Printing Mechanism Including Resiliently Biased Rotatable-type Wheels

Abstract

A printing mechanism having a plurality of type wheels mounted on a common shaft. Each of the type wheels is resiliently mounted for movement in the radial direction and an impression roller is arranged to contact the outer periphery of the type wheels. An arresting device is provided to keep the type wheels aligned after they have been set. The arresting device is a plurality of reciprocating members that engage the type wheels and hold them in place. These reciprocating members may be either a single pin that engages special teeth in a portion of the periphery of the type wheels, or they may be an arrangement with two claws which engage in recesses between the type on the type wheels. In the former, the type wheels are resiliently biased by springs mounted within the wheels themselves, and in the latter they are biased by springs mounted in the arresting device.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a printing mechanism for data processing machines. In particular, a roller printing mechanism for printing calculators having a plurality of adjacently disposed type wheels on a common shaft, an arresting device for the type selection and an impression cylinder. A resilient yielding between the type wheels and the impression cylinder is provided during the printing process.

The known roller printing mechanisms often produce unclean prints, since the type discs move out of line during the printing process and the printed symbols have smudged edges.

Among the known roller printing mechanisms are ones in which rigid type wheels cooperate with impression cylinders, which mechanisms are a combination of resilient elements for each column. In one such known embodiment, for example, that set out in German Allowed Application DAS 1,256,658, the impression cylinder is provided with pretensioned, cylindrical, annular springs which yield resiliently during printing of the types. These springs yield independently from one another, according to the associated type wheels, and produce a printing pressure which is independent of the fabrication tolerances and wear.

In the known printing mechanism set out in U.S. Pat. No. 3,381,790 to Chaveneaud et al., issued May 7, 1968, rigid mounted type wheels cooperate with an impression cylinder which consists of individual discs, each having a width corresponding to the width of the type wheels. Each one of these discs is provided with perforations in such a manner that a portion of the periphery is able to yield resiliently. In this portion there is again provided a small roller which is rotatably mounted and which is brought past the types in a rolling movement and serves as resilient printing abutment.

In both of these cases, an easily manufactured and installed, continuous roller printing mechanism which permits a uniform imprint to be achieved from the types of a plurality of adjacently disposed type carriers is not provided. Instead, each type wheel has its associated printing abutment, which is manufactured of a plurality of individual components, and which is, thus, expensive to produce and complicated to install. Moreover, care must be taken that the axial spacing of the resilient elements which take the place of the impression cylinder coincides with that of the type wheels. This means additional installation and fabrication difficulties. A further drawback is that a defined spring force can only be realized with difficulty during the printing process.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the above-mentioned drawbacks, and to provide a dependable and simple printing mechanism for data processing machines which produces a clear, uniform imprint.

This is accomplished according to the present invention in that type wheels are disposed on a common shaft radially against the printing direction so as to be individually resilient. Thus, it is possible to provide a simple, continuous impression cylinder as the printing abutment, and to combine the resilient arrangement with such components, which, due to their functional requirements, are expensive to produce and to install. This prevents the printing mechanism from being made more complicated. The continuous impression cylinder makes it unnecessary to take special measures with respect to the axial position of the type carriers relative to the impression cylinder. The printing mechanism according to the present invention produces a clear imprint due to the uniform yielding of each individual type carrier, in contradistinction to printing mechanisms with recoil rods where the type carriers must by given the opportunity to traverse the rest of the path in the printing direction at flying speed after passing through an acceleration section.

It is a further object of the present invention to provide a printing roller mechanism in which there is provided a device for aligning the individual type discs and wherein these aligned types are uniformly held in their printing position during the printing process so that the symbols are printed in a straight line.

This object is accomplished according to a preferred embodiment of the present invention in that the types on the type wheels are uniformly aligned by at least one pressure member serving as an arresting device and provided with at least two arresting claws; the arresting claws being insertable into the recesses separating the types from one another.

The contact pressure of the impression cylinder on the shaft of the type wheels is advantageously absorbed in the present invention by mounting the pressure members on a guide comb and biasing them. The guide comb is disposed in an imaginary plane which goes through the centers of the printing roller and the type wheel shaft.

In another preferred embodiment of the present invention the pressure members are advantageously made of a unitary piece of synthetic material with elastic regions being provided in their cross sections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view, partly in cross section, showing the type cylinder of a first embodiment of a printing mechanism according to the present invention.

