DISPOSABLE SYRINGE NEEDLE ATTACHMENT HUB

Abstract: The present invention provides a safety syringe having a syringe cylinder with a proximal end and a distal end, a piston stem for insertion in the proximal end of the cylinder, a needle cannula capable of being retracted in a proximal direction into said syringe cylinder, and a needle cannula attachment hub capable of attachment to the syringe cylinder. An interior configuration of the hub includes an interference portion in an adhesive area of the hub, the adhesive area filled with adhesive to releasably attach the cannula to the hub. The interference portion has a contact surface and a distal surface with the angle between the contact surface and the hub wall less than the angle between the distal surface and the hub wall so that a greater force applied on the cannula in a distal direction is required to separate the cannula from the hub as compared to the force required to be applied on the cannula in a proximal direction to separate the cannula from the hub. In an alternate embodiment the interior configuration of the hub includes a narrow distal portion which may include a plurality of annular grooves and an enlarged well area disposed proximal thereto. The well area and the annular grooves are filled with an adhesive for releasably attaching the needle cannula to the hub. A plug member formed of a relatively soft resilient material may be received within the piston void between a distal end of the piston stem and the needle capturer. The plug member maintains proper alignment of the capturer and seals-off a portion of the lateral port of the needle cannula and the proximal opening of the needle cannula after it has passed through the capturer.

Description: DISPOSABLE SYRINGE NEEDLE ATTACHMENT HUB TECHNICAL FIELD The present invention relates to a disposable safety syringe for injecting medication into a patient, and more particularly to a safety syringe including a retractable needle cannula and an improved means for releasably attaching the cannula to the needle cannula attachment hub. BACKGROUND OF THE INVENTION Disposable hypodermic syringes are routinely used to administer medication to patients, thus presenting the requirement for proper disposal of the used and contaminated needles. In an emergency situation, this requirement sometimes is overlooked by the health care technician, whether for practical reasons or otherwise. Separate procedures for disposal are limited at best, consisting of (i) breaking the needle off in a special container which is separate from the syringe, or (ii) using special equipment to assemble or disassemble the syringe, both of which require extra steps for proper disposal of the contaminated device. Even needles which are broken off still can present a hazard of so-called "needle strikes" to trash removal personnel. The potential for needle strikes to health care technicians and associated personnel can cause a high degree of anxiety and require expensive testing procedures of suspected needle strikes. More and more health care personnel are exposed to the risk of infection with the increasing care requirements of HIV- and AIDS-infected individuals, as, well as the risk of hepatitis B and other infectious diseases. Prior attempts to address safe disposal of contaminated needles by retracting the used needle into the cylinder of the syringe are illustrated by, for example, US Patent 4,995,870 disclosing a structure which requires loosening of the hub in order to release the needle from a plug and thus allow for withdrawal of the used needle into the cylinder of the syringe. While manipulating the hub to allow for the retraction, the technician must either expose his/her hand to the distal end of the used and possibly contaminated needle or use an auxiliary device for covering the tip of the used needle. In US Patent No. 5,382,235 to Sak (the '235 patent), the needle cannula is modified and a deflector member and capturer are retrofit to the syringe in order to safely retract and capture the used needle cannula. As depicted in Figure 1, the '235 patent provides an elongated piston stem 2' of a typical syringe having a distal end flange 4 ' which is engageable within groove 10 of generally hollow rubber piston 8. A capturer 40' is receivable within the hollow portion of rubber piston 8 and retained therein by completion of the attachment of the piston 8 to the flange 4'. The typical syringe also includes a cylinder 12' to the distal end of which a separate needle assembly is removably attachable. The point of attachment typically is provided with a Luer lock-type of connection which is well known to those skilled in the art. The needle assembly is illustrated as comprising the cannula 24' which is modified to have at least one lateral port 30' and a conically shaped deflector member 34', attachable thereto in a generally permanent manner. Cannula 24' also has symmetrical grooves 32 to aid in attachment of the Luer lock-type hub 36', onto the cannula 24' by means of an adhesive. The distal end of cannula 24' is pointed for insertion into the patient and the proximal end thereof is sharpened for piercing of the rubber piston 8 upon complete expulsion of the fluid contained in cylinder 12'. In order to ensure uninterrupted and complete expulsion of fluid from cylinder 12', the extended needle cannula 24' is provided with one or more lateral ports 30' for evacuation of any fluid remaining upon depression of the piston stem 2' near the end of the injection stroke. The needle cannula 24' is attached to hub 36' by means of an adhesive injected between the cannula 24' and interior configuration of hub 36'. In order to permit cannula 24' to retract into cylinder 12' upon completion of the injection stroke, force must be applied on cannula 24' in a proximal direction by pulling on stem 