EP0033226A2

EP0033226A2 - Character selecting mechanism for a serial printer

Info

Publication number: EP0033226A2
Application number: EP81300288A
Authority: EP
Inventors: Shigemitsu Matsumori
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 1980-01-23
Filing date: 1981-01-22
Publication date: 1981-08-05
Also published as: EP0033226B1; JPS5928473B2; DE3170969D1; EP0033226A3; JPS56104079A

Abstract

A character selecting mechanism for a serial printer having a print head (3) incorporating a plurality of characters arranged radially about an axis, the said mechanism including a drive motor (1) for rotating the print head (3) connected to a shaft (5) of the drive motor (1) and longitudinal movement selecting means (2) for moving the shaft (5) axially.

Description

This invention relates to a character selecting mechanism for a print head for a aerial printer and it has particular, though not exclusive, application to a print head comprising a petal-type print thimble. The invention is particularly concerned with a character selecting mechanism which can be used for selecting one from two characters each arranged at a different distance along the length of a print head.
In a previously proposed serial printer, a petal-type print thimble comprises cylindrically disposed fingers on each of which two characters are arranged vertically one above the other. For character selection, the print thimble is rotated bi-directionally and/or it is moved vertically to select the character.
To accomplish character selection with this previously proposed arrangement, a mechanical movement must be carried out in both the rotational and the vertical directions, using, for example, a servomotor and a magnet. In the previously proposed arrangement, the print thimble is arranged on a torque-transmission mechanism including a slide sleeve assembly and a spline shaft, so as to enable the thimble to be rotated under the control of the servomotor and to be moved vertically under the control of the magnet. The torque-transmission mechanism is complicated and it includes parts which are delicate and difficult to manufacture. Any slackness of the torque-transmission mechanism results in a deterioration of the positioning of a character.
For vertical character-selection, the magnet selects one of two predetermined print positions (up and down) of the thimble. To print at a position other than those determined by the two predetermined print positions of the thimble, for example where H ₂0 or H 2 is to be printed, it is common practice to shift the printing paper by a half of the character size. However, such minute shifting of the paper is very difficult. In the case of printing in the German language, where the vertical positions of umlauts (··) for a capital and a small letter are different from each other there is a further problem. It is impossible with the previously proposed printer to use a single umlaut type or character element for both a capital and a small letter, unless the previously mentioned minute shifting of the printing paper is carried out.
It is, therefore, an object of this invention to provide a character selecting mechanism for a serial printer with a simplified construction and a high positioning accuracy.
It is another object of this invention to provide a character selecting mechanism which can be shifted longitudinally or vertically by a minute value.
According to this invention, there is provided a character selecting mechanism for a serial printer, the said serial printer having a print head incorporating a plurality of characters arranged radially about an axis thereof, characterised in that the said selecting mechanism comprises a driving motor for rotating the said print thimble connected to a shaft of the said driving motor and a longitudinal movement selecting means for moving the said shaft axially.
The above and other objects and advantages of this invention will be apparent from the following description of a preferred embodiment of the invention given, by way of example with reference to the accompanying drawings, whereins-

Figure 1 is a perspective view of an embodiment of the invention;
Figure 2(a) is a vertical sectional view of the embodiment shown in Figure 1;
Figures 2(b) and 2(c) are side views of a cam 11 used in the said embodiment;
Figure 3 illustrates a relationship between the print thimble position and the stepping number positions of the stepping motor; and
Figure 4 shows diagrammatically the characters to be printed and the order of operating the fingers of the thimble.

