Patent Publication Number: US-2021177449-A1

Title: Medical scissors for microinvasive applications

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2019 134 017.9, filed Dec. 11, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention pertains to medical scissors for microinvasive applications and to a medical instrument with such scissors. 
     TECHNICAL BACKGROUND 
     Medical scissors for microinvasive applications must meet special and especially high requirements. These requirements arise, on the one hand, from the small dimensions which per se already make difficult or rule out a transfer of concepts that have been tried and tested in markedly larger scissors. In addition, there are, on the other hand, requirements for a special reliability, which result from the special application situation. In view of markedly less direct mechanical control and markedly less direct mechanical feedback, medical scissors for microinvasive applications shall cut reliably at the time of each closing. A clamping of the material to be cut between the scissor blades instead of a cutting or a slipping away of the material to be cut distally may not only prolong the duration of a microinvasive action, but may absolutely put the health of the patient at risk in individual cases. 
     SUMMARY 
     An object of the present invention is to create improved medical scissors for microinvasive applications and an improved medical instrument having such scissors. 
     Embodiments of the present invention are based on the idea of configuring the properties of the cutting edges of the scissor blades, especially the wedge angle or the cutting angle or the widths of the beveled surface in an oscillating manner, i.e., alternately increasing several times and decreasing several times. 
     Medical scissors for microinvasive applications comprises a first scissor blade with a first cutting edge between a flank surface and a beveled surface, a second scissor blade, which is movable in relation to the first scissor blade, with a second cutting edge between a flank surface and a beveled surface and a guiding device for the mechanical guiding of the second scissor blade in relation to the first scissor blade such that the second cutting edge touches the first cutting edge at any time in a point of intersection, wherein the guiding device is connected or can be connected rigidly to a shaft of a microinvasive instrument, wherein the first cutting edge is characterized by a first parameter, which increases several times and decreases several times along the first cutting edge, wherein the second cutting edge is characterized by a second parameter, which increases several times and decreases several times along the second cutting edge, wherein the first parameter and the second parameter are in each case the wedge angle between the flank surface and the beveled surface or the cutting angle or the width of the beveled surface. 
     The cutting edges are convex, sharp edges, which are also designated as facets of a blade in the case of scissors. The cutting angle is the sum of the clearance angle and the wedge angle. The beveled surface is the plane or slightly curved surface directly adjacent to the cutting edge. 
     The guiding device and the cutting edges are especially configured and arranged such that the cutting edges touch one another at any time in precisely one point of intersection. 
     The guiding device is, for example, a joint, which exclusively makes possible in a positive-locking manner a pivoting of the second scissor blade in relation to the first scissor blade about a pivot axis defined in a positive-locking manner by the joint. The joint can make possible a pivoting of both scissor blades about a common pivot axis or about two different pivot axes in relation to the distal end of the shaft. As an alternative, the first scissor blade may be connectable or can be connected rigidly, i.e., immovably to the distal end of a shaft. 
     The guiding device is connected or can be connected mechanically to the distal end of the shaft in an especially non-destructive, detachable manner. As an alternative, the guiding device may be connected permanently and not in a non-destructive, detachable manner to the distal end of the shaft. 
     The first parameter increases at least twice and decreases twice especially alternately along the first cutting edge. The second parameter decreases at least twice and increases twice especially alternately along the second cutting edge. The first parameter and the second parameter may each vary along the cutting edges continuously or intermittently, i.e., in increments. The first parameter and the second parameter may each oscillate between a predefined minimum and a predefined maximum and with a constant spatial period. As an alternative, the variations of the first parameter and of the second parameter may vary both in the period and in the amplitude, i.e., the difference of adjacent minima and maxima. The location dependency and the rates of change of the parameters may also repeat or not repeat along the cutting edges. 
     The same parameters or different parameters may vary at the first cutting edge and at the second cutting edge. For example, the wedge angle may vary at both cutting edges or the cutting angle may vary at both cutting edges or the widths of the beveled surfaces may vary at both cutting edges. As an alternative, for example, the wedge angle may vary at one cutting edge and the width of the beveled surface may vary at the other cutting edge. 
     In medical scissors, as they are described here, especially the first cutting edge has a first section, in which the first parameter is not greater than a first predefined value, and a second section, in which the first parameter is not smaller than a second predefined value, which is greater than the first predefined value, wherein the second cutting edge has a first section, in which the second parameter is not greater than a third predefined value, and a second section, in which the second parameter is not smaller than a fourth predefined value, which is greater than the third predefined value, wherein the second section of the first cutting edge is located opposite the first section of the second cutting edge and the second section of the second cutting edge is located opposite the first section of the first cutting edge. 
