Abstract:
An automatic administration instrument includes a syringe and a partition wall in the syringe which partitions the syringe into different rooms for respectively holding plural kinds of drug solutions or a drug and a drug solution. A partition-wall driver displaces the partition wall and an injection needle is connected to the syringe. A body cap attached to the administration instrument body so as to cover the injection needle. The syringe, the partition wall, and the body cap are configured such that displacing the partition wall dissolves or mixes the drug solutions or the drug and the drug solution in a state that the injection needle is covered by the body cap.

Description:
TECHNICAL FIELD 
     The present invention relates to an automatic administration instrument for medical use, which is used for administering drug solutions. 
     BACKGROUND ART 
     Conventionally, an administration instrument for medical use is often used when a drug solution such as growth hormone, insulin, or the like is administered. Generally, when using the administration instrument, a doctor or a nurse performs administration in a hospital or the like, and a patient or his family performs administration at home. The administration is carried out by inserting a needle into some region on the skin, and the angle of the needle insertion into the skin and the speed of the needle insertion as well as the speed at which the drug solution is injected after the needle insertion depend on the skill level of a person who performs the administration. 
       FIG. 5  is a block diagram illustrating the inside of an electric injector which is currently used in dentistry. The principle of administration of drug solutions will be described with reference to  FIG. 5 . Now, a syringe  103  filled with a drug solution is set in a cartridge holder  102  attached to a main body  110 . 
     When pressing a SW 1 , a motor  111  normally rotates, and the torque is reduced by a reduction gear box  109  which is directly connected to the motor  111  to rotate a reduction gear main-shaft  108  of the reduction gear box  109 . An end of the reduction gear main-shaft  108  engages with a gear  106  through a rotary disc  107  to rotate the gear  106 . Further, the gear  106  engages with a gear  105  and thereby the torque of the gear  106  propagates to the gear  105 . A gear  105   a  is provided coaxially with the gear  105  so as to engage with a rack  104   a  which is provided in the lower right half of a push piston  104  from the center thereof. When the gear  105  rotates, the gear  105   a  also rotates in the same direction as the gear  105 , and consequently, the push piston  104  is moved in the direction of the injection needle  113 , whereby the drug solution in the syringe  103  is pushed out of the injection needle  113 . 
     During injecting, air is removed in the above-described operation, and thereafter, the injection needle  113  is inserted into a target region, and the drug solution is administered. In  FIG. 5 , SW 2  denotes a switch for reverse rotation of the motor  111 , and  112  denotes a battery for driving the motor  111 . 
     Up to this point the conventional electric injector for automatically administering a drug solution has been described. 
     Next, a typical administration instrument for medical use in which a drug and a drug solution are dissolved and mixed, which has conventionally been employed, will be described with reference to  FIG. 6 . In the administration instrument for medical use shown in  FIG. 6 , when it is used, a drug and a drug solution are mixed and dissolved by manual operation and then injected. In  FIG. 6 , constituents that are substantially identical to those shown in  FIG. 5  are given the same reference numerals. 
     Now, a syringe  103  is set in a cartridge holder  117 , and the syringe  103  contains a powder preparation  114  and a drug solution  127  which are placed in different rooms separated by a rubber  116  and a rubber  118 . An injection needle  113  attached to an end of the syringe  103  is provided with a needle cap  101 . In this state, the injection needle  113  is directed upward and an injection button  120  is pushed toward the injection needle  113 . Then, the push piston  119  pushes the rubber  118 , the rubber then pushes the drug solution  127 , and the rubber  116  moves toward the injection needle  113  with the pressure at which the drug solution  127  is pushed. When the rubber  116  reaches a position slightly ahead of a protrusion  115  of the syringe, the drug solution  127  goes over the rubber  116 , passes the syringe protrusion  115 , and starts to flow into the room of the powder preparation  114 . The injection button  120  is further pushed, and then the drug solution  127  continuously flows into the room of the powder preparation  114 . After all the drug solution  127  flows into the room of the powder preparation  114 , the rubber  118  contacts the rubber  116 . 
