US3830976A

US3830976A - Printing telegraph mechanism

Info

Publication number: US3830976A
Application number: US00366220A
Authority: US
Inventors: T Taylor
Original assignee: International Standard Electric Corp
Current assignee: Alcatel Lucent NV
Priority date: 1972-06-01
Filing date: 1973-06-01
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20
Also published as: FR2186893A5; GB1321969A; DE2327683A1; ES415461A1; AU5641273A

Abstract

The styli of a mosaic printhead are each attached to switchable conductive loops positioned in a gap between a pole piece and a rotatable magnetic member. The rotatable member is rotated continuously and periodically induces currents in closed, conductive short circuited loops thus causing them and their associated styli to move.

Description

United States Patent [1 1 Taylor Aug. 20, 1974 PRINTING TEIZEGRAPI-I MECHANISM [75] Inventor: Terrence Francis Edward Taylor, [56] References Cited Burgess Hill, England UNITED STATES PATENTS 73 Assigneez International standard Electric 3,477,365 11/1969 Nyman 346/141 X Corporation, New York, N.Y. Primary Examiner-Thomas A. Robinson [22] Flled: June 1, 1973 Attorney, Agent, or Firm-A. Donald Stolzy [21] Appl. No.: 366,220

' [57] ABSTRACT [30] Foreign Application Priority Data The styli of a mosaic printhead are each attached to J 97 switchable conductive loops positioned in a gap beune l, 1 2 Great Britain 25597/72 tween a p piece and a rotatable magnetic member The rotatable member is rotated continuously and pe- [52] Cl 178/30 178/33 3 5 35 riodically induces currents in closed, conductive short [51] Int Cl 9/38 H041 21/00 circuited loops thus causing them and their associated [58] Field of Search 178/17 R, 27, 30, 33; move 346/141; 310/103, 105; 335/229; 197/1 R 10 Claims, 15 Drawing Figures 7/ @4 Z9 78 /0 p 5 ['1 5 ll 75 Pmmzuwcz m 3.830.976

' slmws FIGM.

v 1 PRINTING TELEGRAPH MECHANISM BACKGROUND OF THE INVENTION This invention relates to the art of serial printing, and more particularly, to a method of printing mosaic characters.

In the past, it has been the practice to print a mosaic character by employing a vertical column of styli equal to the character height and printing no dots or one or more dots by styli actuation at successive different horizontally spaced columns over a character width. Typically a column from 7 to 15 styli may be employed at from to 9 of said horizontal locations. The styli spacing is conventionally, but not necessarily, uniform. So is the location spacing. These two may or may not be equal, as desired.

The styli are typically mounted on a movable carriage on which styli actuators are supported. The actuators and other apparatus on the carriage increase the inertia thereof and decrease its advancing and return acceleration, deceleration and velocity, both maximum and average. This is a disadvantage in the operation of a high speed machine.

SUMMARY OF THE INVENTION In accordance with the mechanism of the present invention, the above-described and other disadvantages of the prior art are overcome by utilizing a lightweight induced current activated conductive loop to operate a stylus.

The above-described and other advantages of the present invention will be better understood from the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of a conventional mosaic printer;

FIG. 2 is a sectional view of a portion of a stylus head, a portion of which may be employed with the present invention;

FIG. 3 is a top plan view of a portion of a recording medium in five states of the development of a mosaic character thereon, the character being the numeral 7;

FIG. 4 is a view similar to FIG. 2, but modified in accordance with the present invention;

FIG. 5 is a perspective view of an electromagnetic arrangement constructed in accordance with the present invention;

FIG. 6 is a perspective view of a rotatable magnetic member, conductive loops and a switch;

FIGS. 7 and 8 are end elevational views of two alternative embodiments of the present invention;

FIG. 9 is a perspective view of apparatus similar to that illustrated in FIG. 1 modified as in FIG. 4;

FIG. 10 is a side elevational view of a portion of the apparatus of the present invention;

FIG. 11 is a transverse sectional view of a stylus portion and support tube portion taken on the line 11-11 shown in FIG. 10;

