Medical syringe abstract
A single use disposable medical syringe is constructed and operated
in a manner which prevents transmission of infection by the syringe
after its use for inoculation. The syringe is marketed in a sterile
package ready for use. The syringe needle is then covered by a shield.
The syringe plunger assembly is then releasably locked to the barrel
of the syringe. Following opening of the sterile package and removal
of the needle shield, the plunger assembly is operated to fill the
syringe barrel with medication and to inject the patient. Following
injection, a piston head housing is unlocked from the syringe barrel
and the plunger assembly is retracted toward the rear of the barrel
and becomes automatically locked in this position with the piston
head housing. The needle is disposed within the barrel rearwardly
of a safety shield on the forward end of the barrel containing a
Medical syringe claims
1. A medical syringe comprising a syringe barrel, a safety shield
on the forward end of the syringe barrel including an elastic membrane
spaced substantially rearwardly from the forward end of the safety
shield, a piston head housing, means releasably locking the piston
head housing in the forward end portion of the syringe barrel immediately
behind the safety shield, a plunger assembly for the syringe comprising
a plunger shank, a polygonal cross section piston head on the forward
end of said shank, a piston element on the shank rearwardly of the
piston head wipingly sealingly engaging the bore of said barrel,
a piston head well carrying a needle and being captively held within
said piston head housing and having a cavity receiving said piston
head and having a polygonal cross sectional shape matching the shape
of the piston head, stop means within the piston head housing to
limit rotation of the piston head well therein, a disc housing fixed
on the rear end of said barrel, a friction disc snugly rotationally
held within the friction disc housing and having a geometric non-circular
opening formed therethrough, said plunger shank being received through
said geometric non-circular opening and having a matching cross
sectional shape, whereby rotation of said shank will rotate said
friction disc, said piston head and piston head well and said piston
head housing to release the latter from said barrel, a locking disc
fixed on said shank somewhat rearwardly of said piston element and
being movable with said shank through the bore of said barrel, and
a non-releasable locking means for said locking disc fixed to the
rear end portion of said barrel immediately forwardly of said disc
housing and being engageable with the locking disc in response to
retracting of said stem to lock the plunger assembly including said
piston head housing in a safety retracted position on said barrel
with said needle enclosed by the barrel rearwardly of said safety
shield and elastic membrane, and said needle piercing the elastic
membrane and extending forwardly thereof through the safety shield
prior to usage of the syringe.
2. A medical syringe as defined in claim 1 and a sterile package
means completely enclosing said syringe prior to use thereof and
prior to the opening of said package.
3. A medical syringe as defined in claim 2 and a readily removable
needle enclosing shield on the syringe within said sterile package
and prior to using the syringe.
4. A medical syringe as defined in claim 1 and said piston head
being captively held within the piston head housing between two
end walls of the housing, one of which end walls has an opening
adapted to receive said piston head therethrough so that the piston
head may enter the cavity of said piston head well.
5. A medical syringe as defined in claim 1 and the first-named
means comprising internal locking lugs on said barrel near the forward
end of the barrel, and cooperative locking slots in the side wall
of the piston head housing.
6. A medical syringe as defined in claim 5 and said locking slots
comprising bayonet slots.
7. A medical syringe as defined in claim 1 and the polygonal cross
section piston head comprising a forwardly tapering truncated pyramid
8. A medical syringe as defined in claim 7 and said plunger shank
having cruciform cross section, said friction disc having a cruciform
opening formed therethrough receiving said shank.
9. A medical syringe comprising a syringe barrel, a safety shield
on the forward end of said barrel including an elastic membrane
adapted to be penetrated by a needle of the syringe, a piston head
housing rotationally releasably locked within the forward end portion
of the syringe barrel, a piston head well having a non-circular
cross section and a non-circular cavity disposed captively within
the piston head housing and adapted for limited rotation only therein
on the longitudinal axis of the syringe, a syringe plunger having
a shank and a non-circular piston head on the forward end of the
shank engageable within the cavity of said well, the piston head
housing including a rear end wall having an opening through which
the piston head can enter said cavity and leave the cavity, a piston
element fixed on said shank rearwardly of said piston head and said
piston head housing, a locking disc fixed on said shank rearwardly
of said piston element, and a non-releasable locking means for said
locking disc fixed on the rear end portion of the syringe barrel
whereby the syringe plunger is lockable in a safety retracted position
with the needle of the syringe enclosed by said barrel rearwardly
of said safety shield and membrane, and said needle being attached
to the forward end of said piston head well in communication with
the cavity thereof.
10. A medical syringe comprising a syringe barrel, a first non-releasable
syringe plunger locking means at the rear end of said barrel and
being fixed relative thereto, a safety shield fixed on the syringe
barrel at the forward end thereof and having a safety needle pierceable
membrane, a second releasable syringe plunger locking means fixed
on the syringe barrel substantially at its forward end and somewhat
rearwardly of said safety shield and membrane, a syringe plunger
assembly guidably engaged in the syringe barrel and being longitudinally
movable and turnable therein, said plunger assembly including a
stem, a piston element fixed on said stem and a locking element
fixed on said stem somewhat rearwardly of the piston element and
being engageable with said first non-releasable syringe plunger
locking means, a piston head on said stem forwardly of the piston
element, a piston head well having a cavity adapted to receive the
piston head therein removably, a syringe needle secured to said
well, and a piston head housing movably disposed in said barrel
and substantially surrounding and captively holding said well and
having an opening through which said piston head can enter and exit
the piston head housing and well, and cooperative releasable locking
means on the piston head housing and being engageable with said
second releasable syringe plunger locking means.
