CA2124574A1

CA2124574A1 - Injection syringe

Info

Publication number: CA2124574A1
Application number: CA 2124574
Authority: CA
Inventors: Abraham Van Den Haak
Original assignee: Individual
Current assignee: Advanced Protective Injection Systems Medical BV
Priority date: 1991-11-28
Filing date: 1992-11-27
Publication date: 1993-06-10
Also published as: AU3267993A; BR9206841A; WO1993010842A1; NL9101994A; JPH07501960A; EP0683682A1

Abstract

A syringe, comprising a casing (1) with a piston/piston rod assembly (9, 10) slidable therein and a needle foot (6) latched to a first end of the casing, means being provided to couple the piston with the needle foot and to unlatch the needle foot in an inner extreme position of this assembly in order to be able to withdraw the needle foot with the piston into the casing and thereby to shield off the needle (7) fixed to the needle foot and, as the case may be, to destroy this needle, stroke limiting means (15, 18) being provided which are adapted to limit the stroke length in such a way that the piston remains at a predetermined distance from the needle foot when the piston is pushed inward for the first time to eject the air, and after the withdrawal of the piston for drawing in the injection fluid, to increase the stroke length in such a way that the piston can be coupled with the needle foot when the piston is thereafter pushed inwards again for the ejection of the injection fluid. The means to limit the stroke comprise a ring (18) which, is either slidable by interaction with this assembly, over a predetermined distance with respect to this assembly or to the casing after the assembly has been drawn outwards at least once, or is rotatable and is provided with abutments staggered to each other over the predetermined distance, so that, when the assembly slides, this ring is turned in such a way that, finally, the assembly can be pushed inwards up to the deepest abutment.

Description

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.
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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 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 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 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 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 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.

Claims

1. An injection syringe, comprising - a cylindrical casing (1) having at its front end a seat (4) and an open rear end (2);
- a needle foot (6) latched in said seat (4);
- an assembly of a piston (9) and a piston rod (10) shiftable in said casing between an outward and a first inward position;
- mutually engageable means (22, 33, 24) for coupling said piston (9) and needle foot (6) and unlatching the latter (6) from its seat (4) as soon as said piston (9) has been pushed into said first inward position;
- said syringe being supplied with said assembly (9, 10) in an initial inward position differing from said first position;
and being adapted to perform the following steps.
? a first outward stroke for sucking in air, ? a first inward stroke for expelling the air, ? a second outward stroke for sucking in injection fluid, ? a second inward stroke for expelling said fluid for injection, and ? a third outward stoke for withdrawing said needle foot (6) with said casing (1) after coupling said foot with said assembly (9, 10);
means being provided for restricting the stroke length of said assembly (9, 10) during the first inward stroke to a second inward position in which said coupling and unlatching means (22, 23, 24) are not engaged, said means being movable during said second outward stroke into a position in which the stroke length restriction is cancelled, so that said assembly can be moved during the second inward stroke into the first posi-tion, said stroke length restriction means comprising a ring (18) surrounding said assembly (9, 10) and having at least two different stop positions in respect of said assembly (9, 10) and casing (1), said ring (18), assembly (9, 10 and casing (1) having co-operating elements (16, 17, 26, 20; 30, 26, 32, 35;
44...51;) (16..26; 30..36; 44..51; 55..63) forming stop means for restricting the displacement of said piston (10) to said first and second positions respectively and acting as driving means for moving said ring (18), said ring (18) being movable in respect of said assembly (9, 10) and casing (1) with low friction so as to enable an unimpeded movement of said ring (18) by said driving means.

2. The syringe of claim 1, in which said ring (18) prevents, in the initial position of said assembly (9, 10), an inward displacement of the latter before said first outward stroke.

3. The syringe according to Claim 2, c h a r a c t e r i s e d in that on the side of the piston the first support surface (16) is delimited by one or more somewhat protruding ribs or lugs (19) which prevent the accidental shifting towards the second support surface (17) of the ring (18).

4. The syringe according to Claim 2 or 3, c h a r a c t e r i s e d in that at its far side relative to the second support surface (17) the first support surface (16) adjoins a third support surface (26) with a greater diameter than the first (16), the ring (18) in the initial position being situated on this third support surface (26) and then abutting one or more abutments (27) situated on the easing (1,2) or the tongues (15) which prevent the assembly (9,10) being pressed inwards, and in that on the easing (1,2) or the tongues (15) on the other side of the ring (18) one or more additional abutments (28) are present which upon outward withdrawal of the assembly (9,10) cause the ring (18) to be transferred to the first support surface (16).

