Mechanical Type-printing Apparatus

Abstract

The use of Computer Assisted Instructional Systems and other electronic data processing systems is enhanced by a simple, low-cost, key-responding mechanical type-printing apparatus for printing human and machine readable characters of a family of type of which each character has no more than 12 segments. The generic type family format is a medianly quartered parallelogram (MQP) embracing both slanted and upright printing, the latter being more specifically in the format of an orthogonally quartered rectangle (OQR). The printing apparatus comprises a multiple of printing blade elements arranged as a subassembly for printing short straight line segments by impressing the ends of the blade elements on the record medium against a platen. Liquid ink is fed to the blade elements made up of several leaves between which the ink flows by way of capillary action. The proper blades are selected for printing the corresponding segments making up a desired character by means of a stack of selector plates. There is one selector plate individual to each blade element and a 13th, spacing, plate. Each of the selector plates are of integral construction having a selecting section, the front edge of which is to be moved in a direction forcing the associated printing blade element forward for printing the corresponding line segment, and two guiding sections for insuring parallel movement of the selecting section. Each of the selecting sections of the selector plates has a multiple of substantially square apertures in registry with corresponding apertures in all of the other plates. Keys are extended through the apertures in all of the selector plates in registry. The keys in the plates have surfaces cooperating with edges of the apertures of the plates defining the forward direction of the plates of two different characteristics distributed in predetermined permutation for all of the keys. Depressing a key shifts the selector plates relative to one another in accordance with the distribution of the two different characteristics. The guiding sections of the plates are pivoted at central points so that the selecting sections move directly forward regardless of the location of the particular key which is actuating the plates. The leading edge of the selector plates for the particular character desired may bear directly against the ends of the blade elements remote from the printing ends, but preferably linking elements are interposed between the printing blade elements and the selector plates. These linking elements are particularly desirable when the direction of travel of the printing blade element is at an angle with respect to the direction of travel of the selector plates. Specifically, the square apertures of the plates which are to remain at rest for the selection of a given character are enlarged so that depressing the associated key will not move them forward. A camming element is arranged in the apertures between the actuating surface of the keys and the actuating surfaces of the selector plates to provide more uniform motion. The subassembly of printing blade elements and the subassembly of linking elements are arranged in a carrier which is stepped across the leading edge of the selector plates in response to actuation of the 13th or spacing selector plates. When the carrier has arrived at the end of the line, it is manually returned to the beginning of the travel and the record medium is advanced automatically one line in readiness for the next line of printing. Preferably, the printing blade element assembly, the escapement mechanism, and record-medium-advancing mechanism are designed so that different sized characters may be printed and spaced accordingly.

Description

This application is related to copending U.S. Pat. applications Ser. No. 829,652 filed June 2, 1969, of Reynold Benjamin Johnson, Edward Everett Long and George Edmund Price for a Key Responding Selector Mechanism thereafter allowed Dec. 4, 1970, and Ser. No. 829,642 filed on the same day, of Reynold Benjamin Johnson and Ralph Engene Marrs for a Mechanical Power Transmission System, thereafter allowed Dec. 30, 1970.

The invention relates to mechanical key responsive type printing apparatus, and it particularly pertains to such apparatus for printing constrained characters readily recognized on sight and by optical character recognition apparatus.

In the contemporary alphameric character printing art, attention is being directed to simplified, low cost, manually operated type printing apparatus for use in conjunction with data processing systems such as commercial billing systems, and the like, and Computer Assisted Instructional (CAI) systems. In the CAI systems, the use of character printing apparatus is particularly helpful as a learning aid in that young children may be developed mentally before they have acquired the manual art of clearly lettering and writing rapidly. The same apparatus is valuable as a teaching aid in that automatic grading and selection of predetermined course material may be made along predetermined lines, leaving the teacher free to assist the students in pedagogical ways.