2' once cannula 24' is engaged by capturer 40'. At the same time, care must be taken to ensure a sufficient bond between cannula 24' and hub 36' to prevent inadvertent separation of the cannula 24 ' when force is applied on 24' in a distal direction. That inadvertent separation could result in the needle cannula 24' pulling away from the rest of the syringe which could leave the cannula 24' stuck in the skin or otherwise exposed in a dangerous manner. Difficulties can arise in retractable syringes wherein the adhesive attaching the cannula to the hub is designed to break away to permit the cannula to retract into the syringe cylinder. A weaker adhesive permits ready retraction of the cannula into the cylinder but at the same time increases the risk of cannula separation when force is applied on the cannula in a distal direction. On the other hand, while selection of adhesive which more strongly bonds the cannula to the hub will reduce the risk of inadvertent cannula separation that selection increases the force necessary to retract the syringe into the cylinder which can result in difficulties in securing and retaining the cannula proximal end in the capturer as the plunger is pulled back. In addition, with the plunger assembly design of the '235 patent, it has been observed that residual fluid leakage can occur from a portion of the lateral port 30' and from the proximal opening of the needle cannula at the end of an injection stroke, i.e., just before, during, and after the needle cannula has been retracted into the cylinder. This is due to the proximal end of the needle cannula extending through and protruding proximally of the needle capturer 40' within the void formed in the rubber piston 8. Escaped fluid may remain within the piston void and inside the recess formed at the end of the piston stem, thus causing dead space (space occupied by medicament which cannot be injected) within the syringe. This can result in variance of the injected amount from the prescribed dose, and/or waste of medicament. Also, fluid leaked from the needle cannula may undesirably escape from the void and into the syringe cylinder, distally of the retracted piston. There is a further possibility that during manufacture and subsequent handling of the syringe, the needle capturer will become slightly misaligned within the piston void, with the result that when the proximal end of the needle cannula pierces the piston at the end of an injection stroke, the needle end will be misaligned with the slot between the receiving tabs of capturer 40'. If this happens, the needle cannula may exert an eccentric force on the capturer causing it to tilt within the void of the piston. This makes it difficult for the needle cannula to pass through the capturer slot and may cause the proximal end of the needle cannula to bend. BRIEF SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the prior art while still obtaining the advantages thereof. In one aspect of the invention the hub includes an interference portion in the adhesive area which includes a contact surface facing the proximal end of the syringe and a distal surface facing the distal end of the syringe. The angle between the plane defined by the contact surface and the wall is less than the angle between the plane defined by the distal surface and the wall. Adhesive in the adhesive area releasably attaches the cannula to the hub and contacts the contact surface. A greater force applied on the cannula in the distal direction is required to separate the cannula from the hub, as compared to the force required to be applied on the cannula in a proximal direction to separate the cannula from the hub. In another aspect of the invention a wall in an interior configuration of the hub includes a first portion proximal to the contact surface and a second portion connected to the distal surface the cross-sectional area of the first portion is greater than the cross-sectional area of the second portion. Alternatively an interior configuration of the hub includes a narrow distal needle securing portion and an enlarged well area disposed proximal thereto. The narrow distal portion preferably also includes at least one annular groove. The well area and any annular groove is filled with an adhesive for attaching the hub to the needle cannula. Having adhesive in the well area necessitates a significant force being used to pull the needle in a distal direction, and thereby substantially prevents separation of the cannula in a distal direction while the adhesive in the annular groove necessitates a lesser force being used to separate and pull the cannula in a proximal direction. The adhesive used is also preferably compressible such that, upon pull of the cannula in a proximal direction, the adhesive in the annular groove attaching the needle to the hub means is compressed and pulled away from the groove substantially intact. Thus, the mass of adhesive will remain substantially intact and adhere to the needle cannula when it is retracted into the syringe cylinder. In another aspect of the invention a plug member is received within the void between the distal end of the piston stem and the needle capture member. Preferably, the plug member is formed of a relatively soft resilient material allowing the proximal end of the needle cannula to become embedded therein at the end of the injection stroke, to thereby seal a proximal opening of the needle cannula and a lateral port in the cannula against fluid leakage. The plug member may also be braced against a proximal side of said capture member, thereby serving to retain the capture member in alignment with the piston at a distal end of the void. Various additional advantages and features of novelty which characterize the invention are further pointed out in the Claims that follow. However, for a better understanding of