WO2014008601A1

WO2014008601A1 - Medicament-actuated safety syringe

Info

Publication number: WO2014008601A1
Application number: PCT/CA2013/050536
Authority: WO
Inventors: Ryan Lee; Mark Drlik
Original assignee: Magne, Luc
Priority date: 2012-07-10
Filing date: 2013-07-10
Publication date: 2014-01-16

Abstract

A hydraulically actuated capsule for use with a dental syringe is provided. The capsule has a cover that can reciprocally cover, uncover and re-cover the syringe needle. A piston is urged upward in a cylinder to release a latching mechanism on the cover. As the cover is biased towards the uncovered position, once the latching mechanism is released, the cover will automatically slide proximally. After use, the user slides the cover distally and then removes the capsule. A dental syringe with the capsule is also provided.

Description

MEDICAMENT-ACTUATED SAFETY SYRINGE BACKGROUND OF THE INVENTION

Field of the Invention

The present technology is related to dental syringes. More specifically, the technology is a disposable capsule for use on a standard dental syringe to provide a patient-friendly safety syringe that can easily be deployed with one hand as movement of the cover is actuated by the medicament.

Description of the Related Art

There are many designs for safety syringes. Some allow for the needle to be covered prior to use, others cover the needle after use, some break the needle after use and some have a number of needle positions. US 7,637,889 discloses the use of fluid pressure to expose and re-cover the needle, as follows "When plunger is pulled to the left, the liquid medication from a vial will pass through piercer to reservoir and fill reservoir. A one way valve prevents liquid medication from flowing back into the vial. When plunger is next pushed to the right toward valve the medication in full reservoir acts as a moving piston to push against sliding through valve and pushes valve against spring to compress the spring until it stops at an open valve position. Needle has advanced concurrently with valve and has opened or passed through gate.

"Next, when plunger is pushed further to the right (pushed in further) the medication in reservoir is moved out of the reservoir, through open valve and out needle, to deliver the medication directly to the patient or otherwise. As soon as the nurse or other user releases the push pressure on plunger, the spring automatically pushes the valve back to its closed position, moves the needle back and gate automatically closes." US Patent Application 2011/0054398 discloses lock members that hold a spring in place. Pressure on the lock members breaks the lock members after injection, and this then allows the springs to release, causing the needle to be retracted into the housing. The spring has sufficient force to be able to withstand the injection fluid pressure. US 6,863,659 discloses the following: "The operation cycle of the sharp safe hydraulic retractable syringe is that the user removes plunger rod stop 16 and fully depresses the plunger rod 1 assembly to fully deploy the hypodermic needle 4 through the opening in the first end of elongated hollow barrel 2. The user then aspirates injection fluid into the "syringe" and performs an injection in the conventional manner. During the injection stroke the hydraulic pressure of the injection fluid is raised forcing the activating ring with three moulded pistons 8 against the release activating slide 10a, 10b, 10c which convert the axial pressure of the activating ring with three moulded pistons 8 to a radial pressure acting on the catch ends of respective legs. This radial pressure displaces the catch ends of three-legged retaining clip 11 from the recesses of the release activating slide 10a, 10b, 10c into the grooves on the outside of spring retaining cup 12 thus allowing the springs to expand when the hydraulic pressure falls at the completion of the injection stroke. Thus the springs force the slideable body 7 on which hypodermic needle 4 is mounted away from the first end of, and fully into, elongated hollow barrel 2. Three-legged retaining clip 11 has two of its three legs preset so as to force the spring separating plate 15 against hypodermic needle 4 causing it to be axially misaligned and incapable of re-emerging through the opening in the first end of elongated hollow barrel 2." The syringe only retracts the needle and once retracted, cannot be uncovered, as the legs, once engaged, cannot be disengaged. SUMMARY OF THE INVENTION

A hydraulically actuated capsule for a dental syringe is provided. The capsule can be provided as a sterile disposable. The capsule has a cover, a body, a biasing member and a distal needle. The capsule allows for the needle to be entirely covered as the capsule is being attached to the syringe, and to remain covered as a practitioner is approaching a patient, then be uncovered by simply depressing the plunger of the syringe slightly, thereby causing the hydraulic mechanism to release the cover and the biasing member to urge the cover away from the needle. After injecting, the practitioner can draw the cover back over the needle so that the patient again does not see the needle. The needle is entirely covered prior to removing the capsule. The capsule can then be disposed of, without any risk of a needle stick injury. The capsule therefore provides a safe syringe having little or no possibility of a needle stick injury occurring when used correctly. Additionally, it is patient friendly as the patient does not see the needle.