FIG. 12 is a top plan view of the apparatus shown in FIG. 10;

FIGS. 13 and 14 are alternative embodiments of the present invention; and

FIG. 15 is a block'diagram of a telegraphic machine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional prior art mosaic printer is shown in FIG. 1 including an input circuit 20 which receives and stores, for example, a serial binary code which determines which, if any, of a plurality of styli in a column are to be employed to print dots on a recording medium. Input circuit 20 thus controls a stylus head 21 and the individual styli thereof through a stylus control 23. Input circuit 20 also controls a roll control 24 for a roll 25 which supports a recording medium 26 such as inked paper. Input circuit 20 also controls a carriage control 27 which pulls a carriage 28 in a direction to the right, as viewed in FIG. 1, against the force of a spring 29 which is fixed at its left end connected to carriage 28 at its right end. Head 21 is fixed to carriage 28. Carriage 28 has a single guide 30 in which carriage 28 is guided by a tongue 31 that fits in a groove 32 of channel 30.

As shown in FIG. 2, stylus head 21 includes a rearwall 33 and a front wall 34.

In FIG. 2, a stylus 36 is slidable through a hole 37 in wall 34. A solenoid winding 38 is fixed to wall 34. Stylus 36 is thus slidable through winding 38. A coiled spring 39 rests against the right end of winding 38 and urges stylus 36 in a direction toward wall 38. Stylus 36 has a flange 40 fixed to the end thereof which is pressed against wall 33 by spring 39. Movement of stylus 36 in a direction to the left, as viewed in FIG. 2, is stopped by engagement of flange 40 with a flange 41 on a cylinder 42 fixed to wall 33.

In the prior art, and in accordance with the present invention, dots may be made on paper 26 by the impact of the end of a stylus thereagainst.

In the prior art, a mosaic character may be formed as shown inFIG. 3 The same portion of a recording medium is illustrated at 43, 44, 45, 46 and 47. It will be understood when no solenoid corresponding to solenoid 38 in FIG. 2 is energized for any of the styli 22 shown in FIG. 1, a space will be left on the recording medium. However, this space will not be one character space, but, for example, may be only one-fifth of a character space. When one or more dots in one column are produced, all of these dots may be made simulta* neously.

As shown in FIG. 3, the dot in rectangle 43 is made before the other dots are made. Dots 48, 49, 50 and 51 then may be made simultaneously thereafter. One or more additional dots are added in each column until the numeral seven is portrayed in rectangle 47.

In accordance with the present invention, the chronological order in which the dots are made may or may not be as described hereinbefore and as shown in FIG. 3.

A stylus head 21' is indicated in FIG. 4. A stylus 36' is shown in FIG. 4 slidable through a hole 37' in a wall 34. A hollow cylinder 38 may be slidable on stylus 36' or fixed to wall 34, if desired. In either event, stylus 36' is slidable through cylinder 38'. A coiled spring 39' rests against the right end of cylinder 38' and urges stylus 36' in a direction toward a wall 33'. Stylus 36' has a flange 40' fixed relative thereto which is pressed against wall 33' by spring 39'. Movement of stylus 36' in a direction to the left, as viewed in FIG. 4, is stopped by engagement of flange 40 with a flange 41 on a cylinder 42' fixed to wall 33'.

Note will be taken that the stylus head 21' in FIG. 4 does not differ a great deal from the stylus head 21 in FIG. 2. One difference is that, in FIG. 4, cylinder 38 replaces solenoid winding 38 in FIG. 2. Still further, rear wall 33 has a hole 37" therethrough through which an extension 36" slides.

In some cases, all of the structures illustrated between the walls 33' and 34' may be omitted with the exception of stylus 36. In some cases, flange 40 may also be omitted. Note will be taken that, as shown, stylus 36', flange 40' and extension 36" are fixed relative to each other.

