Abstract:
A syringe for an injector that has at its nozzle end a connection to the fluid delivery tubing that prevents, reduces, or eliminates fluid leaks, by virtue of a ridge on the external surfaces of the connector which engage to tubing. Furthermore, the syringe and injector are configured to permit the syringe to be oriented in more than one manner on the injector.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 10/990,587, filed Nov. 17, 2004, which is incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to disposable replacement syringes for patient fluid injectors and adapters for a fluid injector to accept the syringe. 
     BACKGROUND OF THE INVENTION 
     Injectors are devices that expel fluid, such as contrasting media, from a syringe and through a tube into a patient. The injectors are provided with an injector unit, usually adjustably fixed to a stand or support, having a drive that couples to the plunger of the syringe to drive it forward to expel fluid into the tube, or that may be driven rearward to draw fluid into the syringe to fill it. Usually the syringe is a disposable replacement type. 
     In the injection phase where the plunger is driven forward, pressures are developed in the syringe that range from, for example, 25 psi for some applications to over 1000 to 1200 psi for other applications. Syringes that contain fluid under the higher range of pressures are expensive and therefore can be impractical where the syringes are disposable. Thus, many injectors for high pressure applications have been provided with pressure jackets that are fixed to the injector units and into which the syringes are inserted. The pressure jackets contact the outer surfaces of the syringe to restrain the walls of the syringe against the internal pressures. Other syringes for lower pressure use do not have a pressure jacket. 
     The injectors described in U.S. Pat. No. 5,300,031; U.S. Pat. No. 5,451,211; and U.S. Pat. No. 5,658,261 use a syringe that must be oriented to a single position to orient the nozzle and tubing connector when the syringe is loaded in the injector. This required orientation hinders rapid attachment and replacement of the syringe. In addition, although the Luer connection, syringe/tubing connection, described in the above patents may be adequate for injector applications that use low pressures, leaks often occur when high pressure applications are used. Power injectors require the connection of the Luer lock system to be effective for pressures up to 1,200 p.s.i. Some users have attempted to remedy the leak problem by tightening the connection as much as possible. Over-tightened Luer connectors sometimes crack which compromises the seal. Another problem is that sometimes the connection sticks and the Luer lock cannot be disassembled. 
     Hence, there has been a need to more quickly load and unload disposable replacement syringes in injectors, and for injectors and replacement syringes that can accommodate a more efficient process of syringe replacement. There is also a need for a fluid tubing delivery system, such as a Luer lock system, that does not leak when used with power injectors. 
     SUMMARY OF THE INVENTION 
     The present invention provides injectors, syringe interfaces and syringes that address the needs for rapid loading of syringes and the prevention or elimination of fluid leaks between the syringe nozzle and fluid delivery tubing connection, a Luer lock connection. Specifically, the present invention provides a syringe for an injector that has at its nozzle end a connection to the fluid delivery tubing that prevents, reduces, or eliminates fluid leaks. The syringe can also be oriented in more than one manner on the injector. 
     Another objective provides a syringe adapter, interface, or rotatable cam that can be retrofitted to the faceplate of the injectors to engage a notch at the proximal end of the syringe casing (body). 
     An objective of the present invention to provide a method and apparatus by which replaceable syringes can be more efficiently loaded into and unloaded from injectors. 
     Another objective of the present invention is to provide an injector with a replacement syringe and a method of replacing the syringe in the injector that provides a more efficient replacement of the syringes in the injector. 
     A further objective of the present invention is to provide a replaceable syringe and method of syringe replacement with which the replacement of the syringe can be achieved with simple motions by the operator or with rapid operation of injector unit mechanisms. 
     An additional objective of the present invention is to provide a replaceable syringe positive, rapid and reliable engagement of the syringe with locking structure that holds the syringe in the jacket, engagement of the plunger drive and plunger drive coupling, or connection of the injection tube to the outlet of the syringe. 
