Title:
TYPE HEAD ARRANGEMENT
United States Patent 3559791


Abstract:
A rotary and axially shiftable type head is composed of a stack of type discs provided with circumferential rows of type faces. A selected type disc having a type face corresponding to a selected character is shifted to an advanced position, while the type discs adjacent thereto are held in a retracted position. When the entire type head is moved toward the platen to a printing position, the type faces of the retracted type discs are at a safe distance from the printing area of the platen so that the rows of type faces can be more closely spaced than in the prior art.



Inventors:
WALDENBURGER HERMANN
Application Number:
04/746212
Publication Date:
02/02/1971
Filing Date:
07/19/1968
Assignee:
TRIUMPH WERKE NUERNBERG AG
Primary Class:
Other Classes:
101/110, 178/34, 178/40, 400/163, 400/163.1, 400/168, 400/170, 400/175, 400/258
International Classes:
B41J1/54; B41J7/52; H04L17/24; (IPC1-7): B41J1/32
Field of Search:
101/110 197
View Patent Images:
US Patent References:
3343642Typing apparatus having plural type wheels which selectively strike platenSeptember 1967Weidanz et al.
3221863Printing arrangement for business machineDecember 1965Pietzsch
3169474Type cylinderFebruary 1965Howard
3027988Printing deviceApril 1962Tackett
2311737Silent typewriting machineFebruary 1934Colombo



Primary Examiner:
Burr, Edgar S.
Claims:
I claim

1. Type head arrangement comprising, in combination, a platen having a line-shaped printing area; rotary type head means having an axis of rotation spaced from, and crossing said line-shaped printing area at right angles and including a plurality of adjoining axially stacked type discs forming a type head and having circumferential rows of type faces, first mounting means for mounting each type disc for movement toward and away from said printing area independently of the other type discs between a first position fully retracted from said printing area, and a second position advanced toward said printing area but spaced from the same, and a support supporting said first mounting means and thereby said type head; second mounting means mounting said support for rotation about said axis and for axial movement so that a selected type face can be placed opposite said printing area, and also mounting said support for movement with said type head in a printing motion toward and away from said platen; and control means operable for placing a selected type disc having said selected type face in said second advanced position and any type disc adjoining the selected type disc in said first retracted position during the placement of said selected type face opposite said printing area so that when said support is moved in said printing motion toward said platen with said selected type disc in said second advanced position, said selected type face impresses said printing area while the type faces of said adjoining type discs in said first retracted position are spaced from areas of said platen adjacent said printing area.

2. Type head arrangement as claimed in claim 1 wherein said type discs have central openings; and wherein said control means is movable in said central openings for placing at least said selected type disc in said second advanced position, and said adjacent type discs in said first retracted position.

3. Type head arrangement as claimed in claim 1 wherein said control means include integral journal means supporting alternate type discs of said stacked type discs for rotation about two parallel axes.

4. Type head arrangement as claimed in claim 1 wherein said control means include a first journal portion for supporting said selected type disc for rotation about a first axis coinciding with said axis, and a second journal portion for supporting a type disc adjacent said selected type disc for rotation about a second parallel axis.

5. Type head arrangement as claimed in claim 1 wherein said type discs have overlapping eccentric openings and central bearing openings; wherein said first mounting means include end members at the ends of said stacked type discs, connecting bolt means pressing through said eccentric openings and being secured to said end members, and pivot pin means secured to said end members and mounting said type discs for movement between said first and second positions in which said connecting bolt means abut the edges of said eccentric openings; and wherein said control means include a control member having a plurality of journal portions respectively located in said bearing openings, alternate journal portions being offset to each other and supporting the respective type discs for rotation about two parallel axes, one of said axes coinciding with said axis of rotation of said support, and a control rod connected with said control member and being operable for shifting said control member between two positions in which each journal portion is located in the bearing openings of alternate type discs; and wherein said support is a rotary tubular member in which said control rod is located, said tubular member being secured to one of said end members.