The capsule comprises: a cover, the cover comprising: a resilient first mating member; an open distal end; an open proximal end; and a bore therebetween; a body, the body comprising: a second mating member, wherein the first and second mating members define a reversibly releasable mating pair; mating means for mating the capsule with a syringe; a radially disposed cylinder, the cylinder comprising a bottom, a side wall, an inlet, the inlet in the vicinity of the bottom of the cylinder, an outlet, the outlet on the side wall; a piston slidably housed in the cylinder; a proximal needle in fluid communication with the cylinder through the inlet; and a distal conduit in fluid communication with the cylinder through the outlet; a biasing member located between the cover and the body for biasing the cover proximally substantially axially from the body; and a distal needle, the distal needle in fluid communication with the distal conduit, such that in use, fluid enters the cylinder through the inlet, hydraulic pressure urges the piston from the vicinity of the bottom of the cylinder, the piston urges the resilient first mating member outward, reversibly releasing the mating pair, and the biasing member urges the cover from the body proximally, thereby exposing the distal needle. The capsule preferably comprises at least one gasket, wherein the piston comprises a seat for accepting and locating the gasket in the vicinity of a distal end of the piston. The biasing member is preferably a spring that is retained by a collar on the inner surface of the cover and an annular sear on the body.

Advantageously, the capsule further comprises a guide means for aligning the cover on the body, which can be slidably mating non-circular profiles of the cover and the body, or can be a guide on an inner surface of the cover and a guide member on an outer surface of the body for slidable axial engagement of the cover.

The resilient first mating member is a tab having a free end adjacent the open end of the cylinder, proximate the piston and the reversibly releasable mating pair are a lip and a catch.

Preferably, the inlet enters the bottom of the cylinder and the outlet is about 1 mm to about 2 mm from the bottom. The gasket is preferably located about 1 mm to about 2 mm from a proximal end of the piston.

Advantageously, the capsule is sterilized. In other terms, a capsule for use with a dental syringe is provided. The dental syringe has a plunger, a barrel and a carpule containing fluid housed therein, wherein pressure on the plunger forces fluid from the carpule. The capsule comprises: a distal needle; a cover, the cover positionable between a pre-use position, wherein the distal needle is contained entirely within the cover, an injecting position, wherein the distal needle projects axially outward from the cover, and a disposal position wherein the distal needle is contained entirely within the cover; a body slidably housed coaxially in the cover and retaining the distal needle, the body comprising a hydraulic actuator for fluid communication with a carpule and in fluid communication with the distal needle, the hydraulic actuator positionable between a pre-use position, wherein there is neutral fluid pressure, a releasing position, wherein fluid pressure urges the actuator to reversibly release the cover from the body, an injecting position, wherein fluid flows through the actuator to the distal needle and a repositioning position, wherein fluid pressure is relieved and the hydraulic actuator permits positioning of the cover to the disposal position and reversible engagement of the cover to the body; a biasing member between the body and the cover generating an axial force on the cover; and at least one reversibly mating pair comprising a first mating member on the cover and a second mating member on the body, the reversibly mating pair releasably retaining the cover in the pre-use position against the axial force of the spring and the radial force of the actuator. The capsule preferably further comprises a guide pair for guiding axial movement of the cover relative to the body.