Because of the mass of a print wheel which bears all the symbols likely to be required at a given time by a dataprinter, and of the time taken to position a required symbol at the point of printing, the development of mosaic printers has been looked upon favorably. In these printers, symbols to be printed are built up by the selective printing of dots at positions in an array, usually rectangular, of possible positions. A rectangular array of 35 dots, seven rows by five columns enables a readable representation off the roman letters and arabic numerals to be obtained. Instead of using 35 printing styli, or needles, and selecting all those needed for a particular symbol at the same time, mass can be saved by printing the five columns in succession, using only seven needles. In one commercially available printer of this kind, each needle is driven by its own individual solenoid, the mass of which is some 30 grams. In the interest of speed and reduced wear, it is desirable to reduce this mass even further. This is accomplished in accordance with the present invention.

In the drawings, in FIG. 5, a magnetic yoke 101 is shown. It is of substantially U-shaped cross section which is at least as long as a record web is wide. The record web is that on which the symbols are printed. One limb 102 of the yoke 101 is shaped as a pole piece and another limb 103 cooperates with a short pole piece 104 attached to a printhead carriage. The pole piece 104 causes a local concentration of the magnetic flux produced by the magnetic at the place where it is most useful and so helps to reduce power supply requirements.

A conductive coil 55 encircles a third limb 56 which joins together limbs 102'and 103. By means of electric current in this coil, the magnetic assembly can be energized. Alternatively, yoke 101 and its

limbs

102 and 103 and winding 55 are shorter than the web width, but are replicated across it and are energized in succession, this again reducing the power supply requirements.

A rotatable magnetic member 57 coextensive at least with the width of the record web is mounted to rotate around an axis parallelto its length between the pole pieces, fitting closely in the curved pole piece of limb 102, but being separated from the pole piece 104 by a distance sufficient to allow a conductive loop 58 to perform a linear movement generally perpendicular to the length of the pole piece and to the record web. The loop, which is rigid, is rigidly connected to a printing needle carried on the printhead carriage, which can be made to traverse the width of the record web in order to print a line of graphical symbols. As many loops 58 as there are printing needles are provided. To each loop 58 there may or may not be connected a switch 59 as shown in FIG. 6 through trailing conductors or slip rings, for instances. The pole piece 104 is long enough to cover the loops of all the needles which may be actuated at any one instant.

The rotatable member 57 is caused to rotate continuously by a synchronous motor M or a motor synchronous with the incoming message. Motor M may be shut down, on occasion, if desired.

If motor M is synchronous with the incoming data, the column print data should be spaced in some cases to prevent a printout in two columns.

If motor M is a synchronous motor, it should be fast enough to produce one stylus movement for each set of column data. The data for one column should also be spaced in time to prevent a printout in two columns or between columns.

Motor M is energized at least while the yoke 101 is energized. When any switch 59 is closed, cyclic flux variations, when motor M is running and winding 55 is energized, induce a current in the appropriate conductive loop 58 which sets up its own magnetic field. The interaction of the magnetic field produced by the induced current and the field in the gap between pole pieces 104 and rotatable member 57 causes the loop, and the needle rigidly connected thereto, to move towards the record web, the needle thereby printing a dot. This happens as the narrow face of the rotatable member 57 moves to a position at or near conductive loop 58. Thus, by selective closure of the switches 59, selected loops 58 and their associated needles are moved.

The switches 59 are controlled either from a key board or by signals received from some more or less remote source, and may be any kind of switching device which when closed, or in a conducting condition, offers negligible impedance to the induced currents in an associated loop.

In FIG. 7, a different yoke arrangement is shown. l-lere limbs 102' and 103' and pole piece 104' are as in FIG. 5, but the coil 55 is dispensed with and a permanent magnet forms the limb 56.

Yet another arrangement is shown in FIG. 8. Here limbs 102", 103" and 56" are as in FIGS. 5 and 6, as is pole piece 104", but rotating member 57" is itself a permanent magnet. This arrangement, of course, causes complete flux reversal within the magnetic yoke for each rotation of the member 57".

