US2839603A - Facsimile telegraph scanning mechanism - Google Patents

Description

June 17, 1958 J. v. FOLL ETAL FACSIMILE TELEGRAPH SCANNING MECHANISM Original Filed July 11, 1955 @ZKFO LL United States atent Ofilice 2,839,603 Patented June 17, 1 958 FACSIMILE TELEGRAPH SCANNING MECHANISM John Victor Foll, Peter William Sieber, and Alan Arthur Kirchel, Beckenham, England, assignors to Muirhead & Co. Limited, Beckenham, England Original application July 11, 1955, Serial No. 521,151. Divided and this application November 13, 1956, Serial No. 621,745

3 Claims. (Cl. 178-71) This application is a division of our co-pending application Serial No. 521,151.

The invention relates to facsimile mechanisms such as are employed in facsimile transmitters or receivers, wherein the sheet containing the matter to be transmitted, or the sheet upon which the reproduction is to be made, is mounted upon a drum for the purpose of being scanned, the drum being driven rotationally and arranged for relative axial movement with respect to an optical system. The sheet is usually attached to the drum either by longitudinal clips which engage the two ends of the sheet or by means of a transparent spring-tensioned wrapper. In either case it is desirable that the drum be held in a particular rotational position during the unloading and loading operations in order that the clips may readily be placed in position or, in the case of a transparent wrapper, that the free end of the wrapper is presented in a convenient position for manipulation and loading.

It is essential that the scanning drums in the transmitter and receiver respectively should rotate in correct angular relationship with respect to each other and in exact synchronism. Consequently the drums and the related mechanism must be manufactured to a high degree of precision. Each drum with its arrangement for holding the sheet is of substantial weight and it is desirable that means be provided to ensure that the speed of the drum has been reduced to a low level before it is stopped automatically in the desired position for loading and unloading.

In certain applications of facsimile telegraph machines it is desirable that the driving motors of the transmitter and receiver should run continuallyin synchronism and that either drum may be stopped, re-started and synchronized with the other by automatic means. The acceleration and synchronization of the drum which is being restarted must be carried out without imposing such a load on its driving motor as will pull it out of synchronism.

The invention consists of a facsimile scanning mechanism having means for stopping the drum is a desired position, so arranged that they are prevented from engaging until the speed of the drum has been reduced to a low level, and means operative upon disengaging the stopping means to accelerate the drum to a speed slightly above its normal speed until it is in correct angular relationship with the remote scanning drum.

The invention will be further described in conjunction with the accompanying drawings in which:

Figure 1 shows an embodiment of the invention.

Figure 2 is an enlarged view of a detail of the embodiment of Figure 1.

Figure 3 shows a modification of the invention.

Figure 1 shows an elementary scanning mechanism in which a rotatable message drum 35 is slideably mounted on a hollow shaft 36 and is moved axially by part nut 37 pivotally mounted in one end of the drum engaging the lead screw 34 extending within the hollow shaft, through a slot 38 in the hollow shaft, the lead-screw being driven by gear wheels 58, 59, 60 and 61, at a speed different from that of the drum to effect an endwise movement of the drum. The part nut 37 may act as a key to cause the drum to rotate at the speed of the hollow shaft or alternatively other axially-slideable keying means may be provided.

Attached to the hollow shaft is gear wheel 39 driven by gear wheel 40 which in turn is driven frictionally by clutch plates 41 keyed to shaft 42. Shaft 42 is driven by a gear wheel 43 mounted thereon. Gear wheel 43 is one of a train of gear wheels 43, 44, 45 and 46 driven by the synchronous motor 47. When the motor is running synchronously gear wheel 46 is driven at the designed operating speed of the drum, while gear wheel 39 fixed to the hollow shaft is driven in the same direction at a slightly greater speed (since it is slightly smaller than gear wheel 46). Gear wheel 39 has fixed to it a lug 48 which operates in conjunction with permissive latch 49 mounted on gear Wheel 46 so that whereas gear wheel 46 can rotate when gear wheel 39 is stationary, gear wheel 39 when it rotates cannot overtake gear wheel 46 beyond the point when lug 48 has caught up the latch 49. In this condition gear wheel 40 will slip between the friction plates 41.

The thrust of the friction plates 41 is applied by spring 50 the force of which can be removed by operation of the start-stop lever 51 leftwardly in which case there is no drive to gear wheel 39 and the drum 35 will stop. Associated with the lever 51 is an arresting lever 52 which, when the lever 51 is moved to the stop position, is free to engage with a rectangular hole 53 in the gear wheel 39 under the influence of a spring 54.

