US3596746A

US3596746A - Multitype wheel printing machine

Info

Publication number: US3596746A
Application number: US860524A
Authority: US
Inventors: Jean-Pierre Murat
Original assignee: Sagem SA
Current assignee: Sagem SA
Priority date: 1968-09-25
Filing date: 1969-09-24
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03
Also published as: DE1948204A1; FR1590699A; GB1267745A

Abstract

Teleprinting machine in which the characters are distributed on a plurality of type wheels. It comprises a type wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to both said striker and type wheel carriages a step-by-step movement, means for receiving character signals expressed in the binary code, a rotary selector device and a traversing selector device respectively controlling the selector shaft in rotation and the type wheel carriage in translation. These two devices include a reciprocating crank and link mechanism controlled by the receiving means, two racks and a pinion, the two racks meshing at two diametrically opposite points of the pinion, two toggles respectively connecting the two racks to the crank and link mechanism, a rack selector switching member controlled by the receiving means for selecting a rack out of the two ones, and a plurality of mobile stop members selectively positioned by the receiving means on the path of the toggles for stopping the racks at quantified predetermined positions. The pinion of the rotary selector device drives the selector shaft and the pinion of the traversing selector device drives the type wheel carriage.

Description

United States Patent [72] Inventor Jean-Pierre Murat Argenteuil, France [21] Appl. No. 860.524 [22] Filed Sept. 24. 1969 [45] Patented Aug. 3, 1971 [73] Assignee Societe D'Applications Generales DElectricite et de ecanique Paris, France [32] Priority Sept. 25,1968 [33] France v [31] 167,510

[54] MULTITYPE WHEEL PRINTING MACHINE 4 Claims, 20 Drawing Figs.

[52] 11.8. C1 197/55, 178/34, 101/110, 19 7/18 [51] 1nt.Cl B4lj 1/26 [50] Field of Search l97/18,55; 178/34; 101/110 [56] References Cited UNITED STATES PATENTS 1,150,382 8/1915 Paulson et al 197/55 3.042.174 7/1962 Howard 197/55 X 3,228,510 1/1966 Howard... 178/34X 3,286,806 11/1966 Schoenfelder. 197/55 X 3,353,648 11/1967 Amada et al 197/55 3,374,373 3/1968 Takenaka 178/34X 3,378,127 4/1968 ClaryetaL. 197/55 3,400,798 9/1968 Smith 197/55 X 3,404,765 10/1968 Gassino et al 197/55 3,405,794 10/1968 Means 197/55 3,455,428 7/1969 Shida et al. 197/55 Primary E.run|inerEdgar S. Burr Attorney-Abraham A. Saffitz step-by-step movement, means for receiving character signals expressed in the binary code, a rotary selector device and a traversing selector device respectively controlling the selector shaft in rotation and the type wheel carriage in translation. These two devices include a reciprocating crank and link mechanism controlled by the receiving means, two racks and a pinion, the two racks meshing at two diametrically opposite points of the pinion, two toggles respectively connecting the two racks to the crank and link mechanism, a rack selector switching member controlled by the receiving means for selecting a rack out of the two ones, and a plurality of mobile stop members selectively positioned by the receiving means on the path of the toggles for stopping the racks at quantified predetermined positions. The pinion of the rotary selector device drives the selector shaft and the pinion of the traversing selector device drives the type wheel carriage.

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Jean-Pierre '1 By 7%MZW 4 PATENTEU AUB 31911 3, 596, 746

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Jean-Pierre -T @FIGB /l wiw PATENTED AUG 3|91| SHEET [18 0F 12 Jean-Pierre M" M PATENTED AUG 31911 SHEET 07 0F 12 INVE NTOR: Jean-Pierre T r M PATENTEDAus 3191: 3,596,74

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SHEET 09 [1F 12 Qmm Wmm WWW wQm vmw w QM 3 mqwi NZVE ATTORNZZ PATENTEU AUG 3 I971 SHEET 11 0F 12 INVEN'IOR:

-Pierre Jean Bwflt MULTITYPE WHEEL PRINTING MACHINE The invention relates to a multitype wheel printing machine comprising a printing unit having a plurality of type or character wheels, a rotary selector device and a traversing selector device, operating simultaneously but independently of one another, and a movable striker carriage means, the machine being so designed that during each printing cycle is controlled by coded electrical signals representing characters and actuating decoding electromagnets whereby the required character is brought into the right printing position at the right time to be then thrown by the striker carriage against the paper reel.

Printing machines have been known for many years in which the characters are disposed on separate character-carrying members which are called type'wheels, the number of type wheels being less than the number of characters. The striking rate'of these machines is limited by the inertia and/or distance of travel of the moving members.

It is a mainobject of the present invention to provide a printing machine of the kind specified which enables the striking rate to be increasedby reducing the mass of the moving printing members and the distance which they travel.

Among the novel features of the invention are the following: the rotary selector device and the traversing selector device are each formed by a mechanical linkage comprising a singlerevolutionclutch, a reciprocating ,crankand link, two racks each driven by a toggle and meshing at two diametrically opposite points of a pinion, a rack-selecting switching member,

and a cage bearing a predetermined number of mobile stopsand a fixed stop, the switching member and the mobile stops being positioned by electromagnets, the-arrangementbeing such that during the first movement'of the reciprocating crank, the rack not selected is very quickly stopped as soon as its toggle is folded on contact with the switching member, so that the selected rack is-the only rack to follow the initial movement. The other rack is rejected until its toggle is folded in its turn on-contact with the selected stop of the cage, and on this contactwith the stop, thepreviouslyselected rack and the member controlled thereby are immediately immobilized by a locking means. During the return movement of the reciprocating crank, all the displaced members-are returned to their initial positions. The movable striker" carriage means which cooperates with a stepping mechanismcomprises a carriage mount for the type wheels driven by a cable of the'stepping mechanism, the mount sliding on two shafts, one of which is adapted to berotated by a clutch by one-half turn at'the start of each printing cycle. The carriage means includes a fork and a sleeve device which cooperates withthe' clutch so that the rotation of the type. wheel from a maximum withdrawn position of the printing carriage to a minimum withdrawn position initiates the return to the maximum-withdrawn position only on the receptionof a signal received from an auxiliary clock.