Pole piece 104 may be coextensive with limb 103 and attached thereto instead of being carried on the printhead, although this does not conserve power as does the travelling pole piece.

In FIG. 9, a carriage 60 rolls on a track 61 having rails 62 and 63. Carriage 60 and wheels 64 that roll on track 61. A support and guide plate 65 is fixed to carriage 61. Styli 66 are movable through plate 65. A record web 67 is indicated adjacent styli 66.

In FIG. 10, a magnetic yoke 101' is illustrated with an energizing winding 55'. Yoke 101' has a stationary upper limb 103" and a stationary lower limb 102". A rotatable magnetic member 57" is fixed to and rotatable by and with a drive shaft 68. A traversing pole piece 104" is shown adjacent the limb 103". A pole piece support beam 69 rigidly connects pole piece 104" with a support and guide plate 70. A rear support and brace 71 is fixed to beam 69 and a carriage 72. Brace 71 also has a support tube 73 fixed thereto through which a stylus 74 is slidable. Carriage 72 has wheels 75 as before, which travel on rails 76. A conductive loop 77 is fixed to stylus 74. A platen 78 is provided on which a'web 79 is movable. Platen 78 rolls, but need not have a carriage. It can stay in a fixed axial position.

Plate 70 may or may not be identical to stylus head 21 of FIG. 4.

In FIG. 10, stylus 74 may have a uniform circular cross section throughout its length except for a square portion thereof shown in tube 73. Tube 73 may or may not be square in cross section throughout its entire length. However, it is square over a portion of its length that stylus 74 is square. Alternatively, no means or some other means may or may not be provided to keep stylus 74 and loop 77 from turning about the axis of stylus 74. Stylus 74 may or may not be spring biased.

In FIG. 12, stationary upper limb 103" is again shown with drive shaft 68, rotatable magnetic member 57", stationary lower limb 102", traversing pole piece 104", conductive loop 77, pole piece support beams 69, support tube 73, brace 71, carriage 72, rails 76, plate 70, stylus 74, and web 79. Note will be taken that there are two pole piece beams 69 in both of the FIGS. and 12.

In FIG. 15, a telegraphic machine is indicated at 80 having telegraphic lines 81 and 82 connected thereto. Telegraphic machine 80 has input and

output units

83 and 84, respectively. Telegraphic machine 80 also has a tape punch 85, a keyboard to telegraph code converter 86, a tape reader 87, a telegraph code to mosaic pattern coverter 88, a stunt box 89, a keyboard unit 90, and a printing unit 91.

Telegraphic lines 81 and 82 are connected to input unit 83. Converter 86 and tape reader 87 are connected to the input of output unit 84. The output of output unit 84 is connected to telegraphic lines 81 and 82 The output of tape reader 87 is also connected to converter 88 and tape punch 85. The output'of con verter 86 is connected to one input of stunt box 89, one input to converter 88 and to one input of tape punch 85.

The output of input unit 83 is connected to still another input of tape punch 85, to still another input of converter 88 and to still another input of stunt box 89.

Converter 86 receives an input from keyboard unit 90. Printing unit 91 receives inputs from outputs of converter 88 and stunt box 89.

In review, mosaic printheads have been developed by Philips, as well as several others, including that used in the teleprinter manufactured by Extel Corporation of Chicago, Illinois. These printheads build up characters as a pattern of dots in a possible matrix of 7 X 5 dots. Instead of employing 35 styli and energizing all the styli needed for a character at the same time, they have only 7 stylie arranged in a vertical column and form a character by selectively energizing the styli at five postions, one after the other, much in the way described in copending application Ser. No. 295,154, filed Oct. 5, 1972, by T. J. Holland for PRINTING METHOD, now US. Pat. No. 3,757,346.

These printheads carry individual motors for each stylus on the printhead, in the case of the Philips head, seven motors being needed. (By motor," we mean an actuating device for moving the stylus, not necessarily a rotating electrical device. Thus, a solenoid is a motor, and so is a piezoelectric bimorph.) In order to deliver a sufficiently great impact to print these motors must be reasonably powerful. This means that the printhead is carrying a fair amount of mass.

