Abstract:
A method for producing an endoscope that includes an endoscope head and an optic tube, including the steps of providing the endoscope head, providing the optic tube, and pushing a proximal end area of the optic tube into a distal end area of the endoscope head. The distal end area of the endoscope head is press-fitted with the proximal end area of the optic tube.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of currently pending U.S. patent application Ser. No. 11/770,855 filed Jun. 29, 2007, which claims priority of German Patent Application No. 10 2006 030 521.3 filed Jul. 1, 2006. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a method for producing an endoscope, the endoscope comprising an endoscope head and an optic tube. Such a method, and an endoscope produced by this method, are generally known. 
       BACKGROUND 
       [0003]    Endoscopes are mainly used in minimally invasive surgery in order to examine body cavities or hollow organs. For this purpose, an endoscope comprises an endoscope head, on whose distal end an elongate endoscope shaft is mounted that comprises an optic tube. Connector pieces, for an external lighting source and irrigation/suction lines, and an eyepiece can be provided on the endoscope head. By way of the connector piece for the lighting source, light is coupled into an optical waveguide system extending through the endoscope head and the endoscope shaft and is guided to the distal end of the endoscope shaft. The endoscope also comprises an optics system for imaging purposes. The imaging optics can be made from optical fibres, rod lenses or the like, but can also include an image sensor with electrical signal transmission. 
         [0004]    Depending on the material of the endoscope shaft, endoscopes can be made rigid or flexible. A rigid endoscope has a shaft made from a non-flexible material, for example stainless steel or metal. 
         [0005]    To examine a cavity of the body, a distal end area of the endoscope is introduced into the latter, while the endoscope head, and the part of the endoscope shaft not inserted into the body cavity, remain outside the body. 
         [0006]    The production of an endoscope comprises, among other things, connecting a proximal end area of the shaft to a distal end area of the endoscope head. 
         [0007]    Known methods involve preparing the endoscope head and the optic tube of the endoscope and pushing the two parts into one another in such a way that the optic tube is received with its proximal end area in the distal end area of the endoscope head. The contact surfaces of both end areas are connected to one another by soldering, welding or adhesive bonding. 
         [0008]    A disadvantage of these known methods is that connecting the endoscope head and the optic tube is technically very complicated. In the endoscope production process, suitable machines have to be provided that permit welding, soldering or adhesive bonding of the contact surfaces of the endoscope head and of the optic tube. Moreover, these known methods of connecting the endoscope head to the optic tube require a great deal of time. In particular, when bonding the two endoscope parts to one another, care must be taken to ensure that the optic tube and the endoscope head are held in a fixed position until the adhesive has dried. 
         [0009]    Another disadvantage of these methods is the difficulty in keeping the optic tube and the endoscope head exactly positioned relative to one another during the production process, such that the length of the endoscope is reproducible. If the resulting overall length of the produced endoscope deviates just slightly from the desired length, this difference in length has to be taken into account in the design of the optical waveguide system and the imaging optics. 
         [0010]    In the known production methods by means of welding and soldering; a further disadvantage is that; during the production process, heat develops in the area of the connecting site between the two endoscope parts. The heating of the material of the optic tube can cause said material to become brittle, thus reducing the strength of the optic tube in the area where it is affected by heat, with the result that the optic tube may already break under the effect of slight flexural stresses. 
         [0011]    A further disadvantage is that, in endoscopes that are produced by the known methods, the connection between the endoscope head and the optic tube is not stable. If, during an operation, the optic tube is subjected to a considerable leverage on account of a flexural stress, it is possible that the endoscope will break at the connecting site, i.e. the welding, soldering or adhesive bonding site; between the endoscope head and the optic tube. 
       SUMMARY 
       [0012]    It is therefore an object of the present invention to remedy this situation and to make available a method that is of the type mentioned at the outset and that permits a technically simple and stable connection between the endoscope head and the optic tube. 
         [0013]    It is also an object of the present invention to make available an endoscope of the type mentioned at the outset, in which the endoscope head is of a simple construction and is connected in a stable manner to the optic tube. 
         [0014]    According to an aspect to the invention, a method for producing an endoscope, the endoscope comprising an endoscope head and an optic tube, is provided, the method comprising the steps of providing the endoscope head, providing the optic tube, pushing a proximal end area of the optic tube into a distal end area of the endoscope head, and press-fitting the distal end area of the endoscope head with the proximal end area of the optic tube. 
         [0015]    According to another aspect of the invention, an endoscope is provided, comprising an endoscope head and an optic tube, wherein a proximal end area of the optic tube is press-fitted with a distal end area of the endoscope head. 