The auxiliary clock emits the signal at the relatively low rate of reception of the codedsignals which control the pulling of a character on the typev wheel.

The objects, specific features and advantages of the invention will become more apparent from a reading of the following detailed description of -a preferred embodiment, reference being'made to the accompanying drawings, wherein:

FIG. 1 is a partly sectioned and partial diagrammatic view of a printing machine according to the invention;

FIG. 2 is a partly sectioned view of the rotaryselector device of the printing machine, taken along the line II-Il in FIG. 2;

FIG. 3 is a partly sectioned view of the rotary selector device of the printing machine, taken along the line Ill-Illin FIG. 2;

FIG. 4 is a partly sectioned-view of the rotary selector device of the printing machine, taken along the line IV-IV'in FIG. 5;

FIG. 5 is a partly sectioned view of the rotary selector device of the printing machine, taken along the line V-V in FIG. 4, and viewed from the back of the printing machine;

FIG. 6 is a partly sectioned view of the rotary selector device of the printing machine, taken along the line VI-VI in FIG. 4;

FIG. 6A is a detail shown in perspective of the singleswitching device of the rotary selector device of the printing machine;

FIG. 7 is a detailed partly sectioned view of the lower righthand portion of FIG. 2, to an enlarged scale, showing the withdrawable heel system of the rotary selector device;

FIGS. 8 and 9 are partial views of the toggle and rack in FIG. 2, in an enlarged scale, at the start of their rising and after stopping against a movable stop respectively;

FIG. 10 is a partly sectioned view of the traversing selector device of the printing machine, taken along the line X-X in FIG. 11;

FIG. II is a partly sectioned view of the traversing selector device of the printing machine, taken along the line Xl-XI in FIG. 10;

FIG. 12 is a partly sectioned view of the traversing selector device of the printing machine, taken along the line XII-XII in FIG. 14;

FIG. 13 is a partly sectioned view of the traversing selector device of the printing machine, taken along the line XIII-XIII in FIG. 12;

FIG. 14 is a plan view of the traversing selector device of the printing machine;

FIG. 15 is a detailed partly sectioned view of the upper lefthand portion of FIG. 12, to an enlarged scale, showing the locking of the traversing selector device;

FIG. 16 is a sectioned view of the printing carriage taken along the line XVI- XVI in FIG. I7;

FIG. 17 is a partial cross section taken along the line XVII-XVII in FIG. 16, the printing unit being in the maximum withdrawn position;

FIG. 18 is similar to FIG. 17, showing the printing carriage in the minimum withdrawn position, and

FIG. 19 is similar to FIG. 17, showing the printing carriage in the printing position.

FIG. I diagrammatically shows the main members of a printing-machine according to the invention.

In flanges I1, 12 of the frame (not otherwise shown) there is journaled a shaft 29 whose angular position is controlled via a pinion 291 by a rotary selector device 2. The corresponding printing information is transmitted to a wheel printing carriage 5 'by a pinion (not shown in FIG. 1). In a vertical plane disposeda slight distance infront of the shaft 29 in an articulated parallelogram 39 whose lower articulations are formed by fixed pivots connected to the frame, the left-hand upright 392 ofwhich (shown in FIG. I) has its position controlled by a traversing selector device 3. The corresponding information is transmitted to the printing carriage 5 by a cursor 394. FIG. 1 also shows'a paper reel 59 upon which printing is effected, a

stepped driving device 4 for stepwise movement of the striker carriage and a striker carriage 6 which will be described hereinafter.

To simplify the description of the relative orientation of the machine parts, use is made of a trirectangular trihedron, shown in FIG. 1, in which plane P is horizontal plane 0 is vertical'and parallel to the flanges l1, 12 of the machine, and plane R is vertical and perpendicular to the flanges 1 1, 12.

The rotary selector device 2 as shown in FIGS. 1,2,7 and 8 is constructed as follows. Mounted on a drive shaft 20 journaled in the frame (cf. FIGS. 2 and 7, whose planes are of orientation R) is a one turn clutch (not shown) which drives eccentric 201'and a cam 202 in the direction of the arrow F2 and mounted for free rotation on the eccentric 201 is the head of a link 203. A lever 2l'is pivotably mounted by one of its ends around a pivot 21a connected to the frame and is articulated at an intermediate point 21b to the base of the link 203 For each revolution of the clutch, the lever 21 performs a reciprocating pivoting movement in its plane, as indicated by the arrow F'2. In the drawings, the lever 21 is shownin its inoperative or initial position for eachcycle, corresponding to a lower dead center position.

Articulated to the free end of the lever 21, in two vertical planes symmetrical to that of the lever, are two identical toggles 22, 22' (see FIG. 8). Each of these toggles is articulated at a first end, 22 being articulated at 22a (the bottom end in FIG. 2) to the lever 21. Each lever is articulated at an intermediate point 22b between the two members, and lastly each is articulated at its other end 220 (the top end in FIG. 2) to an associated rack 23.

