Abstract:
A surgical instrument is disclosed that includes: a handle; a shaft coupled to the handle and extending in one direction; a bending part formed on a portion of the shaft; a driving part mounted on the handle and configured to generate a particular driving power; and a power transmission mechanism configured to transmit the driving power generated by the driving part to the bending part such that the bending part is bent. By mounting a driving part onto the surgical instrument and enabling the shaft to bend by a simple manipulation on a controller, it is possible to readily change the direction of the effector even when holding the instrument in one hand. Also, since the shaft is bent while the instrument is held, the reaction force applied on the effector when changing the direction of the effect can be felt by the user, providing a “haptic feedback”.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the National Phase of PCT/KR2010/001314 filed on Mar. 3, 2010, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 10-2009-0019072 filed in the Republic of Korea on Mar. 6, 2009, all of which are hereby expressly incorporated by reference into the present application. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a surgical instrument. 
         [0003]    In the field of medicine, surgery refers to a procedure in which a medical apparatus is used to make a cut or an incision in or otherwise manipulate a patient&#39;s skin, mucosa, or other tissue, to treat a pathological condition. A surgical procedure such as a laparotomy, etc., in which the skin is cut open so that an internal organ, etc., may be treated, reconstructed, or excised, can incur problems of blood loss, side effects, pain, scars, etc. 
         [0004]    Thus, a popular alternative is “laparoscopic surgery” or “minimal invasive surgery”, which involves perforating a small insertion hole in the skin, instead of making an incision, and inserting an endoscope, laparoscope, surgical instrument, microscope for microsurgery, etc., through the insertion hole. 
         [0005]    As illustrated in  FIG. 1 , a conventional surgical instrument  10  used for such laparoscopic surgery may be structured to have an effector  16  coupled to the end of a shaft  14  extending from a handle  12 . When the direction of the effector  16  has to be changed during surgery, the conventional instrument is manipulated by a person manually releasing a locking device  18 , manually operating a manipulator  26  to bend a portion  20  of the shaft like a joint, and then locking the locking device  18  again. 
         [0006]    This conventional method of manually manipulation, however, requires manual manipulation of the locking device  18  and the manipulator  26  during surgery, and thus requires both hands to manipulate the instrument  10 . As such, the surgical instrument  10  cannot be manipulated, if there are surgical tools held in both hands already. 
         [0007]    The information in the background art described above was obtained by the inventors for the purpose of developing the present invention or was obtained during the process of developing the present invention. As such, it is to be appreciated that this information did not necessarily belong to the public domain before the patent filing date of the present invention. 
       SUMMARY 
       [0008]    An aspect of the invention is to provide a surgical instrument with which the shaft can be bent by a simple manipulation on a controller to readily change the direction of the effector. 
         [0009]    One aspect of the invention provides a surgical instrument that includes: a handle; a shaft coupled to the handle and extending in one direction; a bending part formed on a portion of the shaft; a driving part mounted on the handle and configured to generate a particular driving power; and a power transmission mechanism configured to transmit the driving power generated by the driving part to the bending part such that the bending part is bent. 
         [0010]    An effector can further be included that is coupled to one end of the shaft and operated to perform an action required for surgery according to a user manipulation on the handle. In this case, a rotation manipulator can further be included that is rotatably mounted on the handle and connected to the effector to enable the effector to rotate about an extending direction of the shaft. Also, the effector can include a pair of jaws that engage each other, and a grip manipulator can be coupled to the handle and connected to the pair of jaws to enable the pair of jaws to open and close. 
         [0011]    The bending part can be formed adjacent to the effector, which may change direction according to the curving of the bending part. In this case, the bending part can include a snake type joint. 
         [0012]    The driving part can include: a motor part; a power source part configured to supply power required for driving the motor part; and a controller configured to control a driving of the motor part. The power source part can include a battery carried within the handle. The motor part can be positioned exterior to the handle and be connected to the handle by a driving power transmission mechanism. The controller can include a direction manipulator configured to control a driving of the motor part to bend the bending part in correspondence with a manipulation direction. 
         [0013]    The driving part can include a hold capability for driving the motor part such that, if the direction manipulator is manipulated in a particular direction, the bending part remains in a bent state in correspondence with the manipulation. Also, the driving part can further include a release manipulator configured to control a driving of the motor part to restore the bending part to its initial state. 