     Another objective of the present invention is to provide an injector and syringe arrangement that minimizes or eliminates the probability of spillage or leakage from the syringe nozzle flowing into the injector equipment, and otherwise enhancing the ability to maintain sterility and cleanliness of the equipment. 
     In one embodiment, the front end of the syringe is formed of a separate pressure restraining cap made of material that is separate from the front wall of the syringe and may be reusable. With the cooperating structure of the jacket and the syringe, restraining of the pressure jacket along the front and sides of the syringe is provided where the jacket allows for the replacement of the syringe from the front. 
     In another embodiment of the present invention, the threads are engageable in multiple but a limited number of angular positions. Additionally, other keys and key ways carried respectively by the unit and by the syringe limit the angular position in which the syringe may be inserted into the jacket to a unique predetermined angular orientation. Four key ways, such as slots or notches, spaced around the back, rearward or proximate edge of the syringe body, engage tabs on the unit at the rear end of the pressure jacket and in cooperation with the syringe umbrella cap and mating end of the pressure jacket. 
     Replacement of the syringe begins, in the embodiments of the invention, with unlocking the syringe at its front end from the front end of the pressure jacket, by rotating the syringe with respect to the jacket, and by disengaging the plunger drive from the syringe plunger, alternatively by transverse translational or rotational motion, simultaneous with and linked to the motion that disengages the syringe from the jacket. The unlocking of the syringe from the jacket occurs, for example, by loosening mating threads at the front of the syringe and jacket. The twisting of the syringe in the jacket is linked to motion that either translates transversely or rotates a coupling on the syringe plunger out of engagement with the plunger drive. The syringe is then removed from the jacket through the open front end of the jacket. This removal may take place without retraction of the plunger drive should the drive be advanced in the pressure jacket at the time of disengagement from the plunger coupling. The used syringe may also be removed without disconnection of the disposable injection tubing from the nozzle of the syringe. 
     In another aspect, the present invention also provides a disposable syringe that also provides a tight seal at the syringe nozzle and fluid delivery tubing connection. 
     These and other objectives of the present invention will be more readily apparent from the following detailed description of the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a form of an injector embodying principles of the present invention. 
         FIG. 2  is an exploded perspective view of a portion of an embodiment of the injector of  FIG. 1 . 
         FIG. 3A  is a perspective view of a portion of the injector of  FIG. 2 . 
         FIG. 3B  is a cross-sectional view of the connector tip of the syringe within a receiving end of fluid delivery tubing. 
         FIG. 3C  is a cross-sectional view of an end of a fluid delivery tube installed in the connector tip of the syringe. 
         FIG. 4A  is a cross-sectional view along lines  4 - 4  of  FIG. 3A  illustrating a replaceable syringe unlocked from the housing after insertion into the pressure jacket and prior to locking thereto, or after unlocking from the pressure jacket and prior to removal therefrom. 
         FIG. 4B  is a perspective view of the notched proximal end of the syringe. 
         FIG. 5  is a cross-sectional view similar to  FIG. 4  but illustrating the syringe locked to the structure carried by the housing. 
         FIG. 6  is a cross-sectional view along the line  6 - 6  of  FIG. 5 . 
         FIG. 7  is an elevational diagrammatic illustration of the injector of  FIG. 1  with the pressure jacket and syringe removed, and showing the syringe locking structure in the locked position such as in  FIGS. 5 and 6 . 
         FIG. 8  is an elevational diagrammatic view similar to  FIG. 7  illustrating the syringe locking structure in the unlocked position such as in  FIGS. 2-4 . 
         FIG. 9  is an elevational diagrammatic view similar to  FIG. 7  illustrating the locking mechanism in the housing door release position. 
         FIG. 10  is a cross-sectional view through the housing of the injector taken along lines  10 - 10  of  FIG. 1  with the plunger drive disengaged from the syringe plunger coupling. 
         FIG. 11  is a view of a portion of  FIG. 10  illustrating the plunger drive longitudinally moving into engagement with the plunger coupling. 