6. Type head arrangement as claimed in claim 1 wherein said platen is a stationary cylinder having an axis, and wherein said axis of rotation of said type head is perpendicular to the axis of said platen.

7. Type head arrangement comprising, in combination, a platen having a line-shaped printing area; rotary type head means having an axis of rotation and including a plurality of axially stacked type discs forming a type head and having circumferential rows of type faces, said type discs having overlapping openings, first mounting means for mounting each type disc for movement transverse to said axis independently of the other type discs between a first position retracted from said platen and a second position advanced toward said platen, said first mounting means including end members at the ends of said stacked type discs, connecting means passing through said openings and being secured to said end members, and pivot means secured to at least one of said end members and mounting said type discs for movement between said first retracted and second advanced positions in which said connecting means abut the edges of said openings, and a support supporting said mounting means and thereby said type head; second mounting means mounting said support for rotation about said axis, for axial movement, and for displacement toward and away from said platen together with said stacked type discs so that a selected type face of a selected type disc can be first placed opposite said printing area and then moved toward the same in a printing motion; and control means operable for placing the selected type disc in said second advanced position, and any type disc adjacent said selected type disc in said first retracted position so that the type faces of said adjacent type discs are spaced from areas of said platen adjacent said printing area when said selected type face impresses said printing area.

8. Type head arrangement as claimed in claim 7 wherein each type disc is formed with a radial slot; and wherein said pivot means in a pivot pin passing through said slots so that said type discs move in a translatory movement in a plane perpendicular to said printing area in a first angular position of said type head means, and move in a pivotal angular movement in a second angular position of said type head means spaced 90° from said first angular position.

9. Type head arrangement comprising, in combination, a platen having a printing area; rotary type head means having an axis of rotation and including a plurality of axially stacked type discs forming a type head and having circumferential rows of type faces, said type discs having central bearing openings, first mounting means for mounting each type disc for movement transverse to said axis independently of the other type discs between a first position retracted from said platen and a second position advanced toward said platen, and a support supporting said mounting means and thereby said type head; second mounting means mounting said support for rotation about said axis, for axial movement, and for displacement toward and away from said platen together with said stacked type discs so that a selected type face of a selected type disc can be first placed opposite said printing area and then moved toward the same in a printing motion; and control means operable for placing the selected type disc in said second advanced position, and any type disc adjacent said selected type disc in said first retracted position so that the type faces of said adjacent type discs are spaced from areas of said platen adjacent said printing area when said selected type face impresses said printing area, said control means including a control member having a plurality of journal portions respectively located in said bearing openings, alternate journal portions being offset to each other spaced different distances from said printing area and supporting the respective type discs for rotation about two parallel axes, one of said axes coinciding with said axis of rotation of said support, and operating means for shifting said control member in axial direction a distance corresponding to the axial spacing of said type discs.

10. Type head arrangement as claimed in claim 9 wherein said operating means include electromagnetic operating means including first core means connected with said control member, coil means acting on said first core means, and key switch means for causing energization of said coil means; and comprising second core means moved by said coil means and connected with said support for moving said type head in axial direction between a plurality of positions in which different type discs are located opposite said printing area.

11. Type head arrangement as claimed in claim 10 wherein said control means include a control rod connecting said control member with said first core means; wherein said support is tubular and partly surrounds said control rod; wherein said coil means include a plurality of stacked coils; and wherein said key switch means cause energization of pairs of rod coils.

12. Type head arrangement as claimed in claim 9 wherein said control member includes cylindrical guide faces located between said journal portions and being slated to the same.

13. Type head arrangement as claimed in claim 9 wherein each type disc includes a bearing ring bounding said central bearing opening, the axial thickness of each bearing ring being less than the axial thickness of each type disc; wherein said bearing rings are made of metal; and wherein said type discs are made of a plastic material.

14. Type head arrangement as claimed in claim 9 wherein said type head means comprise rolling bearing elements located between said bearing openings and said journal portions.

15. Type head arrangement as claimed in claim 14 wherein said support is a tubular member having a tubular portion with openings confining said rolling bearing elements and located in said bearing openings.

