Abstract:
A drug reservoir loading and unloading mechanism for drug delivery device using unidirectional rotated lead screw and method thereof are disclosed. The drug reservoir loading/unloading mechanism allows exchanging the drug reservoir quickly with very few steps and with more safety. The invention neither requires rewinding of the drive system either automatically or manually while replacing the drug reservoir nor requires an additional adapter to secure the drug reservoir.

Description:
FIELD OF THE INVENTION 
     The present invention is related to drug delivery devices, and in particular to a drug reservoir loading and unloading mechanism for a drug delivery device using a unidirectional rotated shaft. 
     BACKGROUND OF THE INVENTION 
     Conventional portable drug delivery systems are driven typically by a lead screw mechanism that displaces a plunger of a drug reservoir to deliver the medication. The drug reservoir is embedded usually in a compartment, in which the plunger of the drug reservoir has to be physically connected to the lead screw or to the nut due to the siphoning effect. This effect can result in an unintended drug delivery when the pulling force of the fluid column in a catheter is higher than the friction force of the plunger. 
     In drug deliver systems which reuse the lead screw (and the nut), the drug reservoirs are mostly inserted from the top side of the device. Once the drug reservoir is inserted into the device and the plunger is connected to the lead screw, the drug reservoir has to be secured by a lid or by an adapter. In these devices, to insert a new reservoir that is full of fluid, it is necessary to reverse the direction of the lead screw until the piston engagement returns back to the starting position. Thus the drive system must be able to be reversed in direction. On the other hand, in solenoid or non-motor driven systems, the piston engagement must be reset manually when placing a newly filled or partially filled reservoir. Both types of reset methods are problematic in different manners. 
     For example, in motor rewind configurations, the motor must be capable of being reversed requiring additional switches and have complex circuitry. In addition, piston sensing is required to shut off motor at a home position, which consumes extra battery energy, and it is not possible to accommodate a partially filled cartridge without manually adjusting the drive system. Similarly, manual reset configurations also have inherent problems. 
     Typically, manual reset configurations require a more complex housing and a sophisticated nut mechanism to manually engage and disengage the threads. In addition, the disengagement mechanism is both difficult and costly to design and manufacture, the mechanism must be safeguarded from any inadvertent actuation, additional wear issues must be considered, and manual dexterity is required to perform proper function. 
     SUMMARY OF THE INVENTION 
     It is against the above background that the present invention provides a drug reservoir loading and unloading mechanism for a drug delivery device using a unidirectional rotated shaft. The drug reservoir loading/unloading mechanism allows exchanging the drug reservoir quickly with very few steps and with more safety. For example, the invention does not require rewinding (reversing) of the shaft or drive system either automatically or manually while replacing the drug reservoir. 
     In one embodiment, a drug delivery device is disclosed and comprises a shaft, and a drive system operably connected to the shaft and configured to only rotate the shaft in a first direction. A drug reservoir having a plunger used to adjust a volume of the drug reservoir is also provided. A piston rod is operably connected at a first end to the plunger and provides threads. The piston rod is operably connected to the shaft, wherein the drug delivery device provides a secured position which permits the rotation of the shaft to drive the piston rod and move the plunger to adjust the volume of the drug reservoir, and an unsecured position which permits the drug reservoir to be removed unobstructed from the drug deliver device and replaced without having to rotate the shaft in a direction opposite to the first direction. 