A lightweight printhead is desirable so that it can be traversed across the record web at high speeds, particularly, in carriage return. It would, therefore, be of advantage if the head carried only the styli and the supports therefor and as little else as possible, ideally as shown herein.

In FIG. 9, carriage 60 runs on rails and has the support and guide plate through which 7 styli 66 protrude towards a record web 67.

Some form of motor must move the styli 66 towards the web 67 in order that printing may take place. In accordance with the present invention, the back ends of the styli 66 (the ends remote from the web 67) have rigid conductive loops 77 attached thereto by motion transmitting means. The motion transmitting means (e.g., connection means between driver means and the styli 66) may be directed rigid rods, or Bowden cables like bicycle hand brake cables. In accordance with the present invention, loops 77 moving with the printhead are influenced by, not a single motor per stylus, but a common motor, which common motor does not, of itself, traverse the web 67, but is instead coextensive with the width of the web 67. All the loops 77 for each stylus 66 are infleunced, when the loop is complete, by the one motor. The motor is, if you like, an electromagnetic printing bail.

Only one 74 of several styli have been shown in FIG. 10 for clarity. The other styli, if connected to their loops by rigid rods would have to pass through the supports at angles to each other so as to hit the web in a vertical line. See FIG. 13. If connected by Bowden cable, they could be in line at the support plate. See FIG. 14.

Some of the dimensions have been greatly exaggerated for clarity. The loops would be much smaller in width so that all could sit side by side under the traversing pole piece.

An alternative to the travelling pole piece would be to have a stationary pole piece coextensive with the stationary upper limb, thus taking some weight off the traversing printhead. Such a stationary pole piece would, of course, be integral with the stationary upper limb, thus eliminating the air gap.

The rotating magnetic member is rotated at a constant speed by some suitable drive means as long as the printer is in use. The grooves shown in FIGS. 5 and 8 cause the flux to swing back and forth across the loops at a greater rate than it would if it depended on the speed of rotation of the rotating magnetic member alone.

The printhead forms part of a printing unit which in turn is part of a telegraphic machine, for example,-a teletypewriter or teleprinter. FIG. 15 shows the basic units of such a machine. The input unit accepts telegraph signals from the line and renders them suitable for use within the machine. The telegraph code to mosaic pattern converter does exactly what its name implies producing at its output signals with which to operate the printing unit; such a unit has been described before.

In the event that some question arises concerning the structure or operation of converter 88, two patents disclosing both are, by this reference hereto, hereby incorporated herein as though fully set forth hereat. These patents are British Pat. No. 1,240,477 and Swiss Pat. No. 501,971.

The stunt box is a well-known unit which transforms the appropriate telegraph signals into commands to line feed, carriage return, space, et cetra. The keyboard unit generates signals, possibly in its own code, to be applied to the output unit or the printing unit or the tape punch or any combination of the three. The tape reader generates signals to be applied to the same three units in any combination. The keyboard code to telegraph code converter does exacctly what its name implies, assuming that the keyboard does not produce telegraph code directly (otherwise the converter is unnecessary). The output unit renders the signals in the machine suitable for application to the telegraph line. Interconnections between the units have been shown as single lines; however, the intramachine signals may be handled in parallel over multiple con nections.

Although the apparatus of the present invention may be used in punched tape or other applications, it most likely will be used more by repeatedly striking paper (web) on a platen with one or more styli simultaneously or consecutively to provide a dot mosaic inked letter, number, character or otherwise. Any means may be employed to provide or not to provide the ink, as desired. An inked ribbon may be used. It is also well known that a character may be produced by striking a conventional inked paper which carries its own ink. Paper 79 shown in FIG. 10 may be such inked paper, if desired. Many other suitable inking methods and equipments will also be obvious to those skilled in the art.

As stated previously, stylus head 21' shown in FIG. 4 or any modification thereof may be substituted for plate 70 in FIG. 10.