         [0014]    In this case, the direction manipulator can be manipulated in two or more directions, and the motor part can include a first motor and a second motor, the first motor driven in correspondence with a first manipulation direction of the direction manipulator, and the second motor driven in correspondence with a second manipulation direction of the direction manipulator. The bending part can be bent in a first direction according to a driving of the first motor and be bent in a second direction according to a driving of the second motor. 
         [0015]    The power transmission mechanism can include a first wire, which connects the first motor with two points on the bending part facing each other along the first direction, and a second wire, which connects the second motor with two points on the bending part facing each other along the second direction. Also, the power transmission mechanism can further include a reaction force isolator part that is interposed between the first and second wires and the bending part and is configured to block a reaction force, by which the bending part tends toward returning to an original position, from being transmitted to the first and second motors. The reaction force isolator part can include a worm gear. The worm gear can include a worm and a worm wheel mating with the worm, where the worm can be separated from the worm wheel in correspondence with a manipulation on a release manipulator equipped on the driving part. 
         [0016]    The shaft can be detachably coupled to the handle, and the power transmission mechanism can include a first power transmission mechanism built into the shaft and a second power transmission mechanism built into the handle, where the first power transmission mechanism and the second power transmission mechanism can be connected to each other when the shaft is coupled to the handle. 
         [0017]    By mounting a driving part, e.g. a motor, etc., onto the surgical instrument and enabling the shaft to bend by a simple manipulation on a controller, e.g. a joystick, etc., a preferred embodiment of the invention makes it possible to readily change the direction of the effector even when holding the instrument in one hand. Also, since the shaft is bent while the instrument is held, a significant portion of the reaction force that is applied on the effector when changing the direction of the effect can be felt by the user, providing a “haptic feedback”. 
         [0018]    Additional aspects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a perspective view illustrating an instrument for robot surgery according to the related art. 
           [0020]      FIG. 2  is a side-elevational view conceptually illustrating a surgical instrument according to an embodiment of the invention. 
           [0021]      FIG. 3  is a plan view illustrating the curving of a bending part according to an embodiment of the invention. 
           [0022]      FIG. 4  is a magnified view of portion “A” in  FIG. 3 . 
           [0023]      FIG. 5  illustrates a driving part according to an embodiment of the invention. 
           [0024]      FIG. 6  illustrates a reaction force isolator part according to an embodiment of the invention. 
           [0025]      FIG. 7  illustrates the operation of a release manipulator according to an embodiment of the invention. 
           [0026]      FIG. 8  illustrates the detachable coupling of a shaft and a handle according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. 
         [0028]    While terms including ordinal numbers, such as “first” and “second,” etc., may be used to describe various components, such components are not limited to the above terms. The above terms are used only to distinguish one component from another. For example, a first component can be referred to as a second component, and likewise a second component can be referred to as a first component, without departing from the scope of the invention. When a component is said to be “connected to” or “accessing” another component, it is to be appreciated that the two components can be directly connected to or directly accessing each other but can also include one or more other components in-between. 
         [0029]    The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the present invention. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms “including” or “having,” etc., are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof may exist or may be added. 
         [0030]    Also, in providing descriptions referring to the accompanying drawings, those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant descriptions are omitted. In the written description, certain detailed explanations of related art are omitted, when it is deemed that they may unnecessarily obscure the essence of the present invention. 
         [0031]      FIG. 2  is a side-elevational view conceptually illustrating a surgical instrument according to an embodiment of the invention,  FIG. 3  is a plan view illustrating the curving of a bending part according to an embodiment of the invention, and  FIG. 4  is a magnified view of portion “A” in  FIG. 3 . Illustrated in  FIG. 2  to  FIG. 4  are a handle  30 , a rotation manipulator  32 , a grip manipulator  34 , a shaft  40 , a bending part  42 , an effector  44 , a driving part  50 , a direction manipulator  58 , a power transmission mechanism  70 , a first wire  72 , and a second wire  74 . 
