Abstract:
A rotary cutter head for a surgical stapling instrument includes a staple cartridge, an annular cutter, a staple-pushing seat and a staple chamber. The staple-pushing seat and the annular cutter are connected by a bearing structure and provided with guide projections. The inner wall of the staple cartridge or the outboard of the expand-stopping tube is integral injection molded with a metal cylinder insert, on which is provided with a forward helix track and a backward track mutually independent and communicated with each other. The guide projections are mated with the two guide tracks and guiding the annular cutter to move along a helical path.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a surgical stapling head assembly, more particularly, to a rotary cutter for surgical stapling head assembly in the technical field of medical instrument. 
     BACKGROUND OF THE INVENTION 
     A surgical stapling head assembly is the medical instrument used for performing a circular anastomosis stapling operation, which can be operated easily and the surgery operation time can be effectively reduced. The surgical stapling head assembly has distinct advantages over the manual suture, which is approved by more and more doctors and patients. A circular stapling instrument is used for performing a circular anastomosis stapling operation, unwanted tissues are cut while suturing, however, the annular cutter of prior art works in way of straight forward and straight backward thereby the doctor has to exert large force when doing the operation so that tissues are able to be cut by impulsive force, sometimes the tissues may not be cut completely and the uncut tissues will be stretched to break by the force from the stapling instrument while retreating, which brings tensile damages to anastomosis ring and the result is serious. To overcome the defects as mentioned above, rotary cutting instrument is invented by changing the straight cutting of prior art into rotary cutting, the cutting effects are greatly improved and the doctors can exert much less force when doing operations. 
     However, tracks for rotary cutting have comparatively monotonous function, the same helix tracks function not only as forward tracks but also function as backward tracks, the annular cutter has to rotate to retreat and it suffers comparatively large resistance because the backward journey is comparatively long. Furthermore, the rotary cutter of prior art is enabled by disposing ball device between the annular cutter and staple driver, the rotary cutter is connected with the staple driver by means of two slender catches, when the annular cutter is pressed tightly with the staple driver by the catches, the annular cutter will be subject to large friction resistance; when the annular cutter is pressed loosely with the staple driver by the catches, due to influences from self gravity and other factors, the annular cutter may deviate from central axis slightly when cutting tissues, therefore, the shape of the cut is not a full circle, there is a potential danger of cutter being stuck and unmovable when the annular cutter deviates too much from the central axis, which may affect the implementation of the surgery operations. 
     SUMMARY OF THE INVENTION 
     The invention is aimed at solving the problems of prior art by providing a surgical stapling head assembly with a rotary cutter. 
     The object of the present invention is achieved by the following technical scheme: a surgical stapling head assembly with a rotary cutter comprises a casing, an annular cutter, a staple driver and a staple holder, the casing is a tubular body comprising a stepped inner cavity and an anti-expansion tube, a plurality of staple pushers are arranged annularly and alternately in two rows, and are disposed between the anti-expansion tube and an inner wall of the casing, the staple driver is disposed at a proximal end of the staple pushers, the staple holder for receiving one or more surgical staples is disposed at a distal end of the staple driver, the annular cutter is disposed in the space formed by an inner wall of the staple holder, wherein said annular cutter is connected with the staple driver by a bearing structure, the bearing structure at least comprises a bearing inner ring and a bearing outer ring, guiding projections are disposed on said annular cutter or the bearing inner ring or the bearing outer ring, a metal cylinder member with guiding tracks is disposed inside the casing, said guiding projections engage with the guiding tracks so as to guide the annular cutter to move along a helical path. 