The word carriage is hereby defined for use hereinbefore and hereinafter and for use in the claims to mean something that carries something else, and may either be movable or be fixed unless its mobility or the lack of it is specifically and expressly stated.

The phrase carriage means is hereby defined for use hereinbefore and hereinafter and for use in the claims to mean one or more structures and/or a carriage as that word carriage is defined in the immediately preceding paragraph.

The phrase connecting means is hereby defined for use herein and for use in the claims to mean either an electrical conductor integral or not with the conductive loop or a switch or otherwise.

What is claim is:

l. A printer comprising:

a base;

a carriage means mounted on said base;

platen means mounted on said base in a manner to support a recording medium adjacent said carriage means;

an elongated axially movable stylus having first and second ends;

a conductive loop fixed relative to said second stylus end;

means to produce relative movement between a recording medium and said first stylus end in a direction approximately normal thereto;

means mounted on said carriage means to guide said axial movement of said stylus;

driver means to produce magnetic flux in a location linking said conductive loop, said driver means causing the amount of said linking flux to change abruptly; and

a selectively operable switch connected in series with said conductive loop to short circuit the same when the switch is closed, said abrupt change in flux leaving said conductive loop axially motionless when said switch is open, said abrupt change in flux causing a force to be applied to said conductive loop when said switch is closed, said force being transmitted to said stylus to move the same axially to cause said first end thereof to strike a recording medium when such is supported in position therefor by said platen means as aforesaid, and to make a detectable recording mark on said recording medium where said stylus first end strikes said record medium, closure of said switch permitting a current to be induced in said conductive loop, which induced current produces its own magnetic field that reacts with that produced by said driver means and causes said force to be applied to said conductive loop.

2. The invention as defined in claim 1, wherein:

means are provided to prevent said conductive loop from rotating about the axis of said stylus.

3. The invention as defined in claim 2, wherein:

a spring is provided, said spring being mounted on said carriage means to urge said stylus in a direction away from said platen means.

4. The invention as defined in claim 3, wherein:

said driver means includes a magnetic circuit having a fixed magnetic yoke including an elongated, noncircular magnetic shaft spaced a short distance therefrom, a maximum flux being established in said magnetic circuit when said shaft is located in one angular position, a minimum flux being established in said magnetic circuit when said shaft is located in another angular position, means to rotate said shaft, means to establish a magnetomotive force in said magnetic circuit, said conductive loop being located between one end of said yoke and said shaft.

5. The invention as defined in claim 2, wherein:

6. The invention as defined in claim 1, wherein:

spring is provided, said spring being mounted on said carriage means to urge said stylus in a direction away from said platen means.

7. The invention as defined in claim 6, wherein:

8. The invention as defined in claim 1, wherein:

9. An electromagnetic actuator comprising:

a base; t

a movable conductive loop for connection to a member to be mechanically actuated by movement thereof;

means to guide movement of said conductive loop on said base in the plane of said conductive loop;

connecting means selectively operable to open and to short circuit said conductive loop; and

driver means to produce magnetic flux in a location linking said conductive loop, said driver means causing the amount of said linking flux to change abruptly for inducing a current in said conductive loop.

10. The invention as defined in claim 9, wherein:

said connecting means includes a selectively operable switch which can be opened or closed, said switch being connected in series with said conductive loop to short circuit the same when the switch is closed, said abrupt change in flux leaving said conductive loop motionless when said switch is open, said abrupt change in flux causing a force to be applied to said conductive loop when said switch is closed, said force being transmitted to said member to move the same, closure of said switch permitting a current to be induced in said conductive loop which induced current produces its own magnetic field that reacts with that produced by said driver means and causes said force to be applied to said conductive loop.

