Patent GB-651782-A (GB)
Title: Facsimile recording system
IPC: H04N1/032
Filed: 1947-08-25
Abstract: 651,782. Gearing for stopping machinery. FINCH TELECOMMUNICATIONS, Inc. Aug. 25, 1947, No. 23478/47. Convention date, Dec. 8,1944. [Class 80(ii)] [Also in Group XL(b)] In a facsimile recorder in which a marking member traces a helical path on the inside of a drum an electromagnetically controlled gearing arrangement (including clutch and braking members) is provided for stopping the movement of the marking member at the end of a recording cycle and for returning it to its initial position preparatory to commencing a further recording cycle. The described embodiment of the invention which provides a facsimile recorder for use with a continuous unprepared recording sheet on which are produced marks varying from a very light grey to black in accordance with the intensity of the received signals employs a lead pencil marking member mounted for translational and rotational movement inside a hollow drum against the inner surface of which the recording sheet is secured so that the pencil member produces a helical trace on the recording sheet the pressure of the pencil and consequently the shading of the helical trace being varied by electromagnetic means in accordance with received signals. In the schematic lay-out shown in Fig. 1, a pair of gears 30 rotatably mounted on a stationary helically threaded shaft 31 and integrally united by means of a threaded shaft 32 and a slotted shaft 33, rotatably mounted in bearings 34, 38 respectively, are driven through a pair of idler gears 25 keyed to a shaft 26. by means of motor 10, clutch 12 and principal driving gear 16, rotation of the gears 30. 30<SP>1</SP>, about shaft 31 causing rotation of the shaft 32 by means of a gear 35 keyed to shaft 32 and meshing with a gear 36 of equal diameter keyed to the bushing 260 of a gear 261 which is driven at eleventenths the speed of the gears 30, by means of a further gear 263 operating through a clutch mechanism 263. The rotation of shaft 32 is utilized to impart a translatory motion to a carriage member 51, Fig. 2, the side plates 52 of which are provided with threaded openings 64 engaging the threaded shaft 32, and further provided with openings 63, 60 for the passage of the shafts 31 and 33 respectively. The latter are electrically insulated by a bushing 61, and the arrangement is such that a point (such as 70) normal to the plate 53 of the carriage member produces a helical trace on the inside of the drum member 50 due to the combined rotational and translational motions caused respectively by the rotation of the gears 30 about shaft 31 and the rotation of shaft 32 in bearings 34. The plate . 53 of the carriage member is provided with a race-way 54 in which the pencil operating mechanism is rotatably mounted by means of ball bearings 84, Fig. 6, the mechanism comprising a plate 75 carrying a conical housing 87 through an opening 88 in the apex of which a lead pencil 70 is urged into contact with the inner surface of the drum 50 when a stop member 160 is displaced from the opening. The plate 75 is provided with circularly positioned pins 77 which engage the helical thread of the stationary shaft 31 so that the pencil mechanism rotates in the raceway 54 as the carriage moves longitudinally inside the drum, this rotation providing a continuous sharpening of the pencil point. The pencil clamping mechanism, Figs. 6 and 7, comprises a hollow tube 90 the vice-like head 91 of which is compressed to grip the lead pencil 70 by means of a spring 92 which urges the head 91 against the conical end of an armature member 95 mounted for free longitudinal motion, by means of a ball race 120, to allow the pencil point to contact the inner surface of the drum when the stop 160 is displaced. The armature is provided with a winding 145 co-operating with a permanent magnet 150 and connected, at one end, to the metallic housing 87 by means of a stud 147, and, at the other end, by means of an insulated stud 141 to a slip ring 131 insulated from the housing 87 by an insulating member 130 contact being made with the slip ring through a brush 139 connected by means (not shown) to the shaft 33, which is insulated from the carriage by the insulated bushing 61, and to which the received picture signals are applied to vary the pressure of the pencil member and thus to produce the required variations in shading on the recording paper which is secured on the inner surface of the drum. At the termination of each recording cycle, i.e. when the carriage has moved the full length of the drum, the shaft 33 is caused to rotate in a counter-clockwise direction through an angle of about 30 degrees, Fig. 6 and a cam 170 carried thereby and provided with three ledges 172, 175, 178 operates firstly, through ledge 178, to release a clamp mechanism 186 acting on a rod 192 which is normally urged against the pencil 70 by means of a spring-loaded link mechanism 202, secondly, through