Conventional wire printing apparatus, printing telegraph apparatus, and various forms of typewriting apparatus have been suggested for this purpose, either in their conventional form or modified to some extent as the particular application required. Examples of this prior art are to be found in the following U.S. Pat. Nos.: 2,851,141, 9/1958, to Kistner; 2,943,150, 6/1960, to Handley; 3,099,711, 7/1963, to Foley, et al.; 3,276,560, 10/1966, to Wirtz; 3,324,240, 6/1967, to Kleinschmidt, et al.; 3,324,985, 6/1967, to Palmer, et al.; 3,334,720, 8/1967, to Hickerson;

According to the invention, the objects indirectly referred to hereinbefore and those which will appear hereinafter are attained in a key responding multiple element printing apparatus similar in some respects to the conventional portable typewriter. While the printing apparatus according to the invention is even adaptable to dot matrix printing, the invention is based on short line segment printing with multiple printing blade elements oriented in groups for printing characters of a family of type in the general format of a parallelogram within a parallelogram. Conveniently, all of the alphameric characters necessary for a very large variety of work can be made up of not more than a dozen short straight line segments arranged two by two to make up a parallelogram and two intersecting medians thereof. Such characters are defined as constrained characters based on the format of a medianly quartered parallelogram (MQP) which embraces both slanted and upright printing the latter being a special case in the form of an orthogonally quartered rectangle (OQR) of the 26 letters of the English alphabet and the 10 Arabic numerals. Only a few letters vary greatly from the conventional and these are readily recognized upon seeing them in proper context. The printing blade elements are selected for movement out of rest position into printing position against a printing record medium supported by a platen. While an inked ribbon, stamp pad, or similar inking arrangement, is suggested, the invention preferably employs printing blade elements comprising several leaves between which liquid ink is carried to the record medium by capillary action. The printing blade elements are selected for movement between the rest and printing positions by means of a stack of selector plates, one for each printing blade element and a further selector plate for a spacing mechanism. The leading edge of the selector plates may bear directly on the ends of the printing blade element remote from the printing ends, but preferably a plurality of linking elements are interposed between the printing blade elements and the selector plates. This linking element subassembly is particularly desirable when the direction of movement of the printing blade element is at an angle with the direction of movement of the selector plates. The selector plates are moved relative to one another by means of keys arranged in apertures in registry in the stack of selector plates. The keys in the plates have cooperative surfaces at edges of the plates defining at least parts of the apertures of two different characteristics distributed in predetermined permutation, one for each aperture and key combination, enabling the shifting of said selector plates relative to one another in accordance with the distribution of the two different characteristics. In one suggested embodiment, the different characteristics are located in the keys and another of the different characteristics are in the apertures in the selector plates. In the latter embodiment, the forward edge of the selector plates which are to remain in the rest position are cut away so that depression of the key does not effect any movement of these plates. Preferably, a camming element is located in the aperture along with the key so that depression of the key will provide uniform movement of the selector plates to be moved. According to the invention, the printing blade elements are arranged as a subassembly of the printing apparatus and are readily removable and replaceable. It is contemplated that several different sizes of type may be printed by varying the sizes of the subassembly of printing blade elements. The printing blade elements and a subassembly of linking elements are mounted in a carrier which is arranged to advance across the leading edge of the selector plate. An escapement mechanism is arranged along ways in which the carrier moves, and in the case of different sizes of type, the escapement mechanism is adjustable for the different sized characters.

In order that the advantages of the invention may be readily attained in practice, a description of a preferred embodiment of the invention is given hereinafter, by way of example only, with reference to the accompanying drawing, forming a part of the specification and in which:

FIG. 1 illustrates one type family of two versions printed by the apparatus according to the invention;

FIG. 2 is an isometric view of a printing head according to the invention;

FIG. 3 is a view of a printing head carrier with a printing head in place;

FIG. 4 is an isometric view of a partial assembly of the printing apparatus according to the invention;

FIG. 5 is a cross-sectional elevation view of an embodiment of the printing apparatus according to the invention;

FIG. 6 is a plan view of one of the selector plates according to the invention illustrating the principle of operation;

FIG. 7 is an end view of a stack of selector plates according to the invention,

FIG. 8, sections (a) and (b) being taken together illustrate an alternate construction according to the invention.