         [0032]    With this embodiment, instead of manually implementing a manipulation for bending the shaft  40  of the surgical instrument to change the direction of the effector  44  coupled to the end of the shaft  40  as in the related art, the bending may be performed automatically by using the power of a motor, etc. Thus, by simply manipulating a switch while holding the instrument, the direction of the effector  44  can be changed easily, and during this process, the user can be made able to sense the reaction force applied on the front end of the effector  44 , i.e. the user can be provided with haptic feedback. 
         [0033]    An instrument according to this embodiment relates to a so-called “motorized handheld instrument”. As illustrated in  FIG. 2 , a bending part  42  may be formed on the end of the shaft  40 , and as illustrated in  FIG. 3 , the bending part  42  may be curved freely using motor power. Thus, for an instrument manipulated manually, the shaft  40  can be made to bend by using the force of a motor, etc., so that the end portion of the instrument can move up, down, left, and right. 
         [0034]    As illustrated in  FIG. 2 , an instrument according to this embodiment has a basic structure of a shaft  40  extending from a manipulating handle  30 . A bending part  42  capable of bending freely may be formed on the end portion of the shaft  40 , a driving part  50  for generating a driving power that curves the bending part  42  may be mounted on the handle  30 , and the driving part  50  and bending part  42  may be connected by a power transmission mechanism  70 , so that the bending part  42  may curve in a desired direction according to the driving of the driving part  50 . 
         [0035]    A forceps-like effector  44  made of a pair of jaws can be coupled to the end of the shaft  40 , and as the user holds and manipulates the handle  30 , the effector  44  may perform various actions required for surgery, such as cutting, gripping, rotating, etc. To this end, various manipulators corresponding to the actions of the effector  44  can be coupled onto the handle  30 , such as a rotation manipulator  32  that enables the effector  44  to rotate about the extending direction of the shaft  40 , a grip manipulator  34  that enables the pair of jaws to open and close and perform a gripping action, and so on. 
         [0036]    Accordingly, each manipulator and the effector  44  can be connected in various ways to implement various actions on the effector  44 . For example, as illustrated in  FIG. 2 , the rotation manipulator  32  rotatably coupled to the handle  30  may be connected with the shaft  40 , and may thereby enable the shaft  40  as well as the effector  44  connected to its far end to rotate according to the rotation of the rotation manipulator  32 , and the grip manipulator  34  coupled to the handle  30  in the form of a lever may be connected by wires with the pair of jaws, so that when the grip manipulator  34  is pulled on, the tensional force may be transmitted via the wires, to enable the effector  44  to perform a gripping action. Various other connecting methods can be applied according to the operating method of the effector  44  and the operating method of each manipulator. 
         [0037]    The bending part  42  may be formed on a portion of the shaft  40  to serve as a joint at which the shaft  40  curves in a certain direction. In the embodiment illustrated in  FIG. 2 , the bending part  42  is formed on an end portion of the shaft  40 , i.e. at a portion adjacent to the effector  44 . 
         [0038]    As the driving part  50  generates and transmits a driving power to cause the bending part  42  to curve, as described above, the portion of the shaft  40  beyond the bending part  42 , i.e. the portion to which the effector  44  is coupled, may move in a particular direction, and thus the direction in which the effector  44  is facing may be changed by the curving of the bending part  42 . 
         [0039]    That is, not only is it possible to manipulate an instrument according to this embodiment such that the effector  44  performs various actions (cutting, gripping, rotating, etc.) required for surgery, it is also possible to change the direction in which the effector  44  is facing, so that various surgical manipulations can be performed on a desired surgical site without having to change the direction of the entire instrument. Furthermore, even in situations where the direction of the instrument cannot be changed, the effector  44  can be made to change direction in performing surgery by bending the shaft  40 . 
         [0040]    To thus curve a portion of the shaft  40 , a bending part  42  according to this embodiment can be implemented by combining various devices such as hinges, pivots, bellows, etc., or be implemented in a so-called “snake type” form, having multiple flexible joints installed continuously as illustrated in  FIG. 4 . 
         [0041]    With the bending part  42  having a snake type form, it is possible to secure wires onto its inner walls and provide bending in a desired direction by transmitting tensional forces through the wires, as will be described later. For example, if four wires corresponding to the up, down, left, and right directions are secured onto the inner walls of the bending part  42 , pulling on the left wire and loosening the right wire can cause the bending part  42  to bend left, due to the tension of the wire. 