the invention and its advantages, reference should be made to the accompanying drawings and descriptive matter which illustrate and describe preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded view, partially in cross-section, of a prior art disposable syringe with a cannula capturing means; FIG. 2 is an elevational view of the syringe assembly according to a preferred embodiment of the present invention; FIG. 3 is an elevational view of a piston stem of the syringe assembly of FIG. 2.; FIG. 4 is an elevational view of a needle cannula of the syringe assembly of FIG. 2; FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 4; FIG. 6 is a plan view of a capturing device of the syringe assembly of FIG. 2; FIG. 7 is a side elevational view of the capturing device of FIG. 6; FIG. 8 is a side elevational view of a hub of the syringe assembly of FIG. 2 in partial cross section; FIG. 9 is an end elevational view of the hub of FIG. 8; FIG. 10 is an assembled view of the hub of FIG. 8 and the needle cannula of FIG. 4; FIG. 11 is an enlarged detail of a portion of the hub as shown in FIG. 10. FIG. 12 is an enlarged broken-away longitudinal cross-sectional view of the distal end of a modified plunger assembly in accordance with the present invention. FIG. 13 is a side elevational view of a plug member of the plunger assembly illustrated in FIG. 12. FIG. 14 is a bottom plan view of the plug shown in FIG. 13. FIG. 15 is a simplified cross-sectional view of an interior configuration of an alternate embodiment of the hub of FIG. 11. FIG. 16 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. FIG. 17 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. FIG 18 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. FIG. 19 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. FIG. 20 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. FIG. 21 is a simplified cross-sectional view of an interior configuration of a further alternate embodiment of the hub of FIG. 11. DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 2, a syringe assembly according to a preferred embodiment of the present invention is shown generally by reference numeral 50. Syringe assembly 50 includes a typical piston stem 2, a cylinder 12 onto which a Luer lock-type hub 36 is secured at a distal end, a needle cannula 24 attached to hub 36 by means of adhesive (not shown), and a capturing device 40, each of which is explained in greater detail below. In describing the subject invention the term "distal" is used to describe a direction or position toward or at the cannula end of the syringe. The term "proximal" is used to describe a direction or position toward or at the piston stem end of the syringe. Referring to FIG. 3, a piston stem is shown generally by the reference numeral 2. The piston stem 2 of a syringe includes distal end flange 4 that is engageable within groove 10 of generally hollow rubber piston 8 (the piston 8 best seen in FIG. 12). The piston stem 2 includes a reduced thickness notch portion 6 in order to permit the bulk of the piston stem to be broken away from the proximal end after use and the stem has been retracted from the cylinder 10. A hole 11 may be provided in the proximal end of the piston stem to allow extended needle cannula to telescope into the plunger whereby the side port in the cannula may come into engagement with the capturing device. FIGS. 4 and 5 illustrate a stainless steel needle cannula 24 according to the present invention and having at least one lateral port 30. The distal end of cannula 24 is pointed for insertion into the patient and the proximal end 26 may be beveled for piercing of the rubber piston 8 upon expulsion of the fluid contained in cylinder 12. In order to ensure uninterrupted and complete expulsion of fluid from cylinder 12, the extended needle cannula 24 is provided with one or more lateral ports 30 for evacuation of any fluid remaining upon depression of piston stem 2 near the end of its injection stroke, that is with piston 8 positioned near the distal end of cylinder 12. In a preferred embodiment of the present invention, cannula 24 is a twenty-two gage needle with the length of the cannula, including proximal end 26, having a diameter of approximately 0.028". The lateral port 30 defines a reduced cannula circumference and defines a height of approximately 0.020" at the location thereof the height measured from the rounded outer edge of the cannula to the flat inner edge. FIGS. 6 and 7 illustrate a capturing device 40 having a pair of opposed flexible tabs 42 for capturing the needle cannula 24 therein in order to effect capture and subsequent retraction of the cannula 24 into cylinder 12. The opposed edges of the tabs 42 define a longitudinal opening 44 of approximately 0.021" in width. The capturing device 40 is installed within the concavity of piston 8 and retained securely therein by mating flange 4 of the typical stem 2 in piston groove 10. This is best seen in FIG. 12. Thus, after piercing the rubber piston 8, the tabs 42 bend as the larger diameter proximal end 26 of cannula 24 passes through opening 44. Then, when the smaller lateral port 30 is within the opening 44, the tabs 42 bend back to their original location and essentially lock around the port 30 to thereby prevent proximal and distal pull of the needle cannula 24 out of the capturing device 40. Referring to FIGS. 8-11, the Luer lock-type hub 36 according to the present invention is shown in greater detail. The hub is molded polypropylene but other polymer products having the same characteristics are contemplated. Hub 36 includes a proximal flange 46 for engagement with the conventional threaded distal end of cylinder 12, a barrel portion 48, and a narrower needle securing portion 52. Needle securing portion 52 includes one or a plurality of internal annular grooves 54 and