FIG. 9 is a plan view of the carrier showing some escapement and printing head ident detail according to the invention.

FIG. 10 is a view of the type family size selector shaft, and

FIG. 11 is a view of the head ident according to the invention.

An example of a type family produced by the printing apparatus according to the invention is shown in FIG. 1. Two versions of the basic type family are indicated. The "slant" version is based on the medianly quartered parallelogram (MQP) 10. The "upright" version is based on the special case of a right parallelogram or orthogonally quartered rectangle (OQR) 20. Both versions are based generically on a parallelogram within a parallelogram format. The sentence given in the OQR version contains at least one example of each letter of the English alphabet; some special characters and the Arabic numerals are given below it. Note that the numerals are half the width but of the same height as the alphabetic characters. The usual variations in weight and size of a type series are possible in this type family.

The choice of slant and upright versions is usually made on considerations involving human factors; reading one version may be easier and lettering is usually easier in the "inclined" style corresponding to slant printing than in the "vertical" style which corresponds to the upright printing version. The design considerations of optical character recognition apparatus for recognizing this type family may also depend upon the particular version chosen.

FIG. 2 depicts a printing head 24 comprising 12 blades, 0, 1, 2, ...9, Y and Z assembled somewhat on the order of a wire printer but with the printing ends arranged in the desired MQP format in a barrel 26 (shown with a cover plate removed). While the use of the barrel 26 is not necessary to the invention, it is highly desirable in that slant and upright versions of the type family may be interchanged along with a series of different sizes and weights of the type family. It should be noted that the numbering of the blades corresponds to the 12-punch coding of the conventional Hollerith or Information Bearing Matrix (IBM) punched card. The direct relationship between the IBM card punching and the twelve segment type family format is a highly advantageous feature. Although it is contemplated that the blades 0--Z may print by impression against a ribbon similar to that used in the conventional typewriter, preferably liquid ink admitted to the barrel 26 from a reservoir 28 is fed to the ends of the blades. Preferably, each blade is made up of a number of leaves, seven being found particularly suitable, between which the ink flows due to capillary action. Best results are obtained when the leaves are "feathered," that is of increasingly different lengths. The blades are arranged to be pushed forward in the barrel 26 by pressure on the tangs 30--3Z. Feathered blades bow a bit making for better ink flow and self cleaning action. The barrel 26 is fitted with lugs 44 of standardized dimensions for interchangeability so that the head 24 is readily mounted into and demounted from a carrier 45 shown in FIG. 3 and elsewhere. The blades themselves and the barrel containing them may extend the length of the carrier 45, but preferably they are shorter as shown and extended in effect by individual linking elements 47 arranged in sleeve blocks 50 and 52 on the carrier 45. This construction renders the head 24 more readily demountable from the carrier 45 and permits the linking elements to exert pressure "around the corner" of an arrangement as shown in FIGS. 4 and 5 wherein the axis of the printing head 24 is at an angle with the axis of the sleeve block 52 containing the ends of the linking elements 47 to which actuating pressure is applied.

FIG. 4 shows a spacing selector plate 58 which is the lowermost plate of a number of a stack of selector plates by which the printing blade elements O--Z are selected and actuated. The selector plates are actuated by keys 70 only a few of which are shown in FIG. 4. As will be explained hereinafter, depression of a key 70 effectively urges the leading edge of the spacing selector plate 58 forward for actuation of an escapement mechanism on the carrier 45 permitting it to escape one intercharacter spacing equal to the character width plus an intercharacter space along a rack 74 in addition (except for a blank space) to actuating one or more of 12 other similar plates for actuating the corresponding printing blade elements of the printing head 24.

