Cutting element for a retracting needle syringe

(54) Title: CUTTING ELEMENT FOR RETRACTABLE NEEDLE SYRINGE (30) Unionist Priority: 12/05/2005 us 11 / 294,256 (73) Holder (s): becton dickinson and company (72) Inventor (s): Andrew Summerville , Christina J. DArrigo, Jon Swenson (74) Attorney (s): NELLIE ANNE DANIEL SHORES (86) International Request: pct US2006046139 de

12/04/2006 (87) International Publication: wo 2007 / 067449de

06/14/2007 (57) Summary: cutting element for RETRACTABLE NEEDLE syringe. A cutting element for a retractable needle syringe (20) having a plunger (23) with a cuttable distal end and a spring oriented needle (83) held by a cuttable holder. The cutting element (43), capable of cutting the cuttable distal end and the cuttable support, includes a body part (44) having a proximal end (45), a distal end (46), a side wall (47) between them and a passage (50) therethrough. The distal end (46) of the body part (44) includes a cutting edge (48) and an elevated tooth projecting distally (51) having edges converging distally (52). At least one tooth edge includes a sharp side wall (55) for cutting the distal end of the plunger and the needle holder.

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CUTTING ELEMENT FOR NEEDLE SYRINGE

RETRACTABLE

FIELD OF THE INVENTION

The present invention relates to syringe and needle assemblies. More particularly, the present invention relates to a cutting element for a syringe and needle assembly having a structure that allows the needle cannula to be retracted into the syringe barrel after use.

BACKGROUND

In recent years, a growing concern has been raised regarding the transfer of disease, infection and the like to syringe users and healthcare professionals who, accidentally or through negligent manipulation, pierce themselves with hypodermic needles while discarding used hypodermic needle. In many areas in a hospital, where needle cannula products are used, disposal containers are provided so that a syringe or other needle cannula product can be immediately disposed of in a secure, rigid container. However, there are areas of medical practice, such as emergency rooms, where disposal containers may not be readily available or practical, and where products having self-contained safety accessories are desirable. In theory, after such a syringe is used to inject medication or for another purpose, a safety device contained within the syringe or needle assembly is activated to prevent further contact with the sharp tip of the needle. One type of safety syringe includes the structure that allows the hypo2 dermal needle to be retracted into the syringe barrel to minimize the chance of further contact with the sharp needle tip.

The prior art includes retractable needle syringes that include a spring loaded needle assembly 5 that is held in position during normal use of the syringe assembly and a plunger to which it is sealed during normal use of the syringe assembly so that medication or other liquids cannot enter the plunger shaft cavity. These syringes must have a structure to allow release of the spring loaded needle and the opening of the plunger shaft cavity so that the needle can enter the plunger shaft cavity after the syringe is used for_u you intended purpose. To function properly, the cavity in the plunger rod must be sealed so that medication cannot enter the plunger rod during use.

This seal must sometimes withstand high hydraulic pressures when injecting relatively viscous medication through small needles and still be able to be easily opened and allow access by the needle assembly. I20 likewise, the needle assembly must be held firmly in place by the injection forces and still be disengaged so that it can retract into the syringe barrel and into the plunger rod. Some of the prior art retractable needle syringes for solving these problems by providing a leak-proof physical structure to hold the spring loaded needle in position and to seal the hollow plunger rod end. At the conclusion of the injection process, distally directed additional force is applied to the plunger by making an internal cutting element cut through the end of the coiled plunger rod and the spring loaded needle holder. In some embodiments, the retractable needle syringe cutter cuts in a proximal direction through the spring loaded needle mount and then through the distal end of the plunger rod. In both cases this allows the spring loaded needle to enter the plunger cavity helping to keep the user safe from accidental needle punctures.

The retractable needle syringes of the prior art, which have displaceable elements or the breaking of frangible barriers that will allow the spring loaded needle to enter the plunger, may require a wide range of forces to disengage the spring loaded needle. Retractable needle syringes with the cutter have an inherent advantage of being able to be made so that the forces required to activate the retractable needle are more consistent from syringe to syringe.

The present invention deals with an improved cutting element for a retractable needle syringe to provide a much more consistent syringe for syringe activation forces and, if desired, less activation forces.

