WO1997044077A1

WO1997044077A1 - Reinforced locking syringe

Info

Publication number: WO1997044077A1
Application number: PCT/US1997/005491
Authority: WO
Inventors: D. Kent Backman; William Padilla; Arlin Dale Nelson
Original assignee: Merit Medical Systems, Inc.
Priority date: 1996-05-21
Filing date: 1997-04-02
Publication date: 1997-11-27
Also published as: AU2605597A

Abstract

A reinforced locking syringe (10) may be selectively operable in either of a freely reciprocating or a restricted, threaded mode. A trigger (22) attached to the plunger (14) engages internal threads (38) on the interior of the barrel (12) of the syringe (10) with external threads (56) located on the plunger (14) On a spine (53). A handle (20) is affixed to the plunger (14), and a retraction bar (50) is rigidly secured to the spine (53). The threads (56) on the plunger (14) may be retracted from engagement with the threads (38) on the barrel (12), thereby placing the syringe (10) in its freely reciprocating mode. The trigger (22), which is spring biased to engage the external (56) and internal threads (38), employs a plurality of ramps (52) and channels (54) disposed at approximately the same angle to the longitudinal axes of the plunger (14) and barrel (12) as are the threads. A reinforcing sleeve (101) surrounding the barrel (12) prevents the deformation of the syringe (10) when high pressures are exerted within the syringe (10).

Description

REINFORCED LOCKING SYRINGE BACKGROUND 1. Field of the Invention

The present invention is in the field of syringes. More particularly, the present 5 invention relates to a reinforced syringe, such as a reinforced locking syringe that incorporates on the plunger thereof a triggering device which may be actuated to retract threads on the plunger, thereby to enable the plunger to move with respect to the barrel in a freely reciprocating rather than in the restricted, threaded mode. The invention has ready application to the field of angioplasty. 0 2. The Background of the Invention

One ofthe most basic ofthe tools used by the medical practitioner is the syringe. Perhaps best known as an instrument used with a needle to inject medicine into a patient, the syringe has also been found useful in a variety of other applications. For example, syringes are particularly useful in performing angioplastic procedures. 5 Angioplasty is a procedure for reducing the blockage which may occur in blood vessels. Over time, blood vessels may become partially or totally blocked due to buildup of cholesterol plaque along the walls ofthe vessel.

One location where plaque buildup is particularly dangerous is within the coronary arteries. The coronary arteries are those arteries which supply oxygen-rich o blood to the heart. Buildup of plaque within the coronary arteries, a condition commonly referred to as coronary artery disease, can cause serious chest pain — angina — and, if not treated, may eventually cause heart failure.

Coronary angioplasty involves opening these blocked coronary arteries by inserting a balloon-tipped catheter into the artery. The balloon is inserted by making an 5 incision usually in the groin or arm. A catheter is then inserted in a blood vessel exposed by the incision and threaded into the coronary artery.

An X-ray sensitive dye is injected into the coronary artery to enable the clinician to accurately position the catheter in the blocked portion of the artery. The catheter is inserted along the artery until the section ofthe catheter on which the balloon is located 0 is positioned along the blocked portion ofthe artery.

A fluid is injected into the catheter to inflate the balloon. As the balloon is inflated, the plaque is compressed thereby expanding the narrowed artery. The clinician then withdraws the fluid from the balloon catheter, causing the balloon to deflate. The balloon catheter may then be removed from the patient. It has been found that a syringe provides an effective tool for the introduction of fluid into the balloon catheter. As the pressure within the balloon must be carefully controlled during the angioplasty procedure, typical syringes having a plunger which may be freely depressed into the barrel are inadequate for this application.

If the pressure within the balloon is too great, the balloon may burst, a circumstance which usually requires immediate emergency surgery to correct. Some prior art attempts at designing a syringe which provides greater control over the pressures achieved in the balloon include providing a syringe which incorporates a plunger which is threadably connected to the barrel. Thus, the plunger may be slowly threaded into the barrel, resulting in a more controlled introduction of fluid into the balloon catheter.

A serious disadvantage to such syringes is the inability to freely and rapidly move the plunger in and out ofthe barrel in sliding reciprocation. For example, a preferred method of deflating the balloon is to rapidly withdraw the plunger from the barrel to create a negative pressure, thereby causing the fluid to exit the balloon in an attempt to equilibrate the pressure within the balloon catheter. Withdrawing the plunger gradually from the barrel of the syringe by "unscrewing" the plunger requires a great amount of time and, more significantly, results in reduced effectiveness in deflating the balloon.

In recognition ofthe desirability of a syringe capable of operating in both a freely reciprocating mode and a restricted, threaded mode, syringes have been developed which employ a threaded engagement mechanism on the barrel of the syringe which can be actuated to selectively engage with and disengage from threads on the plunger. When the thread engagement mechanism is engaged, the syringe is in its restricted threaded mode, so that free reciprocating movement of the plunger sliding within the barrel is prevented. In this restricted mode of operation, the plunger may only be moved within the barrel by its rotation, which gradually moves it into or out of the barrel. In many syringes employing a thread engagement mechanism on the barrel, the syringe is awkward to use. When using the syringe, the operator must grasp the barrel with one hand and depress the plunger with the other hand, taking care to steadily hold the syringe as the plunger is depressed. Depending on the location and direction of actuation ofthe thread engagement mechanism, it can be difficult to maintain the syringe in a steady position and control the thread engagement mechanism at the same time.

An additional disadvantage to such syringes is that some prior art syringes require that the barrel of the syringe be aligned in a certain orientation before the thread engagement mechanism can be actuated. This makes the syringe more difficult to use because the user must first ensure that the syringe is properly aligned before actuating the thread engagement mechanism. A potentially serious flaw exists in known syringe designs incorporating thread engagement mechanisms. When such mechanisms are deactivated, the action of doing so causes corresponding longitudinal movement of the plunger. Such movement is unwanted, as causing potentially dangerous increases or decreases in the pressure within the balloon being inflated by the syringe. If the balloon were to be expanded beyond acceptable limits, the coronary artery being repaired might be expanded beyond its capacity to yield. Rupture ofthe coronary artery would require immediate emergency surgery to correct, and, depending on the severity ofthe rupture, might require immediate bypass surgery. Another disadvantage suffered by certain prior art syringes is conveniently removing air bubbles from locking syringes.

Apart from angioplasty, other medical applications would also benefit from a properly designed locking syringe. For example, such a syringe could be advantageously employed in a biopsy procedure to remove tissue or cell samples from a patient for later testing and laboratory examination. In a biopsy procedure ofthe type contemplated, a needle is attached to the locking syringe and inserted into the body ofthe patient such that the end ofthe needle contacts the tissue desired to be sampled. The plunger is disengaged from its restricted, threaded mode of operation and rapidly withdrawn in the barrel ofthe syringe, creating a negative pressure within the barrel ofthe syringe and in the biopsy needle. The negative pressure draws sample tissue into the needle. Utilizing a locking syringe would enable the clinician to lock the plunger in this retracted position and preserves the negative pressure during withdrawal ofthe needle from the body ofthe patient. Nevertheless, many ofthe problems and disadvantages discussed above with respect to angioplasty syringes also exist in syringes used for biopsy. Another challenge faced by practitioners is managing the increasingly high pressures generated within the barrels of angioplasty syringes. Certain syringes currently on the market are not recommended for use in high pressure procedures. Syringes used in angioplastic procedures are particularly susceptible to deformation because the pressure caused by the compression of the plunger generates a force into the balloon catheter which is reciprocated against the barrel and plunger of the syringe.