         FIG. 12  is a view of a portion of  FIG. 10  illustrating the plunger drive in engagement with the plunger coupling. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As noted in the Background section, there is a need to more quickly load and unload disposable replacement syringes in injectors. A type of injector for the use of the present invention is described in U.S. Pat. No. 5,300,031; U.S. Pat. No. 5,451,211; and U.S. Pat. No. 5,658,261 which are incorporated by reference herein in their entirety. 
     Briefly, an example of an injector  10  with use of the present invention is illustrated in  FIG. 1 . The injector  10  includes a wheeled base  11  to the top of which is rigidly supported a vertically adjustable upstanding support column  12 . A control module platform  13  is supported at the top of the column  12 . Electrical power is communicated from a power cord (not shown) through the base  11  and the upstanding support  12  and through a power lead  15  to a control module  16  rigidly supported to the platform  13 . The control module  16  includes a programmable microprocessor (not shown) to which commands and programming codes are input through a keyboard  17  on the module  16 . The module  16  is also provided with an operator display  18  to aid in interfacing the input commands and injector status with the operator. Attached to the platform  13  is an articulating adjustable arm  19 . To the remote end of the arm  19  is adjustably supported the injection module unit  20 . 
     The injection module unit  20  of the embodiments of  FIG. 1  includes a housing  21  which contains the operating drive structure of the injector  10 . The housing  21  has a support bracket  23  fixed thereto and adjustably pivotally supported to the remote end  24  of the articulating arm  19 . The housing  21  has pivotally attached to the front thereof a door  25  at the front thereof which is pivotally connected to the housing  21  at a longitudinally extending pivot or hinge pin  26  ( FIG. 2 ) rigidly supported on the housing  21  and extending forward from the front of the housing  21 . 
     On the top of the housing  21  is an injector position and local control panel  27  having a position indicator scale  28  thereon, which displays the position of the injector drive to the operator. The panel  27  also includes a pair of forward and reverse drive direction control buttons  29 , which are selectively actuatable to activate a drive within the housing  21  in either the forward or reverse directions. 
     Extending forward from the front of the door  25  is an injector syringe and pressure jacket assembly  30 , the structure of which can be better understood with reference to  FIGS. 2-5  below. The syringe and jacket assembly  30  includes a hard plastic pressure jacket  31 , which may be of opaque or transparent material, a removable and replaceable disposable syringe  32 , which may be of opaque, transparent or semi-transparent material, and related structure hereinafter described. 
     The syringe  32  is disposable, and includes walls which will withstand only moderate or low pressure. The walls are usually outwardly deformable under operating pressures, particularly pressures of 300 psi or more. Such higher pressures are necessary to overcome pressure drops through the injection tubing at higher flow rates, which are often desirable. The jacket  31  is made of a stronger transparent material that will withstand the operating pressures. When the syringe  32  is contained in the jacket  31 , it is surrounded by the jacket  31  and supported by the jacket  31  against expansion caused by the fluid pressure within as the syringe  32  expands against the jacket wall. 
     The pressure jacket  31  has a generally cylindrical inner bore  33  extending therethrough from a proximate end  34  adjacent the door  25  to a remote end  35  of the pressure jacket  31  toward the front of the unit  20 . The bore  33  is dimensioned so as to receive through the remote end  35  the disposable syringe  32  and to support the syringe against expansion from fluid pressure within such fluid pressure may range to more than a thousand psi. The pressure jacket  31  has an annular flange  37  extending outwardly around the proximate end  34 . The flange  37  is integrally formed with the jacket cylinder and is shaped to conform to an annular recess  38  surrounding a circular hole  39  in the door  25  to which the jacket  31  may be assembled by insertion from the rear. The hole or opening  39  in the door  25  and the cylindrical bore  33  of the jacket  31  are concentric with a longitudinal axis  40  on which also lies an axis  41  of the syringe  32  when the syringe  32  is positioned in the bore  33  of the jacket  31 . The jacket  31  is firmly and rigidly attached to the door  25  with a pair of screws  43 , only one of which is shown, which are threaded into a pair of holes  44  in the back of the door  25  ( FIG. 2 ). An O-ring seal  46  surrounds the flange  37  of the jacket  31  in the recess  38  of the door  25 . 