Advantageously, the actuator is a piston housed in a cylinder. A dental syringe, comprising a plunger, a barrel and a carpule containing fluid housed therein, is also provided. The improvement to the dental syringe is a capsule, that comprises: a distal needle; a cover, the cover positionable between a pre-use position, wherein the distal needle is contained entirely within the cover, an injecting position, wherein the distal needle projects axially outward from the cover, and a disposal position wherein the distal needle is contained entirely within the cover; a body slidably housed coaxially in the cover and retaining the distal needle, the body comprising a hydraulic actuator for fluid communication with a carpule and in fluid communication with the distal needle, the hydraulic actuator positionable between a pre-use position, wherein there is neutral fluid pressure, a releasing position, wherein fluid pressure urges the actuator to reversibly release the cover from the body, an injecting position, wherein fluid flows through the actuator to the distal needle and a repositioning position, wherein fluid pressure is relieved and the hydraulic actuator permits positioning of the cover to the disposal position and reversible engagement of the cover to the body; a biasing member between the body and the cover generating an axial force on the cover; and at least one reversibly mating pair comprising a first mating member on the cover and a second mating member on the body, the reversibly mating pair releasably retaining the cover in the pre-use position against the axial force of the spring and the radial force of the actuator. In other terms, a dental syringe, comprising a plunger, a barrel and a capsule is provided. The capsule comprises: a cover, the cover comprising: a resilient first mating member; an open distal end; an open proximal end; and a bore therebetween; a body, the body comprising: a second mating member, wherein the first and second mating members define a reversibly releasable mating pair; mating means for mating the capsule with the syringe; a radially disposed cylinder, the cylinder comprising a bottom, a side wall, an inlet, the inlet in the vicinity of the bottom of the cylinder, an outlet, the outlet on the side wall, a piston slidably housed in the cylinder, the piston provided with at least one gasket, wherein the piston comprises a seat for accepting and locating the gasket in the vicinity of a distal end of the piston; a proximal needle in fluid communication with the cylinder through the inlet, a distal conduit in fluid communication with the cylinder through the outlet; a spring located between the cover and the body for biasing the cover proximally substantially axially from the body; and a distal needle, the distal needle in fluid communication with the distal conduit, such that in use, fluid enters the cylinder through the inlet, hydraulic pressure urges the piston from the vicinity of the bottom of the cylinder, the piston urges the resilient first mating member outward, reversibly releasing the mating pair, and the biasing member urges the cover from the body proximally, thereby exposing the distal needle.

The capsule advantageously comprises a guide means for aligning the cover on the body. The resilient first mating member is preferably a tab having a free end adjacent the open end of the cylinder, proximate the piston.

BRIEF DESCRIPTIONS OF DRAWINGS

Figure 1 is a perspective view of the syringe of the present technology; Figure 2 is a longitudinal sectional view of the technology of Figure 1 ;

Figure 3 is a longitudinal sectional view of the needle capsule and syringe of the present technology in the storage position;

Figure 4 is a longitudinal sectional view of the relationship between the needle capsule and syringe in the administering position;

Figure 5 a and b are median longitudinal views of the capsule of Figure 1 showing the cylinder; Figure 6 is a median longitudinal view of the capsule of Figure 1 showing the release mechanism;

Figure 7 is a cross sectional view of the technology of Figure 1 ; Figure 8 is a schematic showing fluid flow; and

Figure 9 is a schematic showing the mechanics of the release mechanism. DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

A hydraulic syringe, generally referred to as 10 is shown in Figure 1. The syringe 10 has a finger grip 12, a barrel 14, and a plunger, generally referred to as 16, the plunger 16 having a shaft 18 and a plunger ring 20. A needle capsule, generally referred to as 22, is slidably disposed along the longitudinal axis 24 over the distal end 26 of the barrel 14.

As shown in Figure 2, the finger grip 12 has an aperture 36 for slidably engaging the shaft 18. The barrel 14 has opposing side rails 38 defining a cavity 40 extending at least partially between a proximal end 42 and the distal end 26 of the barrel 14 for accepting the carpule 34. A spring 44 is located in the cavity 40 to assist in retaining the carpule 34.

The details of the needle capsule 22 are shown in Figures 3 and 4. The capsule 22 is preferably provided as a sterilized assembly. The needle capsule 22 comprises a cover 50 with a tab 52, a body 54, and a spring 56. The cover 50 has a stop 58 on an inner surface 62 in the vicinity of the distal end 64 to stop the cover 50 from sliding too far along the barrel 14 of the syringe 10. The cover 50 is preferably transparent or transluscent or has a window 138 (as shown in Figure 1) to allow a practitioner to view the carpule 34 when injecting to ensure that a blood vessel has not been entered. A bore 66 extends between an open distal end 64 and an open proximal end 68 for slidably accepting the syringe barrel 14. A non-circular profile, for example, but not limited to, an oval, or a square, of both the inner surface 62 of the cover 50 and the outer surface 114 of the body 54 promotes coaxial sliding of the cover 50 on the barrel 14. At least one guide 70 and preferably two guides 70 parallel the longitudinal axis 24 of the syringe 10 to maintain coaxial movement of the cover 50. The body 54 has a piston 72 normal to the longitudinal axis 24 that is slidably housed in a cylinder 74. At the open end 76 of the cylinder 74, the piston 72 abuts the tab 52 of the cover 50. The distal end 73 of the piston is preferably convex. The body 54 is slidably engaged with the cover 50. A biasing member, which in the preferred embodiment is a spring 56, is compressed between the body 54 and a collar 84 on the inner surface 62 of the cover 50. The spring 56 biases the cover 50 to the administration or uncovered position. Proximal to the piston 72 there is a lip 112 on the outer surface 114 of the body 54. The lip 112 need only be adjacent the piston 72.

