WO2001021236A1

WO2001021236A1 - Auto-destruct syringe

Info

Publication number: WO2001021236A1
Application number: PCT/CA2000/001104
Authority: WO
Inventors: Douglas C. V. Campbell
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-22
Filing date: 2000-09-21
Publication date: 2001-03-29
Anticipated expiration: 2002-03-22
Also published as: AU7399800A; CA2282974A1

Abstract

The syringe is fitted with a deforming structure (50) for permanently deforming the barrel wall (12) to break the seal (30) between piston (20) and barrel wall. The deforming structure is pivotally mounted in the piston for rotation between an at rest position wherein the deforming structure does not deform the barrel wall and an activation position wherein the deforming means forcibly engages the barrel wall for permanent deformation thereof. An actuator is provided on the plunger for rotating the deforming structure into the barrel wall engaging position upon rearward movement of the plunger subsequent to a full or partial injection stroke. The mechanism renders the syringe non-reusable after a first injection stroke to ensure that the syringe cannot be refilled.

Description

AUTO - DESTRUCT SYRINGE

FIELD OF THE INVENTION

The invention relates to disposable, auto-destruct syringes which are rendered non-

reusable during or after a first use.

BACKGROUND OF THE INVENTION

A principal function of syringes is in conjunction with hypodermic needles for the

treatment of disease by way of intravenous or intramuscular injection in humans or

animals. When treating disease in this way, it is particularly important to prevent infection

of the patient injected.

Communicable diseases are transmitted and infection can be caused in different ways,

such as, by contact with body fluids of an infected person. Infection or transmission of a

communicable disease is undesirable and is especially unfortunate when due to inadvertence

or ignorance, for example, the sharing or reuse of hypodermic syringes.

The practise of sharing hypodermic syringes is especially prevalent among drug

users. Similarly, the reuse of hypodermic syringes has become a major problem in third-

world countries where syringes are used in vaccination campaigns. Often several children

are inoculated with the same syringe either by using large capacity syringes for multiple small injections, or by refilling or reusing the syringes, often without proper sterilization.

As a result of such misuse of hypodermic syringes, potentially disastrous body fluid

transmitted diseases, especially AIDS and Hepatitis, have spread at an alarming rate among

drug users and in third- world countries, particularly among children. Although not all new

cases are attributable to syringe reuse or sharing, it is estimated by the World Health

Organization that the total number of new cases could be significantly reduced if

transmission through contaminated syringes were prevented. In an effort to frustrate the

reuse of hypodermic syringes, disposable syringes have been developed which are intended

to be functional for only one single injection.

A variety of approaches have been adopted in the design and manufacture of single-

use syringes. These can be grouped into three basic categories: (1) the piston or plunger

lock type wherein retraction of the piston is prevented either always or after completion of

the injection; (2) the plunger separating type wherein the plunger separates from the piston

or the piston seal when the plunger is retracted; and (3) the cutting or deforming type

wherein the barrel wall is cut or deformed during injection. It is a major disadvantage that

in the first two types of single-use syringes, the lock type and the separating type, the

barrel, which is the most important part of any functioning syringe remains intact and may

be tampered with and reused. Thus, single-use syringes wherein the barrel is rendered unusable, for example through cutting of the barrel wall, are preferable. However, the

cutting type syringes also have certain disadvantages.

Examples of the third type of single-use or cutting-type syringe are known in the art.

Chiquar- Arias in U.S. Patent No. 3,667,657 discloses pre-filled syringes which include a

small stationary knife that is laterally fixed to the syringe plunger and engages an opening

in the wall of the syringe barrel. When the plunger is forced down into the barrel, as

during injection, the barrel wall is cut. This destroys the barrel behind the piston seal and

makes reuse of the syringe impossible. However, it is a disadvantage of pre-filled syringes

that they can only be used in those circumstances where injection of the respectively

included liquid is desired. In other words, numerous syringes filled with different

inoculates are required which increases the manufacturing and storage costs.

In U.S. Patent No. 3,951, 146, Chiquar- Arias describes syringes wherein the plunger

includes a housing or recess for a small knife which is forced radially outwardly by a

spring. The knife has a rearward rounded edge and a forward cutting edge. The plunger

can be moved rearward for filling of the syringe without cutting or damaging the barrel

wall. For insertion of the plunger during manufacture, a protection strip is inserted

between the knife and the barrel wall, which strip is then removed. Use of the protection

strip is disadvantageous since it adds an additional manufacturing step and thus increases

production cost. Furthermore, the spring loaded knife stays in contact with the barrel wall at all times which, despite the rounded rear edge of the knife, could damage the barrel wall

during aspiration of the inoculate and lead to leakage around the plunger or through the

barrel wall.

