GB2171648A - Carrier feed device for a printing machine - Google Patents

Abstract

The device comprises a carrier drive stepping motor 11 and a capstan 18 both mounted on a carrier 1 which is mounted for sliding movement across the machine, and a wire secured at opposite ends thereof to left and side walls of a machine frame and having an intermediate portion thereof wound in several turns around the capstan. Thus, as the capstan is rotated by the drive motor, the carrier is fed in a self-propelling manner by the drive motor carried on the carrier itself. A fly-wheel is secured to an output power shaft of the carrier drive motor in order to smooth continuous stepwise movement of the carrier. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a carrier feed device for a printing machine This invention relates to a carrier feed device for use with a typewriter, printer or like printing office machine, and more particularly to a carrier feed device of the type in which a wire partially wound around a capstan feeds a carrier across a typewriter or printer as the capstan is rotated by a reversible or bidirectional drive motor.

A carrier feed device of the type mentioned is disclosed, for example, in Japanese laid-open Patent No. 55-34941. In this device, a carrier drive motor and a capstan are mounted at a given position on a typewriter or printer body, and a wire is connected to and extends between a carrier and the capstan around left and right guide pulleys so that the wire may be wound to feed the carrier as the capstan is rotated.

However, such a conventional carrier feed device has the following drawbacks. First, since the wire extends between the capstan and a carrier around the left and right guide pulleys, the wire is liable to be slack or lax, causing incorrect positioning of the carrier. Second, since the wire has a considerable length, an error of positioning of the carrier due to possible elongation of the wire is significant. Third, since the wire is continually moved, it may be damaged by the movement. In addition, due to such an arrangement of guide pulleys, it is not possible, when seeking to design a compact typewriter or printer, to reduce the size of the typewriter or printer below a certain limit.

It is an object of the present invention to provide a carrier feed device in which the drawbacks of conventional feed devices as described above are reduced or obviated.

According to this invention there is provided a carrier feed device for a printing machine comprising: a carrier mounted for movement across the machine; a reversible drive motor mounted on said carrier; a capstan mounted on said carrier and connected to be rotated by said drive motor; a wire partially wound around said capstan; and means for securing opposite ends of said wire to stationary portions of the machine; whereby said carrier is fed as said capstan is driven to rotate by said drive motor.

Preferably said wire comprises a pair of segments each having one end secured to said capstan and wound, at a portion adjacent the one end thereof, in one or more turns around said capstan.

The segments are each wound in the same sense so that, as the capstan rotates, one segment is wound onto the capstan as the other segment is wound off the capstan. Alternatively a single wire may be utilised, a portion of the wire intermediate its ends being wound onto the capstan.

Advantageously, the means for securing said opposite ends of the wire is adjustable for permitting adjustment of the tension of said wire.

Advantageously the carrier may further comprise a fly-wheel connected to be driven by an output power shaft of said drive motor for smooth stepwise rotation of said drive motor and smooth stepwise feeding movement of said carrier.

Advantageously the fly-wheel is secured directly to said output power shaft of said drive motor.

Conveniently the drive motor is a stepping motor.

As the capstan is rotated by the carrier drive motor, the carrier is fed in a self-propelling manner.

In order that the invention may be more readily understood and so that further features thereof may be appreciated, the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of a carrier feed device embodying the present invention; Figure 2 is a sectional view taken along line 1-1 of Figure 1; Figures 3 to 6 are graphs showing the relation between excitation phase positions of a stepping motor and movement thereof; Figure 7 is a graph showing a position deviation of the stepping motor from a reference position; and Figure 8 is a graph showing a speed variation of the stepping motor.

Referring initially to Figures 1 and 2 of the drawings a carrier body 1, which forms part of a printer or typewriting machine, is formed as a box which is open at its front and includes a cassette supporting plate 3, a bottom plate 4, left and right side plates 5 and 6, and a back plate 7. The carrier body 1 is mounted for slidably leftward and rightward movement on a front guide shaft 8 and a back guide shaft 9 in parallel to a platen 10. A reversible carrier drive stepping motor 11 and a reversible ribbon drive DC motor 12 are mounted in the carrier body 1.

