WO1993010842A1

WO1993010842A1 - Injection syringe

Info

Publication number: WO1993010842A1
Application number: PCT/NL1992/000217
Authority: WO
Inventors: Abraham Van Den Haak
Original assignee: Advanced Protective Injection Systems Medical B.V.
Priority date: 1991-11-28
Filing date: 1992-11-27
Publication date: 1993-06-10
Also published as: AU3267993A; NL9101994A; JPH07501960A; CA2124574A1; BR9206841A; 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

Injection syringe

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 assembly 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 much space. It is likewise a disadvantage that in case of incorrect operation of this syringe, 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 meant 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, which can be prepacked with the assembly in its inwardly shifted position and which can be manufactured very cheaply. To that end, the syringe according to the invention is characterised by the features enumerated in the characterising portion of Claim 1.

The increase of the stroke of the assembly then takes 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 second time.

A first embodiment of the syringe according to the invention has the additional features enumerated in Claim 2, whereas Claims 3 and 4 enumerate further advantageous characteristics thereof which prevent shifting of the ring prematurely.

Claims 5, 6 and 7 relate to a somewhat modified embodiment, in which the ring is outwardly expandable, and the functioning thereof 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 invention.

Claim 11 relates to a second embodiment which provides an immediate improvement on the syringe according to the above-mentioned prior Netherlands patent application.

Claims 12..16 relate to an advantageous embodiment of the latching of the needle foot, while Claims 17..20 relate to a special needle cap for such a syringe.

Claims 21..27 relate to another embodiment in which the ring is accommodated in the casing in a non-shif able manner , and, by co-operation with the piston/piston rod assembly when shifting the latter, is rotated in such a manner that in the terminal position thereof an abutment surface of the ring is rotated so far that the assembly can be pushed into the casing over the increased stroke length.

The invention will be further described hereinbelow with 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; Figs. 3A..D partial diagrammatical sections of the terminal portion of a syringe illustrating the latching and coupling means of the needle foot and the piston;

Fig. 4 a diagrammatical section of the terminal portion of a somewhat modified embodiment of the syringe according to Figs. 1 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 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 for such a syringe;

Fig. 9 an exploded perspective view of a fourth embodiment of the syringe according to the invention;

Figs. 10A..J highly simplified schematic representations of successsive operative conditions of the syringe of Fig. 9; and

Figs. 11A..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 casing 1, 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 1 via a genrally conical surface 5.

From the open end 2 a needle foot 6 is pushed into the casing 1, to which a hollow needle 7 is fixedly attached, the needle shiftably projecting outwards through a bushing 8 placed in the gradually narrowing nose 4. The needle foot 6 abuts the conical connecting surface 5 and is secured against shifting in a way to be described hereinafter, in order to ensure that in case of a longitudinal force being 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 be pressed inwards.

In assembling such a syringe all parts may be consecutively slid into the casing 1 from the open end 2. More particularly, the needle 7 may first be stuck in through the bushing 8 and then fixed in the needle foot 6 (for instance with an adhesive), after which the needle foot

6 may be slid into the casing 1 with the needle 7 and the bushing 8. During its passage through the nose 4, the needle

7 is suitably guided in an axial direction so that damage to the needle is avoided (see also Figs. 3B and 3C to be described hereinafter) .

Abutments (not shown) ensure that the piston ^'9 cannot be withdrawn from the casing 1 after insertion.

