a medical instrument according to exemplary embodiments of the invention is described in detail below with reference to the drawings . fig1 illustrates a medical instrument ( medical instrument 1 ) according to one embodiment of the invention , wherein ( a ) is a plan view , ( b ) is a bottom view , ( c ) is a front view , ( d ) is a left side view , and ( e ) is a right side view illustrating the overall configuration of the medical instrument 1 . an example in which the medical instrument 1 is scissors that are used to incise or excise body tissue during surgery or the like is described below . note that the medical instrument according to the embodiments of the invention may also be applied to a holding instrument for holding a suture or body tissue , a holder , a needle holder , or tweezers for performing a holding operation or a cutting operation , and the like . as illustrated in fig1 , the medical instrument 1 includes two manipulation members 14 that are held by the user ( e . g ., doctor ), two plate - shaped elastic members 11 that are respectively secured on one end of the two manipulation members 14 , and two opening - closing members 15 that are respectively secured on the other end of the two manipulation members 14 . a blade 15 a ( i . e ., functional part ) is formed at one end of each of the opening - closing members 15 , and the elastic members 11 are connected to each other ( engage each other ) at one end thereof . the opening - closing members 15 are pivotally connected to each other through a pivot 13 in the vicinity of the blades 15 a . the manipulation members 14 are preferably formed of pure titanium that is lightweight and exhibits high strength and excellent corrosion resistance , and the elastic members 11 are preferably formed of β - titanium that exhibits excellent spring properties . the manipulation member 14 and the elastic member 11 may be bonded by laser welding or the like . it is preferable to polish the joint between the manipulation member 14 and the elastic member 11 after bonding in order to remove a step . it is preferable to form a hole , a groove , or irregularities on the surface of the manipulation members 14 in order to provide the manipulation members 14 with non - slip properties , or decorate the manipulation members 14 . the elastic members 11 are formed in the shape of a leaf spring . the thickness of the elastic members 11 is adjusted so that the blade - edge opening - closing amount of the opening - closing members 15 and the pressing force applied to the manipulation members 14 have a linear proportional relationship . fig3 illustrates a graph showing the relationship between the pressing force and the amount of deformation measured using a commercially available product that is similar to the medical instrument 1 according to one embodiment of the invention ( see ( a )). the commercially available product has a configuration in which the elastic member is formed of stainless steel . when using the commercially available product , the pressing force and the amount of deformation have a non - linear ( curved ) relationship immediately after the start of incision or excision , and incision or excision is performed while increasing the pressing force . fig3 also illustrates a graph showing the relationship between the pressing force and the amount of deformation that is achieved by the medical instrument 1 according to one embodiment of the invention ( see ( b )). the thickness and the length of the elastic members 11 are selected so that the linear relationship between the pressing force and the amount of deformation does not change during incision or excision ( see ( b ) in fig3 ) when the elastic members 11 are combined with the manipulation members 14 and the opening - closing members 15 . the elastic members 11 are designed to have spring properties ( determined by a slope at an angle a ) that ensure that a change in pressing force “ p 4 to p 5 ” during incision or excision ( see ( b ) in fig3 ) is almost equal to a change in pressing force “ p 1 to p 2 ” during incision or excision ( see ( a ) in fig3 ). when β - titanium is used as the material for forming the elastic members 11 , and the thickness of the elastic members 11 is about 0 . 20 to 0 . 35 mm , the length of the elastic members 11 is preferably determined to satisfy the above conditions taking account of the relationship with the opening - closing members 15 and the manipulation members 14 . the manipulation member 14 and the opening - closing member 15 are preferably bonded using a fastening means 16 such as a bolt or a rivet . it is possible to replace the opening - closing member 15 with another opening - closing member that differs in length , angle , weight , material , or the like . the center - of - gravity position of the medical instrument 1 may be adjusted by adjusting the weight , the length , the shape , and the like of the manipulation member 14 , the opening - closing member 15 , and the elastic member 11 . when the manipulation member 14 and the opening - closing member 15 are bonded using the fastening means 16 such as a bolt or a rivet so that the manipulation member 14 and the opening - closing member 15 can be replaced , it is possible to adjust the center - of - gravity position corresponding to the type of surgery , the surgery target part , or user &# 39 ; s preference . the standard center - of - gravity position of the medical instrument 1 according to one embodiment of the invention is set to be identical with ( or set to a position situated forward to some extent as compared with ) the position at which the user &# 39 ; s fingers come in contact with the manipulation members 14 . the blade 15 a is preferably formed of a metal material ( e . g ., nickel - based alloy ) that is non - magnetic and exhibits excellent rust resistance , excellent wear resistance , and excellent corrosion resistance . the blade 15 a may be formed integrally with the opening - closing member 15 , or may be formed separately from the main body of the opening - closing member 15 , and bonded to the main body of the opening - closing member 15 by laser welding , friction welding , or the like . the blade 15 a and the main body of the opening - closing member 15 may be formed of similar metals , or may be formed of dissimilar metals . for example , when the blade 15 a is formed of a nickel - based alloy , the main body of the opening - closing member 15 may be formed of stainless steel that is non - magnetic and exhibits excellent wear resistance and excellent corrosion resistance , for example . note that dissimilar metals or dissimilar alloys may be bonded using a known technique such as the method disclosed in japanese patent no . 