An angioplasty syringe for inflating and deflating an angioplasty balloon catheter creates significant pressures within the balloon in order to compress arterial plaque against the walls ofthe coronary arteries. As a result, significant pressures exist within the barrel of the syringe. In addition to the increasingly high pressures used in current angioplastic procedures, recent advances in the placement and expansion of stents within arteries has demanded the use of higher pressures within syringes. After being widened or opened through angioplasty, certain arteries recollapse after a period of time, requiring a second or a series of angioplastic procedures to reopen the artery. In light of this phenomenon, practitioners may employ a balloon catheter to dispose a stent made from coiled wire, for 5 example, within a narrowed artery, then expand the stent by increasing the pressure within the balloon, then leave the expanded stent permanently in place as a buttress within the artery. The expansion of the stent requires the use of increased pressures within the syringe which may not be required in non-stent expansion procedures.

Even in non-stent applications, when the plunger is compressed toward the output 0 end of the syringe barrel, the fluid within the syringe exerts significant return pressure on the plunger and throughout the inner portion of the barrel. Under high pressures, the fluid can cause bulging or deformation of the syringe, for example, at the junction between the syringe and the barrel.

Under normal pressures, such as pressures at or below 20 atmospheres, the 5 internal threads on the barrel and the external threads on the plunger are engaged when the syringe is in the restricted mode. With the internal and external threads engaged, the relative position ofthe plunger in relation to the barrel is maintained, thereby preventing the force of the pressure built up within the syringe from moving the plunger relative to the barrel. o High pressures, however, such as pressures above 20 atmospheres, may cause the threads to bend or deform and may cause the barrel surrounding the threads to expand or become oval-shaped, creating a bulge in the portion of the barrel surrounding the interface between the internal and external threads. As a result, the internal and external threads may disengage, allowing undesired movement of the plunger relative to the 5 barrel.

Thus, locking syringes provide tremendous advantages in the fields of angioplasty, biopsies, and other procedures. However, extreme pressures may cause deformation of the syringe, which may result in unwanted movement of the plunger. Bulging or breakage, or unwanted movement ofthe plunger may result in the premature o release of pressure.

BRIEF SUMMARY OF THE INVENTION Advantages ofthe invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The advantages of the invention may be realized and obtained by means of 5 the instruments and combinations particularly pointed out in the appended claims. A preferred embodiment of a reinforced syringe is provided that comprises a novel plunger and barrel which together allow the syringe to be selectively operated between a freely reciprocating mode, in which the plunger may slide freely within the barrel in a reciprocating manner, and a restricted, threaded mode, in which the 5 reciprocating movement of the plunger is restricted by placing the plunger in threaded engagement with the barrel.

In the locked or engaged position, the plunger may be screwed into or out ofthe barrel by rotating the plunger, thereby resulting in controlled and gradual reciprocating movement ofthe plunger relative to the barrel. Additionally, if no force is applied to the 0 plunger to cause it to rotate, the plunger remains locked against any movement of the plunger with respect to the barrel. Thus, one operating the syringe in the locked or restricted mode can maintain precise control over the amount of pressure exerted by the syringe.

Accordingly, a locking syringe is provided comprising a barrel and a plunger at 5 least partially disposed in the barrel so as to engage its interior and be capable of reciprocating sliding movement therein. In one aspect ofthe present invention, a plunger position maintenance means is provided for selectively restricting reciprocating sliding movement of the plunger in order to hold a plunger in a selected position against a predetermined pressure created within the barrel. Such a plunger position maintenance o means may itself comprise an internal restricting means and an external restricting means.

The internal restricting means is located on a portion ofthe interior ofthe barrel. The external restricting means is located along at least a portion ofthe longitudinal axis ofthe plunger and is capable of being moved between an engaged position and a disengaged position. In the engaged position, the external restricting means engages the internal 5 restricting means to preclude reciprocating sliding movement of the plunger. In the disengaged position, the external restricting means is freely internal restricting means, so that the plunger is capable of reciprocating sliding movement.

In another aspect of the invention, a trigger means is provided for selectively moving the external restricting means between its engaged and its disengaged position. o The trigger means is capable of assuming a first position in which the external restricting means is placed in its engaged position and a second position in which the external restricting means is placed in its disengaged position. In one embodiment ofthe present invention, the trigger means comprises a handle rigidly secured to the plunger, and a retraction bar rigidly secured to the external restricting means. The retraction bar is 5 selectively movable in relation to the handle between first and second positions which correspond respectively to the first and second positions ofthe trigger means itself. A retraction bar bias means is included for urging the restriction bar into its first position. In another aspect of the preferred embodiment, the syringe is reinforced by a sleeve which surrounds the outside ofthe barrel at a region corresponding to the interface between the internal and external threads, preventing deformation of the barrel during high pressure use.

As the syringe incorporates a triggering device which is actuated by a trigger located on the plunger, a clinician is permitted to easily operate the trigger to actuate the triggering device using the same hand with which the plunger is actuated to operate the syringe. This can be accomplished regardless of whether the locking syringe is maintained in the free position or in the locked position.

In a preferred embodiment ofthe invention, the triggering device is incorporated into the neck ofthe plunger and includes threads and a series of channels disposed along a spine. Ramps corresponding to each channel are located along an elongated groove in the neck of the plunger such that the spine rests in the groove and each ramp is at least partially disposed within its corresponding channel. Upon actuation of the triggering device, the channels travel along the ramps, causing the spine and thereby the threaded portion of the triggering device to be retracted from engagement with corresponding threads on the barrel. In this retracted position, the spine is fully retracted into the groove in the neck of the plunger and the plunger may freely reciprocate slidably within the barrel.

Under such circumstances, yet another embodiment of a locking means usable with the present invention comprises a resilient clamp selectively attachable about the neck of the plunger during activation of the triggering device in order to maintain the spine fully retracted into the groove therein.

Advantageously, the ramps and channels are disposed at an acute angle with respect to the longitudinal axis of the barrel which is less than or equal to the angle of disposition ofthe teeth on the threads with respect to the longitudinal axis ofthe barrel. Thus, as the triggering device is actuated and the channels slide along the ramps, the threads on the triggering device are retracted from the threads on the barrel without any net force resulting which would cause movement ofthe plunger with respect to the barrel.