an enlarged well area 56 disposed proximally thereto. Well area 56 includes wall 57 forming a first portion 59 at a proximal end and a second portion 61 at a distal end. The distal end of needle securing portion 52 is defined, in part by second portion 61. It can readily be seen from FIG. 8 that the cross-sectional area of first portion 59 is greater than the cross-sectional area of second portion 61. The distal end of well area 56 includes contact surface 63 which faces the distal end 65 of hub 36. Sides of grooves 54 form a distal facing surface 67 generally facing the distal end 65 of hub 36. It should be appreciated that while annular grooves 54 are described it is not necessary for surface 67 to be continuous about the circumference of the needle securing portion 52. Segments of internal grooves can be positioned about the circumference of portion 52 to provide a series of distal facing surfaces 67. As best seen FIG. 8 and 11 , the cross-sectional area of the first portion 59 is greater than the cross sectional area of the second portion 61. An adhesive well area is thereby formed defined by the first portion 59 and the contact surface 63. It can also be seen that the inner angle between first portion 59 and contact surface 63 is approximately 90 degrees whereas the inner angle between second portion 61 and distal facing surface 67 is slightly greater than 180 degrees. Inner angle referring to the angle on the side which receives and contacts the adhesive in adhesive area 81. Thus the inner angle between the plane defined by contact surface 63 and first portion 59 of wall 57 is less than the inner angle between the plane defined by distal facing surface 67 and second portion 61 of wall 57. An adhesive 58 is disposed within the internal grooves 54 and well area 56 in adhesive area 81, as shown by cross-hatched area of FIG. 11, to releasably secure cannula 24 to hub 36. Cannula 24 is positioned co-axially within portion 52 and well area 56. When the grooves 54 and well area 56 are filled with the correct amount of a suitable adhesive, as discussed in detail below, in the correct location, the preferred needle pull-out forces are obtained. That is, contrary to prior art syringes having similar cannula pull-out forces in both the proximal and distal directions, the present invention provides higher distal cannula pull-out forces by placing the adhesive in the well 56, and lower proximal cannula pull-out forces by placing the adhesive in the annular grooves 54 in the needle securing portion 52 of the hub 36. When needle cannula 24 is pulled from the hub 36 the adhesive used to secure the cannula thereto stays substantially intact and attached to the cannula 24, the adhesive chosen adhering to stainless steel but have poor adhesion to the polypropylene hub. Accordingly, distal pull of needle cannula from hub 36 is substantially prevented by adhesive in the well 56 securely holding needle cannula 24 since a high force would be required to overcome adhesive force on the cannula 24 or to compress the adhesive such that it passes through the narrower needle securing portion 52 to be removed with the cannula 24. On the other hand, proximal pull of needle cannula 24 must only overcome the short area of interference fit and adhesive force bonded as the adhesive within the grooves passes through the narrower groove restrictions to the contact surface in order for the needle cannula 24 with the adhesive substantially attached thereto to be pulled proximally into the cylinder 12. Accordingly, the lower proximal pull-out forces provide a smooth release of the needle cannula 24 from the hub 36 when the needle is captured by the capturing device 40 and pulled proximally into cylinder 12. Prior art adhesives used for securing a needle cannula to a hub have generally included heat cured epoxies. Such adhesives are brittle, and if used with the hub 36 of the present invention, a proximal pull-out force applied thereto would likely cause the adhesive to shear off and/or flake, thereby adding contaminants to the needle assembly. Accordingly, a preferred adhesive to be used with the hub 36 of the present invention must be slightly flexible so that it may be compressed during proximal pull-out of the needle cannula and thereby adhere substantially to the needle cannula. Urethane acrylate is a preferred suitable adhesive due to its flexibility, and in particular an adhesive known as ULTRA-LIGHT- WELD™ 1-20271 cannula bonder that is produced by Dymax Corporation of Torrington, Connecticut. Other adhesives produced by Loctite, such as numbers 3102, 3103 and 322, may work equally as well with needle assembly 50, especially number 3102 due to the similarity in viscosity and tensile shear strength. The preferred tensile break strength of the adhesive should be approximately 3300 pounds per square inch with an elongation of approximately 60% at break. The adhesive preferably is non-migratory having a high viscosity, preferably approximately 4000 centipoise or greater, so that it is self-maintained in the area of the needle cannula when it is applied thereto. Lower viscosity adhesives that are typically used in prior art syringes tend to wick down the needle such that the final location of the adhesive is difficult to control. The preferred Dymax adhesive has a viscosity of 4000 cp whereas the Loctite 3102 adhesive has a viscosity of 3750 cp. Similarly, the preferred Dymax adhesive has a tensile shear strength of 3000 psi with a 90% elongation at break whereas the Loctite 3102 adhesive has a tensile shear strength of 2500 psi. Other adhesives having other viscosity values, tensile strength values, and elongation values may of course also be used provided that the objects of the present invention are still achieved. That is, the adhesive must adhere substantially where it is applied to the needle