Note: Descriptions are shown in the official language in which they were submitted.
WO 93/10842 2 12 4 S 7 ~ PCI/NL92J00217
In iection syrinqe
The invention relates to a syringe according to the
precharacterising portion of Claim 1.
Such a syringe, which further corresponds to the
precharacterising portion of Claim 11, is known from the
prior Netherlands patent application 90 00 487 by the same
Inventor.
Such syringes are intended to draw in injection liquid
from a storage bottle closed by a pierceable stopper
following removal from their packaging, the piston/piston
rod assem~ly in its initial position being in the extended
condition. The air present in the container is driven into
the bottle upon the needle being stuck into the bottle, so
that, upon subsequent withdrawal of the assembly, the
drawing in of liquid is not impaired by the lower pressure
in the bottle. Prior to injection of the injection liquid
into the patient the remaining air is first ejected from the
container and the needle, the needle being directed upwards.
AS the piston is completely pressed inwards during
injection, coupling with the needle foot takes place.
A syringe thus made has the advantage that the air in
the prepacked syringe may be made sufficiently sterile to
avoid pollution of the contents of the bottle, but it is a
disadvantage that the prepacked syringe has a considerable
length, so that such prepacked syringes take up uuch space.
It is likewise a disadvantage that in case of incorrect
operation of this ~yringe, the coupling of the piston with
the needle foot can take place prematurely. It is a further
disadvantage that the stroke limiting means have a
relatively complicated shape, which has a negative influence
on manufacturing cost. Since such syringes are ~eant to be
disposable, costs must be limited as much as possible.
The invention provides a syringe of the type stated in
the precharacterising portion of Claim 1, ~hich can be
prepacked w.th the assembly in its inwardly shi~ted position
and which can be manufactured very cheaply.
W093/10842 PCT/NL92/~217
212~574 2 -
To that end, the syringe according to the invention is
characterised by the feat~res enumerated in the
characterising portion of Claim 1.
The increase of the stroke of the assembly then takes
5 place after the assembly has been pressed inwards for the
first time following the drawing in of air, so that coupling
with the needle foot can take place only after the assembly
is pressed inwards for the secvnd time.
A first embodiment of the syringe accordïng ~o the
10 invention has the additional features enumerated in Claim 2,
whereas Claims 3 and 4 enumerate f~rther advantageo~s
characteristics thereof which prevent shifting of the ring
premat~rely.
Claims 5, 6 and 7 relate to a somewhat modified
15 embodiment, in which the ring is outwardly expandable, and
- the functioning ther2sf can not deteriorate even in case of
ageing, while Claims 8 and 9 enumerate certain embodiments
of the resilient ring, and Claim 10 relates to a favourable
embodiment of the casing of a syringe according to the
20 invention.
_ _ . , _ _. . ; . ., . . ,.. . . . . ., , . . , ., . . . ,. , . . . . . , . ... , _ ..
,
,s . . . . - .. .. s , - . . ... . . ..... .. . .
I~C-'. V()~ PA I~lI.'~llt~l 01 _ : 4~ r~ R ~ +49 8~ '>:353S34-1~;5: 1lt 4
2 12 4 S 7 i~
9.~,t:.~
Wo 91/ 04 065 c~owe ;~ stop r~g which i~ an externally
bias6ed sp~it ring closely fltting in a seat of the syr~ nt3~ casing,
and i~s provided in its inn~r ~ ace with a s~etrical groove into
wh~ ch a rim on t~Q pi6ton rod fits.
S This ~yrlnge is 8upplied in the retracted position a~
~hown. When expelling air the plunger rod is ~:topped by a ~houlder
abutting ~;aid ring, and t~en the rim cnaps int~ the groove. ~ow the
ring i:~ radially ret~ined in its seat~ 80 that ~he ring and/or the
rim mu~t be Rla8tically defor~able for allowing the latt~r to snap
into the former, which reguire~ a ~ubstantial force, and, moreo~er,
increa~e~ the ~riction ~etwo~n the ring and the ~Rat. so t~ere is a
risk that the user pu~h~s t~e pl~ton rod insuf~iciently inwards (i . e .
no coupl ~ ng w- ~ the ring), and when retr~cting the pi~ton rod , the
frictic~n between the ring and its s~at is so large that ~e ri~ is
1~ pull~d out from the groove, bearing in mind that both are sy~metri-
cally rounded. For a dependable aperation, Y~y narrow tolerance~
s~ould b~ ntain~, in practice, i6 hardly poasible or will lead to
8ub~ ntial c08t.
