A safety syringe employs a mechanical logic arrangement to control
the movement of a spring-biased protective shield that covers the
needle except during an injection, and which limits the number of
injection cycles. The mechanical logic arrangement can include a
series of parallel gated tracks, and a track follower pin disposed
on the slide portion of the protective shield. There are one-way
gates and redirection gates, which can be formed as flaps with a
radial hinge in respect to the barrel axis. An alternative arrangement
can employ a rotary cam. The number of injection cycles can be two
or more, and the penetration depth for a given injection cycle can
Safety syringe claims
1. A safety syringe comprising a tubular barrel having a proximal
end and a distal end; a hollow needle affixed to the distal end
of said barrel and extending distally therefrom; a protective shield
for covering said needle and movable proximally-distally between
a distally extended protective position and a proximal exposed position;
said protective shield including a tubular slide member that fits
slidably over a distal end of said barrel and a needle cover projecting
distally from said slide member over said needle, and spring means
biasing said slide distally to urge the protective shield to its
distally extended protective position in which the needle cover
extends distally beyond a tip of said needle; a plurality of gated
tracks situated on one of said barrel and the slide of said protective
shield; and a track follower situated on a facing surface of the
other of said barrel and said slide and projecting into one of said
tracks to travel therealong and through gates thereof successively
into others of said tracks; such that said protective shield is
initially disposed in its protective position; with said follower
traveling in said tracks to permit the shield to retract proximally
to the exposed position; the follower traveling to another of said
tracks to permit the shield to extend to the protective position
after a first injection cycle; the follower traveling in a successive
one of said tracks to permit the shield to retract to the exposed
position for at least one further injection cycle, and said follower
reaching a lock position at a final injection cycle.
2. The safety syringe of claim 1 wherein said plurality of tracks
includes three tracks, and said track follower reaches a lock position
in a third one of said tracks at the end of a second injection cycle.
3. The safety syringe of claim 1 wherein said plurality of tracks
includes at least four tracks, so that the track follower reaches
the lock position at the end of a predetermined injection cycle
beyond a second injection cycle.
4. The safety syringe of claim 1 wherein plurality of tracks provides
a selective lock position in which the shield is held in a proximal
position in which the needle is at least partly exposed.
5. The safety syringe of claim 1 wherein said plurality of tracks
are situated on a cam disposed on said barrel.
6. The safety syringe of claim 1 wherein said gated tracks include
gates in the form of uni-directional flaps.
7. The safety syringe of claim 1 wherein follower includes a pin
directed axially in respect to said barrel and engaging said tracks
8. The safety syringe of claim 1 wherein said gated tracks include
a combination of unidirectional gates and redirection gates.
9. The safety syringe of claim 1 wherein said unidirectional gates
permit travel in one direction therepast in a given one of said
tracks, but block passage in the opposite direction, and wherein
said redirection gates permit passage in one direction into a successive
one of said tracks from said given one of said tracks.
Safety syringe description
BACKGROUND OF THE INVENTION
This invention relates to medical and surgical devices, namely
syringes and hypodermic needles in which a medication is injected
into a patient or by means of which blood or another fluid is withdrawn
from a patient, and is more particularly concerned with a safety
syringe in which the needle is shielded to protect patients and
medical practitioners against accidental needle-stick injuries.
The safety syringe is intended to protect the user from accidental
puncture from the needle by means of a needle guard that shields
the needle at all times other than during an injection procedure.
It is well appreciated that hypodermic needles present a danger
of cross contamination, that is, spreading of pathogens that may
be in a patient's body fluids, to other persons who may have to
handle a syringe. Accidental sticking of the needle into a doctor
or nurse is a common risk, and steps have been taken to reduce this
risk by covering or shielding the needle between injection cycles
and after injection cycles. The prior proposals have been far from
foolproof, and many of these leave the needle exposed between injections,
or may require the practitioner to use both hands to use the syringe,
which makes the shield or cover inconvenient to use.
There remains a need for a safety syringe that avoids manual operation,
that is, for a syringe in which the practitioner does not need to
take any additional steps during an injection cycle, and in which
the shield will remain over the needle except when the needle is
inserted into a vial for filling the syringe and when the needle
is actually being inserted into the patient to inject the medication.