16. Type head arrangement as claimed in claim 9 wherein said support is a tubular member secured to said first mounting means for rotation therewith; and wherein said control means include a control rod connected with said control member and operable for shifting said control member between axially displaced positions in which each journal portion is located in the bearing openings of alternate type discs.

Description:
BACKGROUND OF THE INVENTION

Type head arrangements are known in which a cylindrical or barrel-shaped type head is provided with a plurality of circumferential rows of type faces arranged in axial columns. Either the carriage with the platen, or the type head is moved in writing direction. The selection of a type face is accomplished by stopping the rotating type head when the column of the selected type face is located opposite the printing area of the platen, whereupon the type head is moved in axial direction to place the selected type face opposite the printing area. The type head is then moved toward the platen so that the selected type face produces an imprint.

The type heads of the prior art are either integral, or constructed of rigidly connected rings. It is necessary to shift the type head a substantial distance in axial direction since the rows of type faces must be spaced in axial direction a distance which assures that only the selected type face has printing contact with a sheet on the platen, while the type faces located directly above or below the selected type faces must not touch the paper sheet. For a platen having a given diameter, a minimum length of the type head results by adding the required minimum distances between the circumferential rows of type faces, and also the distances which the type head has to be raised or lowered for selection of a circular row of type faces.

It is not possible to reduce the diameter of the platen below a standard measure which would improve the conditions, since thick sheet material inserted into a typewriter would crack or break when flexed about a very small platen.

SUMMARY OF THE INVENTION

It is one object of the invention to overcome this disadvantage of known type heads, and to provide a type head arrangement permitting the use of a very small type head, while nevertheless type faces adjacent to the selected type face do not produce undesired imprints.

Another object of the invention is to reduce the size of the type head so that the mass which has to be accelerated during a printing operation is small.

Another object of the invention is to provide a type head arrangement in which the type head can be moved a small distance from an inoperative to a printing position.

Another object of the invention is to reduce the size of a type head as compared with type heads of the prior art, without reducing the diameter of the platen.

With these objects in view, the present invention provides a type head constructed of a plurality of stacked type discs which are rotatable and shiftable relative to each other so that the type disc carrying a selected type face can be placed in a position advanced toward the platen, while type discs adjacent to the selected type disc are held in a retracted position. In order to accomplish the selection of a type face as fast as possible, it is advantageous that the relative shifting of the type discs takes place at the same time as the shifting of the type head for selection of a specific circular row of type faces.

The type head arrangement of the present invention may move parallel to a stationary platen, or be stationary and cooperate with a platen movable with the paper carriage in the writing and return directions.

One embodiment of the invention comprises type head means including a plurality of axially stacked type discs forming a type head, each type disc having a circumferential row of type faces, first mounting means for mounting each type disc for movement transverse to the axis independently of the other type discs between a first position retracted from the platen and a second position advanced toward the same, and a support supporting the mounting means and thereby the type head;

second mounting means mounting said support for rotation about an axis, for axial movement, and for displacement toward and away from the platen together with the type head so that a selected type face of a selected type disc can be first placed opposite the printing area and then moved toward the same in a printing motion; and

control means operable for placing the selected type disc in the advanced position, and any type disc adjacent the selected type disc in the retracted position.

Due to the fact that the selected type face is closer to the printing area than adjacent type faces of the adjacent type discs when the printing movement starts, no imprints can be produced by the type faces of the adjacent nonselected type discs when the selected type face engages the printing area, even if the type discs are very thin and the adjacent circular rows of type faces are much closer spaced than in constructions according to the prior art.

In the preferred embodiment of the invention, the control means include a control member located in central bearing openings of the type discs. The control member has offset alternate journal portions about which alternate type discs rotate. By shifting the control member in axial direction, a shifting of groups of alternate type discs between the retracted and advanced positions is accomplished while the entire type head is moved in axial direction to a position in which the selected type disc is located opposite the printing area. The arrangement is such that the selected type disc is also placed by the respective journal portion of the control means in the advanced position.

