Abstract:
A syringe has a barrel to receive a cartridge. The barrel has a front end portion to which a needle is connected for engagement with the cartridge. At its rear end, the barrel has a plunger mechanism. A sleeve is slidably mounted on the barrel and can be pushed forwards to sheath the needle. The needle is mounted on the barrel via a push-fit mounting device. The needle can be removed for disposal in a container by inserting the syringe into a tube on top of the container so that the protective needle sleeve is pushed back and the needle and mounting device pass through a collar of gripping fingers at an inner end of the tube. The fingers catch behind the mounting device so that this is pulled off to drop into the container with the needle when the syringe is withdrawn from the tube.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to syringes, particularly although not exclusively for dental use, and is more particularly concerned with safe disposal of needles of such syringes. 
     A conventional dental syringe has a barrel with a plunger mechanism at a rear end and a threaded adaptor to receive a needle at a front end. In use a glass cartridge, which contains an injectable liquid between a rear bung and a front membrane, is inserted into the barrel. A needle having a threaded hub adjacent to its rear end is screwed onto the adaptor so that it penetrates the cartridge membrane, and the plunger mechanism is engaged with the bung at the rear end of the cartridge. 
     After use, the cartridge and needle are removed and discarded. For safety purposes, the needle may be deposited in a so-called ‘sharps’ container for safe disposal. 
     In order to avoid needle-stick injuries there have been various proposals for facilitating safe handling of the needle during removal and disposal. 
     EP 0441628A describes the use of a removal device, which may be power operated, to unscrew the needle for deposit in a sharps container without requiring direct manual contact with the needle hub or syringe adaptor. However, there is the problem of avoiding contact with the needle after use and prior to its presentation to the removal device. 
     U.S. Pat. No. 5,403,288 and U.S. Pat. No. 5,989,226 describe the use of a sleeve which can be fitted over the needle after use. This arrangement can give effective protection against needle stick injuries. However, there is then the problem of convenient removal and disposal of the covered needle. In each case the needle is removed together with the sleeve which is in practice requires the sleeve and possibly associated components or even the entire syringe to be disposable. Whilst disposable syringes can be acceptable there is also a requirement for syringes which have re-usable main parts. 
     One object of the present invention is to enable the needle of a syringe to be easily and conveniently removed for disposal whilst being effectively protected within a sleeve to prevent needle-stick injuries but without requiring disposal of the sleeve with the needle. 
     According to one aspect of the invention therefore there is provided a method for disposal into a container of a needle mounted on a syringe via a push-fit mounting device,
         the syringe having a barrel to receive a cartridge of injectable liquid with a forward end on to which the mounting device is a push-fit, a plunger mechanism connected to a rearward end of the barrel, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it sheaths the needle,   the container having a disposal chamber with an opening thereto provided with a receiving structure having a gripper device,   wherein the syringe is presented to the said receiving structure with the needle sheathed by the said sleeve, the sleeve is pushed back to expose the needle, and the mounting device passes beyond the said gripper device,   and the syringe is then withdrawn so that the needle with the mounting device is pulled off the syringe barrel, for deposit in the disposal chamber, by engagement of the mounting device with the gripper device.       

     With this method the needle can be protected by the sleeve as it is presented to the container opening and the needle can then be removed and deposited in the container without requiring disposal of the sleeve. The needle can therefore be removed and safely discarded easily and conveniently, and the main parts of the syringe, including the sleeve, can then be re-used with a fresh needle and mounting device. 
     Preferably, the arrangement is such that the gripper device is a non-return device which engages behind the mounting device so as to abut a rear structure, such as a rear end edge or face, of the mounting device. Most conveniently the gripper device may be arranged to extend peripherally or circumferentially around relative to the syringe axis and thus, for example may comprise a ring of gripper fingers which are preferably resiliently deflectable to allow passage of the mounting device therethrough. 
     In order to ensure that the mounting device passes beyond the gripper device sufficiently to ensure that it is pulled off when the syringe is withdrawn, indicator marks or the like may be provided e.g. on the receiving structure and the syringe sleeve for alignment purposes, and/or the gripping device may be visible. 
     Preferably also, the arrangement may be such that the receiving structure engages a part, particularly a rear part, of the sheath, such as an enlarged rear collar, so as to push back the sheath. 
     In a particularly preferred embodiment the sleeve can be retained in the said forwards position by a releasable locking device, whereby this device is released after presentation of the syringe to the container opening has commenced. 