An auto-destruct disposable syringe with retractable knives is disclosed in Canadian

Patent Application Serial No. 2,045,499 by Fenet. The syringe includes a barrel, a piston,

and a plunger for moving the piston axially in the plunger. The knives are mounted on

flexible arms which are connected with the plunger and are retracted during the aspiration

stroke of the syringe. When the aspirated liquid is expelled from the barrel, the plunger is

pushed against the piston which moves the free end of the arms along an inclined ramp on

the piston, thereby forcing the knives against the barrel wall. The plunger and, thus, the

knives are oriented to be opposite preselected areas of reduced thickness in the barrel wall.

The reduced wall thickness permits penetration of the knives and cutting of the barrel wall,

thereby destroying the barrel behind the piston as it is forced into the barrel during

injection. As a result, the syringe cannot be reused since the barrel will no longer hold a

vacuum and any liquid contained therein will leak through the cut areas of the barrel wall.

However, rotation of the plunger and knives relative to the barrel wall and especially the

areas of reduced wall thickness will render the syringe reusable.

International publication WO 97/26933 by the present applicant discloses an auto-

destruct syringe in which the integrity of the syringe is destroyed during a second aspiration stroke. The syringe is initially supplied with the plunger in a first position

relative to the piston. In this position, the piston can be moved rearward in the syringe by

pulling the plunger. To inject, pushing on the plunger forces the head of the plunger

forward to move past a pair of opposing cutter arms on the piston which each carry a knife

blade and into a second position. The plunger includes a pair of opposing, rearwardly

inclined ramps on which the cutter arms slide during movement of the plunger relative to

the piston. Once the plunger is in this second position, any subsequent attempt to withdraw

the plunger, for example for a second aspiration of the syringe, forces the cutter arms

outwardly against the syringe barrel, thereby forcing the associated knife blades against the

barrel wall to permanently destroy the integrity of the syringe.

It is a disadvantage of this prior art syringe construction that the reliability of the

auto-destruct mechanism thereof depends upon the outward force applied against the two-

knife carrying arms by the plunger. Furthermore, the strength of these arms is limited since

they must be small enough to fit between the plunger and the barrel wall. This renders the

arms relatively weak which results in the arms braking off when a large pulling force is

applied to the plunger. Further, the outward force that can be applied by the cutter arms is

limited and directly dependent on the pulling force exerted on the plunger and the angle of

inclination of the ramps. Small angles will result in an insufficient outward force and large

angles may result in such high friction between the cutter arms and the ramps to allow retraction of the plunger and piston without destruction of the barrel wall. Thus, the

barrel wall must be weakened for reliable operation of the mechanism. However, if the

wall is too thin, the integrity of the syringe during injection may be compromised. On the

other hand, if the wall thickness is too large, the cutter arms may not be able to cut or

score the barrel wall sufficiently to break the piston/ barrel seal. This may render the

syringe impractical. Moreover, since auto-destruct syringes must be discarded after a single

use, they should be made available at the lowest possible price to reduce the financial strain

on the patient, the health care system and international health organizations. This requires

that the syringe be manufactured from relatively economical materials such as plastics.

However, during tests with knives manufactured from inexpensive plastic material, the

inventors of the present application have found that such knives tend to quickly become

blunt, forcing the use of higher priced plastics or metal. Premature wear of ramp-operated

knives may lead to failure of the knives part way during the injection stroke, leaving a

portion of the barrel intact and allowing partial reuse of the syringe. Thus, an economical

tamper resistant auto-destruct syringe is desired which reliably prevents even partial reuse. SUMMARY OF THE INVENTION

These disadvantages are now overcome with an auto-destruct syringe in accordance

with the present invention wherein the integrity of the syringe is reliably destroyed only

when refilling of the syringe is attempted i.e. during a second aspiration stroke with no

damage to barrel integrity during the injection stroke.

It is an object of the invention to provide an improved mechanism for an auto-

destruct syringe of this general type. Preferably, this is achieved by a mechanism for

cutting of the syringe barrel starting at the front end or for breaking the seal between the

barrel wall and the piston, for example by permanently deforming the barrel wall, which

mechanism is activated upon an attempted refilling of the syringe, the third stroke. By

destroying the seal during the third stroke the axial forces required for permanently

deforming the syringe barrel, for example by cutting, are not superimposed onto the basic

force required for pushing the piston down the barrel during injection. In other words, the

self-destruction operation of the syringe will not interfere with the injection stroke so that

compliance with international guidelines which require that the axial force for pushing the

piston down the barrel during injection not exceed a maximum value, is easily achievable.