In the rest position of the drum, gear wheel 39 is held by the arresting lever 52 so that drum 36 is in the convenient position for fixing the message clips or operating the wrapper. In this position the drum can be moved endways to the start-traverse position, the release of the nut 37 being effected by pressing tail 55 against spring action towards the stop 56 mounted on the end of the drum. Motor 47 will uninterruptedly be driving gear 46 at the synchronous speed and in the correct phase corresponding to the associated remote telegraphic machine.

To commence scanning, the lever 51 will be moved to the start position allowing spring 50 to exert its thrust on friction plates 41 to drive gear wheels 40 and 39. At the same time the arresting lever 52 will be disengaged from the gear wheel 39. Hence the drum 35 will accelerate and rotate at a slightly faster speed than the gear wheel 46 until the lug 48 abuts against the latch 49 after which time the drum will revolve at the speed of gear wheel 46 and in correct phase and synchronism with the drum of the remote telegraphic machine. Lead screw 34 associated with part nut 37 will traverse the drum past the lens system 57. When scanning is complete and it is required to stop the drum for reloading and resetting, movement of the lever 51 to the stop position will release the driving clutch plates 41 and move the arresting lever 52 towards the gear wheel 39 to engage with hole 53 to stop the drum as it comes around by its own momentum to the required position.

In order that the impact of stopping the drum 35 is reduced to an acceptable amount, provision is made so that the speed of the drum will have reduced considerably before the arresting lever 52 engages with the slot 53 to stop the drum suddenly and hold it in its rest position (see Figure 2).

The arresting lever 52 is chamfered as shown at 62, and clearance 64 is provided between the length of slot 53 and the length of the projecting lug of lever 52, so that when the arresting lever 52 approaches gear wheel 39 rotating at its working speed, the arresting lever will fall partially into the slot 53 and the edge 63 will engage tent that the arresting lever falls into the slot sufficiently for-leading edge 65 to engage slot end 63.

In these circumstances the shock will be small enough so asto not damage the arresting lever projection as it enters the slot and holds the drum in the desired rest position.

In alternative arrangements the friction clutch may be replaced by other types of clutch capable of slip, e. g., employing a viscous liquid, an eddy current, or a magnetic or hysteresis torque.

Figure 3 shows a modification of the invention. The scanning mechanism is covered by a lid 66 which may be swung about two pivots .67 .(one of which is shown). When the 'lid is open start-stop lever 51 is in the stop position in which clutch 41 is disengaged and lever 52 is engaged with gear 39 to hold drum 35. When lid 66 is closed an extension .68 engages start-stop lever 51, which is moved to the right, thus withdrawing arresting lever 52 'from engagement with gear 39 and allowing clutch 4.1 to engage. The drum then commences to revolve and is accelerated up to a speed slightly higher than scanning speed, as previously described, vuntil latch 48 engages stop 49, when the speed of drum 35 is reduced to that required for scanning.

What we claim is:

l. Facsimile scanning mechanism comprising a message drum, a synchronous motor, gearing to transmit the drive from said motor to said drum, an optical systems, a lead-screw to produce relative axial movement between said drum and said optical system, a clutch interposed in said gearing, said gearing including agear having a slot in its face and coupled to said drum, an arresting lever having a lug adapted to engage said slot in said gear to stop said drum, a spring urging said arresting lever into said slot, a control lever arranged to disengage said clutch and then to allow said arresting lever to enter said slot when moved to the stop position, said arresting lever lug being so chamfered and of such a length in relation to the slot, that it can only fully enter said slot to stop said drum when the speed of said drum has fallen below a predetermined level.

2. Facsimile scanning mechanism, as claimed in claim 1, comprising a second gear mounted co-axially with the drum and continuously driven by the motor at the desired scanning speed, a stop mounted on said second gear, a permissive latch coupled to the gear, said gear being driven at a speed higher that the desired scanning speed, said latch and said stop being arranged so that said second gear may rotate whilst said gear is stationary but said gear can only overtake said second gear until said latch engages said stop after which the clutch slips.

3. Facsimile scanning mechanism, as claimed in claim 2, comprising a lid to cover said mechanism, said lid having an extension which engages the control lever, arranged so that opening said lid allows said control lever to move to the position in which the arresting lever is engaged with the gear and closing said lid moves said control lever to the position in which said arresting lever is disengaged from the gear.

References Cited in the file of this patent UNITED STATES PATENTS 2,288,135 Hoza June 30, 1942 2,630,495 Wise Mar. 3, 1953 2,652,448 Hunt Sept. 15, 1953

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