Referring to FIGS. 4--7, the operation and construction of the selector plates is seen. For the printing head hereinbefore described, one spacing plate 58 and 12 blade selector plates 60-6Z are stacked together. For clarity only five plates are shown in FIGS. 5 and 7. Each displaceable plate 60, for example, in FIG. 6, comprises a moveable selecting section 81, two guiding sections 82 and 83 joined together by a flexible bar section 84 and joined at the other ends to the selecting section 81 by two further flexible bar sections 85 and 86. Four pins 90 are mounted in line across the frame of the machine, as shown in FIG. 4, and the plates are arranged on the frame with the pins 90 protruding through apertures 91, 92 and 93. The pins 90 and apertures 91--93 are of dimensions permitting the guiding sections 82 and 83 to pivot about the pins in apertures 92 and 93 and to so pivot without restraint with respect to the pins in the larger apertures 91. The plates are made of relatively thin material of such resilience that the flexible bar sections restrain the leading edge 94 in the forward movement to a line absolutely parallel to the line defined by the pins 90 despite any tendency to cant due to offcenter pressure from a key depression. Many materials are suitable for the plates. For example, one embodiment used cotton base phenolic 1/32 inch thick and others used tempered aluminum of thicknesses of 0.012 and 0.015 inch. These plates were produced by punching. Molded plates of suitable materials such as "Mylar" of approximately 0.013 inch thickness are contemplated. Less expensive plates may be made of steel of 0.007 inch stock. These plates afford long life in that the flexible bar sections are less prone to fatigue but are inherently heavy and thus, there is high inertia to be overcome in moving the steel plates. In the interests of clarity, only five selector plates are shown in FIGS. 5 and 7, but it should be understood that any practical number of plates may be used according to the invention. In embodiments of the invention, the selector plates have been arranged to move distances of 0.125 inches to 0.050 inches although less and greater distances can be accommodated depending upon the circumstances.

In embodiments where the plates are stacked one upon another as shown in FIG. 5, two distinctly different though similar plates are used. The difference lies in staggering the location of the flexible bar sections 84, 85 and 86 as better shown in the end view of a stack of five plates in FIG. 7. This staggering eliminates any possibility of the edges of the flexible bar sections and edges of the plates from snagging on each other especially with respect to the crosswise component of motion undergone in the flexing of these portions of the plates.

Where a large number of plates are stacked one atop the other, there is a ceiling to the frictional loading at which the selection of one or two plates near the bottom may carry another unselected plate along. FIG. 8 shows a structure eliminating this possibility. Again, only four selector plates 58, 60, 61 and 62 are shown for simplicity, but it should be understood that the arrangement is more and more advantageous as the number of plates is increased. Each plate is supported by a multiple of rockers arranged for limited movement in apertures in a base spring plate 55 fixed in the frame 54 and resting on a rocker support 57. Three or four rockers for each plate will be found satisfactory, though only one rocker for a plate is shown in the interest of simplicity. For example, the spacing selector plate 58 is supported by three or more rockers 58R. The plates 58, 60 and 61 have apertures permitting the rockers 60R, 61R to pass through for supporting the plate above. Friction between rockers is reduced by means of bosses 59 located at suitable points.