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 90 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 10 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 casing 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 manner that when the piston 9 is completely pressed in, the dead space becomes as small 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 provided with a number of inwardly resilient tongues 15, as may be seen more clearly in Fig. 2. On the piston rod 10 there are formed two portions with a smaller diameter, which form two support surfaces 16,17, the surface 17 with the smaller diameter being located on the piston side. In the case shown here, vide also Fig. 2B, the piston rod 10 is made cruciform, and these support surfaces are situated in the ribs thereof. On the support surface 16 situated on the outside there is, in the initial situation, an inwardly resilient ring 18, for instance a split ring, although a coil spring may be used instead; this ring rests on the support surface 16 with an inward tension. As shown in Fig. 2C, a small lug 19 may be provided near the inward end of the support surface 16 on the inner wall of the portion 2 to retain the ring 18 against accidental shifting on this support surface. Fig. 2A shows the initial situation, in which the ring 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 external diameter of the ring 18 is greater than the 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 diameter 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, so that the piston rod can be drawn out unimpeded, the external diameter of the ring having now also become 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 course 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 soon as the piston 9 reaches the needle foot 6, the latter is unlatched and coupling between the two is brought about, so that when the piston rod 10 is pulled outwards, the needle foot is drawn along and the needle 7 comes to lie inside the casing 1. The complete device can then be disposed of as such, while it is also possible to destroy the needle by pressing in the piston rod 10 once more, the point of the needle, which is somewhat curved or somewhat 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 passage in the bushing 8 is so 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 simultaneously 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 bringing about a coupling therewith. The complete assembly can then be withdrawn past the shoulders 21.

Figs. 3B and 3C show a somewhat modified embodiment of the needle foot 6 and the piston 9, the head 13 of the piston being shaped as a smooth cone as in the case of Fig. 1, and the needle foot 6 being provided with a correspondingly conical surface 14. The needle foot 6 has one or more somewhat 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 single 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 complete 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. There 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. Fig. 3C further 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 hereinabove. 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 complete 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 advantage 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 may also be achieved using other non-circular cross-sections. All this is made possible by the fact that all parts may be formed by injection moulding or suchlike out of plastic material.

In the case of the embodiment 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, so that after withdrawal of the piston for drawing in air, the ring 18 slides onto the support surface 17, thus removing the stroke limitation. To prevent this, the embodiment according to Fig. 4 may be used, in which another surface 26 with an even greater diameter, 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 abutment surface 27, so that pressing inwards of the piston rod 10 is thereby prevented. Upon drawing 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 10 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 15. In the initial position, the ring 18 is then locked between the abutments 27 and 28 and is freed from both 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 storage 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. 5 shows a preffered embodiment in which this drawback does not exist, and in which the operation forthe 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 end portion 2, the end surface 31 of the ring 18 resting against this shoulder 30. The ring 18 has an internal shoulder 32 adjoined by an diverging sloping surface 33, which ends in a somewhat sloping end surface 34.

The piston rod 10 shown in the initial position has a draw hook 35 adjoined by a sloping surface 36 which is generally parallel to the internal surface 33 of the ring 18. The underlying portion of the piston rod has a central aperture 37 which makes the intermediate piston rod portion 38 somewhat inwardly resilient.On the outside of the hook 35 there is a somewhat sloping shoulder 39 which is generally parallel with the end surface 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 surface 33, with elastic deformation of the portion 38, until the hook 35 snaps behind the shoulder 32, the sloping shoulder 39 preventing further pressing inwards of the piston rod 10 by abutting the end surface 34 and therefore coupling of the piston 9 with the needle foot 6.

When the piston rod 10 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 briefly compressed piston rod portion 38. When subsequently the piston rod 10 is pressed inwards once more to expel the liquid, the end surface 31 of the ring 18 abuts the head surface 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 10 and is then further widened. The stroke limitation is thus removed, 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 10 is accidentally pressed inwards from the initial position, and that the hook 35 is then engaged with the shoulder 32. Fig. 6A shows a somewhat modified embodiment, there being provided within the seat 29 between the hook 35 and the shoulder 39 a filler piece 41 which may be connected to the casing 1 by a flexible strip 42. The filler piece 41 prevents pressing inwards of the piston rod 10, but, when drawing outwards the latter for the first time, is drawn outwards by the hook 35, because a transverse surface 43 thereof engages the draw hook 35 of the piston rod 10, after which the filler piece can fall away or stay attached to the strip 42. Instead of a filler piece a divided ring may be used, which, like the ring 18, can be slid on over the piston rod end.