     The mounting device may comprise a unitary member attached, particularly permanently attached, to or integrated with the needle, as a so-called needle hub. 
     Alternatively the mounting device may comprise a combination of two parts comprising a needle hub integrated with the needle, and an adaptor which is a push-fit on the forward end of the barrel and to which the needle hub is connected. 
     Thus and in accordance with a second aspect of the invention there is provided a syringe, for use with the above method, comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle having a mounting hub, and a rearward end for connection to a plunger mechanism, a needle adaptor for mounting on the forward end of the barrel for retaining engagement with a hub of the needle to form with said hub a mounting device for the needle, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle, characterised in that the needle adaptor is a push-fit on the forward end of the barrel whereby the needle and adaptor can be separated from the barrel and the sleeve by application of a linear acting removal force to the said adapter. 
     This arrangement allows the needle to be removed and discarded separately from the sleeve. 
     Also, insofar as removal requires only the application of a linear pull-off force, the needle can be detached in a particularly quick and convenient manner notwithstanding the presence of the sleeve. 
     With regard to the push-fit adaptor, this may be in the form of an end piece comprising a cap with one or more internal configurations such as projections which interengage surfaces or cooperable configurations of the barrel to establish a retaining e.g. tight frictional and/or snap fit. 
     The interengagement between the needle hub and the end-piece may be effected, in conventional manner, by screw fit engagement of an internal thread of the hub and an external threaded projecting part of the cap. 
     With regard to the receiving structure of the container of the above described method, this preferably comprises a passageway with an outer end through which the syringe is presented to the said opening, an inner end in communication with the said opening and having the gripper device thereat, and an abutment structure, e.g. at the outer end, for engagement with the sleeve to push this back. 
     Thus, and in accordance with a third aspect of the present invention there is provided a container for use with the above mentioned method comprising a disposal chamber having an opening thereto, and a receiving structure with a gripper device for holding a mounting device of a syringe needle to cause the needle to be pulled off the syringe on withdrawal thereof from the gripper device, characterised in that the receiving device comprises a passageway with an outer end through which the syringe is presented to the said opening and an inner end in communication with the said opening and having the gripper device thereat. 
     The gripper arrangement may be a non-return gripper which cooperates with a trailing abutment of the mounting device and thus may comprise a collar or ring having inwardly directed fingers which may deflect outwardly to allow passage of the abutment and then return inwardly to catch behind the abutment. This trailing abutment may comprise a rear end face or rim of the mounting device. 
     Other gripper arrangements of the nature of catch or interlock or abutment devices may also be used. 
     With regard to the passageway, most preferably the arrangement is such that this will receive the syringe barrel and the needle, but will not allow complete passage of the syringe sleeve whereby this is retracted as the syringe is inserted. Thus, the passageway preferably has an abutment structure arranged to engage a part e.g. an enlarged rearward end portion of the syringe sleeve. This abutment structure may be defined e.g. by a shoulder or rim at an entrance to the passageway. 
     The passageway may comprise a tube, such as a cylindrical tube. 
     The chamber may be a box capable of receiving multiple needle/mounting device combinations for disposal. Thus the chamber may be of substantially greater volume than the aforesaid passageway. This chamber may be linked to the passageway transversely to the direction in which the needle is inserted through the opening. 
     Alternatively to a multi-use box, the chamber may be for single use. In this case it may be of the nature of a tube with the opening through which the needle is inserted having an entrance at one end. The gripper device may also act, or be used in combination with, a holding device so that after detachment the needle/mounting device combination is held in position in the container. In this case, the tube may be open at the end remote from the needle entrance. 
     The sleeve of the syringe used with the above mentioned method may be mounted on the barrel so as to be slidable between rear and forward positions at which respectively the needle is arranged to be fully exposed and fully covered. At these limit positions the sleeve may be held in position frictionally and/or by a releasable catch or the like. 
     In one embodiment, the syringe sleeve has mounted thereon a member movable between release and locking positions whereby in the locking position cooperable configurations on the member and on the barrel interengage to prevent relative longitudinal movement of the member and the barrel and in the release position these configurations are disengaged to permit longitudinal movement. 
