Patent Document

This application is a continuation of the commonly assigned and now abandoned U.S. patent application Ser. No. 08/979,003, filed Nov. 26, 1997 and entitled “Front Loading Power Injector and Method of Loading Flanged Syringe Therein”; which is a continuation-in-part of now abandoned U.S. patent application Ser. No. 08/896,695, filed Jul. 18, 1997 and entitled “Adapter and Syringe for Front-Loading Medical Fluid Injector”; and are both hereby expressly incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to power injectors, and particularly to injectors of the front loading type, and to the loading of syringes into power injectors, particularly syringes of the flanged or otherwise rear loadable type. 
     BACKGROUND OF THE INVENTION 
     Power injectors are devices used to inject fluids at programmed or otherwise controlled rates or pressures into patients. Important uses include computed tomography (CT) and angiography, where a radiopaque contrast medium is injected into a patient&#39;s vascular system to enhance diagnostic images. With power injectors, a motor-driven ram advances the plunger of a syringe under the control, for example, of a microprocessor to provide control of injection parameters such as flow rate, flow volume and timing. Such injectors are often loaded with sterile empty syringes that are filled by drawing fluid from a supply into the syringe through the syringe nozzle by using the ram to draw the syringe plunger backward. In other situations, the injectors are loaded with prefilled syringes in which the fluid has been packaged in the syringe by media manufacturers. 
     Syringes of both the empty and the prefilled types are available in more than one design or style. The type of design or style of the empty syringes that are used by a practitioner are typically the choice, in part, of the practitioner and, in part, of the those selecting the injection equipment being used. With prefilled syringes, however, the choices of the practitioner are limited to the designs and styles provided by the prefilled syringe manufacturer, which may be limited due to the need of the manufacturer to submit the syringe and contents to various governmental approval processes. The time and costs involved in such processes as well as the costs of providing alternative syringe containers for each injection fluid product place practical and financial restraints on of the prefilled syringe manufacturer who might be attempting to provide a variety of physical syringe configurations in its product line. 
     A variety of syringe designs have been developed and are in use for both prefilled and user-fillable syringes. Many such syringes are provided with a radially outwardly projecting flange at their rearward ends which serve to hold or support the syringe against axial motion when force is applied between the flange and plunger by the power ram of the injector. Many syringes with radial flanges on their rearward ends were first developed for use in breech loading or rear loading injectors in which the rear loadable syringe is positioned behind a holder of the injector and translated forwardly, nozzle first, through an opening in the holder, so that the flange or other outwardly extending structure at the syringe rear will seat forwardly against the back surface of the holder. Usually the holder is in the form of a faceplate or door on the injector housing and opens by moving away from the injector housing, either in hinged or turret fashion, for the loading or unloading of the syringe into or from the injector. One such rear loading injector is described and illustrated in U.S. Pat. No. 4,695,271, which is assigned to the assignee of the present application, and is hereby expressly incorporated by reference herein. Injectors of this rear loading type were for many years a standard of the health care industry. 
     More recently, the assignee of the present invention has provided a front loading injector that receives front loadable syringes. A front loading injector is one in which a front loadable syringe is positioned in front of an opening in an injector holder and loaded into the holder by translating the syringe rearwardly, back end first, into the holder. These front loading injectors have a number of advantages that make them highly preferred. One such advantage is the ability to load the injector manually with a simple one handed motion, by merely rearwardly translating the syringe into an opening in the front of the injector, without opening a loading door, and then twisting or otherwise manipulating the syringe to lock it in place. Such a front loading injector is described and illustrated in U.S. Pat. No. 5,279,569, which is assigned to the assignee of the present application, and is hereby expressly incorporated by reference herein. 
