US2806574A - Variable escapement - Google Patents

Description

p 1957 R. A. HIGONNET ET AL 2,806,574

VARIABLE ESCAPEMENT 5 Sheets-Sheet 1 Filed Aug. 21, 1953 LI +r Nmi INVENTORS RENE HIGONNET LOUIS M.- MOYROUD ATTORNEYS p 1957 R. A. HIGONNET ETAL 2,806,574

VARIABLE ESCAPEMENT 3 Sheets-Sheet 2 Filed Aug. 21, 1953 INVENTORS A HIGONNET ATTORNEYS Sept. 17, 1957 R. A. HIGONNET ETAL 2,306,574

VARIABLE ESCAPEMENT Filed Aug. 21, 1953 3 Sheets-Sheet 3 CINVFJVTORS RENE A, HIGONNET BY LOUIS M. M YROUD M A 8 TE s om N 91 3 B my 3. 9 E

ATTORNEYS United StatesPatent O VARIABLE ESCAPEMENT Rene A. Higonnet and Louis M. Moyroud, Cambridge, Mass., assignors to Graphic Arts Research Foundation, Inc., Cambridge, Mass., a corporation of Delaware Application August 21, 1953, Serial No. 375,653

11 Claims. (Cl. 197-84) The present invention relates to variable escapement mechanisms, and more particularly to a resettable differential mechanism for type composing apparatus adapted for variably spacing the characters in a line as they are successively transcribed, the said mechanism responding to input information represented in numerical'form. 7

One object of the present invention is to provide resetting mechanism for each of the additively connected differential stages of such an escapement, whereby each stage may be returned at predetermined intervals (e. g., at the end of each line of type composition) to a fixed, precisely determined position.

Another and related object is to provide novel mechanism for returning the carriage which spaces the characters of type to a precise position corresponding to the margin of a page, the said mechanism operating upon a principle which eliminates the effects of backlash.

A still further object, with reference to type composition, is to provide a variable escapement mechanism having a plurality of input leads which may be energized in selected combinations corresponding to a numerical representation of each desired width of carriage movement. For such purposes, we prefer the binary notation, since this requires only'two discrete conditions per digit represented. The said notation is preferably introduced into the composing machine by permutation bars associated with the keys of the keyboard, and is maintained in all of the operations associated with the provision of character and word spaces in the line. Specifically, these operations involve the memory unit or register which stores the selected characters for purposes of justification, the line length accumulator, the justifier, the multiplier units which relate the information pertaining to the relative width values of the characters in any given alphabet to the set width selected for the particular composition, and the character spacing mechanism itself.

With these and other objects in view, a feature of the present invention resides in the novel use of a delayed action clutch in the rewind apparatus of each stage in a series of differentials comprising the variable escapement mechanism. Each stage has an input shaft provided with a clock spring or similar device normally urging the shaft in one direction, and a ratchet escapement mechanism. At the beginning of a line of composition the spring is fully wound. As the line of characters is progressively transcribed, one character at a time, the ratchet mechanisms associated with the input shafts operate in successive selected combinations to unwind the springs. At the end of the linea reversible motor, acting through each delayed action clutch, causes each input shaft to rotate in the reverse direction through an angle equal to the cumulative total of its previous spacing movements, thus rewinding the respective springs and returning each input shaft precisely to its original position. Thus the variable escapement, by moving in reverse, brings the character spacing carriage, which is continuously connected therewith, precisely to its original position corresponding to the margin of a page.

According to another feature, the arrangement of the differential mechanisms of the variable escapement provides an appropriate response to the binary form of input, such as is provided by the output of the multiplier unit described in the copending application of Caldwell, Higonnet and Moyroud, Serial No. 295,284, filed June 24, 1952.

The variable escapement mechanism herein described is preferably adapted to move the refiecting'element of the optical system described in the copending application of Caldwell, Serial No. 148,901, filed March 10, 1950, now Patent No. 2,670,665. This optical system, through the movements of a mirror or other suitable reflector, directs a beam of successively projected characters to variably spaced positions in a line upon a sensitized sheet or film, as hereinafter more fully described.

The present invention also constitutes an improvement over the variable escapement described in Patent No. 2,636,588. 'As such, it is well adapted for use in photocomposing machines of the type described in our'copending application, Serial No. 70,472, filed January 12, 1949, now Patent No. 2,682,814, and in said application Serial No. 295,284.