The keys 70 move the selector plates by pressure on the forward edges of the apertures 96 in which the keys are arranged. Those plates which are not to be moved have the apertures enlarged at least in the forward direction so that the plate is undisturbed by movement of the key 70 in the larger aperture. The leading edge 88 of selector plates according to the invention also can be moved forward by corresponding movement of the guiding sections 82 and 83. An aperture 98 similar to the key apertures 96 is located in the longer guiding section 82 on the centerline of the selector plate 60. Conveniently, the stem of a space bar which is similar in construction to the stems of the keys 70, is arranged in the apertures 98 of all of the plates in the stack. The apertures 98 in the selector plates 60-6Z are made sufficiently large and of such configuration that none of the selector plates 60-6Z are disturbed by depression of the space bar. The aperture 98 in the spacing selector plate 58 is arranged to cam the guiding section 82 rearward in pivotal motion about the pin 90 in the aperture 92. The edge of the aperture 98 in the spacing plate 58 remote from the leading edge 88 is parallel to the leading edge 88 when the guiding section 82 is in its rearmost position. The other edges of the aperture 98 in the spacing selector plate 58 are relieved so that the space bar stem does not bind as the guiding section 82 pivots. The apertures 96 and 98 may be circular for those plates to be moved by the depression of a key having cylindrical form and elongated into oval shape or those plates not to be moved by the particular key arranged therein. Preferably, the apertures 96 and 98 are substantially rectangular in form as shown permitting the use of a pressure-equalizing cam member 112 in conjunction with each of the keys 70 and with the space bar key stem 110 as shown in FIG. 5. Each cam member 112 has a tip 114, a pressure-exerting cam surface 116 and a key return cam surface 118. The tip 114 of each cam member 112 is arranged loosely in a bore in a keyboard bottom plate 120 so that the cam member 112 pivots about the shoulder forming the tip 114. The space bar stem 110 and each key 70 is of rectangular configuration and has a shallow bore at the lower end in which a key return compression spring 122 is located. The other end of the key return spring 122 is arranged in a bore in the bottom plate 120. In the absence of any pressure on the key 70 or the space bar 100, the latter are urged to the uppermost position due to the return spring 122. Each key 70, and the space bar stem 110 as well, has a rectangular slot in through the intermediate portion thereof in which a pair of rollers 127 and 128 are arranged. The combined diameters of the rollers 127, 128 is equal to the distance between a key backplate surface member 130 and the cam member 112 when cammed into the position for urging the selector plates forward. The rollers are loosely held in the key stem slot by means of a V-shaped resilient spring member having the ends bent at right angles and riding in central bores of the key rollers 127 and 128. When the key 70 is depressed, both rollers 127, 128 ride at the top of the slot 124 and force the cam member 112 forward as shown. At the end of the forward stroke, the rollers 127 and 128 continue past the peak of the cam surfaces 116 and 118 allowing the cam member 112 to fall back. The pressure of the return spring 122 then is permitted to force the key 70 upward. In so doing, the forward key roller 128 is held back by the key return cam surface 118 and thus revolves about the other roller 127 within the key so that the cam member 112 is not again urged forward to cause the same selected character to be repeated.

In an embodiment of the printing apparatus according to the invention for printing characters of a single size, the spacing selector plate 58 need only actuate a conventional dual pawl and rack machine escapement mechanism. A carrier return lever 134 and conventional mechanism serves to release the escapement and return the carrier to the left side of the machine at the end of a given line. Conventional line feed means are also contemplated for use in embodiments of the printing apparatus. For example, a web record medium and conventional typewriter line feed mechanism is contemplated. For apparatus according to the invention which is designed for the utmost in portability, a record media mounting 136 is arranged adjacent a bar platen 135 with one or more series of steps 138 for manually advancing an IBM card record 140. Alternately, a simple pawl and ratchet mechanism of conventional form may be used to swing a card feed arm 142 attached to a pulley 144 in an arc substantially following the outline of the steps 138. A card feed drive cord 146 is connected to the carrier return mechanism by conventional means for stepping the card feed arm 142 each time the carrier is returned to the left side of the machine.

A series of type families of different size are contemplated with the printing apparatus according to the invention. For example, three type families have been found particularly useful in practice. The largest size (termed 3-pitch) measures 31/3 characters per inch. Each 3-pitch character is 0.18 inches wide and 0.25 inches high, which dimensions are suitable for automatic machine reading as well as machine printing. Five characters per inch (5-pitch), where the width of each character is 0.125 inches and the height is 0.170 inches, is a convenient size for machine printing and machine reading. A smaller size (termed 10 -pitch) with each character 0.08 inches wide and 0.10 inches high, is suitably condensed to afford a great deal of information per document although the machine for reading this small character is much more expensive due to the tighter tolerances necessary in construction.

