Optical instruments of this type for minimally invasive surgery are disclosed, for example, by DE 195 07 205C2.
In order to ensure that, even under the high thermal load of autoclaving, no moisture intrudes into the instrument housing, it is known from practice that the end windows on the at the end side used as glass covers and/or end lenses are connected to the instrument housing by soldering or brazing fluid-tightly.
In order to solder the end window into the corresponding window frame of the instrument housing, the end window has a metallic edge coating, whereby the end window can be soldered with the aid of a tin or gold solder into the window frame provided for this purpose. The corresponding end window is surrounded by a liquid solder bath when soldered into the window frame. In a position where the end window is essentially floating in the solder bath, it is difficult to position the end window precisely in the center of the window frame. The eccentric position of the end window automatically results in a different thickness of the solder layer between the end window and the window frame.
Due to the different coefficients of thermal expansion of the materials used for the instrument housing, the window frame and the solder, significant stresses are always present, especially when the end window is placed eccentrically in the window frame, which can lead to the formation of cracks and/or stress ruptures in the end window and consequent non-sealing.
Technical realization elements:
In this context, it is an object of the present invention to provide optical instruments for use in minimally invasive surgery, in which the end window can be fixed in a corresponding window frame with low stress.
A solution for the realization of this object according to the present invention is characterized in that at least two zones protruding radially inwardly from the window frame are constructed on the inner periphery of each window frame facing the corresponding end window.
By constructing separate individual segments protruding radially inwardly from the window frame, the corresponding end window is maintained in the middle of the window frame during welding, since there is essentially no space left for an eccentric arrangement of the end window based on the radially inwardly protruding segments. The construction thus allows that a solder edge of substantially uniform thickness may be formed around the entire perimeter of the end window to be soldered. The stresses acting on the corresponding end window which occur during brazing and cooling can be significantly reduced by the uniform thickness of the solder edge around the corresponding end window, so that stress cracks or stress ruptures no longer occur on the end window.
It is proposed by the preferred embodiment of the present invention to construct three or four zones protruding inwardly along a radial direction on each window frame.
It has been found that the manner of construction of the three or four radially inwardly protruding segments is particularly effective so as to ensure a centered arrangement of the end windows in the corresponding window frames and, on the other hand, to provide sufficient free space for the formation of solder edges of substantially uniform thickness.
Of course it is also possible according to the present invention to provide more than four radially inwardly protruding segments in the corresponding window frame.
In addition, it is provided by the present invention that a gap for constructing the solder layer is left between the radial inner surface of the radially inwardly protruding segments of each window frame and the corresponding end window. The gap left between the window frame and the end window ensures that the solder edge which completely surrounds the end window at the periphery is constructed in such a manner that the solder edge ensures a fluid-tight seal.
In order to form zones protruding inwardly along the radial direction, it is proposed according to the present invention that each zone protruding inwardly along the radial direction from the window frame is constructed as a front arching portion of a waveform.
Because of the corrugated front arches, an essentially point-only construction method in which the edge of the solder between the window frame and the end window is constructed as a particularly thin area is realized.
The waveform construction of the radially inwardly protruding section of the window frame is sufficient to allow the end window to be placed in the middle of the window frame on the one hand, and on the other hand ensures the construction of the solder edge of substantially uniform thickness, thereby significantly reducing the possible stresses due to the difference in coefficients of thermal expansion of the materials used.
In order to ensure the centering of the end window in the corresponding window frame, it is proposed according to the present invention that the front arches of all waveforms of a window frame have the same arch radius. It is of course possible that the arching radius of the front arching portion of the waveform of each window frame in an optical instrument having a plurality of end windows is different from the arching radius of the other window frames of the same optical instrument.
Stresses which may occur due to differences in the thermal expansion systems of the materials used may also be reduced according to the present invention by means of, i.e., zones protruding inwardly in the radial direction being arranged uniformly distributed over the inner circumference of the corresponding window frames. This means, for example, that the three zones in the case of using three zones are arranged at 120° and the four zones in the case of four zones are arranged staggered from each other at 90° on the inner circumference of the window frame.