Other features of the invention relate to certain features of construction, modes of operation, arrangements and relationships which will be more readily understood from the following description of a preferred embodiment thereof.

In the accompanying drawings,

Fig. 1 is a partially schematic side elevation of the variable escapement showing various associated parts of a photographic composing machine, the latter being represented partly in block form; Fig. 2 is a front elevation of the ratchet advance mechanism for one stage of the variable escapement,

Fig. 3 is a bottom elevation of the mechanism shown in Fig. 2;

Fig. 4 is a view illustrating the condition of a delayed clutch after the completion of the resetting operation, or immediately prior to the transcription of a new line of characters;

Fig. 5 is a view similar toFig. 4, illustrating the condition of the clutch in an intermediate resetting position; Fig. 6 is an oblique view of a single delay wheel of the clutch;

Fig. 7 is a view of the switching mechanism controlling the reversible motor M, taken on line 7-7 of Fig. 1; and Fig. 8 is a view taken on line 8-8 of Fig. 1 showing the mechanism for stopping'the reset power shaft.

, Fig. 1 shows the basic elements of a photographic composing machine, with details of construction of the preferred form of variable escapement according to this invention. Preferably, the machine isessentially like that which is described in the above-mentioned application Serial No. 295,284, in that it employs multiplier units in conjunction with the recording and transcribing apparatus, as hereinafter more fully described. In place of the film carriage described in that application, however, we preferably use a sliding prism arrangement like that described in the above-mentioned application Serial No. 148,901. It will be understood, however, that the specific form of machine herein described is used merely for purposes of illustration, and is not intended to imply a limitation of the invention thereto.

The operation of the entire machine will first be generally described before passing to the description of the specific and preferred form of the variable escapement.

The operation of the machine in composing each individual line of type is conveniently described in terms of two distinct, consecutive steps. In the first or storage step,.the operator types the entire line on a keyboard unit 2, whereby an instantaneous visual copy of the typed matter is preferably produced for purposes of correction. Information relative to the selected characters including their respective widths is also recorded and accumulated in suitable memory and computing devices for later use in controlling the selection of characters to be transcribed, and in the automatic; computation of justification space corrections to be inserted or subtracted at appropriate places in the line. In the second or transcription step, the stored characters are successively disposed by photographic projection and with the desired spacing upon a sheet or strip of sensitized film. A suitable carriage, herein-after more fully described, isinterposed in the optical projection system and an element thereof is moved by an escapement to provide the necessary spacing.

At the beginning of the storage step, the machine opera-tor adjusts a coefiicient selector 4 (described more fully in said application Serial'No. 295,284) to a position corresponding to the set width of the characters to be composed. At this moment, the keyboard unit 2 is connected with one of two registers 6 or 8 as determined by the positions of switching means schematically illustrated by a set of transfer contacts 10. The keyboard is provided with a set of permutation bars mechanically engageable with the keying mechanism, whereby each depressed key moves a corresponding combination of the permutation bars, producing upon a set of output leads an electrical representation of information corresponding to the selected character. This information is of the binary form, that is, each output lead has only two possible conditions, energized and unenergized. Preferably, the total number of keyboard output leads is divided into two groups as described in said application Serial No. 295,284. One group represents the so-called relative width value of the particular character in binary notation; that is, one lead of the group represents each binary digit. The second group of leads represents information of two types, namely information which serves to distinguish characters of the alphabet having like widths from one another, and information in the nature of instructions pertaining to the transcription of the character, including its selected set width.

As the operator types each character of the line, the foregoing coded information is sent over the output leads to the register 6 or 8 then connected with the keyboard unit 2, and. also to a multiplier unit 12 which is connected with the coeflicient selector 4. This multiplier, as described in the application just mentioned, multiplies the binary number representing the relative width value of the character with the selected. coefficient, also represented in binary form, thereby producing a product in binary notation which is supplied to an accumulator 14. The latter accumulates a total representing the actual cumulative widths of the selected characters, together with minimum word spaces, since the relative width value of each. character has. been. multiplied by the selected set width in which it is to be projected to form each summand. The total is sent to a justifier 16 which, after the entire line has been typed, computes the desired increments to be added to or subtracted from the successive intercharacter or interword spaces, or both, to cause the line to become flush with both the left and right margins of the page. It will be clear, of course, that the justifier must also take into account the number of word spaces in the line, which number is conveniently supplied to it by means connected with the space bar of the keyboard unit 2, as shown in the above application.