In order to accommodate different sizes of type families, an adjustable escapement, an adjustable line feed and a printing head ident are provided. For example, in order to accommodate the three sizes of type families described above, a selector lever 148 is moved to rotate a selector mechanism shaft 150 on which three sets of cams are arranged. As seen in FIGS. 9 and 10, the selector mechanism shaft 150 is journaled in the carrier 45 and in an upper cover plate 152 of an escapement selector assembly. A portion of the selector mechanism shaft 150 above the carrier 45 and below the upper cover plate 152 has three notches 154, 155 and 156 corresponding to the three different positions of the selector lever 148. These notches, in effect, constitute one of the three character size selecting cams mentioned above. An escapement baseplate 158 is slideably mounted on the carrier 45. A pawl spring member 160, fastened to the baseplate 158 to move with it, is trifurcated to provide a 3-pitch escapement spring pawl 163, a 5-pitch escapement spring pawl spring 165 and a 10-pitch escapement spring pawl 170. Only one of the escapement spring pawls will fall into the allocated notch depending on the position of the size selector lever 148. The particular pawl spring resting in its allocated notch serves both as a detent for the selector mechanism shaft 150 and as the pawl for an allocated escapement ratchet 173, 175 or 180. The three escapement ratchets are mounted on an escapement ratchet shaft 182 journaled in the carrier 45 and the upper cover plate 152. An escapement pinion gear 184 is arranged on the lower end of the escapement ratchet shaft 182 to engage the rack 74. The pawl spring member 160 has a pawl spring tang 162 which is operative with the 10-pitch escapement ratchet 180 for all of the sizes of character selected. An upright escapement pawl spring lifting bar is also attached to the escapement baseplate 158 in such a position as to bear against the selected escapement pawl spring. A baseplate bias spring 168 urges the baseplate 158 against the spacing selector 58. In operation, each time a key or the space bar is depressed the spacing selector plate 58 moves forward carrying the pawl spring member 160 and the escapement pawl spring lifting bar 186 forward. In so moving, the selected pawl spring 170 as shown as being selected from engagement with its associated escapement ratchet 173, and moving the pawl spring tang 162 into position for engagement with the 10-pitch escapement ratchet 180 which is (hidden) below the 3-pitch escapement ratchet 173. This releases the hold on the escapement and the carrier 45 is urged to the right by suitable means, such as a conventional spring-loaded cord and pulley assembly. As the depressed key 70 passes over the cam member 112, the spacing selector plate 58 is released and falls back along with the escapement baseplate 158 in response to urging by the baseplate bias spring 168. The selected escapement pawl spring 170 returns to the operative position to stop rotation of the escapement ratchet 173 when the next tooth arrives after a rotation of the escapement ratchet 173 corresponding to the width of one character plus one intercharacter space. The positioning of the selector mechanism shaft 150 also positions a bail selector cam 188 against which a line feed selector bail 190 is urged by suitable means such as by a spring 192 shown in FIG. 3. The position of the line feed selector bail 190 is imparted by means of a line feed selector rod 194 to a conventional mechanism (not shown) for adjusting the line feed of the record medium in response to carrier return in a manner well known to the art and therefore not described in detail. A further cam 196 is carried on the selector mechanism gap 150 for translating a cam follower 198 as seen in FIG. 11. This cam follower 198 carries a printing head ident 200. A compression spring 202 urges the cam follower 198 into contact with the head ident positioning cam 196. The head ident 200 is positionable in one of three positions above the carrier 45 so that only the printing head 24 having a barrel 26 which is correspondingly notched as shown in FIG. 3 can properly be mounted in place on the carrier 45 in operative position with respect to the linking elements 47. The printing heads for both the slant and the upright versions of the same size type family will have the ident slot located in the same position. Thus, while the size of the type is automatically accommodated as desired; it is still possible to vary the versions in the printed text for conveying emphasis and the like.

