JPH0419950B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a paper feeding device for a printing device such as an electronic typewriter, and more particularly to a device for moving a platen to feed paper by feeding a ratchet wheel via a cam. It is.

Configuration of Conventional Examples and Problems Therein In recent years, a large number of printing devices have appeared in which printing operations are electronically controlled. In these paper feeding devices as well, conventional mechanical parts are replaced with motors, electromagnetic solenoids, etc., and the operating means are controlled electronically. Since many motors, electromagnetic solenoids, control electric elements, etc. are more expensive than mechanical parts, it is necessary to devise ways to use them effectively.

A conventional paper feeding device will be described below.

A carriage on which a printing mechanism is placed performs a printing operation while reciprocating in parallel with a platen holding printing paper at an appropriate interval, and the platen is rotated every time one line of printing is completed to feed the paper.

In a conventional paper feeding device, the platen is rotated by rotating a cam using the driving force of a motor, which drives a pawl to feed a pawl wheel fixed to the platen shaft. The stroke of the pawl is set in advance to advance the ratchet wheel by two rows. Since the paper feed amount can generally be switched in three stages: 1, 11/2, and 2 lines, operate the paper feed amount switching lever to change the amount by which the pawl is run free so that the pawl does not engage with the ratchet wheel. As a result, paper feed amounts of 1, 11/2, and 2 lines are obtained.

As mentioned above, conventional paper feeding devices use powerful motors that are capable of feeding two lines per revolution of the cam, even though the normal usage is to feed paper one line at a time. There must be. As a result, the motor becomes large and the entire device becomes large and expensive.

Purpose of the Invention It is an object of the present invention to make a paper feed motor small and inexpensive, thereby making the entire device smaller, lighter, and cheaper, and to provide a paper feed device that can reliably and easily change the paper feed amount. It is to provide.

Structure of the Invention The paper feeding device of the present invention includes a platen, a ratchet wheel engaged with a rotating shaft of the platen, a motor, a cam rotated by the driving force of the motor, and a ratchet wheel driven by the cam. a pawl that engages to rotate the platen by a minimum paper feed amount for each rotation of the cam; a rotation detector that generates a rotation signal during rotation of the cam; A paper feed amount setting means for setting a feed amount, a paper feed amount setting signal set and generated by the paper feed amount setting means, a rotation signal from the rotation detector, and a paper feed operation command signal, and the motor is activated. The rotation detector includes a switch that turns ON and OFF once for each rotation of the cam, and the rotation signal is generated in accordance with ON and OFF of the switch, which causes the motor to rotate. This makes it possible to reduce the size of the apparatus and at the same time reduce the size of the entire apparatus, as well as to ensure and easily switch the paper feed amount.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of a paper feeding device according to an embodiment of the present invention. In Fig. 1, numeral 1 is a platen around which printing paper is wound and feeds the paper by rotating itself, numeral 2 is a cup-shaped type wheel with type arranged at the tips of many spokes, and numeral 3 is a hammer. Characters are printed by hitting the paper wound around the platen 1 from the back side of the spoke piece via a printing ribbon (not shown). FIG. 2 is a sectional view of a main part of the paper feeding device shown in FIG. 1. The explanation will be continued below with reference to FIGS. 1 and 2. 4 is a motor, a pinion gear 5, a gear 6,
7 and 8 form a gear train that meshes with each other in sequence, increasing and decelerating the driving force of the motor 4, and rotating the drive cam 9. 10 is a detection cam that rotates in synchronization with the drive cam 9; 11 is a leaf switch in which two leaf contact pieces 12 are provided with mutually opposing contacts (not shown); 12
moves up and down, the contacts of the switch 11 close and open, and the rotation of the drive cam 9 is detected. 13 and 14 are machine frames that hold the motor 4, the shafts of each gear, the bearing 16 of the platen shaft 15, and the leaf switch 11.

17 is a sleeve fixed to the platen shaft 15 by a set screw 18; 19 is a clutch that is guided by the sleeve 17 and slides in the direction of the platen axis; and 20 is an external toothed portion 19a of the clutch 19;
The ratchet wheel 21 is a washer that prevents the ratchet wheel 20 from coming off from the sleeve 17. 22
is the protrusion 2 that fits into the groove 17a of the sleeve 17.
2a and a boss portion 22b facing the protrusion 19b of the clutch 19.