Figs. 6B and 6C show two extreme inward end positions of the piston rod, viz. after the expulsion of air and liquid, respectively, the filler piece 41 being already removed, so that these positions apply equally to the embodiment according to Fig. 5. In the position of Fig. 6C, the shoulder 30 of the piston rod 10 abuts the ring 18 which is still situated in the seat 29, which limits the inward stroke length, while in the position of Fig. 6C the ring 18 e p s on r por on an s re a ne y the end surface 20' of the casing end 2; the stroke length is then no longer limited.

Fig. 7 shows yet another embodiment, 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 have 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 narrowed portion 49 is provided with a bevel 50, which engages the sloping surface 46 of the hook 44. 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 shifted towards the hooks 45. The pressing forces are still transferred to the piston 9 by the head surfaces 48 and/or 51 of the piston rod 10. When, as shown in Fig. 7C, liquid is drawn in, a pulling force is exerted on the piston rod 10, the bevelled surface 50 of the narrowed portion of the piston rod 49 being allowed to slide over the 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 comes to lie between the hooks 44 and 46, the hooks 46 being locked against outward movement 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 upon subsequent pressing inwards of the piston rod for the expulsion of liquid the piston 9 can be pressed inwards over a correspondingly greater distance, this distance being sufficient to bring about coupling with the needle foot. Additional abutments (not shown) on the piston rod 10 and the casing 1 may limit the inward shifting of the piston rod to a distance at which in the. position of Fig.. 7 coupling between the piston 9 and the needle foot 6 cannot take place. In this situation, the syringe can readily be packaged.

Although a syringe according to Figs. 1..7 may be packaged in a generally sterile condition, it is necessary for drawing in liquid from a liquid bottle first to fill the syringe internally with air. If this is ambient air, there 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 1 and is provided with a filter 53 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 needle through the stopper of a liquid container. The cap 52 is then folded like 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 invention, and of an assembly of a piston 9 and a piston rod 10 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 surface 29 in the end part of the casing 1, so that the ring can rotate but cannot slide, and is kept in position by means of one or more shoulders 55 which can move outwards resiliently when inserting the ring, but prevent later removal of .the ring.

In the embodiment shown the piston rod 10 is provided with three first ribs 56. It is also possible to provide the 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 outer 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 be fixed, whereas the

15 two lugs 61b and 61c are each situated on a cut-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.

Further the ring 18 has in the outwards facing rim 63 a

25 notch 64 for each shoulder 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 lugs 61 prevent withdrawal of the piston 9 from 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 10 is illustrated, whereas only a part of the ring 18 with the lugs 61 and the notch 64 is shown.

Fig. 10A 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 en 61b, whereas the shoulder 60 abuts on the rim 63 of the ring 18.

When, as shown in Fig. 10B, the piston rod 10 is drawn outwards for the first time in order to draw air in, the first lug 61a -moves against the connecting piece 58 whereby 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. 10C 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. 10D 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 Fig. 10E, arriving between the second and the third lug 61b and 61c respectively. In the position of Fig. 10E, the shoulder 60 abuts against the rim 63 of the ring 18.

In order to prevent that the ring turns when the lug 61b slides over the chamfered rim 59, a small guiding plate 66 can be arranged parallel to the rib 56 but at such a distance from the inclined connecting piece 58 that between them a passage remains for passing a lug 61, as clearly appears from Fig. 10B. During the pushing in of the piston rod 10 in the vicinity of the position according to Fig. 10D, this guiding plate 66 arrives between the lugs 61b and 61c, thus preventing the turning of the ring 18, whereas at the same time the lug 61b is ambiguously guided over the chamfered side 59.