The two symmetrical racks 23, 23' are also disposed in two vertical planes symmetrical to that of the lever 21. Each of the two racks, for instance 23, is made up of two analogous parts offset in relation to one another by their common width in the horizontal direction, but rigidly interconnected by a bar 23a. The first rack is guided and combed" by two

studs

23b, 23c which are fixedly connected to the frame, so as to be able to move only in its plane and only in the vertical direction. Its upper portion has a flanged lateral vertical toothed edge 23d forming the part similar to a comb. The

toothed flanges

23d, 23d of the two racks mesh symmetrically with the pinion 291 mounted at the end of the rotary selector shaft 29. The pinion 291 is rigidly fixed to the shaft 29 via deformable hub 292 tightened by a screw and unitary with the pinion. In the gap between the hub 292 and the pinion 291 a collar of the latter is supported by a bearing 293 inserted in the left-hand flange 11 of the frame (FIG. 1).

Each toggle, as 22, is urged at its lower end by a spring 22d hooked to the lever 21, into a position in which the toggle bears via an intermediate heel 22c against the associated rack 23. Each toggle, as 22, has at its top end 220 connected to the associated rack 23 an aperture 22f such that an upper heel 22g of the toggle can move, in relation to an intermediate heel 232 of the associated rack, between the level of the latter heel and a slightly lower level. In the rest or reset position shown in FIG. 2 the toothed parts 23d of the racks 23, 23', are set at the same height so that the level of the axis of the pinion is the central level which is common to both toothed parts.

Towards the front and the left-hand side (as viewed in FIGS. 1 and 2) ofthe top parts of the racks 23, 23' in the mean position and slightly; above the intermediate heels, 23c, a cage 24 is disposed as shown particularly in FIG. 4, 5, 6 and planes 0, R and P respectively. The cage 24 has a U-shaped outline in horizontal section which can be seen in FIG. 6 and comprises two vertical planar arms which are guided and combed" respectively by two studs 24b, 240 connected to frame so that the arms can move only in their plane and only in the vertical direction. Three horizontal flat bars act as movable stops 241-243 (FIG. 4) and are disposed one above the other to slide in narrow apertures in two opposite vertical walls. A fourth stop 244 (FIG. 4) is disposed above 243 and is fixed in relation to the cage 24. The levels of the four stops are regularly spaced and h is the distance between two consecutive stops. The cage 24 can take up two positions. The bottom position of the cage 24 (as shown in FIGS. 4 and is defined by a pawl 245 (FIG. 5) pivoting around a pivot 245a connected to the frame and urged by a spring 245!) which is hooked to the frame in the direction of a pin 24d of the cage.

The top position of the cage 24 is defined by a stop 240 connected to the frame toward which the cage is urged by a spring 24] hooked to the frame. The difference in level between the top and bottom positions of the cage is equal to h/2. The relatively long lower arm of the cage 24 terminates in a lug 243 which comes into place just below the edge of the lever 21 when the latter is in its bottom dead center position.

Each of the movable stops 241-243, for instance 243 (FIG. 6) has two large lateral pins 243a, 243'a projecting on the side of the racks 23, 23' to cooperate therewith, and on the same side a small lateral pin 243b is adapted to cooperate with the major arm 254 ofa return lever 25 (FIG. 4). On the opposite side, outside the cage 24, each movable stop, as 243 abuts the cage (FIG. 6).

A flat bent return lever 25 has a minor arm 251 and a major arm 252 (cf. more particularly FIG. 4). The lever 25 mounted to pivot around a pivot 25a connected to the frame is urged by a spring 25b (FIG. 4) hooked to the frame so that its minor arm 251 remains in contact with the lever 21 (FIG. 4) in the rest position and is provided with a withdrawable movable heel 211 of said lever 21 (cf. FIG. 7). The heel 211 has the form of a section of an angle iron and one of its' flanges is maintained against the flat surface. Its second flange is maintained against the edge of the lever 21, by means of two apertures out in the first-mentioned flange which cooperate with the two

studs

21c, 21d of the lever 21. These two apertures also define the two end positions which the heel 211 can take up in relation to the lever 21 in a direction which is showndiagrammatically by the arrow F"'2'in FIG. 2. The second flange of the heel 211 has two recesses, a first recess which enables the minor arm 251 of the lever 25 to escape from the heel 211 under the action of the spring 25b so as to come in direct contact with the lever 21, and a second recess which enables the position of the heel 211 to be controlled. The heel 211 is urged by a spring 212 hooked to the lever 21 into its rest position (shown in FIG. 7) in which the arm 2510f the lever 25 is in contact with the heel 211 and not with the lever 21. A flat bend lever 204 is mounted to pivot around a pivot 204a connected to the frame; when the lever 21 is in its lower dead center position (as shown in FIG. 7) the lever 204 urged by a spring 204b connected to the frame tends to come into contact, via its minor arm and an end flange 2040, with the cam 202; the major arm of the lever 204 then engages by its free end in the second recess in the heel 211, so that the latter is then in its rest position (shown in FIG. 7); when the lever 204 has escaped by its two ends respectively from the cam 202 and the heel 211, its travel under the actionof its spring 204b is limited by a stop 204d connected to the frame.

A switching member 26 (shown more particularly in FIGS. 6 and a is mounted to pivot on a pivot 26a connected to the frame. More precisely, the switching member 26 is formed by a triangular flat with a central aperture and having on the side of the

racks

23, 23 a raised edge with two upper lateral framing projections 26b, 26'b and on the opposite side a controlled arm 26c. The switching member 26 is so mounted that its lateral projections are at a level slightly higher than the level of the intermediate heels, as 23c, of the racks 23, 23' in the inoperative position. The switching member 26 can take up two end positions defined by a stop 26d connected to the frame and cooperating with one or other of the sides of the central aperture the-first position is called the rest position (shown in FIG. 6) in which the projection 26'b is in the path of the rack 23', the second being the set position in which the projection 26 b is in the path of the rack 23. The switching member 26 is urged by a spring 26e connected to the frame into its rest position.

