Patent GB-1421490-A (GB)
Title: Facsimile system with provision for document loading and unloading
IPC: G03B27/62
Filed: 1973-12-28
Abstract: 1421490 Facsimile systems MINNESOTA MINING & MFG CO 28 Dec 1973 [29 Dec 1972] 60051/73 Heading H4F In a facsimile system employing a rotatable drum provided with releasable clamping means for a document the drum is rotated in the forward (normal scanning) direction to a reference position at which a document is loaded and clamped and in the reverse direction to unload and unclamp the document at a " positioning " speed which is less than the normal operating speed. Fig. 1, shows the general form of the apparatus which is capable of transmitting data over a telephone line and Fig. 2, shows the control circuitry associated with the operation of the invention. To load a document, the latter, 360 (see also Fig. 4) is placed on a document shelf 6 and its leading edge 362 is pushed through opening 8 into a slot 350 in the drum 2 which is initially at a reference position. Load/unload switch 164 (Fig. 2) is then momentarily closed and causes document clamp drive circuit 230 to release clamping bar 354 and clamping finger 352 which are spring biased "upwards" and operate to clamp the document. After a delay of 200-300 m. sec. the drum motor 121 is operated at the " positioning " speed (approx. 32 r.p.m.) by control oscillator 140 to rotate the drum 2 in the forward direction (arrow A) so that the document is drawn around the drum. When the latter has made one complete revolution a magnet 186 carried by the drum operates a reed switch 184 (in positioning apparatus 182) which stops the drum rotation in the position shown in Fig. 4. A logical " 0 " on run control conductor 309 is now replaced by a logical " 1 " resulting in the disabling of position speed control oscillator 140 and the enabling of run speed oscillator 12 which causes the drums to rotate in the forward direction (arrow A) at the normal operating speed (180 r.p.m.). When the transmission of data is completed known control apparatus replaces the logical " 1 " on conductor 309 by a logical " 0 " so that oscillator 140 again controls the speed of the drum and if at this instant magnet 186 is not adjacent reed switch 184 or adjacent a second reed switch 185 the drum continues to rotate in the forward direction at 32 r.p.m. until switch 184 is closed. If, however, the drum over-shoots and magnet 186 comes to rest adjacent reed switch 185 switch 184 opens and the closure of switch 185 causes the motor to reverse the direction of drum rotation until magnet 186 is positioned adjacent switch 184 as shown in Fig. 4. To unload the document the load/unload switch 164 is momentarily closed and this causes oscillator 140 to drive the drum in the reverse direction (arrow B, Fig. 5) so that the document 360, the unclamped edge 364 (Fig. 4) of which biases itself away from the drum surface, is guided by the inner surface 338 of access door 7 through opening 8 on to the document shelf 6. When the closure of reed switch 184 signals that a complete rotation (in the reverse direction) has been completed (Fig. 6) the rotation is stopped and after a delay of 200-300 m. sec. the clamping mechanism is operated to release the document. Details of the control circuitry of Fig. 2 are given with reference to Figs. 3A, 3B and 3C (not shown).