The stepping motor 11 is mounted on a Ushaped mounting frame 13 fixed to the bottom plate 4. The output shaft 11a of the stepping motor 11 is connected to a capstan 18 through a gear mechanism including a small gear 14, a large gear 15, a middle gear 16 and another large gear 17 so that the stepping motor can drive the capstan rotationally. The small gear 14 is fixed to one end of an output power shaft 11a of the stepping motor 11. The large gear 15 is integral with the middle gear 16 and is supported for rotation on the mounting frame 13. The large gear 17 is integral with the capstan 18 and also supported for rotation on the frame 13. A fly-wheel 11b is fixed on the other end of the output power shaft 11 a of the stepping motor 11.

A pair of wires 20 and 21, termed the left wire and the right wire are each connected at one end thereof to the capstan 18 and wound along a spiral groove 19 formed on an outer peripheral face of the capstan 18. The other ends of the wires 20, 21 are secured to opposite left and right side plates 28 of a typewriter or printer body (not shown) by securing means 22 whereby the tension of the wires 20, 21 can be adjusted. The securing means 22 may be in the form of a bolt or the like screwed in the side plate 28 having an axially extending hole formed therein through which the said other end the wires 20 or 21 extends so as to be secured to the bolt.

It is to be mentioned that the wires 20, 21 may be replaced by a single continuous wire which is wound at an intermediate portion thereof in several turns around the capstan 18.

Thus, as the stepping motor 11 is rotated in a forward or reverse direction, the capstan 18 is rotated in a forward or reverse direction to wind one of the wires 20, 21 onto the capstan 18 while the other wire 20 or 21 is unwound from the capstan 18. Accordingly, the carrier 1 is slid leftwardly or rightwardly on the guide shafts 8 and 9 as the stepping motor 11 mounted on the carrier 1 itself is rotated in the forward or reverse direction. Since the fly-wheel 11 is secured to the output power shaft 11a of the stepping motor 11, when the carrier 1 moves continuously such as, for example, in a tabbing operation, vibrations by stepwise revolution of the stepping motor 11 are moderated or reduced by the fly-wheel 11 b and thereby the carrier 1 can be smoothly and continuously fed.

Figure 3 is a graph showing a manner of position control where the stepping motor 11 rotates by twelve steps to move the carrier 1 for tabbing operation. In this figure, a thick full line indicates excitation phase positions of the stepping motor 11, a broken line indicates controlled positions (movement of the stepping motor) where not flywheel is connected to the stepping motor 11 or the fly-wheel 11b is free from the stepping motor 11, and a thin full line indicates controlled positions with the fly-wheel 11b connected with the stepping motor 11 as in the embodiment.Since the stepping motor 11 effects position control in a digitally stepwise manner as seen from a thick full line, if the inertia of the stepping motor and its driven system is sufficiently low, the stepping motor 11 will move clumsily in a stepwise manner as seen from the stepped thick full line because the stepping motor has a good follow-up property of the driven system to its excitation phase position. Accordingly, normally a stepping motor will be accelerated or decelerated suitably in order to move a driven system smoothly. However, if the stepping motor is position controlled in accordance with such acceieration or deceleration, the stepping motor will move clumsily particularly at a low speed (when variation of steps per unit time is low). The reason is explained below.

Where a stepping motor has a high inertia, a high torque is required in proportion to the inertia when its speed is to be changed. Accordingly, where the torque is constant, a speed variation becomes smaller as the inertia increases. Figures 4, 5 illustrate the relations between excitation phase positions of a stepping motor and movement thereof at a stage where target point, that is to say the point at which it is desired to locate the carrier, is being reached, Figure 4 showing those where the inertia is high and Figure 5 showing those where the inertia is low.

Thus, if a stepping motor which will effect such movement as seen from a thin full line in Figure 6 is to be controlled for the excitation phase position as seen from Figure 4, the stepping motor will first move to a position as indicated by "2" in a period of time Tb and will thereafter stay at the position "2" for a following period of time Ta-Tb. Accordingly, the stepping motor is apparently braked, resulting in clumsy movement thereof.