By the same token, there remains a need for an effective safety
syringe that permits normal, one-hand operation without compromise
The safety syringe should also permit some limited number of injection
cycles, in excess of a single cycle, so that it is possible to fill
the syringe from a vial, and then inject the medication into the
patient at one, two, or some other number locations. For example,
it is sometimes necessary to apply a medicament or local anaesthetic
to a patient on both sides of a wound, and the syringe should permit
this. It is then desirable for the syringe to lock, with the shield
covering the sharp needle, after the last of the injection cycles.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide
a safety syringe in which the needle is covered before, between,
and after the injection cycles, and which avoids the drawbacks of
the prior art.
It is another object to provide a safety syringe that is of a straightforward,
simple design, and which does not require any special actions on
the part of the practitioner.
It is a more specific object to provide a safety syringe with a
spring-loaded shield that remains in the cover or guard position
except during an injection cycle, which permits one-hand operation,
and which locks in the cover or guard position after a predetermined
Nth injection cycle.
It is another object to provide a safety syringe with the features
of automatic limited cycle, one-hand operation, continuously guarded
needle, and programmability (e.g., by manufacturer) for specific
In accordance with one aspect of the present invention, a safety
syringe is made with a a tubular barrel that has a proximal end
and a distal end; a hollow needle affixed to the distal end of the
barrel and extending distally from the barrel; and a protective
shield that covers the needle and is movable proximally-distally
so that the shield has a distal or extended protective position
and a proximal exposed position. The protective shield has a tubular
slide member that fits slidably over the distal end of the barrel
and a needle cover that projects distally from the slide member
out to cover the needle. A spring or other biasing device urges
the slide member distally so that the protective shield goes its
distally extended protective position. In that position, the needle
cover extends distally beyond a tip of said needle so that the patient
and practitioner are protected from the sharp end of the needle.
A series of gated tracks are provided on the barrel and a track
follower that rides in the gated tracks is situated on a facing
surface of the slide member. The track follower, which can be a
radially oriented pin, projects into one of the tracks so it can
follow the tracks, and pass through gates successively along the
series of tracks. Alternatively, the tracks can be formed on the
slide of said protective shield, with the pin or follower on the
barrel of the syringe.
The gated tracks are arranged such that the protective shield is
initially disposed in its protective position. The follower travels
in the tracks, back and forth, in sequence to permit the shield
to retract proximally to the exposed position, and then back to
the covered or protective position. The follower travels from one
track to another in turn to permit the shield to extend to the protective
position after a first injection cycle; then in a successive one
of the tracks to permit the shield to retract to the exposed position
for at least one further injection cycle; and then the follower
travels to reach a lock position at a final injection cycle.
In some of many possible preferred embodiments the series of tracks
includes three tracks, and said track follower reaches a lock position
in the third tracks at the end of a second injection cycle. Alternatively,
there can be at least four tracks, so that the track follower reaches
the lock position at the end of a predetermined injection cycle
beyond a second injection cycle, i.e., after three or after four
injection cycles. In other alternative embodiments, one track in
the series of tracks provides a selective lock position in which
the shield is held in a proximal position in which the needle is
at least partly exposed.
The tracks or channels can be of programmed lengths to accommodate
the need to limit the depth of injection. With a given track shortened
or lengthened the needle can be limited to a shallower injection
depth or permitted to go to a deeper injection depth, as required
for a given application.
Favorably, the gates included in the gated tracks are in the form
of uni-directional flaps with a hinge axis that is directed radially,
in respect to the barrel of the syringe.
An alternative embodiment the series of gated tracks or channels
can be on a sleeve that rotates around the circumference of the
barrel of the syringe, controlling the shield extension and retraction
with cam action.
An important aspect of this invention lies in the use of one-way
gates, redirection gates, and programmed channel lengths to create
a logical sequence to control the action of the shield. The arrangement
of the tracks or channels can be manifested in many forms.
The safety needle of this invention is fully automatic, with the
shield sliding out of the way upon injection and sliding back over
the needle when the injection is complete. The safety syringe arrangement
of this invention automatically limits the number of injections
for which the syringe can be used, thus preventing a needle that
has been used on one patient from contacting a practitioner or another
patient. The incorporation of mechanical logic allows the practitioner
to operate the syringe with one hand, except when the logic sequence
requires a manual input, such as to unlock from a lock position.