     Notwithstanding the desirability of using front loadable syringes and front loading power injectors, it is often necessary to utilize prefilled or other syringes, which may be available only in a breech or rear loadable type. To accommodate practitioners in such situations, breech loading capability has been provided for front loading injectors of the type disclosed in U.S. Pat. No. 5,279,569, referred to above, by interchanging the syringe holding head structure of the front loading injector with a breech loading syringe holder that will accept flanged rear loadable syringes. The use of interchangeable heads nonetheless has required the practitioner to resort to the rear loading techniques of the older systems which still have the disadvantages that provided the motivation for their replacement. 
     Accordingly, there remains a need to provide the advantages of a front loading injector and the capability of using syringes, particularly prefilled syringes, of the rear loadable type, particularly those having flanged or other outwardly extending structure on their rearward ends that function to align or lock the syringe on the injector. 
     SUMMARY OF THE INVENTION 
     A primary objective of the present invention is to provide a power injector having the capability of being front-loaded with syringes, and more particularly with rear loadable, side loadable, hand operable and other syringes, including prefilled syringes and syringes having locking and aligning structure such as an outwardly extending flange at the rearward end thereof. A more particular objective of the present invention is to provide a front loading injector capable of being front loaded with syringes having flanges at the rearward end thereof and to provide a method of front loading such syringes into a power injector. 
     A further objective of the present invention is to provide a power injector, such as a front loading injector, with a alternative structure, such as a substitute syringe holder or faceplate, that will adapt an injector to be front loaded with syringes of the rear loadable type, particularly syringes having flanges at their rearward ends. 
     According to the principles of the present invention, a syringe holder is provided with a syringe receiving opening or cavity therein that is of a size and shape that will receive the rearward end of a breech loadable syringe when the syringe is translated axially rearwardly into the opening. The opening is provided with syringe gripping structure that moves from the periphery of the opening against the body of the syringe, to lock, align and orient the syringe in the opening. 
     In accordance with the preferred embodiment of the invention, an iris-like syringe holding mechanism is provided, such as, for example, a gripping mechanism including a plurality of jaws is arranged around the opening in a outwardly retracted position on the holder and are linked together. The jaws preferably function in an iris-like fashion, to reduce the size of the opening to that of the syringe body, thereby gripping the body immediately forward of the rearward end of the syringe. Structure on the rearward end of the syringe, such as a radially outwardly extending flange, for example of a type typical of a breech loadable prefilled syringe, is gripped in a slot between the jaws and a stop at the back of the opening, so that the syringe is locked in the opening, is aligned with its axis on the centerline of the opening and is oriented generally perpendicularly to the injector housing wall and parallel to and aligned with the injector ram. 
     In the preferred embodiment of the invention, the holder is removable, replaceable or exchangeable with holders of other configurations that are provided for supporting syringes of differing shapes or types, or for receiving syringes of the front loadable or rear loadable types. In an alternative embodiment of the invention, the holder with a syringe holding mechanism having iris like holding elements is provided as part of an injector. 
     With the present invention, breech loadable syringes, particularly prefilled syringes having various configurations of flanges, tabs or other outwardly extending structure at their rearward ends, are capable of being front loaded into and removed from the power injectors, and thereby have all of the advantages of front loadability, including those of high speed syringe replacement, the ability to load or remove a syringe with one hand, and the ability to remove a syringe while injection tubing remains connected to the syringe tip, and other advantages discussed in the incorporated patents cited above. The syringe holder of the present invention is capable of holding syringes with such radially or other outwardly extending structure on their rearward ends as well as syringes of a variety of other configurations, including syringes that lock to the injector at their rearward ends or elsewhere at other locations on the syringe. 
     These and other objectives of the present invention will be readily apparent from the following detailed description of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a front loading power injector according to principles of the present invention. 
     FIG. 2 is a partial cross-sectional view along line  3 — 3  of FIG. 1, showing the injector with its syringe gripping structure in a retracted position. 
     FIG. 3 is a view, similar to FIG. 2, with the gripping structure in a closed or locked position. 
     FIG. 4 is a cross-sectional view along line  4 — 4  of FIG.  3 . 
     FIG. 5 is a front view of an alternative embodiment of the power injector of FIG. 1, showing the syringe gripping structure in a retracted position. 
