JPH0367034B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a small-sized serial printer, and more particularly to a small-sized serial printer configured to prevent printed characters from protruding from a printing hammer and smearing printing paper when a carriage is lowered.

Conventional serial printing printers place the type drum horizontally relative to the printing paper, that is, with the rotation axis horizontal, and the rotational movement of the type drum,
Serial printing was performed using stop, impact, and carry operations.

However, this type of conventional printer requires an expensive pulse motor to drive and control the type drum and perform printing operations, or a complicated clutch mechanism to transmit intermittent power, making it likely to be expensive overall. There were flaws.

Therefore, in order to improve this drawback, a small serial printer is equipped with a type drum that rotates around an axis perpendicular to the digit direction of the printing paper, and a carriage that transports this type drum in the direction of the printing digit. was suggested.

In conventional small serial printers of this type, the printing hammer operates when the carriage returns to the home position and prints, so when the carriage returns, the type comes into contact with the printing paper, causing the printing paper to The problem was that it got dirty.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional printer, and an object of the present invention is to provide a small-sized serial printer configured to eliminate contact between type and printing paper when the carriage is returned, and to prevent the printing paper from becoming dirty. It is an object.

In order to achieve the above object, the present invention provides a cam plate along the reciprocating path of the carriage, and the carriage has a printing hammer with one end facing inside the type drum and the other end facing the cam plate side. The printing hammer has a structure in which a claw is provided at one end of the printing hammer to prevent it from engaging with the cam plate when lowering the carriage.

Hereinafter, details of the present invention will be explained based on embodiments shown in the drawings.

FIG. 1 and subsequent figures explain one embodiment of the present invention, and FIG. 1 shows the overall configuration.

The small printer according to the present invention is assembled using a frame 1 as a base. At one end of the frame 1, a motor 2, a solenoid 3 that serves as a trigger when driving a control mechanism to be described later, and a tachogenerator 4 for detecting a TP signal are attached.

An output shaft 2a of the motor 2 extends outward beyond the left side plate 1a of the frame 1, and a pinion gear 5 is fixed to the tip thereof. Further, a rotary shaft 6 is rotatably supported on the side plate 1a parallel to the output shaft 2a, and an intermediate gear 8 is rotatably mounted on a shaft (not shown) between the rotary shaft 6 and a gear 7 fixed to the outer end thereof. The pinion gear 5 and the gear 7 are
The rotation of the motor 2 is transmitted to the rotation shaft 6 by meshing with the shaft 6.

As shown in FIG. 2, a worm gear 9 and a tacho-generator magnet 10 for detecting a TP signal are fixed to the rotating shaft 6, and the worm gear 9 is always in mesh with a drum gear 11, which will be described later.

As shown in FIG. 3, the drum gear 11 is provided on the lower surface of the carriage 14 guided by guide shafts 12 and 13.
A TR drum 15 for detecting TR signals is integrally equipped.

Additionally, a drum base 1 is mounted on the upper side of the carriage 14.
6 is located and an integrally formed shaft 16a
via the above drum gear 11 and TR drum 1
5 is integrated and rotatably supported on the carriage 14.

A type belt 17 for numbers is wrapped around the drum base 16 on the upper side, and a type belt 18 for symbols is wound on the lower side.Protrusions 17 are formed on the back side of each type.
a, 18a pass through a through hole made in the drum base 16 and are fitted inside the drum base 16.

As shown in FIG. 1, a hammer 19 for symbol printing located on the upper side and a hammer 20 for printing numbers located on the lower side are arranged on the carriage 14 in the direction of the upper digits of the drum base 16. It is rotatably supported within a certain angular range via a shaft 14f extending upwardly.

The symbol printing hammer 19 is fitted into the drum base 16 by bending one arm 19a as shown in FIG. It can be installed freely.

The tip of the other arm 19b is attached to a vertical portion 22 of a cam plate 22 disposed along the reciprocating path of the carriage.
a is located at a position where it can engage with a protrusion 22b protruding from the inside of the base.

An arm 20a of the number printing hammer 20 extending above the drum base 16 has a roller 2 on the lower surface of its tip.
3 is rotatably supported via a shaft 24,
It faces the numeric type belt 17 in the drum base 16. The other arm 20b has a claw 25 at its tip, which is rotatably supported within a predetermined angle θ as shown in FIG. 4, and engages with a protrusion 22c located below the protrusion 22b. I am in a position to gain.