During the subsequent transcription step, means schematically illustrated by transfer contacts 18 connect the register which contains the previously stored information with a reading unit 20, the latter being adapted to read the information character-by-character, moving automatically from one position to the next in the register under the control of automatic stepping means.

A suitable register and reading unit are described in our 4 copending application, Serial No. 770,320, filed August 23, 1547. i 1

Cycling means operating in synchronism with the movements of the reading unit cause projection of the selected characters as they are read from the register one at a time upon the sensitized film and subsequent spacing of the projected characters by corresponding variable amounts as determined by the information contained in the register and in the justifier. Since the projection and spacing operations follow successively upon one another, it is convenient to provide in the reading unit a number of sensing, or momentary-type contacts adapted to be operatively associated with depressible pins in the register, and holding or repeating relays adapted to be energized on the sensing contacts and to hold through cam-operated contacts associated with the operational timing or cycling mechanism. Such relays are described in said application Serial No. 70,472. In this manner, the information read from the register may be held for a brief period permitting the successive operation first of the projectionunit 22 and second of the variable escapement hereinafter to be more fully described.

The projection of the selected characters is preferably performed by a device such as that shown and described in. our copending application Serial. No. 770,320, mentioned above. The encoded information in the reading unit 20 is sent to a decoder 24 which selects a particular segment of a continuously rotating opaque disk 26, which segment contains a translucent character to be projected. The decoder is connected with the projection unit 22, which sends an impulse synchronized with the movement of. the disk over a lead 28 to an intermittent flash device 30. The fias'h device emits an exceedingly brief impulse of light energy through the disk 26at the precise moment when the selected character is accurately aligned in a fixed projection positionor axis, in front of a window 32 in-an optical frameor bench 34. This frame is similar to that described in the above-mentioned application Serial No. 148,901, and comprises a stationary collimating lens 36 and a movable system 38 comprising a reflector 40 and lens 42. The collimating lens forms an image of the selectedcharacter at infinity, and the parallel rays are collected by the lens 42 and converged after reflection upon the sensitized sheet 44.

To space the successive characters, themember 38 is moved 'by means of a rack 46 and pinion 48, the pinion being driven by the variable escapement mechanism. The escapement is driven in turnby energization of selected combinations of its input leads E1 to E256, which are connected to the justifier 16 and to a multiplier 50 similar in function and. operation to the multiplier 12 previously described. The multiplier 50 is connected with. the reading unit 20 to receive information corresponding to the relative width. value of the selected character. It receives information from a coefiicient selector 52 pertaining to the selected point set. The latter information, as previously mentioned, is also stored in the register and hence is available at the reading unit 20 from whence it is received by means of a lead 54.

The variable escapement operates directly from the binary information supplied to it by either the justifier 16 or the multiplier 50. Thus, it is not required that special provision be made to translate or decode the binary width information prior to its transfer to the escapement. This results in a considerable saving in equipment and hence reduces the cost of manufacture.

We turn next to a specific description ofthe variable escapement mechanism and its related parts. The device as shown in Fig. 1 is to a degree schematic in arrangement, proportions and details of design, but. it willbe understood that this is merely to permit a ready understanding of its operation. In actual construction the parts will, of course, be oriented in' suchsuitable manner as-may be dictated by considerations well known to those skilled in the mechanical arts.

The various parts of the mechanism are supported between the end walls of a rigid frame 56. In this frame are journaled a set of eight interconnected differential stages, each stage except the first representing one digit of the binary input. The right-hand differential, which is the single exception, represents both the lowest and nextto-lowest order digits. There is an input shaft L1 to L256 for each differential, except for the first which is connected to both of the shafts L1 and L2. There is also an output shaft P2 to P256 for each differential, and a carry-over gear M4 to M256 by which the motion of the output shaft is transferred to the next higher order differential. Thus for example, the motion of the output shaft P8 is determined both by the directly applied input rotation of the shaft L8 and by the carry-over motion imparted by the output shaft P4 through the gear M8.