5. The syringe according to Claim 1, c h a r a c t e r i s e d in that:
- the ring (18) is an outwardly expandable ring which is shiftable in a widened end portion (29) of the casing end (12) and is restrained therein against inward shifting, the inner side of the ring being provided with a recessed shoulder (32) which adjoins a diverging sloping surface (33) directed towards the far side relative to the needle end of the casing and opening outwards, terminating in an outward end surface (34), - the piston rod (10) is provided with a draw hook (35) which, in the initial position, is situated outside the ring (18) and upon inward shifting of the assembly (9,10) is slidable over the sloping surface (33) of the ring, and finally grips behind the recessed shoulder (32) of the ring (18), a sloping shoulder (39) of the piston rod (10) then abutting the end surface (34) of the ring (18) in order to limit the inwards stroke length of the assembly (9,10), whereas, upon subsequent withdrawal of the assembly (9,10), the ring (18) is drawn out of the widened casing portion (29) and, after leaving this portion, is allowed to expand outwards, and - the piston rod (10) beyond this terminal shoulder (39) has such a diameter that when, upon renewed pressing inwards of the assembly (9,10), the end (31) of the ring (18) which is situated at the piston side thereof in the expanded condition abuts the terminal surface (20) of the widened casing portion (29), the ring (18) with its sloping inner surface (33) is shifted along past the sloping shoulder (39), thus removing the limitation of the stroke length.

6. The syringe according to Claim 5, c h a r a c t e r i s e d in that the portion (38) within the draw hook (35) is made inwardly resilient.

7. The syringe according to Claim 5 or 6, c h a r a c t e r i s e d in that on the outside of the ring (18) inside the widened end portion (29) a filler piece (4) is provided which at least approximately fills up the intermediate space between the end surface (34) of the ring (18) and the terminal shoulder (30) of the piston rod (10), this in such a manner that inward shifting of the assembly (9,10) from the initial position is prevented whereas upon outward withdrawal of the assembly (9,10) from the initial position the filler piece (4) is withdrawn from the casing (1,2) and is liberated therefrom.

8. The syringe according to any one of Claims 1 .. 7, c h a r a c t e r i s e d in that the ring (18) is a split ring.

9. The syringe according to any one of Claims 1 .. 7, c h a r a c t e r i s e d in that the ring (18) is a coiled spring.

10. The syringe according to any one of Claims 1 .. 9, c h a r a c t e r i s e d in that the casing (1) is provided at its needle end with a nose (4) in which a bushing (8) provided with a guide bore for the needle fits.

11. The syringe according to Claim 1, in which the stroke limiting means are formed by two pairs of resilient locking lugs and two collar edges on the piston rod or vice versa, the collar edges being bevelled at their piston side, the distance between these collar rims corresponding to the predetermined distance for the limited stroke length, and the piston rod in the initial position at least approximately resting against the piston, the piston rod being provided with an abutment limiting its outward stroke, c h a r a c t e r i s e d in that the inner side of the ring (18) is shiftable around the outside of the locking lugs (44,45) while the outer side of this ring (18) fits with friction inside the casing (1), the width of the inner surface of the ring (18) which contacts the locking lugs (44,45) being no greater than the axial length of a locking lug (44,45), all this in such a manner that the locking lug (44,45) engaged by the ring is locked by the ring (18).

12. The syringe according to any one of Claims 1 ..
11, wherein the needle foot is restrained against inward shifting by one or more abutment edges of the casing, c h a r a c t e r i s e d in that the container wall (1') 1 and/or the piston (9) is deformable in such a way that, upon completed pressing inwards of the piston (g) along the extended stroke length the abutment edges (21) are released from the needle foot (6).

13. The syringe according to Claim 11, c h a r a c t e r i s e d in that the needle foot (6) is provided with one or more protruding hooks (24) which are adapted to grip elastically behind an edge (25) of the piston (9) in order to couple the piston (9) with the needle foot (6) when the piston (9) has been completely pressed inwards.

14. The syringe according to Claim 13, c h a r a c t e r i s e d in that the container (1), the needle foot (6) and the piston (9) have a non-circular, and in particular a rounded-triangular cross-section, the lugs (21) being situated at the wall portions with the smallest radius, and the hooks (24) of the needle foot (63 being situated at the portions thereof with the greatest radius.

15. The syringe according to any one of Claims 1 14, c h a r a c t e r i s e d in that the piston (9) and the needle foot (6) are provided with conical surfaces (13,14) of at least approximately the same shape, which upon complete pressing inwards of the piston (9) at least approximately interfit.

16. The syringe according to any one of Claims 12 ..
15, c h a r a c t e r i 8 e d in that the casing (1) is provided, at its needle end, with an inwardly directed support surface (5) against which the needle foot (6) comes to rest upon being shifted into the casing from the other end in order to lock the needle foot (6) between this support surface (3) and the abutment edges (21).