     In medical scissors, as they are described here, especially the first cutting edge has alternately first sections in which the first parameter is not greater than a first predefined value and second sections, in which the first parameter is not smaller than a second predefined value, which is greater than the first predefined value, wherein the second cutting edge has first sections, in which the second parameter is not greater than a third predefined value, and second sections, in which the second parameter is not smaller than a fourth predefined value, which is greater than the third predefined value. 
     In medical scissors, as they are described here, especially the first cutting edge has alternately first sections in which the first parameter is not greater than a first predefined value and second sections, in which the first parameter is not smaller than a second predefined value, which is greater than the first predefined value, wherein the second cutting edge has alternately first sections, in which the second parameter is not greater than a third predefined value, and second sections, in which the second parameter is not smaller than a fourth predefined value, which is greater than the third predefined value, wherein each second section of the first cutting edge is located opposite a first section of the second cutting edge and each second section of the second cutting edge is located opposite a first section of the first cutting edge. 
     The first predefined value is especially the smallest value, which the first parameter has along the entire first cutting edge. As an alternative, the first parameter may attain a value that is smaller than the first predefined value within the first section or within the first sections of the first cutting edge and, as an alternative or in addition, outside of the first section or outside of the first sections. The second predefined value is especially the largest value, which the first parameter attains along the entire first cutting edge. As an alternative, the second parameter may attain a value that is greater than the second predefined value within the second section or within the second sections of the first cutting edge and, as an alternative or in addition, outside of the second section or outside of the second sections of the first cutting edge. 
     The third predefined value is especially the smallest value which the second parameter attains along the entire second cutting edge. As an alternative, the second parameter may attain a value, which is smaller than the third predefined value within the first section or within the first sections of the second cutting edge and, as an alternative or in addition, outside of the first section or outside of the first sections of the second cutting edge. The fourth predefined value is especially the largest value, which the second parameter attains along the entire second cutting edge. As an alternative, the second parameter within the second section or within the second sections of the second cutting edge and, as an alternative or in addition, outside of the second section or outside of the second sections of the section cutting edge may attain a value that is greater than the fourth predefined value. 
     In medical scissors, as they are described here, especially the first cutting edge has alternately first sections, in which the first parameter is smaller than a first predefined value, and second sections, in which the first parameter is greater than the first predefined value, wherein the second cutting edge has alternately first sections, in which the second parameter is smaller than a third predefined value, and second sections, in which the second parameter is greater than the third predefined value, wherein each second section of the first cutting edge is located opposite a first section of the second cutting edge and each second section of the second cutting edge is located opposite a first section of the first cutting edge. 
     Directly adjacent first and second sections of the first cutting edge may be directly adjacent to one another or separated by areas (which are point-like in the mathematical sense), in which the first parameter is neither smaller nor greater than, but rather is identical to the first predefined value. The same applies to the first and second sections of the second cutting edge. 
     The first cutting edge has especially two, three, four or more first sections and two, three, four or more second sections. The second cutting edge has especially two, three, four or more first sections and two, three, four or more second sections. 
     A point at the first cutting edge corresponds to a point at the second cutting edge, when there is a configuration of medical scissors, in which the point at the first cutting edge and the point at the second cutting edge are at the same time identical to the point of intersection of the cutting edges. A section of the first cutting edge is located opposite a section of the second cutting edge, when points within the section of the first cutting edge corresponding to points within the section of the second cutting edge form at least half or at least two thirds or at least three fourths of the section of the first cutting edge and at the same time points within the section of the second cutting edge corresponding to points within the section of the first cutting edge form a corresponding percentage of the section of the second cutting edge. 
     Because of the smaller wedge angle and/or because of the smaller cutting angle and/or because of the smaller width of the beveled surface, first sections of the first cutting edge and first sections of the second cutting edge cut more readily or better than second sections of the first cutting edge and second sections of the second cutting edge. By a first section of the second cutting edge being located opposite each second section of the first cutting edge and a first section of the first cutting edge being located opposite each second section of the second cutting edge, the medical scissors have at least either well-cutting first sections of the first cutting edge or well-cutting first sections of the second cutting edge especially continuously or with small gaps along the cutting edges. At the same time, the profiling of the cutting edges by the alternating arrangement of first sections and of second sections prevent or at least reduce the risk of a slipping away of a material to be cut distally. 
     In medical scissors, as they are described here, the first sections and the second sections of the first cutting edge and the first sections and the second sections of the second cutting edge are especially arranged such that the point of intersection is located at any time at least either at a first section of the first cutting edge or at a first section of the second cutting edge during the closing of the medical scissors. 