     The syringe  32  includes a syringe case  50  formed of a single piece of molded plastic material, a pressure cap  51  and a plunger  54  ( FIGS. 3A ,  4 A- 5 ). The syringe case  50  includes a cylindrical syringe body  55  having an open proximate end  56  and a remote end  58  to which is integrally formed a conical front wall  57 . The front wall  57  is truncated at its forward end, to which is integrally formed an elongated neck  59  extending from the wall  57  at the center thereof. The neck  59  of the syringe case  50  has an orifice  60  ( FIG. 3A ) in its remote or distal end which communicates with an internal syringe cavity  61  formed of the interior of neck  59 , the interior of conical front wall  57  and the interior of cylindrical body  55  of the case  50  of the syringe  32 . The rear end of the cavity  61  is further defined by a forward facing conical surface  64  of the plunger  54 . The conical surface  64  is of a slope which conforms to the slope of the interior of the conical front wall  57 . The plunger  54  is slidable within the body  55  of the syringe case  50  such that the cavity  61  is of variable volume. 
     In one embodiment best seen in  FIGS. 3B and 3C , near the front or remote or distal end of the neck  59  of the syringe case  50 , a tubing connector  200  has an internally threaded section  66  configured to mate with thread  63  on the exterior of tubing  65 . In another embodiment, two or more threads may be on the exterior tubing  65 . 
     The tube connector  200 , also known as a Luer tip or Luer connection, on distal, or remote, end of neck  59  of syringe case  50  has a specific structure which enables it to connect to a fluid delivery tube  65  ( FIG. 3A ). As illustrated in  FIG. 3B , the connector  200  has about a six-degree taper  212  extending from the proximal end  205  to the distal end  210  of the connector  200 . The taper  212  includes at least one ridge  215 , or knurl along the outer surface of the taper  212  that acts as a sealing ring and is in contact with the inner surface  220  of the connecting end of tube  65 . 
     In another embodiment, the taper  212  includes at least two ridges or knurls  215 ,  225  along the outer surface of taper  212 . These sealing rings reduce, eliminate, or prevent leakage between the connector  200  and the connector of the delivery fluid tube  235 , and also facilitate connection and removal of tubing. One of the ridges  225  is located at the distal end  210  of the connector  200 . The second ridge  215  may be positioned at any location along the taper  212  such as midway between the proximal end  205  and distal end  210  of the connector  200 . 
     The functionality of ridges or knurls  215  and  225  is best seen in  FIG. 3C . When tubing  65  is connected to connector  200 , only the ridges  215 ,  225 , or sealing rings, of the connector  200 , are in contact with the inner surface  220  of the tube  65 , thus reducing the surface area contact of the connector  200 . This reduction in surface area increases contact pressure between the connector  200  and the tube  65 . The increased contact pressure provides a better seal at the connector  200 /tube  65  connection. Furthermore, the reduction in surface area reduces the friction between the tubing  65  and connector  200 , such that the tubing is inserted and removed with a reduced torque for a given contact pressure than would be the case in the prior art. The ridges or knurls  215  and  225  thus achieve two benefits of increasing contact pressure and improving sealing, and reducing friction to make insertion and removal easier. 
     Turning more specifically to  FIG. 4A , it may be seen that the cap  51  is generally conical in shape and has an inner rearward surface  75 , which conforms to the front surface of the conical wall  57  of the case  50  of the syringe  32 . In certain embodiments, the rearward conical surface  75  of the cap  51  may be bonded to the front surface of the conical wall  57  of the case  50  of the syringe  32 , or it may be formed integrally therewith, molded from the same plastic material as the case  50  of the syringe  32 . In the illustrated embodiment, the cap  51  is separate from the syringe body portion  55  and has a pair of holes or detents  76  into which fit a pair of projections  77  extending forward from and formed integrally on the outer surface of the conical wall  57  of the case  50  of the syringe  32 . The cooperation of the pins or projections  77  with the holes or detents  76  prevent the cap  51  from rotating with respect to the syringe case  50  when the cap  51  is mounted on the syringe  32 . 