Note that the protrusions 22b and 22c have a triangular cross section, and are configured such that the tips of the arms 19b and 20b ride on them both when the carriage 14 is moved up and back.

On the outer edge of the horizontal portion 22d of the cam plate 22, a plurality of triangular protrusions 22e as shown in FIG. 5 are formed in a sawtooth shape. As shown in FIG. 6, the tips of elastic pawls 14a protruding from one end of the carriage 14 are engaged with these protrusions 22e.

Further, as shown in FIG. 7, the cam surface 22 is supported on the rotary shaft 6 via a bracket 22f protruding from the lower end, and is provided so as to be able to freely rotate within a certain angle range, and is supported by a spring. By S.
In FIG. 1, a clockwise rotational habit is given.

On the other hand, the reference numeral 26 indicates an ink roller case in which an ink roller 28 is rotatably supported via a shaft 27. This ink roller case 2
6 has an elastic claw 26a, and the carriage 14
It is removably engaged with a protrusion 14b protruding from. The carriage 14 has an ink roller case 26
A spring 29 is tensioned at the mounting portion of the ink roller case 26, and this spring 29 holds the ink roller case 26 so that it does not slip out.
An ink roller 28 is pressed against the type belt 18 for type and symbols to apply ink.

One end of a carriage return spring 30 is connected to one end of the carriage 14, and the other end of the spring 30 is attached to an arc-shaped guide 31 protruding from the side surface of the right side plate 1b in FIG. 39 and is fixed to the left side plate 1a, so that the carriage 14 is always pulled in the direction of the side plate 1b. However, the sixth
As shown in the figure, when the claw 14a of the carriage is engaged with the protrusion 22e of the cam plate 22, the movement of the carriage 14 is restricted.

On the other hand, as shown in FIG. 6, a drive gear 32 is meshed with the drum gear 11, and the drive gear 32 is connected to a shaft 14d extending downward from the carriage 14.
It is rotatably supported on the shaft. A control lever 33 is attached to the shaft 14d below the drive gear 32.
is rotatably supported on a shaft, and a spring (not shown) gives it the ability to rotate clockwise in FIG.

The free end 33a of the control lever 33 faces a position where it can engage with a rack tooth 34a of a rack plate 34 arranged parallel to the cam plate 22 along the reciprocating path of the carriage 14.

Further, as shown in FIG. 6, the drum gear 11 can also engage with the rack teeth 34a, and the rack plate 3
4 can freely rotate one end in the width direction within a certain angular range via a shaft 35 as shown in FIG. 9 with respect to the side plate 1b.

The rack plate 34 has a shaft 34b on the opposite side from the shaft 35 and protruding outside the side plate 1b of the frame, and one end of a lever 36 is rotatably connected to this shaft 34b. The lever 36 is rotatably supported on the side plate 1b via a shaft 36c in the middle thereof, and has a protrusion 3 extending upward near the other end.
6a is formed, the protrusion 36a being in contact with the free end 37a of the armature 37 of the solenoid 3. A spring 38 is also provided between the end of the lever 36 opposite to the shaft 34b and the upper end of the side plate 1b.
is stretched, and the rack plate 34 is given the habit of rotating clockwise in FIG.

On the other hand, a paper guide 40 is provided between the carriage 14 and the platen 39 facing the type drum, and the printing paper P is guided therethrough. A clutch gear 41 is provided on the lower surface of the side plate 1b of the platen 39 in FIG. 1 at a position where it can mesh with the drive gear 32.

As shown in FIGS. 1A and 1B, the clutch gear 41 is a boss 43a of a PF (paper feed) worm 43 rotatably supported on a shaft 42.
Although it is rotatably fitted in and can move freely in the sliding direction, it is subject to restrictions in the radial direction as described below.

The clutch gear 41 is given the habit of always moving upward by a spring 44 loaded between it and a spring receiver 42a at the lower end of the shaft 42. As shown in FIG. 16, a gently sloping cam surface 41a is formed on the upper surface of the clutch gear 41, with one end being high and the other end being low, and a ratchet 41b for preventing reverse rotation, which will be described later, is formed. There is.

Further, a PF lever 46 is rotatably supported near the clutch gear 41 via a shaft 45.
One end 46b thereof is given a rotational habit by a spring (not shown) in a direction in which it comes into contact with the cam surface 41a.