     This may make possible a continuous, good cutting action of the medical scissors. 
     In medical scissors, as they are described here, the first sections and the second sections of the first cutting edge and the first sections and the second sections of the second cutting edge are especially arranged such that during the closing of the medical scissors areas, in which the point of intersection is located neither at a first section of the first cutting edge nor at a first section of the second cutting edge, are not larger than adjacent areas, in which the point of intersection is located at a first section of the first cutting edge or at a first section of the second cutting edge. 
     Especially areas of the angle between the scissor blades or areas of the coordinates of the point of interaction along one of the two cutting edges are meant by areas. 
     The especially good cutting property is only interrupted briefly by the short interruptions between areas, in which the point of intersection is located either at a first section of the first cutting edge or at a first section of the second cutting edge. 
     In medical scissors, as they are described here, the first parameter is identical to the first predefined value especially at least either in each first section of the first cutting edge or the second parameter is identical to the third predefined value in each first section of the second cutting edge. 
     In other words, the first parameter is constant, namely especially minimal within the first sections of the first cutting edge, and the second parameter is constant, namely especially minimal within the first sections of the second cutting edge. 
     In medical scissors, as they are described here, the first predefined value and the third predefined value are especially identical. 
     In medical scissors, as they are described here, the first parameter is identical to the second predefined value especially at least either in each second section of the first cutting edge or the second parameter is identical to the fourth predefined value in each second section of the second cutting edge. 
     In other words, the first parameter is constant, namely especially maximal within the second sections of the first cutting edge, and the second parameter is constant, namely especially maximal within the second sections of the second cutting edge. 
     In medical scissors, as they are described here, the second predefined value and the fourth predefined value are especially identical. 
     In medical scissors, as they are described here, the wedge angle of the first cutting edge is not greater than 20° or not greater than 30° or not greater than 40° especially in each first section of the first cutting edge, wherein the wedge angle of the second cutting edge is not greater than 20° or not greater than 30° or not greater than 40° in each first section of the second cutting edge. 
     In medical scissors, as they are described here, the wedge angle of the first cutting edge is not smaller than 60° or not smaller than 70° or not smaller than 80° especially in each second section of the first cutting edge, wherein the wedge angle of the second cutting edge is not smaller than 60° or not smaller than 70° or not smaller than 80° in each second section of the second cutting edge. 
     In medical scissors, as they are described here, the width of the beveled surface of the first cutting edge is not greater than a 20th or not greater than a 50th or not greater than a 100th of the length of the first cutting edge especially in each first section of the first cutting edge, wherein the width of the beveled surface of the second cutting edge is not greater than a 20th or not greater than a 50th or not greater than a 100th of the length of the second cutting edge in each first section of the second cutting edge. 
     In medical scissors, as they are described here, the width of the beveled surface at the first cutting edge is not smaller than a 20th or smaller than a 10th of the length of the first cutting edge especially in each second section of the first cutting edge, wherein the width of the beveled surface of the second cutting edge is not smaller than a 20th or not smaller than a  10 th of the length of the second cutting edge in each second section of the second cutting edge. 
     In medical scissors, as they are described here, a side of the first scissor blade facing away from the flank surface has grooves that are oriented essentially at right angles to the first cutting edge, wherein the first sections of the first cutting edge are each present in a groove, wherein the second sections of the first cutting edge are each present between adjacent grooves. 
     A groove is essentially at right angles to a cutting edge, when the groove forms with the cutting edge an angle of at least 60° or of at least 70° or of at least 80°. Each groove may have a depth that is constant or constant at least over one section or is essentially constant. As an alternative, each groove may have a varying depth, especially a depth which at first increases within a comparatively short section away from the cutting edge and then decreases within a comparatively long section. Each groove may be linear or curved and have a constant or a varying cross section. 
     In particular, the cross sections of all grooves on the side of the first scissor blade facing away from the flank surface have identical or similar cross sections. The cross sections of the grooves on the side of the first scissor blade facing away from the flank surface may vary uniformly from groove to groove along the scissor blade. 
     Grooves on a side of the scissor blade facing away from the flank surface may, on the one hand, be able to be produced in an especially simple manner and effectively spatially modulate the property of the cutting edge of the scissor blade, on the other hand. 
     In medical scissors, as they are described here, the cross section of a groove especially has a linear edge section that is parallel to the first cutting edge. 
     In particular, at the first cutting edge the linear edge section of the cross section of the groove passes over into the first cutting edge. 