         [0042]    A description has been provided above on the overall structure of a surgical instrument according to this embodiment. However, it is not absolutely necessary that a motor be used for a driving part  50  according to this embodiment; various mechanisms for generating driving power can be used to curve the bending part  42 . Also, it is not absolutely necessary that the driving power generated and transmitted from the driving part  50  be used for curving the bending part  42 ; the driving power can be utilized as the driving power for various manipulations such as operating the effector  44 , etc. 
         [0043]    Furthermore, an instrument according to this embodiment is not necessarily limited to a manual type in which the user holds the instrument in one hand; a setup can be implemented in which the handle portion  30  is mounted on a surgical robot arm and is operated by driving power transmitted from the robotic arm. A more detailed description will now be provided as follows on the operation of each part of the instrument. 
         [0044]      FIG. 5  illustrates a driving part according to an embodiment of the invention. Illustrated in  FIG. 5  are a shaft  40 , a driving part  50 , a first motor  52 , a second motor  54 , a power source part  56 , a direction manipulator  58 , a release manipulator  60 , a first wire  72 , and a second wire  74 . 
         [0045]      FIG. 5  is used to illustrate an example in which a driving part  50  according to this embodiment is implemented by a pulley-coupling wires onto a pair of motors. 
         [0046]    A driving part  50  according to this embodiment can be composed of a motor part, a power source part  56 , and a controller that controls the driving of the motor part. In this embodiment, the motor may be used for only the curving manipulation of the bending part  42 , and a motor can be used with a capacity tantamount to generating the required power. In this case, a motor can be used having a size that allows the motor to be carried within the handle  30 . 
         [0047]    However, it is not absolutely necessary that a motor part according to this embodiment be carried within the handle; it is also possible to install the motor part exterior to the handle and connect the motor part with the handle by a driving power transmission mechanism such as a “cable conduit”, etc., so as to supply driving power from the exterior. 
         [0048]    The power source part  56  may be a component that supplies electrical power required for driving the motor, and can receive electrical power from the exterior or employ a battery, such as of a regular or rechargeable type, etc., carried within the handle in order to improve the portability of the instrument. As described above, a miniature motor can be used to generate a power sufficient for curving the bending part  42 , and accordingly, the power source part  56  can also be designed with a small capacity, so that the driving part  50  can thus be composed with low cost. 
         [0049]    The controller may be a part that controls the driving of the motor part. With the present embodiment, a direction manipulator  58  such as a miniature joystick or direction keys can be installed as a controller on the handle portion  30  in a manner corresponding to the curving direction of the bending part  42 , so that the curving direction of the bending part  42  can be controlled more intuitively. For example, if the bending part  42  is formed to bend in the up, down, left, and right directions, a joystick, etc., can be installed that is manipulated in the up, down, left, and right directions, such that the manipulation direction of the direction manipulator  58  matches the curving direction of the bending part  42 , allowing the user to intuitively manipulate the direction manipulator  58  and curve the bending part  42 . 
         [0050]    As illustrated in  FIG. 3 , manipulating the direction manipulator  58  to the right (R) may correspondingly curve the bending part  42  to the right (R), while manipulating the direction manipulator  58  to the left (L) may correspondingly curve the bending part  42  to the left (L). 
         [0051]    In order that the manipulation of the direction manipulator  58  in an up, down, left, or right direction may drive a motor to curve the bending part  42 , a motor part according to this embodiment can employ a pair of motors  52 ,  54  as illustrated in  FIG. 5 . 
         [0052]    That is, by making provisions such that the first motor  52  is driven according to an up and down manipulation of the direction manipulator  58 , the second motor  54  is driven according to a left and right manipulation of the direction manipulator  58 , the bending part  42  is moved up and down according to the driving of the first motor  52 , and the bending part  42  is moved left and right according to the driving of the second motor  54 , the manipulation direction of the direction manipulator  58  and the curving direction of the bending part  42  can be matched. 