In the preferred embodiment of the invention electromagnetic means are used for simultaneously shifting the control member and the support of the type head in axial direction under the control of typewriter keys.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary perspective side view illustrating an embodiment of the invention;

FIG. 2 is a fragmentary plan view and horizontal section of the type head in a first operational position;

FIG. 3 is a plan view and horizontal section corresponding to FIG. 2 and illustrating another operational position of the type head;

FIGS. 4, 5 and 6 are fragmentary sectional views illustrating three different operational positions of the type head;

FIG. 7 is a fragmentary sectional view illustrating a fourth operational position of a modified exchangeable type head;

FIG. 8 is a vertical section taken on line VIII-VIII in FIG. 2, and illustrating the type head arrangement, and electromagnetic operating means for the same, in the operational printing position of FIG. 4;

FIG. 9 is a schematic, partially sectional view illustrating a position of the printing head spaced from the platen during selection of a type face;

FIG. 10 is a fragmentary side elevation illustrating a detail of the embodiment of FIG. 8;

FIGS. 11, 12, 13 and 14 are vertical sectional views illustrating the type head in the positions of FIGS. 4, 5, 6 and 7, respectively, together with electromagnetic operating means for shifting the type head and control means according to the invention relative to each other in axial direction; and

FIG. 15 is a fragmentary schematic perspective view illustrating key controlled apparatus for setting the type head to the printing of a selected type face.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing, a type head 1 is composed of four type discs 15, 16, 17 and 18, each of which is provided with a circumferential row of type faces 100, partly or completely omitted in FIGS. 1, 2 and 3 for the sake of simplicity. The type faces of all four type discs together represent a system of characters, digits and symbols, as is conventional in typewriters. Mounting means are provided for the four type discs and include two end members 22 and 23 which are mounted on an upper tubular portion 2a of a tubular support 2. FIGS. 2 and 3 show the type head with the upper end plate omitted. Each type disc has eccentric openings 29 and 30, and a radial slot 25. A pivot pin 26 passes through slots 25 of the stacked type discs 15 to 18, and bolts 27 pass through the eccentric large openings 29 and 30, as also shown in the section of FIG. 8. FIG. 2 shows type disc 16 in an advanced position as compared with the retracted position uppermost type disc 15, and the necessary angular displacement takes place about pivot 26.

FIG. 3 shows type disc 15 in the advanced position, and type disc 16 in the retracted position due to a translatory displacement of the upper most type disc 15 on pivot pin 26 permitted by the radial slot 25.

The position of FIG. 2 corresponds to the position of FIG. 5, and the position of FIG. 3 corresponds to the position of FIG. 4. Corresponding advanced and retracted positions can be assumed by type discs 16 and 17, as shown in FIGS. 6, 7 and 11--14. While alternate type discs are set to the advanced and retracted positions, respectively, the type head is in the position shown in FIG. 9 in which the type faces are spaced from the printing area of platen 24, and when the selection of a type face has been completed, the type head is moved to the printing positions shown in FIGS. 2--8 and 11--14 in which one type face of a type disc in the advanced position abuts a portion of a line-shaped printing area of platen 24 parallel to the axis of platen 24.

Referring now to the schematic FIG. 1, a tubular support 2 passes through a bearing bore in a tiltable frame 9 which is mounted on a carriage 11 which can be moved in the conventional manner along a platen 24 so that the type head 1 moves along the platen to successive printing areas. In order to select a particular type face from the rows of type faces on the type discs, an operating member 14 which has a rack portion 14a is moved in longitudinal direction so that a gear 3 on support tube 2 is rotated with support tube 2 which is secured to the end members 22 and 23 of the type head so that the type head 1 is rotated. The selection of a particularly angular position of the type head corresponding to a selected type face, is not an object of the present invention.

The tubular support 2 has a flange 4 against which a ring 6 is pressed by an attaching ring 5. Ring 6 has two projecting journals 7 which form a joint A with a pair of operating members 58, as shown in FIGS. 8 and 10. However, members 58 are shown in FIG. 8 in a position turned 90° for the sake of clarity and the correct position of operating member 58 is shown in FIG. 10.

