Abstract:
A medical solution administration device includes a medical solution storage unit configured to store a medical solution; a channel part having a channel through which the medical solution is flowable from the medical solution storage unit to a living body; a piston; a cylinder part having an internal space; a driving unit configured to slide the piston between a press end position at which a front end of the piston is located at a first end of the internal space of the cylinder part and a pulled-back position at which the front end of the piston is located at a second end of the internal space of the cylinder part; and a seal located at an end of the cylinder part and positioned adjacent to the front end of the piston when the piston is in the pulled-back position, the seal being configured to circumferentially contact the piston.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application filed under 35 U.S.C. 111(a) claiming the benefit under 35 U.S.C. §§120 and 365(c) of PCT International Application No. PCT/JP2013/005609 filed on Sep. 24, 2013, which is based upon and claims the benefit of priority of Japanese Application No. 2012-212603 filed on Sep. 26, 2012, the entire contents of which are hereby incorporated by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a medical solution administration device. For example, the present disclosure is suitable for applying to a case where insulin is administered in a body. 
         [0004]    2. Background Art 
         [0005]    A so-called syringe pump type medical solution administration device has been conventionally proposed (for example, refer to JP 2010-501283 W) as a device for administering medical solution (insulin). The syringe pump type medical solution administration device is a portable device used by being stuck to skin of a user, and it administers the medical solution filled in an external cylinder to a body by pushing out the medical solution via a plunger. 
         [0006]    A medical solution can be supplied into the body by a so-called piston pump type supply unit in the medical solution administration device. In the medical solution administration device using the piston pump type supply unit, a seal such as an O-ring and an X-ring is provided on an outer circumference of a piston sliding in a cylinder. This prevents the medical solution from leaking outside the device from between the cylinder and the piston. 
         [0007]    Here, as illustrated in  FIGS. 1 and 2 , a starting resistance between sliding parts of the piston and the seal increases with time. After the lapse of a predetermined time, the increase in the starting resistance becomes gradual, and the value tends to be a constant value. This is considered because the seal gradually enters a recess on a sliding surface of the piston with time.  FIG. 1  is a diagram of changes of the starting resistances of a plurality of kinds of seals caused by elapse of time.  FIG. 2  is a diagram of an experiment result indicating changes of thrusts (starting resistance) in a case where the piston is started by using the piston having a diameter of 1.03 mm and the X-ring after different leaving times (0, 24, 72, and 96 hours) have elapsed. 
         [0008]    Therefore, in this medical solution administration device, because the starting resistance between the piston and the seal is large, it is necessary to use a large force to start the piston to overcome the starting resistance at the time of starting the use of it. 
         [0009]    On the other hand, it is desired that the portable medical solution administration device be reduced in size because the device is used by being stuck to the skin of the user. 
       SUMMARY OF INVENTION 
       [0010]    Certain embodiments of the present invention have been made in consideration of the above points. Certain embodiments of the present invention propose a medical solution administration device which can be reduced in its overall size. 
         [0011]    According to one embodiment, a medical solution administration device includes a medical solution storage unit configured to store a medical solution; a channel part having a channel through which the medical solution is flowable from the medical solution storage unit to a living body; a piston; a cylinder part having an internal space; a driving unit configured to slide the piston between a press end position at which a front end of the piston is located at a first end of the internal space of the cylinder part and a pulled-back position at which the front end of the piston is located at a second end of the internal space of the cylinder part; and a seal located at an end of the cylinder part and positioned adjacent to the front end of the piston when the piston is in the pulled-back position, the seal being configured to circumferentially contact the piston, and being configured to prevent the medical solution from leaking outside of the cylinder from between the piston and the cylinder part. The first end of the internal space formed by the cylinder part is connected to the channel part. The medical solution administration device is configured such that the piston is locatable in an initial state at an initial position in which the piston is in a position further pulled back than the pulled-back position and in which a contact resistance between the piston and the seal is smaller than in a case where the piston is located at the pulled-back position. 
