JPS5842039B2 - Drafting machine drawing head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drafting machine drawing head for supplying a consumable writing lead, such as a pencil lead, to the paper in a lead holder.

Conventionally, in this type of device, for example, Japanese Patent Application Laid-Open No. 53-91
As seen in Publication No. 768, a rotary disk having a plurality of lead holders is rotatably provided at the Y cursor of a rectangular coordinate drawing machine, and the rotary disk is rotated according to the wear of the lead of the lead holder during use. A device is used that allows unused lead holders to be sequentially set in the use position.

In such devices, the fixed positioning of the rotary disk and the core feeding mechanism use separate operating mechanisms, making the mechanism complex and requiring advanced technology to achieve fixed positioning accuracy of the rotary disk. There was a problem.

Moreover, since it is intended for short lead lengths such as 60 mm, multiple lead holders are provided, and the connections between the drawing lines of one lead and the drawing lines of other leads are intermittent, making it difficult to produce good images. Another drawback is that lines cannot be drawn.

The present invention was devised to solve the above-mentioned problems, and the present invention has been developed to solve the above-mentioned problems.
By using a long core of 0 mm, drawing can be performed for a long time and highly accurate lines can be obtained.

Moreover, since a long lead is used, there is no need to constantly replenish the lead, which simplifies the mechanism, and since the lead remains at a constant drawing position for a long time, the lead can be replaced and set at the drawing position. This eliminates the need for the high degree of precision found in conventional mechanisms.

That is, the drawing head of the drawing machine according to the present invention is attached to a lead chuck holder configured to apply a predetermined pressure in the direction of the drawing surface, moves forward while holding the lead, and detects lead wear. A lead chuck is provided that performs an operation to release the holding of the lead when the lead is released, and when the lead chuck is released, it is held in a predetermined position with respect to the head body in order to detect lead wear and change the lead clamping position. A lead chuck holder lifting mechanism is provided that can raise the lead chuck holder by a predetermined pinch while resisting the pressing force while leaving the lead in the lead lower end holding mechanism, and the lead chuck mechanism holds the lead lower end during drawing. A simple mechanism is adopted in which a finger movement space is provided between the lead chuck and the lead lower end holding mechanism so that the finger can move in the direction of the drawing board as the lead wears out.

The present invention will be described below with reference to embodiments shown in the drawings.

The printing head of the present invention shown in the embodiment has a core chuck mechanism A1.
Lead pressure mechanism B that applies a predetermined pressure to the lead chuck holder to apply finger pressure; Holding mechanism C at the upper end of the lead provided to hold the lead; Holding mechanism D at the lower end of the lead; Lead raising and lowering the lead for drawing. Amplifier down mechanism E1 and core chuck holder lifter iF, :! : It consists of.

First, the core chuck mechanism A will be explained.

That is, as shown in FIG. 6, a core chuck holder 4 is fitted into a core chuck holder guide tube 3 which is vertically installed on the base 2 of the plotter head main body 1 so as to be able to move up and down.
A core chuck body 5 for holding the core a is fitted in the center of the core chuck holder 4 in the axial direction.

A core insertion hole 5a is provided in the center of the core chuck body 5,
Furthermore, a reverse tapered surface is formed on the outer peripheral surface 5b of the tip,
Several slits are formed in the axial direction upward from the tip (not shown) to form a collet.

A large diameter cylindrical portion 5c is formed at the upper end of the core chuck body 5, and an auxiliary guide 5' is screwed into the large diameter cylindrical portion 5c.

Incidentally, the large diameter cylindrical portion 5c of the core chuck main body 5 and the auxiliary guide 5' may be constructed integrally.

,. The reverse tapered surface of the lower end of the core chuck main body 5 is exposed in a concave surface 4a formed at the lower end of the core chuck holder 4,
Furthermore, a ring 6 is fitted to the collet in the recess 4a so as to be able to be freely engaged with and detached from the reverse tapered surface 5b, and also,
A stopper 7, which the ring 6 comes into contact with, is adhesively fixed to the lower edge of the recess 4a.In addition, at the upper end of the core chuck holder 4, there is a case 8 housing a first solenoid 9 that responds to a detection means to be described later. A core guide 9c is provided on the suction disc 9b, which is attached as shown in the figure and is attracted by the coil 9a shown in FIG. 4 of the first solenoid 9.
A core chuck spring 11 is in contact with the upper end of the core chuck body 5 and is located between the lower surface of the large diameter cylindrical portion 5c of the core chuck body 5 and the bottom of the inner hole 10 formed in the core chuck holder 4. 5 is wrapped around and intervening.