On the other hand, the worm part 43b of the PF worm 43 meshes with a PF gear 47 formed as a crown gear as shown in FIG. has been done. A pinch roller 50 is in contact with the rubber roller 48, pinching the printing paper P, and the printing paper P is sent out.

By the way, in FIG. 1, a leaf spring 51 is fixed to the right side plate 1b, and its bent free ends 51a and 51b are respectively protruded from the end of the cam plate 22 as shown in FIG. Protrusion 22g, 2
It is in a position where it can be engaged with 2h.

Incidentally, as shown in FIG. 18, conductive films 52a to 52c are provided on the outer peripheral surface of the TR drum 15, which is integrated with the drum base 16, separated at predetermined intervals. , a brush 53a whose one end is fixed to the carriage 14 side,
53b are in contact with each other in a sandwiching manner.

A voltage is applied to the brushes 53a, 53b from the carriage side, and as the TR drum 15 rotates, each brush 53a, 53b is applied once per rotation.
b contact the same film 52a at the same time and detect the TR signal.

Next, the operation of the printer according to the present invention constructed as above will be explained with reference to the timing chart shown in FIG. 21.

First, when the switch is turned on and the motor rotates, the rotation is caused by pinion gear 5, intermediate gear 8,
7 is transmitted to the drum gear 11 via the rotating shaft 6 and the worm gear 9, and the drum base 16, which is integrated with the drum gear 11, is continuously rotated clockwise in FIG.

When the drum gear 11 rotates, the TR drum 15 integrated therewith also rotates, and a TR signal is output.

In addition, the magnet 1 attached to the rotating shaft 6
0 rotation causes the tachogenerator 4 to output a TR signal.

When a printing command is issued by the control circuit based on these signals, the solenoid 3 is turned on, and the tip 37a of the armature 37 is brought into contact with the protrusion 36 of the lever 36.
a, the rack plate 34 is rotated clockwise in FIG. 9 about the shaft 35, and the rack teeth 34
The a side rises.

As a result, the rack teeth 34a and the drum gear 11 mesh with each other, and the free end 33a of the control lever 33 is positioned below the rack teeth 34a. That is, the relationship between the free end 33a of the control lever 33 and the lock tooth 34a changes from the state shown in FIG. 12A to the state shown in FIG. 12B. Here, even if the power to the solenoid 3 is cut off, the rack teeth 34a are in contact with the free end side 33a of the control lever 33, so the rack plate 34 cannot return to the horizontal state, and the rack teeth 34a and the drum gear 11 are in mesh with each other. Continue.

Therefore, the rack plate 34 in a fixed state causes the drum gear 11 to move forward, the carriage 14 to move forward, and the drum base 16 to rotate, thereby performing a carrying movement.

Of course, at this time, the printing hammers 19 and 20 also move at the same time, and when printing the first digit, the cam plate 2
Of the symbol printing protrusions 22b arranged above the vertical portion 22a of No. 2, the left protrusion 22b shown in FIG.
Only the tip of the arm 19b of the symbol printing hammer 19 is engaged, and as shown in FIG.
9 is rotated counterclockwise, and the roller 21 attached to one arm 19a pushes the protrusion 18a on the back side of the symbol type belt 18, so that the selected type flies out toward the printing paper P and is attached to the platen. 39
Printing is performed by pressing the

When the tip of the arm 19b of the symbol printing hammer 19 passes over the protrusion 22b, the roller 21 separates from the protrusion 18a of the symbol type belt 18, and printing is completed.

However, the drum gear 11 still has the lock teeth 34a.
The carriage 14 is in the middle of being carried up.

As the carry of the carriage 14 progresses, when the tip of the control lever 33 reaches the position shown in FIG. 12C, the rack teeth 34a come into contact with the stepped portion of the free end 33a, as shown in FIGS. 12D to F. The rack teeth 34a and the drum gear 11 are disengaged, the lock teeth 34a and the free end 33a of the control lever 33 are engaged, and the carriage 14 no longer moves forward.

Here, if the carry speed is fast, the carriage 14
Due to the inertia of the carriage 14, the carriage 14 tries to move forward, but the tip 33a of the control lever 33, which moves together with the carriage 14, hits the next rack tooth 34a and restricts the movement of the carriage 14.

Furthermore, the carriage 14 attempts to be returned to the home position by the return spring 30;
As shown in FIG. 6, the tip of the claw 14a of the carriage 14 engages with the protrusion 22e of the cam plate 22 and stops at that position. At this time, the free end 33a and the lock teeth 34a of the control lever 33 are in the state shown in FIG. 12F.

