Abstract:
An eyepiece assembly for an endoscope focusable by an exterior focusing collar is made soakable by using an O ring and very fine screwthreads to prevent liquid sterilant from penetrating under the collar and entering the interior of the eyepiece. The use of an O ring also provides a uniform resistance to the turning of the focusing collar and makes the focusing adjustment shock resistant. In another aspect of the invention, the placement of the light fiber connector on the discardable stop housing improves light transmission and allows one-handed focusing of the eyepiece.

Description:
FIELD OF THE INVENTION 
     This invention relates to endoscopes, and more particularly to an endoscope sterilizable by immersion into a liquid sterilant. 
     BACKGROUND OF THE INVENTION 
     In a hospital environment, sterilization is generally accomplished by one of three methods: 1) exposure to a sterilant gas; 2) steam autoclaving; or 3) immersion into a liquid sterilant. Because of the inability of some endoscope materials to withstand autoclaving temperatures, and because gas sterilization may be unavailable or impractical in some situations, it is desirable for an endoscope to be sterilizable by liquid immersion. 
     Unfortunately, prior art adjustable-focus endoscopes such as those shown in copending application Ser. No. 720,590 filed Apr. 8, 1985 and entitled &#34;Disposable Small Diameter Rigid Endoscope&#34; could not be liquid-sterilized because the liquid would seep into the lens cavity of the eyepiece through the adjustment mechanism and would become trapped therein. It was therefore desirable to create an immersible or soakable endoscope which was easy to adjust, as inexpensive as possible to manufacture, and capable of maintaining its adjustment under rough handling. 
     SUMMARY OF THE INVENTION 
     The present invention fulfills the objectives stated above by providing an optical adjustment mechanism for an endoscope which resists the penetration of liquid into the lens chamber by using an O-ring seal and very fine screwthreads to seal the adjustment mechanisms, and by using a sliding pin arrangement to hold the stop housing against relative rotation with respect to the eyepiece. 
     In addition to making the endoscope soakable, the mechanism of this invention has several other advantages. For one, it not only allows the eyepiece and stop housing to be made entirely of plastic (thereby saving cost), but it actually encourages the use of plastic for optimum performance. Secondly, it allows convenient one-handed adjustment of the endoscope. Thirdly, the containment of the light and image fiber entirely within the stop housing saves at least one light fiber connection, thereby increasing the light efficiency of the instrument. Fourthly, the O-ring seal provides a uniform resistance to turning the adjustment collar and prevents accidental misadjustment of the focus by rough handling. Fifthly, the uncemented mounting of the lens in the inventive arrangement makes the lens self-aligning and interchangeable. Sixthly, the ability to factory-adjust the throw of the mechanism allows considerable loosening of the manufacturing tolerance for the image fiber rod whose end must be cut and polished--a process in which it is very difficult and costly to maintain close tolerance. Seventhly, the inventive mechanism makes the endoscope soakable in both assembled (fully disposable) form and disassembled (non-disposable eyepiece) form. Eighthly, assembly of the eyepiece and stop housing requires no alignment because the image fiber rod is centered on the axis of the eyepiece. 
     It is thus the principal object of the invention to provide a liquid-impervious focus adjustment mechanism for endoscopes. 
     It is another object of the invention to provide a mechanism of the type described which is easy to adjust and resists misadjustment due to rough handling. 
     It is a further object of the invention to provide a mechanism of the type described which provides enhanced ease of manufacture and attendant cost savings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an axial vertical section of a urethral endoscope constructed in accordance with the invention, in assembled form; 
     FIG. 2 is an enlarged transverse vertical section of the catheter portion of the device along line 2--2 of FIG. 1; 
     FIG. 3 is an exploded view of a preferred embodiment of the invention; 
     FIG. 4 is an exploded view of an alternative embodiment of the invention; 
     FIG. 5 is a perspective view showing the method of adjustment of the device of this invention; 
     FIG. 6 is an exploded view of another alternative embodiment of the invention; 
     FIG. 7 is an axial vertical section of the device of FIG. 6 in the unlocked position; and 
     FIG. 8 is a section similar to FIG. 7 but showing the device in the locked position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 through 3 show a preferred embodiment of the invention. In these figures, the numeral 10 designates a urethral endoscope which consists of an eyepiece 12 including a lens chamber 14, an adjustment cavity 16, an adjustment collar 18, and a stop housing connector 20; a stop housing 22 including a light source connector 24; a conventional flexible fiber conduit 26; a conventional Y connector 28; and a conventional flexible multi-lumen urethral catheter 30 with an optical objective element 32 at its distal end. 
     In the manufacture of the eyepiece 12, a lens 40 is loosely inserted into the barrel 42 of the eyepiece 12 into which a plano 44 has previously been press-fitted, and the lens retainer 46 is screwed into the barrel 42. Next, the stop housing connector is aligned with the barrel 42 so that the pin 48 of the barrel 42 is coaxial with the pin guide opening 50 of the stop housing connector 20, and the adjustment collar 18, which has previously been screwed onto the stop housing connector 20, is slipped over the barrel 42 until it locks into place by the action of the snap ring 52. The stop screw 54 can now be loosely inserted into the recess 56 of the stop connector 20 and screwed into the lens retainer 46 to the desired depth. A gasket 58 is next inserted into the recess 60 of stop housing connector 20, whereupon the eyepiece 12 can be assembled with the stop housing 22. 