Mounted for free rotation on the eccentric 201 (see FIG. 2) is not only the head of the link 203 mentioned hereinbefore, but also the head of a lever 205 mounted to pivot around a pivot 2050 connected to the frame. A bolt member 27 mounted to pivot around a pivot 27a connected to the frame has two arms 271, 271' bearing respectively two identical segments 272, 272' disposed in the same vertical planes as the racks 23, 23'. Each of the sectors, for instance 272, has a stepped free edge forming an angle of about 45. The sectors, as 271-272, are each urged by a spring, as 27b connected to the arm 27 and to the frame, into a position in which the arm 271 bears against a finger 205b supported by the free end of the lever 205. The right-angled notches of the

segments

272, 272 of the bolt 27, for instance those of the segment 272, are

each adapted to cooperate by wedging with the closest lower right-angle part 23f of the associated rack 23.

Levers 281, 282 (FIG. 5) are respectively the armatures of two electromagnets 281e, 282a; depending on whether the latter are set or reset, the levers 281, engage or do not engage of the recesses in the movable stops 241-243, The position of the pawl 245 (FIG. 4) is controlled by a lever 283 which is the armature of a third electromagnet 283e, depending on whether the latter is in its set or reset position, the pawl 245 is in its set or reset position in the sense defined hereinbefore. The position of the switching member 26 is controlled by a lever 284 which is the armature of a fourth electromagnet 284e; in dependence on whether the latter is in the set or reset position the switching member 26 is in the set or reset position in the sense defined hereinbefore.

The rotary selector device 2 described hereinbefore operates as follows: when any electric signal is received, and in dependence on the coding thereof, the electromagnets 281e 284e, independently of one another, remain reset or are set. It will first be supposed that 283e and 2842 are reset, 281e and 282e assuming as a whole one of four possible combinations.

When the same signal is received, the clutch of the device 2 rotates by one revolution in the direction indicated by the arrow F2 in FIGS. 2 and 7. Immediately the cam 202 tilts the lever 204 clockwise (as viewed in FIG. 7) so pulling the withdrawable heel 211 into its set position. Consequently, under the action of its spring b the return lever 25 suddenly drops into the first recess in the heel 211; this rapid counterclockwise rotation (as viewed in FIG. 4) of the lever 25 equally suddenly releases the movable stops 241-243 and, under the action of their respective springs, each immediately assumes a predetermined position bearing against either one of the

levers

281, 282 or the cage 24. Because of the relationship between the length of the major arm 252 and the minor arm 251 of the lever 25, the displacement of the lever 25, as soon as it starts to escape from the stops 24l-243, is a multiple of the thickness of the withdrawable heel 211.

On the other hand the lever 21 driven by the link 203 effects a turning reciprocating movement in its vertical plane corresponding to the direction indicated by the arrow P2 in FIGS. 2 and 7, first rising. Consequently, the lever 204, after escaping on the one hand from the cam 202 and on the other from the heel 211, is returned by its spring 204b to its stop 204d. The lever 21 also causes the two toggles 22, 22' to rise and then, once the clearance of the apertures, as 22f (FIG. 8) has been resumed, the associated

racks

23, 23 rise. However, in the embodiment chosen in which the switching member 26 is reset, the projection 26'b thereof almost immediately stops the rack 23 by means of the intermediate heel 23'e thereof then; the associated toggle 22' bends at its intermediate articulation 22'b. Consequently, the rack 23 is the only one to rise and, as a result of the rotation of the pinion 291, the rack 23' drops to the same extent, increasing the bending of the associated toggle 22'. This movement continues until the rack toggle 23-22 is stopped by one of the movable stops 241-243 (i.e., by the large lateral pine 243a of one of these stops) or by the fixed stop 244, abutted by the upper heel 22g of the toggle and the intermediate heel 232 of the rack. At that moment, the toggle 22 bends in its turn at its intermediate articulation 22h (cf. FIG. 9), while the rack 23 driven by the inertia of the movable members applies its heel 23e positively against the stop abutted.

In the particular case described, the four possible combinations of reset or set conditions of the two

electromagnets

281e, 282e and therefore of the stops 241-243, to which the fixed stop 244 should be added enable the rack 23 to be stopped at four levels regularly spaced out by a constant distance I1. ln known manner the positions of the recesses 2410-2431' of the movable stops can be calculated to control, via the

levers

281, 282 and taking into account the fixed stop, these four equidistant stoppages of the particular rack. Corresponding to these levels are regularly spaced out angular positions of the shaft 29 which themselves correspond for instance to the characters numbered 1, 3, 5, 7 of the type wheels.

The lever 205, at the same time as 21, has now also effected a pivoting reciprocating movement in its vertical plane, starting by rotating around its axis 205a counterclockwise (as viewed in FIG. 2). Consequently, the bolt 27, under the action of its spring 2 27b has made a pivoting reciprocating movement shown by the arrow F" starting by coming close to the rack 23, so that at the precise moment when the rack is positively stopped by the stop abutted, the associated segment 272 is wedged by one of its notches on the lower angle 23f of said rack. The rack is thus rigidly stopped, since his wedged at both ends.

If initially the electromagnet 283e is energized, the associated lever 283 moves the pawl 245 away from the pin 24d of the cage 24. Consequently, the cage 24 is immediately forced by its spring 24f into its top position against the stop 24e. This upward displacement over a distance 12/2 of the cage 24 causes the four angular positions which the shaft 29 can adopt to correspond to the characters numbered 2, 4, 6, 8 of the type wheels.