FIG. 2 is a cross-sectional view taken generally along the line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional partial view taken generally along the lines 3--3 of FIG. 1.

FIG. 4 is a cross-sectional partial view taken generally along the line 4--4 of FIG. 1.

FIG. 5 is a side elevation, cross-sectional view of a printing mechanism having an aligning device with pressure members, according to a second embodiment of the present invention.

FIG. 6 is a partial top plan view partly in cross section, of the type cylinder and aligning device of FIG. 5.

FIGS. 7 and 8 each show a further embodiment of a pressure member for the embodiment of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment according to FIGS. 1-4, a shaft 2, which is provided with a plurality of adjacently disposed type wheels 1 to form a type cylinder 1' performs an oscillating movement, as indicated by the arrow in FIG. 2. During its clockwise rotation, it causes the type wheels 1 to be set and, thus, the selected types 20 to be positioned in printing position. The reverse rotational movement of the shaft 2, however, brings all the type wheels 1 back into their starting position.

For this purpose, a follower disc 3 (FIG. 4) is provided on shaft 2 for each type wheel 1 and is keyed to the shaft by tangential wedges 21, 21' extending over the entire length of shaft 2. On this follower disc 3, there are disposed receiver discs 4 (FIG. 3), to which is imparted the rotational movement of the follower discs 3, but which are additionally mounted loosely on shaft 2 so as to be able to perform a radial movement. Longitudinal slotted guides 7, on the follower discs 3 define the radial direction of movement of the receiver discs 4. Bolts 8, which are attached in a known manner to discs 3, slide in slots 7. A guide rail, or rod 9, which is common to all the type wheels, may also be used, either in addition to or in place of pin 8. Moreover, each wheel 1 has a wire spring 10 supported by the bolts 11 provided on follower disc 3 and acts within cutout area 22 in the receiver disc 4 against the cam 12 of the receiver disc 4 to hold disc 4 in contact with shaft 2. Type rings 6 are arranged about the periphery of receiver discs 4 to be freely rotatable, and are restrained in the axial direction by resilient arms 13,13' of pressure plates 5, which are fastened to receiver discs 4 by means of bolts 23, and by flaps 14,14' of receiver discs 4. Thus, follower discs 3 and pressure plates 5 take over the lateral guidance of type rings 6. Combs 19, which pass through recesses 24 in the type wheels 1 and which are fastened to end plates 25, 25' of the type cylinder 1' in any suitable, well-known manner hold the type wheels 1 at a uniform distance from one another by means of slots 19'.

The setting movement of the shaft 2 in the clockwise direction cause all the type wheels 1 to rotate, and type rings 6 are carried along by friction due to the pressure between flaps 14, 14' of the receiver discs 4 and the resilient arms 13, 13' of the pressure plates 5. During the rotational movement, arresting pins 26 of an arresting device 16 engage into teeth 15 of type rings 6. Teeth 15 correspond to the selected types 20 in each column, and stop the movement of type rings 6 unless the selected type requires passage of a type ring 6 until end abutment 17 abuts on abutment surface 27. Pins 26 are mounted for axial reciprocation, and may be actuated in any suitable well-known manner. Shaft 2, follower discs 3, receiver disc 4 and pressure plate 5 complete their rotational movement without being hindered in any way, due to the friction coupling. In the rest position of shaft 2, the set types 20 are printed by a rolling process resulting from the rotation of an eccentrically mounted impression cylinder 28 around its bearing pin 29. The contact pressure of types 20 is determined by springs 10, which at the same time compensate for manufacturing tolerances and wear on the type wheels 1. After completion of the printing step, but before the resetting movement of shaft 2 is initiated, the arresting pins 26 are brought out of engagement with type ring teeth 15. Rotation of shaft 2 in the counterclockwise direction now returns the follower, receiver and pressure plates 3, 4, 5, and, thus, type rings 6, into their starting position. This position is determined by an abutment 18 on type rings 6 which abuts on a surface 30 of device 16 provided for this purpose and brings the shaft 2 to its other end position. The above procedure can then be repeated.

The embodiment shown in FIGS. 1-4 of the drawings relates to a roller printing mechanism in which the types 20 are printed by an eccentric rotational movement of the impression cylinder 28, and by a rolling movement caused thereby. The printing process may however also be accomplished by other movements, e.g. transversal movement of the type carrier and the pressure roller 28 with respect to each other.

The various parts of the type wheels, the arresting device and the impression cylinder may be made of suitable, conventional materials.