     In medical scissors, as they are described here, a web which remains between adjacent grooves has especially a rounded cross section. 
     A rounded cross section has especially radii of curvature, which are not smaller than one third or not smaller than one fourth of the linear dimensions of the cross section. 
     In medical scissors, as they are described here, a side of the second scissor blade facing away from the flank surface has grooves that are oriented essentially at right angles to the second cutting edge, wherein the first sections of the second cutting edge are each present in a groove, and wherein the second sections of the second cutting edge are each present between adjacent grooves. 
     In medical scissors, as they are described here, the cross section of a groove has especially a linear edge section that is parallel to the second cutting edge. 
     In medical scissors, as they are described here, a web which remains between adjacent grooves has especially an angular cross section. 
     An angle or, as an alternative, a plurality of angles of the cross section of the web between adjacent grooves and one or more corresponding convex edges of the web may prevent or hinder a sliding of tissue along the cutting edge in a positive-locking manner. 
     In medical scissors, as they are described here, a side of the first scissor blade facing away from the flank surface has especially a plurality of first surface areas, which are partial areas of a first flat or slightly curved surface, and a plurality of second surface areas, which are partial areas of a second flat or slightly curved surface, wherein each first section of the first cutting edge is present in a first surface area of the first scissor blade and each second section of the first cutting edge is present in a second surface area of the first scissor blade. 
     The side of the first scissor blade facing away from the flank surface adjoins the flank surface of the first scissor blade in the first cutting edge. When the first surface areas are partial areas of a first slightly curved surface, the radii of curvature of the first slightly curved surface are continuously greater than or much greater than the length of the first scissor blade. When the second surface areas are located in a second slightly curved surface, the radii of curvature of the second slightly curved surface are especially greater than or much greater than the length of the first scissor blade. 
     The first surface areas of the first scissor blade are especially first partial areas of the beveled surface of the first scissor blade, in which the wedge angle or the cutting angle is relatively small. The second surface areas of the first scissor blade are especially second partial areas of the beveled surface of the first scissor blade, in which the wedge angle or the cutting angle is relatively large. 
     In medical scissors, as they are described here, the flank surface, the first flat or slightly curved surface, in which the first surface areas of the first scissor blade are located, and the second flat or slightly curved surface, in which the second surface areas of the first scissor blade are located, intersect one another in the first cutting edge. 
     The first sections of the first cutting edge are then areas of the cutting edge, in which the first surface areas adjoin the flank surface, and the second sections of the first cutting edge are then areas, in which the second surface areas adjoin the flank surface. 
     In medical scissors, as they are described here, a side of the second scissor blade facing away from the flank surface has especially a plurality of first surface areas, which are partial areas of a third flat or slightly curved surface, and a plurality of second surface areas, which are partial areas of a fourth flat or slightly curved surface, wherein the first sections of the second cutting edge are each present in a first surface area of the second scissor blade and the second sections of the second cutting edge are each present in a second surface area of the second scissor blade. 
     In medical scissors, as they are described here, the flank surface, the third flat or slightly curved surface, in which the first surface areas of the second scissor blade are located, and the fourth flat or slightly curved surface, in which the second surface areas of the second scissor blade are located, intersect one another especially in the second cutting edge. 
     The first surface areas of the second scissor blade are especially first partial areas of the beveled surface of the second scissor blade, in which the wedge angle or the cutting angle is relatively small. The second surface areas of the second scissor blade are especially second partial areas of the beveled surface of the second scissor blade, in which the wedge angle or the cutting angle is relatively large. 
     A medical instrument for microinvasive applications comprises a shaft, the proximal end of which is connected or can be connected mechanically to a handling device, and medical scissors, as they are described here, which are connected or can be connected mechanically to a distal end of the shaft. 
     The shaft is especially long and thin. The length of the shaft is especially at least 10 times as large as the diameter of the shaft. The shaft may have a linear or curved, rigid or partly or completely flexible configuration. 