That is, the control lever 33 maintains the engagement between the rack teeth 34a and the drum gear 11 during carry-up, and
Make sure to carry up one digit, and move the carriage 1.
It has a function to prevent overrun of 4.

Next, the second digit print signal causes solenoid 3 to
When energized, the carriage 14 starts to carry as described above, and the right-hand protrusion 22b of the upper protrusion 22b of the cam plate 22 and the arm 19b of the symbol printing hammer 19 shown in FIG. The tips engage and print the symbol again.

In addition, in the case shown in Figure 21, "985CN"
An example of printing is shown. When the printing of the second digit symbol is completed, the paper is fed as described later, and the printing paper is lifted to the same position as the number belt. Then, when the solenoid 3 is energized by the third digit print signal, the carriage 14 is activated as described above.
starts carrying, and the leftmost protrusion 22c and the arm 20 of the number printing hammer 20 among the protrusions 22c lined up at the lower end of the vertical part 22a of the cam plate 22 shown in FIG.
The claw 25 attached to the tip of b engages. Claw 25
Since rotation in the counterclockwise direction in FIG. 17 is restricted when the carriage is moved up, the hammer 20 is rotated in the counterclockwise direction in FIG. Roller 2
3, the number type belt 17 is pushed and the selected number is printed.

After that, finish printing all the numeric digits in the same way,
When the carriage 14 reaches the highest digit, the shoulder of the claw 14a of the carriage 14 engages with the protrusion 22i formed at the base of the cam plate 22, as shown in FIG. as shown by the solid line in the direction away from the carriage 14.

As a result, the protrusions 22g and 22h of the cam plate 22, which had not been engaged with the bent portions of the free ends 51a and 51b of the leaf spring 51 as shown in FIG. 15A, are removed as shown in FIGS. 15B to C. As such, the free ends 51a, 5
1b begins to engage. As a result, the cam plate 22 is held in that position. This is the state shown in FIG. 15C.

In this state, the claw 14a of the carriage 14
Then, the cam plate 22 is disengaged from the protrusion 22e, and the carriage 14 is pulled back to the home position by the tensile force of the return spring 30.

At this time, the spring force pressing the free end 33a of the control lever 33 against the rack plate 34 is
Since the force of the return spring 30 is greater, the control lever 33 is moved counterclockwise in FIG.
a, and does not prevent the carriage 14 from returning to its home position.

Incidentally, when the carriage 14 returns, the claw 25 attached to the tip of the arm 20b of the number printing hammer 20 may engage with the protrusion 22c of the cam plate 22, but the claw 25 does not fit in the predetermined position as shown in FIG. Since it can be rotated clockwise in FIG. 4 at intervals of angle θ, the number printing hammer 20 is not rotated and no printing is performed.

Note that when the claw 25 is rotated, the protrusion 22
c and will not stain the printing paper until it returns to the home position.

On the other hand, as shown in FIG. Since the setting is such that the arm 19b does not come into contact with the paper, no symbols are printed and the paper is not soiled.

When the carriage 14 returns to the home position,
As shown in FIG. 15D, the protrusion 14e of the carriage 14 hits both free end sides 51a and 51b of the leaf spring 51, and the protrusions 22g and 22h of the cam plate 22 disengage from the bent portion of the leaf spring 51. The cam plate 22 is returned to its original state by a spring (not shown). Then, before printing of the next line begins, paper feeding is performed as described later, and all printing cycles for one line are completed.

Next, the paper feeding operation will be explained.

As shown in FIG. 2, the protrusion 14e provided on the carriage 14 during carry-up for printing the second digit symbol as described above pushes against one end 46a of the PF lever 46.
and is disengaged when the carriage 14 stops at a predetermined position.

At this time, the PF lever 4 engaged with the protrusion 14e
6 is rotated clockwise as shown by the chain line in FIG. 2, and its one end 46b is disengaged from the cam portion 41a.

As a result, as shown in FIG. 10B, the clutch gear 41, which had been pushed up against the force of the spring 44, is pushed up by the spring 44, and the first
As shown in FIG. 0A, the clutch gear 41 and drive gear 32 mesh with each other, and the clutch gear
starts rotating.