In the preferred embodiment, the auto-destruct mechanism includes a piston provided

with a deforming means or cutter which is pivotally mounted therein for rotation between

an at rest position wherein the deforming means is recessed into the piston and does not forceability engage the barrel wall and an operating position wherein the deforming means

is forced with a deformation edge into the barrel wall. The deforming means is preferably

mounted in an axially fixed location in the piston and rotated by the plunger upon axial

movement of the plunger relative to the piston. In the at rest position, the deforming means

is preferably completely recessed thereby permitting assembly, filling and injection by

manipulation of the plunger. In the operating position, at least the deforming edge of the

deforming means extends beyond the outside diameter of the piston, to cause deformation

of the barrel wall.

In another preferred embodiment, the deforming means is a cutter, at least a part of

which extends radially beyond the piston to cut the barrel wall.

In an alternative embodiment, that part of the cutter extending beyond the piston

merely burrows into or deforms the barrel wall.

Accordingly, the invention provides an auto-destruct mechanism for a syringe having

a syringe barrel for holding fluid and having an open rear end and a closed front end with a

passage extending through the closed front end of the barrel to permit expulsion of fluid

therethrough from the interior of the barrel. The mechanism includes a piston

reciprocatable in the barrel for sealingly engaging the barrel wall; a plunger having a

forward portion normally interlocked with the piston and a rearward portion to be

manipulated by a user of the syringe; connecting means for interlocking the piston with the plunger to permit axial movement of the piston in the barrel by operation of the plunger;

the connecting means permitting a preselected amount of axial movement of the plunger

relative to the piston between a thrust position wherein the piston is advanced in the barrel

by the plunger and a pull piston where the piston is retracted in the barrel by the plunger;

deforming means for permanently deforming the barrel wall to break the seal between the

piston and the barrel wall, the deforming means being pivotally mounted in the piston for

rotation between an at rest position wherein deformation of the barrel wall by the

deforming means is prevented, and an operating position wherein the deforming means

forcibly engages the barrel wall for permanently deforming the barrel wall; and an

activating means on the plunger for rotating the deforming means into the operating

position upon movement of the plunger into the pull position after at least a partial injection

stroke.

The term permanently deforming the barrel wall in the context of this application is

intended to include puncturing or cutting of the barrel wall, burrowing into the barrel wall

to produce a permanent groove, and other actions which will break the seal between the

piston and the barrel wall and allow leakage around the piston, thereby preventing the

further generation of pressure or vacuum in the barrel.

One feature of the present invention is that the rotation movement of the deforming

means guarantees an engagement of the deforming means with the barrel wall at a constant force independent of the amount of retraction force applied to the plunger. Furthermore,

the direction of rotation of the deforming means is preferably selected such that a barrel

engaging end or edge thereof moves radially outwardly and axially forwardly into

engagement with the barrel wall upon rotation into the operating position. This will ensure

that the deforming means is kept in the operating position during the third stroke and not

rotated back into the at rest position upon retraction of the piston.

In an especially preferred embodiment, the piston and plunger are shaped and

constructed to partially overlap when interlocked, the piston has a radial recess in its outer

surface for receiving the deforming means and the connecting means has a deforming

means receiving recess such that the piston and the plunger are interlocked when the

deforming means is inserted into the radial recess to extend into the deforming means

receiving recess.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described by way of example

only and with reference to the attached drawings, wherein:

FIGURE 1 is an axial cross-section through the preferred embodiment of the auto-

destruct mechanism in accordance with the invention and with the cutter in the safety

position for insertion of the mechanism into a syringe barrel; 11

FIGURE 2 is an axial cross-section through the auto-destruct mechanism shown in

FIGURE 1 , but during the beginning of the intake stroke with the cutter in the cocked

position;

FIGURE 3 is an axial cross-section through the auto-destruct mechanism shown in

FIGURE 1 , but during the first aspiration stroke, with the cutter in the cocked position;

FIGURE 4 is an axial cross-section through the auto-destruct mechanism shown in

FIGURE 1, during the exhaust stroke, with the cutter in the at rest position;