     Embodiments are explained in more detail below on the basis of the attached figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic view of a microinvasive medical instrument; 
         FIG. 2  is a schematic axonometric view of medical scissors; 
         FIG. 3  is another schematic axonometric view of the medical scissors from  FIG. 2 ; 
         FIG. 4  is another schematic axonometric view of a scissor blade of the medical scissors from  FIGS. 2 and 3 ; 
         FIG. 5  is another schematic axonometric view of the medical scissors from  FIGS. 2 through 4 ; 
         FIG. 6  is another schematic axonometric view of the medical scissors from  FIGS. 2 through 5 ; 
         FIG. 7  is schematic views of two sections through the scissor blades of the medical scissors from  FIGS. 2 through 6 ; 
         FIG. 8  is schematic views of two sections through another embodiment of the medical scissors; and 
         FIG. 9  is a schematic axonometric view of a scissor blade of the embodiment according to  FIG. 8 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings,  FIG. 1  shows a schematic view of a microinvasive medical instrument  10 , the proximal end of which is formed by a handling device  12  with a first grip part  13  and with a second grip part  14 . The first grip part  13  of he handling device  12  is mechanically connected to a proximal end of the shaft  16  rigidly, but especially in a non-destructive, detachable manner. A distal end  17  of the shaft  16  is connected mechanically rigidly, but especially in a non-destructive, detachable manner, to the medical scissors  20  as a tool. 
       FIG. 2  shows a schematic and enlarged axonometric view of medical scissors  20 . The medical scissors may be part of the medical instrument  10  from  FIG. 1  or part of a different medical instrument. 
     A proximal end  21  of the medical scissors  20  comprises dogs  22  for the mechanical connection in a non-destructive, detachable manner (in the form of a bayonet connection) to a distal end  17 , which is only suggested in  FIG. 2  in broken contours, of a shaft of a medical instrument, for example, of the medical instrument shown in  FIG. 1 . 
     The medical scissors  20  further have a first scissor blade  30 , the proximal end  31  of which is rigidly mechanically connected to the proximal end of the medical scissors  20  and thus rigidly even though in a non-destructive, detachable manner to the distal end  17  of the shaft of the medical instrument in the example being shown. In the example shown, the first scissor blade  30  even has a monolithic configuration with the proximal end  21  of the medical scissors  20  and the dogs  22 . 
     Between the proximal end  31  and the distal end  32  of the first scissor blade  30 , a first cutting edge  35 ,  36  extends between a flank surface  33 , which is facing away from the viewer and is hence not visible in the view in  FIG. 2 , and a multipart beveled surface  37 ,  38  which is facing the viewer. 
     The first cutting edge  35 ,  36  has alternately first sections  35  and second sections  36 . The flat bottoms of wide and flat grooves form first partial areas  37  of the beveled surfaces. These first partial areas  37  form with the flank surface  33  the first sections  35  of the first cutting edge and form with the flank surface  33  a comparatively small wedge angle. The grooves  39  are arranged approximately at right angles to the cutting edge  35 ,  36 . 
     Oblique end surfaces of webs between the grooves  39  form second partial areas  38  of the beveled surface. These second partial areas  38  form with the flank surface  33  the second sections  36  of the first cutting edge and form with the flank surface  33  a comparatively large wedge angle. The wedge angle between the flank surface  33  and the beveled surface  37 ,  38  of the first scissor blade  30  is thus markedly smaller at the first sections  35  than at the second sections  36  of the first cutting edge. 
     In the example shown, the webs between the grooves  39  have markedly rounded cross sections. In the example shown, the first partial areas  37  of the beveled surface are located together in a first plane or in a first slightly curved surface and the second partial areas  38  of the beveled surface are located together in a second plane or in a second slightly curved surface. The first surface and the second surface are slightly curved insofar as their radii of curvature are markedly greater than the length of the first scissor blade. 
     The medical scissors  20  further comprise a second scissor blade  40  with a proximal end  41 , which is pivotably mechanically connected via a joint  24  to the proximal end  21  of the medical scissors and to the first scissor blade  30 . The joint  24  defines a pivot axis at right angles to or essentially at right angles to the first cutting edge  35 ,  36  of the first scissor blade  30 . Arranged in the shaft  16  of the medical instrument  10  is a transfer device, in particular a transfer rod, not shown in  FIG. 2 , which couples the second grip part  14  of the handling device  12  (cf.  FIG. 1 ) with the second, pivotable scissor blade  40  of the medical scissors  20  such that a movement of the second grip part  14  in relation to the first grip part  13  is accompanied by a pivoting movement of the second scissor blade  40  in relation to the first scissor blade  30 . 
     The second scissor blade  40  has a configuration similar to the configuration of the first scissor blade  30 . In particular, the second scissor blade  40  has a second cutting edge  45 ,  46 , which extends from the proximal end  41  to the distal end  42  of the second scissor blade  40 . The second cutting edge  45 ,  46  is located between a flank surface  43  facing the viewer in the view shown in  FIG. 2  and a multipart beveled surface  47 ,  48 , which is facing away from the view and is hence not visible in the view shown in  FIG. 2 . 