As shown in Figures 4, 5 A and 5B, preferably, the body 54 has an annular seat 85 for abutting the distal end 87 of the spring 56. The body 54 has a proximal needle 88 and a threaded female connector 90 for threadedly engaging the syringe barrel 14. When engaged, the proximal needle 88 is in fluid communication with the carpule 34. The proximal needle 88 is in fluid communication with the cylinder 74 in the vicinity of the bottom 92 of the cylinder 74. The may be through direct contact, or via a conduit 93. A conduit 94 leads from the cylinder 74 through a side wall 96 at approximately one or two millimeters from the bottom 92. The conduit 94 may be molded as an integral part of the body 54, or may be a needle. The distance from the bottom 92 is equivalent to the distance that the piston 72 must push the tab 52 in order to release the cover 50. A distal needle 98 is in fluid communication with the conduit 94. The piston 72 has a seat 100. Two O-rings, or a single wider ring 110 function as a gasket, and abut the seat 100. They are sized such that the diameter is equivalent to the diameter of piston 72 at its distal end 73. The O-rings assist in retaining fluid in the cylinder 74 when pressure is exerted.

The details of the cylinder are shown in Figures 5 A and B.

The release mechanism is shown in Figure 6. The tab 52 is free from the cover distally, i.e. it has a free end 51 and is resiliently flexible, to allow for some movement from the tab cavity 53. The tab 52 has a catch 116 on the adjacent surface 118, that being the surface adjacent the body 54. Before disengaging, the lip 112 is proximal to the catch 116. The piston 72, when urged upwards, contacts the tab 52 and urges it upward, releasing the catch 116 from the lip 112. The spring 56, then urges the cover 50 to slide proximally over the barrel 14, exposing the distal needle 98. As shown in Figure 7, the body 54 has guide members 120 for engaging the guides 70 on the cover 50. The guide 70 extends along the inner surface 62 of the cover 50 along the longitudinal axis 24 of the syringe 10. The guide members 120 and guides 70 are referred to collectively as a guide pair.

In use, a practitioner unwraps the sterilized capsule 22, slides it onto the syringe barrel 14, then threads the body 54 onto the distal end 26 of the barrel 14. Once assembled, the practitioner begins by administering pressure on the plunger ring 20, causing the plunger 16 to urge contents of the carpule 34 into the body 54. The fluid enters the cylinder 74 at or close to the bottom 92 of the cylinder (see Figure 8 for fluid flow). This exerts pressure on the piston 72, which then slides within the open ended cylinder 74, pushing the tab 52 of the cover 50 freeing the catch 116 from the lip 112 on the body 54 (see Figure 9 for mechanics of the release mechanism). The spring 56 then urges the cover 50 to slide proximally along the barrel 14, exposing the distal needle 98. The practitioner can then inject the patient by further depressing the plunger 16 and expelling the contents of the carpule 34.

After the practitioner has injected the patient, the needle 98 can be re-covered by pushing the cover 50 distally. The force needed to do this is sufficient to compress the spring 56. The catch 116 of the tab 52 then re-engages with the lip 112 of the body 54, locking the cover 50 into the covered position. This holds the cover 50 in place, with the needle 98 safely covered. The practitioner can then unthread the capsule 22 from the barrel 14 of the syringe 10 and safely dispose of it as a unit. The relationship between the inlet 102, the outlet 104, the piston 72 and the O- rings 110 is shown in Figures 8 and 9.