Thi~ is aggravated ~y 'che ~act t~at, when pressing the
pistcn ~nwardly, a vacuu~ ~; created and additional f~iction braking
~an~ are pr~sent, ~o that: the req-lired force is already large, and
pressing t~e rim ~nto said groove r~auire~; a ~;ubstantial additional
~orce.
According to th~ invention ~ rin~s of the various e~bodi-
23 DlQnt~ are mo~able without sub:~tantial friction, and in the ca~ that
an outwardly bi~c~ed r~ ng i8 us~d, thQ gr~ove i~ asymmetrical and t~e
pi~'cor~ rsa i~ made hollow at ~;o a- to ~aJce it~s wall fl~xible, wh~c~
fac~l~t~e t~e en~age~ent with ~aid grootJQ and prev~nt the
d~ongagement when ret~acting t:he piston rod.
j30
SUBSTI~U~ ~HEET
.
..
Claim 11 relates to a second embodiment which provides
an immediate improvement on the syringe according to the
above-mentioned prior ~etherlands patent application.
Claims 12..16 relate to an advantageous em~odiment of
25 the latching of the needle foot, while Claims 17..20 relate
to a special needle cap for s~lch a syringe.
Claims 21..27 relate to another embodiment in which the
ring is accommodated in the casing in a non-shiftable manner,
and, by co-operation with the piston/piston rod assembly when
30 shifting the latter, is rotated in such a manner that in the
terminal position thereof an abutment s~rface of the ring is
rotated so far that the assembly can be p-~shed into the
casing over the increased stroke length.
The invention will be fl~rther described hereinbelow with
35 reference to a drawing showing in:
Fig. 1 a diagrammatical section of a first embodiment
of the syringe according to the invention;
Figs. 2A..C partial diagrammatical sections of this
syringe;
W093/10~2 2 1 ~ 7 ~ PCT/NL92/~217
-- 3
Figs. 3A..D partial diagrammatical sections of the
terminal portion of a syringe ill~strating the latching and
coupling means of the needle foot and the piston;
Fig. 4 a diagrammatical section of the terminal portion
5 of a somewhat modified embodiment of the syringe ac~ording to
Figs. l and 2;
Fig. 5 a corresponding diagrammatical section of a
second embodiment of the syringe according to the invention;
Figs. 6A..C a somewhat modified embodiment of the
lO syringe according to Fig. 5 in various positions;
Figs. 7A..C partial diagrammatical sections of part
of a third embodiment of the syringe according to the
invention in three different positions;
Fig. 8 diagrammatical representations of a needle cap
l~ for such a syringe;
Fig. 9 an exploded perspective view of a fourth
embodiment of the syringe according to the invention;
Figs. lOA..J highly simplified schematic representations
of successsive operative conditions of the syringe of Fig. 9;
20 and
Figs. llA..D corresponding schematic representations of
a slightly modified embodiment of the syringe of Fig. 9.
Fig. 1 shows a first embodiment of the syringe according
to the invention. This comprises a generally cylindrical
25 casing l, having, at some distance from the open end 2, a
gripping ring 3 and at its other end a narrowed nose 4 which
adjoins the casing l via a genrally conical surface S.
From the open end 2 a needle foot 6 is pushed into the
casing l, to which a hollow needle 7 is fixedly attached,
30 the needle shiftably projec~ing outwards through a bushing 8
placed in the gradually narrowing nose 4. The needle foot 6
ab~ts the conical connecting surface 5 and is secured
against shifting in a way to ~e described hereinafter, in
order to ensure that in case of a longitudinal force being
3~ exerted on the needle 7, for instance in case of the piercing
of the stopper of a storage bottle of injection liquid or the
skin of a patient, the needle foot cannot he pressed inwards.