     Thus and in accordance with a further aspect of the invention there is provided a syringe for use with the above described method comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle via a push-fit mounting device, and a rearward end for connection to a plunger mechanism, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle, characterised in that the syringe sleeve has mounted thereon a member movable between release and locking positions whereby in the locking position cooperable configurations on the member and on the barrel interengage to prevent relative longitudinal movement of the member and the barrel and in the release position these configurations are disengaged to permit longitudinal movement. 
     Preferably the movable member is provided at the rear end of the sleeve. 
     Conveniently, the movable member is rotatable about the axis of the barrel between locking and release positions. These positions may be limit positions which may be defined by interengagement of a peg with a slot, or by aligned markers or otherwise. The cooperable configurations may comprise a projection, particularly an elongate projection, on the member and a slot or groove in a projecting part of the barrel or vice versa. 
     The syringe sleeve may have a main tubular body part restrained against rotation around the barrel i.e. so that it is guided for longitudinal movement along the barrel. This may be achieved by means of a longitudinal groove or slot on one and a projection, particularly an elongate projection, which engages the groove or slot on the other and these may be aligned with the aforesaid projection and slot or groove of the movable member in the release position thereof. 
     The rotatable member may also comprise a tubular part or collar which is preferably of shorter length than the aforesaid main body part. 
     The syringe of this further aspect of the invention may have any or all of the features of the syringe of the second aspect of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described further by way of example only and with reference to the accompanying drawings in which: 
         FIG. 1   a  is a plan view of one form of a syringe according to the invention with the sleeve pushed forwards; 
         FIG. 1   b  is a plan view of one form of a syringe according to the invention with the sleeve pushed rearwards; 
         FIG. 2  is a sectional view of a forwards section of the syringe of  FIG. 1 , within part of a sharps container adapted for use with the syringe, with the sleeve retracted; 
         FIGS. 3 &amp; 4  are end and top views of the sharps container, the latter Figure also showing the syringe and having a section removed; 
         FIG. 5  is an exploded view of the syringe of  FIG. 1 ; 
         FIG. 6  is a sectional view of part of the container of  FIGS. 3  and  4  with the syringe shown in full; 
         FIG. 7  is a further sectional view of a rearward detail of the syringe with the sleeve retracted; and 
         FIG. 8  is an exploded perspective view of the rearward end of the sleeve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a dental syringe has a barrel  1  in the form of a tube of circular cross-section which is open at its rear (distal) end and closed at its forward (proximal) end and has a cut-out side opening  1   a.    
     The barrel  1  has a finger grip structure  2  attached to the rearward open end, with a plunger  3  extending through this structure  2 . The plunger  3  terminates at a forward free end with an enlarged head  4 , and at a rearward end with a further finger grip  5 . 
     At its forward end, the barrel  1  has an integral end portion  6  with a flat radially extending front end face  7  with an axial aperture  8  bounded by a rearwardly projecting tapered structure  9 . There is a longitudinal slot  11  running from the end face  7 . 
     The barrel  1 , finger grip structure  2  plunger and finger grip  5  may be formed from stainless steel or plastics which can be disinfected by autoclaving or other technique. 
     As shown in  FIG. 5 , the barrel has diametrically opposed longitudinally extending ridges  12  with forward and rearward cut-out slots  13 ,  14 . 
     Around the barrel  1  is located a sleeve  15  comprising an open ended circular cross-section tube  16  having a slightly larger diameter than that of the barrel  1 . The tube  16  may be transparent or may have transparent or cut-out side sections for viewing of the barrel  1  through the side opening  1   a  or through windows  16  cut out of the barrel  1  opposite to the window  1   a . The sleeve  15  is also formed from autoclavable material so as to be reusable e.g. stainless steel or plastics. 
     At a rearward end of the tube  16  there is mounted a locking member  17  in the form of an open ended tube or collar of greater diameter than the tube  16 . This collar  17  is retained on the tube  16  so that a rearward end region projects beyond the end of the tube  16  and forms an inturned lip  18 . A major part of the collar  17  overlies the tube  16  and is retained on the tube  16  by interengagement of an inward projection  17   a  on the collar  17  with a recess in a springy end part  17   b  of the tube  16 . A curved insert  19  fits in a slot  20  in the tube  16  and projects through the tube so as to project into the cartridge slot  1   a  in the barrel  1 . The arrangement is such that the collar  17  can rotate about the tube  16  around its axis between limit positions defined by the relative dimensions of the projection  17   a  and the cooperable slot in the end part  17   b  but is retained against longitudinal displacement on the tube  16 . Markers  21  are provided on the collar  17  and on the tube  16  and are aligned respectively at the different limit positions. 