When clutch gear 41 started rotating, it returned to normal.
Since one end 46b of the PF lever 46 rides on the cam portion 41a, it is gradually pushed down and disengages from the drive gear 32, as shown in FIG. 10B.

During this time, the PF worm 43 meshing with the clutch gear 41 also rotates in the same direction, causing the PF gear 47 meshing with it to rotate, and the rubber roller 48 to rotate via the shaft 49. As a result, rubber roller 4
8 and the pinch roller 50, the printing paper P is fed half a pitch.

In this way, the printed symbol is raised to the same level as the next printed number, so that the number can be printed on the same line as the symbol. This eliminates the need for vertical movement of a drum or platen during printing, as seen in typewriters.

Note that when the paper feeding is finished and the drive gear 32 and the clutch gear 41 are separated, the PF lever 46 is moved to prevent the clutch gear 41 from moving upward while being reversed by the clutch spring 44.
The tip of the arm 46b engages with the ratchet 46c,
Prevents reversal.

Further, when the carriage 14 finishes printing the most significant digit and returns to the home position, the remaining half-pitch paper feed is performed in the same manner.

By the way, if printing is not performed over all digits and the carriage 14 is returned halfway, a slightly different operation is required.

That is, as shown in FIG. 17, in this case, the projection 16c protruding from the inner surface of the drum base 16
On the other hand, when the printing operation is performed as described above, the roller 23 of the hammer 20 hits the protrusion 16c, preventing the hammer from rotating.Contrary to what was described above, the hammer 20 does not move and the carriage 14 advances. , the cam plate 22 falls to the left in FIG.
The state shown in FIG. 5C is reached, the carriage 14 returns to the home position, and the printing cycle when all digits are not printed is completed.

In addition, when printing a symbol in the first and second digits when only paper feeding is performed without performing a printing operation, as shown in FIG.
After performing a printing operation on the inner part of the protrusion 18a on the back side of the number 8, and performing a half-pitch paper feeding operation, when the third digit, that is, the first digit of the number, the inner part of the drum base 16 is printed. A printing operation is performed on the protrusion 16c, the carriage 14 is returned to the home position in the same manner as described above, and the paper is fed the remaining half-pitch, making a total of one pitch.

By the way, when the printer of the present invention is installed in a calculator or the like, when the calculator is turned on, no matter which digit the carriage 14 is stopped at,
First, the drum base 1 is activated by the TR signal and TP signal.
A printing operation is performed on the protrusion 16c provided inside the printer 6, and the carriage 14 returns to the home position, and a reset operation is performed for the next printing.

When the carriage is stopped at the 0th and 1st digits, which are the home positions, the protrusion 22 of the cam plate 22 is one of the means for returning the carriage 14.
g and 22h and the free ends 51a and 51 of the leaf spring 51
The engagement of b is slightly different.

That is, the protrusion 22g of the cam plate 22 and the leaf spring 5
Since the protrusion 22b is set so that the arm 19b of the symbol printing hammer 19 does not engage with the protrusion 22b of the cam plate 22 when the free end 51a of the symbol printing hammer 19 engages with the free end 51a of the symbol printing hammer 19. When the tip of the cam plate 22 is moved back by the protrusion 22b of the cam plate 22, the protrusion 22h of the cam plate 22 and the bent portion of the free end 51b of the leaf spring 51 are engaged, as shown in FIG. 15B. The carriage 14 is then returned.

In this case, the tip of the arm 19b of the symbol printing hammer 19 may engage with the protrusion 22b;
When the carriage 14 returns from a position close to the home position, the force of the return spring 30 is weak and the return speed of the carriage 14 is slow, so that the printing paper is not stained.

Further, the protrusion 22c of the cam plate 22 that can engage with the claw 25 of the number printing hammer 20 is not located near the home position, so that it does not stain the printing paper.

Incidentally, the arm 19b of the symbol printing hammer 19 is not provided with anything in the above-described embodiment, but as shown in FIG. A protrusion 22j may be provided at one end of the plate 22 to engage with the claw 54 when the claw 54 is rotated to the state shown by the chain line.

Unlike the embodiments described above, if such a structure is adopted, even if the carriage is returned from a state where it is stopped at the 0th and 1st digits,
Unlike the embodiments described above, the tip of the arm 19b and the protrusion 22b do not engage with each other.

When the carriage 14 returns to the home position and raises the cam plate 22, the protrusion 22j engages with the pawl 54, and the pawl 54 returns to its normal state.