Referring to Figure 1, a type carriage assembly 100 for a serial printer includes a print head incorporating a petal-type print thimble 3. The print thimble 3 has sixty four fingers 15 arranged cylindrically. Two characters 14 are arranged vertically on, i.e. at different distances along, each finger, allowing for a total of one hundred and twenty eight characters on the print thimble 3. The print thimble 3 is mountedm a mounting member 4, which is secured with a shaft 5 of a servomotor 1, in the form, for example, of a stepping motor. The servomotor 1 drives the mounting member 4 which in turn rotates the print thimble 3 to the desired finger position. For character selection from two vertically arranged characters 14 on a finger 15 and for vertical shifting by a minute value, a longitudinal movement or vertical selecting means 2 is provided below the servomotor 1.
A print hammer (not shown) is incorporated in such a way that its action strikes the inside wall of a finger 15 of the print thimble 3. The print hammer carries a magnet. When it is energized by the action of a solenoid driver (not shown), the hammer is driven in free flight and strikes the finger 15 of the selected print thimble character 14. The hammer is reseated in its original position by virtue of the reaction produced by a recoil force, together with the force exerted by the magnet.
Referring to Figure 2(a), the stepping motor 1 comprises a stator 6, a rotor 7 secured to the shaft 5, and bearings 8 and 9 for supporting the shaft 5. The shaft 5 carrying the rotor 7 is not only able to rotate but it is also able to move vertically. The longitudinal or vertical selecting means 2, incorporates, for example, a stepping motor having a rotor and a stator and a shaft 10 which is connected to a cam 11. A roller 12 provided on the shaft 5 contacts the cam 11 in order to minimise the effects of friction. Rotation of the cam 11 moves the shaft 5 vertically by a distance defined by the angle of rotation of the cam 11. A difference in distance between the uppermost and the lowermost positions of the shaft 5 corresponds to the pitch of the vertically disposed characters 14 on the finger 15. A spring 13 provided in the stepping motor 1 urges the shaft 5 towards the cam 11.
When the cam 11 is positioned in the way shown in Figure 2(b), the print thimble 3 is at the uppermost position D, as shown by a solid outline in Figure 2(a), and when the cam 11 is positioned in the way shown in Figure 2(c), the print thimble 3 is at the lowermost position E, as shown by a dotted outline in Figure 2(a).
Referring now also to Figure 3, assume that the print thimble 3 moves vertically from the position D to the position E, the stepping motor 2 moving by a stepping number of 6, it is possible to assign the print thimble 3 to one of the positions h, i, j, k, and 1, as shown in Figure 3, by setting the stepping number. The positions h, i, j, k, and 1 are adjustable, as required, by properly designing the shape of the cam 11.
From Figure 3, it can be seen that the position h of the thimble 3 is shifted downwards from the position D by a minute value m, and the position k of the thimble 3 is shifted upwards from the position E by a minute value n. Thus, the print thimble 3 may be positioned, with a high degree of accuracy, at a position determined by the stepping number of the stepping motor 2.
Such a facility has considerable value, for example when in the German language A and a are to be printed. In such a situation only one printing element ".." (umlaut) is used for the.umlauts required for printing both A and a. As shown in Figure 4, the printing element "··" on a finger 15 is moved downwards by a minute amount p for use with "a", from the position which it occupied for use with "A".
It will be appreciated that, although the invention has been described, by way of example, with reference to a particular embodiment, variations and modifications can be made within the scope of the appended claims. For example, although in the preferred embodiment, it is explained that the shaft 5 is able to move vertically, it will be understood that the movement to which reference is made is that along the longitudinal axis of the shaft, which, in other embodiments, could be arranged to extend in a direction other than the vertical. Furthermore, other forms of motor 1 and 2 and other forms of lever mechanism than the rotatable cam 11 may be employed. It will also be understood that although the invention is particularly applicable to a printer having a petal-type print thimble, it can be employed with other types of print head having characters arranged radially about an axis. ,

Claims

1. A character selecting mechanism for a serial printer, said serial printer having a print head (3) incorporating a plurality of characters arranged radially about an axis thereof, characterised in that the said selecting mechanism comprises a driving motor (1) for rotating the said print head (3) connected to a shaft (5) of the said driving motor (1) and a longitudinal movement selecting means (2) for moving the said shaft axially.

2. A character selecting mechanism as claimed in claim 1 characterised in that the driving motor (1) includes a rotor (7) and a stator (6), the rotor (7) being carried upon a shaft (5) which is able to move axially and to rotate and the head (3) incorporating a thimble and being coupled to the shaft (5).

3. A character selecting mechanism as claimed in either claim 1 or claim 2 characterised in that the longitudinal movement selecting means (2) includes a cam(11) rotatable to move the said shaft (5) axially and a stepping motor arranged to rotate the cam (11).

4. A character selecting mechanism as claimed in any one of the preceding claims characterised in that there is provided a spring (13) arranged to urge the shaft (5) against movement axially by the longitudinal movement selecting means (2).

5. A character selecting mechanism as claimed in any one of the preceding claims characterised in that a roller (12) is provided between the shaft (5) and the longitudinal movement selecting means (2).