The automatic, limited cycle operation is achieved through a variety
of mechanical logic mechanism that are built into the syringe at
the time of manufacture. A basic-cycle logic sequence, or standard
sequence, would be inject vial--inject patient--lock. However, the
syringes can be produced with other logic sequences by altering
the mechanical logic at the time of manufacture. One alternative
logic sequence could be inject vial--inject patient--hold open--manual
The above and many other objects, features, and advantages of this
invention will be more fully appreciated from the ensuing description
of a few selected preferred embodiments, which is to be read in
conjunction with the accompanying Drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic view of a safety syringe according to an
embodiment of the present invention.
FIGS. 2 to 6 are schematic views of the safety syringe of this
embodiment showing in sequence the safety syringe being injected
into a vial, drawing material from the vial, between cycles, injecting
the material into a patient, and post injection.
FIG. 7 shows another embodiment in which there is a limited depth
FIGS. 8 and 9 show alternate additional embodiments in which there
is a locked open position in which the needle is selectively held
FIG. 10 shows another embodiment which employs a rotary cam.
FIG. 11 shows an alternative embodiment in which there can be a
larger number of injection cycles.
FIG. 12 shows a further alternative arrangement in which the guard
is further extended over the needle following a final injection
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference now to the Drawing, FIG. 1 shows a safety syringe
10 according to an embodiment of this invention. The syringe 10
has a generally cylindrical barrel 12 with a hollow needle 14 extending
from its distal end. A plunger or piston 15 is positioned within
the barrel 12 and extends out from its proximal end. In this embodiment
a protective needle guard or shield 16 is positioned over the distal
portion of the barrel 12 and needle 14 and includes a generally
cylindrical slide portion 18 that fits over the barrel and a needle
cover portion 20 that is of narrower diameter than the slide portion
18 and fits over the needle 14. The distal end of the needle cover
20 is open to permit the needle to be exposed during an injection
cycle, and there is a generally conic wall 21 joining the slide
portion 18 and needle cover portion 20. A coil spring 22 is situated
inside the slide portion 18 between the distal end of the barrel
12 and the wall 21 to urge the protective needle guard 16 distally,
so that the needle cover portion 20 normally extends beyond the
end of the needle 14.
A mechanical logic arrangement controls the number and depths of
the injection cycles, and in this embodiment the mechanical logic
comprises an arrangement 24 of parallel gated tracks 24A, 24B and
24C disposed on the barrel 12 of the syringe 10 and oriented parallel
to the axis of the syringe. The tracks 24A, 24B, 24C are in the
form of channels, and these guide the travel of a follower 26 which
here is in the form of a pin that projects radially inwardly from
the inside surface of the slide member 18. The pin or follower is
guided from each gated track 24A, 24B to the next 24B, 24C by means
of one-way gates 28 and redirection gates 30. These gates can be
in the form of flaps that are arranged radially and that are hinged
in a radial manner with respect to the axis of the syringe 10.
Initially, as shown in FIG. 1 the syringe 10 as it comes from
the supplier, has the protective shield 16 biased distally outward
with the pin follower 26 situated at the distal end of the first
track 24A. Then, in order to fill the syringe 10 the practitioner
pushes the needle end of the syringe onto the diaphragm of a vial
V, as shown in FIG. 2 and this pushes the needle cover 20 and slide
18 back, i.e., proximally, so that the pin 26 travels past a one-way
gate 28 and then out along the track 24A, as shown in FIG. 3. This
compresses the spring 22. Now the practitioner can fill the syringe
by drawing back the plunger 15 (this action is not shown). When
the syringe 10 is withdrawn from the vial, the spring 22 urges the
protective shield forward, i.e., distally, as shown in FIG. 4 so
that the cover 20 protrudes past the end of the needle 14. During
this motion, the follower pin 26 travels to the one-way gate 28
and a redirection gate 30 directs the pin 26 into the adjacent channel
The needle cover 20 remains in a protective position over the needle
14 until the syringe is used to inject the medication into a patient
P. As shown in FIG. 5 pushing the needle 14 through the skin of
the patient P deflects the needle cover 20 proximally, and the follower
pin 26 travels proximally along the track 24B past a one-way gate
28 in that track. After the practitioner has injected the medication
into the patient P, he or she withdraws the syringe, and the spring
22 pushes the protective shield forward, so that the needle cover
20 again projects beyond the end of the needle 14 as shown in FIG.