Reference numeral 23 denotes a ratchet pawl to which the shaft 24 is pivotally attached and is biased by a torsion spring 25 so as to mesh with the ratchet wheel 20. Reference numeral 26 denotes a ratchet pawl for releasing the engagement after the ratchet 23 moves the ratchet wheel 20. 23, and the ratchet claw 2
3 is a pin that rotates counterclockwise when viewed from the platen knob 22 side; 27 is a cam follower of the drive cam 9; 28 is a ring member that fixes the shaft 24 and the cam follower 27 and is biased counterclockwise by a spring 29; 30 is a boss on which the ring member 28 is pivotally mounted and fixed to the platen shaft 15 by a set screw 31; 32 is a washer that prevents the ring member 28 from coming off from the boss 30; and 33 is a day tent that applies a day tent to the ratchet wheel 20. The lever 34 is a torsion spring that biases the detent lever 33 clockwise.

35 is the external toothed portion 19a of the clutch 19 and the ratchet wheel 20
This spring biases the clutch 19 so that the clutch 19 is always engaged with the internal teeth 20a of the clutch 19.

The operation of the paper feeding device of this embodiment configured as described above will be described below.

FIG. 1 shows a state in which paper feeding is started. The ring member 28 is biased by the spring 29, and the cam follower 2
7 is in contact with the position of the smallest radius of the drive cam 9. At this time, the leaf switch 11 is in a position where the leaf contact piece 12 is not pushed up by the detection cam 10, and the switch is in an OFF state. First, when a paper feed operation command signal is input from the printing device to a control means (not shown), the motor 4 starts rotating in the direction of arrow A, and the drive cam 9 starts rotating in the opposite direction to arrow A.

Fig. 3 is a cam displacement diagram in which the horizontal axis represents the rotation angle of the drive cam 9 and the rotational displacement amount of the cam follower 27 is shown on the vertical axis.
The rotation angle is , and the leaf switch 11 is turned on and off.
The characteristics are expressed on the vertical axis. The explanation will be continued with reference to FIGS. 3 and 4. As described above, the drive cam 9 begins to rotate and the cam follower 27 is pushed clockwise, and the ring member 28 similarly rotates around the platen shaft 15 against the force of the spring 29, and the ratchet pawl 23 is advanced. The arm portion 23a of the ratchet pawl 23 slides while contacting the pin 26, the ratchet pawl 23 rotates clockwise around the shaft 24, and the ratchet pawl 23 engages with the ratchet wheel 20 when the rotation angle of the drive cam 9 is around 90°. . At this time, the leaf contact piece 12 of the leaf switch 11 is pushed up by the detection cam 10 and the switch is turned ON, but the motor 4 continues to rotate and at a rotation angle of 180°,
The feed of the ratchet wheel 20 by one tooth is completed. The detent lever 33 climbs over the top of one tooth of the ratchet wheel 20 and settles on the trough of the next tooth, thereby preventing unnecessary rotation of the ratchet wheel 20. As the motor 4 continues to rotate further, the radius of the drive cam 9 begins to decrease, the cam follower 27 returns counterclockwise, and the ring member 2
8, the ratchet pawl 23 also returns to the initial position shown in FIG. When the drive cam 9 reaches a rotation angle of 270°, the ratchet pawl 23 completes its return, and the radius of the detection cam 10 that was pushing up the leaf contact piece 12 of the leaf switch 11 suddenly becomes smaller.
It becomes OFF. Since this leaf switch 11 is ON
A signal when switching to OFF is input to the control means. A slide switch (not shown) for selecting the paper feed amount provided on the keyboard of the printing device has one line.
It has 3 positions: 11/2 line and 2 line feed,
Assuming that one line feed is set from among these three positions, one tooth of the ratchet wheel 20 fed by the ratchet pawl 23 is provided for 1/2 line.
Two teeth will be sent.

The control means receives a paper feed amount setting signal of one line feed from the slide switch, counts two signals from the leaf switch 11, and stops supplying drive current to the motor 4 at the same time as counting the second signal. At this time, since the motor 4 continues to rotate due to inertia, the control means supplies a brake current to the motor 4 so that it stops when the rotation angle of the drive cam 9 changes from 270° to 360°. Similarly, when the slide switch is in the 11/2 row position, the control means counts three signals from the leaf switch and controls the motor 4 to advance the ratchet wheel 20 by three teeth. When the slide switch is in the 2nd row position, it can be easily inferred that the ratchet wheel 20 is moved by 4 teeth.

Next, the fine adjustment mechanism of the paper feeding device of this embodiment will be explained.