SUMMARY OF THE INVENTION

A cutting element is provided for a retractable needle syringe having a plunger with a cutable distal end and a spring oriented needle maintained in an energized state by a cuttable holder. The cutting element is capable of cutting the distal cutable end of the plunger and the cuttable support. 0 The cutting element includes a body part having a proximal end, a distal end, a side wall between them defining a longitudinal axis and a passage therethrough. The distal end of the body part includes a cutting edge and a raised tooth projecting distally having a distal tip and edges converging distally. At least one tooth edge includes a sharp side for cutting the distal end 10 of the plunger and the support.

The sharp side wall can include a beveled edge. The cutting element may include a plurality of cutting teeth which may or may not be equally spaced around the distal end of the body part.

The edges converging distally from the cutting tooth may meet to form a distally directed point or not meet and define a distally directed edge at the distal tip.

The cutting element can be configured so that the cutting teeth include two sharp sides for cutting. The cutting teeth can be separated by concave cutting edges moving along the distal end of the body part.

For cutting elements having two or more teeth, the cutting edges between the cutting teeth can be about the same height when measured along the longitudinal axis or the cutting edges can be at different heights when measured along the longitudinal axis cutting element.

For cutting elements having two or more teeth, the distal tips of each cutting tooth can be of the same height when measured along the longitudinal axis or the distal tips can be at different heights when measured along the longitudinal axis of the element cutting.

The body part of the cutting element 10 can be cylindrically shaped. In addition, the cutting element is configured so that it has three teeth or four teeth.

The cutting element is desirably made of metal and preferably made of stainless steel.

In another embodiment of the present invention, the cutting element for a retractable needle syringe having a plunger with a cuttable distal end and a spring oriented needle maintained in an energized state by a cuttable holder is provided. The cutting element is capable of cutting the cutable distal end of the plunger and the cutable support. The cutting element which includes a cylindrically shaped laminated metal body part has a proximal end, a distal end, a side wall between them defining a longitudinal axis and a passage therethrough. The distal end of the body part includes a chamfered cutting edge and at least three tapered cutting teeth projecting distally having a distal tip and chamfered cutting edges converging distally meeting to form a distally directed point on the distal cutting tip. The chamfered cutting edge at the distal end of the body part is concave shaped in the spaces between the teeth which are substantially evenly spaced around the distal end of the body part.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of a retractable needle syringe.

Figure 2 is an exploded perspective view of the retractable needle syringe of Figure 1.

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<td>versai</td><td>syringe</td><td>needle</td><td>retractable</td><td>of the Figure</td><td>1, taken at</td>

<td>long</td><td>line 3-3.</td><td></td><td></td><td></td><td></td>

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<td>versai</td><td>increased from</td><td colspan="2">external hub</td><td>assembly i</td><td>re-needle</td>

tractable '.

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<td> 20</td><td>tractable.</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

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<td> 25</td><td></td><td></td><td></td><td>The figure</td><td> 8</td><td>is</td><td>section view</td><td>trans-</td>

on the distal end of the retractable needle syringe of Figure 1 illustrating the syringe after the liquid contained therein has been dispensed.

Figure 9 illustrates the syringe of Figure 8 when the proximal and distal parts of the plunger rod were repaired and the cutting element cut through the plug and the inner hub.

Figure 10 illustrates the syringe of Figure when the cutting element has cut completely through the inner hub and the needle has been retracted into the plunger.

Figure 11 is a perspective view of a prior art cutting element for the retractable needle 10 syringe.

Figure 12 is a side elevation view of the cutting element of Figure 11.

Figure 13 is a side elevation view of a cutting element of the present invention.

Figure 14 is a perspective view of the distal end of the cutting element of Figure 13.

Figure 15 is a perspective view of the distal end of a preferred cutting element for a retractable needle syringe of the present invention.

Figure 16 is a perspective view of the distal end of an alternative cutting element of the present invention.

Figure 17 is a perspective view of the distal end of another alternative cutting element 25 of the present invention.

Figure 18 is a side elevation view of the distal end of yet another alternative cutting element of the present invention.

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<td>tender</td><td>of this</td><td colspan="2">invention.</td><td></td><td></td><td></td><td></td><td></td>

<td>DESCRIPTION</td><td>DETAILED</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td> 5</td><td colspan="2">While</td><td colspan="2">it is</td><td colspan="3">invention is satisfied</td><td>pe-</td>

the modalities in many different forms are shown in the drawings and will be described in detail here, the preferred modalities of the invention with the understanding that the present description should be considered exemplary of the principles of the invention and are not intended to limit the scope of the invention to the illustrated modalities . The scope of the invention will be measured by the attached claims and their equivalents.

Referring to Figures 1-17, an operable retractable needle syringe 20 includes a retractable needle assembly a15 21, a syringe barrel 22 and a plunger 23. The barrel includes an inner surface 25 defining a chamber 27, a proximal end 28 and a distal end 29 including a cylindrical collar 31 having an outer surface 32 and an inner surface 33.

0 The plunger is slidably positioned in a fluid-proof engagement with the inner surface of the drum. The plunger preferably includes a proximal part 37 having a distal end 38 with an elongated cavity 39 therein.

A cutting element 43 is positioned at the distal end 38 of the proximal part of the plunger 23. The cutting element 43 includes a body part 44 having a proximal end 45, a distal end 46, a side wall 47 between them defining an axis longitudinal 49 3 and a passage 50 therethrough. The distal end 44 includes a cutting edge 48 and at least one distally protruding cutting tooth 51 having a distal tip

53 and edges converging distally 52. ​​at least one tooth edge includes a sharp side wall 55. The tooth cutting element is an important device of the present invention that offers advantages over prior art cutting elements that have a planar cutting edge perpendicular to or at an angle to the longitudinal axis of the cutting element. This advantage will be discussed in more detail later here. As best illustrated in Figure 13, the distal tip 53 of each cutting tooth is preferably about the same height when measured along the longitudinal axis as indicated by the letter B. Additionally, the cutting edges may or may not be at same height when measured along the longitudinal axis. In this embodiment, the cutting edges 48 are at substantially the same height, as indicated by the letter A, when measured along the longitudinal axis.

A distal hollow part 65 of the plunger 23 is reliably connected to the proximal part 37 and capable of telescopic movement with respect to the proximal part. A cover element in the distal part seals a distal end 67. In this embodiment, the cover element is the plug 25 70. It is preferred that the cover element is made of an elastomeric material selected from the group of thermoplastic elastomers, natural rubber, rubber synthetic and combinations thereof. The cover member can also be thermoplastic or a combination of thermoplastic support material and elastomeric material.

The retractable needle assembly 21 includes an outer hub 71 having a proximal end 73, a distal end 74 and a passage 75 therethrough. The retractable needle assembly also includes an inner hub 76 having a proximal end 77, a distal end 79 and a conduit 80 therethrough. The inner hub includes an inner portion 81 and a cutable outer portion 82 connected to the inner portion. The cuttable outer part of the inner hub is connected to the outer hub 71. The distal end 79 of the inner hub is smaller than the passageway 75 of the outer hub at the distal end 74 and is accessible therefrom and preferably projects distally outwardly from the same hub.

A needle cannula 83 has a distal end 85, a proximal end 86 and a lumen 87 therethrough. The proximal end of the cannula is connected to the distal end 79 of the inner hub so that the 20 lumen is in fluid communication with conduit 80 of the inner hub. The distal end of the cannula preferably includes a sharp distal tip.

An energized spring is contained between the inner and outer hubs and in this preferred embodiment the energized spring 25 is a compressed spiral spring 88. Various types of spring and elastomeric and similar materials can be used to provide a guiding force between the inner and outer hubs The spiral spring is merely representative of these many possibilities, all of which are within the scope of the present invention. A spiral spring is preferred due to its compact size and the ability to easily design the spring to provide the forces necessary for proper operation of the retractable needle assembly.

During assembly, the spiral spring is placed on the inner part of the inner hub and then the distal end of the spring is positioned on the outer hub and the inner and outer hubs are moved towards each other to compress the spring and lock them together through the projection action of annular locking 78 in the inner hub and recess of annular locking 72 in the outer hub. When the inner hub and the outer hub are joined, compressing the spiral spring, the annular locking projection on the inner hub fits into the annular locking recess 72 on the outer hub. The projection and the recess are formatted so that much less force is required to assemble the components that invert the process, thus providing a permanent locked condition in which the inner hub and the outer hub are inseparable during normal operating conditions. There are numerous ways of connecting the internal and external hubs, and the pressure fitting arrangement shown here is merely representative of all of these methods that are within the scope of the present invention. In particular, adhesives, separate metal locking clips, ultrasonic welding, crimping, internally molded locking structure and the like, can be used to hold the inner hub and outer hub together.

A preferred way of connecting the needle cannula to the retractable needle assembly is to place the proximal end of the needle cannula at the distal end of the conduit 80 of the inner hub. An enlarged or irregular part 84 at the distal end of the conduit 80 provides a space for adhesive 89 to be placed around the outside of the needle cannula after it is positioned in the conduit.