cannula 24 and the adhesive must be sufficiently flexible such that it will compress and stay substantially intact and adhered to the needle cannula 24 when the cannula is pulled out in the reverse direction In use of the invention, the capturing device 40 is installed within the concavity of piston 8 and retained securely therein by mating flange 4 of the stem 2 in piston groove 10 during packaging of the syringe. The packaged syringe has stem 2 at least partially telescoped into cylinder 12. A needle assembly including hub 36 and needle cannula 24 may be pre-assembled or would be packaged with the standard sterility shield 22 for safe handling of the needle assembly during attachment thereof to the distal end of cylinder 12. Once the needle assembly is positioned on the syringe, the protection shield 22 is removed from the cannula 24 for infusing a fluid medicament into the cylinder 12. Upon substantial expulsion of the medicament therefrom, the pointed proximal end 26 of the cannula 24 will pierce the rubber of piston 8 and pass between the flexible tabs 42 to effect capture of the needle cannula 24 within capturing device 40 as described above and telescope into the piston stem. A subsequent proximal force applied to piston stem 2 overcomes the adhesive force adhering the needle to hub 36 such that needle cannula 24 may be retracted and the adhesive pulled free from the walls of the needle securing portion 52 of the hub 36. The contact of the port 30 with the tabs 42 permits the cannula to cant to one side when the needle is fully retracted inside the cylinder. Upon full retraction of piston stem 2, the used needle cannula 24 is safely disposed within the cylinder 12 for appropriate disposal and there is no danger of infection to the health care technician. The piston stem 2 is then snapped off at the break-away notch portion 6 and disposed of. This prevents the piston stem 2 from being easily pulled out of the barrel with the cannula 24 still attached. It also prevents distal pressure being applied to the piston stem 12, causing the retracted needle to be pushed distally and possibly puncturing through the wall of the syringe barrel. Alternate Hub Internal Configuration Embodiments Alternate embodiments of the interior configuration of the hub, as an alternate to the configuration depicted in FIGS> 8-11 will be discussed with specific reference to FIGS. 15- 21. In each of FIGS. 15-21 the distal end of the hub is at the top of the figure and the proximal end at the bottom of the figure. Referring to FIG. 15, cannula 24 is releasably attached to hub 36J by means of adhesive 58 shown by means of cross-hatching in FIG. 15. Hub 36J includes wall 57J which forms a first portion 59J at a proximal end and a second portion 61 J at a distal end. The cross-sectional area of first portion 59J is greater than the cross-sectional area of second portion 61 J. The first portion 59J forms a well area 56J. The distal end of well area 56J includes contact surface 63 J which in the embodiment of FIG. 15 is generally frusto-conical in shape. Contact surface 63J faces the proximal end 69J of hub 36J. In the embodiment of FIG. 15, second portion 61 J is smooth with no annular grooves or other distal facing impediments. In effect, the inner angle of the second portion 61 J and distal surface is 180 degrees and the inner angle between first portion 59J and contact surface 63 J is less than 180 degrees or less than the angle of the second portion 61 J. The adhesive area 81 J is defined by the cross-hatched area depicted in FIG. 15. Adhesive 58 contacting the contact surface 63 J will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65 J of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69J into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 16, cannula 24 is releasably attached to hub 36.2 by means of adhesive 58 shown by means of cross-hatching in FIG. 16. Hub 36.2 includes wall 57.2 which forms a first portion 59.2 at a proximal end and a second portion 61.2 at a distal end. The cross-sectional area of first portion 59.2 is greater than the cross-sectional area of second portion 61.2. The first portion 59.2 forms a well area 56.2. The distal end of well area 56.2 includes contact surface 63.2 which in the embodiment of FIG. 16 is generally perpendicular to first portion 59.2 forming a cylindrical shaped well area 56.2. Contact surface 63.2 faces the proximal end 69.2 of hub 36.2. In the embodiment of FIG. 16, second portion 61.2 includes two annular ridges 73.2 extending into the adhesive area 81.2. Surfaces of ridges 73.2 form a plurality of distal facing surfaces 67.2 facing the distal end 65.2 of hub 36.2. The inner angle of the second portion 61.2 and distal facing surface 67.2 is greater than 90 degrees and the inner angle between first portion 59.2 and contact surface 63.2 is 90 degrees which is less than the angle of the second portion 61.2. and distal facing surface 67.2. The adhesive area 81.2 is defined by the cross-hatched area depicted in FIG. 16. Adhesive 58 contacting the contact surface 63.2 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.2 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.2 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 17, cannula 24 is releasably attached to hub 36.3 by means of adhesive 58 shown by means of cross-hatching in FIG. 17. Hub 36.3 includes wall 57.3 which forms a first portion 59.3 at a proximal end and a second portion 61.3 at a distal end. The cross-sectional area of first portion 59.3 is greater than the cross-sectional area of second portion 61.3. The first portion 59.3 forms a well area 56.3. The distal end of well area 56.3 includes contact surface 63.3 which in the embodiment of FIG. 17 is generally frusto-conical in shape. Contact surface 63.3 faces the proximal end 69.3 of hub 36.3. In the embodiment