Medical syringe description
BACKGROUND OF THE INVENTION
Infectious diseases, such as AIDS and serum hepatitis, have created
an urgent need for a reliable, practical and convenient anti-contaminating
medical syringe. Such a syringe must be relatively inexpensive to
manufacture, rendering it disposable after a single injection or
The objective of the present invention is to fully satisfy the
need for an anti-contaminating syringe in terms of fully protecting
the patient, medical personnel and innocent third parties against
the possibility of infection being transmitted by the syringe.
Toward this end, the syringe according to the present invention
is provided in a sterile, easily openable package and is pre-adjusted
so that it is ready to be used for injecting a patient after removal
from the sterile package and after separation of a removable shield
from the forward end of the syringe which encloses the syringe needle
prior to use.
The syringe is operated conventionally to draw liquid medication
from a bottle having an elastic diaphragm or stopper and to then
inject the patient.
A housing element within which a piston head of the syringe plunger
assembly is captured and which is locked to the forward end of the
syringe barrel prior to and during normal usage of the syringe is
unlocked by a twisting action of the plunger assembly and is then
retracted with the plunger assembly toward the rear of the syringe
barrel where such assembly, including the piston head housing, becomes
automatically positively locked to effectively prevent reuse of
the syringe. In this retracted position, the syringe needle is held
inside of the barrel rearwardly of a safety shield on the forward
end of the barrel containing an elastic membrane through which the
needle projected prior to and during the injection process. The
retracted needle cannot be touched nor can the membrane in the safety
shield be touched, thus rendering the transmission of infection
by the syringe virtually impossible.
Other features and advantages of the syringe according to the present
invention will become apparent to those skilled in the art during
the course of the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a syringe and sterile package according
to the present invention with the syringe conditioned for usage
following removal from the sterile package and separation of a needle
shield from the syringe.
FIG. 2 is a longitudinal vertical section taken through the syringe
with its plunger assembly locked in a retracted safety position
ready for disposal following a single use.
FIG. 3 is an exploded perspective view of the syringe, partly broken
FIG. 4 is an enlarged fragmentary longitudinal vertical section
taken through the syringe with its plunger assembly in a forwardmost
FIG. 5 is a transverse horizontal section taken on line 5--5 of
FIGS. 6 and 7 are similar sections depicting stages of rotation
of the plunger assembly relative to and with a piston head housing.
Referring to the drawings in detail wherein like numerals designate
like parts, a single-use disposable medical syringe 10 according
to the invention comprises a syringe barrel 11 provided slightly
rearwardly of its forward end with a pair of internal diametrically
opposed locking lugs 12. A cylindrical piston head housing 13 having
spaced end walls 14 and 15 receives a piston head well 16 captively
therein, the well being held or captured between the two end walls
14 and 15 of the housing 13.
The well 16 has a cavity 17 preferably in the shape of a downwardly
tapered truncated pyramid adapted to receive through its top a piston
head 18 of like shape which nests within the cavity 17. The piston
head 18 enters and leaves the cavity 17 through an opening 19 formed
in the end wall 14 of the housing 13. The housing 13 contains therein
a pair of diametrically opposite stop lugs 20 which resist rotation
of the well 16 in the housing 13 beyond prescribed limits. The housing
13 is provided in its cylindrical side wall at diametrically opposite
points with bayonet locking slots 21 adapted to receive and release
the locking lugs 12 in response to twisting of the housing 13 within
the barrel 11 as will be further explained. A tubular pointed syringe
needle 22 is secured to the end wall of the well 16 with its bore
in communication with the cavity 17 of the well.
The syringe further comprises a disc housing 23 fixed to the rear
end of the barrel 11 and having opposite side finger grips 24. The
housing 23 has a serrated bore 25 receiving therein snugly but rotationally
an externally serrated friction disc 26 having a cruciform opening
27. A plunger lock ring 28 is fixed in the housing 23 and is provided
at diametrically opposite points with a pair of internal spring
locking tabs 29 whose purpose will be described.
A syringe plunger assembly 30 includes a straight elongated cruciform
plunger stem 31 which engages somewhat loosely through the cruciform
opening 27 of the friction disc 26. The rear end of the plunger
31 is equipped with a thumb plate 32.
The plunger assembly further includes near the forward end of the
stem 31 a piston 33 equipped with an O-ring 34. The piston 33 is
fixed on the stem 31 somewhat rearwardly of the piston head 18 which
forms a part of the plunger assembly 30.