     Next, for fully mixing and dissolving them, the injection needle  113  is directed upward in the above-mentioned state and is slightly shaken. Next, with the injection noodle  113  being directed upward, the needle cap  101  is removed and the injection button  120  is pressed, thereby releasing air. After the air releasing, the injection needle  113  is inserted into a region of the body at which the drug solution is to be administered, and the injection button  120  is pressed, whereby the drug solution is administered into the region. As described above, in the administration instrument shown in  FIG. 16 , the processes from the mixing and dissolving of the drug and drug solution to the administration thereof are manually performed. 
     However, in the conventional administration instrument for medical use, no matter how much a person is skilled in achieving the angle to the skin and the speed during needle insertion as well as the speed of injecting the drug solution and the speed of removing the needle after the needle insertion, the person who does the administration is merely a human being, and therefore, the above-mentioned angle and speeds cannot be prevented from being varied depending on the physical condition and the like at that time. Since a person who administers the drug solution and a person who is given the drug solution are both human beings, the body sizes are different and the physical conditions at the administration are not always the same. Therefore, it is difficult to administer the drug solution in the same manner every time. Therefore, it is not always possible to perform administration with reduced pain. 
     Particularly, since the electric injector shown in  FIG. 5  is a grip type injector, the user must grip and support its body by one hand as well as keep on pressing the SW 1  throughout administration. Further, since the injector is large in shape and a battery  112  is heavy in weight, a great physical strain is imposed on the person who performs administration and, therefore, it is difficult to perform self-administration using this injector. 
     Further, in the mixing and dissolving type administration instrument shown in  FIG. 6 , since the dissolving operation is manually performed, it is necessary to watch the dissolving condition with great care as well as perform the dissolving with discretion. Further, proper mixing cannot be performed unless the injection needle is shaken in a vertical orientation even after the dissolving. This is a very troublesome work for a patient having bad eyesight. 
     Further, a patient may have a fear about seeing the injection needle until just before administration, and this may cause a mental strain to the patient. 
     As described above, the needle insertion itself imposes physical and mental strains on the patient and, in some cases, seriously affects the body of the patient, which might lead to life-threatening danger. 
     The present invention is made to solve the above-described problems and has an object of providing an administration instrument for medical use which automatically performs needle insertion, administration, and needle removal, and further, automatically performs dissolving, mixing, and air-releasing when it is a dissolving and mixing type administration instrument, and still further, has a construction in which an injection needle is kept unseen from the outside until just before needle insertion, thereby reducing physical and mental strains on patients and realizing administration under more stable conditions. 
     DISCLOSURE OF THE INVENTION 
     An automatic administration instrument for medical use according to the present invention is provided with means for automatically inserting an injection needle into a skin, and means for automatically removing the injection needle from the skin, and injection is carried out under the state where a part of the body of the administration instrument is pressed against a body region of a patient to be subjected to administration. Therefore, an angle, a depth, and a speed at which needle insertion or needle removal is carried out can be controlled, thereby reducing a possibility that administration is influenced by variations in the level of skill, daily physical condition, or body size among individuals. 
     Further, in the automatic administration instrument for medical use according to the present invention, the speed at which the injection needle is automatically inserted into the skin or the speed at which the injection needle is automatically removed from the skin is made variable, and the amount of drug solution to be injected per unit time during administration can be arbitrarily set, and further, the injection needle is not visible from the outside until needle insertion is completed. Therefore, the pain of the patient to which the drug solution is administered is reduced during needle insertion, administration, and needle removal, and the fear of the patient is also reduced, whereby administration can be carried out in a stable manner, resulting in reductions in physical and mental burdens. 
     Further, when the automatic administration instrument for medical use according to the present invention is an administration instrument that employs plural drug solutions to be mixed, or a drug and a drug solution to be dissolved and mixed, the mixing or dissolving is automatically carried out, and further, a syringe is automatically shaken in the administration instrument body after the mixing or dissolving is completed. Therefore, the patient is relieved of the inconvenience of the mixing or dissolving operation, and further, the drug solutions can be mixed with higher reliability, whereby the drug solution itself can be used in the optimum state. Further, since air-releasing or the like is also automatically carried out, it becomes unnecessary to check air-releasing, thereby reducing the inconvenience of the air-releasing operation. 