If the electromagnet 284e is first energized, the associated lever 284 immediately moves the switching member 26 from its previous reset position to its set position in which the projection 26b of the switching member is on the path of the rack 23. This switching of the switching member 26 causes the eight angular positions which the shaft 29 can adopt to correspond to the characters numbered l'-8' symmetrically disposed in relation to the preceding ones on the type wheels. The rising movement of the lever 21 continues, and the rack 23 (or 23) is locked as has been stated hereinbefore, and the toggles 22, 22' continue to increase the bending of their intermediate articulations until the lever 21 reaches its top dead center position, the positions of the racks 23, 23' remaining unchanged as in the first part of the consequent drop of the lever 21. A certain amount of time is therefore available which is used for striking.

The descending movement of the lever 21 continuing, the result is that all the members are brought back into their initial or inoperative positions: the toggles 22, 22' when bent resume contact by their intermediate heels, as 222, with the associated

racks

23, 23 and then pull these racks, the previously immobilized rack having in the meantime been released by the removal ofthe associated segment of the bolt 27, so as to bring back the racks and the pinion 291 into their mean starting positions; the return lever 25 which has constantly followed the lever 21 returns at the same time as the latter and resumes contact with the small pins, as 243b, of he movable stops so as to return the latter into their starting positions; possibly the lever 21 resumes contact with the lug 24g of the lower arm of the cage 24 to return the latter into its bottom position immediately locked by the pawl 245; on completion of the cycle, the cam 202 resumes contact with the lever 204.

The traversing selector device 3 greatly resembles the rotary selector device 2. As a result, the description of the structure of the device 3 is greatly simplified and can be confined to emphasizing its differences. Like members or like functions of the devices 2, 3 have like references distinguished only by their first digit (2 and 3 respectively). The words right hand and left hand" to be used in the following description must be understood to apply to the right-hand and Left-hand sides ofthe machine seen from the front or as in FIG. 1.

The lever 31 driven by a one-turn clutch (not shown) performs a reciprocating pivoting movement in its plane. In FIGS. 1, 10, 12 and 15 whose planes are all of orientation R, the lever 31 (!FIG. 10) is shown in its reset position or starting position for each cycle, corresponding to a right-hand side dead center position, and the reciprocating movement of the lever is symbolized by an arrow F The two couples of racks and toggles 32, 33 and 32', 33' (FIG. 10) are similar to those of the device 2 but are of generally horizontal orientation and move from left to right or from right to left. The

racks

33, 33 symmetrically mesh with a pinion 391 (FIG. 10) mounted loosely on a stud 391a connected to the frame. Only one of the racks, for instance 33, is connected to the left-hand upright 392 of the articulated parallelogram 39 by a link 39b. The other rack 33' is not connected.

A cage 34, whose U-shape in vertical section can be seen in FIG. 13 is similar to that of the device 2 except for the following points. It has only one fiat horizontal arm. The cage and the arm cooperate with two studs 34b, 340 (FIG. 12) which are perpendicular to one another, so that the cage is guided and "combed" so that its arm cannot move except in its plane and in the direction (P,R). The cage 34 carries only two movable stops 342, 343 (FIGS. 12 and 14) sliding in slots in the cage and a fixed stop 344 connected thereto. The vertical planes of the three stops are suitably spaced out in a manner to be explained hereinafter. The cage 34 can move only over an extremely small distance defined by cooperation of a fixed stop 34c (FIG. 12) connected to the frame and notches 3411 cut in its vertical lateral walls; its reset position, in which it is returned by a tension spring 34f connected to the frame is on the right-hand side. Lastly, the top of the upper surface of the cage 34 has a boss 34k whose position can be adjusted longitudinally with respect to the cage. Each of the mobile stops 342, 343, for instance 343, has substantially identical structure as of the like elements of the device 2. The same is true for the flat bent return lever 35, the withdrawable heel 311 (FIG. 7 remaining completely valid after being rotated 90 clockwise), the switching member 36, the

levers

381, 382 of the movable stops and the lever 384 of the switching member, which are all three, as before, armatures of electromagnets. The very small movement of the cage taking place every time the toggle racks are brought into operation is caused only by the thrust of the latter against the movable or fixed stops 342-344.

On the other hand, the locking device for the racks is completely different from that of the device 2 and requires a full description (FIG. 15).

An end of a flat lever 306 is articulated to the pivot 32a by means of which the

toggles

32, 32 are articulated to the lever 31. The second end of the lever 306 has an upwardly extending lug 306b and is guided and combed" by a stud 33: by means of an aperture 3060. The lever 306 bears laterally a first flat pawl 373. The pawl 373 is mounted to pivot around a pivot 3730 connected to the lever 306 and has an upwardly lug 373k. Its position is always determined by cooperation between its lower edge 373e, the end of which has a concave recess, and a fixed stud 373d connected to the frame and against which the pawl 373 is returned by a torsion spring 373e.

