Safety syringe abstract
A safety syringe including a generally cylindrical needle body
having first and second opposite ends, the first end being open,
a needle member extending from the second end of the needle body,
a plunger having a central bore and piston secured to an end of
the plunger, the plunger and piston being inserted through the first
end of the needle body, the piston sealingly engaging an inner surface
of the needle body, a stylette having a sharp point, the stylette
extending through the needle member, penetrating through and frictionally
engaging the piston and extending into the central bore of the plunger,
wherein the sharp point of the stylette is normally retracted into
the needle member to prevent needle-stick injuries, and extends
from the needle member upon applying a biasing force to the piston
by depressing the plunger, whereby frictional engagement between
the piston and the stylette forces the sharp point to be exposed
from the needle member.
Safety syringe claims
I claim:
1. A safety syringe, comprising:
a generally cylindrical needle body having first and second opposite
ends and an interior volume, said first end being open and said
second end having a opening;
a needle member extending from said second end of the needle body
and being in communication with said in error volume through said
opening;
a plunger having a central bore and piston secured to an end of
the plunger, said plunger and piston being inserted through said
first end of the needle body, said piston sealingly engaging an
inner surface of the needle body;
a stylette having a sharp point, said stylette extending through
the needle member, penetrating through and frictionally engaging
said piston and extending into the central bore of the plunger,
said piston being slidable with respect to and over a length of
said stylette, wherein
said sharp point of the stylette is normally retracted into the
needle member to prevent needle-stick injuries, and extends from
the needle member upon applying a biasing force to said piston by
depressing said plunger, whereby frictional engagement between the
piston and the stylette forces said sharp point to be exposed from
said needle member.
2. The safety syringe of claim 1 wherein said piston is flexible
between biased and unbiased positions.
3. The safety syringe of claim 1 further comprising a side port
along an outer surface of the needle member through which medication
is released.
4. The safety syringe of claim 1 further comprising stop means
to prevent said sharp point from extending from needle member beyond
a predetermined distance.
5. The safety syringe of claim 4 wherein said stop means comprises
a step along an inner surface of the needle member and a crimped
portion of the stylette which abuts said step.
6. The safety syringe of claim 5 wherein said step is cylindrical.
7. The safety syringe of claim 6 wherein said step contains a
plurality of axial flow holes extending therethrough.
Safety syringe description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a syringe. More particularly,
the invention relates to a safety syringe which prevents needle-stick
injuries unless a biasing force is applied to the plunger thereby
to expose a sharp point necessary for penetration of tissue.
2. Related Art
Recently, concerns have been raised over protecting medical personnel
from coming into contact with infected equipment. Such concerns
have lead to the development of safety syringes which protect or
shield the sharp point of the needle when not in use, so as to prevent
needle-stick injuries from used syringes.
An example of such a syringe is shown in U.S. Pat. No. 5088986
which utilizes a needle sheath which is retractable so as to expose
a needle for administering medication. The mechanism used to retract
the sheath is relatively complex, relying on a switch device and
a spring-loaded mechanism.
U.S. Pat. No. 4969877 discloses a syringe having a retractable
needle. The syringe includes an outer housing having an inner chamber
which is slidable therein, the inner chamber having a needle extending
therefrom. The syringe is adapted to lock into a retracted position
and into a deployed position forwardly within the housing for injection.
U.S. Pat. No. 4941883 discloses a syringe which is somewhat similar
to that shown in the '877 patent in that a retractable needle is
provided. However, use is made of a reservoir which is parallel
to a sheath in which the needle retracts. Fluid communication between
the needle and the reservoir is achieved through a radial opening
and radial apertures, and separate plungers are used for deployment
of the needle and injection of medication. Other safety needle apparatuses
are shown in U.S. Pat. Nos. 4834718 and 4507117.
Each of the state of the art safety needles described above has
a relatively complex structure, such as spring-loaded switch mechanisms,
to protect the sharp point of the needle. Accordingly, while such
syringes attempt to offer increased safety, they are costly to manufacture.
Additionally, the prior art safety syringes require additional manipulation
of the safety devices to ready them for injecting medication. Accordingly,
objectives of the present invention include provision of a simple,
easy to use and cost-effective safety syringe which is adapted to
prevent needle-stick injuries.