     Furthermore, in the automatic administration instrument for medical use according to the present invention, when the patient forgets about attaching the injection needle when performing dissolving or administration, the operation of pushing out the drug solution is stopped, thereby preventing the risk of cracking of the syringe, inverse leakage of the drug solution, or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an automatic administration instrument for medical use according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the automatic administration instrument for medical use. 
         FIG. 3  is a cross-sectional view of an automatic administration instrument for medical use according to another embodiment of the present invention. 
         FIG. 4  is a block diagram illustrating the automatic administration instrument for medical use according the embodiment of the present invention. 
         FIG. 5  is a block diagram illustrating an internal construction of the conventional electric injector. 
         FIG. 6  is a cross-sectional view of a dissolving and mixing type automatic administration instrument for medical use according to conventional example. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described with reference to  FIGS. 1 to 4 . 
       FIG. 1  is a perspective view illustrating an external view of an automatic administration instrument for medical use according to an embodiment of the present invention,  FIG. 2  is a cross-sectional view for explaining the internal structure of the automatic administration instrument for medical use,  FIG. 3  is a cross-sectional view for explaining the internal structure of an automatic administration instrument for medical use according to another embodiment of the present invention, and  FIG. 4  is a block diagram for explaining the embodiment of the present invention. 
     First of all, the construction and operation of an automatic administration instrument for medical use which is capable of automatic needle insertion and automatic needle removal will be described with reference to  FIG. 1 ,  FIG. 2 , and  FIG. 4 . 
     In  FIG. 1 , reference numeral  18  denotes a body of the automatic administration instrument for medical use, numeral  17  denotes a switch for making the administration instrument perform insertion and removal of an injection needle, numeral  21  denotes a body cap that covers the injection needle, and numeral  20  denotes a skin touch switch for detecting that the administration instrument body  18  is pressed against a body region where administration is to be carried out. 
     In  FIG. 2 , an inner case  10  to which a syringe  8  filled with a drug solution  5  is attached is set in the body  18 . An injection needle  1  is set at an end of the inner case  10 . Further, the injection needle  1  is housed in a body cap  21  and is invisible from the outside. In  FIG. 2 , however, the injection needle is visible because  FIG. 2  shows the position of the needle during needle insertion. Further, a battery  2  and a liquid crystal display  3  are also housed in the body cap  21 . 
     Now, the user holds the body  18  by hand, presses the skin touch switch  20  against a target region on his/her body, and presses the switch  17 . Then, an axis of a motor  16  starts to rotate, and thereby a movable screw that is directly connected to the axis of the motor  16  rotates. A screw thread is formed on the surface of the movable screw  15  so as to engage with a thread formed inside the inner cap  14 . The inner cap  14  is engaged with a part of the inner case  10  by screws, and is freely movable by a predetermined stroke in the longitudinal direction of the body  18 , in the body  18  united with the inner case  10 . 
     That is, in this construction, as the axis of the motor  16  rotates, the movable screw  15  rotates. The rotation is converted into a thrust that moves the inner case  10  toward the tip of the injection needle  1  in the body  18  by the inner cap  14 , and consequently, the injection needle  1  is protruded from the body cap  21  toward the skin and inserted into the skin. 
     When administration of the drug solution is ended, the motor  16  rotates backward, and the injection needle  1  is housed into the body  18 . That is, the needle  1  is removed from the skin. 
     It has been known that the higher the speed of inserting and removing the injection needle is, the lesser the patient feels pain. While in this embodiment these operations are carried out at an instant of 0.05 sec or below during actual administration, the operation speed is variable and settable by a setting switch  26 . Further, a series of operations and settings described above are carried out by sending signals to a microprocessor  100  shown in  FIG. 4  to be judged and instructed by the microprocessor  100 . 
     Since, for safety, the circuit is constructed so that the actual needle insertion is not carried out unless the skin touch switch  20  is pressed, the needle insertion cannot be carried out unless the skin touch switch  20  is pressed against the target skin region. Further, the needle removal is carried out by rotating the motor  16  backward after the microprocessor  100  judges that the administration is completed. Also the needle removal is carried out at an instant of 0.05 sec or below, like the needle insertion. 