     FIG. 6 is a view, similar to FIG. 5, with the gripping structure in a closed or locked position. 
     FIG. 7 is a cross-sectional view along line  7 — 7  of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a power injector  10  of a type, for example, that is used for angiographic and CT injection. One such injector is described and illustrated in U.S. Pat. No. 5,279,569, which is assigned to the assignee of the present invention, and is expressly incorporated herein by reference herein. The injector  10  includes an injector housing  11  that contains a power driven ram  12 . The ram  12  is longitudinally extendable from the housing  11  in a direction normal to the front of the housing  11  by activation of a motor (not shown) contained within the housing  11 . The forward end of the ram  12  is extendable from a retracted position in which its forward end is located inside the housing  11 , as illustrated in FIG. 1, to an extended position in which its forward end has been advanced a considerable distance outside the front wall of the housing  11 , as more fully explained in the incorporated U.S. Pat. No. 5,279,569. The injector described in that cited patent has a door assembly that constitutes a syringe mounting head of a front loading type for receiving a front loadable syringe with the syringe being loaded therein by translating it rearwardly, back end first, into the front of the mounting head. 
     The embodiment of the invention illustrated in FIG. 1 is, however, equipped with a faceplate in the form of a syringe mounting head  15  that is an alternative to, or a replacement for, or otherwise exchangeable with, the front loading head described in the patent which is configured to receive a syringe that is particularly designed for front loading, and which has a rearward end of the same outer diameter and cross-section as the syringe body. The mounting head  15  of the embodiment of FIG. 1 is rather configured to receive a syringe  40  of a type that has been designed for breech loading into an injector of the rear loading type, where the syringe  40  is translated, front end first, through an opening from the rearward side of a loading door, which must be opened for the purpose of loading or unloading a syringe  40 . 
     The syringe  40  typically has a cylindrical syringe body  41  with a frusto conical front end  42  having a conical injection nozzle  43  at the front thereof. The syringe body  41  has a rearward end  44  provided with a radially outwardly extending flange  45 . The flange  45  is typically of uniform thickness and integrally formed with the syringe body  41  at its extreme rearward end. The flange  45  may be a ring shaped annular flange with a circular outer edge, but usually is provided with at least one flat edge or notch to angularly align the syringe or to prevent the syringe from rotating about its longitudinal axis. The flange  45  of the syringe  40  has a polygonal outer edge that will angularly orient, or prevent rotation of, the syringe  40  when mounted in an injector. As illustrated in FIG. 1, the syringe  40  is provided with a flange  45  having an outer edge of octagonal shape. Within the body  41  of the syringe  40  is a plunger  47  formed of a hard polymeric material which forms a slidable but sealable contact with the inside of the syringe body  41  and defines along with the body  41  a sealed cavity  48  within the body  41  which contains injection fluid  49 , preferably the syringe  40  when supplied from the manufacturer, that is, a prefilled syringe. 
     The head  15  preferably includes a casting  17  removably pivotally connected to the front of the housing  11  to a pivot shaft  16  and with a locking mechanism  25 , which illustrated in part in FIGS. 1-3, and as is more particularly described in the incorporated U.S. Pat. No. 5,279,569. The mechanism  25  functions to lock and unlock of the head  15  to and from the housing  11 , to couple the ram  12  to plunger  47  within the body  41  of the syringe  40 , and to lock the syringe  40  to the injector  10 . The mechanism  25  is provided with an operating lever  26 , illustrated in an unlocked or loading position in FIGS.  1  and  2 ., which is the position which allows the head  15  to be opened, removed and replaced and which allows syringes  40  to be loaded and unloaded from the mounting head  15 . The lever or handle  26  is connected to a disc  27  rotatably mounted to the casting  17 . The handle  26  is moveable to a locked position, illustrated in FIG. 3, which is the position at which the head  15  is locked to the injector  10 , the ram  12  is coupled to the syringe ram and the syringe  40  is locked to the injector  10 . 
