Patent GB-484250-A (GB)
Title: Improvements in episcopic apparatus
IPC: G03B21/06
Filed: 1937-03-31
Abstract: 484,250. Episcopic projection apparatus. ANCIENS ETABLISSEMENTS BARBIER, BENARD, & TURENNE. March 31, 1937, Nos. 9159, 9160, and 9161. Convention dates, April 2, 1936, June 15, 1936, and March 30, 1937. [Class 97 (i)] In episcopic apparatus having two objectives of different focal lengths to project a small object-field or a large object-field respectively, each objective is brought into its operative position when the other is moved to its inoperative position ; the operative position of the small-field objective is between the field, for example a surgical operating table, and the usual image-erecting mirror, whereas that of the large-field objective is between the mirror and the screen. As shown in Fig. 2, the smallfield objective O<1> and the objective O<2> are carried on a lever L pivoted at A. In the position shown, rays R<1> pass from the object C to the screen E via the mirror M. The lever L is held fixed by engagement of a finger L<1> in a notch S<1> on a segment S pivoted at S<3> and held by a spring S<4>. To project a large object-field the segment S is released and the lever L rotated until the objective O<2> occupies the dotted position O<1>2 when the lever is clamped by engagement of the finger L<1> with a second notch S<2>. The objective O<1> now occupies the position vacated by the objective O<2> and the rays R<2> from the large object-field are projected on the screen E. In the modification shown in Fig. 3, focusing and changing of the objectives is effected by mechanical means such as an electric motor. The objectives O<1>, O<2> are carried on a shaft A rotatable in a frame 1 vertically movable in a slot 3 in a fixed frame 2 and carrying the mirror M. An electric motor 7 drives a reduction gear 8 which may be clutched either to a pinion 15 or a gear 18, or may be free. The pinion 15 engages a wheel 16 keyed on the shaft A to rotate the latter, and the gear 18 engages a rack 19 to raise or lower the carriage 1 for focusing. Stops 21 are provided to limit the rotation of the shaft A and switches may also be provided to switch off the motor or to declutch the drive when one or other objective has been moved to its operative position ; switches may also be provided at the ends of the slot 3 to switch off or declutch the motor when the carriage 1 reaches either of these positions. Both the drive of the motor and the actuation of the clutches may be controlled from a distance by suitable electrical or other means where, for example, the projection screen is not in the same room as the object. To obviate movement of the mirror M and consequently of the image during focusing the apparatus shown in Fig. 6 is employed. The objectives O<1>, O<2>, (not shown), and driving motor 107 are carried on a frame 101 pivoted on a shaft 102 which carries the fixed mirror M. The objective O<1> is carried on a bracket 105 sliding radially in a pair of arms 104 for focusing. The objective O<2> (not shown) is similarly supported in a pair of arms. The motor 107 drives a sleeve 109 having clutch surfaces 110 and 111 ; on movement of the sleeve to the left to change the objectives, the surface 110 engages a surface 110a on a gear 115 which, through a gear train drives a worm wheel 117 engaging a segment 118 fixed to the frame 119, thus causing the frame 101 to rotate about the shaft 102. To focus the objectives the sleeve 9 is moved to the right when clutch surface 111 engages a surface 111a on a gear 120 which drives through a gear train a screwthreaded shaft 127 connected to the bracket 105 so that the bracket moves in the arms 104. The shaft driving 'the shaft 127 carries a gear 123 engaging a corresponding gear connected to the objective O<2> so that both objectives move together although only one is in operation. A solenoid 136 permits remote control of the sleeve 109 and a switch may be provided to control the motor 107.