In order to form a window frame for accommodating an end window, it is proposed by the present invention that a window frame is formed at the distal and/or proximal end of the instrument housing. The manner of construction in which the inner wall of the housing at the distal and/or proximal end serves directly as the window frame is particularly applied in optical instruments having a small diameter of the barrel, for example less than 10 mm.
Finally, it is suggested by alternative embodiments of the present invention that the window frame is constructed as a separate member that can be secured to the distal and/or proximal end of the instrument housing. The manner in which the window frame is constructed as a separate member that can be secured to the inner wall of the housing at the distal and/or proximal end is particularly applicable in optical instruments with larger barrel diameters, e.g., 10 mm and larger.
Description of the accompanying drawings
Other features and advantages of the present invention are obtained in accordance with the corresponding accompanying drawings illustrating only exemplary embodiments of an optical instrument for minimally invasive surgery according to the present invention, to which the present invention is not limited. Illustrated in the accompanying drawings are:
Fig. 1 illustrates a schematic longitudinal section of an optical instrument for minimally invasive surgery constructed as an endoscope according to the prior art;
Fig. 2 illustrates a cross-sectionalized front view of the distal end of an optical instrument according to the present invention; and
Fig. 3 illustrates an enlarged schematic view according to detail III of Fig. 2.
Particular embodiments
The drawing of FIG. 1 schematically illustrates the construction of an optical instrument 1 constructed as an endoscope for minimally invasive surgery. The optical instrument 1 has a hollow instrument housing 2, and various optical elements, such as a lens 3 and a fiber optic bundle 4, are arranged in the hollow instrument housing.
The instrument housing 2 is fluid-tightly closed at a distal end 5 and at a proximal end 6, respectively, by means of an end window 7, which is arranged in a window frame 8 whose periphery completely surrounds the end window 7.
In the optical instrument 1 illustrated in FIG. 1, the end window 7 at the distal end is constructed as an end lens 9 and the end window 7 at the proximal end is constructed as a glass cover 10 in an eyepiece unit 11.
Endoscopes and other medical optics 1 have to be sterilized before each use. Sterilization is nowadays carried out with the aid of autoclaving, in which the optical instruments 1 are treated with hot steam at a pressure higher than 3 bar and at a temperature higher than 130°C.
In order to ensure that no moisture intrudes into the instrument housing 2, even under the high thermal load of autoclaving, the end window 7 on the end side, which is used as the glass cover 10 and/or the end lens 9, is in particular fluid-tightly connected to the instrument housing 2 by means of a thermal bonding process, e.g. welding or brazing. Typically, bonding methods are not suitable for joining the end windows 7, since bonded connections cannot withstand the thermal loads of autoclaving for long periods of time.
During autoclaving of the optical instrument 1, due to the different coefficients of thermal expansion of the materials used, a significant stress can occur in the end window 7 welded or brazed to the instrument housing 2, which significant stress can lead to the formation of cracks and/or stress ruptures in the end window 7 and a consequent non-sealing.
This stress occurs in the optical instrument 1 according to the prior art in such a way that the corresponding end window 7 is surrounded by a bath of liquid solder and fastened only by means of a solder mandrel when soldered into the window frame 8. In order for the end windows 7 to be soldered into the corresponding window frames 8 of the instrument housing 2, the end windows 7 have a metallic edge coating, whereby the end windows can be soldered with the aid of tin or gold solder into the window frames 8 provided for this purpose.
In a position where the end window 7 is essentially floating in the solder bath, it is difficult, particularly in angled optical systems, to arrange the end window 7 precisely in the middle of the window frame 8. The eccentric position of the end window 7 at this point automatically results in a different thickness of the solder layer between the end window 7 and the window frame 8, which results in a different thermal expansion during brazing and a different thermal contraction during subsequent cooling.
In order to construct the window frame 8 for housing the end window 7, two different embodiments are provided in principle.
Preferably, in optical instruments 1 in which the cylinder diameter of the instrument housing 2 is small, e.g. less than 10 mm in diameter, the window frame 8 is formed directly in the inner wall of the housing of the instrument housing 2, in particular at the distal end 5 of the instrument housing 2.
