Abstract:
The injection syringe for injecting two liquids has a cylinder within which there are displaceably arranged in a liquid-tight fashion a piston as well as a separator piston member. The separator piston member divides the internal space of the cylinder into a first front compartment and a second rear compartment and is provided with a spacer rod arranged to be displaced in a liquid-tight fashion within a bore of the piston. Retaining or holder means ensure that the separator piston member maintains a constant spacing from the piston while the first liquid in the first front compartment is being ejected, whereas the separator piston member and the piston are displaceable relative to each other during ejection of the second liquid. The dual-liquid injection syringe is particularly utilized in computerized tomography for injecting a contrast medium and a flushing medium.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to the commonly assigned, copending U.S. application Ser. No. 436,307, filed Oct. 25, 1982, entitled &#34;Injection Syringe For The Successive Injection Of Two Liquids Into The Blood Vessels Of Living Bodies&#34;. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a new and improved construction of an injection syringe, also simply referred to as a syringe, for the successive injection of two liquids or agents into the blood vessels of living bodies or the like. 
     In its more particular aspects, the syringe for the successive injection of two liquids, especially although not exclusively, a liquid contrast agent or medium and a flushing agent or medium, into the blood vessels of living bodies, is of the type comprising a cylinder provided at one end thereof with an attachment or connection flange and at the other end thereof contains, at the region of an outlet or discharge opening, a catheter connection or equivalent structure. A piston member can be inserted into the cylinder, so as to be displaceable therein in a liquid-tight manner. 
     Particularly in the field of computer tomography an injection technique is gaining increasing importance, wherein immediately after injecting a contrast medium there is injected a physiological saline or salt solution. However, with the state-of-the art syringes, for instance as disclosed in Swiss Patent No. 580,427, granted Aug. 31, 1976, there only can be injected during one working operation a single liquid. Thus, there must be employed in each case two syringes, each of which is filled with a respective liquid and each of which is provided with a respective drive. Apart from the high costs involved with the employment of two syringes and two drives the use of two systems requires a correspondingly greater expenditure in terms of servicing and operating the same as well as monitoring such systems. 
     SUMMARY OF THE INVENTION 
     Therefore, with the foregoing in mind it is a primary object of the present invention to provide an improved construction of syringe for the successive injection of two liquids in a manner which is not afflicted with the aforementioned drawbacks and limitations of the prior art proposals. 
     Another and more specific object of the present invention aims at the provision of a new and improved construction of a syringe of the aforementioned type, by means of which it is possible to effectively inject in succession two liquids, and wherein there are effectively complied with the high requirements as concerns reliability and accuracy which are placed upon such medical equipment. 
     Still a further significant object of the present invention is directed to a new and improved construction of a syringe for the successive injection of two liquids, which syringe is relatively simple in construction and design, quite economical to manufacture, extremely easy to use, and not readily subject to breakdown or malfunction. 
     Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the syringe of the present development is manifested by the features, that there is provided a separator piston member which is disposed in the cylinder intermediate the piston and the outlet or discharge opening to separate the two liquids. A spacer rod extends substantially in parallelism with respect to the cylinder axis and is mounted at the separator piston member. Retaining means serve to hold the spacer rod in an axial bore of the piston during ejection of the first liquid, and the spacer rod is movable in a liquid-tight fashion in the axial bore during ejection of the second liquid. 
     The retaining or holder means may be structured as locking or latching means comprising at least one locking spring mounted in a counterbore of the piston, and there is provided at least one detent at the locking spring, said detent latching into a recess formed at the circumference of the spacer rod. 
     The separator piston member of the injection syringe according to the invention may have a convexly, preferably conically-shaped front face and a convexly, preferably conically-shaped rear face. The front face may be shaped so as to be adapted to the shape of the syringe cylinder at the outlet region thereof. 
     According to another aspect of the invention the separator piston member comprises a flexible plate at the end of the spacer rod which is remote from the piston. An annular support is provided for the flexible plate at the circumference thereof. A central closure member is arranged at the end of the spacer rod remote from the piston in order to closingly engage the plate. 
