GB2057974A

GB2057974A - Printer

Info

Publication number: GB2057974A
Application number: GB8024345A
Authority: GB
Original assignee: Suwa Seikosha KK; Epson Corp
Current assignee: Suwa Seikosha KK; Epson Corp
Priority date: 1979-08-13
Filing date: 1980-07-24
Publication date: 1981-04-08
Also published as: JPS5627375A; JPS6227995B2; GB2057974B

Abstract

A flying serial printer comprising a rotatable character drum (12) having axially adjacent columns of print characters on the periphery thereof. A hammer (18) is movable in the axial direction of the character drum to print from a desired print character in each print column. An actuating shaft (26) of the same length as the axial length of the character drum is arranged to be rotated on energisation of the electromagnet. A trigger transmission member (24) is arranged to be rotated with the actuating shaft and is axially movable therealong. A trigger lever (23) is rotatably supported on a part of the transmission member and a rotatable cam (22), having substantially the same length as the axial length of the character drum, is arranged so that when the trigger lever is disposed in the path of rotation of the cam the latter is caused to contact the hammer to cause it to print from a desired print character on the character drum. The transmission member, the trigger lever and the hammer are movable stepwise between print columns. <IMAGE>

Description

SPECIFICATION Printer This invention relates to printers, for example, flying serial printers.

The present invention seeks to provide a lightweight and miniature printer which has a relatively small number of component parts, which is easily assembled and repaired and which, furthermore, is relatively inexpensive to produce.

According to one aspect of the present invention there is provided a printer comprising: a rotatable character drum having a plurality of axially adjacent columns of print characters on the periphery thereof; a hammer movable in the axial direction of the character drum to print from a desired print character in each print column; an electromagnet; an actuating shaft of substantially the same length as the axial length of the character drum and arranged to be rotated upon energisation of the electromagnet; a transmission member arranged to be rotated with the actuating shaft and axially movable therealong; a lever rotatably supported on a part of the transmission member; a rotatable cam member having substantially the same length as the axial length of the character drum, and arranged so that when the lever is disposed in the path of rotation of the cam member, the latter is caused to contact the hammer to cause it to print from a desired print character on the character drum; and means for causing the transmission member, the lever and the hammer to move stepwise.

According to another aspect of the present invention there is provided a printer comprising: a rotatable character drum having a plurality of axially adjacent print characters on the periphery thereof; a hammer movable in the axial direction of the character drum to print from a desired print character in each print column; an electromagnet; an actuating shaft of substantially the same length as the axial length of the character drum and arranged to be rotated upon energisation of the electromagnet; a transmission member arranged to be rotated with the actuating shaft and axially movable therealong; a lever rotatably supported on a part of the transmission member; a rotatable cam member having substantially the same length as the axial length of the character drum, and arranged so that when the lever is disposed in the path of rotation of the cam member, the latter is caused to contact the hammer to cause it to print from a desired one end of which the character drum is supported and adjacent the other end of which the electromagnet is mounted.

The printer may include a motor for rotating the character drum, the motor being mounted on the support means adjacent said electromagnet.

Preferably the printer includes a carriage on which the transmission member, lever and hammer are disposed.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a perspective schematic view of a conventional printer; Figure 2 is a side view of a printer according to the present invention; Figures 3 and 4 are perspective views of parts of the printer of Fig. 2; Figure 5 is a plan view of the printer of Fig.

2; and Figure 6 illustrates gearing of the printer of Fig. 2.

A conventional printer, as shown in Fig. 1, is a serial printer which is provided with a motor 3 to drive a print character drum 1 via a shaft 2, and a motor 6 to move a hammer 4 from one column to the next. The hammer 4 is moved along a hammer shaft 7 and a hammer guide shaft 11, by means of a hammer supporting frame 10 and an endless belt 8 which is moved by the motor 6. The hammer 4 is urged to strike against a desired print character on the print character drum 1 by rotating the hammer shaft 7 in the clockwise direction by means of a lever 9 actuated by a plunger 5, so that a printing operation is performed.In this conventional printer, since a large force is applied to the hammer shaft 7, the engagement between the hammer 4 and the hammer shaft 7 and/or the lever 9 when the hammer 4 is moved by the hammer shaft 7 and the lever 9 by the plunger 5, the hammer 4, the hammer shaft 7 and the lever 9 must be relatively massive so that they have sufficient strength to withstand the large forces applied to them.

In order to return the hammer 4 in a predetermined time after striking against a desired print character, a return spring (not shown) having a large force is provided.