The retractable needle assembly also includes means for connecting the outer hub to the syringe barrel collar 10. In this modality, half-pope to connect includes the structure that provides threadable coupling between the collar and the external hub. In this preferred embodiment, the threadable engagement structure includes at least one thread 90 in the passage 75 of the outer hub 71 and at least one thread 34 on the outer surface 32 of the cylindrical collar. Thus, the needle assembly, in this embodiment, is removably connected to the drum. This aspect allows the flexibility to change needle and syringe assemblies to obtain an appropriate syringe and needle combination. sized for the type of drug and injection site desired. In addition, the structure of this modality allows the installation and removal of the needle assembly from the drum using the same movements required for the installation and removal of a standard hypodermic needle from a standard hypodermic syringe so that no additional training is required for the worker health care.

The structure for threadable engagement between the collar and the outer hub can include a wide variety of thread-type and bayonet-type structures including a thread on the outer surface of the collar and a thread follower projection on the inner surface of the outer hub that will follow the collar thread when the hub is screwed into the collar. This structure is similar to the well-known locking luer needle assembly and syringe combinations in which the syringe collar has a thread on its inner surface and the needle assembly has two outward projections at the base of its hub to allow that the hub follow the threads of the collar when it is screwed into the luer tip and paste. The inside of the collar may also have thread followers.

It is also within the scope of the present invention to include means for connecting the outer hub to the collar which is permanent rather than removably engaging. For example, the outer hub can be attached to the collar for adhesive, or ultrasonic welding, retaining clips or a one-way snap fit arrangement that makes assembly irreversible under normal use. Such structures are within the scope of the present invention.

It should be noted that the needle assembly does not have to be removable or separate from the drum. Drum elements and needle assembly can be optimized to reduce the number of parts and obtain a permanently attached needle assembly.

To help prevent leakage, this embodiment includes the tapered cylindrical surface 91 on the inner hub 76 and the tapered cylindrical surface 35 within the cylindrical collar 31 of the drum. When the retractable needle assembly engages the drum collar, the tapered cylindrical surface 35 on the collar engages the tapered cylindrical surface 69 on the inner hub to seal the interface between the hub and the collar to prevent leakage during normal use. A gasket can also be used to seal some of the contact surfaces between the needle assembly and the drum.

In use, the retractable needle assembly of the present invention can be removably attached to the syringe barrel 22 containing the plunger 23. A needle shield 93 can now be removed from the retractable needle assembly thereby exposing the needle cannula for use. The retractable needle syringe can be filled, using known methods for such uses as withdrawing liquid injectable from a vial having a pierceable plug. A syringe can then be used to inject liquid into a patient, an IV set, a catheter or other suitable device. After the liquid in the chamber is injected or otherwise distributed, the distal end of the buffer will be in contact with the distal end of the drum chamber as best illustrated in Figure 8. At this point, the user can apply additional distally directed axial force to the proximal end of the plunger through the proximal flange 41 to lower the plug at the distal end of the drum chamber and cause disengagement of the proximal part 37 of the plunger from the distal part 65 of the plunger. Because the connection between the proximal part of the plunger and the distal part of the plunger is broken or overcome, the proximal part will move distally within the distal part and along the tube advancing the cutting element 42 so that its sharp distal end will press and will cut the plug 70 and through the inner hub between the inner part 81 and the cutable outer part 82, as best illustrated in Figure 9. Applying a distally directed force to the plunger that causes the release element to cut completely through the inner hub, will allow the spring to drive the inner part of the inner hub along which the needle cannula in the elongated cavity of the plunger as best illustrated in Figure 10. The used needle cannula is now safely contained within the syringe assembly and ready for safe disposal.