It is contemplated that the selector plates be arranged for opening and/or closing electric circuit contacts in predetermined permutation for simultaneously controlling other devices and/or transmitting coded data to a computer, or the like. As shown in FIG. 5, a plurality of pivoted switch bars 230 (only the end one of which appears) have the upper ends disposed in apertures in the plates 58 and 60-6Z for forward movement in accordance with the distribution of aperture sizes in the plates in much the same manner as for the keys 70. Conventional electric circuit switch contact assemblies 232 and 234 are opened and closed by the movement of the bars 230 carrying an associated switch lever cam 236.

While the invention has been shown and described particularly with reference to a preferred embodiment thereof, and various alternative structures have been suggested, it should be clearly understood that those skilled in the art may effect further changes without departing from the spirit and scope of the invention.

Claims

The invention we claim is:

1. Printing apparatus comprising:

a frame including ways,

a carrier arranged to move on said ways and components urging said carrier in one direction in said ways,

a printing head removably arranged in said carrier and comprising

a multiple of printing elements in the form of short line segment printing blade elements oriented and grouped for printing characters of a predetermined family of type, each element having rest and printing positions

a stack of selector plates and an escapement plate having a multiple of apertures in registry therein,

keys arranged in said apertures in registry in said selector plates,

said keys and edges of said plates defining at least parts of said apertures having cooperating surface configurations of two different characteristics distributed in predetermined permutation, one for each aperture and key combination, enabling the shifting of said selector plates relative to one another in accordance with the distribution of said two different characteristics,

said printing elements and said selector plates being arranged for selectively shifting said printing elements in accordance with the shifting of said plates in response to the actuation of one of said keys,

an escapement reference element arranged along said ways

an escapement mechanism arranged in said carrier and having an escapement drive element engaging said escapement reference element,

said escapement mechanism comprising

a plurality of escapement ratchets fixed to said escapement drive element,

a plurality of escapement pawls arranged for potentially engaging said escapement ratchets,

an escapement selecting lever arranged to move said escapement pawls selectively into engagement with said escapement ratchets,

an escapement indicating element connected to said lever, and

an ident element on said print head mating with said escapement indicating element for preventing the mounting of a print head in said carrier except for the escapement chosen in accordance with the indicating element selected by operation of said lever,

said spacing plate being arranged for shifting said escapement pawls to stop the movement of said carrier in said one direction on completion of the shifting of said printing elements,

thereby printing the character corresponding to said one key and escaping the carrier a spacing equal to that of one character.

2. Printing apparatus as defined in claim 1 and incorporating

a member associated with each key in said apertures for insuring the exertion of uniform pressure simultaneously on the plates to be shifted,

said member and the associated key sharing two camming surfaces and a cam follower arranged to force said member against the selected plates on the operating stroke of said key and to cam the follower away from the plates on the return stroke.

3. Printing apparatus as defined in claim 1 and incorporating

a bail arranged in said frame along said ways and connected to a line feed device for controlling the spacing between lines,

a cam on said selector lever and engaging said bail for determining the line feed in accordance with the print head acceptable by operation of said lever.

4. Printing apparatus as defined in claim 1 and wherein

said selector plates have additional apertures therein similar in configuration to said apertures in which said keys are arranged, and

electric switch arm members arranged in said additional apertures for opening and closing electric switch contacts in accordance with the shifting of said selector plates.

5. Printing apparatus as defined in claim 1 and incorporating

a card-feeding device comprising

a step-shaped member having steps substantially equal to the desired line spacing, and

an arm coupled to line mechanism and arranged for passing said step-shaped member in engagement with a card being fed.

6. Printing apparatus as defined in claim 5 and wherein

said arm is pivoted at one end thereof about an axis parallel to the steps of said step-shaped member and,

the steps of said step-shaped member lie in a cylindrical surface of revolution about said axis.