17. The syringe according to any one of Claims 1 ..
10, c h a r a c t e r i s e d in that on the outside of the casing (1) a needle cap (52) is provided which surrounds a needle (7) projecting from the needle foot (6) which cap (52) is filled with sterile air and is adapted allow this sterile air to be drawn in to upon withdrawal of the assembly (9,10) for the first time.

18. The syringe according to Claim 17, c h a r a c t e r i s e d in that the needle cap (52) is provided with a suction filter (53).

19. The syringe according to Claim 17 or 18, c h a r a c t e r i s e d in that the wall (54) of the needle cap (52) is collapsible upon drawing in of air.

20. The syringe according to any one of Claims 13 .. 19, c h a r a c t e r i s e d in that the needle cap (52) is accordion shaped, and in that its closed end may be penetrated by the point of the needle in order to allow the cap (52) to be rearwardly compressed so as to uncover the needle (7).

21. A syringe comprising a casing with a piston/piston rod assembly slidable therein and a needle foot latched at a first end of the casing, means being present to couple, in the inner extreme position of the assembly, the piston with the needle foot, and to unlatch the needle foot in order to enable the needle foot to be drawn into the casing with the piston and thereby to shield off and possibly destroy a needle coupled with the needle foot, stroke limiting means being provided which are adapted to limit the stroke length upon pushing inwards the piston for the first time for the expulsion of air in such a way that the piston remains at a predetermined distance of the needle foot, and to increase the stroke length after withdrawal of the piston for drawing in injection fluid in such a way that upon repeated pushing inwards of the piston for the expulsion of the injection fluid, the piston will be coupled with the needle foot, c h a r a c t e r i s e d in that the stroke limiting means comprise a ring (18) rotatative but non-shiftable, provided with a first and second abutting surface (63, 65) and which are axially staggered to each other, the distance between which corresponds at least approximately to the predetermined distance to be obtained between the piston (9) and the needle foot (6) at the limited stroke length, in which ring (18) the piston rod (10) is shiftable, which ring (18), by interaction with the piston rod (10) after the latter's second withdrawal, is rotated in such a way that an abutment (60) on the piston rod (10) comes into contact with the second abutment surface (65) of the piston rod (10) when the piston rod is pushed inwards again so that the piston (9) can be coupled to the needle foot (6).

22. The syringe according to Claim 21, c h a r a c t e r i s e d in that the piston rod (10) is provided with one or more ribs (56) each, near the free end (11) of the piston rod (10), changing into a parallel second rib (57) staggered circumferentially to the first rib, between which ribs (56, 57) a sloping connecting piece (58) is situated, in that the ring (18) is provided with one or more sets of at least two inwardly directed lugs (61a, 61b, 61c) between which passages are situated for corresponding ribs (56, 57) of the piston rod (10), the second and, as the case may be, the third lug (61b, 61c) of a set being adapted to move slightly outwards elastically, which lugs (61), at drawing out of the piston rod (10), can slide alternately along the sloping connecting piece (58) in order to cause the ring (18) to rotate accordingly, and in that at the inwards pushing of the piston rod (10) the second and, as the case may be, the third lug (61b, 61c), can move away elastically and can slide over the sloping connecting piece without causing the ring (18) to rotate.

23. The syringe according to Claim 22, c h a r a c t e r i s e d in that the second and, as the case may be, the third lug (61b, 61c) of each set and/or the sloping connecting piece (58) are provided with a chamfer (59) which facilitates the sliding over.

24. The syringe according to Claims 21 or 23, c h a r a c t e r i s e d in-that the second and, as the case may be, the third lug (61b, 61c) of each set is fixed on a resilient tongue (62) formed in the ring (18).

25. The syringe according to any one of the Claims 21..24, c h a r a c t e r i s e d in that next to at least one of the first ribs (56) of the piston rod (10) a small guiding plate (66) is provided which is directed parallel to the respective rib (56) and at a distance thereof which is approximately equal to the width of the second and, as the case may be, the third lug (61b, 61c) of a set, and which ends at a distance of the sloping connecting piece (58) which is at least equal to the width of these legs, which guiding plate (66), at the withdrawal of the piston rod (10), prevents rotation of the ring (18).

26. The syringe according to one of the Claims 22..25, c h a r a c t e r i s e d in that the or each first rib (56) in the part joining the sloping connecting piece (58) is so much wider than the second rib (57) that the second and, as the case may be, the third lug (61b, 61c) remain resting on this widening in their outwardly bent position when drawing outwards the piston rod (10).

27. The syringe according to Claim 26, c h a r a c t e r i s e d in that the second and, as the case may be, the third lug (61b, 61c) and/or the or each first rib (56) are provided with a chamfer which facilitates the sliding of a lug onto this widening.