In assembling such a syringe all parts may be
consecutively slid into the casing l from the open end 2.
WO93/10~2 PCT/NL92/00217
212~574 4 ~
More particularly, the needle 7 may first be stuc~ in
thro~ugh the ~ushing 8 and then fixed in the needle foot 6
~for ins~ance with an adhesive), after which the needle foot
6 may be slid into the casing 1 with the needle 7 and the
S bushing 8. During its passage through the nose 4, the needle
7 is suitably guided in an axial direction so that d~ma.ge to
the needle is avoided (see also Figs. 3B and 3C to be
described hereinafter).
A~utments (not shown) ensure that the piston 9 cannot be
10 withdrawn from the casing 1 after insertion.
WO93/10&42 5 2 12 4 S 7 ~ PCT/NL92/~217
It will be obvious that such a syringe may also be
adapted for the use of separate needles intended to be
fitted from the outside, as shown and described for instance
in the abovementioned prior patent application so 00 487.
An assembly of a piston 9 and a piston rod 10 connected
therewith is also inserted into the casing 1, the piston rod
lo having at its free end a pressing surface 11 with-which
the piston rod 10 can be operated. The piston 9 has for
instance a sealing ring 12 which provides a liquid tight
seal to the inner wall of the casinq 1, and is further
provided with a conical surface 13 at the side directed
towards the needle foot 6. The needle foot 6 has a
corresponding conical surface 14, this in such a ~anner that
when the piston 9 is completely pressed in, the dead space
beco~es as s~all as possible.
Furthermore, means to be described hereinafter are
present to provide coupling between the piston 9 and the
needle foot 6 when the piston 9 is completely pressed in and
to simultaneously unlock the needle foot 6, this in such a
way that after providing said coupling and unlocking the
needle foot 6 can be drawn inwards into the casing 1 along
with the needle 7.
Near the open end of the casing 1 the casing is
pro~ided with a number of inwardly resilient tongues 15, as
~ay be seen ~ore clearly in Fig. 2. On the piston rod 10
there are formed two portions with a smaller diA~eter, which
forn two support surfaces 16,-17, the surface 17 with the
s~aller ~i~ eter being located on the piston side. In the
case shown here, vide also Fig. 2B, the piston rod 10 is
~ade cruciforJ, and these support surfaces are situated in
the ribs thereof. on the support surface 16 situated on the
outside there i~, in the initial situation, an inw~rdly
refiilient ring 18, for instance a split ring, although a
coil gpring may be used instead; this ring rests on the
3S support surface 16 with an inward tension. As shown in Fig.
2C, a s~all lug 19 ~ay be provided near the inward end of
the support ~urface 16 on the inner wall of the portion 2 to
retain the ring 18 against accidental shifting on this
support surface.
WO93/10842 212 ~ , 7 4 - 6 - PCT/NL92/00217
Fig. 2A shows the initial situatiOn, in which the rin~
18 is situated outside the tongues 15. When air is drawn in
and then driven out into a storage bottle, the piston rod
having passed the tongues 15 cannot be pressed further
inwards than the position shown in Fig. 1, the ring 18 then
abutting the abutment shoulder 20, as in this situation the
e~ternal diameter of the ring 18 is greater than t~e-
internal diameter of the container 1 at this shoulder 20.
The stroke length of the piston 9 is thereby limited to such
an extent that it cannot unlatch the needle foot 6 and
cannot be coupled with this needle foot 6. The tongues 15
now grip behind this ring, as shown in Fig. 1.
When the piston rod 10 is withdrawn again, in order to
draw in injection liquid, the tongues 15 retain the ring 18,
shifting it to the support surface 17, the di~meter of the
ring decreasing as a result of its inward resilience. This
causes the ring 18 to be liberated from the ends of the
tongues 15, 80 that the piston rod can be drawn out
uni~p~ded, the external diameter of the ring having now also
beco~e smaller than the internal diameter of the casing 1.
In the course of subsequent pressing inwards of the piston
rod 10 for the expulsion of injection liquid, the piston 9
can then be pressed through to the needle foot 6, in the
courge of which practically all the injection liquid can be
expelled as a result of the conical form of the surfaces 13
and 14, which is advantageous especially in the case of
expensive injection fluids.