     The first cutting edge  35 ,  36  at the first scissor blade  30  and the second cutting edge  45 ,  46  at the second scissor blade  40  touch in precisely one point of intersection  50 . This is ensured by the joint  24  as guiding device and a slightly prestressing curvature of one of the two scissor blades  30 ,  40  in the longitudinal direction thereof. This longitudinal curvature cannot be seen in  FIG. 2 . This longitudinal curvature and the prestressing resulting therefrom are especially selected to be such that the force between the cutting edges  35 ,  36 ,  45 ,  46  is approximately constant, regardless of the location of the point of intersection  50  (cf.  FIGS. 2, 3 ). 
       FIG. 3  shows another schematic axonometric view of the medical scissors  20  from  FIG. 2 . The view in  FIG. 3  differs from the view in  FIG. 2  by a different, approximately opposite viewing direction. As a result, the flank surface  33  at the first scissor blade  30  and the beveled surfaces  47 ,  48  of the second scissor blade  40  are facing the viewer and are visible in  FIG. 3 . 
     Similarly to the first cutting edge  35 ,  36  at the first scissor blade  30 , the second cutting edge  45 ,  46  at the second scissor blade  40  also has alternately first sections  45  with a small wedge angle between the flank surface  43  (cf.  FIG. 2 ) and the adjoining first partial area  47  of the beveled surface and second sections  46  with a large wedge angle between the flank surface  43  and the adjoining second partial area  48  of the beveled surface. 
     Also at the second scissor blade  40 , flat bottom surfaces of wide and flat grooves  49  form the first partial areas  47  of the beveled surface with a comparatively small wedge angle to the flank surface. End faces at the ends of webs between the grooves  49  form second partial areas  48  of the beveled surface. These second partial areas  48  of the beveled surface form with the flank surface the second sections  46  of the second cutting edge and form with the flank surface a comparatively large wedge angle. The wedge angle between the flank surface and the beveled surface  45 ,  46  of the second scissor blade  40  is thus markedly smaller at the first sections  45  than at the second sections  46  of the second cutting edge. 
       FIG. 4  shows another, enlarged axonometric view of the first scissor blade  30  of the medical scissors from  FIGS. 2 and 3 . The view in  FIG. 4  differs from the view in  FIG. 2  by the first partial areas  37  of the beveled surface that adjoin the first sections  35  of the first cutting edge and the partial areas  38  of the beveled surface that adjoin the second sections  36  of the first cutting edge being shaded differently and thus being markedly distinguishable. 
     In the example shown, all first partial areas  37  of the beveled surface are located in a first slightly curved surface and all second partial areas  38  of the beveled surface are located in a second slightly curved surface. The slight curvature of the first surface and of the second surface cannot be seen in  FIG. 4 . The curvature results especially from the already mentioned slight curvature of the first scissor blade  30  in its longitudinal direction, which curvature likewise cannot be seen in  FIG. 4 . The flank surface  33  (cf.  FIG. 3 ), the first surface, in which the first partial areas  37  of the beveled surface are located, and the second surface, in which the second partial areas  38  of the beveled surface are located, may each be curved in one or more directions or be flat, as an alternative. 
     The first cutting edge  35 ,  36  of the first scissor blade  30  is the (slightly curved or linear) line of intersection of the flank surface with the first surface, in which the first partial areas  37  of the beveled surface are located, and at the same time, with the second surface, in which the second partial areas  38  of the beveled surface are located. 
       FIG. 5  shows another schematic axonometric view of the medical scissors  20  according to  FIGS. 2 through 4 . The view in  FIG. 5  is largely similar to the view in  FIG. 2 . The view in  FIG. 5  differs from the view in  FIG. 2  by the structures on the side of the second scissor blade  40  facing away from the viewer being suggested in broken lines. 
       FIG. 6  shows another schematic axonometric view of the medical scissors  20  according to  FIGS. 2 through 5 . The view in  FIG. 6  is largely similar to the view in  FIG. 3 . The view in  FIG. 6  differs from the view in  FIG. 3  by the structures on the side of the first scissor blade  30  facing away from the viewer being suggested by broken lines. 
     It can be seen in  FIGS. 5 and 6  that the grooves  39  and hence also the first partial areas  37  of the beveled surface at the first scissor blade  30  are arranged offset in relation to the grooves  49  and hence also to the first partial areas  47  of the beveled surface at the second scissor blade  40 . A second section  46  of the second cutting edge with a large wedge angle at the second scissor blade  40  is located opposite each first section  35  of the first cutting edge with small wedge angle at the first scissor blade  30 . A second section  36  of the first cutting edge with a large wedge angle at the first scissor blade  30  is located opposite each first section  45  of the second cutting edge with a small wedge angle at the second scissor blade  40 . 