     To hold the cap  51  against the conical wall  57  of the case  50  of the syringe  32 , six resilient tabs  78  are formed about a central inner hole  79  of the cap  51 . The tabs  78  are separated by six equally spaced radial slots  80  ( FIG. 3A ). The hole  79  in the cap  51  is equal to or only slightly greater in size than the circular forward end of the conical wall  57  of the case  50  of the syringe  32 . The neck  59  of the syringe  32  has an enlarged straight section  81  slightly greater in diameter than the hole  79  in the cap  51  and also greater in diameter than the forward end of the conical wall  57  of the case  50 , thereby forming a groove  82  at the juncture of the straight neck portion  81  with the conical wall  57  so that the tips of the tabs  78 , which are sufficiently resilient to slide over the enlarged neck portion  81  as the cap  51  is inserted on the case  50  of the syringe  32  with the hole  79  surrounding the neck  59  to snap fit into the groove  82 . 
     Referring to  FIGS. 2 and 4A , the syringe  32  includes structure that is configured to lock the syringe  32  to the front end of the jacket  31  by cooperating with mating structure on the jacket  31 . The jacket  31  has, spaced around the circumference thereof near the remote or front end  35  of the jacket  31 , four equally spaced outwardly projecting thread sections  85 . These thread sections  85  are slightly less than 45° in extension around the circumference of the jacket  31  and are spaced apart with gaps of slightly greater than 45°. The cap  51  has a cylindrical rim  87  in which are formed four similarly sized and spaced mating thread sections  86 . The thread sections  86  project inwardly toward the jacket  31  when the syringe  32  is positioned in the jacket  31 . As such, when the syringe  32 , with the cap  51  assembled to it is inserted into the jacket  31 , the threads  86  of the cap  51  pass through the spaces between the threads  85  on the jacket  31  to a point behind the threads  85 . When so inserted, the syringe assembly  32  with the cap  51  may be twisted clockwise 45° to tighten and thereby secure the cap  51  to the jacket  31  by engagement between the threads  85  and  86  as shown in  FIG. 5 , to thereby lock the syringe in the bore  33 . 
     The plunger  54  of the syringe  32  is molded of an elastomeric material. Preferably, the plunger  54  includes two portions molded of different materials and bonded together. These portions include a forward more flexible portion  90  in which is formed the forward conical surface  34 . This forward portion  90  has a pair of outwardly extending rings  91  formed in the periphery thereof to make sealing engagement with the inside of the wall of the cylindrical body  55  of the syringe case  50 . The rearward portion of the piston  54  is a flat circular surface to which is bonded the flat circular forward surface of a more rigid rear portion  93  of the piston  54 . The rear rigid portion  93  of the piston  54  is molded of a harder stronger plastic material and has a rearward facing circular surface  95  having a rearward extending coupling  96  integrally formed thereon at its center. The coupling  96  includes a rearwardly extending cylindrical shaft  97  on the axis  41  of the syringe  32  and a larger symmetrical cylindrical button  98  integrally formed at the rear end of the cylindrical shaft  97 . 
     At the forward end of the carriage  108  is supported a pair of hooked jaws  114  which are pivotally mounted at their rearward ends by a pair of pivot pins  115  to the carriage  108 . The jaws  114  are biased toward the axis  112  by a pair of balls  116   a  and  116   b  of resilient material positioned between the outside of the jaws  114  and an inner cylindrical wall  117  of a recess  118  formed in the forward end of the carriage  108 . The balls  116   a ,  116   b  are partially captured in depressions in the outer surfaces of the jaws  114 . The balls  116   a ,  116   b  bias the jaws toward their innermost position toward the axis  112 . The innermost position of the jaws is determined by a spacing block  119  on the axis  112  of the carriage  108  at the center of the cavity  118 . 