When the syringe is designed for angioplasty, it may also be provided with an integral transducer means for measuring the amount of pressure exerted on fluid being injected by the syringe, as more particularly described in United States Patent No. 5,135,488 entitled "System and Method for Monitoring, Displaying, and Recording

Balloon Catheter Inflation Data," which is incorporated herein by specific reference. BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantages ofthe invention are obtained, a more particular description ofthe invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments ofthe invention and are therefore not to be considered limiting of its scope, the invention will be described with additional specificity and detail through the use of the accompanying drawings in which:

Figure 1 is a perspective view of a first embodiment of a locking syringe incoφorating teachings ofthe present invention;

Figure 2 is an exploded, cross-section view of the components of the locking syringe of Figure 1 taken along section line 2-2 therein;

Figure 3 is a longitudinal, cross-section view ofthe locking syringe of Figure 1 in the restricted, threaded mode of operation; Figure 3 A is an enlarged detail sectional view of a portion ofthe interface ofthe internal and external threads illustrated in Figure 3;

Figure 4 is a longitudinal, cross-section view ofthe locking syringe of Figure 1 in the freely reciprocating mode of operation;

Figure 5 is a disassembled longitudinal, cross-section view ofthe pieces ofthe handle and triggering device ofthe locking syringe of Figure 1 ;

Figure 6 is a cross-sectional view of the pieces of a second embodiment ofthe handle and the triggering device of a locking syringe like that of Figure 1;

Figure 7 is a cross sectional view ofthe pieces ofthe handle and triggering device illustrated in Figure 6 showing the spine of the triggering device in a fully retracted position; Figure 8 is a cut-away cross-sectional view ofthe pieces ofthe handle and triggering device in Figure 7 taken along section line 8-8 shown therein, illustrating the intermeshing of channels and ramps of that triggering device;

Figure 9 is a perspective view of a locking syringe incoφorating teachings ofthe present invention, including a first embodiment of a lock for the thread-release mechanism and also demonstrating a cap having ridges over which channels in a reinforcing sleeve may be mounted;

Figure 10 is a perspective view ofthe locking syringe of Figure 8 with the lock for the thread-release mechanism thereof engaged;

Figure 11 is a longitudinal, cross-sectional view ofthe locking syringe of Figure 10 taken along section line 1 1-11 thereof; Figure 12 is a perspective view of a locking syringe incoφorating teachings of the present invention, including a second embodiment of a lock for the thread-release mechanism thereof; and

Figure 13 is a transverse, cross-sectional view ofthe locking syringe of Figure 12 taken along section line 13-13 therein.

Figure 14 is a perspective view of a locking syringe incoφorating teachings of the present invention, including a reinforcing means disposed over the barrel thereof;

Figure 15 is a longitudinal, cross-sectional view ofthe locking syringe of Figure 14 taken along section line 15-15 therein; Figure 16 is a perspective view ofthe reinforcing sleeve mounted on the syringe in Figure 14.

Figure 17 is a plan view ofthe sleeve of Figure 16 as seen from the distal end of the sleeve.

Figure 18 is a cut away view of the sleeve mounted on the syringe shown in Figure 14 taken along section line 18-18 shown therein, demonstrating the sleeve's effect of reinforcing the barrel such that the threads are retained in engagement when the syringe is in the locked mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the drawings, like parts are designated with like numerals. In Figure 1, a first embodiment of a locking syringe 10 is illustrated embodying teachings ofthe present invention. Locking syringe 10 includes a barrel 12 and a plunger 14. The barrel

12 has a plunger insertion end 15 and an output end 16 which is equipped with a tip 17.

A piece of tubing 18 may be attached to the tip 17. Tubing 18 may be connected to a rotatable connector, such as a luer connector, and attached to a balloon catheter (not shown) thereby creating a conduit for fluid communication between barrel 12 and the balloon catheter for use in angioplasty. Alternatively, a needle may be attached to locking syringe 10 at tip 17, thereby enabling the syringe to be used for a biopsy application or an application requiring controlled injection. It will be appreciated that there are a variety of applications for the locking syringe of the present invention and, according to the application, an appropriate attachment may be attached to the syringe at tip 17.

In Figure 1 , plunger 14 can be seen to be attached at a neck 19 to a handle 20.

Plunger 14 is also configured with a means for triggering the selection of the mode of operation of the syringe, whether it be the freely reciprocating mode or the restricted, threaded mode. The means for triggering such selection utilizes a triggering device 22.

As will be explained in greater detail below, triggering device 22 may be actuated to selectively place plunger 14 in threaded engagement with barrel 12 or to enable plunger 14 to freely reciprocate slidably within barrel 12.

With reference in addition to Figure 2, barrel 12 is seen to further include a cap

28 which is threadably connected to output end 16 thereof. Cap 28 is provided to facilitate assembly of locking syringe 10. Cap 28 also includes internal restricting means such as helical internal threads 38 which are capable of engaging corresponding threads on plunger 14.

Plunger 14 is configured with a collar 40 having a bulb adaptor 42 at one end.

The function and configuration of collar 40 is set forth in greater detail in United States Patent Application Serial No. 07/173,447, filed March 25, 1988, entitled "Disposable

Control Syringe." A rubber bulb 44, such as those known in the art, is attached to bulb adaptor 42.

In operation, collar 40 of the plunger 14 remains disposed within barrel 12.

Means are provided on plunger 14 to retain collar 40 within barrel 12. It is presently preferred that a flange 46 be configured on the end of collar 40 for this puφose. As plunger 14 is slidably extracted from barrel 12, flange 46 will engage and abut against a lip 48 of cap 28 to prevent further extraction of plunger 14.

Barrel 12 of the locking syringe 10 further includes a transducer 24 in fluid communication with the interior of barrel 12 for measuring the fluid pressure within barrel 12. In the presently preferred embodiment, the transducer 24 is located at output end 16 of barrel 12, near tip 17, as illustrated in Figures 1-3.

In order to effectively measure the pressure within barrel 12, transducer 24 is ideally always in fluid contact, directly or indirectly, with the fluid in the interior of barrel 12. To prevent plunger 14 from being inserted into barrel 12 and blocking the fluid contact between transducer means 24 and barrel 12, a stop 26 shown in Figure 1 is configured on plunger 14.

Stop 26 acts to prevent plunger 14 from being inserted into barrel 12 beyond the location of stop 26. It will be appreciated that a variety of other means may be employed for preventing plunger 14 from blocking fluid contact between transducer 24 and the fluid in the interior of barrel 12. For example, a ridge could be provided along the interior of barrel 12 adjacent transducer 24 toward the same result.

With reference now specifically to Figure 2, transducer 24 comprises, for example, a piezoresistive semiconductor integrated circuit chip 25 which mounts within a housing 30 integrally configured on output end 16 of barrel 12. Transducer chip 25 and an electrical cable 31 attached thereto are secured in housing 30 with a suitable potting compound. A transducer cover 32 is provided to enclose the entire assembly in housing 30. A small opening 34 permits the fluid contact between transducer chip 25 and the fluid in the interior of barrel 12. Stop 26 serves as a means to prevent plunger 14 from being inserted into barrel 12 to a point at which bulb 44 would block opening 34.

It can also be seen in Figure 2, triggering device 22 includes a retraction bar 50 in connection with plunger 14. In a presently preferred embodiment, retraction bar 50 is disposed proximate to handle 20 to facilitate actuating retraction bar 50 with the same hand used to grasp handle 20. It will be appreciated that retraction bar 50 may also be disposed at various locations along plunger 14.