FIGURE 5 is an axial cross-section through the auto-destruct mechanism shown in

FIGURE 1 , illustrating the primed blade of the cutter at the beginning of the second

aspiration stroke, with the cutter in the operating position;

FIGURE 6 is a perspective view of the auto-destruct mechanism shown in FIGURE

1, illustrating the position of the cutter receiving recess;

FIGURE 7 illustrates an axial cross-section through the plunger;

FIGURE 8 illustrates an enlarged side view of the front end of the plunger shown in

FIGURE 7;

FIGURE 9 is a perspective view from above of the plunger front end shown in

FIGURE 8;

FIGURE 10 is a top plan view of the plunger front end shown in FIGURE 8;

FIGURE 11 is a side elevational view of the cutter; FIGURE 12 is a top plan view of the cutter;

FIGURE 13 is a top plan view of the piston showing the cutter receiving recess.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of an auto-destruct mechanism in accordance with the

invention is preferably used in a disposable syringe into which it is inserted and with which

it is packaged in the empty condition to allow aspiration of an injectable liquid and

subsequent injection without destruction of the syringe. The auto-destruct mechanism

destroys the integrity of the syringe barrel once re-use is attempted after injection by an

attempt of refilling of the syringe during a second aspiration (herein also referred to as

"third stroke").

In particular, the mechanism in accordance with the invention is inserted in a syringe

barrel as shown in Figure 5 of the drawings. The syringe consists of a syringe body 10

including a barrel 12, a piston 20 including a seal 30 and an auto-destruct mechanism 50

for permanent deformation of at least the barrel interior wall 13 to break the seal between

the piston and the barrel. The auto-destruct mechanism 50 includes the piston 20, a plunger

40 with a connecting means in the form of a connecting portion 5 for connecting the

plunger 40 with the piston 20, thereby allowing the user of the syringe to reciprocate the

piston by way of the plunger, and a cutter 60 having a blade portion 61 and a lever portion 62. The syringe body 10 includes a cylindrical barrel 12 which has an open rear end 7 and

a closed front end 1. The front end 1 of the barrel is provided with an integral needle

mount 2 for attachment of a hypodermic needle. The front end 1 further has a fluid passage

3 for the expulsion of fluid from the barrel 12 and into a needle (not shown). Although a

needle (not shown) can be removably attached to the mount 2 for separate disposal, it is

preferably permanently affixed to the needle mount 2 to prevent the re-use of possibly

contaminated needles.

An auto-destruct mechanism 50 is shown in detail in Figures 1 through 4. As can be

seen from reference to Figure 1 , the piston 20 includes a seal or stopper 4 which is made

of elastomeric seal material such as butyl rubber used in conventional syringe piston seals.

The seal 4 is preferably connected with the piston 20 by way of an interference fit. Other

methods of attaching the seal to the piston are known in the art and do not need to be

discussed in detail herein. The outer diameter of at least a circumferential section of the

seal 4, at least in a preferred embodiment, is slightly larger than the inner diameter of the

syringe barrel 12, to ensure a liquid tight sliding engagement therebetween. In one

embodiment of the seal, a circumferential groove 9 is provided in the outer surface of the

seal 4 to improve the sealing characteristics thereof. Alternatively, the seal 4 can have a

diameter which is marginally smaller than the syringe barrel diameter and include one or

more circumferential sealing ribs giving the stopper an overall diameter larger than the syringe barrel inner diameter, thereby ensuring a reliable seal. The piston 20 also contains

a cutter recess 6. In the assembly position, the cutter or deforming means does not extend

beyond the recess 6, but is contained entirely within the outer diameter of the

plunger /piston combination. The piston 20 and plunger 40 are constructed such that the

plunger 40 can move a defined axial distance A ( see Figure 3) relative to the piston 20 in

the installed/assembled condition of the auto-destruct mechanism 50. The extent of this

axial movement is defined by the interaction of the plunger front end 9, the piston front

end 8 and the cutter 60. The piston 20 in the preferred embodiment is sleeve-shaped and

the plunger front end 9 fits thereinto. In the region of overlap between the plunger and the

piston, the plunger is divided into two portions, the plunger tongue 41, and the interlocking

portion 43 which functions as the connecting means (see Figure 8) . As more clearly

apparent from Figures 8 to 10, the plunger tongue 41 has a priming opening 47 for

receiving the lever portion 62 of the cutter 60. Forwardly of this priming opening 47, the

plunger tongue 41 has a solid front end 44, the length of which is selected such that it

maintains the cutter 60 in the safety position when the plunger 40 is completely inserted

