JPS593889Y2 - type selection mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a type selection mechanism, and more particularly to a type selection mechanism whose drive shaft can be continuously rotated.

In general, the printing mechanism of a small serial printer used for desktop calculators, etc. has a type wheel that has many types around it and can move in the line direction, and rotates the type wheel to place the desired type at the printing position. It has a character selection mechanism for positioning, a printing hammer that has a length of one line and is swingably supported, and a plunger mechanism that drives the hammer.

First, the type ring is positioned at the lowest digit, and when the desired type is positioned at the printing position, the recording paper inserted between the print mark and the ink-applied type is placed on the type. Press it to print the least significant digit.

Thereafter, the type wheel is moved to the next printing digit and the above-described printing operation is repeated, and thereafter, the same operation is performed to print up to the most significant digit, thus completing the printing of one line.

In the case of serial printers, when the recording paper is pressed against the type by a hammer, it is better to keep the type wheel stationary to avoid cast and uneven character arrangement, resulting in better print quality, and /'% This makes it easier to control the timing of driving the timer.

By the way, in conventional serial printers, the type wheel is directly connected to the shaft of a stepping motor or the like, and the motor is rotated to select the type, so the motor is started, rotated, and stopped for each character printed. I had to have it.

For this reason, it takes a considerable amount of time to start and stop the motor, making high-speed printing difficult, and furthermore, the motor control circuit is complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a type selection mechanism that can keep the drive motor for rotating the type wheel rotating at all times without stopping it, and that has a simple configuration.

Embodiments of the present invention will be described in detail below with reference to the drawings.

Figure 1 is a cross-sectional front view of the type selection mechanism according to the present invention;
The figure is an exploded perspective view of the type selection mechanism according to the present invention, and FIG. 3 is an explanatory diagram of the ratchet stop mechanism.

In the figure, reference numeral 1 denotes a drive gear, which rotates by being driven by a gear (not shown) connected to a motor, and includes a flat plate part 1b having teeth 1a on the outer periphery, and a stepped boss part 1C formed at the center of the flat plate part. A through hole 1d is provided through the flat plate portion 1b and the boss portion 1C.

Reference numeral 2 denotes a ratchet for character selection, and a large number of pawls 2a are formed on a portion of the side surface.

Note that the claws 2a may be provided on the entire surface.

3 is a driven member, which is a body portion 3b provided with a through hole 3a.
, 3b' and the collar part 3C.

4 is a rotating shaft, the drive gear 1 is fitted into the rotating shaft 4 freely, in other words, rotatably, and the driven member 3
is press-fitted and fixed to the rotating shaft.

Reference numeral 5 designates a known spring clutch, in which the boss IC of the drive gear 1 is connected to the boss IC of the drive gear 1 from one side, and the body 3 of the driven member 3 is connected to the other side.
b are respectively inserted, and one end 5a of the spring clutch is secured in a groove 2b provided on the inner periphery of the ratchet 2.

When the drive gear 1 rotates, the spring clutch 5 tightens the boss portion 1C of the drive gear 1 and the body portion 3b of the driven member 3, respectively.

Reference numeral 6 denotes a bearing, which is freely inserted into the rotating shaft 4.

Reference numeral 7 denotes a side plate (support plate) into which the foot portion 6a of the bearing 6 is inserted and held.

Reference numeral 8 designates a spring clutch for preventing reversal, into which the foot 6a of the bearing 6 is inserted from one side, and the body 3b' of the driven member 3 from the other. engage.

Reference numeral 9 denotes a type ring, which is slidably slidable on the rotary shaft 4 and spline-coupled to rotate integrally with the shaft 4;
A large number of printed characters 9a, 9b, . . . 91 are supported on the circumferential side surface.

Reference numeral 10 (see FIG. 3) is an electromagnet for character selection, which attracts the lever 11 by being excited, and engages the tip of the lever 11 with the pawl 2a of the ratchet 2.

Reference numeral 12 denotes a spring which is used to excite and disconnect the electromagnet 10, and the lever 11
to be reinstated.

Next, the assembly of the type selection mechanism of the present invention and the type selection operation will be explained.

The driven member 3 is press-fitted and fixed in advance at a predetermined position on the rotating shaft 4.

Then, first, connect the spring clutches 5 and 8, respectively.
Insert into the body parts 3b, 3b' of the driven member 3.

Next, the bearing 6 with the side plate 7 fitted into the foot 6a is inserted into the rotating shaft 4, and the foot 6a is connected to the spring clutch 8.
, and one end 8a of the spring clutch 8 is engaged with the groove 7a of the side plate 7.

After that, the ratchet 2 is inserted from the right side, and the one end 5a of the spring clutch 5 is secured in the groove 2b of the ratchet 2.

Finally, by inserting the drive gear 1, the type selection mechanism shown in FIG. 1 is completed.

The selection of printed characters by this printed character selection mechanism is performed as follows.