Therefore, normally, the core chuck body 5 is urged upward by the core chuck spring 11, and the collet is closed by the ring 6 being engaged with the bottom of the recess 4a formed at the lower end of the core chuck holder 4. Holds core a.

This is the so-called core chuck closed state.

When the first solenoid 9 is turned on, the suction disc 9b is attracted by the coil 9a, and the core guide 9c moves the auxiliary guide 5' down against the force of the core chuck spring 11.
Since the core chuck main body 5 screwed thereon is also lowered, the ring 6 also descends together with the collet at first, but when it hits the stopper γ, it cannot move forward and only the collet 5b continues to descend.

Therefore, the ring 6 is disengaged from the collet 5b, and the collet opens away from the core a, resulting in a so-called core chuck open state.

Next, a core pressing mechanism B which applies a predetermined pressure to the core chuck holder to apply lateral pressure, and a core holding mechanism C provided at the upper end of the core provided for holding the core are constructed as follows.

That is, as shown in FIG. 1, a protective pipe 12 is erected at the center of the case lid 8a that is screwed onto the case 8, and the base of the protective pipe 12 is screwed onto the case lid 8a.

Reference numeral 13 denotes a lateral pressure spring receiver installed upright in the holder 14 which is fixed to the base 2 of the block-head main body 1 with a screw 14a as shown in FIG.
A protective pipe 12 penetrates through the center.

A lateral pressure spring 15 wrapped around a protective pipe 12 is provided in the bad spring receiver 13, and pressurizes the core chuck holder 4 via the case 8.

As described above, the lateral pressure spring 15 is connected to the lateral pressure spring receiver 1.
Since the case lid 8a is supported by the holder 14 via the holder 14 through the holder 14, the case lid 8a is pressed by the lateral pressure spring 15, and a predetermined pressure is applied to the core chuck holder 4, so that the case lid 8a is held by the core chuck of the core chuck holder 4. Lateral pressure is applied to the core.

By providing the protective pipe 12, the core is not only supported through the core chuck body 5 of the core chuck holder 4 and the core guide 9c of the first solenoid 9;
It is also supported by the protective pipe 12, and the longer the protective pipe 12 is, the longer the core can be held.

Next, the holding mechanism for the lower end of the lead will be explained. The lower end of the lead chuck holder guide tube 3 protrudes into the concave hole 2a of the base 2, and a rubber gasket 17 is held in the center of the hood 16 that is fitted into this. There is a plate 16a, and the inner diameter of the center hole of the rubber seal is slightly smaller than the outer diameter of the core a so that the core is held by friction. The upper end of the center hole is formed into a funnel shape as shown in FIG.

A nut 19 that is engaged with the lower surface of the base 2 is screwed into the tightening cylinder 18 that is screwed into the concave hole 2al of the base 2. A spring 20 is interposed between the protruding edges.

Since some space is formed between the upper end of the tightening tube 18 and the bottom of the recessed hole 2a, the degree of screwing of the tightening tube 18 can be adjusted, and the upper end of the tightening tube 18 and the hood can be adjusted. There is also some clearance between it and the outwardly protruding edge of the upper end of No. 16.

As described above, since there is some clearance between the upper end of the tightening tube 18 and the outwardly protruding edge of the upper end of the hood 16, when the lead is fed out, the rubber gasket 17 initially resists the force of the spring 20 by this clearance. Due to the frictional holding force l, the hood 16 descends together with the core a, and its descending stop position is regulated.

At this stop position, a certain gap is formed between the hood 16 and the paper surface, and from the position where the hood 16 stops, the core a
resists the frictional holding force of the rubber packing 11 and further protrudes from the hood 16 by the above-mentioned gap.

The length of the core protruding from the hood 16 is such that the core does not break.

Once the core protrudes from the hood 16, it rises while maintaining its protrusion length due to the frictional holding force of the rubber packing 11, but the hood 16 also rises together with the core within the range of the above-mentioned clearance. It will be changed depending on the degree.

When there is no core, the spring 20 automatically lifts it up.

Further, the outer diameter of the outwardly protruding edge at the upper end of the hood 16 is larger than the inner diameter of the upper end of the tightening tube 18, and from this relationship, the upper end of the tightening tube 18 also serves as a stopper that determines the lowering limit of the hood 16. ing.

