US2464618A - Facsimile synchronizing control - Google Patents

Description

J. R. SHONNARD ET AL 2,464,618

FACSIMILE SYNCHRONIZING CONTROL March 15, 1949.

2 Sheets-Sheef'l Filed Sept. 7, 1.945

JOHN R. SHONNARD GEORGE W. KAYE v INVENTORS A 77UP/Vf Y March 15, 1949.

J. R. SHONNARD ET AL 2,464,618

FACSIMILE SYNCHRONI ZING CONTROL Filed Sept. 7, 1945 2 Sheets-Sheet 2 JOHN RSHONNARD GEORGE W. KAYE 28 INVENTORS BY y 6 fl77v/P/V fy' Patented Mar. 15, 1949 UNITED STATES ATENTJ' OFFICE FACSIMILE SYNCHRONIZING CONTROL Application September '7, 1945, Serial N.'61'5,'006' 9 Claims.

This: invention relates to telegraph machines and: more especially to driving and phasing arrangements for facsimile scanning drums and th'e like';

In the operation of facsimile systems employmg rotating scanning drums, it is usually requisite' before'the start of a transmission period to phase the drumsat the transmitter and receiver',.'even though the drums otherwise would run in perfectspeed synchronism. This phasing operation is particularl important where one of the drums is comparatively heavy, or where the .drum'rotates at sucha high speed as to have considerable inertia. This problem of phasing has been found to be particularly difficult with large or heavy drums because of the comparatively great and sudden load which is placed: upon the driving mechanism at the instantzof' phasing. Heretofore, the phasing operation has required almost. an instantaneous change from no loadto full load on the drivingmotor and on the clutch between the motor and the-drum. Since such clutches are usually of. the slip-friction type, it is clear that this sudden change from no load to full load is represented-bya considerable slip in the clutch with a con'sequent undesirable change in phase between-:thereceivedphasing impulse and the actualangular phase of the drum.

There is disclosed in U. S. Patent #2,42l,438, aznovel'form. of drive-coupling between a slipfriction clutch and a scanning drum whereby thex-load on the clutch of the driving. motor is -materially reduced during phasing operations and the like.

Accordingly, it is a principal object of the present invention to provide an improvement on the. clutching and phasing arrangement disclosed insaid U. S. Patent #2,421,438.

Another object is to provide a drive-coupling between a motor and a scanning drum or-the like which under certain conditions, is allowed to coast-freelyin conjunction with novel means ion-imparting positive driving force to the coastin-g drum at-timed intervals.

Another object is to provide an improved phasing control mechanism whereby a scanning drum can coast while its associated driving clutch is declutched, and wherein special means are providedto insure that the coasting speed does not drop below a certain amount when the clutch is subsequently operated to clutching position.

A.-feature of the invention relates to a drive-- coupling between a motor and; a scanning drum,

including- 1a slip+frictionzclutch .having i an 1ele.-5-

ment which can be selectively stopped, said 'element being coupled to the drum'by a special-onc way latch, whereby undercertain conditions, the drum can freely coast; in conjunction withan other member frictionally driven fromsaid clutch and having automatically operable means for imparting positive driving torque" to the drum to maintain its coasting speed above a predetermined amount.

A further feature relates to a novel combination of slip-friction clutches and latchi'ngcontrol means whereby a'scanning drum orthe like can be selectively clutched to a driving shaft'with a minimum of slippage or lost motion between the drum and the driving-shaft, and --with a minimum of load on the driving motor at the instant of clutching.

A still further feature relates to the novel or-' ganization and'relativelocation and intercom nection of parts which cooperate'to provide an improved and highly 'accuratephasing controlarrangement for telegraph machines, facsimile scanners and the like."

Other features and advantages not particularly enumerated will be apparent after a condrum driving and coasting control arrangement 1 according tothe inventiom: Fig. 2 is a right-hand end view of the drum" of Fig. 1.

Fig. 3 is an exploded perspective view to show more' clearly the construction of' the secondary or coasting control clutch. I

Fig. 4 is a perspective'view'of part of Fig. 1 to show how the secondary clutch is momentarily released during each revolution-of the I drum shaft.

Fig. 5 is another viewof- Fig. 4.