Therefore, the plunger 5 has to be extremely large for driving the hammer shaft 7 and the lever 9 and for storing energy in the return spring. Thus the power consumption of the conventional printer is relatively high. Since the hammer shaft 7 and the lever 9 are relatively massive and heavy, the response time is poor and printing speed is relatively low. In addition, since a large force is applied to the moving parts of the conventional printer they are worn out relatively quickly, and require heat treatment for added strength.

Thus cost is increased.

A printer according to the present invention is illustrated in Figs. 2 to 6. As shown in Fig.

2 the character drum 1 2 having a plurality of axially adjacent columns of print characters on the periphery thereof, is rotatably mounted on a shaft 1 3 and is in contact with an ink roller 1 4. A mask 1 5 prevents the characters of the adjacent columns taking part in a printing operation and serves, together with a paper guide 16, as a guide for recording paper 32.

A carriage 1 7 is rotatably supported on shafts 19, 27, and carries a single hammer 18 and a trigger lever 23. The carriage 1 7 moves along the shafts 19, 27 in the axial direction, that is in the directions of arrows A, B (Fig.

4). The shaft 1 9 performs not only a guide function for the carriage 1 7 but also a paper feeding function since paper feeding rollers 54 are fixed at opposite ends thereof. An idler roller 20 is urged towards the paper feeding rollers 54 by a spring member 21.A ratchet wheel or cam 22, having substantially the same length as the axial length of the character drum, forces the hammer 1 8 to strike a desired print character on the character drum under the action of the trigger lever 23, A positioning lever 28 having triangular teeth 281 (best seen in Fig. 4) positions the hammer 1 8 exactly in relation to a given column of print characters on the character drum, and allows the carriage 1 7 to return to the home position when disengaged from an engagement member 171 on the carriage 17. Reference numeral 30 denotes an electromagnet energised during a printing operation and having an armature spring 31.

A motor 33 (Fig. 5) drives a motor gear 34 via a motor shaft 35. A transmission gear 36 is driven by the gear 34 and drives a ratchet gear 37 which, in turn, drives a reduction gear 38. A character drum gear 39 drives the character ring. A return electromagnet 40, when energised, actuates a return lever 41 and disengages the return lever from a selection lever 45. A shift gear 42 winds up a rope 43, one end of which is attached to a part of the carriage 17, and as it does so urges the carriage 1 7 to move in the direction of the arrow A. Reference numeral 44 denotes a shift transmission gear. A spring 46 urges the selection gear 45 to move in the direction of an arrow C. Reference numerals 47, 48 denote support frames.A return spring 49, one end of which is attached to the frame 47 and the other end to the carriage 1 7 returns the carriage 1 7 to the home position.

A paper feeding transmission gear 50 (Fig.

6), which has a cam portion 501, actuates a release lever 52 when the cam portion 501 is engaged with an end portion 521 of the release lever 52, and further actuates a transmission lever 53, thereby disengaging the positioning lever 28 from the carriage 1 7.

Reference numeral 51 denotes a paper feeding gear.

The operation of the printer of Figs. 2 to 6 will now be described.

First, a shifting operation of the carriage 1 7 will be described. Rotation of the motor 33 causes the character drum 1 2 to rotate by way of the motor gear 34, the transmission gear 36, the ratchet gear 37, reduction gear 38 and the character drum 39. At the same time as the character drum 1 2 rotates, the selection gear 45 is engaged with the transmission gear 44 since an end of the return lever 41 is engaged with the selection gear 45 which is coaxial with the shaft 13, and teeth of the transmission gear 44 cause the shift gear 42 to rotate intermittently.Each rotational step of the shift gear 42 winds up a length of the rope 43, which is attached to a part of the carriage 17, on a pulley portion 421 of the shift gear 42, the length of rope being slightly greater than the pitch p between columns of printing. The tension in the rope 43 is then released. As a result, the carriage 1 7 which is guided by the shafts 19, 27 moves by a step which is slightly more than the pitch p, in the direction of the arrow A, against the action of the return spring 49, and then retracts slightly in the direction of the arrow B. This retraction in the direction of the arrow B causes the engagement portion 1 71 of the carriage to be engaged with one of the triangular teeth 281 of the positioning lever 28, thereby bringing the carriage to rest.

Thus, the hammer is in an exact position corresponding to a column of print characters on the character drum 1 2.

Next, a printing operation will be described.