Another operating member 13 shown in FIG. 1 which engages a cutout 12 in frame 9 in which the tubular support 2, 2a is mounted for rotary and axial movement. Operating member 13 holds frame 9 and type head 1 normally in the position shown in FIG. 9, but when electromagnet is energized, frame 9 is tilted by its armature 13 about pivot 10 to the printing position of FIG. 8. During the rotation of the type head for the selection of a type face, rack portion 14a only loosely engages gear 3 on tubular support 2, but when the type head is shifted to the printing position of FIG. 8, the gear teeth engage each other fully so that the circumferential position of the selected type face is accurately determined. However, the loose connection between rack portion 14a and gear 3 during the selecting rotation and axial shifting of type head 1 is sufficient for rotating the type head and for stopping the type head in a selected angular position in which the selected type face is located opposite the printing area of the platen.

Each type disc 15 to 18 has an insert in the form of a bearing ring 19 which forms a central bearing opening. Balls 20, or other roller bearing elements, are held in cutouts of the tubular sleeve 2a of tubular support 2 and are engaged by bearing rings 19. A control member 8a is located within tubular sleeve 2a and secured to a control rod portion 8 passing through the tubular support 2. Journals 59 project in opposite directions from the lower end of control rod portion 8, and form a joint with the fork-shaped end 81 of a second control rod portion 80. The joint of the control rod 8, 80 is designated B in FIG. 10, from which it is apparent that the type head together with support tube 2 and control rod portion 8 can be tilted from the inoperative position in which a type face is in the position D to the printing position C. The provision of two joints A and B permits the tilting to the printing position in axial displaced positions of tubular support 2 and control rod 8 since points A, B, C are located on a straight line in the printing position.

Control member 8a has offset and staggered journal portions 21 which are connected by slanted cylindrical guide portions 21a. The journal portions 21, which have circular cylindrical faces, are engaged by balls 20 so that type discs 15 to 18 are mounted for rotation. As explained above, tubular support 2 is rotated about an axis together with end members 22 and 23, and every alternate journal portion has an axis 121 coinciding with the axis 108 of control rod 8 and tubular support 2, while the other set of alternate journal portions 21e has an axis 121e which is radially spaced a distance e from axis 121, as shown in FIG. 4. Axes 121 and 121e are located in a plane perpendicular to the printing area and to the axis of platen 24.

When control rod 8 is shifted in axial direction a distance corresponding to the thickness of each type disc 15, the positions of alternate journal portions 21, 21e relative to the type discs is changed. For example, in the position of FIG. 4, type discs 15 and 17 are in advanced positions corresponding to the respective journal portions 21, as also shown in FIG. 3, while type discs 16 and 18 are in retracted positions due to the eccentric position of journal portions 21e. In the position of FIG. 5, the type head has been raised by the tubular support 2 so that type disc 16 is in the operative position at the level of the printing area and is held by the respective journal portion 21 in the advanced position, together with the type disc 18.

In the position of FIG. 6, not only the type head, but also control rod 8 with control member 8a have been raised so that type disc 17 is located at the level of the printing area of the platen, and is placed in the advanced position by journal portion 21, together with type disc 15, while type disc 16 and 18 are in the retracted position since they cooperate with journal portions 21e. In the position of FIG. 7, the lowest type disc 18 is operative and advanced together with type disc 16, while type discs 15 and 17 are retracted by journal portions 21e.

FIG. 7 illustrates a modified type head construction in which the type head is detachable for exchange with another type head carrying type faces according to a different font. The tubular support includes a flange 31 screwed onto a tubular member 32. Control rod 33 has a control pin 33a projecting therefrom through a bore in control member 34 which is secured to the pin by holding means 35. When holding means 35 is removed and the flange 31 unscrewed from tubular member 32, the entire type head with control member 34 can be detached and exchanged.