Fig. -6 is a detailed view,"partly sectional, along 3 prises a set of three friction discs 8, 9 and I0. Discs 8 and 9 are appropriately fastened to shaft 2, while disc II] is not connected to the shaft but is driven by frictional engagement with discs 8 and 9. Firmly attached to member I is a rigid stop arm II, which has an inclined trailing face l2. The stopping of disc H3 is controlled by the armature I2a of an electromagnet l2b which magnet can be normally continuously energized so as to maintain its armature 12a out of the path of stop arm ll. When disc Ill and arm II are released for rotation, said arm is adapted to engage the left-hand end of a latch 13 which is pivotally mounted on a pin M in a slotted uide or stud I5, rigidly fastened to the drum driving plate [6. By means of a suitable spring (not shown), the latch I3 is normally held in the position shown in Fig. 1.

Plate I6 is fastened to drum shaft l! which is journalled at opposite ends in suitable ball bearings in standards l8, l9. Preferably, the righthand end of shaft I! is provided with an end thrust ball bearing and the proper pressure being obtained by a suitable spring (Fig. between the member l8 and a shoulder on shaft ll. Shaft 11 carries the usual lead screw 28, and at its right-hand end is slotted at 2i, the scanning drum 22 being slidably keyed thereto so that as shaft I! turns, the scanning drum also turns and advances along the shaft as determined by the pitch of the lead screw thread 29. For a detailed description of a preferred drum and lead screw arrangement, reference may be had to U. S. Patent No. 2,138,784, the disclosure of which is expresslyincorporated herein by reference.

Plate I 6 has another latch member 23 pivotally mounted on a pin 24 and within a radial slot on the periphery of plate It (Fig. 4). By means of a suitable biasing spring (not shown), the latch 23 is normally held in the position shown in Figs. 1 and 4, where it rests in a notch between adjacent teeth 25 on a collar 26 which forms part of the secondary or coasting control clutch. As shown in Fig. 6, collar 26 is arranged to be frictionally driven b means of a friction plate 21, which is secured by screws 28 to the plate 29 forming part of the main clutch member 9.

As shown more clearly in Figs. 1, 4 and 5, the left-hand face of member l8 carries a cam 30 which is adapted to engage the tail portion 3! of latch 23, so as to tilt the latch to the position shown in Fig. 5 whereby the members 16 and 26 are decoupled. Under these conditions, and assuming that clutch member Ill is stopped, the scanning drum 22 is disconnected from the drive shaft 2 and is free to coast for a fraction of a revolution permitting the drum to decelerate. In the meanwhile of course, shaft 2 and member 26 are in continuous rotation. However, when the tail 3| of latch 23 leaves cam 30, the members I6 and 26 are so displaced as to prevent the latch from re-engaging the same notch, thus causing the drum to slip back until the latch drops into the next succeeding notch. This therefore prevents the drum 22 from coasting down below a certain speed, and the number of notches provided controls the total displacement or deceleration permitted per revolution. In other words, in the absence of the auxiliary clutch, the drum 22 might, because of friction, experience a drop in coasting speed to such an amount so that when arm II is subsequently released, the difference in normal continuous running speed of shaft 2 and the lowered coasting speed of drum 22,

would subject the shaft 2 to a comparatively sud- 4 den load, with resultant slipping between the clutch members 8, 9 and It]. This slippage may result in an improper phasing between drum 22 and the corresponding scanning drum with which it is to be synchronized at the opposite end of the system.

The operation of the mechanism is as follows. When the latch 23 rests in one of the notches between adjacent teeth 26 as shown in Fig. 4, the collar 26 tends to drive the lead screw I! by means of plate It, and at the same speed as shaft 2. When cam 30 engages latch tail 3!, latch 23 is tilted out of engagement with collar 26 and the speed of drum 22 will be lowered slightly because of friction in its bearings and the like.

: ber 2'! and shaft 2.

In the particular arrangement illustrated, the member 26 has eight equally spaced notches so that the drum 22 can never freely coast for more than one-eighth of a revolution. Therefore, the speed of drum 22 will always be within or of the normal running speed of shaft 2. If desired, the positive driving of the drum by shaft 2 and member 21 may be such as to overdrive the drum thus likewise enabling the latch l3 to catch up with stop arm l 1.

