Abstract:
A cartridge interface assembly ( 80 ) characterized by a driving plunger ( 82 ) including an outer shaft ( 84 ), and a driver ( 86 ) including an inner shaft ( 88 ) movable telescopically with respect to the outer shaft ( 84 ), wherein rotation of the driver ( 86 ) causes the driving plunger ( 82 ) to advance in a direction away from the driver ( 86 ), and wherein the cartridge interface assembly ( 80 ) is inserted in a cartridge ( 22 ) in which a plunger ( 24 ) is slidingly disposed, and rotation of the driver ( 86 ) causes the driving plunger ( 82 ) to advance distally in the cartridge ( 22 ) until abutting against the plunger ( 24 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a section 371 of International Application No. PCT/US2011/021605, filed Jan. 19, 2011, which was published in the English language on Jul. 28, 2011 under International Publication No. WO 2011/090956 which is a continuation-in-part of U.S. application Ser. No. 12/689,250 filed Jan. 19, 2010, the disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to external drug pumps, and particularly to an assembly for pushing a drug from a cartridge, in which the assembly interfaces between an actuator, e.g., a motor, and a pushing device, e.g., a plunger in the cartridge. 
     BACKGROUND OF THE INVENTION 
     External drug pumps are typically used to deliver to patients substances which contain large molecules which cannot be digested when administered orally, such as insulin. Typically, the pump is adhered to the abdomen of the patient and delivers the substance to the patient via a cannula or needle that is inserted into the patient&#39;s skin. 
     PCT Patent Application PCT/IL2008/001312 (published as WO 2009/044401) to Gross and Cabiri (as well as U.S. patent applications Ser. Nos. 12/244666 and 12/244668, the disclosures of which are incorporated herein by reference), describes an external drug pump. In this pump, a cartridge is provided that contains a substance to be administered to a subject. (The terms “drug” and “substance” are used interchangeably throughout the specification and claims, and encompass any material administered to a subject. The term “cartridge” throughout the specification and claims encompasses any container for a drug, such as but not limited to, a cartridge, vial, syringe, bottle, ampoule and many more, and is not limited to any size or shape.) 
     The cartridge is sealed by a stopper, and has first and second threaded elements (e.g., a screw and a nut) that are threadedly coupled to each other. The distal end of the second threaded element defines a coupling portion that couples the second threaded element to the stopper. The first threaded element is rotatable with respect to the cartridge, and is linearly immobile with respect to the cartridge during rotation of the first threaded element. The first threaded element, rotated by a motor, is configured to linearly advance the stopper and at least the distal end of the second threaded element toward the distal end of the cartridge, without substantially rotating the second threaded element and the stopper. 
     The following is provided to facilitate understanding of the above described assembly. 
     Reference is made to  FIG. 1 , which illustrates the relevant elements of the prior art cartridge assembly of WO 2009/044401 (based on  FIG. 4  of that application), wherein a cartridge  22  is inserted into a housing base. 
     The distal end of cartridge  22  is inserted into a cartridge piercing mechanism  44 , which pierces a seal at the distal end of cartridge  22  having a stopper  24  therein (the stopper being an example of a plunger, piston or pushing device; the stopper will also be referred to as a plunger). Cartridge  22  is then lowered into the housing base. Typically, opposing resilient arms  70  support the cartridge upon the housing base. As cartridge  22  is lowered into the housing base, a first cog  52  engages a second cog  54 . (First cog  52  is rotated by the motor, not shown here.) In some applications, before insertion of cartridge  22  into the housing, first threaded element  26  protrudes a distance h from the proximal end of the cartridge. The proximal end of the first threaded element (or of second cog  54 ) comprises a rounded portion  74 . Portion  34  of the housing base comprises an angled face  76 . As rounded portion  74  slides past the angled face, the first threaded element is pushed the distance h inside the cartridge. As a result, the first and second threaded elements  26  and  28  and the stopper  24  are displaced towards the distal end of the cartridge  22 . During operation, the motor (not shown) turns cog  52 , which turns cog  54 . This linearly advances stopper  24  towards the distal end of the cartridge  22 , thereby administering the substance from cartridge  22 . 