ledge 175 to retract the pencil tube 90 so that the pressure of the vice 91 is released and the point end enters the opening 88 and, thirdly, through ledge 172, to allow the stop member 160, the bar 165 of which, Fig. 8, operating in the slots 167 in the carriage plates 52 is spring urged into con-. tact with ledge 172, to fall into position opposite the opening 88 and thus to determine and limit the forward projection of the pencil 70 under the action of the rod 192, the whole operation being reversed at the commencement of a recording cycle. The means for effecting the 30 degrees rotation of shaft 33 include a crank arm 311, Figs. 1, 2 and 14, keyed to the shaft 33 and provided with a pin 312 which, during the recording cycle, engages in an inner circular groove 321 in the gear 261 the arrangement being such that on completion of a recording cycle the clutch 263, Fig. 1, through which gear 261 is driven,. is disengaged by electromagnetic means.. and a brake mechanism applied simultaneously to stop the gear 262, and therefore the gears 261 and 36, so that gear 35 then rotates at high speed in the opposite direction causing the pin 312 to ride out of groove 321 and to enter groove 320 by means of the connecting groove 322, thus imparting the required rotation of shaft 33, and at the same time returning the pencil carriage to the end of the drum preparatory to commencing a further according cycle. At this stage the electromagnetic energization of the clutch 263 is reduced to remove the brake from gear 262, full de-energization being effected to engage the gear 262 with the drive shaft 26 at the commencement of the next recording cycle. Control and synchronization.-Operation of the recorder in response to received picture and synchronizing signals is controlled by the elements shown at 14, Fig. 1, in which the cams 502 and 503 rotated at the same speed as the gears 30, 30<SP>1</SP> by means of worm 21 keyed to the main driving shaft 15, operate contacts 504 and 505 respectively, the former contacts interrupting the circuit of the winding 145 of armature 95, Fig. 6, for about 1/9th of a revolution of the pencil carriage (i.e. as the pencil point passes over the surface 366 of the clamping plate 365) and the latter contacts interrupting the synchronizing circuit, Fig. 25, as the pencil passes the centre of surface 366, and remaining open for 180 degrees of rotation. The synchronizing circuit' which comprises an oscillator 700, Fig. 25, operating at a frequency of about 13c/s and controlled by a variable reactance valve 703 in accordance with the voltage across condenser 711 applied to its control grid, this voltage being derived from the received synchronizing signals through diode 710, supplies control signals at 701 which are combined with further control signals, generated by a photo-electric cell 623, Fig. 1, co-operating with a light source 620 and chopper disc 20, the two set of control signals being rectified (by means not shown) and fed to slip rings 610, 611 on an electromagnetic clutch 12 the driving torque of which is infinitely variable and depends on the algebraic sum of the applied control signals and the arrangement being such that this torque is a maximum when the contacts 505 interrupt the synchronizing circuit at the centre of the received synchronizing signal. Paper feed mechanism.-The paper feed mechanism, Figs. 19, 20, 21, comprises a supply roll 250a from which the paper 250 is drawn by the driven feed roll 350, suitable pressure for drawing and feeding the paper being provided by a spring-loaded pressure roll 351. The mechanism operates to feed the paper into the interior of the drum 50 by means of a guide path formed by a guide recess 362 in a plate 360 under which is supported a clamping plate 365 provided with a guide surface 367 and a curved surface 366 which matches and completes the inner surface of the drum. The clamping plate, normally is spring-urged upwardly by means of springs 394 provided around pins 380 secured to the plate 365 and acting between crank arms 392, Fig. 22, keyed to a shaft 391, and nuts 390 carried by the pins 380, so that the paper is clamped to prevent motion with respect to the drum during the recording operation. During the feeding of the paper the clamping effect of plate 365 is released by clockwise rotation of shaft 391, this rotation being automatically effected at the end of a recording operation (or, if desired, manually by depression of a crank 402 keyed to shaft 391), the paper then being free to emerge from the drum between a further recess 363 in the plate 360 and the curved surface 411 of the picture viewing bed 410 at the end of which a knife 425 operates to cut-off the' recorded picture or, alternatively, the paper may be rolled upon a take-off roll. In a modification the paper feed mechanism employs a pair of feed rolls and a pair of synchronously operated draw rolls which ensure that the paper is locked at each end thus fulfilling the clamping function of