     These and other features and advantages of the invention will be more fully understood from the following description of various embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of the various embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  is a perspective view of one embodiment of a drug delivery device with a disposable drug reservoir according to the present invention; 
         FIG. 2  is a partially sectioned and cut away side view of the drug delivery device of  FIG. 1  enclosing the disposable drug reservoir according to the present invention; 
         FIG. 3  is a partially sectioned and cut away side view of another embodiment of a drug delivery device shown holding a disposable drug reservoir in a lid thereof, positioned open, according to the present invention; 
         FIG. 4  is a partially sectioned and cut away side view of still another embodiment of a drug delivery device shown holding a disposable drug reservoir in a lid thereof, positioned open, according to the present invention; 
         FIG. 5  is an upper perspective view of another embodiment of disposable drug reservoir according to the present invention, which is suitable for use in the drug delivery device shown by  FIG. 4 ; 
         FIG. 6  is an upper perspective view of another embodiment of a drug deliver device and a disposable drug reservoir suitable for use therewith according to the present invention; 
         FIG. 7  is an upper perspective view of still another embodiment of a drug deliver device and a disposable drug reservoir suitable for use therewith according to the present invention; 
         FIG. 8  is an upper perspective view of yet another embodiment of a drug deliver device and a disposable drug reservoir suitable for use therewith according to the present invention; 
         FIG. 9  is a partially section view of the drug deliver device of  FIG. 8  shown with the disposable drug reservoir, also sectioned, locked therein; 
         FIGS. 10 and 11  are top views of a partially threaded nut using in the drug deliver device of  FIG. 8  according to the present invention; and 
         FIG. 12  is an upper perspective view of still yet another embodiment of a drug deliver device and a disposable drug reservoir suitable for use therewith according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of the embodiments of the invention, skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiment(s) of the present invention. Accordingly, the drawings are merely schematic representations, intending to depict only typical embodiments of the invention, and therefore should not be considered as limiting the scope of the invention. The invention will be described with additional specificity and detail through the accompanying drawings. 
     With reference to  FIG. 1 , a perspective view of a drug delivery device  10  according to an embodiment of the present invention is shown. In this illustrated embodiment, the drug delivery device  10  provides a disposable drug reservoir  12  having a piston rod  14  connected at one end to a plunger  16  that is used to adjust the volume of the drug reservoir  12  and to dispense a liquid drug contained therein. In one embodiment, the piston rod  14  is shaped to provide a channel or slot  15 . In one embodiment, at the free end of the piston rod  14 , a flexible nut segment  18  is provided integral with the slot  15  on the inside surface of the piston rod  14 . The nut segment  18  is threaded and is engageable with a shaft  20  of the drug delivery device  10 . 
     In the illustrated embodiment of  FIG. 1 , the shaft  20  of the drug delivery device  10  at one end is mounted for rotation to a shaft support  22  provided to a base  24  of the drug delivery device  10 . A lid  26  is mounted pivotally to the base  24 , such as for example, by a hinge  27  so that it can be opened and closed manually. Together, the base  24  and the lid  26  define a reservoir compartment, which is generally indicated by symbol  28 . The other end of the drive shaft  20  is operably connected to a drive system  30  of the drug deliver device  10 , which incrementally and unidirectionally rotates the drive shaft  20  upon activation. The drive system  30  may drive the shaft  20  by a motor actuator or by a limited stroke actuator such as Linear Piezoelectric Motor, Shape Memory Alloy, Piezo Bender, or the like. A ratchet mechanism (not shown) can be used to increase torque and to refine the resolution of the shaft&#39;s rotation. Examples of drive systems suitable for use with the present invention are disclosed by commonly owned and co-pending applications U.S. patent application Ser. Nos. 11/874,417; 11/946,905 and 11/936,813, the disclosures of which are herein fully incorporated by reference. 
     As shown by the illustrated embodiment of  FIG. 1 , the drug reservoir  12  is inserted at an angle to the shaft  20  into the reservoir compartment  28  of the drug delivery device  10 . In one embodiment, the drug reservoir  12  and the lid  26  each provide an engagement feature  32  and  34 , respectively, which associates together such the drug reservoir  12  engages first with and is held by the lid  26  while in the open position. In one embodiment, engagement feature  32  of the drug reservoir  12  is a raise portion providing a groove which accommodates slidably the complimentary shaped engagement feature  34  of the lid  26 . In such an embodiment, opening and closing the lid  26  disengages and engages, respectively, the nut segment  18  of the piston rod  14  with threads  36  of the shaft  20 , which in this embodiment is provided as a lead screw. 
     It is to be appreciated that opening lid  26  disengages the nut segment  18  from the threads  36  of the shaft  20 , and thus the drug reservoir  12  can then be pulled unconstructively out of the reservoir compartment  28 . In this manner, it is to be further appreciated that the drug delivery device  10  does not require rewinding of the drive system  30  automatically nor manually when it comes time to replace the drug reservoir  12 . In addition, as the nut segment  18  is integral with the drug reservoir  12 , thereby making it also disposable, the drug reservoir  12  can be replaced in fewer steps and with higher reliability as compared to drug deliver devices that do not have a nut segment integral with the disposable drug reservoir and/or which require rewinding of the drive system in order to replace the drug reservoir. A locking mechanism  37  may be provided to prevent inadvertent opening of the lid  26 . 