     Preferably, in the surgical stapling head assembly with a rotary cutter, said metal cylinder member is molded on an outer wall of the anti-expansion tube. or on the inner wall of the casing; corresponding to these two ways, said guiding projections can be disposed at the proper location of the annular cutter or the bearing inner ring or the bearing outer ring so as to engage with the guiding track of the metal cylinder member. 
     Preferably, in the surgical stapling head assembly with a rotary cutter, said guiding track comprises a helix forward track and a backward track, the helix forward track and the backward track are independent from each other but communicated with each other to form at least one back and forth journey. more preferably, said backward track comprises a section of straight line track and a section of arc track, the angle between the two edges of the straight line track and the axis of the metal cylinder member is from 0° to 30°. 
     Preferably, in the surgical stapling head assembly with a rotary cutter, said bearing structure comprises the bearing inner ring, the bearing outer ring and a transmission part, the bearing inner ring is connected with the bearing outer ring by the transmission part, the annular cutter is fixed on the bearing inner ring or the bearing outer ring; more preferably, bearing inner ring and said annular cutter can be fixed by rivets through the rivets holes thereof; or bearing outer ring and the annular cutter can be fixed by rivets through the rivets holes thereof. 
     The present invention has following advantages: by employing bearing structure, the annular cutter can be connected tight with the staple driver by mechanical structure, the annular cutter will not deviate from the central axis when the annular cutter moves along a helical path, the section of tissues cut in surgery operations are in shape of full circle so as to avoid the potential danger of the cutter being stuck and unmovable, the surgery operations is ensured successful. Moreover, during the operation process, the annular cutter rotatingly forwards along the helix track when going forward, and backwards to the inner cavity of the staple holder in way of straight line or part of straight line under the guide from the backward track, the operation of forwarding and retreating which is previously realized by one helix track is divided into two parts, the helix track undertakes the forward operation and the backward track undertakes the backward operation, the forward helix track is communicated with the backward track to form at least one back and forth journey, which shortens the backward journey and reduces the resistance subjected by the annular cutter when retreating, the time consumed for retreating is reduced as well, therefore, the surgery operations can be implemented more easily with more safety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments, with references to the appended drawings, which are intended for illustrative but not limitative purposes. While the embodiments are provided as typical technical solutions of the present invention, various modifications, alternative constructions and equivalents may be employed without departing from the true spirit and scope of the present invention. 
         FIG. 1  is a schematic view showing the structure of the annular cutter of the present invention; 
         FIG. 2  is a schematic view showing the structure of the metal cylinder member of the present invention; 
         FIG. 3  is a schematic view of one bearing structure of the present invention; 
         FIG. 4  is a schematic view showing the partial assembly of the present invention; 
         FIG. 5  is a schematic view showing the structure of the casing of the present invention; 
         FIG. 6  is a schematic view of another bearing structure of the present invention; 
         FIG. 7  is a schematic view of the third bearing structure of the present invention; 
         FIG. 8  is a front view of the bearing structure of the present invention; 
         FIG. 9  is a bottom view of the bearing structure of the present invention. in which: 
       