The gear ratios throughout the mechanism are 1:1 except for the input shaft L1 connection to the lowestorder differential. The ratios produce a binary series, since the carry-over and direct input rotations are each scaled down in the differentials by a factor of 2.

It will be noted from the example just given that the carry-over gearing from stage to stage is indicated in the drawing as a dot-dash line connecting the output shaft of one stage such as P4 with an input gear such as M8 of the succeeding stage. It will be understood that in the actual construction, the gears connected by such lines are in actual engagement.

Each of the input shafts L1 to L256 is provided at one end with a clock spring 58 which at all times urges the shaft in the direction indicated by the arrow thereon. Escapement in this direction is controlled by a ratchet wheel and pawl device 60, details of which are shown in Figs. 2 and 3. A coil 62 connected with an input lead such as E1 produces a movement corresponding to one tooth of the ratchet wheel 64, which is rigidly secured to the corresponding shaft L1 by a set screw 66. Thus, for each desired space in the line energization of the appropriate combination of leads E1 to E256 produces one tooth of angular rotation in each of the corresponding combination of the input shafts L1 to L256.

The various parts of the ratchet advance mechanism are mounted in a rigid bracket 68 secured to the frame 56 by screws 70. The bracket has an outwardly turned end wall 72 and two outwardly turned upper sidewall portions 74 and 76. The end wall 72 furnishes support for a magnet assembly including the coil 62, a U-sha-ped closure 78 of magnetic material, and an end plate 80 also of magnetic material, the closure and end plate forming an external magnetic path for the coil 62.

Extending through the magnet is a fixed cylindrical core 82 having an enlarged end portion 84 with a shoulder resting against the plate 80. The core is threaded at the opposite end to receive a nut 86 by which the magnet assembly is fixedly secured to the end wall 72. The core 82 has a longitudinal slot extending from one end into the magnet to receive an armature 88. The armature is pivoted upon a shaft 90 which is in turn supported in a channel-shaped pivot member 92. The member 92 is supported on a shaft 94 suspended between the side walls 74 and 76 of the bracket 68. Thus, upon energization the coil 62 draws the armature 88 into the magnet, thus causing the pivot member 92 to rotate in the bracket about the shaft 94.

The member 92 has flange portions 96 and 98, the portion 96 having a stop pin 100 to limit rotation of the member 92 in the direction to withdraw the armature 88 from the magnet, and the flange 98 having a slot 102 to engage one end of a torsion spring 194, the other end of the spring being received into a hole 106 in the side wall 74 of the bracket. The spring 104 urges the pivot member 92 in the direction to cause the pin 100 to bear upon a surface of the side wall 76 when the magnet is unenergized.

When the magnet is in the unenergized condition as shown in the drawings, the pivot member 92 is in a position to cause a pawl 108 pivoted thereon to come into alignment with the ratchet wheel 64. A spring 110 urges this pawl into engagement with the wheel. The clock spring 58 (Fig. l) urges the wheel 64 in the direction indicated by the arrow in Figs. 2 and 3, thus defining what may be termed the rest position of the escapement.

Also pivoted upon the member 92 is a second pawl 112 having a spring 114 urging it against a stop provided by a screw 116 threaded into the member 92. Another stop is provided by a screw 118.

Upon energization of the coil 62, the armature 88 pivots the member 92 about the shaft 94, disengaging the pawl 108 from the wheel 64 and bringing the pawl 112 into position to engage with the next adjacent tooth after rotation of the wheel 64. It will be noted that the space between the pawls as viewed in Fig. 3 is less than the width of the teeth so that at all times at least one of the pawls is in position to engage therewith.

The clock spring urges the succeeding tooth into engagement with the pawl 112 after a rotation of the wheel which is appreciably less than the angle distended between adjacent teeth. The movement is very rapid, but the correspondingly large momentum of the wheel 64 and shaft L1 is absorbed by the spring 114 upon contact of the wheel with the pawl 112.