     Referring also to  FIG. 2 , the closed position of the lid  26  is shown with the nut segment  18  engaged with the threads  36  of shaft  20 . In one embodiment, the nut segment  18  is flexible such that it is snapped over the shaft  20  generally perpendicular to the shaft axis while closing the lid  26 , thus engaging with the threads  36 . With the lid  26  closed, the drug reservoir  12  fits tightly into the reservoir compartment  28  to avoid backlash of the piston rod  14  which otherwise could cause an unintended drug delivery or under delivery. Accordingly, as the shaft  20  is rotated unidirectionally, due to its engagement with threads  36 , the nut segment  18  moves linearly along the shaft  20 . 
     In the illustrated embodiment, an unthreaded portion  38  may be provided on the shaft  20  adjacent the shaft support  22 . The nut segment  18  will move linearly as the shaft  20  is rotated until being rotated unto the unthreaded portion  38 . At this point, even though the shaft  20  is rotating, the nut segment  18  ceases to advance the piston rod  14  which provides protection to the drive system  30  and the threads  36  of shaft  20  from a hard stop i.e., cessation of rotation due to the nut segment  18  abutting against the shaft support  22 , which could cause overheating of the drive system  30  and/or damage to threads  36  due to shredding of the nut segment  18  from over rotation. Furthermore, upon situating the nut segment  18  onto the unthreaded portion  38 , the speed and sound of the drive system rotating shaft  20  with change, thus providing an indication that the drug reservoir  12  is empty. 
     It is to be appreciated that the shaft support  22  in the embodiment shown by  FIGS. 1 and 2 , is shaped to fit within the interior surface of the slot of the piston rod  14 . In this manner, as the shaft  20  is rotated unidirectionally, moving the nut segment  18  linearly along shaft  20 , the piston rod  14  will likewise move linearly unobstructed over the shaft support  22 . As best shown by  FIG. 1 , a key portion  40  of the piston rod  14  rides in a guidance track  42  in an extended wall  44  of the drug reservoir  12  to both ensure linear motion and avoid rotational motion of the nut segment  18 . The extended wall  44  also provides the engagement feature  32  on an exterior side thereof. Additional embodiments showing alternative drug reservoir loading and unloading mechanisms for a drug delivery device using a unidirectional rotated shaft according to the present invention is now discussed hereafter. 
     With reference to the embodiment shown by  FIG. 3 , portions of the lid  26  are cut away to show the drug reservoir  12  being held in the lid  26  in the open position and inside the drug reservoir compartment  28 . In addition, portions of the extended wall  44  and the piston rod  14  are sectioned away to show that in this embodiment, the interior surface of the slot of the piston rod  14  provides threads  46 , instead of a nut segment  18  as in the previous embodiment shown by  FIG. 1 . A gear  48  is mounted to at the end of the shaft  20  adjacent the shaft support  22 , and provides threads  50  which mesh with the threads  46  of the piston rod  14 . As also with the embodiment show by  FIG. 1 , the opening and closing of the lid  26  disengages and engages, respectively, the threads  46  of the piston rod  14  with the threads  50  of gear  48 . Accordingly, in the closed position, unidirectional rotation of the shaft  20  with cause similar rotation of gear  48 , and likewise linear movement of the piston rod  14 . As also in the previous embodiment, an unthreaded portion  52  may be provided to the interior surface of the slot of the piston rod  14  to provide protection against a hard stop to the movement of the piston rod  14 . 
     It is to be appreciated that although in the previous embodiments shown by  FIGS. 1-3 , the drug reservoir  12  fits into the lid  26  via directing the front end of the drug reservoir (i.e., the end with exit port  60 ) into the device first, the opposite loading direction is also envisioned. For example, as illustrated by  FIG. 4 , in this embodiment the drug reservoir  12  is fitted into the lid  26  with the piston rod  14  being directed in first when the lid  26  is in the open position. In this embodiment, side wall portions of the base  24  are cut away to show that the drug reservoir  12  is held in the lid  26  in the open position as well as the inside of the drug reservoir compartment  28 . As in the previous embodiment shown by  FIG. 1 , the shaft  20  has threads  36 , and is provided as a lead screw. As also with the embodiment show by  FIG. 1 , the threads  36  of the shaft  20  mesh with threads provided on the piston rod  14  such that unidirectional rotation of shaft  20  causes the piston rod  14  to travel away from the shaft support  22  towards a second shaft support  62 . As the piston rod  14  linearly moves, the plunger  16  is pushed, thereby adjusting the volume of the drug reservoir  12  and dispensing a liquid drug therefrom. 