into the piston 20, to prevent the cutter 60 extending beyond the outer diameter of the

piston 20 during assembly of the auto-destruct mechanism and insertion thereof into a

syringe. A cutter opening 48 is provided in the interlocking portion 43 for receiving the

cutter 60 in the assembled condition. The sleeve 20 includes a cutter receiving recess 6 into which the cutter 60 is inserted. It is readily apparent from the drawings that the rearward

movement of the piston upon rearward pulling of the plunger is only possible when these

two parts are interlocked by the cutter 60 received in the cutter recess 6 (see Figure 1) and

extending into the cutter opening 48. If the cutter 60 is not inserted into the cutter receiving

recess 6, plunger 40 is not interconnected with piston 20 in this embodiment. However, a

separate structure for interconnecting the plunger 40 with the piston 20 can be provided

which interconnects the two components independent of the cutter 6, while still permitting

relative axial movement with an axial length A. For example, piston 20 can be provided at

its rear end 21 with an axially inwardly extending rib or flange (not shown) which would

act as a stop for guide tabs 42 of the plunger 40, to prevent removal of the plunger front

end 5 from the piston 20 while allowing relative axial reciprocating movement. Other

methods and structures for interconnecting the piston 20 and the plunger 40 would be

readily apparent to the art skilled person. The cutter opening 48 is offset axially forwardly

of the priming opening 47 to permit progressive rotation of the cutter from the safety

position into the cocked position, then into the at rest position and finally into the operating

position through repeated reciprocation of the plunger 40 relative to the piston 20.

As is best seen in Figure 6, 11 and 12, the cutter 60 includes a generally cylindrically

central body 63, a blade portion 61, a lever portion 62 and a pair of pivots 64 extending coaxially laterally from the cutter body 63. The cutter 60 also includes a pair of lateral

detents 65 which protrude laterally from the cutter body 63 at a top edge thereof.

In the assembly position of the preferred embodiment illustrated in Figure 1 , the

cutter 60 sits in the cutter recess 6 and extends with its lever portion 62 into the cutter

opening 48 of the interlocking portion 43. The cutter recess 6 includes a pair of laterally

extending groves 66 for rotatably receiving the pivots 64 of the cutter. The cutter recess 6

has detent receiving cutouts 67 in opposite side walls of the recess for receiving detents 65

of the cutter 60 in the inserted condition as will be described in more detail further below.

When the auto-destruct mechanism 50 is in this assembly position or orientation, the

mechanism can be safely inserted into the syringe barrel 12 without causing any damage to

the barrel wall 13. In this position, the front end surface 11 of the plunger 40 engages a

thrust shoulder 29 on the piston (see Figure 5), while the cutter 60 is maintained in the

safety position by the solid activation end 44 of the plunger 40, in which position the cutter

is completely received within the piston 20. This presents a significant advantage in

manufacturing cost, since no cutter guards or safety strips are required for assembly of the

syringe. The mechanism 50 is simply assembled by overlapping the plunger 40 and the

piston 20 and placing the cutter 60 in the recess 6 and then installed by inserting the

mechanism into a syringe barrel. Syringes including the mechanism in accordance with the

invention are preferably shipped with the mechanism in the assembly position. OPERATION

To fill a syringe including the auto-destruct mechanism in accordance with the

invention, the user pulls back the plunger 40 thereby retracting the piston 20. Upon the

initial pulling back of the plunger, the plunger moves rearwardly relative to the piston until

a thrust edge 45 of the cutter opening 48 engages the lever portion 62 of the cutter 60 (see

Figure 2). In this condition, the cutter 60 is completely recessed within the piston 20 and

its lever portion 62 is locked in place between the thrust edge 45 and the activation end 44

of the plunger tongue 41. Upon further pulling back of the plunger 40, the thrust edge 45

forces the lever portion 62 rearwardly, thereby rotating cutter 60 forward about the axis

defined by the pivots 64 until the forward end surface 46 of the cutter opening 48 comes to

rest against the cutter (see Figure 3). In this condition, the cutter is in the cocked position,

the lever portion 62 of the cutter 60 forces against the solid activation end 44 of the tongue

41 and deflects it downwardly. The detents 65 of the cutter 60 in this position engage the

respectively associated detent receiving cutouts 67 so that a reverse rotation of the cutter 60

back to the safety position is no longer possible ( see Figure 6). When the plunger 40 is

subsequently pushed into the barrel 12 for injection of the fluid aspirated during the

preceeding aspiration stroke, the plunger 40 moves forward relative to the piston 20 until

the front end surface 11 of the plunger engages the thrust shoulder 29, after which the

piston 20 is moved down the barrel during advancement of the plunger. Since the cutter 60 is in the cocked position in which reverse rotation is prevented, the lever portion 62 slides

along the solid activation end 44 of the tongue 41 during relative displacement of the

plunger and the piston until the lower portion reaches the priming opening 47. At that

point, tongue 41 snaps back from the deflected condition (see Figure 3) into its straight

configuration (see Figure 4), thereby priming the mechanism for future forward rotation of

the cutter 60.