When the coil 62 is deenergized, the member 92 pivots back to its original position, bringing the pawl 108 into a position where, upon a small additional movement of the wheel 64, the tooth previously engaged by the pawl 112 comes into contact therewith. It will be appreciated that in this manner, we have provided a mechanism in which the precision of the escapement is insured by absorption of a large part of the momentum of the wheel 64 through the pawl 112, so that the impact of the teeth upon the pawl 108 is relatively small in spite of the exceedingly fast escapement speeds achieved.

As previously indicated, each of the input shafts L1 to L256 is rotated to a predetermined fixed position at the beginning of each line of transcription. This position may be conveniently indicated on the escapement by a mark 120 (Fig. 2) which is placed on the particular tooth of each of the ratchet wheels to be finally engaged by the pawl 108. During the transcription of a typical line, each of the input shafts will have been rotated by its ratchet means in the direction of the arrow (Fig. 1) through an angle correspondingto a random number of tooth spaces which varies from stage to stage. To reset each stage, we provide at one end of its input shaft a de layed action clutch 122. In addition to these clutches, we provide one additional clutch 123 of similar construction which forms no part of the character spacing mechanism, but is used exclusively as a control element governing the resetting operation. Figs. 4 and 5 show details of the clutch 123 on an enlarged scale, but it will become apparent that the following description thereof is also applicable, except as otherwise indicated, to the clutches on the input shafts. Extending longitudinally of the machine we provide a shaft 124 which is driven through bevel gearing 126 froma reset power shaft 128. The shaft 128 is rotated by a reversible motor M. The shaft 124 has a series of worms such as 130 having alternate left and right hand threads, each of the worms being in continuous engagement with a worm gear such as 132 forming one end of the clutch.

Referring to Figs. 4, 5 and 6, it will be noted that the shaft 133 of the control clutch extends through and is supported in the frame 56. Near the outer end of the shaft is secured a disk 134 by means of a set screw 136. Near its periphery the disk 134 has a downwardly extending pin 138. The gear 132 also has an upwardly extending pin secured near its periphery.

Between the pins 138 and 140are supported a number of delay wheels or disks 142, each constructed in the gauge-74 shape shown in Fig. 6, and each free to slip in rotation about the shaft 133. The'disks are separated by suitable spacers 144 so that the outwardly turned lugs 146 of adjacent disks may come into contact. The pins 138 and 140 are in appropriate positions to come into contact with the end lugs as shown in the drawings. The clutches on the input shafts are similarly constructed, except that they each have one more disk 142, and do not have a disk like the disk 150.

Immediately prior to the transcription step, each clutch is in a position corresponding to that shown in Fig. 4. During the transcription of the line, the input shafts L1 to L128 move, under the control of the input signals, in selected combinations, each shaft moving in such a direction that its pin corresponding to the pin 138 in Fig. 4 moves away from the lug of the delay disk with which it is initially engaged; After approximately a full revolution this pin will have moved to a position bearing upon the lug from the opposite direction. For example, if the clutch 123 were connected with an input shaft, the input shaft would escape in the direction indidicated by the arrow in Fig. 4. (It will be appreciated that, in fact, the clutch 123 remains in the position shown throughout the transcription step.) Further movement after the pin bears upon the lug would cause rotation of the topmost delay disk and would also cause the oppositely turned lug of this latter disk to move out of engagement with its. own lower contacting lug until, in turn, this lug becomes engaged and so on. There are enough delay disks 142 on each clutch so that in even the longest line the final lug on the lowermost disk will not engage with the pin corresponding to the pin 140. It will be understood that this latter pin is stationary throughout the transcription step, and that the shaft 124 does not rotate. Therefore, during the transcription step each input shaft is rotated through its ratchet mechanism without restraint by the delayed action clutch.

At the end of the line of transcription, each of the input stages is reset in two steps which may be conveniently termed the rewind step, and the return step. At the beginning of the rewind step the control clutch 123 and related parts are in the positions shown in Figs. 4, 7 and 8. This clutch, having no associated input ratchet mechanism, does not move during the transcription of the line, and remains in a position such that the gear 132 is urged in the direction indicated by the arrow in Fig. 4, so that it causes. a pin 148 projecting from a disk 150 secured to the shaft 133 to bear upon a pin 152 extending from an arm 154, the arm being in turn secured to a shaft 156. The shaft 156 is rotatably journaled in the frame 56 (see Fig. 1). An arm 158 also secured to the shaft 156 holds an insulated contact roller 160 against a pair of normally-closed contacts B, holding them open. An extension of the arm 154 is secured to a spring 162 which is fastened at the other end to the frame. This spring normally urges the roller 160 to the position indicated at 164, but the pin 148' holds it in the position shown in Fig. 7.