     It is to be appreciated that the second shaft support  62  in the embodiment shown by  FIG. 4  is shaped to fit within the interior surface of the slot  15  of the piston rod  14 . In this manner, as the shaft  20  is rotated unidirectionally, the piston rod  14  will likewise move linearly unobstructed over the second shaft support  62 . However, unlike the embodiment shown by  FIG. 1 , features such as the key portion  40 , the guidance track  42 , and the extended wall  44  of the drug reservoir  12  are not provided in this embodiment of the drug reservoir  12  to ensure linear motion. Ensuring linear motion is helped in an alternative manner, which is explained hereafter. 
     As shown by  FIG. 5 , in this embodiment the end of the piston rod  14  of the drug reservoir  12  is split into two portions  64  and  66 . In this manner, any misalignment of the threads  56  of the piston rod  14  will cause one of the split portions  64  and  66  to flex. Flexing of the misaligned split portions helps to bring the threads  56  of the piston rod  14  into alignment when being rotated by the shaft  20 , thereby helping to ensure proper linear movement of the piston rod  14 . In this embodiment the opening and closing of the lid  26  disengages and engages, respectively, the threads  56  of the piston rod  14  with the threads  36  of shaft  20 . As also in the previous embodiments, the unthreaded portion  38  may be provided to the shaft  20  adjacent the second shaft support  62  to provide protection against a hard stop. Other opening and closing arrangements and shapes for the drug delivery device is also envisioned, which are discussed hereafter. 
     In the illustrated embodiment of  FIG. 6 , the lid  26  of the drug delivery device  10  is a slidably attached to the base  24 . As shown, the drug reservoir  12  is shaped to drop substantially perpendicular into the reservoir compartment  28 . Sliding the lid  26  over the drug reservoir  12  locks the drug reservoir  12  in the reservoir compartment  28  which protects it from shocks and impacts. By sliding the lid  26  back and forth, the threads of the piston rod  14  will engage/disengage the threads of the shaft (not shown) as in previous embodiments. 
     In the alternative embodiment of  FIG. 7 , the lid  26  opens rotatably, like a clam shell, wherein the guidance track  42  is provided in the lid  26 . The drug reservoir  12  accordingly provides the key portion  40  on the piston rod  14  which is accommodated slidably into the guidance track  42  when the lid  26  is closed. As also shown by this embodiment, the drug reservoir is cylindrical in shape and is loaded straight (i.e., not at an angle) into the reservoir compartment  28 . After opening the lid  26 , the drug reservoir may be removed in a similar manner. As the piston rod  14  engages the shaft  20  of the drug delivery device  10  according to any of the embodiments discussed previously above, for brevity no further discussion regarding this embodiment is provided. 
     Turning now to  FIGS. 8 and 9 , a further alternative embodiment of the present invention is shown, with the drug deliver device  10  illustrated in block diagram for ease of illustration. It is to be appreciated that this alternative embodiment is suitable for use in any of the previously illustrated drug deliver device embodiments. In this embodiment, the drug reservoir  12  is generally cylindrical in shape, and the piston rod  14  thereof is moved by the unidirectionally rotated shaft  20  as in all the previous embodiments to push the plunger  16  and adjust the volume of the drug reservoir  12 . However, unlike the other previous mentioned embodiments in which the piston rod  14  provides a U-shaped channel or slot and is fixed to the plunger  16 , in this embodiment the piston rod  14  is shaped as a hollow cylinder which is rotatably mounted to the plunger  16 , such as for example, via ball joint  68  ( FIG. 9 ). The shaft  20  in this embodiment provides a non-cylindrical shape and size to slid into the hollow interior of the piston which is also provides a similar non-cylindrical shape, and which is best shown by  FIGS. 10 and 11 . In addition, the exterior surface of the piston rod  14  provides threads  70  which are discussed further hereafter. 