     In the injection syringe according to the invention, the first liquid is ejected from the first compartment by movement of the piston in conjunction with the separator piston member until the latter contacts the outlet end of the syringe cylinder. Subsequently, the second liquid is ejected from the second compartment by movement of the piston relative to the separator piston member after surmounting the resistance against such movement as provided, for example, by the locking means mentioned heretofore. In the case where the separator piston member includes a flexible plate, this flexible plate remains in closing engagement with the central closure member on the spacer rod as long as there is no pressure difference acting upon the flexible plate. After the first liquid has been ejected, the axial pressure on the piston produces a pressure difference at the flexible plate which, then, disengages from the closure member, so that the second liquid may be discharged through the outlet of the syringe. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
     FIG. 1 is a view, partially in section, illustrating the injection syringe according to the invention in a state prior to injection of the two liquids; 
     FIG. 2 is a view of the injection syringe shown in FIG. 1 in a state of injection of the second liquid contained in the syringe cylinder and following injection of the first liquid; 
     FIG. 3 is a view similar to that shown in FIG. 2 depicting the injection syringe in a final state after termination of the injection; 
     FIG. 4 is a sectional view of part of an injection syringe according to the invention which is equipped with a modified separator piston member and which is in a state of injection of the first liquid from the syringe cylinder; 
     FIG. 5 is a sectional view of the injection syringe shown in FIG. 4 in a state of injection of the second liquid from the syringe cylinder; and 
     FIG. 6 is a top plan view of the injection syringe shown in FIG. 4 and including the modified separator piston member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Describing now the drawings, it is to be understood that in order to simplify the illustration only enough of the construction of the injection syringe has been shown as needed for those skilled in the art to readily understand the underlying principles and concepts of the present invention. Turning attention now specifically to the drawing of FIG. 1, there is shown an injection syringe 1 comprising a cylinder 2, a piston or piston member 10 displaceable in the cylinder 2, a mounting flange 3 at the upper end of the cylinder 2, an outlet or discharge opening 6 at the lower end of the cylinder 2, and a connecting member 4 for connection to a catheter or the like (not shown). Into the internal space or chamber of the cylinder 2 of the injection syringe there is inserted the piston 10 and such is sealingly guided by a sealing ring 12 received in an annular groove 12a provided at the circumference of this piston or piston member 10 which is mounted for slideable axial movement within the cylinder 2. 
     The piston or piston member 10 has an axial bore 13 through which piercingly extends a spacer rod 70. A sealing ring 11 is accommodated in an annular groove 11a formed in the internal axial bore 13 of the piston 10, so that this piston 10 and the spacer rod 70 are movable in a liquid-tight fashion with respect to each other in axial direction. The spacer rod 70 passes through the internal axial bore 13 in the piston or piston member 10 and has a free end at which there is secured a separator member 30, here a separator piston member. The separator piston member 30 contains a substantially conical front face 32, a substantially conical rear face 35 and a substantially cylindrical face 31. A small cylindrical or annular gap 34 exists between the cylindrical face 31 of the separator piston member 30 and the inner cylindrical wall 5 of the syringe cylinder 2. The cylindrical gap 34 thus formed has a small width, for example, in the range of about 1 mm and has an axial length, for example, of about 15 mm, so that the admixing of both liquids 51 and 52 is negligibly small. By means of the separator piston member 30 two compartments 61 and 62 are formed within the cylinder 2, the first compartment 61 of which is defined by the outlet 6 and the front face 32 of the separator piston member 30, and the second compartment of which is defined by the rear face 35 of the separator piston member 30 and the front face of the piston or piston member 10. 
     The spacer rod 70 is retained by locking means 20 in a counterbore 13a formed at the end of the piston or piston member 10 which is remote from the separator piston member 30. The locking or latching means 20, for example, may comprise two locking or latching springs 21 and 21&#39;, each having a locking detent or nose 22 and 22&#39;, respectively. The locking detents 22 and 22&#39; are shown in engagement with associated recesses 23 and 23&#39;, respectively, formed at the circumference or outer surface of the spacer rod 70. 
     Another possibility of securing the separator piston member 30 against axial displacement at the piston or piston member 10 during ejection of the first liquid 51 from the first compartment 61 may be obtained by providing for sufficiently high friction between the spacer rod 70 and the piston 10 within the axial bore 13. This can be achieved, for example, by providing a sufficiently narrow bore 13. This has the advantage that the distance of the separator piston member 30 from the piston 10 may be continuously varied, whereby the volume of the rear compartment 62 becomes variable. 
     In the drawing of FIG. 1, the injection syringe according to the invention is shown in a state ready for the successive injection of the two liquids 51 and 52. The first liquid 51, which may be, for example, a contrast agent or medium, is located within the front compartment 61, while the second liquid 52, which may be, for example, a flushing agent or medium is present in the rear compartment 62. 