4277117 , japanese patent no . 4657508 ( that is owned by the applicant of the present application ), or japanese patent no . 4823715 ( that is owned by the applicant of the present application ). according to the medical instrument 1 having the above configuration , when the user has applied pressing force in the direction in which the elastic members 11 approach each other while holding the manipulation members 14 , the elastic members 11 are elastically deformed , and the blades 15 a are closed around the pivot 13 ( fulcrum ). this makes it possible to incise or excise body tissue , for example . when the pressing force applied to the elastic members 11 has been reduced , the elastic members 11 are deformed to return to the original position , and the blades 15 a are opened . according to the medical instrument 1 having the above configuration , since the opening - closing amount of the blades 15 a can be finely adjusted by merely changing the pressing force applied to the elastic members 11 through the manipulation members 14 , the medical instrument 1 is advantageous for incising or excising body tissue such as a very thin biomembrane , a microscopic blood vessel , or a nerve . fig2 illustrates a medical instrument ( medical instrument 1 ′) according to another embodiment of the invention , wherein ( a ) is a plan view , ( b ) is a bottom view , ( c ) is a front view , ( d ) is a left side view , and ( e ) is a right side view illustrating the overall configuration of the medical instrument v . in fig2 , the same members and the like as those illustrated in fig1 are indicated by the same reference symbols . detailed description of these members and the like is omitted . the medical instrument 1 ′ differs from the medical instrument 1 in that the manipulation members 14 are bent in the shape of the letter “ l ”. specifically , the shape , the length , and the weight of the manipulation member 14 , and the shape , the length , and the weight of the opening - closing member 15 , can be arbitrarily changed corresponding to the application or user &# 39 ; s preference . in this case , the standard center - of - gravity position is the same as described above . the elastic members 11 may be formed of a material other than β - titanium as long as the pressing force and the amount of deformation ( blade - edge opening - closing amount ) at least partially have a linear relationship , and moderate spring properties can be observed . for example , the elastic members 11 may be formed of a superelastic alloy so that the pressing force and the amount of deformation have a unique relationship . fig4 illustrates a graph showing the relationship between the pressing force and the amount of deformation when the elastic members 11 are formed of a superelastic alloy ( another embodiment of the invention ). as illustrated in fig4 , when the elastic members 11 are formed of a superelastic alloy , the pressing force and the amount of deformation have a linear relationship during incision or excision when the elastic members 11 are combined with the manipulation members 14 and the opening - closing members 15 . the spring properties a during incision or excision are appropriate . therefore , the elastic members 11 of the medical instrument according to the embodiments of the invention may be formed of a superelastic alloy although the pressing force and the amount of deformation have a unique relationship . in this case , the elastic members 11 are preferably designed to have spring properties that ensure that a change in pressing force “ p 4 to p 5 ” during incision or excision is almost equal to a change in pressing force “ p 1 to p 2 ” during incision or excision ( see ( a ) in fig3 ). for example , the fastening means 16 is not limited to a bolt or a rivet . a rod - like shaft may be inserted into a through - hole formed in the manipulation member 14 and a through - hole formed in the opening - closing member 15 , and one end or both ends of the rod - like shaft may be caulked to secure the manipulation member 14 and the opening - closing member 15 . although an example in which the manipulation member 14 and the elastic member 11 are provided separately , and connected to each other has been described above , the manipulation member 14 and the elastic member 11 may be formed integrally , or the manipulation member 14 may form part of the elastic member 11 . the embodiments of the invention can be widely applied to a medical instrument ( e . g ., holder , needle holder , scissors , or tweezers ) that is used to implement a gripping operation , a holding operation , an incision operation , an excision operation , a cutting operation , or the like .
a medical instrument effectively suppresses a situation in which the edge of a blade springs immediately after completion of incision , excision , or the like . the medical instrument includes manipulation members that are held by a user , elastic members that are respectively secured on one end of the manipulation members , and intersect each other at one end thereof , and opening - closing members that are respectively secured on the other end of the manipulation members , and intersect each other at a pivot , functional parts for implementing a gripping operation , a holding operation , a cutting operation , or the like being respectively provided at one end of the opening - closing members , the functional parts being opened and closed by adjusting a pressing force applied to the manipulation members , the opening - closing members , the manipulation members , and the elastic members being configured so that the pressing force applied to the manipulation members and an opening - closing amount of the functional parts have a linear proportional relationship during a period in which the functional parts are operated .