     The casting  17  of the head  15  has an opening  30  therethrough, which is preferably of the same shape as the flange  45  of the syringe  40  and slightly larger in size to allow the flange  45  to be inserted into the opening  30 . The opening  30  is preferably flared outwardly on the forward side thereof to guide the flange  45  of a syringe  40  into the opening  30  when the syringe  40  is being loaded. The opening  30  is centered on an axis  31  which is perpendicular to the front of the housing  11 . The axis  31  is parallel to the path of the ram  12  and generally lies on the centerline of the ram  12  when the lever  26  is in its locked position. Behind the opening  30  is an annular stop  32  (FIG.  4 ), which lies in a plane that is oriented perpendicular to the axis  31 . The stop  32  may be integrally formed of or otherwise fixed to the disc  27 , which is centered to pivot on the axis  31 . The stop  32  lies at the back of a recess  34  formed in the disc  27 . The recess  34  has a depth approximately equal to the thickness of the flange  45 . The recess  34  is preferably of the same shape as the flange  45  to hold the syringe  40  against rotation in the opening  30  once the syringe  40  is mounted in the opening  30 . The stop  32  has an opening  33  therein to allow passage of the ram  12 . When the flange  45  of a syringe  40  is inserted through the opening  30  and is seated against the stop  32 , the axis of the syringe  40  coincides with the axis  31  of the opening  30 , whereby the syringe  40  is perpendicular to the faceplate  15 , and the syringe  40  is in its operating position on the injector  10 . 
     According to one embodiment of the invention, the locking mechanism  25  includes a iris-like gripping mechanism  50  for holding the syringe  40  firmly in its operating position in the holder  15 . The gripping mechanism  50  includes a plurality of gripping elements which preferably have gripping surfaces that encircle most of the circumference of the syringe body  31 . In this embodiment, a pair of jaws  51 , 52 , is provided, each jaw being pivotally connected to the housing  17  of the head  15  at respective pivot pins  53 , 54  which are fixed to the housing  17 . The jaws  51 , 52  have inner concave gripping surfaces  55 , 56  having curvatures that correspond to the curvature of the outer surface of the body  41  of syringe  40 . Preferably, the surfaces  55 , 56  of the jaws  51 , 52  each encompass an arc of between 90° and 180°, so that when the jaws  51 , 52  are closed (FIG. 3) the surfaces  55 , 56  substantially surround the body  41  of the syringe  40  and securely hold the syringe in the operating position. The jaws  51 , 52  are spaced forward of the stop  32  so that, when the syringe  40  is in its operating position, the syringe flange  45  is held flat against the stop  32  by the jaws  51 , 52 . 
     The jaws  51 , 52  are simultaneously moved between retracted positions (FIG. 2) and locked positions (FIG. 3) by a camming action of the mechanism  25 , which is provided by a pair of cam follower pins  57 , 58  mounted on the ring  27  to move with and be actuated by the handle  26 . A magnet  88  is provided on the jaw  52  which can be detected by a sensor (not shown) in the injector housing  11  in order to determine that the mechanism  25  is in its locked condition which enables, through controls (not shown) in the housing, the operation of the ram  12 . The pins  57 , 58  scribe an arc on a circle  60 , centered on the axis  31 , when the handle  26  is operated. The pins  57 , 58  move in arcuate slots  61 , 62  in the jaws  51 , 52 , respectively, so that, when the handle  26  is operated, the pins  57 , 58  move the slots  61 , 62  generally radially and thereby cam the jaws  51 , 52  to pivot on their respective pins  53 , 54  between their retracted positions, in which the surfaces  55 , 56  are displaced radially outward of the flange  45  to provide clearance for the flange  45  when the flange  45  moves between the opening  30  and the backplate  32  during loading and unloading, and their locked positions in which the jaws  51 , 52  seat snugly against the outside of the body  41  of the syringe  40  immediately forward of the flange  45 . When so actuated, the jaws  51 , 52  move generally radially inwardly or outwardly along a path that may be, but is not necessary normal to the outer surface  41  of the syringe  40 . 