         [0012]    Accordingly, the contact resistance between the piston and the seal in an initial state is less than in a case where the piston is located at a pulled-back position so that a starting resistance generated between the piston and the seal is less than in a case where the piston is located at the pulled-back position. A force to start the piston to overcome the starting resistance at the time of starting the use of it can be smaller than that of the conventional device 
         [0013]    In one aspect, the medical solution administration further comprises a controller configured to control the driving unit to move the piston from the initial position to the pulled-back position before the medical solution is inserted into the medical solution storage unit from outside. 
         [0014]    In one aspect, a front end part of the piston is formed in a tapered shape, and the front end part formed in the tapered shape contacts a part of the seal in the initial state. 
         [0015]    In one aspect, the piston is formed in a cylindrical shape, and a front end part of the piston contacts a part of the seal in the initial state. 
         [0016]    In one aspect, the driving unit includes a motor, a motor shaft, a bearing, and a coupling, and the motor shaft and the piston are arranged coaxially. 
         [0017]    According to certain embodiments of the present invention, a contact resistance between a piston and a seal in an initial state can be less than in a case where the piston is located at a pulled-back position so that a starting resistance generated between the piston and the seal is less than in a case where the piston is located at the pulled-back position. A force to start the piston to overcome the starting resistance at the time of starting the use of it can be smaller than that of the conventional device. Accordingly, the size of the entire device can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a schematic diagram of a graph indicating a change of a starting resistance caused by an elapse of time. 
           [0019]      FIG. 2  is a schematic diagram of a graph indicating a change of a starting thrust for several different elapsed-times. 
           [0020]      FIG. 3A  is a top perspective schematic diagram of a structure of a medical solution administration device, and  FIG. 3B  is a bottom perspective schematic diagram of the structure of a medical solution administration device. 
           [0021]      FIG. 4  is an exploded perspective view of the medical solution administration device. 
           [0022]      FIG. 5A  is a schematic diagram of a structure of a supply unit where a piston is in a pulled-back position, and  FIG. 5B  is a schematic diagram of the structure of a supply unit where the piston is in a press end position. 
           [0023]      FIG. 6  is a schematic diagram of a position of a piston in an initial state. 
           [0024]      FIG. 7A  is a top view schematic diagram of a structure of a driving unit where the piston is in the pulled-back position, and  FIG. 7B  is a side view schematic diagram of the structure of the driving unit where the piston is in the pulled-back position. 
           [0025]      FIG. 8  is a schematic diagram of a structure of the driving unit where the piston is in the press end position. 
           [0026]      FIG. 9  is a schematic diagram of an electrical structure of the medical solution administration device. 
           [0027]      FIG. 10  is a flowchart of a medical solution administration procedure. 
           [0028]      FIG. 11  is a schematic diagram of a shape and an initial position of a piston according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    One embodiment of the present invention will be described in detail below with reference to the drawings. 
       Entire Structure of Medical Solution Administration Device 
       [0030]    As illustrated in  FIGS. 3A ,  3 B, and  4 , a medical solution administration device  1  is a portable device. A user can hold and use the device by the device being stuck on the skin. The medical solution administration device  1  includes a lower case  2  and an upper case  3  which is fitted into an opening of the lower case  2  and has a flat and substantially rectangular parallelopiped shape. An upper side of the lower case  2  is opened, and the lower case  2  has a space therein. 
         [0031]    It is preferable that the size of the medical solution administration device  1  be reduced to be stuck to the skin of the user. However, for example, the size may be a substantially rectangular parallelopiped shape having a width of 32 mm, a length of 44 mm, and a height of 11 mm. 
         [0032]    A sticking unit  4 , such as a double-sided tape and the like, is provided on a bottom surface  2 A of the lower case  2 . The user holds the medical solution administration device  1  by sticking the sticking unit  4  to the skin of the user. 
         [0033]    In the medical solution administration device  1 , a puncture mechanism  5 , a medical solution storage unit  6 , a channel part  7 , a supply unit  8 , a driving unit  9 , a board  10 , and the like are provided in a space formed by the lower case  2  and the upper case  3 . 