     When a syringe  32  is locked in the jacket  31  with its axis  41  and the axis  40  of the jacket  31  may be in alignment with the axis  112  of the shaft  105 , the plunger  54  may be located in the cylindrical body  55  of the syringe case  50  in a position forward of the remote end  56 . Preferably, however, the jaws  114  are displaced to the side of axis  112  of the shaft  105  so that as the jaws  114  and coupling tip  98  are in their disengagement position, maximum clearance is provided so that the syringe  32  may be inserted into the jacket  31  without the sterile internal walls of the syringe  31  touching the components of the drive, as illustrated in the figures. 
     In the engaging position, the jaws  114  are in alignment with the coupling  98  on the axes  40  and  41  of the jacket  32  and syringe  32 . In such a situation, the jaws  114  may be in a retracted position at the center of the opening  39  of the door  25  adjacent to the proximate end  34  of the jacket  31 , and out of engagement with the coupling  96  on the plunger  54 . From this position, operation of the motor  101  rotates the shaft  105  and drives the carriage  108  forwardly to move the jaws  114  toward and into engagement with the coupling  96  on the plunger  54 . This engagement takes place as shown in  FIG. 11  where a pair of tapered cam surfaces  120  at the forward interface of the tips of the jaws  114  engage the enlarged portion or button  98  of the coupling  96  to expand the jaws, as shown in  FIG. 11 , to snap around the button  98  of the coupling  96  to form a driving engagement between the drive assembly  100  and the coupling  96  of the plunger  54  as shown in  FIG. 12 . Once so engaged, any forward or reverse movement of the carriage  108  under the power of the motor  101  will cause the plunger  54  to be driven either forwardly or backwardly in the syringe body  55 . 
     Disengagement of the jaws  114  from the coupling  96  can thereafter be achieved by translational movement between the coupling  96  and the jaws  114  between a disengaged position as shown in  FIG. 4A  and an engaged position as shown in  FIG. 5 . When the plunger coupling  96  and the jaws  114  are disengaged, the syringe  32  can be replaced without the need to retract the carriage  108  of the drive  100 . This allows for rapid replacement of the syringe  32 . Preferably, the jaws  114  are either fully retracted toward the housing  21  where engagement by translation of the coupling  96  will occur, or the jaws  114  are sufficiently within the jacket prior to replacement of the syringe so that the coupling  96  of the replacement syringe  32  will not contact the jaws  114  except as the drive  100  is advanced. 
     If sterility is not a problem, the most time saving approach would be to insert the syringe  32  into the jacket  31  with its plunger all the way forward and the drive fully advanced so that, when the syringe is translated toward the jaws  114 , engagement will immediately occur and the plunger can be immediately retracted to fill the syringe. 
     When a syringe  32  is inserted into the jacket  31  when the plunger  54  is at its rearmost position toward the proximate end  56  of the syringe body  55 , the coupling  96  is in a position adjacent the proximate end  56  of the syringe body  55  and projecting rearwardly therebeyond. When in such a position, engagement between the jaws  114  and the coupling  96  is brought about by translational movement between the position shown in  FIG. 4A  and that shown in  FIG. 5 . In the unlocked or disengaged position shown in  FIG. 4A , the axes  40  and  41  of the jacket  31  and the syringe  32 , respectively, as well as the center of the opening  39  of the door  25 , lie spaced from and parallel to the axis  112  of the shaft  105  as shown in  FIG. 4A . In the locked or engaged position, the axis  112  of the shaft  105  is slightly eccentric relative to the axes  40  and  41  of the jacket  31  and syringe  32 , respectively, as shown in  FIG. 5 . This translational movement, the engagement and disengagement between the coupling  96  and the jaws  114  and the 45E rotational movement which secures the cap  51  to the pressure jacket  31  by engagement of the threads  85  and  86  are brought about by operation of a translating and locking mechanism  125 , which is best understood by reference to  FIGS. 2-9 . 