While the arm 154 is being so held, a pair of stop arms 166 and 168 rigidly secured with it to the same shaft 156 are held in the positions shown in Fig. 8. The arm 166 engages a stop cam 170., The arm 168 is free of a secondstop cam 172. These two cams are secured to the shaft 128 (see also Fig. 1).

As previously explained, the clutches associated with each of the input shafts will have moved during transcription from aniinitialposition in which their respective disks 142 appear as shown in Fig. 4, starting at the upper end corresponding to the disk 134, according to the movements of their respective input escapements; but no motion will have reached the gear corresponding to the gear 132 of any of these clutches.

The rewind step is initiated, by a circuit hereinafter described, whenthe motor M begins toturn the shaft 128 in the direction indicated by the arrows in Figs. 1,

8 7. and 8. Through the bevel gearing 126, this turns the shaft 124 in the direction indicatedby the arrow in-Fig. 1, and imparts motion to the worm gear 132 and the corresponding gear of each of the input delay clutches 122 in the direction opposite to that of the arrow in Fig. '4.

in the first revolution of the shaft 128, the cam 170 (Fig. 8) throws the arm 166 out of engagement therewith, and rocks the arm 154 toward its neutral position allowing the contacts B to close. (The consequent slight downward movement of the pin 152 is not prevented by the control clutch 123 because of the previously-mentioned movement of the gear 132 in the appropriate directionto allow such motion.)

, Continued rotation of the motor M after the above events causes engagement, approximately once per revolution of. the gear 132,. of this gear with an additional disk 142 until ultimately the disk 134 is engaged. When this occurs, the disks 142 of the clutch 123 will appear as shown in Fig. 5. Once the disk 134 is engaged, the shaft 133 is turned, rotating the pin 148 in the direction of the arrow in Fig. 7 until it bears upon the pin 152 from the side opposite to that shown in the figure. The rewind step is terminated thereupon and the motor M stopped by movement of the roller to close a pair of normally-open contacts A. At substantially the same time, the rocking of the arm 154 moves the stop arm 168 into position to engage with the cam 172. This positively stops the motor shaft 128 in a precisely defined position.

At various times during the rewind step, that is, while the motor M is rotating, each of the input delay clutches 122 will have become engaged therewith. The motion of the input shaft in each case during transcription will have been opposite to that of its worm gear during the rewind step. Therefore the clutches of those escapements which operated more frequently in a given transcription stepv will engage earlier than others which operated less frequently. But at the end of the rewind step, each input shaft will have been returned to its original position by rotation in reverse through the same total angle through which it turned during the preceding transcription step.

To insure accurate resetting of the mechanism with backlash taken up, the cam 172 is set so that when it is engaged by the arm 168 each of the input shafts has advanced to a position in which its pawl 108 rests within the space of the particular tooth on the ratchet wheel marking the initial position of the input shaft. In other words, there is a slight over-travel in each stage on resetting, so that upon subsequent reversed rotation of the motor M, as hereinafter described, the clock spring in each stage will cause a slight motion of the wheel in the normal direction of escapement before the wheel becomes positively engaged by the pawl. It will be appreciated that during this entire resetting step the member 38 of the character spacing mechanism is in continuous engagement with the variable escapement, that in consequence the said member overtravels at the margin by a slight distance during the resetting step, and that it moves up to the precise initial position for the transcription of a new line when the respective ratchet wheels are allowed to move back against their respective pawls as described. We may also provide, if required, a supplementary spring 173 secured at one end to the frame and at the other end to the member 38 to urge the latter in the direction opposite to that of its movements during transcription. This spring provides a force which is weaker than that of any of the clock springs 58, but strong enough to bring the differentials and transfer or carry-over gears M4 to M256 into positive engagement with the input gears, particle larly in the highest order stages of the escapement where backlash is more noticeable. By this means, the backlash within the mechanism is completely taken up.