6. During this movement, the pin follower 26 travels back along
the track 24B, and through another redirection gate 30 into the
next track 24C. In this case, where the safety syringe is limited
to two injection cycles, the third track 24C has a one-way gate
28 that is oriented to prevent the pin 26 from travel, so that the
protective shield 16 remains held in the protective position and
cannot be deflected to expose the needle 14.
Of course, the redirection gates, one-way gates, and the lengths
of the channels or tracks can be arranged for a different mechanical
programming, that is, to achieve a different number of injection
cycles, or to limit injection depth, for example. Also, it is possible
for the gates to be configured with flaps hinged along a circumferential
line, rather than along a radial line. The channels or slots that
comprise the arrangement 24 of tracks can be formed directly on
the barrel 12 or may alternatively be formed on a sleeve that fits
onto an existing syringe barrel. Also, while this embodiment shows
the pin 26 on the inside of the slide 18 and the tracks 24 on the
barrel 12 a reverse arrangement could be employed, with the pin
26 positioned on the barrel 12 and with the tracks 24 formed on
the inside surface of the slide 18. Also, there can be a pair of
similar tracks 24 and a pair of pins 26 on opposite sides of the
syringe for a balanced operation.
One alternative arrangement is illustrated in FIG. 7 in which
the safety syringe employs an arrangement of tracks 24'. Here, the
second track 24'B has a stop 32 that limits travel of the pin 26
in the proximal direction, and thus limits travel of the needle
cover 20 to a programmed amount. This configuration can be employed
where it is desired to limit the injection depth of the needle 14
into the patient P. The remaining elements of this safety syringe
can be the same as with the first embodiment, and are identified
by the same reference numbers, with no need to repeat their description.
The stop 32 can be placed in any of the channels or tracks, depending
upon the need for limiting the depth for any given injection cycle.
It is also possible to lengthen any of the tracks or channels to
permit more of the needle to be exposed for any given injection
FIG. 8 illustrates another embodiment of the safety syringe of
this invention in which its programmed track arrangement 24"
has a lock position 34 formed in third track 24"C that can
be accessed from the second track 24"B, e.g., by twisting the
protective shield 16 relative to the syringe barrel 12. This embodiment
can be used when it is desired to hold the needle cover 20 back
to expose a portion of a needle 14. This permits the practitioner
the option of multiple additional injection cycles, with the needle
continuously exposed. When the last injection cycle is completed,
the practitioner can simply twist the shield so that the pin 26
can travel back along the track 24"B to the locked position
at the distal end of the track 24"C.
Another embodiment is shown in FIG. 9 in which the syringe can
be set into a locked exposed position. Here, there is a set of tracks
24'" with a curved pathway 36 at a proximal part of the tracks
24'"B and 24'"C, so that the pin 26 travels to the lock
position automatically. The syringe can be released from the locked
position by twisting the shield 16 relative to the barrel 12 so
that the pin 26 moves to the final position at the distal end of
the track 24'"C.
As shown in FIG. 10 in some embodiments of this invention the
syringe may employ a rotary cam or sleeve 40 in which there are
a series of gated tracks or channels 40A, 40B, 40C, 40D. The cam
40 is fixed axially on the distal end of the barrel 12 but can
rotate, as shown, when the slide portion 18 of the protective shield
16 moves back and forth. This permits the cam follower pin 26 to
ride in the series of gated channels from an initial position at
the distal end of the first channel 40A to a final locked position
40E at the distal end of the last channel 40D.
An embodiment that permits more than the two injection cycles of
the foregoing embodiments is illustrated in FIG. 11 in which the
elements that are the same as in the previous embodiments are identified
with the same reference numbers. Here, the programmed mechanical
logic includes a sequence 124 of parallel gated tracks 124A to 124E,
such that there can be four injection cycles, with the pin 26 residing
at the distal end of the final track 124E at the end of the last
injection cycle, such that the needle cover 20 is situated over
the needle 14 at the end of that injection cycle.
A further embodiment of this safety syringe 10 is shown in FIG.
12. Here, an extension 50 at the distal end of the final track 24C
allows additional distal travel of the pin 26 and the protective
shield 16. This leaves the needle cover 20 extending further past
the distal, sharp end of the needle 14 in the locked position after
the final injection cycle, for use when additional protection from
needle-stick is desired.
While the invention has been described with reference to specific
preferred embodiments, the invention is certainly not limited to
those precise embodiments. Rather, many modifications and variations
will become apparent to persons of skill in the art without departure
from the scope and spirit of this invention, as defined in the appended