     In the above-mentioned construction, the operation of injecting the drug solution is carried out as follows. 
     With reference to  FIG. 2 , the user holds the body  18  by hand, presses the skin touch switch  20  against a target region where administration is to be carried out, and pushes the switch  17 . Then, the injection needle  1  is inserted into the skin. When about 0.5 sec has passed after the needle insertion, the motor  13  starts to rotate, and the rotation propagates to the shaft screw  12 . The inside of a drug solution push piston  9  is engaged with a screw thread formed at the surface of a shaft screw  12 , whereby the piston  9  is movable forward and backward in the syringe  8  when the shaft screw  12  rotates. Therefore, when the shaft screw  12  rotates, the drug solution push piston  9  is pushed forward. When the drug solution push piston  9  moves forward, it presses the rubber  24  and the rubber  7 , and further, the drug solution  5  is pushed out of the tip of the injection needle  1  to be administered into the skin. 
     However, when the skin touch switch  20  is not pressed, that is, when the body  18  is not pressed against the skin, no needle insertion nor injection of drug solution are carried out even if the switch  17  is pressed, as already described above. Once the switch  17  is pressed, it continues to operate. 
     The time until the motor  13  starts to operate after needle insertion, and the duration of drug injection by the motor  13 , i.e., the amount of drug solution to be injected, are previously incorporated in the microprocessor  100  shown in  FIG. 4 , and these operations are carried out according to instructions from the microprocessor  100 . 
     Further, replacement of the syringe  8  is carried out as follows. 
     After administration, the injection needle  1  is surely housed in the body  18 . When the reset switch  122  is pressed in this state, the motor  13  and the shaft screw  12  rotate so as to pull the drug solution push piston  9  back into the body. Then, the body cap  21  is removed in the state where the drug solution push piston  9  is housed in the body, the needle cap  101  (similar to that shown in  FIG. 6 ) is attached to the injection needle  1 , and the injection needle  1  is twisted to be removed. Next, the syringe cap  4  is removed, and the syringe  8  is removed so as to be replaced with a new one. After syringe replacement, the syringe cap  4  is set, and the injection needle  1  covered with the needle cap  101  is set. Thereafter, the needle cap  101  is removed, and the body cap  21  is attached to the body  18 , whereby the administration instrument goes into the stand-by for administration. 
     Next, a description will be given of automatic dissolving, automatic mixing (shaking), automatic air-releasing, and automatic administration, with reference to  FIGS. 3 and 4 . 
     The inside of the syringe  8  is partitioned by the rubber  7  and the rubber  24  into two rooms, and the respective rooms are filled with the drug solution  22  and the powder preparation  23 . Further, the injection needle  1  is previously attached to the tip of the syringe  8 . 
     When the user holds the body  18  by hand and presses the dissolving switch  121  with the injection needle  1  turning upward, the motor  13  rotates, and the shaft screw  12  directly connected to the axis of the motor  13  rotates. A screw thread is formed on the surface of the shaft screw  12  so as to engage with a thread formed inside the drug solution push piston  9 , and the tip of the drug solution push piston  9  is fixed to the rubber  24  with a screw. 
     Accordingly, when the shaft screw  12  rotates, the rubber  24  united with the drug solution push piston  9  starts to move toward the tip of the injection needle. That is, when the axis of the motor  13  rotates, the shaft screw  12  rotates, and the rotation is converted into a thrust that moves the rubber  24  in the syringe  8  toward the injection needle  1  by the drug solution push piston  9 . 
     Next, when the rubber  24  is pushed, the drug solution  22  is compressed and pushes the rubber  7  forward. When the rubber  7  reaches a position slightly ahead of a protrusion  25  of the syringe, the drug solution  22  passes through the space that is formed by the protrusion  25  of the syringe and, further, goes over the rubber  7  and flows into the room where the powder preparation  23  exists. At this time, the rubber  7  does not move even when the rubber  24  is pressed toward the injection needle  1  until all of the drug solution  22  flows into the room of the powder preparation  23 . 