         [0053]    However, it is not absolutely necessary that the manipulation direction of the direction manipulator  58  and the curving direction of the bending part  42  according to this embodiment be set to up and down directions and left and right directions. Obviously, the movements of the direction manipulator  58  and the bending part  42  can be matched with the direction manipulator  58  manipulated in any two direction, i.e. a first manipulation direction and a second manipulation direction, and the bending part  42  curved in a corresponding manner in a first direction and a second direction. 
         [0054]    Each point of the first and second motors  52 ,  54  and the bending part  42  can be connected by a power transmission mechanism  70  such as a wire, etc. For example, the first motor  52  can be connected to two points on the bending part  42  by a first wire  72 , and the second motor  54  can be connected to two points on the bending part  42  by a second wire  74 . 
         [0055]    If the first motor  52  corresponds to curving along the up and down directions, and the second motor  54  corresponds to curving along the left and right directions, as in the example described above, then the first wire  72  connected to the first motor  52  can be connected to two points, an upper and a lower position, of the bending part  42 , while the second wire  74  connected to the second motor  54  can be connected to two points, a left and a right position, of the bending part  42 . Furthermore, if the first motor  52  corresponds to curving in a first direction, and the second motor  54  corresponds to curving in a second direction, then the first wire  72  can be connected to two points on the bending part  42  facing each other along the first direction, while the second wire  74  can be connected to two points on the bending part  42  facing each other along the second direction. 
         [0056]    In addition to the direction manipulator  58 , a driving part  50  according to the present embodiment can include a “hold” capability and a “release” capability. 
         [0057]    The hold capability may keep the bending part  42  in a curved state if the direction manipulator  58  remains untouched. When the direction manipulator  58  is manipulated in a particular direction, the hold capability may lock the driving part  50  in place such that the bending part  42  maintains its bent position in correspondence with the manipulation. 
         [0058]    Various methods can be used to implement this hold capability, such as by having the electrical power continuously supplied to the motor part when the direction manipulator  58  is in a manipulated state in a particular direction so that the motors  52 ,  54  are not operated by external forces and remain still, by choosing a motor having a sufficiently large cogging torque such that the reaction force resulting from the curving of the bending part  42  does not conversely operate the motors  52 ,  54  in order that the motors  52 ,  54  may not be operated by external forces besides the manipulation of the direction manipulator  58 , by installing a stopper, etc., on the direction manipulator  58  so that the direction manipulator  58  is mechanically locked after being manipulated in a particular direction, or by installing a separate hold switch which may be pressed to lock the manipulation of the direction manipulator  58  and maintain the bent state of the bending part  42 . 
         [0059]    Correspondingly to the hold capability, a release capability can be implemented. The release capability may cause the shaft  40 , which has been bent to a particular state, to automatically return to its original position when a release manipulator  60  such as a release button, etc., is manipulated. The release manipulator  60  may serve to drive the motor part to restore the bending part  42  to its initial state. 
         [0060]    The release manipulator  60  can be implemented various ways. For example, the release manipulator  60  can be implemented in the form of a separate button. Alternatively, a press capability can be added to a joystick, so that the joystick may operate as the direction manipulator  58  when the joystick is manipulated up, down, left, or right, and as the release manipulator  60  when the joystick is pressed. 
         [0061]      FIG. 6  illustrates a reaction force isolator part according to an embodiment of the invention, and  FIG. 7  illustrates the operation of a release manipulator according to an embodiment of the invention. Illustrated in  FIG. 6  and  FIG. 7  are a shaft  40 , a bending part  42 , a driving part  50 , a direction manipulator  58 , a release manipulator  60 , first wires  72 , second wires  74 , a reaction force isolator part  76 , a worm  78 , and a worm wheel  80 . 
         [0062]    This embodiment is illustrated for an example in which a reaction force isolator part  76  is installed in the middle of the power transmission mechanism  70 , so that when power is generated and transmitted from the driving part  50  to curve the bending part  42 , the reaction force resulting from the curving of the bending part  42  does not conversely act on the motor and cause damage to or malfunctioning of the motor. 
         [0063]    That is, in connecting the driving part  50  and the bending part  42  with wires, a gear such as a worm gear  78 ,  80  can be placed in-between. Thus, the driving power may be transmitted from the driving part  50  to the bending part  42  (forward direction), but conversely a reaction force due to bending from the bending part  42  to the driving part  50  (reverse direction) may be isolated such that it is not directly transmitted to the motor. 
