fig1 shows the basic construction of a rectoscope 10 which consists substantially of a head 12 and a tube 14 . there is a spacer sleeve 16 on the distal end of the tube 14 . on the proximal end of the tube 14 there is a shield 18 . tube 14 is attached detachably or permanently to the head 12 , of which the housing 20 , a holding ring 24 attached thereto , a cover 26 hinged to housing 20 , and a connecting fixture 22 and a screw 32 attached to the cover are illustrated . the connecting fixture 22 is used to attach a handle which is not shown , which either itself contains a lighting device or is connected to a cold light projector via a light - conducting cable . the light supplied from the handle is conducted from the connecting fixture 22 into the interior of the appliance via a bunch of light - conducting fibres . the exact construction of such a rectoscope is shown and described in detail in the german specification as - ps no . 1 566 179 cited above , incorporated herein by reference . fig2 is a perspective view of the head 12 and part of tube 14 of the rectoscope 10 , where the head housing and cover 26 are shown detached from each other . on one side of cover 26 , being the upper side in fig2 a seal 27 is attached . in a bore provided within the cover , a window 28 ( a flat glass disc or lens through which observation is possible when the cover is closed ) is installed by means of a holding ring 28 &# 39 ;. a connecting fixture 29 is attached to the cover , and compressed air can be blown through such fixture into the inside of the rectoscope . two diametrically opposed arms 43 and 44 are attached laterally to the cover 26 . arm 43 bears a radially adjustable screw 32 , while on the arm 44 an axial pin 46 is attached . pin 46 is dimensioned to fit in a bore 38 which is provided in a lug 36 attached to holding ring 24 . thus , when the axial pin 46 is inserted in the first bore 38 , cover 26 can be pivoted around an axis perpendicular to the axis of the rectoscope . thus , pin 46 in combination with bore 38 provide the means for opening and closing cover 26 . as is shown in more detail in fig3 a second bore 40 is provided in lug 36 on the holding ring 24 , bore 40 running perpendicular to the axis of first bore 38 and housing a compression spring 41 and a stop - ball 42 loaded thereby in the direction of first bore 38 . the stop - ball 42 projects into the contour of the bore 38 , so that when the axial pin 46 is inserted in the bore 38 , the stop - ball engages in an annular groove 48 cut in the axial pin . second bore 40 , at its end which opens to first bore 38 , has a burr 39 which can be punched in , for example , using a centre punch . in practice , cover 26 is therefore easily detached from the housing 20 of the head 12 , but on the other hand is held securely on it . the axial pin 46 and the bore 38 in the lug 36 thus form a releasable hinge 30 . instead of the axial pin being inserted directly in the bore 38 , having a bearing sleeve 56 , shown in fig6 can be inserted therein , having a bore the diameter of which is slightly smaller than that of the stop - ball 42 , lining up with the second bore 40 . when the axial pin 46 is inserted in the bearing sleeve , the stop - ball 42 then projects through the bore in the bearing sleeve into the annular groove 48 . referring to fig4 located in the arm 44 of the cover 26 there is a third bore 50 made in the form of a blind hole , the open end of which opens out in the face of the cover 26 opposite the axial pin 46 . the bore 50 houses a spring 52 and a stop - ball 54 which projects into a recess provided in the lug 36 when the cover 26 is in the open position . in this way the cover 26 is held securely in the open position without being able to swing shut accidentally as the endoscope is manipulated . on the side of the holding ring 24 opposite the lug 36 , a chamfer 35 is provided , sloping towards the distal end of the head 12 and towards its axis . screw 32 is provided with a spherical end 34 which engages behind chamfer 35 when the cover 26 is closed , as shown in fig5 . in this way , good sealing is always obtained , even after the endoscope has been in use for a long time . the chamfer 35 has the additional advantage that compressed air inside the rectoscope 10 can escape only slowly when the cover 26 is opened , which prevents discomfort to the patient due to the sudden release of the compressed air . thus , because of the engagement of the spherical end 34 and the chamfer 35 only a small slot is opened initially so that the pressure inside the rectoscope 10 escapes only slowly , instead of all at once as would happen with a sudden complete opening of cover 26 . while the invention has been disclosed particularly in the form of a rectoscope , it is to be understood that the releasable cover - housing head arrangement may be adapted for use with any other type of instrument . the important features are that the hinge pin be secured from accidental loosening when the cover is attached to the housing ; that the hinge pin be easily released for detaching the cover from the housing ( or that the cover be easily released from the pin if the pin is integral with the housing and the bore is in the cover ); that the cover be held securely in the open position once it has been opened ; and that the cover can be clamped closed onto the housing by means of the screw - chamfer arrangement . all of these features are adaptable to a cover / housing combination in any instrument environment , it being understood that the rectoscope as illustrated is a preferred embodiment but only one of many embodiments within the scope of the invention .
the invention discloses an endoscope , and particularly a rectoscope , having an improved means of securing a cover to the head housing of the endoscope using a releasable hinge . in a preferred embodiment a pin removably located in a bore forms the hinge for the cover connection .