         [0034]    The puncture mechanism  5  projects a puncture needle (not shown) from a puncture needle hole  2 B provided on the bottom surface  2 A of the lower case  2 . The puncture needle (not shown) includes a needle, a cannula, and the like to puncture the skin of the user in order to administer the medical solution (for example, insulin) stored in the medical solution storage unit  6  to the body of the user. 
         [0035]    The medical solution storage unit  6  includes, for example, an external cylinder and a piston. The medical solution is stored in a space formed by the external cylinder and the piston. In the medical solution storage unit  6 , the piston moves in the external cylinder by a force generated when the medical solution is discharged by the supply unit  8 . 
         [0036]    The channel part  7  includes an intake pipe  7 A, a supply pipe  7 B, channels  22 B.  23 A, and  24 A respectively formed in a supply unit  8 , and the puncture needle of the puncture mechanism  5  and forms a channel for flowing the medical solution from the medical solution storage unit  6  to the body. The medical solution storage unit  6  is communicated with the channel  23 A formed in the supply unit  8  by the intake pipe  7 A. The channel  24 A formed in the supply unit  8  is communicated with the puncture needle of the puncture mechanism  5  by the supply pipe  7 B. 
         [0037]    As described in detail below, the supply unit  8  supplies the medical solution stored in the medical solution storage unit  6  to the body via the channel part  7  by sliding the piston  21  in the internal space  22 A of the cylinder part  22  ( FIGS. 5A and 5B ). 
         [0038]    The driving unit  9  drives the piston  21  based on the control by a CPU (controller)  51  ( FIG. 9 ) and slides the piston  21  in the internal space  22 A of the cylinder part  22 . 
         [0039]    A power supply  54  for supplying a power ( FIG. 9 ) and a circuit such as the CPU  51  are arranged on the board  10 . 
       Structure of Supply Unit 
       [0040]    As illustrated in  FIGS. 5A and 5B , the supply unit  8  includes the piston  21 , the cylinder part  22 , lids  23  and  24 , one-way valves  25  and  26 , a seal  27 , a seal fixing part  28 , and a fixing member  29 . In  FIG. 5A , the piston  21  is located at a position where the piston is pulled back to the end at the time of the reciprocation (referred to as “pulled-back position” below). In  FIG. 5B , the piston  21  is located at a position where the piston is pressed to the deepest part at the time of the reciprocation (referred to as “press end position” below). 
         [0041]    A body  21 B of the piston  21  other than a front end part  21 A is shaped like a cylinder having a diameter of 1.03 mm, for example. The front end part  21 A is formed in a truncated cone shape, and the diameter of the front end part  21 A decreases as it approaches the front end. 
         [0042]    The piston  21  slides with a predetermined stroke by being driven by the driving unit  9  in the hollow internal space  22 A shaped like a cylinder formed in the cylinder part  22 . For example, stainless steel, copper alloy, aluminum alloy, a titanium material, and a thermoplastic elastomer such as polypropylene and polycarbonate can be considered as a material of the piston  21 . 
         [0043]    The internal space  22 A where the piston  21  is inserted from one end and slides is provided in the cylinder part  22 . Also, the cylinder part  22  is provided so that the channel  22 B which contacts with another end of the internal space  22 A and is orthogonal to the internal space  22 A penetrates between side surfaces of the cylinder part  22  opposed to each other. 
         [0044]    In the cylinder part  22 , the seal  27  for preventing leakage of the medical solution between the piston  21  and the cylinder part  22  and a seal fixing part  28  for fixing the seal  27  are provided on one end of the internal space  22 A where the piston  21  is inserted. For example, an X-ring and O-ring are exemplified as the seal  27  for preventing the leakage of the medical solution, and the X-ring is applied to the present embodiment. 
         [0045]    The seal  27  is inserted into the cylinder part  22  from the side of the surface where the internal space  22 A is provided in the cylinder part  22  and is pressed and fixed by the seal fixing part  28 . A part of the seal fixing part  28  is fitted into the cylinder part  22  and the other part is exposed to outside so that the seal  27  is fixed. 
         [0046]    In the cylinder part  22 , the lids  23  and  24  are connected to the side surface where the channel  22 B is formed via the fixing members  29 . In the lids  23  and  24 , the channels  23 A and  24 A for penetrating along the channel  22 B are provided at positions respectively opposite to the channel  22 B of the cylinder part  22 . 
