GB2246326A - Geometry of dot-printing elements in a multi-printhead print-carriage - Google Patents

Abstract

A print carriage (10) reciprocates across the width (S) of the substrate to be printed on with an amplitude ST. The carriage bears a plurality of equispaced printheads (12)(14)(16) separated by distances H, and each printhead comprises two columns of printing elements separated by distance c, one column being vertically displaced with the other so as to be interdigitated therewith at a pitch g. The pitch of printed dots is P. If the number of printheads (12 - 14) is N, then preferably (a) g=1 DIVIDED 2P (b) c=S3N - 1 DIVIDED 2P <IMAGE>

Description

SERIAL DOT PRINTER WITH ALTERNATE DOT DISPOSITION Description This invention relates to an alternate dot disposition in a serial dot printer to enable a reduction in the power consumption of the apparatus.

Recently, a variety of printers have been proposed as output apparatus for such machines as desk top calculators, microcomputers etc.. In particular, small-sized and inexpensive printers are desired.

As an example of such simplified printers, a serial printer is well known.

In a typical serial printer, a printing head executes the printing operation by being reciprocally driven along a platen around which recording paper is wound. Although such a serial printer is somewhat inferior to a large-sized line printer in printing speed, it can realize a structural simplicity and low cost.

As a serial dot printer using a dot type printing head, a so-called tandem type printer is known. In a tandem type printer, a plurality of dot printer heads are arranged at regular intervals in the carriage running direction on the carriage. The carriage, opposed to the platen, is capable of reciprocally running in the serial printing direction.

In a tandem type printer, a divided printing method is often used. In this method, the distance between the respective printing heads on the carriage is established with a value obtained by dividing the width of the total printing area by the number of printing heads. The carriage moves for the same distance as the total interval of the printing heads, thereby executing the printing operation on the recording paper. Upon completion of all the printing processes in the printing direction, one line has been printed. Thereafter, the printing operation starts with a new line.

In such a tandem type printer having a plurality of printing heads, the printing operation is executed by a simultaneous movement of all heads, namely, the dot pins (printing needles) of the printing heads are all driven at the same time. As a result, the power consumption at a specific time becomes very large so as to require a large-sized power source. In consequence, the productive and operative costs, the volume, the weight of the printer are significantly increased, and the temperature of the printer rises.

Particularly, when the dot pins of the printing heads are disposed alternately and the number thereof is large, the number of dot pins to be driven at the same time becomes proportionally large, thereby amplifying the above-mentioned disadvantage.

It is therefore an object of this invention to provide a serial dot printer in which a plurality of printing heads with alternate dot disposition are arranged on a single carriage, said printing head being capable of effectively reducing the power required at each printing strike thereby affording the use of a power source of small capacity.

Accordingly this invention provides a serial dot printer with alternate dot disposition having a plurality of printing heads, integrally fed in the serial printing direction and each having an alternate dot disposition, which are arranged a fixed distance apart, wherein, when the total printing width is S; the number of printing heads is N; and the dot pitch to be printed is P, the alternate dot pitch is set to 1/2 P, and the head pitch D is set to D = S/N - 1/2NP.

In accordance with this invention, the printing operation is carried out in such a manner that at the time of each printing strike, only one pin row of one printing head is driven, by individually delaying the driving timing between the respective pin rows of the printing heads.

As a result, the power required at the time of each printing strike is always only that necessary to drive one pin row.

Consequently, all the pin rows of the printing heads need not be driven simultaneously, thereby significantly reducing the power source capacity and realizing a small-sized apparatus.

The invention is further described below, by way of example, with references to the accompanying drawings in which: FIG. 1 is a schematic view illustrating the principle of operation of a serial dot printer according to this invention; FIG. 2 is an enlarged view showing the alternate dot disposition of the respective head in FIG. 1; and FIG. 3 is a view showing the operation of the composition shown in FIG. 1.

The present invention is particularly useful when embodied in a serial dot printer such as shown in FIG. 1, which schematically shows a principle composition of a serial dot printer with alternate dot disposition according to the invention.

In FIG. 1, a plurality, e.g. three, of printing heads are disposed on a carriage provided to be receprocally movable in the longitudinal direction of a platen in a serial dot printer having a total printing width S, with a uniform head pitch H.

Each printing head moves over an allocated distance (printing stroke) ST. The dot pin is driven, at a printing position against the recording paper on the platen.