A second substantially flat pawl 374, mounted to pivot around a shaft 374a connected to the case 34, has a lug 374b directed to the right and an end 3740 adapted to cooperate with the lug 306b of the lever 306. The pawl 374 is urged to rotate clockwise (as viewed in FIG. 15) by a torsion spring 374d. A bolt 375 of generally flat T-shape and mounted to pivot around a shaft 375a connected to the frame has on its right-hand side a downwardly directed lug 375b adapted to cooperate with the boss 34k of the cage 34 and on its left-hand side an upwardly directed tooth 375d adapted to cooperate with a notched segment which will be described hereinafter. Substantially halfway between the tooth and the shaft are a lateral pin 375: adapted to cooperate with the lug 374): of the second pawl, and an end 375e adapted to cooperate with the lug 375b of the first pawl. The bolt 375 is urged to rotate clockwise (as viewed in FIG. 15) to become operative by a tensile spring 375] attached to the frame. Lastly, a tooth segment 376 attached to the upper horizontal transverse member 393 of the articulated parallelogram has jags 376c whose shape exactly correspond to that of the tooth 3750' of the bolt 375. The traversing selector device 3 operates similarly to the device 2 and only the differences will be emphasized.

When any electric signal is received, based on the coding thereof, the electromagnets 381e-384e remain inoperative or come into operationindependently of one another. As shown in FIGS. 13 and 14, it will be assumed that 384e remains inoperative so that 381e and 382e, as a whole, will assume one of four possible combinations. When a character signal is received, the clutch of the device 3 rotates by one revolution in the direction of the arrow F in FIG. 10. Under the action of a cam 302 and a lever 304, a withdrawable heel 311 immediately enables the return lever 35 to escape and give the

stops

342, 343 the necessary freedom of movement.

On the other hand, the lever 31 effects a reciprocating pivoting movement in its vertical plane corresponding to the arrow F',, in FIGS. 10 and 15, starting by rotating counterclockwise (as viewed in FIGS. 10 and 15). The lever 31 thus displaces to the left the two toggles 32, 32' and then, by means of the latter, the two

racks

33, 33. However, in the example selected, with the switching member 36 in the rest position, the latter almost immediately stops the rack 33'. Consequently the rack 33 is the only one to be displaced to the left and, as a result of the rotation of the pinion 391, the rack 33' returns to the same extent to the right, increasing the bending of its associated toggle 32. This movement continues until the

rack toggle

33, 32 is stopped by one of the

movable stops

342, 343 i.e., by the large lateral pin 343a of one of these stops) or by the fixed stop 344 abutted by the left-hand end heel of the toggle and the intermediate heel of the rack. At that moment, the rack 33 has repelled the left-hand upright 392 of the articulated parallelogram to the left to a predetermined extent.

In the particular case described, the four possible combinations of reset or set conditions of the two electromagnets 38le and 382e and therefore of the

movable stops

342 and 343, and of the fixed stop 344 enable the rack 33 to be stopped in three suitably spaced vertical planes. Corresponding to these planes are translational positions regularly spaced in projection on a fixed horizontal plane of the upper horizontal member 393 of the articulated parallelogram. These positions bring the

wheels

534, 535, 536 into the vertical striking plane A (FIG. 1) which is positioned between wheels 53;, and 534, when carriage 5 is at rest.

When the rack toggle pair 33-32 is stopped in its leftward movement by a movable or fixed stop, the cage 34 is pushed to the left against its return spring 34f to the extent allowed by cooperation between the stop 34c and the notches 3411. Consequently the bolt 375, which is urged by its spring 375f and whose lug 375b can now drop on to the right of the boss 34k from the top of the cage, turns by a small angle clockwise (viewed in FIG. 15) and its toot-h 375d engages very precisely in a jag of the segment 376. Because of the lever 31, the lever 306 has slid to the left, driving the first pawl 373 in the same direction so that the lug 373b therefore has passed to the left of the end 375e of the bolt 375, while finally rotating slightly clockwise (as viewed in FIG. 15) under the action of its spring 3732 and cooperation of its lower ramp 373C with the fixed stud 373d, thus preparing the withdrawal of the bolt which will be described hereinafter. In the case in which electromagnet 384e is brought into operation, the associated lever 384 causes the switching member 36 to go immediately from its precediny rest position into its set position, so that the other projection of the switching member is on the path of the rack 33. This switching of the switching member 36 causes one of the three new translational positions of upper transverse member 393 of the articulated parallelogram to bring one of the

type wheels

53,, 53,, 53 (FIG. 1) into the vertical striking plane A.

The leftward movement of the lever 31 being continued after the parallelogram has been locked, the toggles 32, 32' continue to increase their bending movements until the lever 31 reaches the left-hand dead center position, and the positions of the racks 33, 33' remain unchanged, as in the first part of the return movement of the lever 31. A certain amount of 'time is therefore available and is used for striking.

The movement to the right of the lever 31 continues and results in returning all the members to their initial reset positions. When the first pawl 373 returns to the right, its lug 375b pulls on the end 375e of the bolt so that the latter turns slightly in opposition to its spring and is simultaneously released by its tooth 375d and its lug 375b thus releasing both the articulated parallelogram and the cage 34. The second pawl 374 slides by means of lug 374b over the pin 375c of the bolt to be hooked thereon, thus retaining the bolt in the withdrawn position during the whole return travel in the direction of the rack toggle 33-32 or 33'32, and during the movement of the notched segment 376 of the articulated parallelogram, and also of the cage whose boss 34k is again placed under lug 375b of the bolt. Lastly, the lug 306b of the lever 306 returns the second pawl 374 to its reset position.

The return lever 35 which has continuously followed the lever 31 returns at the same time as the latter and returns or maintains the movable stops in their starting positions.

In the embodiment described the printing machine has only six type wheels which can be positioned by two translations of opposite directions having each three quantified steps. So the cage 34 whose function is to double the number of quantified steps is unnecessary. It becomes necessary when the number of type wheels which is equal to two times the number of quantified steps in a given direction exceeds the number of movable and fixed stops of the racks.

At the end of the cycle the cam 302 resumes contact with the lever 304.