of FIG. 17, second portion 61.3 includes an annular groove 54.3 in the adhesive area 81.3. Surface of groove 54.3 forms a distal facing surface 67.3 facing the distal end 65.3 of hub 36.3. The inner angle of the second portion 61.3 and distal facing surface 67.3 is greater than 180 degrees and the inner angle between first portion 59.3 and contact surface 63.3 is greater than 180 degrees as well. The adhesive area 81.3 is defined by the cross-hatched area depicted in FIG. 17. Adhesive 58 contacting the contact surface 63.3 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.3 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.3 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 18, cannula 24 is releasably attached to hub 36.4 by means of adhesive 58 shown by means of cross-hatching in FIG. 18. Hub 36.4 includes wall 57.4 which forms a first portion 59.4 at a proximal end and a second portion 61.4 at a distal end. The cross-sectional area of first portion 59.4 is greater than the cross-sectional area of second portion 61.4. The first portion 59.4 forms a well area 56.4. The distal end of well area 56.4 includes contact surface 63.4 which in the embodiment of FIG. 18 is generally frusto-conical in shape. Contact surface 63.4 faces the proximal end 69.4 of hub 36.4. In the embodiment of FIG. 18, second portion 61.4 includes a distal facing surface 67.4 in the adhesive area 81.4. Distal facing surface 67.4 faces the distal end 65.4 of hub 36.4. The inner angle of the second portion 61.4 and distal facing surface 67.4 is slightly less than 180 degrees and the inner angle between first portion 59.4 and contact surface 63.4 is less than 180 degrees and also less than the inner angle of the second portion 61.4 and distal facing surface 67.4. The adhesive area 81.4 is defined by the cross-hatched area depicted in FIG. 18. Adhesive 58 contacting the contact surface 63.4 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.4 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.4 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 19, cannula 24 is releasably attached to hub 36.5 by means of adhesive 58 shown by means of cross-hatching in FIG. 19. Hub 36.5 includes wall 57.5 which forms a first portion 59.5 at a proximal end and a second portion 61.5 at a distal end. The cross-sectional area of the distal region of first portion 59.5 is greater than the cross- sectional area of second portion 61.5. The first portion 59.5 forms a well area 56.5. The distal end of well area 56.5 includes contact surface 63.5 which in the embodiment of FIG. 19 is generally frusto-conical in shape. Contact surface 63.5 faces the proximal end 69.5 of hub 36.5. In the embodiment of FIG. 19, second portion 61.5 includes a distal facing surface 67.5 in the adhesive area 81.5. Distal facing surface 67.5 faces the distal end 65.5 of hub 36.5. The inner angle of the second portion 61.5 and distal facing surface 67.5 is slightly less than 180 degrees and the inner angle between first portion 59.5 and contact surface 63.5 is less than 90 degrees. The adhesive area 81.5 is defined by the cross-hatched area depicted in FIG. 19. Adhesive 58 contacting the contact surface 63.5 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.5 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.5 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 20, cannula 24 is releasably attached to hub 36.6 by means of adhesive 58 shown by means of cross-hatching in FIG. 20. Hub 36.6 includes wall 57.6 which forms a first portion 59.6 at a proximal end and a second portion 61.6 at a distal end. The cross-sectional area of first portion 59.6 is greater than the cross-sectional area of second portion 61.6. The first portion 59.6 forms a well area 56.6. The distal end of well area 56.6 includes contact surface 63.6 which in the embodiment of FIG. 20 is generally perpendicular to first portion 59.6 forming a cylindrical shaped well area 56.6. Contact surface 63.6 faces the proximal end 69.6 of hub 36.6. In the embodiment of FIG. 20, second portion 61.6 is smooth with no annular grooves or other distal facing impediments. In effect, the inner angle of the second portion 61.6 and distal surface is 180 degrees and the inner angle between first portion 59.6 and contact surface 63.6 is 90 degrees or less than the angle of the second portion 61.6. First portion 59.6 includes two annular grooves 54.6 in the adhesive area 81.6. Surfaces of grooves 54.6 form a distal facing surface 67.6 facing the distal end 65.6 of hub 36.6. The adhesive area 81.6 is defined by the cross-hatched area depicted in FIG. 20. Adhesive 58 contacting the contact surface 63.6 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.6 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.6 to overcome adhesive contacting distal facing surface 67.6 to pull cannula 24 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Referring to FIG. 21, cannula 24 is releasably attached to hub 36.7 by means of adhesive 58 shown by means of cross-hatching in FIG. 21. Hub 36.7 includes wall 57.7 which forms a first portion 59.7 at a proximal end and a second portion 61.7 at a distal end. The cross-sectional area of the first portion 59.7 is equal to the cross-sectional area of second portion 61.7. The first portion 59.7 forms a well area 56.7. The distal end of well area 56.7 includes contact surface 63.7 which in the embodiment of FIG. 21 is generally cylindrical in shape. Contact surface 63.7 faces the proximal end 69.7 of hub 36.7. In the embodiment of FIG. 21, second portion 61.7 includes a distal facing surface 67.7 in the adhesive area 81.7. Distal facing surface 67.7 faces the distal end 65.7 of hub 36.7. The inner angle of the second portion 61.7 and distal facing surface 67.7 is greater than 90 degrees and the inner angle between first portion 59.7 and contact