Abstract:
A surgical punching instrument with a fixed handle ( 21 ) is attached to a tubular guide part ( 20 ). An actuating lever ( 23 ) is mounted on the fixed handle ( 21 ) in a pivotingly movable manner and is in connection with a plunger ( 27 ) via a short lever arm ( 24 ). This plunger is in turn connected to a punching slide ( 1 ) and is mounted for actuating same against the action of a compression spring in an axially movable manner in a rearward mounting part ( 31 ) of a punching bar ( 2 ), which is guided rotatably by an at least partially cylindrical guide section ( 33, 34 ) and lockably in different rotated positions in the guide part ( 20 ). The punching bar is in contact in the guide part ( 20 ) with an axial stop acting in the direction of actuation with a ring shoulder ( 35 ) and it is locked in an axially detachable manner. The axial stop, with which the ring shoulder ( 35 ) is in contact, comprises a spring-loaded locking lever ( 37 ), which passes through a guide slot ( 45 ) of the guide part ( 20 ) radially into a cylindrical cavity ( 20 ′) of the guide part ( 20 ), in which the guide section ( 33, 34 ) of the mounting part ( 31 ) of the punching bar ( 2 ) is guided.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application DE 20 2004 015 990.2 filed Oct. 14, 2004, the entire contents of which are incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention pertains to a surgical punching instrument with a fixed handle attached to a tubular guide part and with an actuating lever, which is mounted thereon in a pivotingly movable manner and which is in connection via a short lever arm with a plunger, which is in turn connected to a punching slide and is mounted for actuating same against the action of a compression spring in an axially movable manner in a rearward mounting part of a punching bar, which is guided rotatably by means of an at least partially cylindrical guide section and lockably in different rotated positions in the guide part, the punching bar being in contact in the guide part with an axial stop acting in the direction of actuation with a ring shoulder and being locked in an axially detachable manner. 
   BACKGROUND OF THE INVENTION 
   A decomposable laminectomy punch, in which the two punch shafts, namely a punching bar and a punching slide, comprise straight, rod-shaped bodies each, which are mutually guided at one another, in the customary manner, by guide elements having a T-shaped profile that engage one another in a positive-locking manner, is known from an inhouse publication of the applicant. The rear end of the punching bar is provided here with a cylindrical mounting part, which has a larger diameter and has on its front side an annular stop shoulder, with which it is in contact with an axial stop, which is designed as a ring shoulder and in which the rearward ends of both punch shafts are mounted. 
   The movable punching slide is connected in an articulated manner to a pin-like plunger, which passes through a central axial hole of the guide part. At its rear end, this plunger has a pushing head, whose diameter is expanded and at which the short lever arm of the actuating lever for actuating the punching slide acts against the action of a restoring spring designed as a compression coil spring arranged on the plunger when the actuating lever is actuated. Locking depressions for a ball notch, which are arranged in a uniformly distributed manner, are provided on the circumference of the cylindrical mounting part. The two punch shafts can be rotated together in the tubular guide part and locked in a locking manner in different angular positions by means of this ball notch. 
   To make it possible to remove the two punch shafts together from the guide part, e.g., for cleaning purposes, it is necessary to remove the short lever arm of the actuating lever from the path of motion of the plunger. The actuating lever is mounted for this purpose with the short lever arm radially displaceably in relation to its bearing axis and with a special, axially stepped bearing journal, which can in turn be displaced against spring pressure in a bearing bore. The two punch shafts can then be pulled out of the guide part on the rear side together with the plunger and the restoring spring. These two parts can then be separated from one another by releasing the guide elements profiled in a T-shaped manner by correspondingly displacing the punching slide in the longitudinal direction relative to the punching bar. 
   This type of decomposability can be applied in case of straight punch shafts only, which can be pushed over their entire length through the tubular guide part. This type of decomposability cannot be used in case of punch shafts bent at right angles. 
   Another surgical bar shaft instrument, in which both grip parts are fixed together to a tubular guide part in an articulated manner and can be locked, is also known from DE 198 52 682 C2. By releasing the bolted connection, the two lever arms and especially the short lever arm of the actuating lever can be pivoted out of the path of movement of the two punch shafts, so that these can be pulled out of the guide part on the rear side. 
   This type of decomposability cannot be used in the case of punch shafts having a bent offset portion, which can be offset at right angles, either. 
   SUMMARY OF THE INVENTION 
   The basic object of the present invention is to provide a surgical punching instrument of the type mentioned in the introduction, but with instrument shafts that have bent offset portions, which can be bent at right angles, in which the instrument shafts comprising a punching slide and a punching bar each can be inserted into the guide part and can be removed therefrom in a simple manner, e.g., for cleaning purposes. 