In order to print from a desired print character on the character drum 1 2 which is rotated by the motor 33, a trigger signal is applied to the electromagnet 30 and the latter attracts an armature 29 thereto. The movement of the armature 29 towards the electromagnet 30 causes a trigger lever actuating plate 25 fixed to a trigger actuating shaft 26, having substantially the same length as the axial length of the character drum, to rotate the latter in a counter-clockwise direction. A trigger transmission member 24 is also rotated in the counterclockwise direction, since it is attached to the trigger actuating shaft 26 by engagement in a U-shaped groove 261 in the periphery of the trigger actuating shaft.The rotation of the trigger transmission member 24 drives the trigger lever 23, rotatably supported on one end of the trigger transmission member 24, and an end portion 231 of the trigger lever 23 is thus disposed in a track of rotation of the cam 22. A portion 221 of the cam 22 strikes against the end portion 231 of the trigger lever 23, and the hammer 1 8 flies towards the character drum 1 2 and strikes a desired print character to print on the recording paper 32. When printing of one column is completed, the carriage 1 7 is shifted to the next column, since the rope 43 attached to one end of the carriage 1 7 is wound up on the pulley portion 421 of the shift gear 42 by the shifting operation described above and the carriage 1 7 is moved along the shafts 19, 27 in the direction of the arrow A together with the hammer 1 8 and the trigger transmission lever 24 to which the trigger lever 23 is attached. When the next desired print character on the character drum 1 2 comes face to face with the hammer 18, it is printed by repeating the above printing operation.

A paper feeding-operation and a carriage return operation will now be described. When the return lever 41 is moved in the direction of an arrow D by energising the return electromagnet 40, the return lever is disengaged from the selection gear 45, and the latter moves in the direction of an arrow C under the action of the spring 46 to engage with the paper feeding transmission gear 50. Rotation of the motor 33 is transmitted to the paper feeding transmission gear 50 through a toothed portion 452, of the selection gear 45, and the teeth of the paper feeding transmission gear 50 causes the paper feeding gear 51, fixed to the shaft 19, to rotate intermittently so that the recording paper is indexed by the paper feeding rollers 54.The cam portion 501 of the paper feeding transmission gear 50 is engaged with the end portion 521 of the release lever 52, so that the release lever 52 is rotated in the counter clockwise direction. The transmission lever 53, which is attached to the shaft 27 coaxial with the positioning lever 28, is rotated in the clockwise direction and the triangular teeth 281 of the positioning lever 28 are disengaged from the carriage 1 7. The carriage 1 7 thus moves in the direction of the arrow B under the action of the return spring 49 to return to the home position.

The layout of the printer will now be described referring to Figs. 2 and 5. The hammer 1 8 is opposite to the character drum which is rotatably mounted on the shaft 1 3 and permanently in contact with the ink roller 14. The hammer 1 8 and the trigger transmission member 24 are disposed on the carriage 1 7. The trigger lever 23, which is rotatably mounted on the carriage 17, is engaged with the trigger transmission member 24 which is engaged with the U-shaped groove 261 in the trigger actuating shaft 26. The trigger lever 23 is disposed in the track of rotation of the portion 221 of the cam 22 upon rotation of the trigger actuating shaft 26. The trigger lever actuating plate 25, which actuates the trigger lever 23, is fixed to one end of the trigger actuating shaft 26.The electromagnet 30, when energised, attracts the armature 29 thereto which is engaged with an end portion 251 of the trigger lever actuating plate 25.

The electromagnet 30 is fixed on the frame 47. The motor 33 is disposed in side-by-side relationship with the electromagnet 30. The hammer 18, the trigger transmission member 24 and the cam 22 which causes the hammer 1 8 to fly toward the character drum 1 2 are disposed between the character drum 1 2 and the electromagnet 30.The carriage 1 7 including the hammer 18, the trigger transmission member 24, the trigger lever 23, etc. can be moved in the direction of the axis of the character drum 1 2. The paper feeding rollers 54 are fixed to opposite ends of the shaft 1 9 supporting the hammer 1 8 and the carriage 1 7. The positioning lever 28 is rotatably attached to the shaft 27 also supporting the carriage 1 7.

Thus since the electromagnet 30 drives the trigger lever 23 through the trigger actuating shaft 26 and the trigger transmission member 24, there is, as a result, no necessity to move the electromagnet 30 with the carriage 1 7.

Therefore, the electromagnet 30 is fixed on the frame 47 and the motor 33 is mounted on the frame 48 in side-by-side relationship with the electromagnet to save space. It is thus possible that the printing means including the cam 22, the carriage 17, etc. are disposed between the electromagnet 30 and the motor 33, and the electromagnet 30 and the motor 33 are disposed opposite to the character drum 1 2 and side-by-side between the frames 47, 48. When the trigger lever actuating plate 25 fixed to one end of the trigger actuating shaft 26 is rotated in the counterclockwise direction when the armature 29 is attracted to the electromagnet 30, the trigger actuating shaft 26, which is rotatably supported by the frames 47, 48, is rotated.