         [0016]    The method according to the invention and the endoscope according to the invention permit a technically very simple connection between the endoscope head and the optic tube. Press-fitting the two endoscope parts together advantageously requires no further auxiliaries, for example soldering tin or adhesive. Moreover, the method according to the invention can be carried out in less time than soldering, welding or adhesive bonding of the endoscope head to the optic tube. Therefore, during production of the endoscope, it is possible to omit process steps such as cooling or drying of the connecting site between the endoscope head and the optic tube. 
         [0017]    Also, by press-fitting the optic tube with the endoscope head, which pressing operation can be carried out cold and without heating, no material weakness is caused by the effect of heat, as does occur in the case of welding or soldering. 
         [0018]    A further advantage of the method according to the invention compared to the known methods is the fact that the connection between the optic tube and the endoscope head is stable, and remains so over the course of time. Since the two endoscope parts are pressed together, the endoscope is not sensitive to external influences, such as water. Consequently, the optic tube does not come loose, not even after a large number of cleaning processes of the endoscope, with the result that expensive repair work is avoided. 
         [0019]    The pressing together of the endoscope head and optic tube also permits a stable connection between both parts. In this way, the endoscope advantageously withstands even considerable flexural stresses of the optic tube that generate a considerable leverage on the optic tube. 
         [0020]    In a preferred embodiment, the proximal end area of the optic tube is press-fitted by axial compressing. 
         [0021]    This measure represents a constructionally simple pressing of the optic tube onto the endoscope head. Since the wall thickness of the optic tube is smaller than that of the endoscope head, the optic tube is more suitable for an axial compressing process than is the endoscope head for a crimping process. 
         [0022]    In another preferred embodiment, the optic tube is held in an axially fixed position during the pressing operation, and an axial force in the direction of a distal end area of the optic tube is exerted on the proximal end area of the optic tube. 
         [0023]    This measure has the advantage that the press-fitting of the optic tube with the endoscope head is achieved in a simple manner in that the inserted optic tube is held at the distal end of the endoscope head and an axial force, which acts in the direction of the distal end of the optic tube, is exerted on it at the same time. The proximal end area of the optic tube is thereby axially compressed and press-fitted with the endoscope head. 
         [0024]    In another preferred embodiment, the axial force is provided by a pressing tool, in particular a mandrel. 
         [0025]    This measure represents a technically simple possibility of generating the axial force acting on the optic tube. In contrast to the known methods, the outlay in terms of tools is much less. 
         [0026]    In another preferred embodiment, the distal end area of the endoscope head is provided on its inside with a circumferential recess into which material of the optic tube flows with a form fit during the pressing operation. 
         [0027]    This measure has the advantage that the optic tube is held in an axially particularly secured position in the endoscope head, because material of the optic tube engages in the recess of the endoscope head. Tensile forces and pressure forces on the optic tube in the axial direction do not lead to a change in position of the optic tube relative to the endoscope head. 
         [0028]    In another preferred embodiment, the circumferential recess is provided as a groove extending about the full circumference. 
         [0029]    This measure has the advantage that; because of this design of the recess, a particularly large amount of material can engage in the recess. The connection of the endoscope head to the optic tube is therefore particularly stable. 
         [0030]    In another preferred embodiment, the distal end area of the endoscope head is provided with at least one circumferentially limited cavity into which material of the optic tube flows with a form fit during the pressing operation. 
         [0031]    This measure has the advantage that the material pushed into the circumferentially limited cavity ensures that the optic tube cannot turn relative to the endoscope head about its longitudinal axis. In this way, the optic tube is secured against rotation in a simple manner. 
         [0032]    In another preferred embodiment, a proximal end of the optic tube is additionally widened in a trumpet shape. 
         [0033]    This measure has the advantage that the proximal end of the optic tube points outwards and away from the longitudinal axis of the optic tube. If, during subsequent assembly work, optical fibres are introduced through the optic tube and the endoscope head, these are advantageously prevented from damage, for example from kinking or breaking. 
         [0034]    In another preferred embodiment, the distal end area of the endoscope head is adhesively bonded to the proximal end area of the optic tube after the pressing operation. 
         [0035]    This measure has the advantage that the endoscope is sealed against external influences, for example water. However, in contrast to the known methods, the adhesive does not have to apply the adhesion force for the secure connection between optic tube and endoscope head, such that the adhesion site does not represent a predetermined break point. 
         [0036]    Further advantages and features will become clear from the following description and from the attached drawing. 