Note that it is also possible to provide only the conductive film 52a on the TR drum 15, as shown in FIG. 20. In this case, although abrasion powder is generated in the insulating portion, insulation failure due to abrasion in the conductive portion does not occur.

Since this embodiment is configured as described above,
Compared to printers that perform type selection, printing, and carry separately, this printer performs printing and carry at the same time.
A printer capable of high-speed printing with little time loss can be obtained.

In addition, printing is performed by rotating a hammer using a protrusion on the cam plate and rolling the characters while pressing them against the printing paper, resulting in a quiet printer with almost no printing noise.

Furthermore, when the carriage is returned, it is operated using only the force of the return spring, and the solenoid only needs to be energized when a print command is issued, so there is no energy loss, low power consumption, and an inexpensive free-run motor can be used as a motor, making it compact. You can get a cheap printer.

As is clear from the above description, according to the present invention, a cam plate is provided along the reciprocating path of the carriage,
The carriage is equipped with a printing hammer with one end facing inside the type drum and the other end facing the cam plate, and one end of the printing hammer has a claw that prevents it from engaging with the cam plate when the carriage is lowered. Because of this, there is no printing operation by the printing hammer when the carriage is lowered, which has the excellent effect of not staining the printing paper.

[Brief explanation of drawings]

The figure explains one embodiment of the present invention.
The figure is a perspective view explaining the overall structure, Figure 2 is an explanatory diagram showing part of the power transmission mechanism, Figure 3 is a longitudinal side view explaining the structure of the drum, and Figure 4 is a hammer attached to a number printing hammer. An explanatory diagram of the pawl, Fig. 5 is a partially enlarged perspective view of the cam plate, Fig. 6 is a plan view showing the carriage drive control mechanism, Fig. 7 is a side view of the cam plate, and Fig. 8 is the installation of the ink roller. FIG. 9 is an explanatory diagram showing the carrying operation by the rack plate, FIGS. 10A and B are longitudinal side views illustrating the operation of the clutch gear, and FIG. 11 is an explanatory diagram showing the paper feeding mechanism. , FIGS. 12A to 12F are explanatory diagrams of the operation of the control lever showing the carriage carry-up operation, FIG. 13 is a plan view showing the operation of the symbol printing hammer, and FIG. 14 is a plane view showing the carriage return operation. Figure, No. 15
Figures A to D are explanatory diagrams showing the engagement operation between the cam plate and the leaf spring, Figure 16 is a perspective view showing the engagement relationship between the clutch gear and the PF lever, and Figure 17 is for printing numbers during digit return operation. A plan view showing the operation of the hammer,
Fig. 18 is an explanatory diagram of the TR signal detection mechanism, Fig. 19 is an explanatory diagram showing another structural example of the symbol printing hammer,
FIG. 20 is an explanatory diagram showing another example of the TR signal detection mechanism, and FIG. 21 is a timing chart. 1...Frame, 2...Motor, 3...Solenoid,
4...Tachometer generator, 6...Rotating shaft, 9...Worm gear, 10...Magnet, 11...Drum gear,
14... Carriage, 15... TR drum, 16... Drum base, 17... Type belt for numbers, 18... Type belt for symbols, 19... Hammer for symbol printing, 20...
Hammer for number printing, 21, 23...Roller, 22...
Cam plate, 25...claw, 26...ink roller case,
28... Ink roller, 30... Return spring, 3
2... Drive gear, 33... Control lever, 34... Rack plate, 34a... Rack tooth, 36... Lever, 37
... Armature, 39... Platen, 41... Clutch gear, 43... Worm section, 46... PF lever,
47...PF gear, 48...rubber roller, 51...plate spring, 51a, 51b...free end, 52a-52c...
Conductive film, 53a-53b...Brush.

Claims (1)

[Claims] 1. In a small serial printer equipped with a type drum that rotates around an axis perpendicular to the digit direction of printing paper and a carriage that conveys this type drum in the direction of the printing digit, a cam plate is installed along the forward and backward path of the carriage. A printing hammer is provided on the carriage side so as to be rotatable with one end facing inside the type drum and the other end facing the cam plate side, and the printing hammer is attached to the cam plate at a predetermined printing position. A protrusion that engages with one end is provided, and the end of the cam plate of the printing hammer is provided with a pawl that engages with the protrusion when raising the digit and rotates in a direction to avoid engaging with the protrusion when lowering the digit. A small serial printer characterized by: