US2492621A - Facsimile synchronizing device - Google Patents

Description

Dec. 27, 1949 A. G. COCJLEY FACSIMILE SYNCHRONIZING DEVICE Filed March 12, 1948 INVENTOR.

Patented Dec. 27, 1949 2,492,621 FAG SIMILE SYNCHRONI-ZING DEV-ICE Austin G. Cooley, New York, N. Y., assignor to Times Facsimile Gorporatiom'New York, ELY, a corporation of New York Application March 12, 1948, Serial No. 14,456

'1 Claims. 1

This invention relates to telefacsimile apparatus and more particularly to the motor drive and phasing mechanism employed for starting and driving the drum or other scanning member in controlled speed and phase relation.

One object of the invention is to provide an improved and eflicient facsimile drive which is adapted to start a relatively large picture drum or scanning member from rest, bring it into proper phase relationship and rotating at a desired constant speed in synchronism with the machine with which it is connected.

Another object of the invention is to provide an improved phasing mechanism for facsimile or telephoto apparatus in which the phasing load on the motor is low. 7

Another object of the invention is to reduce the power required to drive the scanning mechanism of a facsimile machine to a minimum.

A further object of the invention is to provide an improved drive arrangement for the picture or recording drum of apparatus of the character described employing a driving motor of a nonsynchronous type and a second motor of a synchronous type so interconnected that the driven element rotates at a speed determined by the synchronous motor.

A still further object of the invention is to provide an improved drive arrangement for apparatus of the class described which is adapted to bring the driven element up to synchronous speed and eiiect a phasing operation automatically in response to the closure of control switches without requiring manipulative skill to start and phase the facsimile equipment.

Still another object of the invention is to provide driving mechanism for the drum of a facsimile machine which will permit the drum to be stopped or held stationary during or after the phasing operation without losing phasing adjustment.

Other objects and advantages of the invention will appear from the following detailed description of the embodiment thereof shown in the 45 accompanying drawings, wherein Fig. 1 is a perspective view, partly in section, of a preferred construction. In this view the element to be phased in its angular position and driven at constant speed is shown as a drum or cylinder of a facsimile machine.

Fig. 2 is a perspective view showing the ,relation of the driving and phasing elements of Fig. 1 in 'a-simp'lified and exploded form in order to show more clearly the underlying principles of construction.

In'telefacs'imile apparatus in general use, picv ture transmitting and recording drums are em-.

ployed which are driven at a constant speed and in a desired phase relation. In this manner the drums of the transmitter and recorder are operated in rotational synchronism and in phase. In some apparatus other types of scanning devices are employed instead of the drums, which are also required to be operated in controlled speed and phase relation.

In order to maintain the drum or scanning member of the recorder operating at the same speed as that of the transmitter, the respective scanning members may be driven by synchronous motors, each controlled by a tuning fork or other frequency standard or connected to the same alternating-current system. Another synchronizingarrangement involves transmission of a low-frequency carrier from the transmitting .station to the receiving station and synchronizing the speeds of the two motors by the carrier. In most synchronizing systems, the sychronous motor is driven by a vacuum tube amplifier. Consequently it is desirable to reduce the size of the synchronous motor element as much as possible by reducing the load imposed thereon by the drum or scanning member. However, if the drum is started and stopped for phasing,

,usually a friction clutch is provided and considerably more power is required to prevent stalling the synchronous motor by the clutch load than for merely maintaining the operating speed of the drum. At the present time, facsimile equipment is being used which employs relatively large picture drums or rotating members driven at relatively high speeds and therefore requiring increased driving power.

It has been found impractical to connect these taining the drum or scanning member rotating through a secondary clutch or other auxiliary drive means but the construction is rather com- .plicated, particularly as it was necessary to insure 0 that the auxiliary cl-utchwould not drive the drum at .a speed greater than synchronous speed or provide in some manner for bringing the drum.

tosynchronous speed.

