Retractable needle syringe

A retractable hypodermic needle configured for one-time use wherein the needle is spring loaded and automatically irretrievably retracted into the hypodermic syringe when the syringe plunger is fully depressed, whereby protrusions on the end of the plunger engage tabs holding the spring loaded needle to release the needle for retraction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to hypodermic needles and more specifically to a 
hypodermic needle which retracts into the syringe after use, thereby 
preventing reuse and the spread of diseases normally associated therewith. 
2. Description of the Prior Art 
It is well known that diseases can be spready by re-using a needle and that 
a person can come in contact with a disease by being accidently scratched 
by the needle. Hypodermic needles and syringes on the market today have 
fixed needles attached to a cylinder. After the needle has been used, it 
should be disabled and destroyed to prevent transmission of diseases. 
But, even thrown away needles can expose one to disease as the needle and 
syringe can quite often be re-used by an unsuspecting person. The 
contaminated needle can also accidently cut or prick a person, exposing 
that individual to a transmittable disease. Efforts have been made to 
educate people not to re-use needles, but the spread of disease through 
needles is still widespread and hospital personnel have been accidently 
cut by contaminated needles even though they are extremely careful and 
well aware of the dangers. Some medical facilities have equipment to break 
the needle from the syringe or cylinder rendering the syringe harmless, 
but, these devices are not available to the general public. Some syringes 
have a protective cap covering the needle which can be placed over the 
needle after use, allowing the needle to be broken from the syringe, but 
here again an accidental scratch from the needle could be devastating. 
SUMMARY OF THE INVENTION 
The present invention effectively overcomes the problems of the prior art 
and provides for an efficient way of disposing of a spent needle without 
subjecting one to the potential hazzards of handling it after use while 
simultaneously removing the needle from circulation, whereby reuse becomes 
impossible.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
This invention may perhaps be best understood by making reference to 
several drawings and specifically describing one of the preferred 
embodiments. 
In the needle's initial state, in FIG. 3, the handle cannot be pushed down. 
The needle is inserted into a container of fluid and when the handle (7) 
is pulled back, stop (8) falls off, and the slide or plunger moves away 
from the needle, thus creating a vacuum to draw fluid from the container 
into the syringe. When a desired fluid level is reached, the operator 
stops the pulling process and adjusts the dose. The needle is inserted 
into a patient or area. Then, the handle (7) is pushed in to force the 
fluid through the needle. When the slide extensions (9) reach the clamps 
(10), a push on handle (7) provides a force to release or break the 
clamps, thus releasing the hold on the needle. The needle is automatically 
drawing through the gasket (11) and pulled into the inside cylinder (6) 
where is becomes inaccessible and non-reusable. 
FIG. 3 shows a syringe and needle in its initial state with needle (12) 
protruding through gasket (11) which serves as a leak-proof seal for the 
syringe (14) and stabilizes the shaft of the needle (12). In this case the 
head of the needle (13) is attached to a tensioned spring (16) by an 
attachment means (15), which can employ any of the means shown in FIGS. 
1a, 1b or 1c. The needle is held in place by clamps or tabs (10) 
fabricated of breakable material or at least a material malleable enough 
to allow the needle head to be released upon the exertion of force by 
projections (9) on the end of plunger 18. The tabs (10) can be moulded 
into the syringe end plate through which the needle protrudes or they 
could be moulded as part of a washer plate (not shown) which is 
appropriately seated within syringe body (14). Spring (16) is shown 
extended and under tension with one end connected to the needle head (13) 
and the other end connected to the end surface of the inside cylinder 
(17). In this mechanical state, the needle (12) and head are in mechanical 
equilibrium wherein the spring force tends to pull the needle through the 
gasket (11) and the clamp (10) prevents it from being retracted into the 
body of the syringe. It should be noted here that the syringe is shown in 
its simplest form with simple finger tabs on the upper and outer portion 
of the syringe cylinder for holding the syringe, but it should be fully 
understood that finger tabs are well known in the art and that the handle 
or plunger cap (7) is thumb actuated and may also contain a lip to extract 
the plunger from the top of the cylinder during the filling of the 
syringe. 
A slide or plunger mechanism (18) has projections (9) on its bottom 
surface. These projections will release the clamps or tabs (10) when the 
handle (7) is pushed down. In the initial state, the handle is prevented 
from being pushed down by a mechanical stop (8). The mechanical stops (8) 
can be any type of temporary bushing, such as slip rings, or two 
semi-circlar inserts, as shown in FIG. 7, placed between handle (7) and 
the top end of syringe housing (14) to assure that the protrusions (9) on 
the plunger (18) do not release the tabs (10) until the syringe has been 
used and the needle is ready to be retracted into the inside cylinder (6). 
The stops (8) are released and fall from their places upon filling the 
syringe, thus readying the syringe for retraction of the needle upon 
demand. When the handle is pushed down, the projections (9) release the 
clamps (10) and attachments (15) pull the needle through gasket (11) and 
pull the head through the diaphragm (19). Diagraphm (19) prevents liquid 
from entering the spring cylinder until the diaphragm is broken. The 
needle and head are then pulled deep into the inside cylinder (12). Once 
inside the cylinder (6), the needle (12) cannot be again pushed through 
the gasket by any means, thus rendering the needle inaccessible and 
non-reuseable. 
FIG. 5 shows another arrangement of the invention. In this arrangement, a 
spring mechanism is under compression in its initial state. Spring force 
is applied to the needle head (20) tending to drive the head and needle 
through diaphragm (21) and into chamber (22). In the initial state, clamps 
(23) hold the needle head from moving up or down. When slide (24) is moved 
in the direction of the clamps, the projections (25) on the bottom of the 
slide release the clamps (23) by a release mechanism or by breaking the 
clamps, thus releasing the needle and needle head. The force of the spring 
mechanism (26) drives the needle into chamber (22) thereby rendering 
inaccessible and non-reuseable. 
FIG. 6 shows a top view of the circular projection (25) and the diaphragm 
(21). FIG. 7 shows a top view of the circular mechanical stop (8) which 
prevents the handle (7) of FIGS. 3 and 5 from accidently moving forward 
and triggering the retraction of the needle. The stop (8) falls from the 
syringe as the plunger is activated to fill the syringe.