In this embodiment, the releasable connection between the proximal part 37 of the plunger and the distal part 65 of the plunger that allows the relative telescopic movement between the two parts of the plunger is provided by a pressure fitting arrangement between the proximal part of the plunger and the part away from the plunger. In particular, an annular projection 68 within the proximal end of the distal part 65 of the plunger engages an annular groove 40 at the proximal end of the proximal part 37 of the plunger. When sufficient axial force is applied, the annular projection 68 disengages from the annular groove 40 allowing the distal end of the release element to cut through the plug and the inner hub between the cuttable outside and the inside. There are numerous structures and materials and elements that can provide a releasable connection between the proximal and distal parts of the plunger with the structure shown here above being merely representative of the many probabilities, all of which are within the scope of the present invention. In particular, any combination of projections and / or recesses and / or discontinuities in the proximal and distal parts can achieve a similar result. Also, the connection can also be breakable as well as detachable such as by using a frangible adhesive between the two elements or molding the elements as an integral structure containing a brittle plastic projection or projections that join the elements and can be broken with a force applied with a cliff pin. A cliff pin 10 may be made of plastic with one or more notches or tension risers properly placed to cause the desired strength levels to be disrupted. A ruptured connection can also be made similar to the pressure fitting arrangement in drawing the various projections and recesses 15 to fail to reach the desired voltage level. Also, it should be noted that a one-piece plunger is possible if the plug is designed to flex on a fixed cutting element when excess force is applied to the plunger.

A cutting element of the prior art 143 is polished in Figures 11 and 12. The cutting element includes a proximal end 145, a distal end 146 and a side wall 147 between them. The distal end 146 further includes a cutting edge 148. The prior art cutting elements are essentially cylindrical in shape 25 having a circular and planar cutting edge. The cutting edge is typically perpendicular to the longitudinal axis of the cutting element so that the first contact of the cutting element is the inner surface of the plug, or needle holder element, depending on the design, is a full circular contact. When pressing against the plug interface, the cutting mechanism is a slotted mechanism, in which the circular edge of the cutter penetrates directly into the internal surface of the plug. There is no sliding component for cutting. This type of action requires a very sharp edge so that the load required to make the cut ^zeg minimized. A laminated metal cutting element, depending on the manufacturing process used in this formation, can be reasonably sharpened when done. However, a post-training sharpening process is required. Additionally, the cutter is hardened so that the very thin edge does not deform during the cutting process. Contact cutters tend to experience a wider range of cutting forces possibly associated with dimensional and material variations and cutting element sharpening. Forming the planar cutting edge at an angle to the longitudinal axis can reduce the cutting component of the cutting force.

The cutting element of the present invention offers a more robust design that does not necessarily require heat treatment or post-formation sharpening operations and reduces the potential to have wide variations in forces required to obtain the cut of the plug and needle support structure The cutting mechanism of the cutting element of the present invention is not primarily a chisel but one for drilling and shearing. The cutting edge geometry of the cutting element of the present invention is not a circular plane but preferably pointed crown geometry. By changing the mechanism by which the cutter operates, the cutting force is reduced and thus sharpening of powders is necessary -formation and heat treatment.

Figure 15 illustrates the distal end of a preferred cutting element 243 of the present invention. The cutting element 2453 includes a body part 244 having a distal end 246 and a generally cylindrical side wall 247 defining a passage 250 therethrough. The distal end includes the cutting edge 248 and three tapered cutting teeth projecting distally 251 having distally converging edges 252. In this embodiment all three cutting teeth have a sharp side wall in the form of beveled edges 257. Each cutting tooth includes a distally directed point 258. The cutting teeth in this embodiment are substantially evenly spaced around the distal end of the body part and are separated by concave cutting edges 262, that is, the cutting edge is concave shaped in the spaces between the cutting teeth.

The pointed geometry of the teeth together with the pointed chiseled profile of each of the points creates an initial contact against the target surface with a very low surface area. When a force is palisated, the load divided by the surface area defines the penetration stress. Since the surface area is close to zero, the penetration stress is very high and capable of penetrating a target with only a very small charge compared to the cutting elements of the prior art. Once penetration is established, the sharp beveled edges of the cutting teeth slice the target material instead of slicing it. The applied force is therefore administered over a greater distance along the longitudinal axis, thus requiring less force to trim the equivalent work performed. Near the end of the cut, the target material is accumulated between the roots of the cutting teeth, and the final part of the cutting action actually becomes a cut, but the amount of material left is relatively small so that the force required for completing the cut is minimized.

The cutting element of the present invention can be adjusted to provide a number of different sensations while cutting based on the number of cutting teeth, the depth, the teeth, the shape of the points, the shape of the roots between the teeth and the formation of a chisel edge on the profile of each cutting tooth. Based on these variations, a very soft sensation, a very hard sensation or countless internal sensations can be produced.