     The tube  16  has diametrically opposed internal grooves  10   a  ( FIG. 8 ) which slidably interfit with the ridges  12  and extend along the entire length of the tube. 
     The sleeve  15  can slide to a rearmost position ( FIG. 1   b ) at which its rear end abuts or in close to the finger grip structure  2  and its front end is generally level with the forward end of the barrel  1 . 
     The sleeve  15  can slide to a forwards position ( FIG. 1   a ) at which its rear end is slightly behind the front end of the barrel  1  and the sleeve  15  extends forwardly beyond such front end. 
     The interengagement between the insert  19  and the cartridge slot  1   a  allows longitudinal sliding until the insert abuts the forwards end of this slot  1   a . The sleeve  15  is thereby prevented from displacement off the barrel  1 . 
     The interengagement between the internal grooves of the tube  16  and the ridges  12  permits easy sliding but prevents relative rotation of the tube  16  and the barrel  1 . 
     At the open front end of the barrel  1  there is mounted a disposable plastics end piece  22 . 
     The end piece  22  is a one piece plastics moulding in the form of a cap of circular cross-section having a front end wall  23  and a generally cylindrical body  24  with a rear opening. 
     The front end wall  23  has a forward central axially extending projection  25  with an external screw thread and an internal axial through bore  26 . Within the body  24  there is a rearward central axially extending tapered projection  27  also with an axial through bore. 
     From the end wall  23  of the cap  22  there is a longitudinal projecting ridge  29 . 
     The end-piece  22  is a push-fit onto the end of the barrel  1  with the rearward projection  27  entering the aperture  8  and with the projection  29  in the cap  22  engaging the slot  11  in the barrel  1 . This engagement is a tight fit so that the cap  22  is held securely in position. This tight fit is a function of tight wedging engagement of the cap  22  with the barrel  1 . Alternatively or additionally if desired there may be a snap-fit interconnection of e.g. slots in the cap with projections on the barrel  1 . A marker element  30  is provided on the cap  22  so as to help alignment of the cap projection  29  with the barrel slot  11 . 
     The sleeve  15  can be releasably locked in the forwards position by rotation of the collar  17  to one limit position to bring projections within the collar into engagement with the gaps  13 . The sleeve  15  can be released from this by rotation of the collar  17  back to its opposite limit position. In more detail the inturned rear end lip  18  of the collar  17  has diametrically opposed longitudinally extending slots  10  which in one position are aligned with the slots in the tube  16  and the ridges  12  on the barrel  1  thereby to permit longitudinal sliding with the tube  16  on the barrel  1 . When the collar  17  is rotated out of this position to the opposite limit position solid parts of the lip  18  are moved into the gaps  13  in the barrel ridges  12  thereby preventing longitudinal sliding movement. 
     The sleeve  15  is releasably retained in the rearmost position in similar manner by movement of the solid parts of the lip  18  of the collar  17  into the gaps of the barrel ridges  14 . 
     The syringe so far described is used with a conventional anaesthetic-filled cartridge  31  in the form of a glass tube sealed with a rear-end bung and a front end membrane, and a needle  32  comprising a stainless steel tubular member  33  with an attached hub  34 , in the form of an internally threading cap, adjacent to but spaced from its rear end. 
     In use, with the sleeve  15  in its forwards position and the plunger  3  retracted the cartridge  31  is inserted through the side opening  1   a  of the barrel  1 . 
     The plunger head  4  can then be moved forward to engage the cartridge bung. 
     The needle hub  34  is screwed onto the end piece  22  with the sleeve  15  in its rearward position. This causes the rear end portion of the needle  33  to pass through the bores  26  so as to be directed into position to penetrate the membrane at the front end of the cartridge  31 . 
     The interconnection between the end piece  22  and the end portion  6  of the barrel  1  is such that the end piece  22  cannot rotate relative to the barrel e.g. when the needle is screwed into position. 
     The inner projecting part  27  of the end piece  22  prevents contact between the rear part of the needle  33  and the end portion  6  of the barrel  1  thereby to limit contamination. Also it guides insertion of the needle and therefore reduces the risk of bending. 
     The sleeve  15  can now be moved to its forward position in which it completely covers the needle  33 . The sleeve  15  can be held in this forward position with the collar  17 . 
     When required, the collar  17  can be rotated to the release position and the sleeve  15  can then be moved back to its rearward position. The needle  32  is thereby exposed for use. 
     After use, the sleeve  15  is again moved to its forwards position and when required the needle  32  and end piece  22  are detached together and inserted into a sharps container  35  for disposal. The spent cartridge  31  can then also be removed and discarded. 
     As shown is  FIGS. 3 and 4 , the sharps container  35  comprises a generally rectangular box structure with a top wall  36  containing an upwardly projecting integral tunnel structure  37  which has an opening  38  at one end and is closed at the opposite end. The tunnel structure  37  is open to the interior of the box structure along its lower side via an opening  36   a  in the wall  36 . 
     As shown in  FIG. 6  the opening  38  is bounded by an outwardly flared rim and has a detachable cap  39  for temporary closure of the opening by insertion into this rim. Within the opening  38  there is fixed a tubular structure  40 , defined by a removable snap-in sleeve within a retaining structure  28  of the tunnel structure  37 , which is open at both ends and extends from the periphery of the opening  38  inwardly part way along the tunnel structure  37 . 
     Within the tubular structure  40  there is fixed a collar  41  which projects beyond the innermost end of the structure  40  and at such projecting end has a ring of resiliently deflectable fingers  42  which project axially into the tunnel structure  37  away from the opening  38  and are inclined inwardly towards the axis of the tubular structure  40 . 
     The tunnel structure  37  extends only partially along the top wall  36  of the container  35 . Beyond the closed end of the tunnel structure  37  there is a further opening  44  in the top wall  36 , which can be temporarily closed with a cover flap  43 , to receive spent cartridges  31 . 
     Internally, the box structure  35  has a compartment which receives the used needles  32  and spent cartridges  31 . The openings  36   a  and  44  communicate with this. 
     The syringe with a used needle in position is presented to the opening  38  with the sleeve  15  fully covering the needle  32  and locked in position. 
     The internal diameter of the tubular structure  40  is large enough to permit entry of the tube  16  of the sleeve  15  and is approximately the same length as such tube  16 . However, the internal diameter is not wide enough to receive the enlarged collar  17 . The syringe can therefore be pushed in until the collar  17  reaches the rim around the opening  38 . The collar  17  is then manually rotated to the release position and the syringe in pushed further in. 
     At the innermost end of the tubular structure  40 , a shoulder is defined between the tubular structure  40  and the collar  41 , the collar being of slightly smaller diameter than the tubular structure  40 . 
     As the syringe is pushed through the opening  38  the sleeve  15  is pushed back on the barrel  1  by engagement of the rim around the opening  38  with the collar  17  and the needle  32  and end-piece  22  ultimately pass through the collar  41  to a position beyond the free ends of the fingers  42 . The fingers  42  deflect outwardly to permit this and then close inwardly behind the end of the end piece  22  so as to grip the barrel  1  and engage the rim of the rear of the end piece  22 , as indicated in  FIG. 2 . 
     A marker or the like may be provided to indicate when the syringe is fully inserted to the extent that the fingers are locked behind the end piece  22 . 
     Withdrawal of the syringe using the finger grip structure  2  now causes the end piece  22  with the needle  32  to be pulled off the syringe barrel  1  and to fall downwardly through the opening  36   a  into the container  35 . The cartridge  31  can now be removed and inserted through the opening  44  into the container  35 . 
     The interfit between the barrel  1  and the cap  22  is such as to ensure secure retention in normal use but so as to permit release and pull-off of the cap  22  when a suitable force, acting longitudinally of the syringe axis is applied. 
     The main part of the syringe, namely the barrel  1 , finger grip structure  2 , plunger  3  and finger grip  5 , and sleeve  15  can now be disinfected and re-used with a fresh end piece  22 , needle  32  and cartridge  31 . 
     With this arrangement, needle stick injuries can be avoided with a syringe arrangement which permits retention for reuse of main parts of the syringe whilst facilitating ready removal and disposal of a used needle. The arrangement of the syringe is also such as to ensure safety during use. 
     It is of course to be understood that the invention in not intended to be restricted to details of the above embodiment which are described by way of example only. 
     Thus, for example, instead of using a conventional needle  32  with its threaded hub  34  and the separate end piece  22  these may be integrated i.e. such that the needle has an integral hub which, like the end piece  22 , is a push fit on the end portion  6  of the barrel  1 .