         [0064]    By placing the reaction force isolator part  76 , such as a worm gear  78 ,  80 , etc., between the first and second wires  72 ,  74  and the bending part  42  as illustrated in  FIG. 6 , reaction forces of the bending part  42  tending to return to its original position can be prevented from being directly transmitted to the first and second motors  52 ,  54  and incurring unnecessary loads. 
         [0065]    In this case, the forces generated and transmitted from the motor may not be applied directly on the bending part  42 . Rather, the motor may rotate the worm  78 , and the worm wheel  80  mating with the worm  78  may rotate correspondingly, so that the tensional forces may be applied to each point of the bending part  42 . In this way, a reaction force resulting from the curving of the bending part  42  can be prevented from being conversely transmitted directly to the motors. 
         [0066]    As described above, it is possible to implement a “release capability” for restoring the curved shaft  40  to its original position, by installing a release manipulator  60  on the driving part  50  and driving the motor part such that the bending part  42  bent into a particular state is restored to its initial state. Not only is it possible to electronically restore the shaft  40  according to a manipulation of the release button in this manner, it is also possible to implement the release capability by mechanically separating the reaction force isolator part  76 . 
         [0067]    That is, in cases where a worm gear having a worm  78  and a mating worm wheel  80  is used for the reaction force isolator part  76 , manipulating the release manipulator  60  (see B of  FIG. 7 ) can cause the worm  78  to be mechanically separated from the worm wheel  80  and be drawn back (see B′ of  FIG. 7 ), so that the reaction force resulting from curving the bending part  42 , i.e. the elastic restoring force of the bending part  42 , may return the shaft  40  to its original position. 
         [0068]      FIG. 8  illustrates the detachable coupling of a shaft and a handle according to an embodiment of the invention. Illustrated in  FIG. 8  are a handle  30 , a rotation manipulator  32 , a shaft  40 , a driving part  50 , a power transmission mechanism  70 , a worm  78 , and a worm wheel  80 . 
         [0069]    An instrument according to this embodiment can be manufactured to have a structure in which the shaft portion  40  is disposable and the handle portion  30  is reusable. That is, the shaft portion  40  and the handle portion  30 ,  40 ′ can each be manufactured separately but in a detachably coupling structure, so that the shaft portion  40  may be discarded after use, and a new shaft may be fastened again to the handle  30  for reuse as necessary. 
         [0070]    In this case, a power transmission mechanism  70  according to this embodiment may be separated into a first power transmission mechanism  70  built into the shaft side  40  and a second power transmission mechanism  70 ′ built into the handle side  30 . By forming coupling devices that engage each other on the end portions of the separated power transmission mechanisms  70 ,  70 ′, respectively, the first power transmission mechanism  70  and second power transmission mechanism  70 ′ can be connected with each other during the coupling of the shaft  40  to the handle  30 . 
         [0071]    For example, a protrusion can be formed at the end portion of a wire built into the shaft side  40 , and an indentation into which the protrusion may fit can be formed at the end portion of a wire built into the handle side  30  ( 40 ′), so that when coupling the shaft  40  onto the handle  30 , the wires may be coupled and connected with each other. 
         [0072]    Also, if a reaction force isolator part  76  such as a worm gear  78 ,  80 , etc., is to be installed in the shaft  40 ,  40 ′ as described with reference to  FIG. 6 , the worm  78  can be installed in one side  40 ′ of the separated shaft and the worm wheel  80  mating with the worm  78  can be installed in the other side  40 . Thus, during the process of separating and coupling the shaft  40 , the worm gear can be mated, so that the power transmission mechanisms  70 ,  70 ′ may be connected naturally. 
         [0073]    However, it is not absolutely necessary that in an instrument according to this embodiment the shaft has to be separated at a portion adjacent to the handle; it is also possible to manufacture the shaft to have a structure that it is separated in its middle portion, such that one portion is connected to the handle and the other portion serves as the shaft tip, with the two portions detachably coupling with each other. The shaft tip can be disposable, while the handle and the shaft portion connected to the handle can be reusable. 
         [0074]    While the present invention has been described with reference to particular embodiments, it will be appreciated by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention, as defined by the claims appended below.