As ~oon a8 the piston 9 reaches the needle foot 6, the
latter is unlatched and coupling between the two i~ brought
about, ~o that when the piston rod 10 is pulled outw~rds,
the needle foot is drawn along and the needle 7 co~es to lie
inside the ca~ing 1. The co~plete device can then be
di~po~ed of as such, while it is also possible to destroy
the néedle by pressing in the piston rod 10 once more, the
point of the needle, which is somewhat curved or so~ewhat
excentrically guided, abutting the end surface of the
bushing 8 or the conical surface 5, and the needle is bent
beyond use. In addition, the passsge in the bushing 8 is so
W093/10~2 7 212 ~ 5 7 ~ PCT/NL92/~217
narrow that the chance of the needle reentering this passage
is extremely small.
The means for latching the needle foot 6 in the casing
1 and for coupling the piston 9 to the needle foot 6 may be
provided in different ways. Fig. 3 shows examples of
embodiments thereof.
As shown in Fig. 3A, the end of the casing 1 is
provided with internal shoulders 21 which are distributed
along the circumference at an angle of, for instance, 120-,
the end portion 1' of the casing 1 being slightly narrowed
and elastically deformable. The needle foot 6 is slid in
from the open end 2 during assembly of the syringe, the
casing end 1' and possibly also the needle foot 6 being
deformed somewhat until the needle foot 6 snaps behind the
shoulders 21. Upon complete pressing inwards of the piston
9, the latter deforms the casing end 1' somewhat, the
shoulders 21 being moved back, while simultaneou~ly a knob
22 on the surface of the piston head forcing its way into a
correspondingly shaped recess 23 in the needle foot 6 and
b~inginq about a coupling therewith. The complete assembly
can then be withdrawn past the shoulders 21.
Figs. 3~ and 3C show a somewhat ~odified e~bodiment of
the needle foot 6 and the piston 9, the head 13 of the
pi~ton being shaped as a smooth cone as in the case of Fig.
- 25 1, and the needle foot 6 being provided with a
correspondingly conical surface 14. The needle foot 6 has
one or ~ore so~ewhat projecting hooks 24 which, as shown in
Fig. 3B, can protrude outwards in a transverse direction
when free in order to facilitate the forming thereof in a
~ingle operation. In the course of sliding the needle foot 6
into the casing 1, these hooks 24 bend inwards, so that they
lie flat against the inner wall of the casing 1. Upon
co~plete pressing inwards of the piston 9, the ends of these
hooks 24 engage a groove 25 between the piston head 13 and
its sealing ring 12 so that coupling can be brought about in
a simple way. m ere may, for instance, be three hooks 24
present, which must then be situated in the interspaces
between the lugs 21, as shown, the piston rod in this case
having three ribs.
WO93/10842 21 2 4 5 7 4 - 8 - PCI'/NL92/00217
Fig . 3C f urther shows that before introducing the
needle foot 6, the bushing 8 is placed onto the needle 7 to
guide the needle during passage through the wider nose 4, as
described ~ereinabove.
More particularly, as shown in Fig. 3D, the casing 1,
the needle foot 6, and the piston 9 are made with a somewhat
triangular cross-section, the piston rod 10 being made with
three ribs. The piston 9 and the needle foot 6 are then
guided non-rotatably in the casing 1. The lugs 21 are
situated on the sides of the triangular casing wall, whereas
the hooks 24 of the needle foot are situated opposite the
corners. Upon co~plete pressing inwards of the piston 9, the
lugs 21 are pushed away by the bevelled piston head 13, by
which action the foot 6 is freed, so that after engaging of
the hooks 24 with the piston 9, the needle foot 6 can be
drawn inwards together with the piston 9.
The advantage of this is that the position of the hooks
24 relative to the lugs 21 is unambiguously fixed. An
additional adv~ntage is that a syringe thus made cannot roll
about, and that due to the flattened surfaces the casing 1
can be brought closer to the skin during injection. It will
be obvious that these advantages mny algo be achieved u~inq
other non-circular cross-sections. All this is made pos~ible
by the fact that all parts may be for~ed by injection
moulding or suchlike out of plsstic material.