         [0047]    In the lid  23 , one end of the channel  23 A is connected to the channel  22 B of the cylinder part  22 , and the other end of the channel  23 A is connected to the intake pipe  7 A. This allows the intake pipe  7 A and the channel  22 B to be communicated with each other. 
         [0048]    In the lid  24 , one end of the channel  24 A is connected to the channel  22 B of the cylinder part  22 , and the other end of the channel  24 A is connected to the supply pipe  7 B. This allows the channel  22 B and the supply pipe  7 B to be communicated with each other. 
         [0049]    In the supply unit  8 , the one-way valve  25  is provided between the channel  23 A of the lid  23  and the channel  22 B of the cylinder part  22 . The one-way valve  26  is provided between the channel  22 B of the cylinder part  22  and the channel  24 A of the lid  24 . 
         [0050]    The medical solution flows from the channel  23 A of the lid  23  to the channel  22 B of the cylinder part  22  through the one-way valve  25 , and the medical solution does not flow from the channel  22 B of the cylinder part  22  to the channel  23 A of the lid  23  through the one-way valve  25 . For example, an umbrella valve is applied as the one-way valve  25 . 
         [0051]    The medical solution flows from the channel  22 B of the cylinder part  22  to the channel  24 A of the lid  24  through the one-way valve  26 , and the medical solution does not flow from the channel  24 A of the lid  24  to the channel  22 B of the cylinder part  22  through the one-way valve  26 . For example, the umbrella valve is applied as the one-way valve  26 . 
         [0052]    When the supply unit  8  supplies the medical solution from the medical solution storage unit  6  into the living body, the piston  21  is moved by the driving unit  9  from the press end position to the pulled-back position in the internal space  22 A. Then, the supply unit  8  sucks the medical solution stored in the medical solution storage unit  6  into the internal space  22 A. 
         [0053]    The piston  21  is moved by the driving unit  9  from the pulled-back position to the press end position, and accordingly, the supply unit  8  supplies the medical solution sucked to the internal space  22 A into the living body. 
         [0054]    The supply unit  8  can administer the medical solution in an amount of about 1 to 2 μL to the body of the user by one reciprocal movement of the piston  21 . The supply unit  8  can administer the medical solution of a desired dose to the user at a desired administration rate by repeating this movement in a set period and interval. 
         [0055]    As illustrated in  FIG. 6 , in an initial state (shipping state) of the supply unit  8 , the piston  21  is arranged at a position where it is further pulled back from the pulled-back position and where a part of the front end part  21 A formed in a truncated cone shape contacts with the seal  27  along the circumferential direction (also referred to as “initial position” below). 
         [0056]    Therefore, because the tapered front end part  21 A of the piston  21  contacts with the seal  27  in the supply unit  8 , the amount of the squeeze of the seal  27  can be smaller than that in a case where the body  21 B of the piston  21  contacts with the seal  27 . Accordingly, a contact resistance between the piston  21  and the seal  27  can be reduced in the supply unit  8 . 
         [0057]    When the medical solution administration device  1  is started, the piston  21  is moved to the pulled-back position in the supply unit  8  by the driving unit  9 . 
       Structure of Driving Unit 
       [0058]    As illustrated in  FIGS. 7A and 7B , the driving unit  9  includes a base part  31 , a motor  32 , a motor supporting part  34 , a motor fixing plate  35 , a fixing plate supporting part  36 , a bearing  37 , a coupling  38 , and a bearing supporting part  39 . 
         [0059]    Each part of the driving unit  9  is arranged on the base part  31 . The motor  32  is held by the motor supporting part  34  and the motor fixing plate  35  supported by the fixing plate supporting part  36  and is fixed to the base part  31 . 
         [0060]    In the motor  32 , the motor shaft  33  exposed from the side surface on the side of the motor fixing plate  35  is provided. A screw groove  33 A is formed on the side surface of the motor shaft  33 . 