     After the rubber  24  is pressed toward the injection needle  1  and all of the drug solution  22  flows into the room of the powder preparation  23 , the rubber  24  contacts the rubber  7 . On the other hand, the drug solution  22  that has flowed into the room of the powder preparation  23  starts to gradually dissolve the powder preparation  23 . The microprocessor  100  shown in  FIG. 4  monitors the time from when the motor  13  starts to rotate to when all of the drug solution  22  flows into the room of the powder preparation  23 . Up to this point the automatic dissolving has been described. 
     As described above, since the microprocessor  100  shown in  FIG. 4  monitors the time required for a series of operations up to the automatic dissolving, it instructs automatic mixing (shaking) after the automatic dissolving is completed. 
     Hereinafter, this operation will be described. 
     The body  18  is positioned so that the injection needle  1  turns upward. In  FIG. 4 , when the microprocessor  100  judges that the automatic dissolving is completed, the microprocessor  100  outputs an instruction to rotate the motor  16 . When the motor  16  rotates, the movable screw  15  directly connected to the axis of the motor  16  rotates. 
     A screw thread is formed on the surface of the movable screw  15  so as to engage with a thread formed inside the inner cap  14 . The inner cap  14  is fixed to a part of the inner case  10  with a screw, and is freely movable in combination with the inner case  10 , by a predetermined stroke in the direction parallel to the longitudinal direction of the body  18 , in the body  18 . That is, when the axis of the motor  16  rotates, the movable screw  15  rotates, and the rotation is converted into a thrust that moves the inner case  10  forward in the body  18  by the inner cap  14 . 
     A plate-shaped protrusion  19  is formed on a part of the inner case  10 . Further, a photocoupler  11  is formed on the inside of the body  18 . As the inner case  10  moves toward the injection needle  1  with rotation of the motor  16 , the plate-shaped protrusion  19  also moves in the same direction. When the plate-shaped protrusion  19  reaches the position of the photocoupler  11 , the microprocessor  100  outputs an instruction to rotate the motor  16  in the direction inverse to the previous rotation, according to a detection signal of the photocoupler  11 . Then, the inner case  10  moves up to the initial position. When the inner case  10  reaches the initial position, the microprocessor  100  again outputs an instruction to normally rotate the motor  16  as before. Then, the inner case  10  starts to move toward the injection needle  1 . 
     By repeating the above-mentioned operation several times, the inner case  10  is shaken. Consequently, the syringe  8  attached to the inner case  10  is shaken, whereby the dissolved drug solution in the syringe  8  is shaken. 
     The shaking time of the syringe  8  and the number of times the syringe  8  is shaken (for example, 10 sec or below, and five to twenty times) have previously been incorporated as a program in the microprocessor  100  so that an optimum state can be obtained according to the drug solution to be handled. The stroke during the shaking is made so that the injection needle  1  never goes out of the body cap  21  attached to the body  18 . 
     Next, automatic air-releasing and automatic administration will be described. 
     Initially, automatic air-releasing is incorporated as a program in the microprocessor  100  so as to be carried out subsequently to the automatic shaking. 
     During the air-releasing, the body is positioned with the injection needle  1  turning upward, as in the dissolving and shaking. The air-releasing is carried out with the injection needle  1  protruding from the body cap  21 . 
     After the shaking, the microprocessor  100  outputs an instruction to normally rotate the motor  16 . Then, as described above, the movable screw  15  rotates, and the inner cap  14  moves the inner case  10  toward the injection needle  1 , and consequently, pushes the injection needle  1  out of the body cap  21 . During the air-releasing, even if the plate-shaped protrusion  19  formed at a part of the inner case  10  passes the photocoupler  11  formed on the inside of the body  18 , the microprocessor  100  does not accept a signal at this time. 
     At a point in time when the injection needle  1  goes out of the body cap  21 , the microprocessor  100  stops rotation of the motor  16 , and then outputs an instruction to normally rotate the motor  13 . As already described for the automatic dissolving, when the motor  13  normally rotates, the rotation makes the shaft screw  12  rotate, and makes the drug solution push piston  9  move toward the injection needle  1 . 