Claims

1. A printer comprising: a base; a carriage means mounted on said base; platen means mounted on said base in a manner to support a recording medium adjacent said carriage means; an elongated axially movable stylus having first and second ends; a conductive loop fixed relative to said second stylus end; means to produce relative movement between a recording medium and said first stylus end in a direction approximately normal thereto; means mounted on said carriage means to guide said axial movement of said stylus; driver means to produce magnetic flux in a location linking said conductive loop, said driver means causing the amount of said linking flux to change abruptly; and a selectively operable switch connected in series with said conductive loop to short circuit the same when the switch is closed, said abrupt change in flux leaving said conductive loop axially motionless when said switch is open, said abrupt change in flux causing a force to be applied to said conductive loop when said switch is closed, said force being transmitted to said stylus to move the same axially to cause said first end thereof to strike a recording medium when such is supported in position therefor by said platen means as aforesaid, and to make a detectable recording mark on said recording medium where said stylus first end strikes said record medium, closure of said switch permitting a current to be induced in said conductive loop, which induced current produces its own magnetic field that reacts with that produced by said driver means and causes said force to be applied to said conductive loop.

2. The invention as defined in claim 1, wherein: means are provided to prevent said conductive loop from rotating about the axis of said stylus.

3. The invention as defined in claim 2, wherein: a spring is provided, said spring being mounted on said carriage means to urge said stylus in a direction away from said platen means.

4. The invention as defined in claim 3, wherein: said driver means includes a magnetic circuit having a fixed magnetic yoke including an elongated, non-circular magnetic shaft spaced a short distance therefrom, a maximum flux being established in said magnetic circuit when said shaft is located in one angular position, a minimum flux being established in said magnetic circuit when said shaft is located in another angular position, means to rotate said shaft, means to establish a magnetomotive force in said magnetic circuit, said conductive loop being located between one end of said yoke and said shaft.

5. The invention as defined in claim 2, wherein: said driver means includes a magnetic circuit having a fixed magnetic yoke including an elongated, non-circular magnetic shaft spaced a short distance therefrom, a maximum flux being established in said magnetic circuit when said shaft is located in one angular position, a minimum flux being established in said magnetic circuit when said shaft is located in another angular position, means to rotate said shaft, means to establish a magnetomotive force in said magnetic circuit, said conductive loop being located between one end of said yoke and said shaft.

6. The invention as defined in claim 1, wherein: spring is provided, said spring being mounted on said carriage means to urge said stylus in a direction away from said platen means.

7. The invention as defined in claim 6, wherein: said driver means includes a magnetic circuit having a fixed magnetic yoke including an elongated, non-circular magnetic shaft spaced a short distance therefrom, a maximum flux being established in said magnetic circuit when said shaft is located in one angular position, a minimum flux being established in said magnetic circuit when said shaft is located in another angular position, means to rotate said shaft, means to establish a magnetomotive force in said magnetic circuit, said conductive loop being located between one end of said yoke and said shaft.

8. The invention as defined in claim 1, wherein: said driver means includes a magnetic circuit having a fixed magnetic yoke including an elongated, non-circular magnetic shaft spaced a short distance therefrom, a maximum flux being established in said magnetic circuit when said shaft is located in one angular position, a minimum flux being established in said magnetic circuit when said shaft is located in another angular position, means to rotate said shaft, means to establish A magnetomotive force in said magnetic circuit, said conductive loop being located between one end of said yoke and said shaft.

9. An electromagnetic actuator comprising: a base; a movable conductive loop for connection to a member to be mechanically actuated by movement thereof; means to guide movement of said conductive loop on said base in the plane of said conductive loop; connecting means selectively operable to open and to short circuit said conductive loop; and driver means to produce magnetic flux in a location linking said conductive loop, said driver means causing the amount of said linking flux to change abruptly for inducing a current in said conductive loop.

10. The invention as defined in claim 9, wherein: said connecting means includes a selectively operable switch which can be opened or closed, said switch being connected in series with said conductive loop to short circuit the same when the switch is closed, said abrupt change in flux leaving said conductive loop motionless when said switch is open, said abrupt change in flux causing a force to be applied to said conductive loop when said switch is closed, said force being transmitted to said member to move the same, closure of said switch permitting a current to be induced in said conductive loop which induced current produces its own magnetic field that reacts with that produced by said driver means and causes said force to be applied to said conductive loop.