         [0061]    The bearing  37  is formed in a substantially rectangular parallelopiped shape that is elongated along the axis direction of the motor  32  and is formed to be hollow. In the bearing  37 , a screw hole  37 A, in which the motor shaft  33  of the motor  32  is arranged to be penetrated and screwed to the screw groove  33 A, is provided at the center of the side surface corresponding to a short side of the substantially rectangular parallelopiped shape. 
         [0062]    In the bearing  37 , the piston  21  is connected to a side surface opposed to the side surface on which the screw hole  37 A is provided corresponding to the short side of the substantially rectangular parallelopiped shape via the coupling  38 . The piston  21  and the motor shaft  33  are coaxially arranged. The bearing  37  is supported by the bearing supporting part  39 . For example, a thing for adjusting a gap between the motor shaft  33  and the piston  21  in the axis direction is applied as the coupling  38 . 
         [0063]    As illustrated in  FIGS. 7A ,  7 B and  8 , in the driving unit  9 , the motor shaft  33  is rotated by driving the motor  32 , and the bearing  37  screwed to the motor shaft  33  is moved in the axis direction according to the rotation. Accordingly, this reciprocates the piston  21  in the axis direction. According to this, the driving unit  9  slides the piston  21  in the internal space  22 A of the cylinder part  22 . The piston  21  is located at the pulled-back position in  FIGS. 7A and 7B , and the piston  21  is located at the press end position in  FIG. 8 . 
         [0064]    In this way, in the driving unit  9 , because the motor shaft  33  of the motor  32  and the piston  21  are coaxially arranged, a force which is added to the bearing  37  by rotating the motor shaft  33  directs to the same direction as a force which is added to the piston  21  by the force added to the bearing  37 . Accordingly, a loss of the thrust of the piston  21  is eliminated. 
         [0065]    Therefore, the driving unit  9  can slide the piston  21  with a stable stroke distance in the internal space  22 A of the cylinder part  22 . The driving unit  9  can drive the piston  21  with smaller force by eliminating the loss of the thrust of the piston  21 . Therefore, the motor  32 , a battery, and the like can be reduced in size, and the entire device can be reduced in size. The side surfaces of the piston  21  may be coated with diamond-like carbon to reduce a sliding resistance. 
         [0066]    On the other hand, in a device in which a piston and a shaft of a motor are not coaxially arranged, a force which is added to a bearing by rotating the shaft offsets a force which is added to the piston by the force added to the bearing so that the loss of the thrust of the piston increases. At the same time, the sliding resistances of the bearing and the piston increases due to the offset of the forces. Therefore, not only is the stroke of the piston not stable, and the entire device becomes large. 
         [0067]    In the medical solution administration device  1 , a space between the seal fixing part  28  and the coupling  38  is covered with a tubular film  40  having flexibility. For example, polyethylene can be applied as a material of the film  40 . 
         [0068]    Both ends of the film  40  are fixed by film fixing parts  41  and  42  with no gap relative to the seal fixing part  28  and the coupling  38  in a circumferential direction. For example, the film fixing parts  41  and  42  are formed by the O-rings. 
         [0069]    Because the film  40  has the flexibility, a state where the piston  21  is covered can be continuously maintained over a period from a state where the piston  21  is located at the pulled-back position to a state where the piston  21  is located at the press end position. 
         [0070]    Therefore, in the medical solution administration device  1 , the piston  21  can slide in the internal space  22 A of the cylinder part  22  without contacting with the air outside the film  40 . According to this, the medical solution administration device  1  can keep the piston  21  clean. 
       Electrical Structure of Medical Solution Administration Device 
       [0071]    As illustrated in  FIG. 9 , the medical solution administration device  1  is connected to the central processing unit (CPU)  51 , a read only memory (ROM)  52 , a random access memory (RAM)  53 , a power supply  54 , an interface part (I/F part)  55 , an informing part  56 , and the driving unit  9  via a bus  57 . 
         [0072]    The CPU  51 , the ROM  52 , the RAM  53 , the power supply  54 , and the informing part  56  are arranged on the board  10 . An electric battery is applied as the power supply  54 . For example, a button (not shown) which is arranged in the upper case  3  or the lower case  2  and receives an input instruction of the user is applied as the interface part  55 . A speaker is applied as the informing part  56 . 