In the case of the eabodi~ent according to Figs. 1 and
2, it is possible that after removing a syringe from its
packaging, the piston rod is accidentally pressed into the
position shown in Fig. 1, 80 that after withdrawal of the
pi~ton for drawing in air, the ring 18 slides onto the
~upport surface 17, thus re~oving the stroke limitation. To
prevent thi~, the embodiJent according to Fig. 4 aay be
used, in which another surface 26 with an even greater
dia~eter, on which the ring 18 rests in the initial
situation, adjoins the support surface 16. The tongues 15
are now provided on their outer side with an abutment
surface 27, the ring 18 in the initial situation resting
against the abut~ent surface 27, so that pressing inwards of
the piston rod 10 is thereby prevented. Upon drawing
W093/l0842 _ 9 _ 2 12 ~ 3 ~ ~ PCT/NL92/~217
outwards of the piston rod, the ring 18 is retained by one
or more abutment surfaces 28 on the other side of the
tongues 15, so that the ring 18 is pressed onto the first
support surface 16, the diameter of the ring decreasing to
such an extent that it can slide away under the abutment 27
when the piston rod lo is pressed back in for the expulsion
of air, after which the operation continues as described
with reference to Figs. 1 and 2. The abutments 28 may for
instance be circumferentially staggered in relation to the
tongues lS. In the initial position, the ring 18 is then
locked between the abutments 27 and 28 and is freed from
b~th abutments during shifting towards the surface 16.
In the embodiments according to Figs. 1, 2 and 4 with
an inwardly resilient ring it is possible that during
protracted ætorage the ring 18 loses some of its resilience,
so that, upon being shifted, its external diameter does not
decrease sufficiently for the ring to fit closely on the
support surface 17, so that, eventually, the piston rod 10
cannot be pressed inwards sufficiently.
Fig. S shows a preffered embodiment in which this
drawback does not exist, and in which the operation f the
ring 18 cannot be influenced from the outside. The ring 18
is now seated in a widened seat 29 with a transverse
shoulder 30 in the en~ portion 2, the end surface 31 of the
ring 18 resting against this shoulder 30. The ring 18 h~s an
internal shoulder 32 adjoined by an diverging sloping
surface 33, which ends in a so~ewhat sloping end surface 34.
The piston rod 10 shown in the initial position has a
draw hook 35 ad~oined by a sloping surface 36 which i~
generally p~rallel to the internal surface 33 of the ring
18. The underlying portion of the piston rod has a central
aperture 37 which ~akes the intermediate piston rod portion
38 so~ewhat inwardly resilient.On the outside of the hook 35
there is a somewhat sloping shoulder 39 which is generally
parallel with the end ~urface 34 of the ring 18.
When, during expulsion of air after drawing it in, the
piston rod 10 is pressed in, the surface 36 slides over the
surf~ce 33, with elastic deformation of the portion 38,
un~il the hook 35 snaps behind the shoulder 32, the sloping
W093/1~2 2 12 4 5 7 4 - 1 o - PCT/NL92/00217
shoulder 39 preventing further pressing inwards of the
piston rod lO by abutting the end surface 34 and therefore
coupling of the piston g with the needle foot 6.
When the piston rod lO is drawn back out to draw in
injection liquid, the hook 35 takes with it the ring 18
which, after leaving the seat 29 will expand outwards, this
being enhanced by the further expansion of the briefl~
compressed piston rod portion 38. When subsequently the
piston rod lO is pressed inwards once more to expel the
liquid, the end surface 31 of the ring 18 abuts the head
~urface 20 of the casing portion 2. The ring 18 is shifted
with its sloping surface 33 past the sloping shoulder 39
towards the wider end portion 40 of the piston rod lO and is
then further widened. The stroke limitation is thus removed,
lS so that coupling between the piston 9 and the needle foot 6
can take place.
In this case also it is possible that the piston rod lO
is accidentally pressed inwards from the initial position,
and that the hook 35 is then engaged with the shoulder 32.