     In the embodiment of FIGS. 1 and 2, the stop housing 22 is assembled with the eyepiece 12 by screwing its threaded nose 62 into the threaded recess 60 of the stop housing connector 20 until the transverse face 64 of the nose 62 sealingly engages the gasket 58. In the embodiment of FIG. 4, the assembly is done by hooking a pair of pins 72 into guide slots 74 and twisting the stop housing 22 until the resiliency of the gasket 58 pushes the pins 72 into the lock recesses 76 of the guide slots 74. 
     In the assembly of eyepiece 12 and stop housing 22, by either method, the steel-sheathed end 66 of the image fiber 68 slips into the central bore 70 of stop screw 54 where it is held in alignment with lens 40. 
     In accordance with one aspect of the invention, the light source connector 24 is mounted on the stop housing 22 rather than on the eyepiece 12 as in the prior art. This construction has several advantages. First, it avoids a discontinuity in the light fibers 78, and the inevitable resulting loss of light efficiency; secondly, it avoids the need for rotational alignment of the stop housing 22 with the eyepiece 12 during assembly; and thirdly, the light source connector 24 provides a finger grip for the one-handed adjustment of the endoscope 10 as hereinafter described. 
     The endoscope 10 of this invention is focused by turning the collar 18 with respect to the eyepiece barrel 42. Because of the engagement of pin 48 with pin guide opening 50, the stop housing connector cannot rotate with respect to the eyepiece barrel 42 but can only translate in an axial direction. The leftward movement of the connector 20 in FIG. 1 is limited by its engagement with the shoulder 80 of the barrel 42, while its rightward movement is limited by the engagement of shoulder 82 of connector 20 with the head 84 of stop screw 54. 
     In the mechanism of this invention, the throw or range of movement of connector 20 is adjustable by screwing the stop screw 54 into or out of the lens retainer 42. This is a useful feature when using the eyepiece 12 with different lenses 40 or different stop housings 22 whose image fibers may terminate at different distances from the nose 62. 
     In the structure of FIGS. 1, 3 and 4, an O ring 86 serves the dual function of sealing the left end (in FIG. 1) of collar 18 against liquid penetration between collar 18 and barrel 42, and of offering a constant, soft frictional resistance to the turning of collar 18. This makes it easier to properly focus the endoscope 10, and the resilience of the O ring 86 allows the endoscope 10 to maintain its focus if the eyepiece 12 is dropped or otherwise carelessly handled. 
     The right end (in FIG. 1) of the collar 18 is sealed against liquid penetration between collar 18 and connector 20 by using a very fine screwthread (e.g. twenty or more threads per centimeter) where the collar 18 is screwed onto the connector 20. Due to the resiliency of plastic materials, it is advantageous to form the collar 18 and connector 20 (as well as all the other parts of the eyepiece 12 and stop housing 22) of plastic rather than metal. This is, of course, also a desirable thing to do from a standpoint of manufacturing cost. The seal between stop housing 22 and eyepiece 12 is provided by gasket 58. 
     In the device of this invention, it is practical to form the pin (or pins if more than one is provided) 48 as an integral part of barrel 42, because the stress imposed upon the pin 48 in order to prevent rotation of connector 20 is so much less than the stress imposed upon the guide pins of the prior art shown in the above-mentioned copending application Ser. No. 720,590 that it need not be made of metal. 
     FIG. 5 illustrates an advantage of the present invention which is produced by locating the light source connector 24 on the stop housing 22 rather than on the eyepiece 12. By positioning the middle finger 88 and the ring finger 90 on each side of the light source connector 24, and the little finger 92 underneath the stop housing 22, the collar 18 can easily be turned between the thumb 94 and index finger 96 while looking through the eyepiece 12, without rotating either the stop housing 22 or the eyepiece barrel 42. 
     FIGS. 6 through 8 illustrate an alternative embodiment of the invention in which the focusing is done simply by screwing the eyepiece 112 more or less deeply onto the stop housing 122. An O ring 186 interposed between two adjacent sets of screwthreads on stop housing 122 provides the seal which allows soaking the endoscope 110 without fear of liquid penetration. The same turning resistance and immunity to rough handling are provided by O ring 186 as are provided by O ring 86 in the previously discussed embodiments. One-handed adjustment is also possible as shown in FIG. 5; however, in the embodiment of FIGS. 6 through 8, the eyepiece 112 would have to rotate with respect to stop housing 122 during adjustment. 
     A screwthreaded locking ring 198 is provided in the embodiment of FIGS. 6 through 8 to lock a focus setting against movement. In the position of locking ring 198 shown on FIG. 7, the focus of the endoscope 110 can be adjusted by rotating the eyepiece 112 with respect to the stop housing 122. After the proper focus setting has been made, the locking ring 198 is screwed toward the eyepiece 112 until it engages the eyepiece 112 and squeezes its threads to prevent further rotation.