FIG. 5 shows a cross-sectional view of a second embodiment of the present invention having an impression cylinder 28' eccentrically mounted on pins 29'. This eccentric mounting again causes the cylinder 28' to press when rotating, onto an oscillating type cylinder 31', consisting of a plurality of individual type wheels, or discs 31. The type discs 31 are mounted on individual sliding discs 61', each consisting of two halves 61 and 62. The sliding discs 61' are mounted on the shaft 2' of the type cylinder 31'. To compensate the contact pressure movement of the cylinder 28', the sliding discs 61' are resiliently mounted on two wire, or leaf, springs 121 and 122. All the sliding discs 61' are aligned vertically by two centering pins 116, 117. The type discs and the sliding discs are held through end caps 52,52' at the ends of the roller by retaining rings 51, 51', which are inserted into shaft 2' in the known manner (see FIG. 6).

The individual type discs 31 are each set by a drive pinion 151, only one of which is shown. These drive pinions 151 are actuated in any suitable, well-known manner. The individual type discs are then aligned into the proper printing position by a plurality of reciprocable pressure members 41. Each individual type disc is held in the proper printing position by a respective pressure member, so that when the impression cylinder 28' comes in contact with the printing types the letters will not be smudged on the recording carrier 126 (FIG. 5). Carrier 126 may be a strip of paper. Each pressure member 41 is provided with two arresting claws 401 and 402, which engage into the recesses 201 between the individual types 20' during alignment of the type discs and, thus, arrest each type wheel in a stable force system consisting of shaft 2' and the pressure member 41 with its two arresting claws, this means that the discs 31 are held in a three-point bearing and cannot be moved out of place.

The guide comb 111 is disposed in an imaginary plane which passes through the center points of the pressure roller 28' and the type cylinder shaft 2'. The individual pressure members 41 are mounted in recesses 121 of the pressure comb 111 so as to be resiliently displaceable.

The resilient mounting is accomplished by a tension spring 115 provided for each pressure member, which spring 115 is fastened to a spring support 114 at its one end and in a hole 216 in the pressure member 41 at its other end. When the impression cylinder comes in contact with the aligned type discs, the pressure members absorb the contact pressure of the impression cylinder by moving radially with respect to disc 31 on the guide comb 111. After the printing step is completed and the pressure is withdrawn, the individual pressure members 41 return to their starting positions.

After each printing cycle the type cylinder 31', i.e. the individual type wheels, is newly set by retracting the guide comb 111, together with the individual pressure members 41 as a unit. Any suitable, well-known means may be used to actuate the comb 111.

FIG. 6 shows a top plan view partly in cross section of the type cylinder 31' with the individual type discs 31 and the arrangement of the individual pressure members 41 on the common guide comb 111. The individual type discs 31 are seen to be mounted on the slide disc halves 61 and 62, which are mounted on the common shaft 2'. The two centering pins 16 and 17 align the slide discs. End caps 52, 52" with retaining rings 51, 51' hold the entire type cylinder 31' together. The guide comb 111 is provided with a plurality of recesses 111' and 121. The recesses 111' receive the spring supports 114; recesses 121 receive the pressure members 41. The tension spring 115 serves for the elastic displaceability of the individual pressure member 41 on the guide comb 111. More than one spring 115 may be used if desired.

During printing, the individual type discs are kept in alignment by the pressure members 41. After printing, the guide comb 111, together with the pressure members 41, disposed thereon, is retracted and the individual type discs 31 can be reset for the next printing cycle.

FIG. 7 shows a cross-sectional view of a modified arrangement of a pressure member 41' with the spring support 114' and the tension spring 115'. Spring support 114' and pressure member 41' are placed onto guide comb 111.

FIG. 8 shows a pressure member 41" constructed of a synthetic material, for example Delrin. It is provided with two arms 411, 412 which engage into a recess 101 of the guide comb 111. When the impression cylinder 28' presses onto the type discs 31, the pressure is transmitted to the pressure member 41" through claws 401', 402', and arms 411, 412 are deformed and absorb the contact pressure. After completion of the printing step, the pressure member returns to its normal position.