The return step is initiated with the closing of the contacts A, and a circuit hereinafter to be more fully described operatesto reverse the motor M, thereby rotating the control clutch 123 in reverse through exactly the same angle by which it rotated in the rewind step. This rotation sets all of the clutches back to the position indicated in Fig. 4, but produces no movement'in the input shafts of the escapement stages, the latter being held by their respective pawls 108. In the last revolution of this return step, the pin 148 of the control clutch moves in the direction opposite to that of the arrow in Fig. 7, thereby finally opening the contacts B when the pin 148 engages with the pin 152 and moves it to the position indicated in Fig. 7. The rocking of the arm 154 causes the stop arm 166 to engage with the cam 170 to stop the shaft 128 positively in a manner similar to that previ ously described for the rewind step.

The rotation of the motor M is under the control of two relays R1 and R2. These relays are connected with the contacts A and B as shown in Fig. l. The circuit conditions as shown correspond with those which obtain immediately after the end of the return" step, that is, at the beginning of a new line of transcription.

When a new line is to be transcribed, the machine operator closes a key K which energizes the relay R1. This relay holds through its normally open contacts in series circuit with normally closed contacts of the relay R2. Energization of the relay R1 closes a second pair of contacts to connect a voltage source with a lead 174, causing rotation of the motor M in an appropriate direction to perform the rewind step of the resetting operation as previously described.

In the initial movement of the roller 160 in the rewind step, the contacts B close, but this has no effect upon the circuit. However, at the end of the rewind step, the contacts A are closed, thereby causing energization of the relay R2 through the contacts B, now closed. The relay R2 holds through its normally open contacts in series circuit with the contacts B. The holding circuit of the relay R1 is opened by the relay R2 and the potential is thereby removed from the lead 174. Voltage is immediately applied to a lead 176 through transfer contacts of the relay R2, thereby causing reverse rotation of the motor M. This rotation continues until the contacts B are again opened by the roller 160. This breaks the holding circuit of the relay circuit R2, after which both relays R1 and R2 remain at rest until the key K is again depressed.

It will be understood that while the present invention has been described with reference to a specific embodiment it is in no way limited thereto, but on the contrary, it encompasses all variations in control circuitry, design, arrangement and relationships of the various parts that will occur to those skilled in this art in the light of the foregoing specification.

Having thus described our invention, we claim:

l. A differential device having two input shafts and an output shaft, driven means connected with the output shaft, means to advance the input shafts in successive selected combinations to produce movements of predetermined variable size in the output shaft, said successive advancements being initiated with each input shaft in a fixed initial positio and resettng means including a delayed action clutch connected with an input shaft and reversible means for driving the clutch to rotate the shaft to said position through an angle equal to its aggregate movement in said succession of advancements and in the opposite direction thereto.

2. A differential device having two input shafts and an output shaft, driven means connected with the output shaft, means to advance the input shafts in successive selected combinations to produce movements of predetermined variable size in the output shaft, said successive advancements being initiated with each input shaft in a fixed initial position, and resetting means including a delayed action, two-way clutch connected with an input shaft, reversible drive means for the clutch, and controls having provision to drive said shaft through the clutch to ment in said succession of advancements and in the oppo= site direction thereto.

3. A variable escapement mechanism comprising a number of stages arranged in a series, each stage com prising a differential device having two input shafts and an output shaft, at least one of said stages having an input shaft connected with the output shaft of the preceding stage in said series, means to advance the input shafts of each of a selected combination of the stages to produce a movement of predetermined size in the output shaft of the final stage, said advancement being initiated with each input shaft in a fixed initial position, and resetting means for each stage to rotate an input shaft independently to said position through an angle equal to its movement in said advancement and in the opposite direction thereto.

4. A variable escapement mechanism comprising a numoer of stages arranged in a series, each stage comprising a differential device having two input shafts and an output shaft, at least one of said stages having an input shaft connected with the output shaft of the preceding stage in said series, means to advance the input shafts of the stages in successive selected combinations to produce movements of predetermined variable size in the output shaft of the final stage, said successive advancements being initiated with each input shaft in a fixed initial position, and resetting means -f-or each stage to rotate an input shaft independently to said position through an angle equal to its aggregate movement in said succession of advancements and in the opposite direction thereto.

5. in type composing apparatus, the combination of a keyboard having provision for selection of the characters in a line of type, means for transcribing the characters successively upon a sheet, and an escapement mechanism to move the transcribing means relative to the sheet for spacing the characters, said mechanism consisting of a number of stages arranged in a series, each stage comprising a differential device having an individual input shaft, means to advance each input shaft from an initial position in successive selected combinations to produce movements of the escapement corresponding to the widths of said characters, and resetting means for each stage having provision to move its said input shaft after the last character in said line is spaced through an angle equal to its movement in said advancement and in the opposite direction thereto.

6. in type composing apparatus, the combination of a keyboard, a register for storing information corresponding to each of the selected characters in a line of type, said information including a binary representation of the character width, means for transcribing the characters successively upon a sheet, and a variable escapement mechanism to move the transcribing means relative to the sheet to space the characters, said mechanism comprising a number of stages arranged in a binary series, each stage including a differential device having an individual input shaft, and means connected with the register for rotating selected combinations of the input shafts in accordance with the binary values represented.

7. In type composing apparatus, the combination of a keyboard, means actuated by the keyboard to represent the Width of each selected character successively in binary form, means for transcribing the key-selected characters successively upon a sheet, and a variable escapement mechanism to move the transcribing means relative to the sheet to space the characters upon the sheet, said mechanism comprising a number of stages arranged in a binary series, each stage including a differential device having an individual input shaft, and means connected with said width representing means for rotating selected combinations of the input shafts in accordance with the binary values represented.

8. In type composing apparatus, the combination of a keyboard having provision for selection of the characters in a line of type, means for transcribing the characters successively upon a sheet, an escapement mechanism to move the transcribing means relative to the sheet for spacing the characters, said-mechanism consisting of a number of stages arranged in a series, each stage comprising a differential device having an. individual input shaft, means to advance the input shafts in successive selected combinations to produce movements of the escapement mechanism corresponding to the widths of said characters, each input shaft having apredetermined initial position at the beginning of the line, and resetting means for each stage having provision to move its said input shaft after the last character in said line is spaced through an angle exceeding in magnitude and opposite in direction to its move ment in said advancement, and thereafter to return said shaft precisely to its initial position.

9. In type composing apparatus, the combination-of a keyboardhaving provision for selection of the chara ters in a line of type, means for transcribing the characters sue cessively upon a sheet, a carriage to move the transcribing means relative to the sheet from an initial marginal posi tion for spacing the characters, an escapement mechanism for the carriage, said mechanism consisting of a number of stages arranged in a series, each stage comprising a differential device having an individual input shaft, means to advance the input shafts from an initial position in successive selected combinations to produce movements of the escapement mechanism corresponding to the widths of said characters, resetting means having provision to move each input shaft after the last character in said line is spaced through an angle exceeding in magnitude and opposite in direction to its angular movement in said advancement, 50

and thereafter to return said shaft precisely to its initial position, and a spring urging the carriage to return past its said initial position and thereafter permitting movement to said position upon operation of the resetting means.

, 10. A differential device having two input shafts and anoutput shaft, driven means connected With the output shaft, means to advance an input shaft insuccessive selected steps to produce movement of predetermined size inthe output shaft, said successive advancements being initiated with said input shaft in a fixed initial position, and resetting means for said. input shaft including a gear, a delayed action two-Way clutch connecting said shaft With the gear, means to rotate the gear through a fixed angle to to engage the clutch and cause said shaft to return to said initial position, and means to rotate the gear through an equal and opposite angle after said shaft is returned.

11.; A differential device having two input shafts and an output shaft, driven meanstconnected with the outputshaft, means to; advance an input shaft in successive selected steps-to produce movements of predetermined size in the output shaft, said successive advancements being initiated with-said input shaft inafixed initial position, and resetting means for said input shaft including a gear,

a. delayed action, two-Way clutch connecting said shaft with-the gear, means to rotate the gear through a fixed angle to engage the clutch and cause said shaft to return to a position beyond said initial position, means to rotate the gear through an equal and opposite angle after said shaft is returned, and ratchet and pawl means to arrest the shaft precisely in said initial position.

References Cited in the file of this patent UNITED STATES PATENTS 1,084,671 Tallmadge Jan. 20, 1914 2,411,723 Hausman Nov. 26, 1946 2,439,470 Jackson Apr. 13, 1948

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