Figure 16 illustrates an alternative cutting element of the present invention. In this embodiment, the cutting element 343 includes a body part 344 having a distal end 346 and a generally cylindrical side wall 347 defining a passage 350 therethrough. The distal end includes the cutting edge 348 and four tapered cutting teeth protruding 351 having edges converging distally 352. In this embodiment all four cutting teeth have a sharp side wall in the form of chamfered edges 357. Each cutting tooth includes a point distally directed 358. The cutting teeth in this embodiment are substantially equally spaced around the distal end of the body part and they are separated by the concave cutting edges 361, that is, the cutting edge is concave shaped in the spaces between the cutting teeth.

Figure 17 illustrates another embodiment of the present invention. In this embodiment, the cutting element 443 includes a distal end 446, a side wall 447 and a passage 450 through the cutting element. The cutting element in this embodiment includes six tapered cutting teeth projecting distally high 451 having distally converging edges 4 52 ending in a distally directed cutting edge 459. In this embodiment, all six cutting tooth edges have sharp side walls in the form of beveled edges 457. The distally directed cutting edge 459 also preferably includes a beveled cutting surface 4623. The distally directed cutting edge may be desirable. over a cut point in situations where the force required to start the cut is desired to be greater than that possible with the pointed cut tooth.

As indicated above, near the end of the cut, the target material contacts the cutting edges between the cutting teeth in which the final part of the cutting action becomes a size. The amount of material remaining is relatively small so that the force required to complete the cut is minimized. The force is further minimized by having concave cutting edges that further reduce the amount of material that must be cut using a chiselling action. The strength of this final carving action can also be reduced by changing the cutting edges as illustrated in the embodiment of Figure 18. In this embodiment, the cutting element 543 includes a distal end 546, a side wall 5467 and one pass through it. The cutting element in this embodiment includes six tapered cutting teeth projecting distally high 551 having distally converging edges 552 ending at a distal tip 553. The cutting teeth 10 in this embodiment are substantially equally spaced around the distal end of the body part and are separated by the concave cutting edges 561. at least two of the cutting edges between the cutting teeth are at different heights when measured along longitudinal axis 15 of the cutting element. In this embodiment, at least one cutting edge is positioned at distance C, measured along the longitudinal axis, while at least one other cutting edge is positioned at a different distance D, when measured along the longitudinal axis. Consequently, the cutter's minimum minimum chipping action 20 is alternated to reduce the required cutting force. In this mode, each other cutting edge is at distance C and those cutting edges between are at distance D.

Figure 19 illustrates another embodiment of the present invention. This modality is similar to the modality of the Figure except that the force required for the initial cutting action is reduced by alternating the distal tips of the cutting teeth.

In this embodiment, the cutting element 643 includes an extreme 22 distal medium 646, a side wall 647 and a passage therethrough. A cutting element in this embodiment includes six tapered cutting teeth projecting distally high 651 having edges converging distally 652 ending at a distally directed point 658 at the distal tip. The cutting teeth in this embodiment are substantially equally spaced around the distal end of the body part and are separated by concave cutting edges 661. At least two of the cutting edges between the cutting teeth are at different heights when measured along the longitudinal axis 649 of the cutting element. In this mode, at least one cutting edge is positioned at the distance

And, measured along the longitudinal axis, while at least one other cutting edge is positioned at a different distance «

F, when measured along the longitudinal axis. Also, at least two of the 558 distally directed points are at different heights when measured along the longitudinal axis of the cutting element. In this modality, at least one distally directed point is positioned at distance H, measured along the longitudinal axis, while at least one other cutting edge is positioned at a different distance J, when measured along the longitudinal axis. Consequently, alternating the distally directed points 658 reduces the cutting force during this cutting face but not having all the cutting action started simultaneously.

It is desirable to make the cutting element from metal such as rolled metal and preferably stainless steel. However, any material suitable for cutting through the components of the syringe in question can be used to form the cutting element, such as plastics, ceramics and the like, all of which are within the scope of the present invention. 0 cutting element in the preferred embodiments for the present invention has a cylindrical side wall, however other shapes such as elliptical or multi-sided, such as hexagonal, square and the like are within the scope of the present invention and the illustrated cylindrical body part is merely representative of these many possibilities.

Other retractable needle syringes such as the retractable needle syringe shown in US Patent No. 6,432,087 BI operate in a similar manner to the retractable needle syringe described herein but contain the cutting element at the distal end of the syringe barrel with the cutting edge facing in a proximal direction. In this type of retractable needle syringe, after injection, the user provides an additional distally directed force on the plunger that causes the cutting element to cut through the support structure retaining the energized spring and needle and then through the distal end of the plunger to allow the spring to move the needle into the plunger cavity. The cutting element present is also intended to work on syringes of this type.