As the latch 23 steps from notch-to-notch, the main driving latch IE will come into contact with the arm I l, and as soon as this position is reached the plate is will be driven continuously by means of arm II and latch l3. By reason of the fact that the stop arm I! picks up the load of the drum when the drum is coasting within 80 or 90% of the normal running speed, the shock on clutch I will be very slight and there will be little or no slippage. In fact, with the particular arrangement disclosed, the slippage. can be reduced to a substantially negligible amount, and if desired a greater number of notches may be provided in the member 26 to reduce even further the possibility of slippage.

While one particular embodiment has been illustrated and disclosed herein, it will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A phasing arrangement for telegraph apparatus such as a facsimile scanning drum, com prising a driving shaft, a slip-friction clutch between said driving shaft and drum, means to declutch the drum from the driving shaft to allow the drum to coast freely, and means to impart positive driving torque to the drum at intervals while coasting to maintain its coasting speed above a predetermined amount until said declutching means is again operated to cause clutching of the drum to said shaft.

2. A phasing arrangement for telegraph apparatus such as a facsimile scanning drum, comprising a continuously running driving member for said drum, a driving connection between said member and said drum, said connection including a device which can be stopped While allowing the drum to coast freely with relation to said driving member, said device when released allowing the driving member to impart positive driving torque to the drum, and other means to maintain said coasting speed above a predetermined amount while said device is stopped.

3. A phasing arrangement for a telegraph device such as a facsimile scanning drum, comprising a continuously running driving member, a scanning drum having substantial rotational inertia, a controllable clutch for applying power from said driving member to said drum, a one way positive latch coupling between said driving member and said drum and which also allows said drum to coast freely with relation to said driving member when the said drum is declutched from said driving member, and means independent of said latch coupling to impart positive driving torque at intervals to said drum while coasting to maintain said coasting speed above a predetermined amount.

4. A driving arrangement for a, telegraph apmain clutch, an auxiliary clutch having a member l positively driven by said shaft, and means for coupling the drum to said member at intervals while the drum is coasting and while said decoupling means is decoupling the drum from said main clutch to maintain the coasting speed above a predetermined amount.

5. A driving arrangement according to claim 4 in which said member comprises a toothed ring, and the last-mentioned means includes a shiftable member rotatable with the drum and movable into and out of engagement with said toothed ring.

6. A driving arrangement for a telegraph device such as a facsimile scanner, comprising a continuously running driving shaft, a driven shaft for said drum, a scanning drum connected to said driven shaft, a slip-friction clutch between said two shafts and having a member frictionally driven from said driving shaft, a oneway latch device between said member and said driven shaft for imparting a. positive torque to said driven member while allowing said drum to coast when said member is stopped, and another clutch device for coupling said driven shaft iii) to the driving shaft at regular intervals during each coasting rotation of the drum.

7. A driving arrangement for telegraph apparatus such as a facsimile scanning drum, comprising a, continuously running driving shaft, a driven shaft for said drum, a slip-friction clutch having a member frictionally coupled to the driving shaft, a stop arm carried by said member for stopping said member without stopping the driving shaft, a driving plate fastened to the driven shaft, a pivoted latch member extending from said plate into the path of said stop arm, a toothed ring frictionally coupled to said driving shaft, and another pivoted latch member carried by said plate and selectively movable into engagement with said teeth to impart a positive torque at spaced intervals to said drum when said arm is stopped.

8. A driving arrangement according to claim '7 in which stationary cam means is provided for engaging said other latch at a predetermined point of the drums rotation.

9. A phasing arrangement for a telegraph device such as a facsimile scanning drum, comprising a continuously running driving source for said drum, means to drive the drum from said source preliminarily to the receipt of a phasing signal, means to disconnect the drum from said driving source to allow it to coast freely, means responsive to the receipt of a phasing signal to control the connection of said driving source to said drum while the latter is coasting, and means to maintain said coasting speed above a predetermined amount pending the receipt of said phasing signal.

JOHN R. SHONNARD. GEORGE W. KAYE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,105,897 Towne Jan. 18, 1938 2,138,784 Cooley et al Nov. 29, 1938 2,255,869 Ridings et a1 Sept. 16, 1941

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