     According to another embodiment of the invention, an alternative head  15   a  is provided in which the syringe  40  is held in its operating position by an alternative gripping mechanism  50   a  having a set of four slidable jaws  71 - 74 , as illustrated in FIGS. 5-7. Each of the jaws  71 - 74  has a rectangular cross-section when viewed from the axis  31 , and each is trapped to slide radially in a respective one of four rectangular slots  75  formed between respective pairs of adjacent ones of a set of four wedges  76 , which are fixed to the ring  27 , and between the casting  17  and the rotatable ring  27 . The jaws  71 - 74  have inner concave gripping surfaces  77  having curvatures that correspond to the curvature of the outer surface of the body  41  of syringe  40 , so that when the jaws  71 - 74  are closed (FIG. 3) the surfaces  77  substantially surround the body  41  of the syringe  40  and securely hold the syringe in the operating position. The jaws  71 - 74  are spaced forward of the stop  32  so that, when the syringe  40  is in its operating position, the syringe flange  45  is held flat against the stop  32  by the jaws  71 - 74 . 
     The jaws  71 - 74  rotate with the ring  27  and also simultaneously move between retracted positions (FIG. 5) and locked positions (FIG. 6) by the camming action of the mechanism  25   a . The gripping surfaces  77  of the jaws  71 - 75  have V-shaped notches  89  therein which line up with the corners of the recess  34  in the ring  26 . Each one of the jaws  71 - 74  is provided with a cam follower slot  78  in which is located a cam pin  79  which is fixed to the casting  17  and lies on a circle centered on the axis  31 . When the handle  26  is operated to move the ring  27 , the wedges  76  move with the ring  27  and rotate with them the jaws  71 - 74 . The movement of the jaws  71 - 74  moves the slots  78  along the fixed pins  79 , which causes the jaws  71 - 74  to move radially when the handle  26  is operated between their retracted positions, in which the gripping surfaces  77  are displaced radially outward of the flange  45  to provide clearance as the flange  45  during loading and unloading of the syringe  40 , and their locked positions snugly against the outside of the body  41  of the syringe  40  immediately forward of the flange  45  to hold the syringe  40  in position for operation. 
     Preferably, as illustrated in FIG. 3, the gripping surfaces, such as surfaces  55 , 56  of jaws  51 , 52 , span at least approximately 25% of the circumference of the syringe for many syringes. In the embodiment illustrated, the jaws  51 , 52  have spaces  81 , 82  between them that each span no more than approximately 10-20% of the circumference. With some syringes, it is preferred that the gripping surfaces span at least approximately 65% of the circumference and in addition or in the alternative, that spaces between contacting portions of the surfaces by not more than approximately 95% of the circumference of the syringe. For example, surfaces  77  of jaws  71 - 74  in FIG. 6, each have two arcs spaced by a V-shaped notch  89  of less than about 3 to 5% of the circumference, with the spaces  83  between the jaws  71 - 74 , when the jaws are in the locked position, being also spanning less than approximately 3 to 5% of the circumference, leaving about 65% of the circumference cumulatively spanned by the surfaces  77 . 
     While the jaws  51 , 52  and  71 - 74  are referred to herein as gripping jaws, these jaws may or may not actually squeeze radially inward on the syringe  40 . What is preferred is that they contribute to the holding of the syringe in the opening  30 , particularly resisting the force exerted by the ram  12  in moving the plunger  47 . It is also important that, whatever holding action is performed by the gripping structure, the syringe  40  be held against the forces of operation without subjecting it to such forces and stresses that would cause any portion of the syringe  40  to fail. To this end, it is preferred that the jaws  51 , 52  or  71 - 74  engage the syringe  40  close to the body  41  of the syringe  40 , at the intersection of the flange  45  with the syringe body  41 , in a way that concentrates axial forces on the syringe  40  on the flange  45  as close to the body  41  as possible. This may be accomplished by configuring the rear edge of the inner surfaces  55 , 56  or  77  of the jaws  51 , 52  or  71 - 74  with a smaller radius than the radius  85  between the flange  45  and the outside of the syringe body  41 , as illustrated in FIG.  6 . This leaves small spaces  86  between the jaws and the syringe body  41  and spaces  87  between the jaws and the syringe flange  45 . 