     Since the operation up to the shaking has been ended, the rubber  7  and the rubber  24  contacting each other moves toward the injection needle  1 , pushes out the drug solution in the syringe  8 , and further, pushes out the air in the syringe  8 . Since the amount of air to be pushed out at this time depends on the amount of operation of the drug solution push piston  9 , i.e., the rpm of the motor  13 , the rpm of the motor  13  is previously incorporated in the microprocessor  100  as a program. 
     Next, automatic administration will be described. The user holds the body  18  by hand, and presses the skin touch switch  20  against a target region, and presses the switch  17 . Then, automatic needle insertion is carried out. Since the detail has already been described, repeated description is not necessary. 
     After the automatic needle insertion, the microprocessor  100  outputs an instruction to normally rotate the motor  13 . Then, the shaft screw  12  rotates, and the drug solution push piston  9  pushes the rubber  24  and the rubber  7 , and further, pushes the drug solution. The drug solution is administered to the skin through the inside of the injection needle  1 . The speed of administering the drug solution at this time can be variably set by the setting switch  26 . Further, since the motor  13  is controlled at a constant speed by the microprocessor  100 , it is possible to make the amount of drug solution to be injected per unit time constant. 
     When the skin touch switch is removed from the skin during the administration, the microprocessor  100  outputs an instruction to stop the rotation of the motor  13 , whereby the drug solution push piston  9  stops, and consequently, injection of the drug solution from the needle  1  stops. Further, the injection needle  1  goes into the automatic needle removal state after a few seconds from when rotation of the motor  13  stops, and then it is housed in the body  18 . At this time, the reason why the injection needle  1  is left for a few seconds is because the drug solution may leak from the tip of the injection needle  1  due to pressure that has been applied to the drug solution push piston  9  even if the piston  9  is suddenly stopped during the administration. The time has previously been stored in the microprocessor. 
     After the administration is completed, the microprocessor  100  outputs an instruction to perform the operation of automatic needle removal. An appropriate time from the completion of administration to the automatic needle removal should be about 6 sec, considering existing data that the time from when injection of the drug solution is stopped to when leakage of the drug solution from the tip of the needle is completely stopped is about 5 sec. 
     A series of operations from the automatic needle insertion and the automatic administration to the automatic needle removal may be performed by only pressing the skin touch switch  20  against the skin without pushing the switch  17 . For this purpose, the microprocessor  100  should monitor the time periods required for the respective operations from when the skin touch switch  20  touches the skin, whereby all of the operations can be carried out at appropriate timings. Further, the microprocessor  100  may sound a buzzer  27  with varying the tone according to the timings of the respective operations, i.e., needle insertion, administration, completion of administration, needle removal, etc., whereby a person having bad eyesight as well as a person having normal eyesight can recognize the operation state by the sound, and they can use the administration instrument with peace in mind. 
     Further, if the user forgets about attaching the injection needle  1  when performing dissolving or administration, dissolving or administration are prevented by the operation as follows. 
     This operation will be described with reference to  FIGS. 2, 3, and 4 . 
     With reference to  FIG. 4 , the driver of the motor  13  is provided with a detection resistor  123  for converting a current that flows in the motor  13  into a voltage. The voltage is compared with a reference voltage that is previously set by a reference voltage setting resistor  124  and a reference voltage setting resistor  125  in a comparator  126 . When the user presses the switch  17  to perform dissolving or administration without the injection needle, the motor  13  tries to normally rotate in such a direction that the drug solution push piston  9  pushes out the drug solution  9 . However, in the rooms filled with the drug solution  5  ( 22 ) and the powder preparation  23 , respectively, there is no way to make the air or the drug solution escape because the injection needle  1  is not attached, and thereby the pressure increases suddenly. However, the motor  13  tries to continue the rotation, more current flows into the detection resistor  123 , and thereby the voltage of the detection resistor  123  increases. When the voltage of the detection resistor  123  exceeds the voltage that is set by the reference voltage setting resistor  124  and the reference voltage setting resistor  125 , the output of comparator  126  instructs the microprocessor  100  to stop the motor  13 . Of course, a program for giving the above-mentioned instruction is previously incorporated in the microprocessor  100 . 
     APPLICABILITY IN INDUSTRY 
     As described above, the automatic administration instrument for medical use according to the present invention is useful as an administration instrument for administering drug solutions such as growth hormone, insulin, and the like.