Triggering device 22 further includes an extended longitudinal groove 51 having a series of ramps 52 disposed along the walls thereof. A spine 53 having a corresponding channel 54 for each ramp 52 is disposed within groove 51, such that each ramp 52 is disposed in register with and at least partially within a corresponding channel 54 during the operation of locking syringe 10. This relationship is maintained in both the freely reciprocating mode of operation or the restricted, threaded mode. Although in a presently preferred embodiment ofthe invention three or four sets of ramps and channels are employed, it will be appreciated that the number of ramps and channels is largely a matter of design choice. It has been found that increasing the number of ramps and channels may lend stability to plunger 14 and prevent unwanted deflection in triggering device 22. Further, although the preferred embodiment has channels 54 disposed on spine 53 and ramps 52 disposed on the walls of groove 51 , it should be understood that alternatively these relative positions could be reversed. Then channels 54 would be disposed along the walls of groove 51 in neck 19 and ramps 52 would be disposed along spine 53.

In a preferred embodiment of triggering device 22, external threads 56 are configured along one side of spine 53 of triggering device 22. External threads 56 are so configured as to be capable of threadably engaging internal threads 38 located within cap 28. External threads 56 are noncontinuous, as the tooth pattern thereof does not continue around spine 53 to connect adjacent teeth.

Triggering device 22 is further configured with a means for biasing external threads 56 into threaded engagement with internal threads 38 and a means for biasing retraction bar 50 in a nonactuated position correspondingly. One presently preferred mechanism for accomplishing this function is to employ a spring 58, as illustrated in Figure 2, which rests between a notch 60 in retraction bar 50 and a post 62 attached to handle 20. Post 62 includes a nib 64 which fits inside the end of spring 58 resting against post 62. Nib 64 assists in positioning spring 58 against post 62 and preventing spring 58 from sliding laterally along post 62. Thus, post 62 and nib 64 act to properly position retraction bar 50 with respect to handle 20 and to prevent any lateral movement of retraction bar 50 with respect to handle 20.

The operation of the locking syringe 10 may be best explained by reference to Figures 3, 3 A, and 4. In Figure 3, locking syringe 10 according to the present invention is illustrated in its restricted, threaded mode of operation. In the restricted mode of operation, plunger 14 is in threaded engagement with barrel 12 by the engagement of external threads 56 with internal threads 38. Due to such threaded engagement, the slidably reciprocating movement of plunger 14 within barrel 12 in the longitudinal direction of handle 20 (substantially in the direction of arrow A shown in Figure 3) is restricted.

In the restricted mode of operation, plunger 14 may, however, be moved in and out of barrel 12 by rotating handle 20. Depending on the pitch of threads 56 and 38, plunger 14 will move in a helical path which translates into a predetermined longitudinal distance within barrel 12 with each rotation of handle 20. In this manner, the rotational movement of plunger 14 causes gradual longitudinal movement of rubber bulb 44 within barrel 12. This effects slight pressure differences in the material being injected or extracted by locking syringe 10. In some applications, such as in angioplasty, when locking syringe 10 is used to exert a controlled pressure, the ability to obtain slight longitudinal movements of plunger 14 or to move plunger 14 to a predetermined point of insertion are necessary for obtaining and exactly controlling the desired pressures.

Figure 4 illustrates the locking syringe 10 of the present invention with triggering device 22 actuated to place locking syringe 10 in freely reciprocating mode of operation. With triggering device 22 so actuated, a longitudinally directed force applied to handle 20 in the manner of arrow A will result in the substantially unrestricted slidable movement of plunger 14 longitudinally within barrel 12. Thus, rapid movement of plunger 14 with respect to barrel 12 may be obtained with locking syringe 10 in the freely reciprocating mode of operation.

Many applications requiring a locking syringe also require that the syringe be capable of operating in such a freely reciprocating mode. For example, when performing angioplasty, it is first necessary to fill the balloon catheter with a liquid before applying pressure on the liquid to expand the balloon within the blocked blood vessel. Initially, filling the balloon catheter can be quickly and easily accomplished with a syringe in such a freely reciprocating mode of operation. Also, when the angioplasty procedure is completed and it is desired to deflate the balloon, the balloon may be most efficiently and rapidly deflated by creating a negative pressure within locking syringe 10. This acts to extract liquid out ofthe balloon catheter, thereby deflating the balloon. The creation of negative pressure within locking syringe 10 can be effectively accomplished when locking syringe 10 is in the freely reciprocating mode of operation. Triggering device 22 is actuated by applying a force on retraction bar 50 in the direction shown in Figure 4 by arrow B. Unlike prior art type syringes, this may be advantageously done by the clinician with a one-handed squeezing movement using the same hand that moves plunger 14. The clinician grasps handle 20 and, by squeezing retraction bar 50 and handle 20, is able to apply a force on retraction bar 50 in the direction of arrow B and an equal and opposite force on handle 20. In the process, there is no resulting net force on plunger 14 which would tend to move plunger 14 in or out of barrel 12. The force applied to retraction bar 50 acts to compress spring 58 and causes channels 54 to slide over ramps 52, bringing spine 53 into longitudinal groove 51 in a direction indicated in Figure 4 by arrow C. The two primary components triggering device 22 are illustrated in Figure 5. As seen there neck 19 is connected to handle 20, and spine 53 connected to retraction bar 50 is slidably disposed in longitudinal groove 51 in neck 19. When the components of triggering device 22 shown in Figure 5 are assembled as illustrated in Figures 3 and 4, channels 54 each engage a ramp 52. As triggering device 22 is actuated by applying a force to retraction bar 50 in the direction of arrow B, spine 53 retracts in the direction in which channels 54 are forced to travel along ramps 52. As channels 54 travel along ramps 52, external threads 56 located on spine 53 are retracted from engagement with internal threads 38.

The direction of travel of external threads 56 in this process is dictated by the angle of disposition D made by ramps 52. For example, a presently preferred angle of disposition of ramps 52 is approximately 45 degrees with respect to longitudinal axis L. Thus, as external threads 56 are retracted upon actuation of triggering device 22, external threads 56 move both longitudinally in the direction of arrow B shown in Figure 4 and laterally in the direction of arrow C shown in that same figure. In some applications of a syringe according to the present invention, it is preferred that triggering device 22 be actuatable to change operating mode of the locking syringe between the restricted, threaded mode of operation to the freely reciprocating mode, without causing perceptible resulting movement of plunger 14 longitudinally with respect to barrel 12. Movement of plunger 14 with respect to barrel 12 may be avoided as external threads 56 are retracted from engagement with internal threads 38, if the angle of disposition ofthe external and internal threads is greater than or equal to the angle of disposition of ramps 52 and channels 54. Under such conditions the direction of movement of spine 53 in longitudinal groove 51 is at an angle that will not cause the threads to bind against each other.

Figure 3 A is an enlarged view of a portion ofthe interface between the internal 5 and external threads 38 and 56 of Figure 3 that illustrates the nonsymmetrical form ofthe teeth in internal threads 38 and external threads 56. As can be observed in Figure 3 A, each tooth 71 of the external threads 56 has a leading edge 72 and a trailing edge 74. Each tooth 75 of internal threads 38 has a leading edge 76 and a trailing edge 78. Leading edges 72 of teeth 71 of external threads 56 and leading edges 76 of teeth 75 of 0 internal threads 38 are preferably disposed at angles with respect to each other which permit the teeth to mesh properly. The same is true of trailing edges 74 of teeth 71 of external threads 56 and trailing edges 78 of teeth 75 of internal threads 38.