         
           
                 
                 
                 
                 
               
             
                 
                     
                 
                 
                   No. 
                   Denotes 
                   No. 
                   Denotes 
                 
                 
                     
                 
               
               
                 
                   101 
                   casing 
                   102 
                   staple driver 
                 
                 
                   103 
                   annular cutter 
                   104 
                   anti-expansion tube 
                 
                 
                   105 
                   metal cylinder member 
                   106 
                   forward helix track 
                 
                 
                   107 
                   straight line backward track 
                   108 
                   arc backward track 
                 
                 
                   109 
                   bearing structure 
                   110 
                   bearing inner ring 
                 
                 
                   111 
                   bearing outer ring 
                   112 
                   ball 
                 
                 
                   113 
                   washer 
                   114 
                   rivet hole 
                 
                 
                   115a 
                   guiding projection 
                   115b 
                   guiding projection 
                 
                 
                   115c 
                   guiding projection 
                 
                 
                     
                 
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A surgical stapling head assembly with a rotary cutter as illustrated from  FIGS. 1 to 5  comprises a casing  101 , a staple driver  102 , an annular cutter  103  and a staple holder, the casing  101  is a tubular body with a stepped inner cavity and an anti-expansion tube  104  is disposed therein, a plurality of staple pushers are arranged annularly and alternately in two rows, and are disposed between the anti-expansion tube  104  and the inner wall of the casing  101 , the staple driver  102  is disposed at the proximal end of the staple pushers, the staple holder is disposed at the distal end of the staple pushers, the annular cutter  103  is disposed in the space formed by the inner wall of the staple holder. 
     A metal cylinder member  105  is molded on the outer wall of the anti-expansion tube  104 , of which the structure is illustrated in  FIG. 2 , a forward helix track  106  and a backward track are distributed on the outer wall of the metal cylinder member  105 , a guiding structure is disposed on the annular cutter  103  and the guiding structure is inserted via the entrance of the forward helix track  106  so that the annular cutter  103  is rotatably connected with the metal cylinder member  105 , the bottom of the annular cutter  103  is fixed on the staple driver  102  by the bearing structure  109 , a washer  113  is disposed between the bearing structure  109  and the staple driver  102  as illustrated in  FIG. 4 . 
     Furthermore, said guiding structure is in the form of guiding projections  115   a , guiding projections  115   a  are disposed on the inner wall of the bottom of the annular cutter  103  as illustrated in  FIG. 1 . At the same time, said forward helix track  106  is communicated with the backward track to form at least one back and forth journey, and the backward track comprises a section of straight line track  107  and a section of arc track  108 , the angle between the two edges of the straight line backward track  107  and the axis of the metal cylinder member  105  is from 0° to 30°, preferably, from 6° to 9°, as illustrated in  FIG. 2 . Therefore, the latter forward helix track  106  and the former backward track have a natural transition which avoids backtrack to the first journey when going to the next cycling journey. 
     The assembling process of the surgical stapling head assembly with a rotary cutter is as follows: the metal cylinder member  105  is injection molded and nested on the outer wall of the anti-expansion tube  104 , the bearing structure  109  is injection molded and fixed inside the staple driver  102 , the staple driver and staple pushers are made integrally, the staple driver  102  is disposed inside the casing  101 , by guiding projections  115   a  disposed on the inner wall of the bottom of the annular cutter  103 , the annular cutter  103  is inserted via the entrance of the forward helix track  106  of the metal cylinder member  105  so that the annular cutter  103  is rotatably engaged with the metal cylinder member  105 , the annular cutter  103  is able to perform rotary movement by the guide from the helix track, then the annular cutter  103  is fixed with the bearing structure  109  and the staple holder is placed in the casing  101  so that the assembling of rotary cutter is completed. 
     The instrument is triggered when using, the annular cutter  103  is pushed by the staple driver  102  to go up along a helical path under the co-operating between the guiding projection  115   a  and the forward helix track  106 ; and then the guiding projection  115   a  retreats in way of straight line along the backward track of the metal cylinder member  105 , thus, a back and forth journey is completed. Because the backward track comprises a section of straight line track  107  and a section of arc track  108 , the latter forward helix track  106  and the former backward track are able to have a natural transition so that the annular cutter  103  will not backtrack to the last journey when going to the next cycling journey, and the regular forward path of the annular cutter  103  is ensured. 
     Second Embodiment 
     A surgical stapling head assembly with a rotary cutter as illustrated from  FIGS. 1 to 5 , of which the structure is similar to that in the first embodiment. The staple driver  102  is internal injection molded and fixed with the bearing structure  109 , the bearing structure  109  comprises the bearing inner ring  110  and the bearing outer ring  111 , the ball  112  is disposed between the bearing inner ring  110  and the bearing outer ring  111  as a transmission part. When the friction between the bearing inner ring  110  and the bearing outer ring  111  is not large, the bearing inner ring  110  is able to be connected with the bearing outer ring  111  by means of friction without the ball  112  or other transmission parts disposed between the bearing inner ring  110  and the bearing outer ring  111 . 