     To load a syringe  40  into an injector  10 , a faceplate  15  or  15   a  having a gripping mechanism  50  or  50   a  is mounted onto the injector housing  11 , for example as a replacement to the standard faceplate with which the injector  10  is provided. If the syringe  40  has a plunger coupling that is not compatible with the coupling in the ram  12  of the injector  10 , a ram coupling adapter may be attached to the end of the ram  12  to provide coupling between the ram  12  and the coupling element (not shown) on the rear side of the plunger  47 . 
     With the lever  26  in its unlocked position, a syringe  40  is loaded into the opening  30  by translating the syringe  40  in a rearward axial direction, rear end first, until the flange  45  on the rearward end  44  of the syringe  40  passes through the opening  30  and rests in the recess  34  and against the stop plate  32  in the ring  27 . The tapered front of the opening  30  in the casting  17  guides the flange  45  such that the shaped perimeter thereof lines up with the similarly shaped periphery of the recess  34 . With the lever  26  so unlocked, the jaws  51 , 52  or  71 - 74  are in their retracted positions out of the path of the flange  45  as it is inserted into the opening. 
     When the rearward end  44  of the syringe  40  is completely seated in the opening, the lever  26  is moved to its locked position, which causes the jaws  51 , 52  or  71 - 74 , to move to their closed positions against the outside of the body  41  of the syringe  40 , gripping the body  41  and trapping the flange  45  between the jaws  51 , 52  or  71 - 74  and the ring  27 . This locking motion securely holds the syringe in position in the holder  15  on the housing  11  of the injector  10 , with its plunger  47  in line with the ram  12  and its centerline on the centerline of the holder  31  in alignment with the centerline of the path of the ram  12 . 
     Removal of the syringe is accomplished by moving the lever  26  to its unlocked position to move the jaws  51 , 52  or  71 - 74  to their retracted positions. With the injector that is disclosed in U.S. Pat. No. 5,279,569, this movement of the lever causes the locking mechanism  25 , 25   a  to slightly rotate the head  15  on the housing  11 , which translates the ram  12  out of alignment with the centerline  31  of the opening, thereby shifting the syringe  40  sideways and uncoupling the ram  12  from the syringe plunger  47 . The syringe  40  can thereby be manually removed from the injector  10  by translating it forwardly in the axial direction. If there is used injection tubing connected to the nozzle  43  after the use of the syringe  40 , the syringe  40  can nonetheless be removed without disconnecting the tubing from the syringe nozzle  43 . 
     Insertion of the syringe  40  into the injector  10  can also be carried out with a simple one handed motion, without separately operating the lever  26 . This is accomplished by inserting the syringe in the opening  30  and translating it axially rearwardly until the flange  45  is seated against the stop plate  32  in the recess  34 . Then by twisting the syringe  40  in the opening by less than 90°, preferably by about 45°, the ring  26  will turn, operating the locking mechanism  25 , which moves the faceplate  15  and syringe plunger  47  into alignment with the ram  12  and operates the gripping mechanism  50 , 50   a  to move the jaws  51 , 52  or  71 - 74  to their locked position. 
     The invention provides the user of a power injector with the ability to front load an otherwise rear loadable syringe, particularly a rear loadable syringe having a flange at the rearward end thereof. This provides the user with the advantages of front loadability. 
     Those skilled in the art will appreciate that the applications of the present invention herein are varied, and that the invention is described in preferred embodiments. Accordingly, additions and modifications can be made to the embodiments of the invention illustrated and described herein without departing from the principles of the invention.

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