In other words, even if the output power of the stepping motor is reduced while the excitation phase time T is increased, the stepping motor will reach the position "2" in the time Tb and will tend to stay at the position for the remaining time Ta Tb. Therefore, the stepping motor 11 will not move smoothly.

When a stepping motor having a low inertia is fed as seen from Figure 5, acceleration of the stepping motor will increase. When the stepping motor starts or stops, the driven system will be vibrated heavily and hence a high stress will be applied thereto. Consequently, it is hard to control starting or stopping of the stepping motor.

If a fly-wheel is connected to a stepping motor and a high inertia is given to the output torque of the stepping motor, the stepping motor will move smoothly (as shown by the thin full line in Figure 3) and hence can be positioned accurately and instantly at a target position without heavy vibrations at a stage when the target position is reached and without continuing vibrations after then. Figure 7 is a graph illustrating a change of position deviations and Figure 8 is a graph illustrating a change of speed of a stepping motor, and in Figure 8, a full line illustrates such a speed change in case of the stepping motor connected to the fly-wheel and a broken line illustrates a speed change in case of the stepping motor without a fly-wheel.

Referring again to Figures 1 and 2, the ribbon drive DC motor 12 is mounted on another mounting frame 23 which is fixed to the bottom plate 4.

Revolution of the ribbon drive DC motor 12 is transmitted to a half rotation cam 27 through gears 24, 26. Thus, the half rotation cam 27 is rotated in a forward or reverse direction by an angle of 180 degrees by rotation of the ribbon drive DC motor 12 in a forward or reverse direction. When the half rotation cam 27 is rotated in the forward direction by 180 degrees, a print ribbon (not shown) in a print ribbon cassette 49 which is removably mounted on the carrier body 2 is fed. When the half rotation cam 27 rotates in the reverse direction by 180 degrees, a correct ribbon lift frame 54 which is pivotally mounted on the carrier body 2 is pivoted upward and a correct ribbon 73 which is mounted on the correct ribbon lift frame 54 is fed.

A print unit 82 is also mounted in the carrier body 2. A mounting frame 83 of the print unit 82 is pivotally mounted on the left and right side plates 5 and 6 of the carrier body 2 by means of left and right shafts 84. A type wheel select motor 85 is fixed to the back of the mounting frame 83. A hammer actuator 86 is fixed to the upper part of the mounting frame 83 while a print hammer 87 is pivotally mounted on the latter. A type wheel rotating body 96 is connected to the type wheel select motor 85 by means of a gearing not shown and is supported on the mounting frame 83. Thus, if a type wheel cassette 101 containing a type wheel 102 therein is loaded in position at a front part of the carrier body 2, the type wheel 102 can be removably connected to the type wheel rotating body 96 so that it may be selectively rotated by the type wheel select motor 85 to select a character type thereon for printing.

Claims (1)

1. A carrier feed device for a printing machine comprising a carrier mounted for movement across the machine; a reversible drive motor mounted on said carrier; a capstan mounted on said carrier and connected to be rotated by said drive motor; a wire partially wound around said capstan; and means for securing opposite ends of said wire to stationary portions of the machine; whereby said carrier is fed as said capstan is driven to rotate by said drive motor.

2. A carrier feed device as claimed in claim 1, wherein said wire comprises a pair of segments each having one end secured to said capstan and wound, at a portion adjacent the one end thereof, in one or more turns around said capstan.

3. A carrier feed device as claimed in claim 1 or 2, wherein said means for securing said opposite ends of the wire is adjustable for permitting adjustment of the tension of said wire.

4. A carrier feed device as claimed in claim 1, 2 or 3, further comprising a fly-wheel connected to be driven by an output power shaft of said drive motor for smooth stepwise rotation of said drive motor and smooth stepwise feeding movement of said carrier.

5. A carrier feed device as claimed in claim 4, wherein said fly-wheel is secured directly to said output power shaft of said drive motor.

6. A carrier feed device according to any one of the preceding claims, wherein said drive motor is a stepping motor.

8. A carrier feed device substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

9. Any novel feature or combination of features disclosed herein.