       FIG. 7  shows a schematic view of two sections through the medical scissors  20  from  FIGS. 2 through 6 . The sectional planes of  FIG. 7  are approximately parallel to the pivot axis defined by the joint  24  (cf.  FIGS. 2 through 6 ) and are approximately at right angles to the cutting edges  35 ,  36 ,  45 ,  46 . The sectional plane of  FIG. 7  contains the point of intersection  50  of the cutting edges  35 ,  36 ,  45 ,  46 . 
     The cutting plane A is the plane at right angles to the pivot axis defined by the joint  24  (cf.  FIGS. 2 through 6 ), in which the cutting edges  35 ,  36 ,  45 ,  46  are moved in relation to one another. 
     The flank surface  33  of the first scissor blade  30  forms with the cutting plane or sectional plane A the clearance angle α 1 . The flank surface  43  of the second scissor blade  43  forms with the cutting plane A the clearance angle α 2 . Broken lines suggest the positions and orientations of said first surfaces B 1 , B 2 , in which the first partial areas  37 ,  47  of the beveled surfaces of the scissor blades  30 ,  40  are located, and the positions and orientations of said second surfaces C 1 , C 2 , in which the second partial areas  38 ,  48  of the beveled surfaces of the scissor blades  30 ,  40  are located. 
     A situation or configuration of the medical scissors, in which the point of intersection  50  of the first cutting edge at the first scissor blade  30  and of the second cutting edge at the second scissor blade  40  is located between a second section  36  of the first cutting edge with a large value of the wedge angle β 1  (and hence also of the cutting angle δ 1 ) and a first section  45  of the second cutting edge with a small value of the wedge angle β 2  (and hence also of the cutting angle δ 2 ), similar to the situation shown in  FIGS. 2, 3, 5, 6 , is shown on the left-hand side in  FIG. 7 . 
     A situation or configuration of the medical scissors, in which the point of intersection  50  of the first cutting edge at the first scissor blade  30  and of the second cutting edge at the second scissor blade is located between a first section  35  of the first cutting edge with a small value of the wedge angle β 1  (and hence also of the cutting angle δ 1 ) and a second section  46  of the second cutting edge with a large value of the wedge angle β 2  (and hence also of the cutting angle δ 2 ) is shown on the right-hand side in  FIG. 7 . 
     During the closing the medical scissors, the situations shown on the left-hand side and on the right-hand side in  FIG. 7  alternate, so that one of the two wedge angles β 1 , β 2  has a small value that is usually and only briefly interrupted at the momentary point of intersection  50  of the cutting edges  35 ,  36 ,  45 ,  46 . 
       FIG. 8  shows a schematic view of two sections through an alternative embodiment of the medical scissors, which is similar in some features, properties and functions to the medical scissors shown on the basis of  FIGS. 2 through 7 . The type of view, especially the sectional planes, corresponds to that of  FIG. 7 . Below are described especially features, properties and functions of the medical scissors, in which these medical scissors differ from the medical scissors shown on the basis of  FIGS. 2 through 7 . 
     The embodiment being shown in  FIG. 8  differs from the medical scissors shown on the basis of  FIGS. 2 through 7  especially by the wedge angles β 1 , β 2  along the cutting edges  35 ,  36 ,  45 ,  46  being constant or varying only slowly. Instead of this, the widths b 1 , b 2  of the beveled surfaces  37 ,  47  vary. 
     A situation, in which the point of intersection  50  of the cutting edges is in contact with a second section  36  of the first cutting edge with a comparatively large value of the width b 1  of the beveled surface  37  of the first scissor blade  30  and with a first section  45  of the second cutting edge with a comparatively small value of the width b 2  of the beveled surface  47  at the second scissor blade  40 , b 1 &gt;b 2 , is shown on the left-hand side in  FIG. 8 . 
     A situation or configuration of the medical scissors, in which the point of intersection  50  of the cutting edges is in contact with a first section  35  of the first cutting edge with a comparatively small value of the width b 1  of the beveled surface  37  of the first scissor blade  30  and with a second section  46  of the second cutting edge with a comparatively large value of the width b 2  of the beveled surface  47  at the second scissor blade  40 , b 1  &lt;b 2 , is shown on the right-hand side in  FIG. 8 . 
       FIG. 9  shows a schematic axonometric view of the first scissor blade  30  of the medical scissors shown on the basis of  FIG. 8 . The type of view corresponds to that of  FIG. 4 . 