     For injection of the first liquid 51 the piston member 10 and the separator piston member 30 are conjointly displaced in a direction towards the outlet 6 until the front conical face 32 of the separator piston member 30 abuts against the conically-shaped bottom or base region 8 of the cylinder 2. The separator piston member 30 is still retained at a constant spacing from the piston member 10 by means of the spacer rod 70. As mentioned previously, the size or dimension of the cylindrical or annular gap 34 between the cylindrical wall 31 of the separator piston member 30 and the inner wall 5 of the cylinder 2 is appropriate to prevent any appreciable intermixing of the two different liquids 51 and 52 present in the compartments 61 and 62, respectively. In this state, when the separator piston member 30 abuts against the bottom 8 of the cylinder 2, the first liquid 51 has been ejected, whereas the second liquid 52 is still present completely within the rear compartment 62. 
     Now to inject the second liquid 52 the spacer rod 70 is released from the locking means 20 by exerting an increased pressure upon the piston member 10. Consequently, the locking springs 21 and 21&#39; are released or delatched from the recesses 23 and 23&#39;, respectively. The piston member 10, then, may be displaced relative to the separator piston member 30. By advancement of the piston member 10 the second liquid 52 is ejected through the cylindrical or annular gap 34 towards the outlet 6. FIG. 2 shows the inventive injection syringe in a state where the first liquid 51 has been completely ejected while the second liquid 52 has been only partially ejected. FIG. 3 shows the injection syringe according to the invention in a final state, in which both the first liquid 51 and second liquid 52 have been ejected from the injection syringe 1. 
     To ensure passage of the second liquid 52 after ejection of the first liquid 51 there are beneficially provided flow channels 33 at the front conical face 32 of the separator piston member 30. It has been found, however, particularly in the case of a physiological salt solution which is used as a flushing medium and which is contained in the second compartment 52, that a separator piston member having no flow channels 33 also may be utilized and does not cause any blockage at the region of the discharge opening or outlet 6. 
     FIGS. 4 to 6 of the drawings show a modified construction of an injection syringe for the successive injection of the two liquids 51 and 52 and which is equipped with a modified separator piston member 80. Otherwise, the injection syringe is essentially constructed the same as that shown in FIGS. 1 to 3, and thus, corresponding parts have been conveniently designated by generally using the same reference numerals. For simplicity, the drawings of FIGS. 4 to 6 show only those parts of the injection syringe which include the modified version of the separator piston member 80. 
     The separator piston member 80 will be seen to comprise a support ring 81, a flexible plate or lamellae 82 mounted thereto, and a central closure member 85 mounted at the spacer rod 30. The support ring 81 is retained at the spacer rod 70 by means of lateral struts 84 of which, for example, three are provided. During ejection of the first liquid 51, the flexible plate 82 or equivalent structure remains in the closed position due to the pressure equilibrium in both the front compartment 61 and the rear compartment 62. When the support ring 81 abuts a front cylindrical surface or edge 7 of the cylinder 2 and the pressure in the rear compartment 62 is increased, the flexible plate or lamellae 82 will automatically open, so that the second liquid 52 will pass through an opening 83 which is thus formed during further movement of the piston or piston member 10. 
     FIG. 6 shows a top plan view in axial direction of the separator piston member 80 shown in FIG. 4. The support ring 81, to which the circular flexible plate 82 is secured, will be clearly evident. The opening 83 in the plate 82 is closed in a plug-like manner by the closure member 85. 
     In the following description the filling of the inventive injection syringes with the two liquids 51 and 52 will be explained in greater detail. While the discussion will be made with reference to the syringe of FIGS. 1 to 3, it is analogously applicable to the modified syringe construction of FIGS. 4 to 6. 
     The empty syringe cylinder 2 is closed near the outlet 6 and completely filled with the second liquid 52 which may be, for example, a physiological salt solution which is to be subsequently injected. Then, the piston member 10, including the separator piston member 30 in its most extended or desired spaced position, is slowly introduced. The liquid passes through the cylindrical or annular gap 34 formed between the separator piston member 30 and the inner wall 5 of the cylinder 2 so as to fill the rear compartment 62. The slightly conical shape of the rear face 35 of the separator piston member 30 and the slightly conical shape of the front face 32 of the separator piston member 30 facilitate the filling operation which is to be performed with the exclusion of air. The resistance to the introduction of the piston member 10 strongly increases when the piston member 10 has become axially introduced to such an extent that the sealing ring 12 of the piston member 10 contacts the inner wall 2. The cylinder 2 is now reopened at the front end at the outlet 6 and the piston member 10 is then advanced by about 1 centimeter, and then, the cylinder 2 is connected to an injector. The front compartment 61 is then emptied of the remaining second liquid 52 by correspondingly advancing the piston member 10, and thereafter a contrast agent or medium is sucked-up through the outlet 6 into the first compartment 61 by retracting the piston member 10. 
     While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and and practiced within the scope of the following claims. Accordingly,