Further, in the space 21 between the hood 16 and the lower end of the core chuck holder 4, a core receiver 23 supported from above and below by springs 22, 22a is housed so as to be movable up and down.
There is a core insertion hole 23a in the center.

Then, there is a core insertion hole 23a. And the core insertion hole 23
The inlet of a is formed into a funnel-shaped hole to facilitate insertion of the core a.

By having the core support 23 as described above, the lower end of the core is supported and the core can be prevented from being broken. The core holder 23 descends while being positioned at the center of the space, thereby preventing buckling of the core between the lower end of the core chuck body 5 and the rubber packing 1γ, and completely holding the lower end of the core.

Note that the core chuck holder guide tube 3 is fitted into the base 2 of the plotter head main body 1 from above, and the first,
Since it is fixed to the base 2 with a set screw 24 as shown in FIG. 6, it can be disassembled from the base 2 in conjunction with the above-described mounting structure of the hood 16.

Next, the lead up/down mechanism E for raising and lowering the lead for drawing will be explained.

That is, 25 shown in FIGS. 1 and 6 is a clutch body, which is fitted on the outer periphery of the core chuck holder guide tube 3 and can be slid up and down. Tapered ring 2 formed on a syn-inclined tapered surface
6 is installed inside the lid material 2, which is screwed onto the mortar-shaped part 25a.
A plurality of balls 21 are interposed between the outer periphery of the core chuck holder 4 and the outer periphery of the core chuck holder 4 and the 0 taper ring 26 fixed thereto.
Note that the ball 21 is restricted from descending by the upper end surface of the core chuck holder guide cylinder 3.

Reference numeral 29 shown in FIG. 1 is a second solenoid supported by the plotter head main body 1 via a bracket 30, and its suction disc 29a is drawn down by a coil, and is integrated with the suction disc 29a. The tip of the lever 31 fixed to the operating shaft 29b of the clutch body 25 is connected to the engagement groove 25c of the clutch body 25.
The clutch body 25 is engaged with the clutch body 25 to move it up and down.

Further, an amplifier spring 33 is provided between the lower end of the operating shaft 29b and the cap 32 screwed onto the base 2.

Therefore, when the second solenoid 29 is de-energized, the spring 33 causes the operating shaft 29b to rise, causing the clutch body to rise.

Above the second lensoid 29, a stopper 35 is supported by the plotter head body 1 via a bracket 34.
This restricts the upper limit of movement of the suction disc 29a, and the upper limit position can be finely adjusted by adjusting the degree of screw engagement with the nut 35a.

Since the core up-down mechanism is as described above,
When the second solenoid 29 is turned ON, the taper ring 26 is lowered together with the clutch body 25 from the actuating shaft 29b via the lever 31, and the ball 2γ is in contact with the upper end surface of the core chuck holder guide cylinder 3. Since the downward movement is restricted and the inner surface of the tapered ring 26 is formed into an upwardly inclined tenor ζ-plane, the degree of contact of the ball 27 with the core chuck holder 4 is relaxed, and the so-called locking clutch is unlocked. As a result, the core chuck holder 4 becomes free and can be freely lowered by the acupressure spring 15.

As long as the first solenoid 9 is not turned on, the core chuck is in a closed state, so the core is also held in the core chuck body 5 and moves forward toward the paper surface together with the S core chuck holder 4. The tip of the paper touches the surface of the paper,
A so-called drawing state is established and this state can be maintained.

In addition, in this state, the hood 16 is connected to the core and the compressor skin 1.
It descends with the core due to the frictional force with 1.

Next, when the second solenoid 29 is turned OFF, the actuating shaft 29b is raised by the up spring 33, and the clutch body 25 is raised via the lever 31. Then, the ball 27 is pressed downward by the spring 28. As the clutch body 25 rises, it slides on the tapered surface of the tapered ring 26, which strengthens the degree of contact with the core chuck holder 4, thereby fixing the core chuck holder 4 and the taper ring 26. , the core chuck holder 4 is raised.

In this case, as long as the first solenoid 9 is not turned ON, the lead chuck is in the closed state, so the lead also rises together with the S lead chuck holder 4 while being held by the lead chuck, resulting in the drawing state. Can be canceled.

In this state, the hood 16 is attached to the core and rubber gasket 1.
1 and the force of the spring 20,
Hold this position.

Finally, to explain the core chuck holder lifting mechanism F for changing the core clamping position, as shown in FIG. 2, a rotary solenoid 38 is attached to the block-head body 1 via a bracket 38a. A sector gear 31 is attached to the rotating shaft 38b.