         [0073]    The CPU  51  generally controls the entire device by reading a basic program stored in the ROM  52  to the RAM  53  and executing it. At the same time, the CPU  51  performs various processing by reading various application programs stored in the ROM  52  to the RAM  53  and executing them. 
         [0074]    When administering the medical solution to the user, the medical solution administration device  1  performs medical solution administration processing according to the flowchart illustrated in  FIG. 10 . 
         [0075]    The CPU  51  starts each part in step SP 1  when receiving a start signal from a controller (not shown) which sends various instructions to the medical solution administration device  1 . In step SP 2 , the CPU  51  drives the driving unit  9  and moves the piston  21  from the initial position to the pulled-back position. 
         [0076]    The user injects the medical solution into the medical solution storage unit  6  in step SP 3 . In step SP 4 , after the medical solution administration device  1  has been stuck to the skin of the user via the sticking unit  4 , the puncture needle punctures the user by the puncture mechanism  5 . 
         [0077]    When receiving an administration parameter such as a dose and an administration rate transmitted from the controller, the CPU  51  sets the parameter in step SP 5  so as to drive the driving unit  9  according to the administration parameter. 
         [0078]    The CPU  51  starts to administer the medical solution by driving the driving unit  9  in step SP 6 . When determining that all the medical solutions have been administered, the CPU  51  ends the administration of the medical solution in step SP 7 . 
         [0079]    On the other hand, when determining in step SP 7  that not all the medical solutions have been administered, the CPU  51  determines in step SP 8  whether the medical solution of the set dose has been administered. Then, when CPU  51  determines that the medical solution of the set dose has not been administered, the administration of the medical solution is continued in step SP 9 . 
         [0080]    When the CPU  51  has determined in step SP 8  that the medical solution of the set dose has been administered, the CPU  51  waits for an input of an instruction from the controller in step SP 10 . When the instruction is received, steps SP 5  to SP 10  are sequentially performed. 
       Effect and the Like 
       [0081]    With the above structure, in an initial state (shipping state) of the medical solution administration device  1 , the piston  21  is arranged at a position where it is further pulled back from the pulled-back position and where a part of the front end part  21 A formed in a truncated cone shape contacts with the seal  27  along the circumferential direction (initial position). Then, the piston  21  is located in the pulled-back position before the medical solution is injected into the medical solution storage unit  6 . 
         [0082]    Accordingly, in the medical solution administration device  1 , when the piston  21  is located at the initial position, the amount of the squeeze of the seal  27  is reduced. Therefore, the contact resistance can be smaller than in a case where the seal  27  contacts with the body  21 B of the piston  21 . 
         [0083]    Therefore, the medical solution administration device  1  can reduce the contact resistance (starting resistance) between the piston  21  and the seal  27 . Even when the starting resistance between the piston  21  and the seal  27  becomes large as time elapses, the value can be considerably reduced compared with the conventional value. 
         [0084]    In this way, it is not necessary for the medical solution administration device  1  to use a large force to start the piston to overcome the starting resistance at the time of starting the use of it, and the size of the entire device can be reduced. 
         [0085]    Also, in the medical solution administration device  1 , because the piston  21  is formed in a truncated cone shape, the piston  21  can be surely activated when it moves from the initial position to the pulled-back position. 
       Another Embodiment 
       [0086]    In the above-mentioned embodiment, a case has been described where the front end part  21 A of the piston  21  is formed in a truncated cone shape. However, the present invention is not limited to this, and the front end of the piston may be formed in a cylindrical shape similarly to the body. 
         [0087]    For example, as illustrated in  FIG. 11 , a front end part  121 A and a body  121 B of a piston  121  are respectively formed in cylindrical shapes with the same diameter. In the initial state, the piston  121  is arranged at a position where it is further pulled back from the pulled-back position and at an initial position where it contacts with a part of the seal  27  along the sliding direction. According to this, in the initial state, a contact resistance (starting resistance) between the piston  121  and the seal  27  can be reduced.