Normally, the spring 35 is connected to the external teeth 19a of the clutch 19.
Since the clutch 19 is biased so that the internal teeth 20a of the ratchet wheel 20 mesh with each other, when the ratchet wheel 20 is advanced, its rotation is transmitted to the clutch 19, and further transmitted to the sleeve 17, so that the sleeve 17 The platen shaft 15, which is engaged with the platen shaft 15, rotates and the paper is fed. Now, when manually finely feeding the paper, when the platen knob 22 is pushed, the boss part 22b pushes the protrusion 19b of the clutch 19, and the clutch 19 moves along the platen axis 15 in the sleeve 17 to release the spring 35.
It slides against the force of. Then, the engagement between the internal teeth 20a and the external teeth 19a is lost, and if the platen knob 22 is rotated in this state, the protrusion 2
The sleeve 17 rotates independently of the ratchet wheel 20 via 2a. Since the number of teeth of the internal toothed portion 20a and the external toothed portion 19a is considerably greater than the number of teeth of the ratchet wheel 20, the platen 1 can be rotated for fine adjustment.

As described above, according to this embodiment, one of the drive cams
By setting the paper feed amount to 1/2 line per rotation and arbitrarily obtaining a paper feed of an integer multiple of that, the motor power only needs to correspond to the minimum paper feed amount, making it possible to downsize the motor. The paper feeding device can be downsized. In addition, since the claw feed is performed by generating a rotation signal in response to one ON/OFF of the leaf switch 11 for each rotation of the drive cam 9, even if the rotation control accuracy of the drive cam 9 is poor, one You can feed the claws just by turning the leaf switch 11 ON and OFF.
The accuracy of the claw feed amount is increased.

In this embodiment, a leaf switch is used as the cam rotation detector, but a micro switch may also be used. The same function can also be obtained by blocking or opening a photodetector such as a photointerrupter using a detection cam. Furthermore, although the detection cam that synchronizes with the drive cam is provided separately, the rotation of the drive cam may be directly detected, or the reciprocating motion of the ring member may be detected.

Effects of the Invention As is clear from the above description, the paper feeding device of the present invention has a structure in which the platen is claw-fed by the minimum paper feed amount for each revolution of the cam, and the cam rotation detector and the minimum paper feed amount are detected by the cam rotation detector and the minimum paper feed amount. The motor is driven and controlled in response to a signal from the paper feed amount setting means that sets the paper feed amount in integer multiples, so the motor only needs to have the ability to feed at least the minimum paper feed amount, making it compact and light in drive power. A small motor is sufficient, and the excellent effect of making the device smaller and lighter can be obtained.

Furthermore, the claw feed amount can be adjusted by turning on one switch.
Since it depends only on OFF, it is possible to set an arbitrary paper feed amount with a simple configuration, and the accuracy of the claw feed amount can be increased regardless of the accuracy of rotation control for each rotation of the cam.

Furthermore, when feeding 1 line or 11/2 lines, in the conventional configuration, the ratchet pawl runs idle for 1/2 line or 1 line, which wastes electric power on the motor. According to the paper feeding device, in order to supply power to the motor for the required amount of paper feeding,
Power saving becomes possible.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a partially cutaway essential part of a paper feeding device according to an embodiment of the present invention, FIG. 2 is a side sectional view of the essential part of FIG. 1, and FIG. A cam displacement diagram for explanation, FIG. 4 is a characteristic diagram of a cam rotation detection switch similar to FIG. 3. 1...Platen, 4...Motor, 5...Pinion gear, 9...Drive cam, 10...Detection cam, 1
1... Leaf switch, 15... Platen shaft, 1
7... Sleeve, 19... Clutch, 20... Ratchet wheel, 22... Platen knob, 23... Ratchet pawl, 26... Pin, 27... Cam follower, 28
...Ring member, 30...Boss, 33...Detent lever, 35...Spring.

Claims (1)

[Claims] 1 a platen, a ratchet wheel locked to the rotating shaft of the platen, a motor, a cam that rotates by the driving force of the motor, and a cam that is driven by the cam and engages with the ratchet wheel for each rotation of the cam. a pawl that rotates the platen by a minimum paper feed amount, and one of the cams.
a switch that turns on and off once for each rotation; a rotation detector that generates a rotation signal corresponding to a predetermined paper feed amount when the switch is turned on and off once;
a paper feed amount setting means for setting a paper feed amount that is an integral multiple of the minimum paper feed amount; and control means for driving and controlling the motor until the paper feed amount thus determined matches the paper feed amount set by the paper feed amount setting means.