     Reference is now made to  FIG. 2 , which illustrates cartridge  22  with plunger  24  in an initial position before cartridge  22  has been filled. The cartridge is either pre-filled by the manufacturer or filled by the user, such as with a hypodermic needle  15  inserted through a septum  17  in cartridge  22  ( FIG. 3 ) or through a septum  19  in the housing of the drug pump ( FIG. 4 ). As shown in  FIG. 3 , the plunger  24  moves linearly in the cartridge  22  as the cartridge is filled. Because no two cartridges will be filled with exactly the same amount of substance, such as due to tolerances, different injected volumes, different diameters or other dimensions, different plunger shapes, air bubbles or other factors, there is unfortunately no definitive position of the plunger  24  after cartridge  22  has been filled. This can cause a problem because it is possible that the overall length of the geared and threaded mechanism (which is predefined) that interfaces with plunger  24  may not meet the filled position of plunger  24  (which is unknown), thereby causing a problem to properly push against plunger  24  in order to administer the substance. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide an improved assembly for pushing a drug from a cartridge, in which the assembly interfaces between an actuator, e.g., a motor, and a pushing device, e.g., a plunger in the cartridge, as is described more in detail hereinbelow. The invention solves the above mentioned problem of the prior art. Although the invention is described with reference to PCT Patent Application WO 2009/044401, nevertheless it is understood that the invention is applicable for many types of motor-driven drug cartridges. 
     There is thus provided in accordance with an embodiment of the present invention a cartridge interface assembly including a driving plunger including an outer shaft, and a driver including an inner shaft movable telescopically with respect to the outer shaft, wherein rotation of the driver causes the driving plunger to advance in a direction away from the driver, and wherein the cartridge interface assembly is inserted in a cartridge in which a plunger is slidingly disposed, and rotation of the driver causes the driving plunger to advance distally in the cartridge until abutting against the plunger. The driver may include a gear wheel. The inner shaft may mate with an intermediate shaft, and the intermediate shaft may mate with the outer shaft, so that the shafts are movable telescopically with respect to one another. 
     In accordance with a non-limiting embodiment of the present invention the inner shaft is threadedly received inside a hollow portion of the intermediate shaft, and the intermediate shaft is threadedly received inside a hollow portion of the outer shaft. 
     There is also provided in accordance with an embodiment of the present invention a method for interfacing between a driver and a plunger slidingly disposed in a cartridge, the method including inserting a cartridge interface assembly in the cartridge, the cartridge interface assembly including a driving plunger including an outer shaft, and a driver including an inner shaft movable telescopically with respect to the outer shaft, and rotating the driver to cause the driving plunger to advance distally in the cartridge until abutting against the plunger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
         FIG. 1  is a simplified illustration of a prior art cartridge assembly; 
         FIG. 2  is a simplified illustration of the prior art cartridge with plunger in an initial position before the cartridge has been filled; 
         FIG. 3  is a simplified illustration of filling the prior art cartridge with a hypodermic needle inserted through a septum in the cartridge; 
         FIG. 4  is a simplified illustration of filling the prior art cartridge with a hypodermic needle inserted through a septum in a housing of a drug pump; 
         FIGS. 5 and 6  are simplified pictorial and sectional illustrations, respectively, of a cartridge interface assembly including a driving plunger, constructed and operative in accordance with an embodiment of the present invention; 
         FIGS. 7 and 8  are simplified illustrations of the cartridge interface assembly inserted in a cartridge, respectively before and after the driving plunger abuts against the plunger of the cartridge, in accordance with an embodiment of the present invention; 
         FIGS. 9 and 10  are simplified illustrations of a cartridge interface assembly, constructed and operative in accordance with another embodiment of the present invention, about to be screwed into a plunger of a cartridge, with the driver (gear wheel) moved away from, and abutting against, the body of the cartridge interface assembly, respectively; and 
         FIGS. 11A and 11B  are close-up pictorial illustrations of the cartridge interface assembly of  FIGS. 9 and 10 , showing a locking assembly, constructed and operative in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Reference is now made to  FIGS. 5 and 6 , which illustrate a cartridge interface assembly  80 , constructed and operative in accordance with a non-limiting embodiment of the present invention. 
     Cartridge interface assembly  80  includes a driving plunger  82  at the distal end of an outer shaft  84 . A driver  86 , such as but not limited to, a gear wheel, includes an inner shaft  88 . Inner shaft  88  is received inside a hollow portion of an intermediate shaft  90  and threadedly mates therewith. Intermediate shaft  90  is in turn received inside a hollow portion of outer shaft  84  and threadedly mates therewith. The shafts  84 ,  88  and  90  are arranged to move telescopically with respect to one another. Outer shaft  84  may further include a proximal O-ring  92 . The driving plunger  82  and O-ring  92  are preferably made of an elastomer, such as natural or synthetic rubber. The other parts may be made of plastic or metal. 
     In an alternative embodiment, the intermediate shaft  90  may be omitted and inner shaft  88  and outer shaft  84  may be arranged to move telescopically with respect to one another. In further alternative embodiments, there may be more than three shafts arranged to move telescopically with respect to one another. 