Also, a rack 36 is fixed to the case 8 marked @.
The sector gear 3γ meshes with this, and is driven once by the rotary solenoid 38 which responds to a detection means to be described later.

Further, a sensor shielding plate 39 is fixed to the case 8 as shown in FIG. 3, and a sensor 40 consisting of a light projecting element 40a and a light receiving element 40b as shown in FIG.
is fixed on base 2.

Therefore, when the lead chuck holder 4 is pressed down by the acupressure spring 15 and moves down inside the lead chuck holder kite tube 3 as the lead a wears out, the rotary solenoid 4
Since case 8 is OFF, the sector gear 31 is in a free state and descends together with the core chuck holder 4.
While engaged with the claw 36, it rotates counterclockwise in the direction of the hour hand in Fig. 1.

When the sensor shielding plate 39 is inserted between the light emitting element 40a and the light receiving element 40b of the sensor 40 and detects that a certain amount of the core has been consumed, a signal is sent to the rotary solenoid 38 electrically connected to the sensor shielding plate 39. This is O
N, the sector gear 37 is rotated in the opposite direction to the above rotation direction and returned to its original position.

At this time, the second solenoid 29 is turned on, the clutch is opened by the operation described above, the first solenoid 9 is also turned on in response to the detection means, and the core chuck is opened as described above. Since it is opened by such an operation, the rise of the core chuck holder 4 is not hindered, and since the core a is held by the compressor packing 1γ, the core a remains.
The lead chuck holder 4 rises together with the lead chuck body 5.

Then, when the core chuck holder 4 is raised by a predetermined pitch by the low clean lens 38, the first solenoid 9 is turned off again, the core chuck is closed and the core is clamped at the new position, and the acupressure spring 15 is activated. The core is under pressure and as it wears out, the core chuck holder 4 descends, but in this case the second solenoid 29 is turned on.
Since the state is continued, the drawing state can be maintained continuously, and by repeating the above operation, it is possible to draw continuously until there are no more cores.

The apparatus of the embodiment is constructed as described above, and its handling operations are systematically listed as follows.

(1) Turn on the first renoid 9.

Therefore, the core chuck is opened.

(2) The core a is made to protrude from the rubber packing 11 through the protective pipe 12, the core guide 9c, the auxiliary guide 5', the core insertion hole 5a of the core chuck body 5, and the core insertion hole 23a of the core receiver 23.

(3) The first solenoid 9 is turned OFF, so the core chuck is closed and the core is held by the collet 5b of the core chuck body 5.

(4) Turn on the second solenoid 29 to unlock the locking clutch.

When this lock is released, the core chuck holder 4
becomes free, and lateral pressure is applied to the core by the acupressure spring 15.

In this case, the sector gear 3γ remains in mesh with the rack 36 and can be lowered.

(5) By turning on and off the second solenoid 29, the core is turned down with respect to the paper surface, and at the same time, the plotter head main body 1 is moved relative to the plotting surface using, for example, a rectangular coordinate drawing machine as shown in FIG. One drive in the X-Y coordinate axis direction causes drawing and drawing to be stopped.

That is, when the second solenoid 29 is turned on, the lead is moved down and the drawing state is in effect, and when the second solenoid 29 is turned off, the lead is raised and the drawing is stopped.

(6) When the sensor 39 and 40 detect that the core has been consumed by a certain amount, the first solenoid 9 turns ON in response to that signal.
As a result, the core chunk is opened, and at the same time, the rotary solenoid 38 is also turned on and operates.

In this case, since drawing is in progress, the second solenoid 29 is turned on.
Since the locking clutch is opened, the core chuck holder 4 is raised by a certain pitch due to the engagement between the sector gear 3T and the rack 36, and the sector gear 37 is returned to its original position.

(7) After the predetermined period of time, the first solenoid 9 is turned off, the core shaft is closed, and the new position of the core a is clamped, and at the same time, the rotary solenoid 38 is also turned off, and the sector gear 31 becomes free.

(8) Next, turn on and off the second solenoid 29 to move the lead up and down on the paper surface to draw.

After repeating the above operations, the lack of a core is detected by, for example, the number of times the rotary solenoid 38 is operated, and a new core is replaced.

The embodiments described above illustrate the features of the printing head of the present invention, and the present invention is not limited to these embodiments.

That is, in order to apply a predetermined pressure to the lead holder, in addition to the lateral pressure spring 15, it is necessary to use a weight, a torque motor, or air pressure as shown in Japanese Patent Publication No. 53-3681, or an air motor. You are free to use it in any way you like.