In a preferred embodiment, trailing edges 74 and 78 are disposed at substantially the same acute angle with respect to the longitudinal axis L of plunger 14 and barrel 12 5 shown in Figure 5 as the acute angle of disposition D associated with ramps 52 and channels 54. Thus, as external threads 56 are moved from the engaged position thereof of the disengaged position thereof, teeth 71 on exterior threads 56 retract without contacting trailing edge 78 of teeth 75 on internal threads 38 which would cause longitudinal movement of plunger 14 in barrel 12. Conversely, as external threads 56 are o moved from the disengaged position thereof to the engaged position thereof, minimal longitudinal movement, is imparted to plunger 14 within barrel 12. Significant longitudinal movement would result in a significant change in the pressure being exerted by the locking syringe 10. As noted above, this would not be acceptable for certain applications of a locking syringe. 5 If slight increases of pressure within barrel 12 of locking syringe 10 can be tolerated as triggering device 22 is actuated, a variety of combinations of angles may be utilized. It has been found that an angle of disposition D reflected in ramp 52 and channels 54, as well as in trailing edges 72 and 78 of teeth 71 and 75, respectively, of approximately 45 degrees is preferable. o Leading edges 72 and 76 of teeth 71 and 75, respectively, are preferably disposed at an angle of approximately two degrees from the normal to longitudinal axis L of plunger 14 and barrel 12. This two-degree draft is primarily to assist in removing the parts from their molds during the manufacturing process when the parts are molded from plastic. 5 In order to prevent plunger 14 from racheting back when a substantial back pressure is built up inside barrel 12 of locking syringe 10, ramps 52 are canted towards tip 17 of barrel 12. For other applications, it may be desirable to reverse the cant of ramps 52. For example, when locking syringe 10 is used primarily or exclusively for creating substantial negative pressures, ramps 52 may be canted away from tip 17, to prevent plunger 14 from racheting into barrel 12 as substantial negative pressures are 5 developed.

When it is desired to release locking syringe 10 from its freely reciprocating mode of operation and return it to the restricted threaded mode of operation, the force being applied to retraction bar 50 in the direction of arrow B in Figure 4 is merely released. Under the biasing force of spring 58, spine 53 will then travel up ramps 52 in a direction 0 to take spine 53 out of longitudinal groove 51 , returning external threads 56 to a position of threaded engagement with internal threads 38, as illustrated in Figure 3.

With retraction bar 50 attached to plunger 14 of locking syringe 10, triggering device 22 may be actuated regardless of the rotational orientation of handle 20 to barrel

12. To actuate triggering device 22, the operator of locking syringe 10 need only grasp 5 barrel 12 with one hand and hold handle 20 with the other. Retraction bar 50 may then be easily actuated with the hand which is holding handle 20.

In another preferred embodiment ofthe present invention, shown in Figures 6-8, the strength and stability of plunger 14 is enhanced by reducing the amount of empty space within the mechanism of triggering device 22. Wear on external threads 56 may o also be reduced by increasing the available travel distance for spine 53 into longitudinal groove 51, so that spine 53 retracts fully into groove 51 when external threads 56 are moved out of the engaged position thereof.

In the embodiment shown in Figures 6-8, spine 53 has channels 54 which are arranged in pairs in which each channel 54 ofthe pair is in lateral register with the other 5 with a support gusset 66 disposed longitudinally and centered along spine 53 between the channels 54 in each pair. Support gussets 66 add rigidity and strength to spine 53. Ramps 52 are provided on each side of longitudinal groove 51 that register with channels 54. To reduce the likelihood that ramps 52 may snag and prevent full retraction of spine 53 into longitudinal groove 51, ramps 52 have a bevelled leading edge 67. Each channel 0 54 on spine 53 correspondingly has a wedge 68 which compliments bevelled leading edge 67 of each ramp 52 when spine 53 is fully retracted into longitudinal groove 51. Wedges 68 add volume and further stability to spine 53.

Also, at least one protruding arm 70 is provided on spine 53 to assist maintaining orientation of spine 53 within longitudinal groove 51 during movement spine 53 along 5 ramps 52 and to enhance the lateral stability of plunger 14. Figure 7 shows spine 53 fully retracted into longitudinal groove 51, so that the tips of external threads 56 do not extend beyond upper edge 79 of neck 19. In this manner, during free sliding reciprocation of plunger 14 within barrel 12 there will be no grinding or undesired racheting of external threads 56 against internal threads 38, which could cause grinding and racheting, wear and breakage to the teeth thereof.

As can be seen in Figure 8, the preferred embodiment illustrated significantly reduces the amount of empty space within the mechanism of triggering device 22, thereby increasing the strength and stability of plunger 14.

It will be appreciated by one skilled in the relevant art that a syringe according to the present invention may be made of a variety of materials. It is presently preferred, however, that barrel 12, including tip 17, be made of a transparent material, such as a clear plastic. Thus, the operator of the syringe can visually ascertain whether there are any air bubbles in the contents of barrel 12.

Figure 9 demonstrates the preferred cap 28 employed in the present invention. Cap 28 preferably includes a plurality of reinforcing ribs or ridges 80 radially spaced about the periphery of cap 28 and extending longitudinally along the outside surface of cap 28.

Figure 9 also shows locking syringe 10 provided with an additional aspect ofthe invention intended to facilitate the priming of locking syringe 10 to remove air bubbles from the fluid contents thereof. Locking syringe 10 is provided with a plunger position maintenance means for selectively restrictive sliding movement of plunger 14 to hold plunger 14 in a selected position against the predetermined pressure created within barrel 12. As already disclosed, for example, in relation to Figures 3 and 4, a suitable plunger position maintenance means comprises an internal restricting means located on a portion of the interior of barrel 12 and an external restricting means located along at least a portion ofthe longitudinal axis of plunger 14. The internal restricting means takes the form of internal threads 38 formed on cap 28. The external restricting means comprises external threads 56 located along spine 53 which is attached to retraction bar 50 and slidably disposed in longitudinal groove 51. As thus configured, external threads 56 are movable between an engaged position illustrated in Figure 3 and a disengaged position illustrated in Figure 4. In the engaged position, which is also the position shown in Figure 9, external threads 56 engage internal threads 58 to restrict reciprocating sliding movement of plunger 14 in barrel 12. In the disengaged position external threads 56 are free of internal threads 38 and plunger 14 is capable of engaging and reciprocating sliding movement in barrel 12. This position is shown in Figure 10. According to another aspect ofthe invention, locking syringe 10 is provided with a trigger means for selectively moving external threads 56 between the engaged and disengaged position thereof. The trigger means of the present invention is capable of assuming a first position in which external threads 56 are placed in the engaged position thereof and a second position in which external threads 56 are placed in the disengaged position thereof. Thus, the first position of the trigger means of the present invention corresponds to the relationship of elements illustrated in Figures 3 and 9. Correspondingly, the second position of the trigger means of the present invention corresponds to the relationship of elements illustrated in Figures 4 and 10. As already illustrated by way of example, the trigger means of the present invention comprises a handle 20 rigidly secured to plunger 14 at neck 19. Retraction bar 50 is rigidly secured to spine 53 upon which external threads 56 are disposed. Retraction bar 50 is capable of being selectively moved relative to handle 20 between first and second positions which correspond respectively to the first and second positions of the trigger means of the invention. Spring 58 shown in Figure 3 functions as a retraction bar bias means for urging retraction bar 50 into the first position thereof, wherein reciprocating sliding movement of plunger 14 is possible.