When a print command is generated, a motor (not shown) is started, and thereafter the motor rotates at a constant rotational speed until a print end signal is generated.

When the motor rotates, the drive gear 1 also starts rotating.

Now, since the spring clutch 5 is wound in the direction of winding against the rotation of the drive gear 1, when the drive gear 1 rotates, it tightens the boss portion IC and the body portion 3b.

On the other hand, one end 5a of the spring clutch 5 is connected to the ratchet 2.
Since the spring clutch 5 is engaged with the groove 2b, when the spring clutch 5 rotates while tightening the boss portion 1C and the body portion 3b, the driven member 3 and the ratchet 2 rotate.

Since the driven member 3 is fixed to the rotating shaft 4, the rotating shaft 4 also rotates together with the driven member 3.

Incidentally, although not shown, a rotary encoder such as a slit disk is attached to the rotating shaft 4.

For example, a slit for the home position and a slit for indicating the position of the printed characters are formed on the outer periphery of the slit disk.

Therefore, if print position information (information indicating the number of print characters from the home position) of the characters to be printed is commanded from a controller (not shown), it is easy to detect and count the slits from the home position with a detector. The type commanded by can be positioned at the printing position.

At the same time as the commanded type is positioned at the printing position,
The electromagnet 10 (see FIG. 3) is energized, which attracts the lever 11, causing the tip of the lever 11 to engage the ratchet 2.
engages with the claw 2a.

When the tip of the lever engages with the pawl 2a, the rotation of the ratchet 2 is blocked and the ratchet 2 stops its rotation.

On the other hand, if the rotation of the ratchet 2 is prevented, the tightening of the spring clutch to the boss IC and the body 3b is immediately loosened, the connection between the driven member 3 and the driving gear 1 is immediately released, and from then on, the electromagnet 10 The rotation of the drive gear 1 is not transmitted to the driven member 3 until the excitation of the drive gear 1 is cut off.

As a result, the rotating shaft 4 also stops together with the driven member 3, a desired type is selected, and the type wheel 9 becomes stationary.

While the type wheel 9 is in a stationary state, a printing operation (hammering) is performed, and then the excitation of the electromagnet 10 is turned off.

After the carrying operation of the type wheel 9, the same operation is repeated to complete the printing of - lines.

Note that the spring clutch 8 operates to prevent the rotating shaft 4 from reversing.

This is because when the spring clutch 5 is loosened, a force in the reverse direction is generated, causing the driven member 3 to rotate slightly in the reverse direction, which deteriorates the positioning accuracy of the type.

However, by arranging the spring clutch 8 so that its one end 8a engages with the groove 7a of the side plate 7, reverse rotation of the driven member 3 due to the above reversal force is prevented.

As described above, according to the present invention, the drive unit consisting of a drive gear etc. can be kept rotating at all times, so there is no need to start and stop the motor every time one character is printed, allowing for high-speed character selection and high-speed printing. Control becomes easier.

Further, a complicated motor control circuit is not required, which is advantageous in terms of cost.

Furthermore, power is transmitted between the drive side and the printing wheel side by providing a drive gear, a spring clutch, and a driven member.
In addition, the transmission system is disconnected when selecting type by simply stopping the ratchet by providing a ratchet, which makes it possible to provide a small and lightweight printer with a small number of parts.

[Brief explanation of drawings]

Figure 1 is a cross-sectional front view of the type selection mechanism according to the present invention;
The figure is an exploded perspective view of the type selection mechanism, and FIG. 3 is an explanatory diagram of the ratchet stop mechanism. 1... Drive gear, 1a... Teeth, 1C... Boss part,
2...Ratchet, 2a...Claw, 2b...Groove, 3
... Driven member, 3b, 3b' ... Body part, 4 ... Rotating shaft, 5, 8 ... Spring clutch, 6 ... Bearing, 7 ... Side plate, 9 ... Type wheel , 10... Electromagnet, 11... Lever

Claims (1)

[Scope of utility model registration request] In the type selection mechanism of a printer that selects a predetermined type by rotating a type wheel that rotates integrally with the rotary shaft and supports a large number of type on its circumferential side, the type selection mechanism of a printer that prints by rotating a type wheel that rotates integrally with a rotating shaft and supports a large number of type on its circumferential side surface, is constantly rotated by a motor or the like and a boss portion is rotated. a drive gear that is free with respect to the rotating shaft; a driven member that is fixed to the rotating shaft; and a ratchet that is freely provided with respect to the driven member; the boss portion is inserted from one side, and the driven gear is inserted from the other side. A spring clutch, into which the member is inserted, is engaged with the ratchet and transmits the rotation of the drive gear to the driven member and the ratchet, and a lever that stops the rotation of the ratchet, by stopping the rotation of the ratchet. A type selection mechanism characterized in that a predetermined type is selected by loosening the tightening of the spring clutch and releasing the connection between the driving gear and the driven member.