Fig. 6A ~hows a somewhat modified e~bodi~ent, there
being provided within the seat 29 between the hook 35 and
the ~houlder 39 a filler piece 41 which ~ay be connected to
the casing l by a flexible strip 42. The filler piece 4$
prevonts pressing inwards of the piston rod lO, but, when
drawing outw~rds the latter for the first ti~e, is drawn
outwards by the hook 35, because a transverse surface 43
thereof engages the ~raw hook 35 of the piston rod lO, after
which tbe filler piece can f~ll away or stay attached to the
~trip 42~ Instead of a filler piece a divided ring ~ay be
u~d, which, like the ring 18, can be slid on over the
pi~ton rod end~
Figs. 6B and 6C show two extre~e inward end positions
of the piston rod, viz. after the expulsion of air and
liquid, respectively, the filler piece 41 being already
re~oved,-so that these positions apply equally to the
e~bodiment according to Fig. 5. In the position of Fig. 6C,
the shoulder 30 of the piston rod lO abuts the ring 18 which
i5 still situated in the seat 29, which limits the inward
~troke length, while in the position of Fig. 6C the ring 18
W093/1~2 ~ 2 ~i 3 7 ~ PCT/NL92/~217
is shifted onto the piston rod portion 40 and is retained by
the end surface 20' o~ the casing end 2; the stroke length
is then no longer limited.
Fig. 7 shows yet another smbodiment, the stroke
limiting means being situated near the piston 9. The piston
further has two pairs of hooks 44 and 45, the hooks 44 at
least being outwardly resilient. The hooks 44 each p~e at
their piston sides a sloping surface 46, and on the other
side a straight head surface 47. The piston rod 10 has a
head surface 46, which, in the initial position illustrated
in Fig. 7A, rests against the rear surface of the piston 9,
while a narrqwed portion 49 is provided with a bevel 50,
which engages the sloping surface 46 of the hook i4. At a
certain distance of the bevel 50 the narrowed portion 49
adjoins a transverse surface 51, which in this position is
close to or against the end surface of the second hook 45.
In this initial position a ring 18 rests on the external
surface of the hooks 44, the ring 18 further fitting with
friction against the internal wall of the casing 1. The
hooks 44 are then locked against bending outwards, so that
the piston rod is fixedly coupled to the piston 9 for
pressing as well as drawing forces.
When air is drawn in, the ring 18 is carried along by
the piston 9. However, as soon as the piston rod 10 is
pressed back in for the expulsion of air, the ring 18 will
be held back by friction with the casing 1 and, as shown in
Fig. 7B, will be ~hifted towards the hooks 45. The pressing
forc~s are still transferred to the piston 9 by the head
~urfaces 48 and/or 51 of the piston rod 10.
When, as shown in Fig. 7C, liquid is drawn in, a
pulling force is ~xerted on the piston rod 10, the bevelled
surface 50 of the narrowed portion of the pi~ton rod 49
being allowed to slide overlthe corresponding sloping
surfaces 46 of the hooks 44, these hooks then being allowed
to bend outwards, after which the end portion of the piston
rod 10 co~es to lie between the hooks 44 and 46, the hooks
46 being locked against outward move~ent by the ring 18.
As shown in Fig. 7C, the actual length of the piston
rod is now increased by the length of the hooks 44, so that
2 ~ 2 4 ~ 7 4 - l2 - PCT/NL92/00217
upon subseguent pressing inwards of the piston rod for the
expulsion of liquid the piston 9 can be pressed inwards over
a correspondingly greater distance, thiC distance being
sufficient to bring about coupling with the needle foot.
Additional abutments (not shown) on the piston rod lO
and the casing l may limit the inward shifting of the piston
rod to a distance at which in the position of ~ig. 7
coupling between the piston 9 and the needle foot 6 cannot
take place. In this situation, the syringe can readily be
lO packaged.
Although a syringe according to Figs. l..7 may be
packaged in a generally sterile condition, it is necessary
for drawing in liq1lid from a liquid bottle first to fill the
syringe internally with air. If this is ambient air, there
15 is a risk that this air, which is pressed into the storage
bottle, may pollute its contents and those of the syringe.