The fluid path is shown in Figure 8. Fluid is urged into the proximal needle 88 and through the inlet 102 in the transition from the pre -use position to an activating position 200. The fluid is further urged into the cylinder 74, forcing the piston 72 partially out of the cylinder 74. The O-rings 110 align with the outlet 104 to inhibit or stop fluid flow, thereby allowing for the pressure increase needed to force the piston 72 out of the cylinder 74. This is then the releasing position 202. Further urging of the fluid forces the piston 72 further out of the cylinder 74, allowing the outlet 104 to be clear of the O-rings 110, and consequently, fluid flows through the outlet 104 to the distal needle 98. This is the injecting position 204. The transition from the releasing position to the injecting position is essentially instantaneous. Once the fluid flow ceases, the pressure drops and the piston 72 can be returned to a repositioning position 206. The mechanics of the release mechanism is shown in Figure 9. The pre-use position 198 is a neutral position. The cover 50 is aligned relative to the body 54 such that the tab 52 is over the piston 72 and the reversibly mating pair comprising the catch 116 and the lip 112 is engaged. In order to move from the pre-use position 198 to the releasing position 202, force is exerted as shown by arrow 199. In the releasing position 202, the piston 72 is urged out of the cylinder 74, abuts the adjacent surface 118, then lifts the tab 52 up. This releases the cover 50 from the body 54. To move from the releasing position 202 to the injecting position 204, force is exerted as shown by arrow 203. This force is the biasing force of the spring 56. Once the injection has been completed, force 205 returns the cover 50 and body 54 to the disposal position 208.

The design of the capsule allows it to be used on a standard syringe, with the capsule being a disposable. The capsule is provided in the covered position. This means that the cover is over the needle. It is only when the practitioner is injecting a patient that the needle is exposed. Following injection, the needle is again covered by sliding the cover over the needle. Thus the cover reversibly covers and uncovers the needle. The design allows the practitioner to remove the cover and inject the patient using one hand. The patient need not see the needle, as uncovering the needle can be done immediately before injecting and is done smoothly as part of the injection process. Once the injection is completed, the practitioner can cover the needle, by using the other hand to urge the cover over the needle at the same time as the syringe is being removed from the vicinity of the patient. Again, this can be done smoothly as part of the process of removing the syringe. This greatly reduces the stress on a patient. Further, as the needle is covered during both the assembly and disposal, and can indeed be covered between injections, needle stick injuries are minimized.

The foregoing is a description of an embodiment of the present technology. As would be known to one skilled in the art, variations are contemplated that do not alter the scope of the technology. For example, the conduit can be replaced with a needle or any other channel that permits flow of fluid from the needle cannula to the barrel, the spring may be replaced with any other suitable biasing member and the O-ring(s) can be replaced with any suitable gasket.

Claims

What claimed is: 1. A hydraulically actuated capsule for use with a syringe, the capsule comprising: a cover, the cover comprising: a resilient first mating member; an open distal end; an open proximal end; and a bore therebetween; a body, the body comprising: a second mating member, wherein the first mating member and the second mating member define a reversibly releasable mating pair; mating means for mating the capsule with the syringe; a radially disposed cylinder, the cylinder comprising a bottom, a side wall, an inlet, the inlet in a vicinity of the bottom of the cylinder, an outlet, the outlet on the side wall; a piston slidably housed in the cylinder; a proximal needle in fluid communication with the cylinder through the inlet; and a distal conduit in fluid communication with the cylinder through the outlet; a biasing member located between the cover and the body for biasing the cover proximally substantially axially from the body; and a distal needle, the distal needle in fluid communication with the distal conduit, such that in use, fluid enters the cylinder through the inlet, hydraulic pressure urges the piston from the vicinity of the bottom of the cylinder, the piston urges the resilient first mating member outward, reversibly releasing the mating pair, and the biasing member urges the cover from the body proximally, thereby exposing the distal needle. 2. The capsule of claim 1 , further comprising at least one gasket, wherein the piston comprises a seat for accepting and locating the gasket in a vicinity of a distal end of the piston.

The capsule of claims 1 or 2, wherein the biasing member is a spring that is retained by the cover and the body.

4. The capsule of any one of claims 1 to 3, wherein the biasing member is retained by an annular seat on the body and a collar on an inner surface of the cover.

5. The capsule of any one of claims 1 to 4 further comprising a guide means for aligning the cover on the body.

6. The capsule of any one of claims 1 to 5 wherein the cover and body have slidably mating non-circular profiles.

7. The capsule of any one of claims 1 to 6 wherein the guide means is a guide on an inner surface of the cover and a guide member on an outer surface of the body for slidable axial engagement of the cover.

8. The capsule of any one of claims 1 to 7, wherein the resilient first mating member is a tab having a free end adjacent an open end of the cylinder, proximate the piston.