. In accordance with theembodiment cf the vention'lllus'tra'ted, the synchronous motor is con- It has been pro-- posed to reduce the :clutch friction load by mainnected to a rotatable phasing member and a driving connection in the form of a latch is provided between the phasing member and the drum so that the drum is coupled to the phasing member in one predetermined angular position of the drum relative to said member. Further means is provided for overdriving the drum so that when the phasing member has been released or phased and is rotating at synchronous speed, the drum will catch up to the phasing member and rotate at the synchronous speed of said member with the driving load taken by the motor employed for overdriving the drum. The driving connection between the rotatable phasing member and the synchronous motor or other constant-speed control member enables the phasing member to be stopped for phasing without stalling the synchronous motor. This driving connection is preferably of a type which positively controls the speed of the phasing member without imposing more than a minimum load on the synchronous motor. A variable speed motor may be employed for overdriving the drum or the synchronous motor may be geared through a direct drive shaft to the drum with an interposed friction slip clutch. In accordance with a further feature of the invention, the synchronous motor is preferably connected to the phasing member through a worm and worm gear of a type which prevents torque from the phasing member overdriving the synchronous motor above synchronous speed, such as an irreversible worm-gear drive or a worm-gear drive designed to limit the torque applied to the synchronous motor shaft.

Referring to the drawing, the drum I of a facsimile machine is mounted on a shaft 2 for rotation at a constant speed during transmission. The drum I may be a picture drum of a facsimile transmitter, in case the transmitter is phased with a remote recorder, or may be the recording drum of a recording facsimile machine where such recorder is phased with a remote transmitter. It is further understood that the drum I is intended to represent any rotatable scanning element of this character which is to be controlled in speed and phase relation. The shaft 2 is shown as provided at the outer end thereof with a drive gear 3 meshing with a drive pinion 4 for the purpose of starting the drum I from rest and bringing it up to a desired rotative speed. A shaded-pole motor or other variable speed motor may be provided for overdriving the drum through the gears 3 and 4, or other suitable driving means may be provided for initially accelerating the drum I and providing all or a part of the torque required for the driving load. An induction motor having a high slip-speed characteristic may be used as a drive motor since it has a fairly constant torque over a considerable range of speed. 7 p

In order to control the speed and phase relation of the drum or scanning member I, a rotatable phasing member 6 having a projecting lug I is provided in the specific embodiment shown by way of illustration. The phasing member 6 is coaxial with the drum or scanning member I, and may be journaled on the shaft 2. The position of the phasing membermay be controlled by a timed phasing current impulse, as shown for example in my prior patent, No. 2,275,249 granted Mar. 3, 1942. In order to stop the phasing member 6 in a predetermined phase relation (predetermined angular position) and release the same in re- V sponse to the receipt of a phasing pulse, means such as a pivoted latch memberQ controlled by 4 an electromagnet 9 may be provided. As shown, the latch member 8 is disposed in the path of the lug I and stops the rotation of the phasing member 6 until the latch is retracted by energization of the magnet 9 upon receipt of a phasing current pulse applied to the conductors ID.

The phasing member 6 is driven at a constant synchronous speed by means described hereinafter and serves to control the speed of the drum I by means of a phasing coupling means I2. In the embodiment shown, the coupling means I2 is in the form of a latch operative to couple the scanning means I and phasing member 6 together in one relative angular position of the two members. It preferably consists of a two-Way double-jointed latch pivoted on the scanning member and adapted to engage the lug I of the phasing member 6. As shown, the coupling means I2 comprises a fixed base or supporting element I3 rotating with the drum, a first pivoted latch member I4 and a second latch member I5 pivoted on the member I4. The latches I 4 and I5 are arranged to pivot in opposite directions, as indicated by the arrows in Fig. 1. A strong spring I6 is interposed between the members is and I4 so that the latch can tilt by the pivoting of the member I4 only in response to the application of considerable force. On the other hand a light spring I1 is interposed between the members I4 and I5 so that the member I5 can tilt to permit the lug I of the phasing member 6 to pass the latch in a clockwise direction without imposing substantial drag on the phasing member. Thus the phasing member 6, if driven at constant speed, will serve to hold the drum I at the same speed, through the coupling connection I2 when thedrum is overdriven by the shaft 2. When the shaft tends to run above synchronous speed, the connection I2 engages the lug I, the spring I 6 being sufficiently strong to prevent buckling of the latch I3, I4 by the driving torque. However, if excessive torque is applied between the drum I and the phasing member 6, either while the drum is rotating or as a result of turning it by hand when the phasing member 5 is stopped by the latch 8, the pivoting of the member I4 of the latch will prevent damage to the coupling I2.