     As another configuration of the guiding structure, guiding projections  115   b  are disposed inside the bearing inner ring  110  as the guiding structure, as illustrated in  FIG. 3 , the guiding projection  115   b  engages with the track of the metal cylinder member  105  which is molded with the outside of the anti-expansion tube  104 . When assembling, the guiding projection  115   b  of the bearing structure  109  is inserted via the entrance of the forward helix track  106  of the metal cylinder member  105  so that the staple driver  102  is disposed inside the casing  101 , the annular cutter  103  is placed in the casing  101 , the annular cutter  103  is fixed with the bearing inner ring  110  of the bearing structure  109  as illustrated in  FIG. 4 . 
     When the rotary cutter is assembled and connected with other parts of the surgical stapling head assembly, the instrument preparation work before surgery operation is done. In consideration of the whole surgical stapling head assembly, the working process of the rotary cutter during surgery operation is as follows: the surgery operator binds up the patient body tissues, and then the stapling instrument is adjusted to the most suitable distance for stapling, the trigger is tightly held for implementing triggering, the force is transformed by the transmission part inside the instrument to the push force that pushing the staple driver  102  to move forward, staples in the staple holder are pushed by the staple pushers arranged on the staple driver  102  into the tissues and shaped; at the same time, the guiding projection  115   b  goes forward along the forward helix track  106  of the metal cylinder member  105  so as to enable the annular cutter  103  to rotatably cut the tissues and the unwanted tissues will be cut by the cutting face of the cutter. When the triggering is finished, the guiding projection  115   b  goes to the backward track by the restoring and pulling force of the staple driver  102 , the annular cutter  103  retreats to the inner cavity of the staple holder under the guide from the guiding projection  115   b , thus one cutting journey is completed. Because the staple driver  102  is connected with the annular cutter  103  by the bearing structure  19 , by use of the ball  112 , the annular cutter  103  will not be subject to much friction when rotating. Furthermore, during the whole process of cutting, the annular cutter  103  is tightly connected with the staple driver  102 , therefore, the annular cutter  103  will not shake or deviate from the central axis, the tissues will be cut in shape of a full circle, which avoids the potential danger of the cutter being stuck and unmovable. 
     On the other hand, by employing the surgical stapling head assembly with a rotary cutter of the present invention, the annular cutter  103  and the staple driver  102  go forward along the forward helix track  106  of the metal cylinder member  105 , and retreat under the guide from the backward track, thereby the previous single track is divided into two, that is, the helix forward track  106  and the backward track, the helix forward track  106  and the backward track are independent but communicated to form a back and forth journey, the length of the whole metal cylinder member  105  at least comprises one back and forth journey. Furthermore, the backward track can be disposed into two sections, that is, a section of straight line track  107  and a section of arc track  108 , as illustrated in  FIG. 2 , by disposing the arc track  108 , the next forward helix track  106  will have a natural transition with the last backward track, which avoids backtrack of the annular cutter  103  to the first journey when going to the next cycling journey, the regular forward path of the annular cutter  103  is ensured, thereby the instrument can be operated more safely and reliable. 
     Third Embodiment 
     A surgical stapling head assembly with a rotary cutter as illustrated from  FIGS. 1 to 9 , of which the structure is similar to that in the first embodiment and second embodiment, the differences are that: the metal cylinder member  105  configured as illustrated in  FIG. 2  is molded on the inner wall of the casing  101  (not shown in figures), guiding projections  115   c  are disposed on the bearing outer ring  111  or the outside of the bearing inner ring  110 , as illustrated in  FIGS. 6 and 7 , alternatively, guiding projections  115   c  are disposed on the outside of the annular cutter  103  (not shown in figures), the guiding projections are set to engage with the helix forward track and backward track of the metal cylinder member  105 . 
     For sake of easy combining and connecting, rivet holes  114  are disposed on said bearing inner ring  110  and connecting holes are disposed on the annular cutter  103  so that the bearing inner ring  110  and the annular cutter  103  can be fixed through rivets thereof. Of course, the involved connection can be by way of helix, shaping, pin, bonding, welding or clamping, etc. If the bearing structure  109  employs the similar structure of  FIG. 8  or  FIG. 9 , the bearing outer ring  111  is in a structure of half enclosed, then rivet holes  114  can be disposed on the bearing outer ring  111 . 
     When processing and assembling, the bearing structure  109  is fixedly connected with the annular cutter  103  as an assembled component at first, the connection can be by way of rivet, bonding or helix, etc. Then the assembled component is injection molded inside the staple driver  102  so as to make the bearing outer ring  111  to be integrally connected with the staple driver  102 , the washer  113  can be disposed between the bearing structure  109  and the staple driver  102  when molding. In order to adapt to commonly used manufacture technique, the bearing outer ring  111  and the staple driver  102  can alternatively be connected in way of bonding or helix. When the above-mentioned works are finished, the assembly including the staple driver  102 , the bearing structure  109  and the annular cutter  103  can be placed and mounted inside the casing  101 , along the helix track by inserting the guiding projection  115   c  at the helix track entrance of the metal cylinder member  105  of the casing  101 . When the assembling is done, the operation process is similar to that in the first embodiment and the second embodiment.