surface 63.7 is about 90 degrees. The adhesive area 81.7 is defined by the cross-hatched area depicted in FIG. 19. Adhesive 58 contacting the contact surface 63.7 will result in a greater force required to separate the cannula from the hub when pulled in a distal direction toward distal end 65.7 of the hub. A lesser force is required to pull the cannula 24 in a proximal direction toward proximal end 69.7 against the force of adhesive 58 contacting distal facing surface 67.7 into the syringe cylinder (not shown) in order to dispose of the syringe in a safe manner after use. Adhesive Application In order to ensure that the adhesive is properly applied in the correct location, the preferred method of applying the adhesive and fixing the needle cannula 24 to the hub 36 is described below. A rack capable of holding one or a plurality of hubs is first horizontally positioned on a table top. The hub rack is designed to locate the cannula in the correct location relative to the hub and to minimize angularity of the cannula in the hub. Hubs are loaded onto the hub rack and slid down onto the hub rack face. The needle cannula 24 is slid into the hub 36 through the distal end thereof, the proximal end 26 of the needle being inserted first. The hub is then slid forward toward the distal end of the needle, being careful not to damage the point of the needle. An automatic adhesive dispensing system is adjusted and fixtured so that the correct drop size (approximately 0.020 cc) of adhesive is dispensed onto the cannula at the proper location as measured from the proximal end of the cannula. The hub is slid proximally along the needle and moved into place seated on the hub rack face. The hub should be moved axially along the needle and not twisted or rotated during the sliding process. The hub rack is then moved to an apparatus for ultra-violet light curing of the adhesive. A conveyor system with a fusion ultra-violet light curing system is preferably used, such as the UVC conveyor cure system UVC-6 of Dymax Corporation of Torrington, Connecticut utilizing Dymax' s 5000-EC UVNisible flood lamps. After curing, the proximal end of the needle cannula may be lightly pulled to check for any looseness and to confirm proper curing of the adhesive and the entire assembly should be visually inspected to ensure that there is no excess adhesive. Plug Member Referring now to Figs. 12-14, a modified plunger assembly of the invention is described. The elements of this embodiment also present in the first embodiment are identified with corresponding reference numbers. The modified assembly differs from the first in that the former includes a plug member 101 situated between the distal end of piston stem 2 and capturing device 40. Preferably, plug member 101 has an elongated cylindrical stem 103 which fits snugly within central recess 105 provided within piston stem 2, and an enlarged semi-spherical head portion 104 that nests within the cup-shape of capturer 40. A flat annular underside of the head portion 104 mates tightly against the end surface of stem 103 surrounding the outlet of recess 105. By substantially filling-up the space between the proximal surface 71 of capturer 40 and the distal end of piston stem 2, plug member 101 provides a mass within which the proximal end of needle cannula 24 can become embedded after it has passed through and become locked in capturer 40. In this manner, plug member 101 serves to seal-off the portion of the lateral port 30 of needle cannula 24 which extends below the capturer 40 and the proximal opening of the needle cannula to thereby eliminate the possibility of residual fluid leakage. Plug member 101 should have a length sufficient to seal-off port 30 along its length. The material of plug member 101 should be relatively soft and resilient so as to reduce the required additional force to penetrate the material to an imperceptible level. The material should tear rather than core upon penetration of the needle end, to prevent the material from entering the cannula during the injection stroke. Resiliency is important to ensure maintenance of a liquid-tight interface between the needle cannula and plug member under the fluid pressures generated during injection. In a preferred embodiment, plug member 101 is injection molded from commercial or medical grade silicone rubber or other commercial or medical grade elastomer with a Shore 30A hardness. Compression molding may also be used to produce the plug. It is preferable to have plug member 101 slightly oversized with respect to the space between the distal end of stem 103 and the proximal surface 71 of capturer 40. In this manner, upon assembly, plug member 101 is braced against the proximal surface 71 of capturer 40, thus serving to securely retain the capture member in proper centered alignment with the piston at the distal end of the piston void. Thus, it will be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the construction set forth without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For instance, although the invention has been described with respect to removably attachable needle assemblies, it is also contemplated that similar adaptations may be made to those needle assemblies which are affixed to be integral with the syringe. It is to be understood also that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims: CLAIMS 1. A safety syringe having a syringe cylinder with a proximal end and distal end, a piston stem for insertion in the proximal end of the cylinder, a needle cannula for attachment to the distal end of the cylinder the cannula capable of retraction into the cylinder and a needle cannula attachment hub capable of attachment to the distal end of the cylinder, the hub comprising : (a) an adhesive area for receiving adhesive to releasably attach the cannula to the hub, the adhesive