         [0037]    It will be appreciated that the aforementioned features and those still to be explained below can be used not only in the cited combinations, but also in other combinations or singly, without departing from the scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The invention is described and explained in more detail below on the basis of a number of selected illustrative embodiments and with reference to the attached drawing, in which: 
           [0039]      FIG. 1  shows a side view of an endoscope; 
           [0040]      FIG. 2  shows an optic tube (in cutaway view) and an endoscope head in longitudinal section at the start of a method for producing the endoscope; 
           [0041]      FIG. 3  shows the optic tube and the endoscope head from  FIG. 2  in a further method step of the production method; 
           [0042]      FIG. 4  shows the endoscope head and the optic tube from  FIG. 3  with a pressing tool in a further method step of the production method; 
           [0043]      FIG. 5  shows the endoscope head, the optic tube and the pressing tool from  FIG. 4  in a further method step of the production method; 
           [0044]      FIG. 6  shows the endoscope head, the optic tube and the pressing tool from  FIG. 5  in a further method step of the production method; 
           [0045]      FIG. 7  shows the endoscope head and the optic tube from  FIG. 6  and a further pressing tool in a further method step of the production method; 
           [0046]      FIG. 8  shows the endoscope head, the optic tube and the further pressing tool from  FIG. 7  in a further method step of the production method; and 
           [0047]      FIG. 9  shows the endoscope head in a cross section along the line I-I in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0048]    An endoscope designated by the general reference number  10  is shown in  FIG. 1 . The endoscope  10  comprises an endoscope head  12  and an endoscope shaft  14 . 
         [0049]    Such an endoscope  10  is used, for example, in minimally invasive surgery for examining body cavities or hollow organs. The distal end of the endoscope  10  is introduced into an opening in the body, such that at least the endoscope head  12  remains outside the body. 
         [0050]    The endoscope shaft  14  comprises an elongate optic tube  16  whose proximal end area  18  is connected to a distal end area  20  of the endoscope head  12 . The optic tube  16  is preferably designed as a cylinder-shaped hollow cylinder with a thin wall. 
         [0051]    A connector piece  22 , for an external lighting source, and an eyepiece  24  are arranged on the endoscope head  12 . The endoscope  10  also accommodates an optical waveguide system that extends from the connector piece  22  to a distal end area  26  of the optic tube  16  and is made up of optical fibres. The optical waveguide system is used to illuminate an operating site within the opening in the body. The endoscope  10  also accommodates an imaging system that extends from the eyepiece  24  to the distal end area  26  of the optic tube  16 . The imaging system can comprise optical fibres, rod lenses, or also an image sensor with electrical signal transmission. 
         [0052]    The endoscope  10  is preferably rigid, the optic tube  16  being made from non-flexible materials, for example steel or metal. 
         [0053]    In a method for producing the endoscope  10 , the optic tube  16  and the endoscope head  12  are provided in a first method step (see  FIG. 2 ). At its distal end area  20 , the endoscope head  12  has a circumferential recess  28  on its inside, and at least one circumferentially limited cavity  30 . 
         [0054]    The recess  28  is preferably designed as a groove  32  that extends about the full circumference in the distal end area  20  of the endoscope head  12 . The cavity  30  can either be arranged directly on a part of the recess  28  or can be arranged spatially separate from the latter in the distal end area  20  of the endoscope head  12 . Moreover, the cavity  30  can be set deeper in relation to the recess  28 , as seen in the radial direction of the distal end area  20  of the endoscope head  12 . 
         [0055]    An external diameter  34  of the optic tube  16  is dimensioned such that it is slightly smaller than an internal diameter  36  of the distal end area  20  of the endoscope head  12 . 
         [0056]    In a further method step, as is shown in  FIG. 3 , the proximal end area  18  of the optic tube  16  is pushed in a direction of an arrow  38  into the distal end area  20  of the endoscope head  12 . In doing so, an outer surface  40  of the optic tube  16  touches an inner surface  42  of the endoscope head  12 , or the outer surface  40  of the optic tube  16  is spaced slightly apart from the inner surface  42  of the distal end area  20  of the endoscope head  12 . Moreover, the proximal end area  18  of the optic tube  16  is pushed so far into the distal end area  20  of the endoscope head  12  that at least a proximal end  44  of the optic tube  16  extends past the recess  28  and the cavity  30 . 
         [0057]      FIGS. 4-8  show the distal end area  20  of the endoscope head  12  and the proximal end area  18  of the optic tube  16  being pressed together. 
         [0058]    The optic tube  16 , whose proximal end area  18  is pushed into the distal end area  20  of the endoscope head  12 , is held in an axially fixed position in respect of tensile forces and pressure forces acting in the axial direction of the optic tube  16  (see  FIG. 4 ). For this purpose, the optic tube  16  is clamped in a holding device  46 . Such a holding device  46  can, for example, have two jaws  48 ,  50 , which engage on the outer surface  40  of the inserted optic tube  16  distally of the distal end area  20  of the endoscope head  12 . The two jaws  48 ,  50  either touch the distal end area  20  of the endoscope head  12  or are spaced slightly apart from it. The jaws  48 ,  50  of the holding device  46  are shown in  FIG. 4 , whereas, for reasons of clarity, they are not shown in  FIGS. 5-8 . 