The rotative speed of the phasing member 6 is maintained at the constant synchronous speed by means of a motor 2!; or in case a fluctuating scanning speed is used, as explained for example in my prior Patent No. 2,404,566, the motor 2! maintains synchronism of the member 6. The motor 2! is preferably a synchronous motor which is synchronized with the driving motor of the remote facsimile machine, as by means of a transmitted carrier or by the use of common or synchronized sources of alternating current for driving the motors, as well known to those skilled in the art. As shown, the motor 2i is connected to the phasing member 6 through a worm 22 and worm gear 23, the latter being connected to a driving sleeve 24 surrounding the shaft 2. The

Worm gear 23 is shown as clamped to the sleeve 24 by a clamp 25. The sleeve 26 in turn is keyed to a ratchet gear 26, the teeth of which are engaged by a pivoted pawl 21 on the phasing member 6, The pawl 27 is pivoted on a stud 28 and is urged by a spring 29 against the circumference of the toothed ratchet gear 26. The

pawl and ratchet connection shown is provided for the purpose of permitting substantially free rotation of the synchronous motor rotor when i the phasing 'member 6 -is stopped without imparting a heavy frictional drag on the Synchro aaamnar.

n'ous moron. while at: the same: time? the phasing members is positively heldbaels (to; synchro'e nous-ispeedf)" by the synchronous motor 2 It: When reieasem for rotatiom upon; the receipt of the phasing pulsccontroliing:the'latch 8:

=When -the phasingmembcr fi'is stopped by the latch 8, the motor" 24 drives the? ratchet gear im a clockwise direction; the' pawl H slipping overthe teeth inthe gear; When the phasingmembei 'B is releasedrfor-rotation however, since:

thc f-riotion load is=sma ll thee pressure of: thepawlon; a teeth of the gear 26: is suffic'iently great toei'fect a ratherpositive: drive I between the said-cgear and. the phasing:- member 6' on which the paw l is pivoted. In this manner the' phasing member is operatedat the: synchronous speed of tl' e drive shaft substantially instantaneously after: thephasing pulse is receivedr- The driving power of the pawl= and ratchet in this; direction? is determined by the shape: or thepawl andmatchet teeth and the pressure ofthe spring and thus is not avariable factor like the: friction; drive of the slip clutchheretofore used.- In the opposite direction; when the over-drivetem'lsv to rotate the drum and phasing. member 6 above synchronous speed, the pawl and. ratchet teethare shapedto providepositive'torque transmission so. that. the' motor 2I- positively limits or retards the phasing. member to the desired synchronous speed.

The general" principles, underlying the inven-- tion will bereadily understood.- from the. simpli'fiedv drawing? of Fig. 2, whichillustrates the essential relation between. the driving. phasing and scanning members of Fig. L in. a. simplified form. As. shown, referring to Fig. 2 and usingcorrespondi-ngi reference characters. to. denote corresponding elements of the construction, the drum: l is. driven. throughthe shaft 2 by overdrive'means operative to bring it up from rest to the desiredspeed and tending to rotate the drum above synchronous speedl. Obviously, in stead of a separate induction or other" variable speed, motor; the" shaft 2 may be driven from the" synchronous motor 21 through a slip-friction clutch; The drum IE is maintained at constant speed by the retarding force applied" through the coupling means I 2 and the lug I of the phasing member 6 which is driven at constant. of syn.- clironizecf speed by the. synchronous motor 2!.. Thus", when the drum I catches up to the phasingfmember's iand the coupling; means I2 engages the" lug T, the drum is ret'arde'd" and constrained to operate at the synchronous or controlled speed. of the phasing member" Iii The driving connection" consisting" of the pawl and ratchet 26, 2'! permits. the continued operation of the synchronous motor 21, when the phasing member 6 is latch'ed? during the phasing" operation This is required because the drive for the phasing member must be: operating at synchronous speed at the instant the phasing member is released by the phasing pulse. However, the pawl and ratchet provide a. drive connection which has a minimum: frictional drag when the phasing member It is stopped, and which picks up the phasing mernber with. negligible slippagewhen it is released.