Due to the fact that each selected type disc is advanced by engaging a journal portion 21, and rotates about the axis 121, which is also the axis of the tubular support 2 and of the control rod 8, every selected type disc is in the same relative position to the printing area of the platen, and only type discs in the retracted inoperative position rotate about the eccentric axis 121e. Pivot pin 26 rotates about the axis 121 since it is part of the mounting means for the type disc carried by tubular support 2 or 32. The connecting bolts 27 serve only the purpose of holding the end members 22 and 23 of the mounting means together, and openings 29, 30 are sufficiently large to permit the relative displacement of adjacent type discs. Electromagnetic operating means 50 are provided for shifting control means 80, 8, 8a in axial direction between two positions, and also for shifting tubular support 2 and the type head between four positions in which the type discs 15, 16, 17 and 18 are respectively located at the level of the printing area of platen 24, as shown in FIGS. 4--7 and FIGS. 11--14. A set of four magnetic coils 51, 52, 53, 54 is mounted in a housing 50a and forms a central chamber in which three core members 55, 56 and 57 are located. Core member 56 is fixedly connected to the operating members 58, while core members 55 and 57 are fixedly secured to the control rod portion 80. Operating members 58 are shown in FIG. 8 turned 90°, and actually journal pins 7 and 59 are located in the same plane, as shown in FIG. 10. From FIG. 8 it can be seen that operating members 58 pass through corresponding bores in core member 57, while control rod portion 80 passes through a central bore in core member 56 so that control core members 55, 57 can move together relative to operating core member 56. By selective energization of electromagnets 51--54, type head 1 can be moved between four axially displaced positions, and control member 8a can be moved in synchronism with the movements of the type head between two control positions, each movement being a step corresponding to the thickness of one type disc.

FIGS. 11--14 show the positions of the core members for obtaining printing by the four type discs 15--18, respectively. The four printing positions of the type head shown in the upper parts of FIGS. 11--14 correspond to the four printing positions shown in FIGS. 4--7. The position of FIG. 11 corresponds also to the position of FIG. 8, but mechanical structure shown in FIG. 8 is omitted in FIGS. 11--14 for the sake of simplicity.

In the position of FIG. 11 and FIG. 8 type disc 15 is operative which requires placing of type disc 15 at the level of the printing area of platen 24, and placing of control member 8a in a position in which type disc 15 is advanced, and the adjacent type disc 16 is retracted, as also shown in FIG. 3.

Magnetic coils 53 and 54 have been energized so that magnetic control core 55 abuts the bottom of the casing structure 50a, and operating core member 56 abuts control core member 55. Control member 8a is in its lower position, and type head 1 is in its lowest position. A journal portion 21 has placed type disc 15 in the advanced position, whereupon the type head was moved to the printing position in which the selected type face abuts the printing area of the platen. The adjacent type disc 16 is retracted since the corresponding journal portion 21e is farther spaced from the printing area than the effective journal portion 21.

In the position of FIG. 12, magnetic coils 52 and 54 are energized, control core members 55 and 57 are in the lower position, and operating core member 56 is in a higher position abutting control core member 57. Since the type head has been raised one step, and control member 8a has remained in its previous position, type disc 16 has been shifted to the advanced position, while the adjacent type discs 15 and 17 are in the retracted position since they cooperate with journal portions 21e.

In the position of FIG. 13, magnetic coils 51 and 53 are energized, control core members 55 and 57 have been raised one step, and operating member 56 has been raised a step so that type disc 17 is in the advanced position and operative. Operating core member 56 abuts control core member 55.

In the position of FIG. 14, magnetic coils 51 and 52 are energized, control core members 55 and 57 cannot be further raised, since control core member 57 abuts the top of casing structure 50a, and operating core member 56 is raised into abutment with control core member 57 so that type disc 18 is advanced, and the adjacent type disc 17 is retracted.