         [0059]    An axial force is exerted on the proximal end area  18  of the optic tube  16  in the direction of an arrow  52 . The axial force is generated by means of a pressing tool  54 , which is guided from the proximal direction through the endoscope head  12  into the optic tube  16 . 
         [0060]    The pressing tool  54  can preferably be designed as a cylindrical mandrel  56 . The pressing tool  54  narrows in a step shape at a distal end  58 , such that an external diameter  60  of the distal end  58  of the pressing tool  54  is slightly smaller than an internal diameter  62  of the optic tube  16 . Moreover, in the area of the step-shaped narrowing, the pressing tool  54  has a plane surface  64  that preferably extends about its full circumference and that is transverse to a longitudinal axis  66  of the pressing tool  54 , and on which the proximal end  44  of the optic tube  16  comes to lie on the full circumference. The distal end  58  of the pressing tool  54  is preferably of such a length that the pressing tool  54  extends past the recess  28  and the bulge  30  when in a fully inserted state, i.e. when the plane surface  64  touches the proximal end  44  of the optic tube  16 . 
         [0061]    As is shown in  FIG. 5 , the proximal end area  18  of the optic tube  16  is axially compressed by the axial force in such a way that axially compressed material is forced radially outwards. This is especially the case when the distal end  58  of the pressing tool  54  extends past the recess  28  and the cavity  30  and thus prevents a radially inwardly directed movement of the buckled material. Material of the proximal end area  18  of the optic tube  16  thus engages with a form fit in the recess  28  while the optic tube  16  is press-fitted with the endoscope head  12 . The engagement of the material of the optic tube  16  into the recess  28  permits a secure axial positioning of the optic tube  16  relative to the endoscope head  12 . 
         [0062]    The pressing action also causes material of the optic tube  16  to engage in the cavity  30  (see  FIG. 6 ). This ensures that the optic tube  16  is not able to turn relative to the endoscope head  12  about its longitudinal axis. 
         [0063]    As is shown in  FIG. 7 , the proximal end  44  of the optic tube  16  is also widened in a trumpet shape, such that the external diameter  34  of the optic tube  16  increases at this location. The proximal end  44  of the optic tube  16  points outwards and away from a longitudinal axis of the optic tube  16 . For this purpose, the pressing tool  54  is removed from the optic tube  16  and from the endoscope head  12 . A further pressing tool  68  is pushed, in the direction of the arrow  52 , through the endoscope head  12  and into the pressed-on optic tube  16 , and it exerts an axial force on the proximal end area  18  of the optic tube  16 . 
         [0064]    The further pressing tool  68  likewise narrows at the distal end, although the narrowing is not in the form of a step shape but instead extends over a concavely curved partial area of a distal end  70 . The smallest external diameter  72  of the distal end  70  of the further pressing tool  68  is also slightly smaller than the internal diameter  62  of the optic tube  16 . The narrowing distal end  70  of the further pressing tool  68  spreads the proximal end  44  of the optic tube  16  outwards in such a way that a shape of the proximal end  44  of the optic tube  16  adapts to a shape of the distal end  70  of the further pressing tool  68 . The pressing tool  54  and the pressing tool  68  can also be designed as one pressing tool, with which it is possible both to axially compress the proximal end area  18  of the optic tube  16  and also to widen the proximal end  44  of the optic tube  16 . 
         [0065]    During subsequent insertion of optical fibres into the endoscope  10 , the widened proximal end  44  of the optic tube  16  avoids damage to said optical fibres. 
         [0066]    Thereafter, the further pressing tool  68  is removed from the endoscope head  12  in the direction of an arrow  74  (see  FIG. 8 ). 
         [0067]    After the pressing operation, the proximal end area  18  of the optic tube  16  is also adhesively bonded to the distal end area  20  of the endoscope head  12 . For this purpose, an adhesive is applied to the outer surface  40  of the optic tube  16  and/or to the inner surface  42  of the distal end area  20  of the endoscope head  12 . The adhesive bonding of the optic tube  16  to the endoscope head  12  serves to seal off the connecting site of the two endoscope parts from external influences, such as water. 
         [0068]      FIG. 9  shows a cross-sectional view of the distal end area  20  of the endoscope head  12  along the line I-I in  FIG. 8 . The proximal end area  18  of the optic tube  16  is press-fitted with the distal end area  20  of the endoscope head  12 . Material of the optic tube  16  engages with a form fit in the recess  28 , formed as a groove  32  extending about the full circumference, and into the cavity  30 .