GB190817371A - An Improved Method of and Means for Testing the Accuracy of the Sighting Apparatus of Ordnance. - Google Patents

Abstract

17,371. Burns, W. A. Aug. 18. Optical instruments; telescopes.-For testing the parallelism of the line of sight and the bore of the gun at zero elevation, and also the graduations of the range and deflexion scales, and the accuracy of the permanent drift correction, a mirror is mounted at the muzzle of the gun with its plane truly perpendicular to the axis of the bore, or at a known inclination thereto, and the sighting-telescope is replaced by a testing-telescope A constructed as shown in Fig. 1 with cross-wires at X and an external pointer B, the tip of which is in the optical axis of the telescope. In small guns, the mirror C is set perpendicular to the bore, and if at zero elevation of the gun and sights, the image of the tip of the pointer, seen through the telescope, appears at the point of intersection of the cross-wires, the line of sight and the bore of the gun are parallel. Fig. 7 shows an arrangement for use with larger guns in which the sighting-apparatus is at a distance from the gun. The testing- telescope A, constructed as described above, is pivoted at a in a frame a<1>, which in turn is vertically pivoted at e<1> upon the sight bar E. The mirror C is mounted upon an axis H supported in bearings in arms g attached to the muzzle D of the gun. The initial adjustment of the mirror with its plane perpendicular to the axis of the bore is made by sighting cross-wires or a small aperture in an attachment K at the breech end of the gun through a telescope J rigidly secured to the axis H. The mirror is then tilted through a suitable angle, indicated by a pointer L<1> on a scale L, and the telescope A is turned upon its trunnions a until the image of the tip of the pointer B in the mirror C is seen at the point of intersection of the cross-wires X. If the angle recorded by a pointer a<3> upon a scale a' is the same as that through which the mirror has been tilted, the zero axes of the gun and sights are parallel. The range graduations on the sighting-apparatus are afterwards tested by adjusting the sight-bar E for a given range by the sightelevating gear, and sighting the image of the pointer B by swinging the telescope A about the pivot a. If the angle through which the telescope is thus swung is the same as the known angle of sight elevation which corresponds to the given range, the range graduation is accurate. The deflexion graduations are similarly tested by lateral displacements of the telescope A and the frame a' about the pivot e<1>. As the axis e<2> is inclined to give the permanent drift correction, the accuracy of this correction is tested when testing the range graduations since it is necessary, in order to cause the image of the pointer to coincide with the intersection of the cross-wires, to swing the frame a<1> about the pivot e<1> to neutralize the lateral displacement given to the line of sight by the inclination of the axis e<2>.