Reference will now be made again to FIG. 1 to describe the stepped driving device 4 which is reversible and normally ensures the regular movement from left to right of the slider 394 and therefore of the printing carriage 5, and of the striking carriage 6, by means of two

cables

41, 42 respectively. Cable 41 runs over pulleys, as 421, of fixed axes and set in a rectangle. Cable 42 runs over pulleys, as 41 1, whose axes are formed by the articulations of the parallelogram 39 and ensures a movement vectorially equal to the preceding movement of the slider 394 in relation to the upper transverse member 393 of the parallelogram, by the sliding of the slider over the transverse member. The stepping device 4 does not form part of the invention and will not be described further. An example of a mechanism of the kind specified can be found in French Pat. No. 1,529,888 of l I May I967 in the applicants name.

The printing carriage 5 is constructed as follows (FIGS. 16 and 17). Mounted on the shaft 29 is a pinion 294, and also a frame 50, which is free to have both translational and rational movements, and has two flanges 51, 51' unitary with two struts 51" and 51" (FIG. 12) and bearing two

shafts

52, 56 journaled in flanges 51, 51'.

Mounted on the shaft 52 at the left-hand end thereof is a toothed wheel 521 attached by a pin to the shaft 52 and meshing with the pinion 294, and mounted on the right-hand side of the shaft are a certain number (five in the embodiment illustrated) of identical yielding hubs 522 keyed to the shaft'52 and alternating with spacer washers 523. Each hub 522 has a radial keying slot over its whole length, a part of which has two flats parallel with the slot through which a screw extends for moving the edges of the slot apart and a cylindrical portion shouldered by said part to which is fixed a toothed wheel 524 whose periphery is identical with that of the toothed wheel 521. Mounted on shoulders of the wheel 52! and on the shoulders formed by each washer 523 enclosed by two of said hubs 522 are a certain number (six in the embodiment illustrated of identical rotary printing members 53. Each printing member comprises two flanges 531, 531' interconnected by a pin 532 and by two

struts

533, 534. Mounted freely for rotation on the pin 532 are a type wheel 535 and a toothed wheel 536 connected to one another for instance by riveting. The toothed wheels 536 of the printing members mesh with the wheel 521 and the wheel 524 so that the type wheels 535 all have the same angular position only controlled by that of the pinion 294 which then selects the extent of rotation.

On the other hand, the frame 50 of the printing carriage has at its front a fin 54 in the form of a rigid strip perpendicularly to the shaft 29 and inserted without clearance between two other rigid strips of the same orientation of a fork 395 rigidly connected to the slider 394. As shown in FIG. 17, the slider 394 is formed by a slide whose outline is exactly circumscribed in the reversed U of the upper transverse arm 393 of the parallelogram 39 and which comprises in its top portion a clamp 396 blocking the cable 41 connected to the stepping mechanism. The traversing position of the printing carriage 5i.e., of the type wheels-is therefore finally determined by the algebric sum of the displacements of the stepping mechanism and of the transverse member 393 of the parallelogram giving a traversing information.

The printing members 53 thus mounted to rotate around the shaft 52 normally bear against a stop "55 of the frame 50 and are returned to said stop by tension springs 551 each attached on the one hand to the strut 533 of the associated member 53 and on the other hand to the frame 50. The other strut 534 of each printing member is adapted to be struck by the hammer of the striker carriage, as will be seen hereinafter, to perform actual printing. Mounted on the shaft 56 for traversing and rotary movement is a sleeve 561 cooperating with a fork 631 extending, as will be seen hereinafter, on the striker device 6 to make sure that the printing unit 5 is in the required position.

A striker carriage 6 is set up by a carriage 60 having two flanges interconnected by struts 62. This carriage is mounted and guided for free translational movement on two

shafts

63, 64 freely journaled in flanges 11, 12 of the machine frame. The striker carriage 6 has a clamp blocking the cable 42 of the stepping mechanism 4, this cable controlling the position of carriage 6.

Mounted on the shaft 63 whose angular position is controlled by a one-turn clutch and auxiliary members (eccentric, link, lever, etc. not shown) is a fork 631 adapted to rotate around to the shaft 63 and to traverse the movement of the carriage, the fork cooperating with the sleeve 561 of the printing unit 5 so that at the start of each printing cycle the shaft 63 rotates clockwise (as viewed in FIG. 17) to turn the printing carriage 5 in the direction opposite to the preceding direction through an angle of the order of 30, thus bringing it from the maximum withdrawn position (FIG. 17) into the minimum withdrawn position (FIG. 18).

Mounted on the shaft 64 whose angular position is controlled by a half-turn clutch (not shown) is a cam 641 having two lobes, as 641b, adapted for rotation around the shaft and for following the displacement of the carriage.

Mounted on the strut 62 of the carriage is a hammer 621. A control arm 621b for the hammer has an end roller 62lc kept bearing against the outline of the cam 641 by a return tension spring 621d connected to the carriage. The striker arm 621e of the hammer is driven by cam 641; when the printing carriage 5 has come into the minimum withdrawn position and when the shaft 64, and therefore the cam 61, rotates counterclockwise through an angle of the order of 60, the hammer rotates clockwise through an angle adequate to strike the strut 534 of the selected printing member and hurl it against the paper reel 59.

The striker carriage operates as follows.

At the start of the printing cycle, only in cases in which the printing carriage 5 has not remained in its minimum withdrawn position, it is returned to such position, because of the operation of the clutch of the shaft 63. The two selected rotary and traversing movements are performed as already described-At the end of the printing cycle, the operation of the clutch of the shaft 64 causes the hammer 61 to tilt and hurls only the selected printing member 53 against the paper reel 59. This member, returned by its spring 551, comes back to the stop of the printing carriage 55. As the rotary selector device 2 and the traversing selector device 3 return to their rest positions they bring the type wheels back into their starting positions.

