GB464288A - Telemeter for taking direct measurements of horizontal distances with a horizontal or a vertical staff - Google Patents

Abstract

464,288. Surveying instruments. ALT, H. Oct. 14, 1935, No. 28342. Convention date, Oct. 12, 1934. [Class 97 (ii)] A telescope is aimed at a mark at one end of a horizontal or vertical staff, clamped, and a fine adjustment effected by a micrometer screw, whereupon the telescope is rocked by a second micrometer screw, through a predetermined angle modified in accordance with the inclination of the telescope so that the intercept on the staff corresponds to the horizontal distance between the staff and telescope. Fig. 3a shows a fitment to adapt a telescope for use with a horizontal staff. A block M carrying a micrometer screw B engaging a member V may be clamped to the vertical axle of the telescope when the latter has been roughly sighted on the staff mark. The member V carries a micrometer screw A which engages the horizontal circle L of the telescope and serves to set the latter accurately on the staff mark. Spring plungers F keep the parts V and L pressed against the screws B, A. The screw B is then moved axially through a constant distance determined by abutments, whereupon the telescope is moved through an angle the intercept of which on the staff is independent of the inclination of the telescope axis. When the length of the staff subtends an angle less than the angle defined by the full movement of the screw B, the latter is rotated until the telescope has swung over the total length of the staff whereupon the screw A is used to bring the telescope back to the initial position and the length of the'staff again traversed by rotating the screw B and so on till the full movement of the screw B has been effected. Alternatively the head of the screw B may have a hundred graduations and the number of graduations corresponding to a traverse of the complete staff length determined. The number of staff lengths intercepted by the predetermined angle may then be calculated from the number of graduations corresponding to the full movement of the screw B. Fig. 8 shows a telescope adapted for use with a vertical staff. H is a lever fixed to the telescope F and engaging a roller W on a slide K<1> which can be manually slid along a bar S until the telescope is roughly adjusted on the staff mark and clamped. The bar S is moved on the guides M to effect a fine adjustment by rotating the nut A and the guides M together with the bar S are moved by the micrometer screw B to cause the telescope to move through the desired parallactic angle. A spring C keeps the bar S pressed against the nut A and the supports M pressed against the screw B.