In order to prevent this, a cap 52 may be provided on the
needle 7, as shown in Fig. 8A, which is loosely fitted onto
the end 4 of the casing l and is provided with a filter 53
20 adapted to block out dust from the air. To stick the needle
into a liquid container the cap will have to be removed. It
is also possible, as shown in Fig. 8B, to provide this cap
with a collapsible wall 54, it being possible then to stick
the needle 7 through the end thereof before sticking the
25 needle through the stopper of a liquid container. The cap 52
is then folded li~e an accordion, and can then be left
around the needle 7.
Fig. 9 shows yet another embodiment of the open end of a
syringe according to the inve~tion, and of an assembly of a
30 piston 9 and a piston rod lO to be inserted in the syringe,
wherein without additional means undesired shifting of the
piston rod can be prevented. In this embodiment the ring 18
is accommodated in the support s~rface 29 in the end part of
the casing l, so that the ring can rotate b~t cannot slide,
35 and is kept in position by means of one or more shoulders 55
which can move o~ltwards resiliently when inserting the ring,
but prevent later removal of.the ring.
In the embodiment shown the piston rod lO is provided
with threé first ribs 56. It is also possible to provide the
- 2121~74
WO93~10~2 PCT/NL92/~217
- 13 -
piston rod with two ribs lying in the same plane, whereas it
is also possible to work with only one rib. However, the use
of two or more ribs 56 is preferred.
Near the ol~ter end of the piston rod 10 each of these
5 ribs 56 changes into a shorter second rib 57, parallel to and
staggered over a certain angle distance in respect of the
corresponding first rib 56, whereby between each first rib 56
and the corresponding second rib 57 an inclined connecting
piece 58 is situated of which the upper rim 59 is somewhat
10 chamfered. Near the pressing surface 11 at the end of the
piston rod 10, the ribs 57 are crosswise wider, thus forming
an abutting shoulder 60.
In the ring 18 inwards facing lugs 61a, b and c are
formed, whereby the first lug 61a can ~e fixed, whereas the
15 two lugs 61b and 61c are each situated on a c~t-out resilient
tongue 62. These tongues project so far inwards that an
outward movement thereof is possible within the support
surface 29. The width of the space between two lugs 61
corresponds approximately with the thickness of a rib 56 or
20 57.
Fig. 9 shows only one set of lugs 61, but it may be
advantageous to provide as many sets of lugs as there are
ribs 56 and 57.
F~rther the ring 18 has in the outwards facing rim 63 a
25 notch 64 for each sho~llder 60 of the piston rod 10, the depth
of which in the axial direction to the bottom 65 corresponds
with the stroke increase necessary to effect the coupling of
the pistion with the needle foot, which is obtained in the
embodiment described in the foregoing by the slidability of
30 the ring 18.
Before the assembly of the syringe and before the
sealing ring 12 is placed on the piston 9, the ring 18 is
slid on the piston rod 10 in such a way that a second rib 57
is accommodated in the interspace between the corresponding
35 lugs 61a en 61b. Thereafter the sealing ring 12 is placed and
the whole assembly can be pressed into the casing 1, whereby,
finally, the ring grips behind the resilient shoulders 55.
When the ring 18 is thus fixed in the support surface of the
casing 1, the l~gs 61 prevent withdrawal of the piston 9 from
W093/10842 2 12 ~ ~ 7 4 PCT/NL92/~217
- 14 -
the casing 1.
The operation of this embodiment will now be explained
by reference to the highly simplified diagrams of Fig. 10.
Therein only a part of the ribs 56 and 57 of the piston rod
5 10 is illustrated, whereas only a part of the ring 18 with
the l~gs 61 and the notch 64 is shown.
Fig. lOA shows the starting position in which the piston
is wholly pushed in. In this condition a packed syringe is
sold. The second rib 57 is then situated between the lugs 61a
10 en 61b, whereas the shoulder 60 ab~lts on the rim 63 of the
ring 18.
When, as shown in Fig. lOB, the piston rod 10 i-s drawn
outwards for the first time in order to draw air in, the
first lug 61a moves against the connecting piece 58 whereby
15 the ring will turn, as is indicated with an arrow. The second
lug 61b then follows the connecting piece on the other side,
and finally the position of Fig. lOC is reached, wherein the
rib 56 stays between these lugs 61a and 61b when the piston
rod is pulled out further.