     In the illustrated embodiment, the drug delivery device  10  provides a self locking lever mechanism  72  which performs a first function of securing the drug reservoir  12  to the drug delivery device  10 . Another function of the lever mechanism  72 , in addition to locking the drug reservoir  12  in place, is to engage/disengage the threads  70  of the piston rod  14  via a partially threaded nut  74 . As best shown by  FIG. 8 , the partially threaded nut  74  has a cavity  76  with a generally keyhole shape having a pair of connected and different sized arc portions  78  and  80 , where the smaller arc portion  78  carries threads  82  and the larger arc portion  80  is without threads. In addition the partially threaded nut  74  is biased by a spring  84  that is mounted the base  24  of the drug delivery device  10 . As shown, by  FIG. 10 , the spring  84  normally pushes the threads  82  of the partially threaded nut  74  into engagement with the threads  70  of piston rod  14  when situated through the cavity  76 . 
     A button portion  86  of the lever mechanism  72  is provided which when pushed unlocks a locking portion  88  of the lever mechanism  72  from a catch  90  provided in the drug reservoir  12  and disengages the threads  70 ,  82  simultaneously, as shown by  FIG. 11 . In other words, when pushing the button portion  86 , the small arc portion  78  of the partially threaded nut  74  is displaced, such that the larger arc portion  84  is situated around the piston rod  14  unengaged. In this manner the drug reservoir  12  may be replaced by pushing down on the button portion  86 , as indicated by arrow X, and removing the drug reservoir  12  which slides the shaft  20  from its accommodation within the hollow cylinder shape of the piston rod  14 . When the button portion  86  is released, the spring once again pushes the threads  82  of the partially threaded nut  74  into engagement with the threads  70  of the piston rod  14 , and also self locks the catch  90  of the drug reservoir  12  with locking portion  88 . As the shaft  20  is rotated as discussed previously above, via drive system  30 , no further discussion is provided. 
     With reference to  FIG. 12 , an alternative embodiment to the embodiment discussed above with reference to  FIGS. 9 and 10  is shown, where for brevity, only the differences therebetween are discussed hereafter. In this embodiment, the piston rod  14  does not attached to the plunger  16  of the drug reservoir  12 , and thus is not disposable. As before in the embodiment shown by  FIG. 8 , the shaft is non cylindrical in shape and is slidably accommodated within the piston rod  14 . In addition, the threads  70  engage/disengage with the threads  82  of the partially threaded nut  74  via the lever mechanism  72  as also previous mentioned above. However, in this embodiment, the piston rod  14  is axially spring loaded via axial spring  94 . As shown, the axial springs  94  biases the piston rod  14  away from a spring mount  96  as indicated by arrow Y. It is to be appreciated that spring loading the piston rod  14  in this manner ensures physical contact between a disc  98  that is rotatably connected to the piston rod  14  and the plunger  16  of the drug reservoir  12 , such as for example, by ball joint  100 . 
     Accordingly, as the shaft  20  is rotated unidirectional, with threads  70  and  82  engaged, the piston rod  14  will similarly rotate and advance the disc  98  into contact with the plunger  16 , thereby dispensing a liquid drug from the drug reservoir  12  and compressing axial spring  94 . Upon depressing the button portion  86  of the lever mechanism  72 , such as to remove the drug reservoir  12  from the drug delivery device  10 , the piston rod  14  is sprung back via axial spring  94  to a starting position which places the disc  98  closely adjacent the partially threaded nut  74 . As the shaft  20  is rotated as discussed previously above, such as via drive system  30 , no further discussion is provided. 
     Although not limited thereto, the following advantages and features of the various embodiment of the present invention are noted. The present invention does not require a cap to secure and lock the cartridge which provides more user convenience due to the fact that there are fewer parts to assemble. The replacement procedure can be done with few steps and therefore within a shorter time. Due to the fact that there are fewer parts to assemble, malfunctions are less likely to occur. There is no rewind function necessary since the piston rod is either disposable with the drug reservoir or is supported by a spring to ensure tight connection between the plunger and the piston rod. Unintended drug delivery due to siphoning i.e., pulling force of a water column that is higher than the friction force of the plunger which results in a low pressure in the reservoir thereby causing unintended drug delivery in case that the plunger is not secured to the lead screw, is not of concern since in one embodiment the disposable piston rod with threads is permanently attached to the plunger of the reservoir. In the embodiment where the plunger is spring biased and not disposable, since a connection to the plunger is not provided, the water column force will be less than the friction force of the plunger, thereby again helping to prevent any unintended drug delivery due to siphoning. 
     The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The above embodiments disclosed were chosen and described to explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.