     Reference is now made to  FIG. 7 , which illustrates the cartridge interface assembly  80  inserted in cartridge  22 . Driving plunger  82  is initially distanced somewhat from plunger  24  of cartridge  22 . Rotation of driver  86  (such as by meshing with a rotating motor not shown) causes inner shaft  88  to rotate, which causes intermediate shaft  90  to rotate and advance linearly towards the distal end of cartridge interface assembly  80 , that is, in the direction towards driving plunger  82  as indicated by arrow  91 . The distal movement of intermediate shaft  90  in turn causes outer shaft  84  to advance distally together with driving plunger  82 . The friction of driving plunger  82  against the inner wall of cartridge  22  is such that it is much easier for driving plunger  82  to move linearly than to rotate, such that the rotation of inner shaft  88  and intermediate shaft  90  cause driving plunger  82  to advance distally in cartridge  22  until driving plunger  82  abuts against plunger  24  as shown in  FIG. 8 . In an alternative embodiment, driving plunger  82  is allowed to rotate somewhat as it advances linearly until it abuts against plunger  24 . In another alternative embodiment, driving plunger  82  does not need to touch the inner wall of cartridge  22  and advances distally in cartridge  22  until it abuts against plunger  24 . 
     Thus, with the present invention, no matter what the final position of plunger  24  is after filling cartridge  22  with the substance to be administered, the driving mechanism for pushing plunger  24  will always properly contact plunger  24  via cartridge interface assembly  80  due to the distance compensating action of cartridge interface assembly  80 . 
     Reference is now made to  FIGS. 9 and 10 , which illustrate an alternative embodiment of the cartridge interface assembly, with like elements being designated by like numerals. In this embodiment, a cartridge interface assembly  100  can be connected to a plunger  124  by a screw connection. The plunger  124  is formed with a threaded hole  126 . The cartridge interface assembly  100  includes a threaded fastener  102  protruding from a distal end thereof, formed with male threads that correspond to the threaded hole  126 . The threaded hole  126  and threaded fastener  102  are formed with right-hand (clockwise) threads. Accordingly, the telescoping shafts are formed with left-hand (counterclockwise) threads, so as to be opposite in direction to the threaded connection of the threaded fastener  102  into the threaded hole  126 . The telescoping shafts of cartridge interface assembly  100  (such as the telescoping shafts  84 ,  88  and  90  of the first embodiment, not shown here) are rotated clockwise (as viewed from the distal end of driver  86 ) during operation in order to advance linearly towards the distal end of the cartridge interface assembly (as described above). 
     It may be desirable to supply the cartridge interface assembly  100  with the telescoping shafts fully inside a body  103  of the assembly  100  so that the driver  86  (shown in the illustrated embodiment of  FIGS. 9 and 10  with a double gear wheel, but the invention is not limited to such a gear wheel) abuts against the proximal end of the body  103  of the cartridge interface assembly  100  as seen in  FIG. 10 . If the telescoping shafts are not turned tightly into the body to the position of  FIG. 10 , it may be possible for the shafts to unscrew during transportation and handling before assembly, with the result that the position of  FIG. 10 , which is the desirable position for assembly with the cartridge plunger, is not maintained. On the other hand, if the driver  86  is tightened too much against the body of assembly  100  in an effort to maintain the closed position of  FIG. 10 , this can increase the torque necessary for the motor to overcome the tight connection in order to start turning the driver  86 , thereby overburdening the motor. 
     To solve this double problem (possible opening of telescoping shafts or the driver being tightened too much), a locking assembly is provided with the assembly  100  as is now described with reference to  FIGS. 11A and 11B . 
     Driver  86  is formed with a recess  104 , bounded by a wall  105  and a first locking tooth  106 . The proximal end of the body  103  of the cartridge interface assembly  100  is formed with a second locking tooth  108 . In the final position shown in  FIGS. 11A and 11B  (that of  FIG. 10 ), second locking tooth  108  is received in recess  104 . The first and second locking teeth  106  and  108  are formed with slanted walls  110  and  112 , respectively. The slanted walls  110  and  112  can glide over each other in the clockwise direction, meaning that the second locking tooth  108  is free to move in and out of recess  104  in the clockwise direction. This permits rotation of driver  86  in the clockwise direction, which is the direction the motor turns driver  86  to advance the telescoping shafts distally. However, the second locking tooth  108  cannot move past wall  105 , which means the second locking tooth  108  is cannot move past recess  104  in the counterclockwise direction, thereby preventing driver  86  from being unscrewed away from the proximal end of the body  103 . 
     Thus the locking assembly of the first and second locking teeth  106  and  108  enables easy assembly of the telescoping shaft assembly with the plunger  124 , and attains and maintains the final desired position of the driver  86  (i.e., the cartridge gear final position). The locking assembly prevents the telescoping shaft assembly from opening during transportation and handling, and ensures a small opening torque during operation. 
     It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of the features described hereinabove as well as modifications and variations thereof which would occur to a person of skill in the art upon reading the foregoing description and which are not in the prior art.