When the piston rod 10 is pushed in again to eject air,
the position of Fig. lOD is passed, and then the lug 61b is
pressed outwards over the chamfered rim 59 of the connecting
piece 58, and can slide over the connecting piece 58 as is
indicated with a dotted arrow, the rib 57, as is shown in
25-Fig. lOE, arriving between the second and the third lug 61
and 61c respectively. In the position of Fig. lOE, the
shoulder 60 abuts against the rim 63 of the ring i8.
In order to prevent that the ring turns when the lug 61b
slides over the chamfered rim 59, a small guiding plate 66
30 can be arranged parallel to the rib 56 b~t at such a distance
from the inclined connecting piece 58 that between them a
passag~ remains for passing a lug 61, as clearly appears from
Fig. lOB. During the pushing in of the piston rod 10 in the
~icinity of the position according to Fig. lOD, this g~iding
35 plate 66 arrives between the lugs 61b and 61c, thus preventing
the t~rning of the ring 18, whereas at the same time the lug
61b is ambig~ously gl~ided over the chamfered side 59.
When the piston rod 10 is withdrawn again from the
position of Fig. lOE in order to draw in injection fluid, the
W093/10842 212 ~ j ~ 1 PCT/NL92/~217
- 15 -
position of Fig. lOF is reached, the ring 18 then being
turned in the same way as in the positi~n of Fig. lOB. When
the piston rod 10 is withdrawn further, the rib 56 moves
between the lugs 61b and 61c as is shown in Fig. lOG.
At the rotation of the ring in the position of Fig. lOF,
the notch 64 has now turned in such a way that it becomes
axially aligned with the shoulder 60 of the rib 5?
When the piston rod is pushed inwards again from the
position of Fig. lOG in order to eject the injection fluid,
10 the positicn of Fig. lOH is passed again, whereby the lug 61c
slides over the chamfered rim 59 of the connecting piece 58.
As shown in Fig. lOJ, the lug 61 will finally abut in the
notch 64 against the bottom 65 thereof, in which position the
coupling of the piston 9 with the needle foot can be effected.
15 The increase of the stroke length thus obtained is indicated
at d.
After the coupling of the needle foot, said needle foot
can be drawn inwards as in the preceding embodiments, where-
after, if necessary, the needle can be destroyed by pushing
20 the piston rod 10 inwards again.
Fig. 11 shows, in even more simplified diagrams, a some-
what modified embodiment in positions which correspond with
those of Fi~s. lOA, 8, C, and D. In this modified embodiment,
the or each rib 56 is widened at its upper side, the lateral
25 edge of this widened part being aligned with the edge of the
corresponding rib 57. The chamfered rim 59 is now situated at
the beginning of this widened part near the inclined
connecting piece 58. The operation of this embodiment mainly
corresponds with the working as shown in Fig. 10.
Fig. llA shows the starting position which is equal to
the one of Fig. lOA. Pig. llB shows the position at the
beginning of the rotation of the ring 18 because the firs~
lug 61a is pressed away along the inclined edge 58, the
second lug 61b now sliding over the chamfer 59 onto the
35 widened part of the rib, in which position it remains further
on as is shown in Fig. llC. In the position of Fig. llD,
which corresponds with the one of Fig. lOD, the lug 61b
slides off the widened rib 56 and then arrives behind the
inclined édge 58. In this case the small guiding plate 66 is
W093/l0~2 212 4 5 7 4 PCT/NL92/~217
- 16 -
no more req~ired.
It can be pointed out that, in the embodiments according
to Figs. 10 and 11, the third lug 61c is not strictly
necessary, but it provides an additional safeguard against
5 undesired turning back of the ring 18.
In the syringe according to Fig. 9 the ring 18 will,
under all circumstances, turn with respect to the piston rod
10, also when said piston rod wo~ld itself turn with respect
to the casing 1. In the embodiment shown in Fig. 9 the casing
10 has a triangular shape so that turning the piston 9 is not
possible, but also with a cylindrical casing, when such
rotation is possible, this has no influence on the
interaction between the ring 18 and the piston rod 10.