When the piston rod 10 is withdrawn again from the position of Fig. 10E in order to draw in injection fluid, the position of Fig. 10F is reached, the ring 18 then being turned in the same way as in the position of Fig. 10B. When the piston rod 10 is withdrawn further, the rib 56 moves between the lugs 61b and 61c as is shown in Fig. 10G. At the rotation of the ring in the position of Fig. 10F, the notch 64 has now turned in such a way that it becomes axially aligned with the shoulder 60 of the rib 57.

When the piston rod is pushed inwards again from the position of Fig. 10G in order to eject the injection fluid, the position of Fig. 10H is passed again, whereby the lug 61c slides over the chamfered rim 59 of the connecting piece 58. As shown in Fig. 10J, 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. 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 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 Figs. 10A, B, C, and D. In this modified embodiment, the or each rib 56 is widened at its upper side, the lateral 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. 11A shows the starting position which is equal to the one of Fig. 10A. Fig. 11B shows the position at the beginning of the rotation of the ring 18 because the first lug 61a is pressed away along the inclined edge 58, the second lug 61b now sliding over the chamfer 59 onto the widened part of the rib, in which position it remains further on as is shown in Fig. 11C. In the position of Fig. 11D, which corresponds with the one of Fig. 10D, the lug 61b slides off the widened rib 56 and then arrives behind the inclined edge 58. In this case the small guiding plate 66 is no more required.

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 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 would- itself turn with respect to the casing 1. In the embodiment shown in Fig. 9-the casing 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. A syringe comprising a casing with a piston/piston rod assembly shiftable therein and a needle foot latched at a first end of the casing, means being present to couple, in an 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, there being stroke limiting means which are adapted to limit the stroke length upon the pressing inwards of 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 liquid in such a way that upon repeated pressing inwards of the piston for the expulsion of the injection liquid 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) shiftable relative to either the assembly (9,10) or the casing (1) and engageable with either the casing (1) or the assembly (9,10), the shift distance corresponding at least approximately with the predetermined distance reachable between the piston (9) and the needle foot (6) with the limited stroke length, the ring (18) being shifted by co-operation with either the casing (1) or the assembly

(9,10) after initial withdrawal of the assembly (9,10), the assembly (9,10) co-operating with abutments which in the initial position of the ring (18) limit the inward stroke length of the assembly to the predetermined distance from the needle foot (6), whereas in the shifted position the inward stroke length is increased in such a way that the piston (9) can be coupled with the needle foot (6).

2. The syringe according to Claim 1, c h a r a c t e r i s e d in that: - the piston rod (10) has first and second support surfaces (16,17) with differing transverse dimensions, the second one (17) being situated axially inwards from the first (16) and having a smaller diameter than the first, the ring (18) is an inwardly resilient ring, which in the initial position rests clampingly against the first support surface (16), and then has a first external dimension, and, upon being shifted towards the second support surface (17), has a smaller second external dimension; the casing (1,2) is provided with a transverse abutment shoulder (20), the diameter of which is such that the ring (18) contacts it in the initial position but not in the shifted position, and the end (12) of the casing which is outside the outer side of this shoulder (20) is provided with one or more inwardly resilient tongues (15) which in the initial position are situated between the ring (18) and the shoulder (20), and after pressing the assembly (9,10) towards this shoulder (20) until abutment grippingly engage the ring (18) in order to shift the ring (18) after subsequent withdrawal of the assembly (9,10), towards the second support surface (17), c h a r a c t e r i s e d in that position the ring (18) is released from said tongues (15) and shoulder (20).

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 casing (1,2) or the tongues (15) which prevent the assembly (9,10) being pressed inwards, and in that on the casing (1,2) or the tongues (15) on the other side of the ring (18) one or more additional abutments (28) are present which upon ou war w rawa o e assem y 9,10 cause e r ng (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 a r a c e r s e d n 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 (9) 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 (6) 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 s 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 ciosed 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) v.l.an 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 lugs, 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_r 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.