A plunger assembly locking disc 35 is also fixed to the stem 31
somewhat rearwardly of the piston 33 and is sized to pass freely
through the syringe barrel 11 when the plunger assembly is shifted
longitudinally of the barrel 11. The piston O-ring 34 sealingly
wipes the bore of the barrel 11.
As will be further described, when the plunger assembly 30 is retracted
to its locked safety position as shown in FIG. 2 the locking disc
35 enters the plunger locking ring 28 and depresses the spring locking
tabs 29 which then snap back to their normal positions in front
of the disc 35 FIG. 2 to lock the plunger assembly 30 in the safety
retracted position, thereby preventing reuse of the syringe.
The syringe further comprises a forward end tapered safety shield
36 having a narrow needle clearance opening 37 and a rearward rubber
or rubber-like membrane 38 held firmly within a seating recess 39
at the rear of the shield 36. The needle safety shield 36 is fixed
to the forward end of the syringe barrel 11 by a sleeve portion
36' to which the lugs 12 are preferably attached. Prior to use of
the syringe for injecting a patient, the needle 22 penetrates the
rubber membrane 38 and projects entirely through and beyond the
safety shield 36 FIGS. 1 and 4. Following use of the syringe for
making an injection and following retraction of the plunger assembly
30 FIG. 2 the needle 22 is bodily inside of the barrel 11 and
well rearwardly of the membrane 38 from which it has been withdrawn.
Hence, no one can touch the retracted needle 22 or the membrane
38 which is at the rear of the safety shield 36.
As shown in FIG. 1 the syringe prior to use is enclosed in a conventional
sterile package 40 having a tear-away corner 41 to facilitate opening
the package. Within the sterile package, the syringe carries an
easily removable needle shield 42 which is removed from the syringe
to expose the needle after the syringe is taken from the sterile
As previously explained, the syringe 10 as taken from the sterile
package 40 is ready for use after removal of the needle shield 42.
The piston head housing 13 is locked to the front of the barrel
11 by the lugs 12 and bayonnet locking slots 21. The well 16 is
captively held in the housing 13 and the piston head 18 is nested
in the mating cavity 17 of the well 16.
The needle 22 is now inserted through the diaphragm or stopper
of a medicine bottle and the plunger assembly 30 is retracted to
draw liquid into the barrel 11. During this operation, the piston
33 produces the necessary suction in the syringe barrel to draw
in the liquid medication. The piston head housing 13 remains locked
in the forward position, FIG. 4 and the well 16 is still captively
held by the housing 13. However, the tapered piston head 18 can
move rearwardly with the rest of the plunger assembly 30 and can
exit the housing 13 through the provided opening 19.
The injection or innoculation is now carried out by thrusting the
plunger assembly 30 forwardly, during which the piston 33 forces
the liquid into and through the needle 22 which is penetrating the
tissue of a patient. At the end of the forward movement of the piston
assembly, the head 18 passes through the opening 19 and is again
received in the cavity 17 as shown in FIG. 4.
Following this, the plunger assembly 30 is rotated on its longitudinal
axis, causing the piston head 18 to turn the well 16 an amount limited
by the two stops 20 of housing 13. When these stops are engaged
by the well 16 as shown in FIG. 6 the housing 13 begins to turn,
as shown in FIG. 7 and the housing rotates relative to the barrel
11 and the sleeve portion 36' attached to safety shield 36. This
rotation allows separation of the two lugs 12 from the housing 13
by passing through the bayonnet locking slots 21 thereof which in
turn allows retraction of the plunger assembly 30 with the housing
13 toward the rear of the barrel 11 as shown in FIG. 2.
During this movement, the locking disc 35 on plunger stem 31 trips
over and behind the spring locking tabs 29 and the plunger assembly
and housing 13 become securely locked in the safe retracted position
with the needle 22 completely enclosed in the syringe barrel 11
well rearwardly of the membrane 38. The plunger assembly 30 cannot
again be pushed forwardly because the locking means 29 etc. is
non-releasable. The syringe is now disposed of in a proper manner,
and the possibility of spreading infection with the syringe is rendered
Except for the needle 22 the disposable syringe can be formed
from inexpensive plastics materials and rubber.
It has not been previously described that the plunger stem 31 has
a short cylindrical portion 31' between the piston head 18 and piston
33 FIGS. 2 and 4. This short cylindrical portion is necessary to
enable rotation of the stem 31 relative to the housing 13 prior
to the turning and unlocking of the latter to enable retraction
of the assembly to the safety locking position shown in FIG. 2.
The initial rotation of the stem 31 relative to the housing 13 enabled
by the cylindrical portion 31' is depicted in FIGS. 5 and 6.
Again referring to the friction disc 26 this disc has two functions
in the invention. First, it provides alignment and guidance of the
stem 31 and the elements attached thereto, and secondly, the friction
disc allows rotation of the stem 31 and plunger assembly relative
to the disc housing 23 which is fixed on the barrel 11.
It is to be understood that the form of the invention herewith
shown and described is to be taken as a preferred example of the
same, and that various changes in the shape, size and arrangement
of parts may be resorted to, without departing from the spirit of
the invention or scope of the subjoined claims.