In accordance with another feature of the invention, the worm- gear drive 22, 23 is designed to not only avoid undue loading of the synchronous motor 2! by the drum drive but also limit the reverse torque on the motor tending to pull it out of synchronism. The friction between a worm and worm gear depends upon load and speed? well? as" the materiahandi profiles or the described; the? helix angle or the thread (the angle of thread with a: line' at right angles? to the axis of the worm) should betor the order of 7 to 12 degrees. As noted, this angle for-"optimum: results will change for different materials, speeds; and so forth but improvement Willi be obtained generally in th'e: stated rangefor' 'or dina'ry gear materialsr; Inf this manner, the size. of the synchronoustmotor- 24' may be reduccd: to a minimumasince 17h6:-$1'18;1li1lg and accelerat-- ing torques produced bytheoverdrive are smaliz.

I-n starting, and phasing- .the= drumi'or scanningmember' It, thecircuit of the synchronous motor 2|? is closedandrthe motor brought to synchrot nous speedv If, the, phasing member 6' is locked: by the phasing. latch= 1-, the ratchetmechanism 26,.2-1 permitsethe synchronous motor-2dr topper ate at-synchronous speed without appreciable drag because of?- the locking. of the phasing. memeber 6. When the phasing.pulse-isreceived, the latchmember. 8 is retracted from the phasing lug, 1,. and the phasing member 6- rotateswith:

the ratchet gear 21 at synchronous speech. The drum is brought up to speed by closing its a motor circuit,. either before or after phasing, and tends to rotate above synchronous speedr. When thedrum I catches upv to thephasing. member 5,. and the coupling. means I-2 engages the. mg I oi said member,. the drum. I is retarded. by... the phasing member Ii and: continues to rotate in the desired phase relation and at synchronousspeed Itwill be apparent that the invention-provides an efiective phasing. mechanism in which v a large high-speedscanning member can be: brought to the desired phase relationwith a. phasing mem- 'ber. controlled by the phasing. pulse, and v maintained at desired synchronous. speed. by means.- of asmallisynch'ronous motor.. Since the load.onthe synchronous. motor is small, even when the phasing member is stopped for. phasing. there is nov possibility of stalling. the motor; On the other hand, the relatively heavy power required to start and. rotate the drumor scanning member I is obtained? from. an auxiliary power source which neednotibe closelyregulated as to speed, such as a variable-speed. shaded-pole motor.

It will also be noted that in case of a variable scanning speed'of' transmitter andrecorder, as employedinthe secrecy or scrambler equipment disclosed in my above-mentioned Patent No.

2,404,566,. the motor il 'when, synchronized with the, driving mechanism'of the remote machine is adaptedito control the rotationofth'e' drum I in accordance with variations in the-'rotative speed of the motor. The driving mechanism according to the invention has the advantage that rapid, wide-range variations. in the speed of the scanning means may be controlled by a small motor 21' of" the" synchronous. type. The term synchronous speed is to be construed as. including a variable speed'wliich is synchronized with tn'e'fluctuationsf in speed of a second scanner or scanning drive motor.

A further advantage of the mechanism described above resides in the fact that the drum I is movable with respect to the scanning memher 6 except when actually transmitting or re cording and the drum may be actually stopped during or even after the phasing operation without reouiring re-phasing of. the member 6.

While I have described in detail a preferred 7. embodiment of the invention for the purpose of explaining the underlying principles thereof, such description is only by way of illustration. Various modifications of the invention will occur to those skilled in the art, and may be made without departing from the scope thereof.