According to another aspect ofthe present invention, locking syringe 10 includes a locking means for preventing movement of the trigger means into the first position thereof, thereby to maintain external threads 56 in the disengaged position thereof and to permit reciprocating sliding movement of plunger 14. The locking means thereby relieves an operator of locking syringe 10 from needing to continue to pull retraction bar 50 toward handle 20 and overcome the effect of spring 58. The locking means thus facilitates priming of locking syringe 10 by permitting its operation in the freely reciprocating mode without continuing to hold the trigger means ofthe invention in its first position.

Figure 9 illustrates one embodiment of a locking means configured according to present invention. There, as shown by way of example and not limitation, a pawl 90 is removably securable to retraction bar 50 by a pair of resilient legs 92 which snap about retraction bar 50. When thusly secured to retraction bar 50, pawl 90 is pivotable thereabout and longitudinally slidable toward and away from neck 19.

It is the puφose of pawl 90 to prevent retraction bar 50 from returning to the first position thereof illustrated in Figure 9 once retraction bar 50 is moved into the second position thereof by being drawn longitudinally toward handle 20 in the manner illustrated in Figure 10. Thereupon, the free end 94 of pawl 90 can through a combination of longitudinal movement on and pivoting about retraction bar 50 be entered into a pawl receiving aperture 96 formed in neck 19. Thus, when retraction bar 50 is in the second position thereof, pawl 90 can be moved selectively into a locked position engaging handle 20 and 5 preventing movement of retraction bar 50 out ofthe second position thereof in which free longitudinal movement of plunger 14 is possible.

The action of pawl 90 in effecting this result is more clearly appreciated by reference to the cross-section in Figure 11. There it can be seen that pawl 90 functions as a wedge and prevents retraction bar 50 attached to spine 53 with external threads 56 0 thereon from returning under the influence of spring 58 into a position in which external threads 56 engage internal threads 38. Thus, the operator of locking syringe 10 may release the compressive forces exerted thereby between traction bar 50 and handle 20 without having external threads 56 engage internal threads 38. The stub 98 at free end 94 of pawl 90 serves to fill pawl receiving aperture 96 which is occupied by retraction s bar 50 in the first position thereof. This precludes any return movement of retraction handle 50 thereinto.

Thus, actuation ofthe locking means ofthe present invention permits retraction bar 50 to be released, while locking syringe 10 remains in the freely reciprocating mode of operation. This frees both hands ofthe operator for the puφose of priming the fluid o contents of locking syringe 10 to remove air bubbles therefrom. One method for doing so involves orienting locking syringe 10 with output end 16 of barrel 12 in an upright position as shown in Figure 10. This enables bubbles in the fluid contents 99 of barrel 12 to migrate toward tip 17. Barrel 12 is preferably comprised of a transparent material to enable visual verification of this process. 5 With locking syringe 10 in the vertical position illustrated in Figure 10, the operator grasps barrel 12 and exerts a force thereon in the direction indicated by arrow F in Figure 10. This has the effect of urging plunger 14 into barrel 12, whereupon fluid contents 99 from output end 16 of barrel 12 are forced therefrom through tubing 18 carrying therewith all entrapped air bubbles. Once this process is completed, the o reapplication of compressive forces between retraction bar 50 and handle 20 will permit the removal of pawl 90 from pawl receiving aperture 96. If desired, pawl 90 may be removed entirely from retraction handle 50. At this point, with locking syringe 10 primed, pawl 90 can be discarded.

Naturally, the relative positions of pawl 90 and pawl receiving aperture 96 could 5 be reversed. A structure such as pawl 90 could be selectively or permanently secured to neck 19 in a manner so as to be pivotable into a position that would engage and wedge retraction bar 50 in the second position thereof. This would also prevent movement of retraction bar 50 into the first position thereof shown in Figure 9 and keep locking syringe 10 in its freely reciprocating mode of operation.

Additionally, an operator of locking syringe 10 may choose only to employ stub 98 of pawl 90 without attaching pawl 90 to retraction bar 50. Under such circumstances, only the effect of stub 98 in filling pawl receiving aperture 96 would be employed. With retraction arm 50 drawn into the second position thereof illustrated in Figure 10, stub 98 at free end 94 of pawl 90 would be inserted into pawl receiving aperture 96. This would fill pawl receiving aperture 96, preventing movement of retraction arm 50 into the first position thereof in which retraction arm 50 occupies pawl receiving aperture 96. Thus, stub 98 at free end 94 of pawl 90 could be utilized without recourse to resilient legs 92.

Yet another embodiment of a locking means according to the present invention is shown in relation to locking syringe 10 illustrated in Figure 12. There, retraction arm 50 is in the second position thereof in which spine 53 bearing external threads 56 is laterally withdrawn into longitudinal groove 51 in neck 19. In the position shown, plunger 14 is capable of reciprocating movement within barrel 12. In order to retain retraction bar 50 and handle 20 in the relative position illustrated, a second embodiment of a locking means according to the present invention could be utilized.

As shown by way of example a resilient C-shaped clamp 100 is snapped about neck 19 traversing longitudinal groove 51. Clamp 100 serves to prevent spine 53 from moving laterally out of longitudinal groove 50. In this manner all movement of spine 53 is simultaneously prevented, including that which with retraction bar 50 attached thereto would permit external threads 56 to engage internal threads 38 in the manner illustrated in Figure 3. The effect of clamp 100 in this regard is more fully understood by reference to Figure 13.

The effect of spring 58 shown in Figure 11 between handle 20 and retraction bar 50 is to urge retraction bar 50 and spine 53 attached thereto in a direction toward barrel 12. In the process, due to the interaction of clamps 52 and channels 54, shown for example in Figure 1 1, spine 53 is simultaneously directed radially out of longitudinal groove 51 in the upward direction as shown in Figure 13 by arrow G. Nevertheless, with clamp 100 traversing the opening to slot 51 in the direction of arrow G, spine 53 can engage in no lateral movement, and accordingly longitudinal movement thereof with retraction bar 50 is also precluded. Under such circumstances, priming of the fluid contents of locking syringe 10 can be undertaken in the manner described relative to Figure 10. Thereafter clamp 100 may be removed from neck 19 and either retained or discarded. Thus, it can be seen that, according to the teachings of the present invention, a locking syringe is provided in which the thread-release mechanism thereof can be temporarily locked out to permit an operator to use both hands for the puφose of removing air bubbles from the fluid contents ofthe syringe. When the threads are thusly locked out of engagement with each other, freely reciprocating movement of the plunger in the barrel of the syringe is possible. The locking means of the present invention permits this state to be maintained without continued activation of the thread release mechanism itself. Several embodiments of structures for effecting the lock ofthe thread release mechanism have been disclosed, including a pivotable pawl removably attachable to the retraction bar ofthe thread release mechanism and a resilient clamp securable about the neck between the handle and the plunger.