9. The capsule of any one of claims 1 to 8, wherein the reversibly releasable mating pair are a lip and a catch.

10. The capsule of any one of claims 1 to 9, wherein the inlet enters the bottom of the cylinder.

11. The capsule of any one of claims 1 to 10, wherein the outlet is about 1 mm to about 2 mm from the bottom.

12. The capsule of any one of claims 2 to 11, wherein the gasket is located about 1 mm to about 2 mm from a proximal end of the piston.

13. The capsule of any one of claims 1 to 12, wherein the capsule is sterilized.

14. A capsule for use with a dental syringe having a plunger, a barrel and a carpule containing fluid housed therein, wherein pressure on the plunger forces fluid from the carpule, the capsule comprising: a distal needle; a cover, the cover positionable between a pre -use position, wherein the distal needle is contained entirely within the cover, an injecting position, wherein the distal needle projects axially outward from the cover, and a disposal position wherein the distal needle is contained entirely within the cover; a body slidably housed coaxially in the cover and retaining the distal needle, the body comprising a hydraulic actuator for fluid communication with the carpule and in fluid communication with the distal needle, the hydraulic actuator positionable between a pre-use position, wherein there is neutral fluid pressure, a releasing position, wherein fluid pressure urges the actuator to reversibly release the cover from the body, an injecting position, wherein fluid flows through the actuator to the distal needle and a repositioning position, wherein fluid pressure is relieved and the hydraulic actuator permits positioning of the cover to the disposal position and reversible engagement of the cover to the body; a biasing member between the body and the cover generating an axial force on the cover; and at least one reversibly mating pair comprising a first mating member on the cover and a second mating member on the body, the reversibly mating pair releasably retaining the cover in the pre-use position against the axial force of a spring and a radial force of the actuator.

15. The capsule of claim 14, further comprising a guide pair for guiding axial movement of the cover relative to the body.

16. The capsule of claims 14 or 15, wherein the actuator is defined as a piston housed in a cylinder.

17. A dental syringe, comprising a plunger, a barrel and a carpule containing fluid housed therein, the improvement being a capsule, the capsule comprising: a distal needle; a cover, the cover positionable between a pre-use position, wherein the distal needle is contained entirely within the cover, an injecting position, wherein the distal needle projects axially outward from the cover, and a disposal position wherein the distal needle is contained entirely within the cover; a body slidably housed coaxially in the cover and retaining the distal needle, the body comprising a hydraulic actuator for fluid communication with a carpule and in fluid communication with the distal needle, the hydraulic actuator positionable between a pre-use position, wherein there is neutral fluid pressure, a releasing position, wherein fluid pressure urges the actuator to reversibly release the cover from the body, an injecting position, wherein fluid flows through the actuator to the distal needle and a repositioning position, wherein fluid pressure is relieved and the hydraulic actuator permits positioning of the cover to the disposal position and reversible engagement of the cover to the body; a biasing member between the body and the cover generating an axial force on the cover; and at least one reversibly mating pair comprising a first mating member on the cover and a second mating member on the body, the reversibly mating pair releasably retaining the cover in the pre-use position against the axial force of an spring and a radial force of the actuator.

18. A dental syringe, comprising a plunger, a barrel and a capsule, the capsule comprising: a cover, the cover comprising: a resilient first mating member; an open distal end; an open proximal end; and a bore therebetween; a body, the body comprising: a second mating member, wherein the first mating member and the second mating member define a reversibly releasable mating pair; mating means for mating the capsule with the syringe; a radially disposed cylinder, the cylinder comprising a bottom, a side wall, an inlet, the inlet in a vicinity of the bottom of the cylinder, an outlet, the outlet on the side wall; a piston slidably housed in the cylinder, the piston provided with at least one gasket, wherein the piston comprises a seat for accepting and locating the gasket in a vicinity of a distal end of the piston; a proximal needle in fluid communication with the cylinder through the inlet, a distal conduit in fluid communication with the cylinder through the outlet; a spring located between the cover and the body for biasing the cover proximally substantially axially from the body; and a distal needle, the distal needle in fluid communication with the distal conduit, such that in use, fluid enters the cylinder through the inlet, hydraulic pressure urges the piston from the vicinity of the bottom of the cylinder, the piston urges the resilient first mating member outward, reversibly releasing the mating pair, and the biasing member urges the cover from the body proximally, thereby exposing the distal needle.

19. The capsule of claim 18 further comprising a guide means for aligning the cover on the body.

20. The capsule of claims 18 or 19, wherein the resilient first mating member is a tab having a free end adjacent an open end of the cylinder, proximate the piston.