However, as regards the angular position of the printing carriage 5,'two cases must be distinguished.

If the time elapsing between the preceding signal and a fresh coded signal is long enough (for example more than a tenth of a second) an auxiliary clock (not shown) emits a special signal which again releases the clutch of the shaft 63 and the printing carriage comes into the maximum withdrawn position, enabling the last character struck to be read.

In the opposite case, the clock does not emit this special signal and i the printing unit remains in the minimum withdrawn position.

In reality, the type wheels do not finally return to their starting positions, since at the end of the cycle and/or at the start of the following cycle, the stepping mechanism 4 displaces the slider 394 by one step, and therefore the printing carriage 5 and, at the same time, the striker carriage 6.

What I claim is:

l. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to both said striker and type-wheel carriages a step-by-step movement with respect to said printing medium, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks and a plurality of movable stop members selectively positioned by said receiving means on the path of the toggle connected to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shah for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said type-wheel carriage for positioning a selected type wheel opposite the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.

2. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to both said striker and type-wheel carriages a step-by-step movement with respect to said printing medium, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks, a plurality of movable stop members selectively positioned by said receiving means on the path of the toggle connected to the selected rack, means selectively controlled by said receiving means for displacing said stop members in the direction of the rack movement, whereby each of the stop membercan take selectively two different positions, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said type-wheel carriage for positioning a selected type wheel opposite the striker carriage and means carried by the striker carriage for stricking against the printing medium the type wheel positioned opposite the striker carriage.

3. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type Wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said se cctor shaft, a

striker carriage, a stepping mechanism for imparting to said striker carriage a step-by-step movement with respect to said printing medium along a fixed guide shaft, a stepping mechanism for imparting to said type-wheel carriage a stepby-step movement with respect to said printing medium along a mobile guide shaft, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said mobile guide shaft in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks, and a plurality of movable stop member selectively positioned by said receiving means on the path of the toggle connected to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said mobile guide shaft for selectively positioning the type-wheel carriage with respect to the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.

4. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a

striker carriage, a first cable running on four pulleys located at the four apices of a fixed rectangular frame and connected to said striker carriage, a second cable running on four pulleys located at the four apices of an articulated parallelogram frame and connected to said type-wheel carriage, a stepping mechanism for imparting to both said first and second cables a step-by-step movement with respect to said printing medium respectively along a guide rod forming one side of said fixed rectangular frame and a guide rod forming one side of said articulated parallelogram frame, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means foriselecting a rack out of the two racks and a plurality of movable stop members selectively positioned by said receiving means on the path of the toggle connected to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said articulated parallelogram frame guide rod for selectively positioning the typewheel carriage with respect to the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.

Claims

1. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to both said striker and type-wheel carriages a step-by-step movement with respect to said printing medium, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks and a plurality of movable stop members seLectively positioned by said receiving means on the path of the toggle connected to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said type-wheel carriage for positioning a selected type wheel opposite the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.

2. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to both said striker and type-wheel carriages a step-by-step movement with respect to said printing medium, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks, a plurality of movable stop members selectively positioned by said receiving means on the path of the toggle connected to the selected rack, means selectively controlled by said receiving means for displacing said stop members in the direction of the rack movement, whereby each of the stop member can take selectively two different positions, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said type-wheel carriage for positioning a selected type wheel opposite the striker carriage and means carried by the striker carriage for stricking against the printing medium the type wheel positioned opposite the striker carriage.

3. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type Wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a stepping mechanism for imparting to said striker carriage a step-by-step movement with respect to said printing medium along a fixed guide shaft, a stepping mechanism for imparting to said type-wheel carriage a step-by-step movement with respect to said printing medium along a mobile guide shaft, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said mobile guide shaft in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks, and a plurality of movable stop member selectively positioned by said receiving means on the path of the toggle connecTed to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said mobile guide shaft for selectively positioning the type-wheel carriage with respect to the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.

4. A multitype wheel teleprinting machine comprising a printing medium carrying means, a type-wheel carriage slidable along and rotatable about a selector shaft, a plurality of type wheels mounted on said type-wheel carriage and rotatable about and controlled in rotation by said selector shaft, a striker carriage, a first cable running on four pulleys located at the four apices of a fixed rectangular frame and connected to said striker carriage, a second cable running on four pulleys located at the four apices of an articulated parallelogram frame and connected to said type-wheel carriage, a stepping mechanism for imparting to both said first and second cables a step-by-step movement with respect to said printing medium respectively along a guide rod forming one side of said fixed rectangular frame and a guide rod forming one side of said articulated parallelogram frame, means for receiving character signals expressed in binary code, a rotary selector device and a traversing selector device respectively controlling said selector shaft in rotation and said type-wheel carriage in translation, each of said devices including a reciprocating crank and link mechanism controlled by said receiving means, two racks and a pinion, said two racks meshing at two diametrically opposite points of said pinion, two toggles respectively connecting said two racks to said crank and link mechanism, a rack selector switching member controlled by said receiving means for selecting a rack out of the two racks and a plurality of movable stop members selectively positioned by said receiving means on the path of the toggle connected to the selected rack, said stop members cooperating with said toggles for allowing the same to fold when the toggle meets up with a stop member and thereby stopping the rack, the pinion of said rotary selector device driving said selector shaft for positioning said type wheels in selected radial positions and the pinion of said traversing selector device driving said articulated parallelogram frame guide rod for selectively positioning the type-wheel carriage with respect to the striker carriage and means carried by the striker carriage for striking against the printing medium the type wheel positioned opposite the striker carriage.