Structurally, the inertial load on the trigger actuating shaft 26 depends mainly upon the weight of the trigger lever 23. Since the width b (Fig. 3) of the trigger lever 23 may be approximately equal to the thickness t of the hammer 18, the weight of the trigger lever 23 may be reduced, whereby superior response times are achieved. This results in reduction of the power consumption of the electromagnet 30 and in miniaturization of the electromagnet. The miniaturization of the electromagnet 30 is one of the main reasons why the electromagnet 30 and the motor 33 can be disposed in side-by-side relationship between the frames 47, 48.

The paper feeding rollers 54 are fixed to the shaft 1 9 supporting the hammer 1 8 and the carriage 1 7. The positioning lever 28 is attached to the shaft 27 supporting the carriage 1 7. This arrangement of the paper feeding rollers 54, the hammer 1 8 and the carriage 17, on the shaft 19, and the carriage 1 7 and the positioning lever 28 on the shaft 27, results in reduction of the number of component parts and contributes to low cost and miniaturization. The disposition of the trigger lever 23, driven with lower power in the track of rotation of the portion 221 of the cam 22 and the flying of the hammer 1 8 toward the character drum under the action of the cam 22 results in the provision of a flying serial printer with good response and high reliability.

Claims

1. A printer comprising: a rotatable char acter drum having a plurality of axially adjacent columns of print characters on the periphery thereof; a hammer movable in the axial direction of the character drum to print from a desired print character in each print column; an electromagnet; an actuating shaft of substantially the same length as the axial length of the character drum and arranged to be rotated upon energisation of the electromagnet; a transmission member arranged to be rotated with the actuating shaft and axially movable therealong; a lever rotatably supported on a part of the transmission member; a rotatable cam member having substantially the same length as the axial length of the character drum, and arranged so that when the lever is disposed in the path of rotation of the cam member, the latter is caused to contact the hammer to cause it to print, from a desired print character on the character drum; and means for causing the transmission member, the lever and the hammer to move stepwise.

2. A printer comprising: a rotatable character drum having a plurality of axially adjacent print characters on the periphery thereof; a hammer movable in the axial direction of the character drum to print from a desired print character in each print column; an electromagnet, an actuating shaft of substantially the same length as the axial length of the character drum and arranged to be rotated upon energisation of the electromagnet; a transmission member arranged to be rotated with the actuating shaft and axially movable therealong; a lever rotatably supported on a part of the transmission member; a rotatable cam member having substantially the same length as the axial length of the character drum, and arranged so that when the lever is disposed in the path of rotation of the cam member, the latter is caused to contact the hammer to cause it to print from a desired print character on the character drum; and support means adjacent one end of which the character drum is supported and adjacent the other end of which the electromagnet is mounted.

3. A printer as claimed in claim 2 including a mqtor for rotating the character drum, the motor being mounted on the support means adjacent said electromagnet.

4. A printer as claimed in any preceding claim including a carriage on which the transmission member, lever and hammer are disposed.

5. A printer substantially as herein described with reference to and as shown in the accompanying drawings.

6. In a miniaturized serial printer printing a desired character of at least one rotatable character ring having a plurality of characters on the periphery thereof by a single hammer selectively, the improvement comprising an electromagnet actuated by a trigger signal, a trigger actuating shaft extending over all columns rotated by said electromagnet, a trigger transmission member rotating simultaneously with said trigger actuating shaft and sliding on said shaft in a direction of thrust, a trigger lever rotatably supported by a part of said trigger transmission member and a ratchet wheel extending over all columns permitting said trigger lever to be interposed selectively in a track of rotation and providing printing energy for said hammer, said trigger transmission member and said trigger lever being shifted by step simultaneously with said hammer in the direction of thrust.

7. In a miniaturized serial printer printing a desired character of at least one rotatable character ring having a plurality of characters on the periphery thereof by a single hammer selectively, the improvement comprising: an electromagnet actuated by a trigger signal; printing means including a trigger actuating shaft extending over all columns rotated by said electromaget, a trigger transmission member rotating simultaneously with said trigger actuating shaft and sliding on said shaft in a direction of thrust, a trigger lever rotatably supported by a part of said trigger transmission member and a ratchet wheel extending over all columns permitting said trigger lever to be interposed selectively and providing printing energy for said hammer and said single hammer; said character ring having a plurality of characters such as letters, marks, symbols etc. on the surface thereof; and a motor directly or indirectly driving said character ring and said ratchet wheel; said character ring being disposed adjacent to one side of said printing means and said electromagnet and motor being disposed on the other side of said printing means.