Figure 14 demonstrates locking syringe 10 provided with an additional aspect of the invention intended to reinforce barrel 12 of syringe 10 such that high pressures within syringe 10 will not deform syringe 10. Locking syringe 10 features a barrel 12, a plunger 14 disposed as least partially within barrel 12, and a reinforcing means 101 disposed about barrel 12 such that barrel 12 retains its shape upon the generation of pressure within barrel 12.

As pressure increases within syringe 10, barrel 12 may become oval-shaped or otherwise deform. By disposing a reinforcing means, such as a sleeve 101 , around a portion of barrel 12, additional stiffness is imparted to barrel 12, preventing deformation.

Sleeve 101 is particularly useful in reinforcing angioplasty syringes in which relatively high pressures are generated. As shown in Figure 14 and in cross-section in Figure 15, sleeve 101 is disposed about the plunger insertion end 15 of barrel 12, reinforcing the area surrounding the threaded interface between plunger 14 and barrel 12. As shown in Figure 15 and as described in more detail above, external threads 56 disposed on at least a portion of plunger 14 along the longitudinal axis thereof may threadably engage the internal threads 38 within baπel 12 at an interface, a portion of which is shown in Figure 3 A. By surrounding barrel 12 at this interface, sleeve 101 maintains a relative position between barrel 12 and plunger 14 such that the internal and external threads remain in engagement under high pressure.

As further shown by way of example in Figures 9 and 10, barrel 12 may include a cap 28 through which plunger 14 is disposed. Turning to Figure 14, sleeve 101 is preferably disposed about an outer portion of cap 28 adjacent internal threads 38 within cap 28. With reference to Figures 9 and 14, preferably, reinforcing sleeve 101 is disposed about the proximal cylindrical collar 103 of the cap 28. Most preferably, the distal end 107 of reinforcing sleeve 101, shown in Figure 16, engages the proximal edge 106 ofthe shoulder 105 ofthe cap 28 as shown in Figures 14 and 15.

As shown in Figure 9, the proximal cylindrical collar 103 has at least one ridge

80, and preferably four ridges 80 to prevent cap 28 from rotating within the mold during manufacturing. As seen in Figures 16 and 18, channels 109 in reinforcing sleeve 101 accommodate ridges 80, such that sleeve 101 can be disposed over cap 28. Figure 17 further illustrates channels 109 which receive ridges 80.

While it is possible for channels 109 to contact ridges 80 on cap 28, preferably channels 109 do not actually contact ridges 80, but instead, are dimensioned slightly larger than ridges 80 so that sleeve 101 can be readily disposed about cap 28. Referring again to Figure 17, protuberances 110 extend along the exterior surface of sleeve 101 above the channels 109 to reinforce sleeve 101 at those locations.

As seen in Figures 15, 16 and 17, the internal surface ofthe reinforcing sleeve 101 may have a radius 111 or chamfer adjacent the distal end 107 ofthe sleeve 101, allowing it to be slidably disposed about the barrel and allowing it to fit above a fillet 1 19 at the intersection between the proximal cylindrical collar 103 and the proximal edge 106 ofthe cap shoulder 105. In addition, as shown in Figures 16 and 17, it is possible to design channels 109 such that a second radius 112 or chamfer exists in the distal portion of each channel 109. A second fillet may also exist between the interface of each ridge 80 and proximal edge 106 of cap shoulder 105.

The inner surface 113 of the sleeve 101 is preferably disposed with an interference fit about an outer portion of cap 28. Thus, sleeve 101 fits snugly over cap 28 and exerts a small amount of pressure on the outer surface of cap 28. Sleeve 101 imparts stiffness to cap 28 which prevents bulging and deformation. As shown in Figure 18, sleeve 101 reinforces baπel 12 such that it remains a selected relative position with respect to the plunger 14, ensuring engagement between the external and internal threads when the syringe is in the restricted mode.

For puφoses of manufacturing, the outer surface 115 of sleeve 101 may have a slight taper at a draft angle and/or a lip extending between each of the ridges 80 as the distal end ofthe outer surface 115 in order to be more readily expelled from an injection mold.

While a variety of materials are available in the art for the construction of sleeve 101, the prefeπed material is designed to impart significant stiffness to barrel 12. The modulus of elasticity ofthe material is one important feature when choosing material for sleeve 101. One possible material for reinforcing the stiffness of cap 28 is fiberglass reinforced plastic. While cap 28 and the remaining portion of barrel 12 may be made from a clear polycarbonate, in one presently preferred embodiment, a sleeve is made from a 30% fiberglass reinforced polycarbonate having a white colorant. This material is approximately four times stiffer than the clear polycarbonate and, because of its higher modulus of elasticity, provides improved resistance to deformation. Although the material can withstand pressures significantly higher than 25 atmospheres, such material is recommended for use up to about 25 atmospheres.

In another presently preferred embodiment of sleeve 101 which is particularly useful when engaging in high pressure stent expansion procedures, sleeve 101 is made of a suitable aluminum material, such as the 6063-T6 aluminum. Although the material can withstand pressures significantly higher than 30 atmospheres, such material is recommended for use up to about 30 atmospheres.

Sleeve 101 may be placed onto cap 28 by placing cap 28 on a cylindrical post which supports the inner lip 48 of cap 28 shown in Figure 2. The post may further comprise a cylindrical neck which extends into the aperture 1 17 of cap 28 shown in Figure 2. A hydraulic cylinder may then be used to apply a force of approximately 175 pounds to dispose sleeve 101 in an interference fit about cap 28.

One skilled in the art will recognize that it is possible to retrofit sleeve 101 described in Figures 14 through 18 onto a variety of syringes, including locking and angioplasty syringes known and cuπently in use in the art. Thus, a syringe incoφorating sleeve 101 may further comprise each ofthe syringe components and features discussed throughout this application and may further comprise a variety of syringe components known in the art. For example, as depicted in Figure 15 and as described in detail above, a reinforced syringe may include a triggering means attached to plunger 14 for selectively retracting external threads 56, such that when the triggering means is actuated, external threads 56 and internal threads 38 maintain a position of disengagement, thereby enabling plunger 14 to be freely moved with respect to baπel 12.

In addition, reinforcing sleeve 101 can be selectively attached to preexisting syringes. Consequently, the versatility of a single sleeve 101 is greatly enhanced because it can be used with any one of a variety syringes that are already on hand. Thus, when using a preexisting syringe, a practitioner can retrofit the syringe with a reinforcing sleeve 101, and provide the syringe with reinforcement otherwise not available. Importantly, this retrofit capability provides the advantages of reinforcement, yet simultaneously protects any investment already made in stock of preexisting syringe devices. It will be appreciated that the apparatus and methods ofthe present invention are capable of being incoφorated in the form of a variety of embodiments, only a few of which have been illustrated and described above. The invention may be embodied in other forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive, and the scope ofthe invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency ofthe claims are to be embraced within their scope.