   This object is accomplished according to the present invention by the axial stop, with which the ring shoulder is in contact, comprises a spring-loaded locking lever, which protrudes through a guide slot of the guide part radially into a cylindrical cavity of the guide part, in which the guide section of the mounting part of the punching bar is guided. 
   With the design according to the present invention, punch shafts bent at right angles can also be mounted snugly in the guide part, rotated, locked in different angular positions and removed in a simple manner. In addition, the design according to the present invention has the considerable advantage that the short lever arm of the actuating lever does not need to be mounted in a radially movable manner and does not need to be able to be removed from the path of motion of the plunger in order to make it possible to remove the punch shafts from the guide part. 
   Unlike in the prior-art instruments, the punch shafts are inserted into the tubular guide part and removed from the tubular guide part from the proximal side, i.e., from the front. 
   Another advantage of the design according to the present invention is that it can be readily embodied with straight punch shafts. 
   Instead of the ball notch means provided in the case of the prior-art instruments, the design according to another aspect of the present invention has the considerable advantage that reliable securing of the punch shafts against rotation can be achieved with it relative to the tubular guide part and the handles, but this securing against rotation can also be easily released, by a corresponding actuation of the locking lever, in order to disengage the latter from the notches of the lever. 
   The embodiment of the punch shafts, which is bent at right angles and is provided according to another aspect of the invention, is especially advantageous for the surgeon using the instrument, because he can readily recognize the particular angular position in relation to the handles at any time. This is not possible so easily in case of straight punch shafts. 
   Due to the embodiment according to another aspect of the invention, it is ensured that the engagement between the locking lever and the locking notches of the mounting part of the punching bar is guaranteed even in the inoperative position of the actuating lever, so that an independent rotation of the punch shafts in the guide part is prevented from occurring with certainty. 
   Due to the embodiment according to another aspect of the invention, it is also ensured with simple means that the two punch shafts do not separate from one another independently when they are removed from the guide part, and the embodiment according to claim  6  offers a simple possibility of removing the punching slide from the punching bar and to reattach it to same. 
   Another advantageous embodiment is provided according to another aspect of the invention. Due to this embodiment, the plunger can be separated from the punching slide in a simple manner, and it is also possible, to mount and remove the compression spring in a simple manner. 
   Good guiding of even the distal end section of the punching slide on the punching bar can be achieved with the embodiment according to another aspect of the invention. 
   Due to the embodiment according to another aspect of the invention, the two punch shafts, which are displaceably connected to one another, receive a good guiding within the tubular guide part with the cylindrical guide hole thereof, whose diameter is coordinated with the guide sections of the bearing part. 
   An exemplary embodiment of the present invention will be explained in greater detail below on the basis of the drawings. 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 side view of a surgical punching instrument; 
       FIG. 2  is an enlarged sectional view of the tubular guide part of the punching instrument; 
       FIG. 2   a  is a sectional view of the empty guide part; 
       FIG. 3  is a section III-III from  FIG. 2 ; 
       FIG. 4  is the top view of the locking lever as an individual part; 
       FIG. 5  is the side view of the straight, front section of the punching slide; 
       FIG. 6  is a section VI-VI from  FIG. 5 ; 
       FIG. 7  is a top view of the front section of the punching bar; 
       FIG. 8  is a section VIII-VIII from  FIG. 7 ; 
       FIG. 9  is a side view of the two punch shafts with the plunger and the restoring spring; 
       FIG. 10  is a side view of the two punching slides and the plunger with the restoring spring in a separate view, where the punching bars are shown in a partially cut-away view; 
       FIG. 11  is an enlarged view of the mounting part of the punching bar; 
       FIG. 12  is a sectional view XII-XII from  FIG. 11 ; 
       FIG. 13  is an enlarged side view of the rear end section of the punching bar; 
       FIG. 14  is a front view XIV from  FIG. 13 ; and 
       FIG. 15  is an enlarged detail XV from  FIG. 9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the drawings in particular, The instrument shown in the drawings is a laminectomy punch with two punch shafts, namely, a punching slide  1  and a punching bar  2 , both of which are uniformly bent at right angles and thus have sections  3  and  4 , which extend obliquely in relation to the straight shaft sections  1 ′ and  2 ′ and whose rear sections  6  and  7  lie in one another in a slidingly displaceable manner. 