I claim:

1. In a telefacsimile machine provided with a rotatable scanning member to be driven at predetermined speed and phase relation, in combination, motor means in direct driving relation to said scanning member tending to drive the scanning member above synchronous speed, a rotatable phasing member, means including said phasing member for controlling the angular position of the scanning member in operation, means for supporting said phasing member for rotation independent of said scanning member, means for stopping the phasing member and for releasing the same for rotation when a phasing pulse is received, a second motor means operating at synchronous speed'and connected to the rotatable phasing member to maintain the rotative speed of the scanning member at synchronous speed and a drive connection between said second synchronous motor means and said phasing member embodying a pawl and a ratchet gear engaged thereby to allow rotation of the motor shaft when the phasing member is stopped for phasing control, the teeth of said pawl and gear being shaped to provide a positive light driving torque from said synchronous motor means on the phasing member when it is released.

2. In a telefacsimile machine provided with a rotatable scanning member to be driven at predetermined speed and phase relation, in combination, a motor which varies in speed in accordance with its load connected to and normally tending to drive said scanning member at a speed greater than the predetermined speed, a rotatable phasing member connected to said scanning member in such manner as to retard its speed when the phasing member and the scanner member have a predetermined phase relationship, means for supporting the phasing member for rotation independent of said scanning member, means for stopping the phasing member and for releasing the same for rotation when a phasing pulse is received, thereby controlling the angular position of the scanning member when the overdrive of the said member causes it to assume said predetermined phase relation to said phasing member, and means for continuously maintain ing the rotative speed of said phasing member at said predetermined speed during operation and thereby limiting the rotation of the scanning member to such speed.

3. A facsimile driving and phasing mechanism according to claim 2 in which the means for maintaining the rotative speed of said phasing member at said predetermined speed. comprises a synchronous motor geared to the phasing member through an irreversible worm drive for limiting the loading of said synchronous motor by the over-drive of the variable-speed motor.

4. In a telefacsimile machine of the character described, in combination, a rotatable scanning member tending to rotate above synchronous speed, a rotatable phasing member connected to said scanning member in such manner as to retard its speed when the scanning member and phasing member have a predetermined phase relationship, means for supporting said phasing member for rotation independent of the scanning member, means for stopping the phasing member and for releasing the same for rotation when a phasing pulse is received, thereby controlling the angular position of the scanning member when in said predetermined phase relationship to said phasing member, and motor means for rotating the scanning member and for controlling the rotative speed of the phasing member to obtain a predetermined synchronous speed thereof and of said scanning member.

5. In a telefacsimile machine provided with a rotatable drum or scanning member, in combination, a rotatable phasing member coaxial with the drum when the same is coupled to the phasing member and a pawl-and-ratchet drive connection between the synchronous motor and said f phasing member to permit the synchronous motor to run when the phasing member is stopped while retarding the phasing member to the speed of said motor when said member is released for rotation.

6. A driving mechanism for a facsimile ma chine according to claim 5 in which the drive connection consists of a pawl and ratchet gear having teeth shaped to provide a light positive driving torque from the synchronous motor to said phasing member and relatively heavy positive retarding torque when the speed of the phasing member tends to exceed synchronous speed.

'7. A driving mechanism for a facsimile machine according to claim 5 in which the phasing member is connected to the synchronous motor through worm gearing in which the thread helix 1 angle of the teeth on the driving worm of the motor is of the order of '7 to 12 degrees.

AUSTIN G. COOLEY.

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

UNITED STATES PATENTS Disclaimer 2,492,621.-Austin G. Cooley, New York, N. Y. FACSIMILE. SYNCHRONIZING DEVICE. Patent dated Dec. 27, 1949. Disclaimer filed Jan. 9, 1951,

by the assignee, Times Facsimile Corporation; the inventor consenting.

Hereby enters this disclaimer to claims 2 and 4: of said patent.

[Oficial Gazette F ebi'uarg 6, 1.951.]

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