     The translating and locking mechanism  125  includes a syringe engaging device, or a cam and locking ring  127 , which is rotatably retained in a circular recess  126  in the back of the door  25 . The ring  127  has a generally semi-circular groove  130  in the back surface thereof for receiving a spring wire retaining clip  131  having a pair of looped ends  133  which extend through a pair of slots  134  in the rim of the ring  127  and into a selected one of three pair of diametrically opposed notches  135 ,  136  and  137  in the inner wall of the rim of the recess  126  in the door  25 . The three pair of notches  135 ,  136  and  137  represent three positions of the translating and locking mechanism  125  which are the locked, unlocked and release positions, respectively. The locked position of the mechanism  125  in which the loops  133  of the ring  131  are in the notches  135 , is that illustrated in  FIGS. 5-7  and  10 . The unlocked position, in which the loops  133  of the ring  131  are in the notches  136 , is that illustrated in  FIGS. 2-4  and  8 . The release position, in which the loops  135  of the clip  133  are in notches  137 , is that illustrated in  FIG. 9 . The ring  127  is moved among these three positions by a manually accessible handle  138  in the form of a cylindrical knob  139  rotatably attached to a lever arm  140  formed integrally and extending radially from the ring  127  through a slot  141  in the door  25  ( FIG. 1 ). The ring  127  is retained in the recess  126  by a pair of screws  143  which thread into countersunk holes  144  at the periphery of the recess  126  in the back of the door  25 . These screws  143  have enlarged heads  146 , which, when seated in the holes  144 , overlie the edge of the ring  127 , thereby securing it for rotatable movement within the recess  126 . 
     As shown in  FIGS. 2 and 6 , the ring  127 , or rotatable cam, has an inner periphery  149  which is larger than the circumference of the body  55  of the syringe case  50 . Accordingly, when the syringe  32  is inserted in the jacket  31 , the proximate end  56  of the syringe case  50  extends through and is surrounded by the inner periphery  149  of the ring  127  (rotating cam). A key, or keyway, engaging structure, in one embodiment, is in the form of four projections  251 ,  252 ,  253  and  254  ( FIGS. 4A ,  4 B) provided in the edge of the proximal end  56  of the body  55  of the syringe case  50 . The four projections  251 - 254  are equally spaced. 
     Formed integrally of the ring  127  and projecting inwardly from the inner periphery  149  thereof are three tabs or keys  155 ,  156  and  157 . The tabs  155 - 157  are unequally spaced around inner periphery  149 , such that the tabs or keys  155 ,  156  and  157  fit between the respective projections  251 - 254  in the proximate end  56  of the body  55  of the syringe case  50 , so as to rotate the syringe  32  as the mechanism  125  is rotated through actuation of the handle  138 , or alternatively, to rotate the mechanism  125  as the syringe  32  is rotated at its end. 
     Any one of the spaces between projections  251 - 254  may be engaged with the keys or tabs  155 - 157  of ring  127 . This allows the syringe  32  to be attached to the door  25  and pressure jacket  21  assembly in any one of four orientations as dictated by the four thread sections  85  of the cap  51 . The syringe may thus be retrofitted to the faceplates of the injectors described in U.S. Pat. No. 5,300,031; U.S. Pat. No. 5,451,211; and U.S. Pat. No. 5,658,261, incorporated herein in their entirety, since the tabs  155 - 157  in the ring  127  are compatibly positioned as compared to the injectors of these three patents. 
     The rotation of the mechanism  125  from the unlocked position to the locked position rotates the syringe  32  in the jacket  31  and rotates the cap such that its threads move from an unlocked position as shown in  FIG. 4A  to the locked position of  FIG. 5 , to secure the cap to the jacket  31  by the engagement and tightening of the threads  85  and  86 . 