   It is achieved due to the two oblique sections  3  and  4  of the punching slide  1  and of the punching bar  2  that the two straight sections  1 ′ and  2 ′ of these punch shafts extend radially offset from the axis  5  of the mounting part  20  but in parallel thereto. 
   While the obliquely extending sections  3  and  4  may have any desired cross-sectional shape, the sections  1 ′ and  2 ′ as well as  6  and  7 , which lie one on top of another, are provided with flat sliding surfaces  8  and  9  or guiding surfaces  10  and  11  on the sides facing each other ( FIG. 10 ). In the area of the sliding surface  8 , the punching slide  1  is provided with a guide bead  12  profiled in a T-shaped pattern at its front end and with a guide pin  13  profiled in a T-shaped pattern in the middle area. To receive these guide elements  12  and  13 , the punching bar  2  is provided with two guide grooves  14  and  15 , which are located at correspondingly spaced locations from one another and have a T-shaped profile each. While the guide groove  14  is joined by a broader insertion groove  16  for inserting the guide bead  12 , the guide groove  15  is provided at its rear end with a hole  17  for inserting the guide pin  13 . 
   The front end of the punching bar  2  is provided with an upwardly directed punching blade  18 , which is designed as an abutment for the punching edge  19  of the punching slide  1 . 
   The punching slide  1  is displaceable on the punching bar  2  by the punching stroke H by actuating the actuating lever  23  via the short lever arm  24 . 
   The two punch shafts  1  and  2  are mounted, in the assembled state, together in a tubular guide part  20  in the manner to be described in greater detail below. 
   A stationary handle  21 , on which an actuating lever  23  is mounted in a pivotingly movable manner by means of a bearing journal  22 , is attached to the guide part  20 . This actuating lever  23  has a short lever arm  24  with a rounded end section  25 , which is in contact with the pressing surface  26  of a plunger  27 . The lever arm  24  is mounted in a slot-like recess  28  of the handle  21 , and it passes through a slot  29  of the tubular guide part  20 . The tubular guide part  20  is arranged snugly on a horizontal bearing shaft  30  of the handle  21  and is welded or soldered to same. 
   As can be recognized from  FIGS. 2 and 3 , the guide part  20  comprises a cylindrical tube with a likewise cylindrical cavity  20 ′ ( FIG. 2   a ). The punch shafts  1  and  2  lying on one another with their flat sliding and guiding surfaces  9  and  11  as well as  8  and  10  are mounted in this guide part  20  in the assembled state. 
   To achieve good, possibly clearance-free guiding for the rear section  7  of the punching bar  2  in the guide part  20 , this rear section  7  is provided with a cylindrical mounting part  31 . This mounting part  31  has a peripheral, partly conical incision  32 , by which the mounting part  31  is divided into two cylindrical guide sections  33  and  34 . A radial ring shoulder  35 , in which a total of eight locking notches  36  are milled, which are arranged in a uniformly distributed manner in the circumferential direction, is formed by this incision  32 . 
   A locking lever  37  is provided as an axial stop acting in the direction of the arrow  38  for this ring shoulder  35  with the locking notches  36  thereof. By means of a bearing journal  39 , the locking lever  37  is mounted pivotably in a recess  41  of the bearing shaft  30  against the action of a leaf spring  40 . It has an actuating arm  42 , which projects from the recess  41  of the mounting shaft  30  and is located under the front section of the guide part  20 . 
   A second active locking arm  43  of the locking lever  37  engages one of the locking notches  36  of the mounting part  31  with a locking catch  44  adapted to the shape of the locking notches  36  under the action of the spring  40 . 
   By correspondingly actuating the locking lever  37 , the locking arm  43 , which protrudes into the cavity  20 ′ of the tubular guide part  20  through a slot  45  of the tubular guide part  20 , can be disengaged from the ring shoulder  35  and the locking notch  36 , so that the punching bar  2  can be pulled out of the guide part  20  in the direction of arrow  38 . 
   As is apparent most clearly from  FIG. 3 , the rear, i.e., distal end  6  of the punching slide  1  has the cross-sectional shape of a semicylinder, which protrudes into a central longitudinal groove  47  having a U-shaped profile through a semicylindrical attachment  46  of a smaller diameter and creates the possibility of providing a central threaded hole  48  in the end section  6 . This threaded hole  48  is used to axially fasten the plunger  27  to the punching slide  1 . This plunger  27  is provided for this purpose, at the front end of its cylindrical shaft  27 ′, with a threaded pin  49 , which has a somewhat smaller diameter than the shaft  27 ′. A compression coil spring  50  acting as a restoring spring is arranged on the shaft  27 ′. To receive the front part of the shaft  27 ′ in a guiding and axially movable manner, the mounting part  31  of the punching bar  2  is provided with a central through hole  51 , which continues in the U-shaped, i.e., semicylindrical longitudinal groove  47 . 