area having a wall; (b) an interference portion in the adhesive area comprising a contact surface facing the proximal end of the syringe and a distal surface facing the distal end of the syringe, the inner angle between the plane defined by the contact surface and the wall is less than the inner angle between the plane defined by the distal surface and the wall; and (c) adhesive in the adhesive area releasably attaching the cannula to the hub and contacting the contact surface and distal surface; whereby a greater force applied on the cannula in the distal direction is required to separate the cannula from the hub as compared to the force required to be applied on the cannula in a proximal direction to separate the cannula from the hub. 2. A safety syringe according to Claim 1 wherein the wall has a first portion proximal to the contact surface and a second portion connected to the distal surface, the cross-sectional area of the first portion being greater than the cross-sectional area of the second portion to form an adhesive well area defined by the first portion and the contact surface. 3. The safety syringe according to Claim 2 wherein the second portion further comprises at least one annular groove. 4. The safety syringe as described in Claim 1 wherein the adhesive preferentially bonds to metal in preference to non-metal material. 5. The safety syringe as described in Claim 2 wherein the adhesive preferentially bonds to metal in preference to non-metal material. 6. The safety syringe as described in Claim 3 wherein the adhesive preferentially bonds to metal in preference to non-metal material. 7. The safety syringe according to Claim 2 wherein the second portion comprises at least one annular ridge extending into the adhesive area. 8. The safety syringe according to Claim 2 wherein the angle between the plane defined by the contact surface and the first portion is about 90 degrees. 9. The safety syringe according to Claim 2 wherein the angle between the plane defined by the contact surface and the first portion is greater than 90 degrees and less than 180 degrees. 10. The safety syringe according to Claim 2 wherein the angle between the plane defined by the distal portion and the second portion is about 180 degrees. 11. The safety syringe according to Claim 2 wherein the first portion is angled inwardly in a proximal direction such that the cross-sectional area defined by the first portion adjacent the contact surface is greater than the cross-sectional area defined by the first portion in a region further proximal to the contact surface. 12. The safety syringe according to Claim 2 wherein the wall further comprises at least one annular groove. 13. The safety syringe according to Claim 1 further comprising a plunger assembly comprising: a piston mountable on a distal end of said piston stem, said piston having a void formed therein; a needle capture member received within said void, said needle capture member being arranged such that, in use, a proximal end of the needle cannula is passed through and secured within the capture member at the end of an injection stroke; and a plug member received within said void between the distal end of the piston stem and the needle capture member. 14. The plunger assembly according to Claim 13, said plug member being formed of a relatively soft resilient material allowing the proximal end of the needle cannula to become embedded therein at the end of said injection stroke, to thereby seal a proximal opening and lateral port of said needle cannula against fluid leakage. 15. The plunger assembly according to Claim 14, wherein said plug member is formed of a material having a Shore 30A hardness. 16. The plunger assembly according to Claim 14, wherein said plug member is formed of a material selected from the group consisting of commercial or medical grade silicone rubber and commercial or medical grade elastomer. 17. The plunger assembly according to Claim 13, wherein said plug member is braced against a proximal side of said capture member, thereby serving to retain said capture member in alignment with said piston at a distal end of said void. 18. The plunger assembly according to Claim 13 wherein said plug member is mounted on the distal end of said piston stem. 19. The plunger assembly according to Claim 18, wherein said piston stem has a recess formed at its distal end and said plug member is secured within said recess. 20. The plunger assembly according to Claim 19, said plug having a stem portion received within said recess and an enlarged head portion abutting a proximal side of said capture member. 21. The plunger assembly according to Claim 13, wherein said capture member is formed as a cup-shaped member opening proximally, and said plug member extends within said cup- shape member. 22. The plunger assembly according to Claim 21, wherein said plug member substantially fills the cup-shaped member. 23. The plunger assembly according to Claim 21, wherein a proximal surface of said cup- shape member includes flexible needle capturing tabs formed therein. 24. The plunger assembly according to Claim 13, wherein said piston stem has a flange at a distal end thereof and said piston presents a concavity facing proximally of said syringe and a groove in an internal surface of said concavity, said groove being engageable by said flange to facilitate attachment of said piston to said stem while leaving said void generally defined by said stem distal end and said internal surface of said concavity.

Inventors: FARRAR QUINTON JAMES, PADGETT MARY BETH BLAIR, FARRAR, QUINTON, JAMES, PADGETT, MARY, BETH, BLAIR
Applicants: FARRAR QUINTON JAMES, PADGETT MARY BETH BLAIR, RMS MEDICAL SYSTEMS INC, FARRAR, QUINTON, JAMES, PADGETT, MARY, BETH, BLAIR, RMS MEDICAL SYSTEMS INC.
Application year: 1998
Main classification: A61M5
IPC codes: A61M5