In such a serial printer, for precisely and readably printing Kanji (Chinese characters used in Japanese writing) and Hiragana (the cursive kana characters) with high quality, it is necessary to increase the number of dots for one character.

For this end, a method has been adopted heretofore, in which the number of dot pins in each of the printing heads is increased, and disposed alternately so as to be driven with a time lag, thereby printing the respective character on the recording paper. In the present embodiment, as a matter of convenience, the right side pins of the printing heads 12, 14 and 16 are refered to as right row pins 12a, 14a and 16a, while the left side pins are refered to as left row pins 12b, 14b and 16b.

FIG. 2 shows an enlarged view of the alternate dot pin disposition of the printing heads. The right row pin a and the left row pin b are disposed with a distance c in the lateral direction and with a distance g in the vertical direction, respectively therebetween.

In such a case, if all the right and left row pins of the printing heads are simultaneously driven, a disadvantage would arise in that the required capacity of the power source would become too large.

For a significant feature of this invention, the right and the left row pins of the printing heads are disposed at mutually different positions with respect to the printing positions. As a result, it is possible to avoid simultaneous driving of the plurality of pin rows by a single energization. Namely, at the most only one row of pins are driven at one time, before successively shifting to the other rows. Thus, the capacity of the power source required to perform one driving operation is minimized to that which is enough to drive one row of pins, thereby avoiding the enlarging of the power source capacity and the size of the apparatus.

The specific composition and operation of this embodiment will now be described with reference to FIG. 3 where the dimensional relationship between the pins is schematically established for expressive convenience, not precisely corresponding to the actual disposition.

In FIG. 1, it is assumed that the total printing width in the serial printing direction is S; the number of printing heads is N and the dot pitch to be printed is P; the head pitch (distance between the dot pins) is set to S/N - 1/6P, and the alternate dot pitch (distance between a right row pin and a left row pin in each printing head) is set to 1/2P, respectively.

Next, the operation will be described. At the time tl, a right row pin 12a of the first head 12 is struck against the recording paper at a predetermined position as shown by a black dot.

Thereafter, the carriage 10 shifts a predetermined distance to the right as shown in the drawing, and at the time t2 a right row pin 14a of the second printing head 24 is struck against the recording paper.

In the same manner, at the time t3 a right row pin 16a of the third printing head 16 is struck. Thus upon completion of the driving operation of the right row of pins of the printing heads, at the time t4 a left row pin 12b of the first printing head 12 is struck, and at the time t5 a left row pin 14b of the second printing head 14 is struck, and at the time t6 a left fow pin 16b of the third printing head 16 is struck, respectively, at the same positions in the carriage running direction as the positions printed by the right pin rows of the heads.

As a result, the number of thus simultaneously driven right row pins is, at the most, that equivalent to one full row.

Therefore, the required capacity of the power source need only be that necessary for driving this one row of pins, thereby significantly reducing the size of the power source and the apparatus.

In this manner, upon completion of the one basic cycle of the printing operation, at the time t7 the object to be printed by the respective printing head is shifted to the continuous position, and the same printing cycle will be repeated.

At the time t30, the left row pin 16b of the third printing head 16 will be struck at the right end printing position of the total printing width S, thereby terminating the printing operation over the entire stroke.

Thus, according to this embodiment, the printing operation over the total printing width S is executed at printing regions divided into three sections.

As mentioned above, this invention discloses a serial printer comprising a plurality of printing heads each of which has alternate dot disposition. The printed dot pitch is set in such a manner that only a single dot pin row will be struck at any one time. This is achieved by dexterously adjusting and establishing the distance between the printing heads, and the distance between the right and left pin rows in each printing head. As a result, the capacity of the power source can be reduced significantly to only that required for performing one printing stroke so as to enhance the efficiency of the consumptive power and to reduce the size of the printer.

Claims (2)

WHAT IS CLAIMED IS:

1. A serial dot printer with alternate dot disposition, in which a plurality of printing heads integrally fed in the serial printing direction, and each having an alternate dot disposition, are arranged at regular intervals, and in which, where the total printing width is S, the number of printing heads is N, and the dot pitch to be printed is P, the alternate dot pitch is set to 1/2 P, and the head pitch D is set to D = S/N - 1/2NP.

2. A serial dot printer substantially as herein described with referece to the accompanying drawings.