   As is apparent from  FIG. 2 , the compression coil spring  50  is in contact with the rear-side face  52  of the mounting part  31 . With the other end, it is supported at a head part  53  of the plunger  27 , whose rear-side face  26  forms the pressing surface for the short lever arm  24  of the actuating lever  23 . It can be recognized from the drawing that the shaft  27 ′ of the plunger  27  has a smaller diameter than the pressing head  53 , whose diameter is adapted to the internal diameter of the guide part  20 . The shaft  27 ′ of the plunger  27  passes through the compression coil spring  50  and the central axial hole  51  of the mounting part  31 . The circumferential surface of the pressing head  53  is knurled to ensure that the plunger  27  can be screwed easily into the rear end  6  of the punching slide and can be easily detached therefrom. 
   To guarantee clearance-free mounting of the mounting part  31  in the axial direction in the guide part  20 , the axial distance a between the axial stop formed by the locking catch  44  and the short lever arm  24  of the actuating lever  23  should be selected to be at most equal to the distance a 1  between the ring shoulder  35  and the rear-side face or pressing surface  26  of the plunger  27  that is in contact with the short lever arm  24 . This can be easily accomplished by selecting the length b of the plunger  27  correspondingly. 
   If this distance a is selected to be somewhat smaller than the distance a 1 , a certain axial pressure is to be applied against the short lever arm  24  of the actuating lever when the mounting part  31  is inserted into and locked in the guide part  20  in order to enable the locking lever  37  to jump into engagement with the ring shoulder  35  or one of the locking notches  36 . 
   As can be best recognized from  FIG. 15 , there is an axial gap  57  of the width s between the rear-side face  55  and the face  56  of the guide section  33 , which latter face is located opposite the face  55 , when the plunger  27  is screwed into the rear end section  6  of the punching slide  1 . This gap  57  develops due to the fact that in the mounted state, the face  55  is in contact with two diametrically opposed stop faces  58  ( FIG. 12 ), which project over the guide surface  11  of the rear section  7  of the punching bar  2  by the height h of about 0.5 mm to 1.5 mm. It is thus also ensured that the guide bead  12  and the guide pin  13  cannot leave the guide grooves  14  and  15  as long as the gap  57  exists. 
   To guarantee this, the distances s 1  and s 2 , which the guide bead  12  and the guide pin  13  have from the rear face  55  of the punching slide, are smaller than the distances s 3  and s 4  by the dimension s of the gap  57 , s 3  being the distance between the front guide groove  14  and the front face  56  of the guide section  33  and s 4  being the distance between the hole  17  and the face  56 . The dimension s may be between about 0.5 mm and 3 mm. 
   To make it possible to detach the punching slide  1  from the punching bar  2 , it is necessary to screw the plunger  27  out of the threaded hole  46  of the rear section  6  of the punching slide  1 . Because of the elasticity of the material, it is possible to raise the rear section  6  over the height h of the stop faces  58  in order to move the punching bar  2  farther against the face  56  in order to release the engagement between the guide bead  12  and the guide pin  13 , on the one hand, and the guide grooves  14  and  15 , on the other hand. 
   To insert the two punch shafts, which are connected to one another, i.e., the punching slide  1  and the punching bar  2 , with the plunger  27  screwed in and with the compression coil spring  50  from the front side into the hole  20 ′ of the guide part  20 , it is only necessary to insert this [the guide part] against the direction of the arrow  38  and to press it against the short lever arm  24  until the locking catch  44  of the locking lever  37  is audibly snapped into one of the index notches  36 . The instrument is immediately ready for use thereafter. 
   If another angular position of the punch shafts  1  and  2  in relation to the handles  21  and  23  is to be reached, the locking lever  20  is to be actuated correspondingly in order to release the engagement of its locking catch  44  with one of the index notches. After the two punch shafts  1  and  2  have then been rotated into the desired angular position, the engagement with the locking catch  44  is again established by repeatedly pressing the mounting part  31  against the short lever arm  24 . The mounting part  31  can also be released in the same manner for removal from the guide part  20 . 
   However, it is also possible to disengage the locking catch  44  of the locking lever  37  from the locking notches  36  by moving the mounting part  31  against the spring action, i.e., against arrow  38 . 
   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.