Referring again to FIG. 11, assuming that a distance b between a nonselected type face and platen 24 is permitted, two adjacent rows of type faces would have to be spaced in accordance with the prior art a distance a1. In accordance with the present invention two adjacent rows of type faces can be spaced the distance a, which is half the distance a1. This is due to the fact that type discs adjacent to an operative type disc are retracted at the moment in which the printing is carried out.

Referring now to FIG. 15, the electromagnetic operating means 50 and casing 50a are schematically shown. Four first terminals 51a--54a are connected with magnetic coils 51 to 54, and the four other terminals 51b--54b are connected to ground. Terminals 51a and 54a are connected with two contacts of a switch 90 whose movable contact is connected to source 96. Terminals 52a and 53a are connected to the two stationary contacts of a switch 91 whose movable contact is connected to a voltage source 97. Each key lever 92 of the typewriter has either a projection 92a, or a projection 92b, the respective projections respectively cooperating with two bails 93 and 94 which are mounted for turning movement in supports 95, of which only one is shown. The end portions 93a and 94a cooperate with switch 90, and the end portions, not shown, at the other end of bails 93, 94 cooperate with switch 91. Depending on which projection 92a, 92b is provided, and on the construction of the end portions of the bails, switches 90, 91 are shifted and connect different pairs of coils to the voltage sources. In the position illustrated in FIG. 15, switches 90 and 91 connect the voltage sources 96 and 97 with the terminals 54a and 52a of magnetic coils 54 and 52, corresponding to the position shown in FIG. 12. Springs 98 are connected to the bails 93 and 94 for urging the same against projection 92a or 92b, respectively, of key lever 92.

Operating rack bar 14 can be shifted in longitudinal direction by conventional mechanism, or by an electromagnetic operating arrangement similar to the construction described with reference to FIG. 15. However, the operation of operating rod 14 is not an object of the present invention.

Summarizing, the apparatus is operated in the following manner.

1. When a key associated with a selected character is depressed, operating rack bar 14 is longitudinally shifted so that the type head is turned by tubular support 2 to a position in which the type face carrying the selected character is located opposite the printing area of the platen.

2. The actuation of the key has also effected setting of the switches 90 and 91 to a position energizing a pair of magnetic coils of the electromagnetic operating means 50 so that tubular support 2 is axially shifted simultaneously with control rod 80, 8. The correct relative position between the journal portions of control member 8a and the type discs is automatically obtained by the electromagnetic operating means 50 so that the type disc carrying the selected type face is placed by support 2 and operating members 58 at the level of the printing area of the platen, while simultaneously control member 8a is placed in a position in which a journal portion 21 coaxial with tubular support 2 engages the inner bearing 19, 20 of the respective selected type disc.

3. The placing of the selected type face opposite the printing area has been carried out while the type head is in a position spaced from the printing area. An electromagnet, not shown, is now energized to operate armature rod 13 shown in FIG. 1 so that frame 9 tilts the supporting tube 2 with a type head from the inoperative position shown in FIG. 9 to the printing position shown in FIG. 8, while tubular support 2 tilts about joint A, and control rod 8 tilts about joint B as also shown in FIG. 10. In the position of FIG. 9, gear 14a only loosely engages rack portion 14a, and in the position of FIG. 8, the meshing teeth hold the tubular support 2 and the type head accurately in an angular position in which the selected type face prints the respective character in the correct position.

The retraction of the type discs adjacent to the operative type disc permits a very close axial spacing of the adjacent circular rows of type faces, and the axial thickness of each type disc need only be as large as required by the height of the type faces. The diameter of a type disc is also reduced to a minimum so that the inertia and mass of the type head are small. Due to small mass and small dimensions of the type head, very high typing speeds can be obtained. The weight of the type head can be further reduced by making the type discs of a synthetic plastic material, and only bearing rings 19 of steel.

In a modification of the invention, not shown, only one eccentric journal is provided on the control member so that the same has to be shifted between four positions for displacing a selected one of the four type discs to the advanced position before the type head is shifted to the printing position.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of type head constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a type head composed of a plurality of relatively shiftable type discs having peripheral type faces together representing a system of characters, digits and symbols, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.