     The translational movement of the axes  40  and  41  with respect to the axis  112  is achieved by a fixed cylindrical cam follower or pin  150  which projects outwardly from the fixed housing portion  22  behind the ring  127  and into a cam slot  154  formed therein. The slot  154  is shaped so that the axes  40  and  41  which remain fixed with respect to the ring  127 , along with the door  25 , the jacket  31 , the syringe  32  and all of the structure mutually carried thereby, are moved in relation to the axis  112  of the shaft  105  and the other structure mutually carried by the housing  22 , as the mechanism  125  is rotated. These axes move toward and away from each other in accordance with the shape of the slot  154  determined by the radial distance from the point along the slot  154  where it engages the pin  150  to the axes  40  and  41 . 
     The cam slot  154  in the ring  127  is shaped such that, when the mechanism  125  is in the locked position as shown, for example, in  FIGS. 6 and 7 , the distance between the pin  150  and the axes  40  and  41  is at a minimum and the axis  112  coincides with the axes  40  and  41 . This is illustrated in  FIGS. 5 and 7  wherein the coupling  96  is shown positioned between the jaws  114  and in mutual engagement therewith. When the mechanism  125  is in the unlocked position, with the loops  133  of clip  131  in the notches  136  ( FIG. 6 ) of the recess  126 , the pin  150  lies in the slot  154  in the position shown in  FIG. 8 , which is farther displaced from the axes  40  and  41  than in the position of  FIGS. 6 and 7 , so that the coupling  96  is translated to a position outside of the center line of the jaws  114 , as shown in  FIG. 8  and further illustrated in  FIG. 4A . 
     In the release position, as shown in  FIG. 9 , the pin  150  is positioned at the open end  160  of the cam surface of the slot  154  so that the door  25  can be rotated upwardly about the hinge pin  26 , as shown in  FIG. 9 , to open the space behind the door  25  for access thereto. This position may be used for cleaning the area behind the door  25  which is sometimes necessary because of possible leakage of fluid from the cavity  61  into the space behind the plunger  54 . This can possibly occur because the fluid within the cavity  61 , when being injected by forward advancement of the plunger  54 , may be of relatively high pressure in the range, usually over 200 psi. For applications such as the injection of contrasting fluid for CT scanning, pressure may typically be in the range of from 25 to 300 psi, while in some injection applications the pressure may range to 1200 psi or higher. 
     Leakage rearwardly along the exterior of the neck  59  of the syringe  32  can cause fluid to flow between the body portion  55  of the syringe  32  and the jacket  31 . For this reason, the cap  51  is caused to fit snugly against the forward surface of the conical portion  57  of the syringe  32  at least sufficiently to restrict the flow of this leaking fluid onto the neck  59 . This is assisted by the configuration of the cap  51  at the rim  87  thereof so as to divert away from the space between the syringe  32  and jacket  31  fluid which might leak from the nozzle. 
     As seen in  FIG. 2 , the front of the housing  21  has formed thereon a door stop  185  having a slot  186  formed therein for receiving a lug  187  of the door  25 , to restrain the door  25  against forward force exerted by the drive  100 . As seen in  FIGS. 4A and 5 , behind the front of the housing  21  adjacent the stop  185  is a magnetic sensor  188 , which is responsive to the presence of a magnet  189  in the ring  127 . The sensor  188  generates a signal to the control module  16  to activate the drive  100  only when the mechanism  125  is in its locked position. 
     The locking structure between the syringe  32  and the pressure jacket  31  should provide for retention of the syringe  32  in the jacket  31  against the force of the fluid pressure in the cavity  61  or axial force otherwise exerted on the plunger  54  by the drive  100 . This locking of the syringe  32  to the jacket  31  is preferably achieved, as shown in  FIG. 5 , by structure at or near the forward wall  57  of the syringe case  50 . 
     The invention has been described in the context of its preferred embodiments. It will be appreciated by those skilled in the art that variations and alternatives to the embodiments described may be employed without departing from the principles of the present invention. Accordingly, this patent is not intended to be limited except by the scope of the following claims.