It is possible for the pressure members to have different shapes than those shown without departing from the basic idea of the invention. Thus, all pressure members may be combined into a single component which is pressed, for example, out of a plastic synthetic, for example Delrin. Such a fabrication may be done, for example, by well-known means.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims

I claim:

1. A printing mechanism comprising, in combination:

a. a shaft having an axis;

b. an impression cylinder arranged parallel to said shaft;

c. a plurality of type wheels each being mounted on said shaft for pivotal movement about said axis, into different printing positions opposite said impression cylinder, each of said type wheels having a type ring mounted on said shaft, a pressure plate mounted on one face of said type ring to restrain said type ring in one axial direction, a follower disc adjacent the other face of said type ring and mounted rigidly to said shaft; said type ring and said pressure plate forming an assembly mounted to said follower disc;

d. means for arresting each of said plurality of wheels in any one of said different printing positions; and

e. means mounting said type wheels for radial movement relative to said axis and for resiliently yielding relative to said impression cylinder during printing, said mounting means including means for mounting said assembly loosely on said shaft so as to be radially displaceable with respect to said shaft and means to resiliently bias said assembly against said shaft.

2. A printing mechanism as defined in claim 1 wherein each of said type wheels has a receiver disc mounted on said shaft and said type ring is mounted about the periphery of said receiver disc, said receiver disc, type ring and pressure plate forming an assembly mounted to said receiver disc, and said follower disc has two pins extending axially toward said receiver disc and said resilient means is a resilient elongated member having its ends in contact with said pins, said receiver disc having a cam element contacting said elongated member at a point between said pins so as to be resiliently biased thereby.

3. A printing mechanism as defined in claim 2 wherein said follower disc has at least one pin means extending axially outward from the same face as said pins and wherein said receiver disc has at least one slot which receives said pin means so that said receiver disc is radially displaceable with respect to said follower disc and said shaft.

4. A printing mechanism as defined in claim 3 wherein the printing position of the types to be printed is in a plane between said impression wheels and said type cylinder.

5. A printing mechanism as defined in claim 3 wherein said at least one pin means is at least one guide rail which is common to all of said type wheels.

6. A printing mechanism as defined in claim 5 wherein said type rings are mounted on the periphery of said receiver disc so as to slide thereon and wherein said receiver disc has at least one resilient projecting portion in contact with said type ring on one axial face thereof and said pressure plate has at least one resilient projecting member in contact with said type ring on the other axial face thereof so as to provide a friction coupling between said receiver disc, said pressure plate and said type ring.

7. A printing mechanism as defined in claim 6 wherein said arresting means has a stationary support member and a reciprocating member mounted in said support member and said type ring has teeth for engagement with said reciprocating member and at least one radially extending stop member for engaging with said support member.

8. A printing mechanism as defined in claim 7 further comprising at least one comb member arranged to maintain said follower discs at an axially uniform spacing.

9. A printing mechanism as defined in claim 1 wherein one pressure member is provided for each of said plurality of type wheels.

10. A printing mechanism as defined in claim 9 wherein said pressure members are constructed in one piece from an elastic, synthetic material.

11. A printing mechanism comprising, in combination:

a. a shaft having an axis;

b. eccentrically mounted impression cylinder means arranged for rotation parallel to said shaft for performing a printing movement;

c. a plurality of type wheels each being mounted on said shaft for pivotal movement about said axis, into different printing positions opposite said impression cylinder;

d. means for arresting each of said plurality of wheels in any one of said different printing positions for alignment only; and

e. means mounting said type wheels for radial movement relative to said axis and for resiliently yielding relative to said impression cylinder during printing, said mounting means including means for mounting said type wheels loosely on said shaft so as to be radially displaceable with respect to said shaft, and means for resiliently biasing said type wheels only against said shaft and towards said impression cylinder.

12. A printing mechanism as defined in claim 11 wherein said arresting means has at least two arresting claw members and wherein said type wheels have type elements about their periphery, said type elements forming recesses between them and said arresting claw members engaging in the recesses to arrest each type wheel.

13. A printing mechanism as defined in claim 12 wherein said arresting means is a pressure member including said at least two arresting claws, said claws and said shaft acting to form a triangular force system which is highly stable.

14. A printing mechanism as defined in claim 13 further comprising a guide comb member providing a support for said pressure members and wherein said mounting means includes mounting said type wheels loosely on said shaft so as to be radially displaceable with respect to said shaft and means biasing said pressure members against said type wheels in opposition to the pressure exerted on said type wheels by said impression cylinder, said guide comb member being arranged in an imaginary plane which goes through the center points of said impression cylinder and said shaft and disposed for removal of said arresting claws from said recesses by the movement of said guide comb member radially away from said type wheels.