SUMMARY OF THE INVENTION
The invention provides a safety syringe having a generally cylindrical
needle body, a plunger having a piston inserted into a first end
of the needle body, and a needle member extending from the second
end of the needle body. Further, a stylette having a sharp point
is positioned such that it extends through the needle member, penetrates
through and frictionally is engaged by the piston, and extends into
a central bore in the plunger. According to this arrangement, only
when the user depresses the plunger, the sharp point of the stylette
is exposed for penetration of skin. In this regard, when the plunger
is depressed, the frictional engagement between the piston and stylette
passing therethrough causes the stylette to move with the piston
member such that the sharp point of the stylette is exposed.
Preferably, the piston is flexible between biased and unbiased
positions, such that upon release of the plunger, the piston returns
to its unbiased position to retract the sharp point into the needle
member. Thus, the syringe is automatically rendered safe upon release
of the plunger.
Preferable embodiments include a side port along an outer surface
of the needle member through which medication is released. Additionally,
a stop device may be provided to prevent the sharp point of the
stylette from extending beyond a predetermined distance from the
distal end of the needle member.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the present safety syringe, having
cut-away portions to show the extension of the stylette.
FIG. 2 is a cross-sectional view of section line II--II in FIG.
1.
FIG. 3 is a side view showing deformation of the piston of the
present safety syringe; and
FIGS. 4 and 5 show partial cross-sectional views of the present
safety syringe showing stop means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1-5 show an embodiment of the present invention not drawn
to scale, including safety syringe 1 having needle body 2 which
includes a plunger 4 inserted through a first, open end of the needle
body, and a needle member 5 extending from a second end of the needle
body. Needle body 2 includes handle portion 3 useful for gripping
by the user. Additionally, piston member 8 is secured to an end
of plunger 4 piston member 8 tightly and frictionally engaging
an inner surface of the needle body 2 so as to be in sealing contact
therewith.
Of particular importance, stylette 6 extends through needle member
5 penetrates piston member 8 and extends into plunger 4 through
axial bore 12 thereof, as shown in FIG. 2. Stylette 6 frictionally
engages piston 8 which may be formed of a rubber material, for example.
Stylette 6 bears a sharp point 7 at a distal end thereof, stylette
6 terminating at opposite end 9. Additionally, needle member 5 may
include a side port 10 through which the medication flows.
During operation, the user applies a pressing biasing force to
plunger 4 to force initial movement of piston 8 through needle body
2 just prior to forcing needle member 5 through tissue of the patient.
Because of the frictional engagement between piston 8 and stylette
6 the stylette initially moves in conjunction with the piston 8
so as to force sharp point 7 to protrude from needle 5 as shown
in FIG. 1. Appropriate stop means may be provided in the needle
member 5 to prevent the sharp point 7 from protruding more than
a predetermined distance from needle member 5 discussed in more
detail below.
In a preferred embodiment, the piston member 8 is somewhat flexible
such that upon applying the pressing biasing force to plunger 4
it deforms as shown in FIG. 3. Accordingly, upon release of the
biasing force, the piston returns to its unbiased position, thereby
retracting sharp point 7 back into needle member 5. Thus, the present
syringe is rendered automatically safe upon releasing plunger 4.
FIGS. 4 and 5 show a particular form of the stop means used to
prevent the sharp point 7 from extending too far beyond the end
of needle member 5. Crimped portion 14 is provided to abut step
13 having axial througholes 15 as shown in FIG. 4. At that point,
axial movement of the stylette 6 is stopped, but piston member 8
continues to slide axially simply by pressing plunger 4 with enough
force to overcome the friction between stylette 6 and piston member
8. It is noted that the frictional engagement between piston member
8 and stylette 6 is chosen to be high enough such that sharp point
7 remains exposed during puncturing of tissue of the patient.
The present safety syringe does not impose any material requirements
beyond those of a conventional syringe. For example, plunger 4 and
needle body 2 may be formed of a suitable plastic material, while
piston member 8 may be formed of a suitable rubber material. Stylette
6 needle member 5 and sharp point 7 may be all formed of appropriate
surgical-grade metals.
While a particular embodiment has been shown and described, it
will be understood that the invention is not limited thereto since
many modifications may be made and will become apparent to those
skilled in the art without departing from the scope and spirit of
the claims which follow. |