     It can be seen in  FIG. 9  that the beveled surface  37  of the first scissor blade  30 , which beveled surface  37  is shown in a shaded manner, is continuous, but alternately has very narrow and markedly wider areas. The second scissor blade  40  (cf.  FIG. 8 ) has an especially similar configuration. 
     The scissor blades  30 ,  40  may be structured in a manner especially similar to the medical scissors shown on the basis of  FIGS. 2 through 7  by producing a plurality of wide and flat grooves  39 . Unlike in case of the medical scissors shown on the basis of  FIGS. 2 through 7 , the grooves  39  do not touch the flank surface  33  (cf.  FIG. 8 ), however, but are arranged at a spaced location from this, so that a groove does not form the beveled surface  37  at any point. Rather, the grooves  39  only modulate the width of the beveled surface  37 . 
     Similarly to the medical scissors shown based on  FIGS. 2 through 7 , the grooves are also arranged in the medical scissors shown on the basis of  FIGS. 8, 9  in the scissor blades  30 ,  40  offset such that during the closing of the medical scissors the point of intersection  50  of the cutting edges is at any time in contact with at least one section  35 ,  45  of a cutting edge, in which the width b 1 , b 2  of the beveled surface  37 ,  47  is smaller than a predefined value. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 
     REFERENCE CHARACTERS 
     
         
           10  Medical instrument for microinvasive applications 
           12  Handling device of the medical instrument  10   
           13  First grip part of the handling device  12   
           14  Second grip part of the handling device  12   
           16  Shaft of the medical instrument  10   
           17  Distal end of the shaft  16   
           20  Medical scissors of the medical instrument  10   
           21  Proximal end of the medical scissors  20 , for the especially detachable, rigid, mechanical connection to the distal end  17  of the shaft  16   
           22  Dog at the proximal end  21  of the medical scissors, for formation of a bayonet connection between the medical scissors  20  and the distal end  17  of the shaft  16   
           24  Joint of the medical scissors  20   
           30  First, especially stationary scissor blade of the medical scissors  20   
           31  Proximal end of the first scissor blade  30   
           32  Distal end of the first scissor blade  30   
           33  Flank surface of the first scissor blade  30   
           35  First section of a first cutting edge 
           36  Second section of the first cutting edge 
           37  Beveled surface of the first scissor blade  30  or first partial area of the beveled surface at the first section  35  of the first cutting edge 
           38  Second partial area of the beveled surface of the first scissor blade  30  at the second section  36  of the first cutting edge 
           39  Groove on the side of the first scissor blade  30  facing away from the flank surface  33   
           40  Second, especially pivotable scissor blade of the medical scissors  20   
           41  Proximal end of the second scissor blade  40   
           42  Distal end of the second scissor blade  40   
           43  Flank surface of the second scissor blade  40   
           45  First section of a second cutting edge 
           46  Second section of the second cutting edge 
           47  Beveled surface of the second scissor blade  40  or first partial area of the beveled surface at the first section  45  of the second cutting edge 
           48  Second partial area of the beveled surface of the second scissor blade  40  at the second section  46  of the second cutting edge 
           49  Groove on the side of the second scissor blade  40  facing away from the flank surface  43   
           50  Point of intersection of the first cutting edge  35 ,  36  and of the second cutting edge  45 ,  46   
         A Cutting plane or cutting surface 
         B 1  First flat or slightly curved surface, in which the first partial areas  37  of the beveled surface of the first scissor blade  30  are located 
         B 2  First flat or slightly curved surface, in which the first partial areas  37  of the beveled surface of the first scissor blade  30  are located 
         C 1  Second flat or slightly curved surface, in which the second partial areas  38  of the beveled surface of the first scissor blade  30  are located 
         C 2  Second flat or slightly curved surface, in which the second partial areas  48  of the beveled surface of the second scissor blade  40  are located 
         α 1  Clearance angle of the flank surface  33  at the first scissor blade  30   
         β 1  Wedge angle between the flank surface  33  and the beveled surface at the first scissor blade  30   
         δ 1  Cutting angle at the first scissor blade  30 , δ 1  =a l  + 13   1    
         b 1  Width of the beveled surface  37 ,  38  of the first scissor blade 
         α 2  Clearance angle of the flank surface  43  at the second scissor blade  40   
         β 2  Wedge angle between the flank surface  43  and the beveled surface at the second scissor blade  40   
         δ 2  Cutting angle at the second scissor blade  40 , δ 2  =a 2  +β 2    
         b 2  Width of the beveled surface  47 ,  48  of the second scissor blade