What is claimed is:

Claims

1. An angioplasty syringe for inflating and deflating an angioplasty balloon catheter and for maintaining therewithin a predetermined pressure created by relative movement of components ofthe syringe, comprising: a barrel; 5 a plunger disposed at least partially within the baπel; and reinforcing means disposed about at least a portion ofthe baπel such that the baπel retains its shape upon the generation of pressure within the baπel.

2. A syringe as defined in claim 1 , wherein the reinforcing means comprises a sleeve. o

3. A syringe as defined in claim 1 , wherein the reinforcing means is disposed about a plunger insertion end ofthe baπel.

4. A syringe as defined in claim 1 , further comprising: a plurality of longitudinally extending ridges disposed on and radially spaced about the periphery of at least a portion ofthe baπel; and 5 a plurality of longitudinally extending channels formed in the inner surface of said reinforcing means and configured to receive said plurality of longitudinally extending, radially spaced ridges.

5. A syringe as defined in claim 1, wherein the syringe is a locking syringe.

6. A syringe as defined in claim 1, wherein the reinforcing means has a 0 radiused internal surface adjacent a distal end ofthe reinforcing means.

7. A syringe as defined in claim 1, wherein the plunger comprises a set of external threads disposed on at least a portion of said plunger along the longitudinal axis thereof which threadably engage a set of internal threads within the baπel.

8. A syringe as defined in claim 7, wherein the reinforcing means is disposed 5 about an outer portion ofthe barrel adjacent the internal threads such that the reinforcing means maintains a relative position between the baπel and the plunger, ensuring engagement between the external and internal threads when the syringe is in the restricted mode.

9. A syringe as defined in claim 7, wherein: o the internal threads are located within the baπel at a plunger insertion end; and the reinforcing means is disposed about an outer portion of the barrel adjacent the internal threads.

10. A syringe as defined in claim 1, wherein: 5 the baπel includes a cap through which the plunger is disposed; and the reinforcing means is disposed about the cap.

11. A syringe as defined in claim 10, wherein: the cap is comprised of a cylindrical collar and a shoulder connected to the collar; and the reinforcing means is disposed about the cylindrical collar and, on one 5 end ofthe reinforcing means, engages the shoulder.

12. A syringe as defined in claim 1, further comprising a triggering means attached to the plunger for selectively retracting said external threads, such that when the triggering means is actuated, the external and internal threads maintain a position of disengagement, thereby enabling the plunger to be freely moved with respect to the 0 baπel.

13. A reinforced angioplasty syringe for inflating and deflating a balloon catheter and for holding a plunger in a selected position against a pressure created within a baπel by sliding the plunger to the selected position within the barrel, comprising: a baπel including a set of internal threads; s a plunger disposed as least partially within the baπel, the plunger comprising a set of external threads disposed on at least a portion of said plunger along the longitudinal axis thereof and which threadably engage the set of internal threads; and reinforcing means disposed about at least a portion ofthe baπel such that o the baπel resists deformation upon the generation of pressure within the syringe.

14. A syringe as defined in claim 13, wherein the reinforcing means comprises a sleeve.

15. A syringe as defined in claim 13, further comprising: a plurality of longitudinally extending ridges disposed on and radially 5 spaced about the periphery of at least a portion ofthe baπel; and a plurality of longitudinally extending channels formed in the inner surface of said reinforcing means and configured to receive said plurality of longitudinally extending, radiallv spaced ridges.

16. A syringe as defined in aim 13, wherein: 0 the reinforcing means is interference fit about the baπel; and the reinforcing means has a radiused internal surface adjacent a distal end ofthe reinforcing means.

17. A syringe as defined in claim 13, wherein the reinforcing means is disposed about an outer portion ofthe baπel adjacent the internal threads.

18. A syringe as defined in claim 13, wherein: the internal threads are located within the plunger insertion end of the baπel and the reinforcing means is disposed about an outer portion ofthe baπel adjacent the internal threads. 5

19. A syringe as defined in claim 13, wherein: the baπel includes a cap through which the plunger is disposed; the cap is comprised of a cylindrical collar and a shoulder connected to the collar; and the reinforcing means is disposed about the cylindrical collar and, on one o end ofthe reinforcing means, engages the shoulder.

20. A reinforced locking syringe for holding a syringe plunger in a selected position against a pressure created within a syringe baπel by sliding movement of the plunger to the selected position within the baπel, the syringe comprising: a baπel including a set of internal threads; s a plunger disposed at least partially within the baπel, the plunger comprising a set of external threads disposed on at least a portion of said plunger along the longitudinal axis thereof and which threadably engage the set of internal threads; triggering means attached to the plunger for selectively retracting said o external threads, such that when the triggering means is actuated, the external and internal threads maintain a position of disengagement, thereby enabling the plunger to be freely moved with respect to the baπel; and reinforcing means disposed about a proximal portion of the baπel for reinforcing the baπel so as to prevent deformation ofthe baπel upon generation 5 of pressure within the syringe.

21. A syringe as defined in claim 20, wherein the reinforcing means comprises a sleeve which is interference fit about the baπel, the sleeve having a radiused internal surface adjacent a distal end ofthe sleeve.

22. A syringe as defined in claim 20, wherein the reinforcing means is o disposed about an outer portion ofthe baπel adjacent the internal threads.

23. A syringe as defined in claim 20, wherein: the internal threads are located within a plunger insertion end ofthe barrel and the reinforcing means is disposed about an outer portion of the baπel adjacent the internal threads.

24. A syringe as defined in claim 20, wherein: the barrel includes a cap through which the plunger is disposed; the cap is comprised of a cylindrical collar and a shoulder; the reinforcing means is disposed about the cylindrical collar and, on one 5 end ofthe reinforcing means, engages the shoulder; and further comprising a plurality of longitudinally extending ridges disposed on and radially spaced about the periphery of said collar; and a plurality of longitudinally extending channels formed in the inner surface of said reinforcing means and configured to receive said plurality of 0 longitudinally extending, radially spaced ridges.

25. A reinforced syringe which may be selectively operated between a free position and a locked position, comprising: a baπel; a cap attached to one end of the baπel, the cap having a set of internal 5 threads; a plunger extending through the cap, the plunger comprising a set of external threads disposed on at least a portion of said plunger along the longitudinal axis thereof and which threadably engage the set of internal threads; triggering means attached to the plunger for selectively retracting said o external threads, such that when the triggering means is actuated, the external and internal threads maintain a position of disengagement, thereby enabling the plunger to be freely moved with respect to the baπel; and a sleeve disposed about an outer portion of the cap adjacent the internal threads such that the sleeve maintains a relative position between the baπel and 5 the plunger, ensuring engagement between the external and internal threads when the syringe is in the restricted mode.

26. A syringe as defined in claim 25, further comprising: a plurality of longitudinally extending ridges disposed on and radially spaced about the periphery of said cap; and 0 a plurality of longitudinally extending channels formed in the inner surface of said sleeve and configured to receive said plurality of longitudinally extending, radially spaced ridges.

27. A syringe as defined in claim 25, wherein: the cap is comprised of a cylindrical collar and a shoulder connected to 5 the collar; and the sleeve is disposed about the cylindrical collar and, on one end ofthe sleeve, engages the shoulder.