In optical instruments 1 in which the cylinder diameter of the instrument housing 2 is large, e.g. a cylinder diameter of 10 mm and larger, in particular at the distal end 5 of the instrument housing 2, the window frame 8 is constructed as a separate structure. The window frame 8 is constructed as a separate member, the separate member being fixable to the inner wall of the housing at the distal end of the instrument housing 2, as illustrated in FIG. 2.
The construction of the window frame 8 is described below in accordance with FIGS. 2 and 3 of the accompanying drawings.
In order to provide the optical instrument 1 in which the end windows 7 can be fixed in the corresponding window frames 8 with low stress, at least two zones 12 protruding radially inwardly from the window frames 8 are constructed on the inner peripheral surface of each window frame 8 facing the corresponding end window 7.
As can be seen in particular from FIG. 3, the zones 12 protruding inwardly radially are preferably constructed as a front arched portion 13 of the waveforms of the window frames 8. The radial direction of the zones 12 protruding inwardly from the window frames 8 is as follows. The dimensions of the radial height of the protruding segments 12 are so determined that a gap 15 for constructing the solder layer is left between the radial inner surface 14 of the radially inwardly protruding segment 12 of each window frame 8 and the corresponding end window 7.
By constructing separate individual segments 12 protruding radially inwardly from the window frame 8, the corresponding end window 7 is kept in the middle of the window frame 8 during soldering, because Based on the radially inwardly protruding segments 12 and the only very small gap 15 between the radially inner surface 14 of the segments 12 and the outer periphery of the end window 7 essentially no space is left for an eccentric arrangement of the end window 7. The configuration thus allows that a solder edge of substantially uniform thickness can be formed on the entire periphery of the end window 8 to be brazed. The stresses acting on the corresponding end windows 7 that occur during brazing and cooling can be significantly reduced by the solder edges of uniform thickness around the corresponding end windows 7, so that stress cracks or stress ruptures no longer occur on the end windows 7.
In the embodiment illustrated in FIG. 2, the window frame has four radially inwardly protruding segments 12 constructed as waveform front arches 13. Of course, it is also possible to have only three or more than four radially inwardly protruding segments 12 per window frame 8.
In the accompanying FIG. 2, the waveform front arches 13 are proportionally enlarged with respect to the window frames 8 as well as with respect to the end windows 7 and are not shown in dimensional proportion so that they can be clearly seen. scale, so that the construction of the radially inwardly protruding segments 12 can be clearly shown.
As can also be seen from FIG. 2, the four radially inwardly protruding segments 12 are arranged at 90° staggered from each other evenly distributed on the inner circumference of the window frame 8. The uniform distribution of the radially inwardly protruding segments 12 over the inner circumference of the window frame 8 reduces the appearance of stresses, since it thereby allows solder edges to be more uniformly formed on the periphery of the end window 7, which is advantageous even if the number of radially inwardly protruding segments 12 is other than the number of segments 12 evenly distributed at a corresponding angular spacing.
In order to ensure the centered position of the end window 7 in the corresponding window frame 8, the front arched portion 13 of the waveforms of the window frame 8 has the same arch radius r.
It is of course possible to make the arch radius r of the front arched portion 13 of the waveforms of each of the window frames 8 different from the arch radius r of the other window frames 8 of the same optical instrument 1 in the optic 1 having multiple end windows 7.
Thus, the window frames 8 of the optical instrument 1 constructed as previously described are characterized in that, based on the construction of the zones 12 protruding radially inwardly from the window frames 8, the end windows 7 which need to be welded into the window frames 8 may always be located in the middle of the window frames 8. This at the same time ensures that a solder edge of substantially uniform thickness is constructed between the window frame 8 and the end windows 7, whereby the stresses acting on the corresponding end windows 7 that appear during brazing and cooling may be significantly reduced, so that no stress cracks or stress ruptures no longer appear on the end windows 7.
List of appended markings
1 Optical instrument
2 Instrument housing
3 Lens
4 Fiber optic bundle
5 Distal end
6 Proximal end
7 End window
8 Window frame
9 End lens
10 Glass cover
11 Eyepiece unit
12 Zone
13 Front arch
14 Inner surface
15 Gap
r Arch radius