Once the injection is completed, the syringe is supposed to be discarded. However, if

reuse of the syringe is attempted by pulling of the plunger 40 backwards, the cutter 60 is

rotated into the activated position shown in Figure 5 wherein the blade portion 61 and

especially the associated cutting edge 68 is forced into the barrel wall 13 to destroy the seal

between the piston 20 and the barrel 12 by either cutting the barrel wall or sufficiently

scoring it to reliably prevent the generation of another vacuum in the syringe. This rotation

is achieved by the solid activation end 44 of the tongue 41 pulling the lever portion 62

backward so that the cutter 60 rotates further about the pivots 64. Due to the length of the

lever portion 62, i.e. the distance of the point of engagement between the lever portion and

the activation end 44 from the pivot axis, the blade portion 61 and, thus, the cutting edge

68, is pushed at a large force into the barrel wall 13 thereby guaranteeing proper

functioning of the mechanism. Also, the mechanism in accordance with the invention is

more sturdy than the mechanisms in the art wherein relatively fragile components such as drag arms are relied upon for interconnection between the piston and the plunger.

Moreover, the ramp structures used in the prior art for creating an outward force on the

cutter elements upon relative movement between the plunger and the piston do not operate

to create as large an outwardly directed cutter engagement force as is generated upon

rotation of the cutter 60 with the mechanism in accordance with the present invention.

While only specific embodiments of the invention have been described, it is apparent

that various additions and modifications can be made thereto, and various alternatives can

be selected. It is, therefore, the intention in the appended claims to cover all such

additions, modifications and alternatives as may fall within the true scope of the invention.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVEPROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An auto-destruct mechanism for a syringe with a syringe barrel for holding a fluid

having an open rear end and a closed front end and a passage extending through the closed

end of the barrel for expulsion of fluid from the interior of the barrel, the mechanism

comprising;

a piston for reciprocation in the barrel and for sealingly engaging the barrel wall;

a plunger having a forward portion for engagement with the piston and a rearward

portion for manipulation by a user of the syringe;

connecting means for interlocking the piston with the plunger to permit axial

displacement of the piston in the barrel by axial operation of the plunger;

deforming means for permanently deforming the barrel wall to break the seal between

the piston and barrel wall, the deforming means being pivotally mounted in the piston for

rotation between an at rest position wherein the deforming means does not deform the

barrel wall an activation position wherein by the deforming means forcibly engages the

barrel wall for permanent deformation thereof; and an activating means on the plunger for rotating the deforming means into the barrel

wall engaging position upon rearward movement of the plunger after a full or partial

injection stroke.

2. An auto-destruct syringe as defined in claim 1, wherein the whole barrel wall is of

reduced thickness and along the whole circumference thereof.

3. An auto-destruct syringe as defined in claim 1 , further including stop means for

preventing removal of the plunger from the barrel.

4. An auto-destruct syringe as defined in claim 3, wherein the stop means is a

circumferential, radially inwardly extending crimp in the barrel wall.

. An auto-destruct syringe as defined in claim 1 , wherein a cup-shaped piston seal is

attached to a front end of the piston for sealing engagement with the barrel wall.

6. An auto-destruct syringe as defined in claim 5, wherein a collar-shaped seal

circumferentially surrounds the front of the piston sleeve causing sealing engagement to the

barrel wall.

7. An auto-destruct syringe as defined in claims 4 and 5, wherein the outer diameter of

the seal is slightly larger than the inner diameter of the barrel.

8. An auto-destruct syringe as defined in claims 4 to 6, wherein the seal is made of an

elastomeric material.

9. An auto-destruct syringe as defined in claim 7, wherein the elastomeric material is

butyl rubber.

10. An auto-destruct syringe as defined in claim 1, wherein the rotatable deforming

means is provided with means for preventing rotation back to the at rest position.

11. An auto-destruct syringe as defined in claim 8, wherein the means for preventing

back rotation comprises at least one detent.