Further, the second solenoid 29 does not need to be a solenoid, and any mechanism such as a motor cam or air pressure may be used as long as it can perform vertical movement.

Of course, any detection means can be used for detecting the wear of the core, and it is also possible to connect it to an alarm if necessary.

In the case shown in Figures 7 and 8, multiple lead holders are installed in-line in the traveling head, and it is possible to detect when the lead holder in use is out of lead and set the unused lead holders in the use position one after another. This shows an embodiment configured as follows, in which an X-axis marker 42.42 is added to the side of the drawing board 41, and an
A y-axis lever 43 is slidably provided through the y-axis lever 44, and a traveling head 45 is slidably mounted on the y-axis lever 43.

The X cursor 44.44 and the running head 45 are equipped with a pulse motor or an arbitrary servo motor that rotates in response to a pulse signal from a pulse transmitter (not shown). Move to the position.

The base housing 4 of the traveling head 45 of the Cartesian coordinate drawing machine as described above.
6 is provided with a plurality of lead holders in-line.

1.1. 1. 1 indicates each plotter head equipped with its core holder. When the core in the core holder of the first block-head 1 runs out, this is detected and the second plotter head 1' returns to the use position. As soon as the plotter head 1' is set, electrical switching is performed and the head 1' becomes ready for use.As the plotter head runs out, the next plotter head is brought to the drawing position one after another, and the plotter head is brought into the operating state. It is what it is.

By arranging the lead holders in-line as described above, drawing can be performed for a long time.

Even if the lead falls over, the present invention is installed in a lead chuck holder configured to be able to apply a predetermined pressure in the direction of the drawing surface, moves forward while holding the lead, and when the lead is detected to have worn out. A lead chuck is provided that performs an operation to release the holding of the lead, and in order to detect lead wear and change the lead clamp position, when the lead chuck is released, the lead held in a predetermined position with respect to the head body. A lead chuck holder raising mechanism is provided that can raise the lead chuck holder by a predetermined pinch while resisting the pressing force while leaving the lead in the lower end holding mechanism. A drawing head of a drafting machine is provided with a lead moving space between the lead chuck and the lower end holding mechanism of the lead that can move toward the drawing board as the lead wears out. Since the lead chuck attached to the lead chuck holder can be used to feed out the lead by changing its clamping position, it is possible to use long leads, thus making it possible to draw for a long time. It has the characteristic of being able to obtain lines with high density, and since it uses a long lead, there is no need to replenish the lead in a short time, so it is easy to draw even though the mechanism is extremely simple. It also has the characteristic of improving efficiency.

Therefore, during drawing, a lead moving space is provided between the lead chuck and the lead lower end holding mechanism so that the lead chuck can move toward the drawing board as the lead wears out relative to the lead lower end holding mechanism. The length section of the lead from one clamping position to the clamping position for feeding the next lead becomes longer, which increases the drawing time during which the lead is exhausted in that section and requires the lead chuck holder lifting mechanism to be operated frequently. As a result, the frequency of feeding out the lead is reduced, and the position of the lead stays at a constant drawing position for a long time, allowing highly accurate line changes. Regardless of the movement of the chuck, the lead lower end holding mechanism is held at a predetermined position with respect to the head body, and the distance between the lead lower end holding mechanism and the drawing surface can be shortened, so the lead lower end holding mechanism can be moved away from the lead lower end holding mechanism. The length of the lead protruding toward the drawing surface is short, making it difficult to break, allowing for long drawing times and highly accurate line changes.

Note that the present invention can be used not only for long cores but also for short cores.

[Brief explanation of the drawing]

Fig. 1 is a cutaway front view of the printing head of the present invention, Fig. 2 is a cutaway plan view of the same as above, Fig. 3 is a cutaway side view of the same as above, Fig. 4 is an explanatory diagram of the first lensoid, and Fig. 5 is an explanation of the sensor. 6 is a sectional view of the essential parts of the present invention, FIG. 7 is a perspective view of the Cartesian coordinate drawing machine, and FIG. 8 is a perspective view of the running head. Core chuck mechanism A, 3...Core chuck holder guide tube, 4...Core chuck holder, 5...
... Core chuck body, 6 ... Ring, γ.
... Stopper 8 ... Case, 9 ...
... 1st solenoid, 11... Spring for four-finger chuck. Core pressure mechanism B applies a predetermined pressure to the core chuck holder to apply finger pressure. 13...Shiatsu spring receiver, 14...
・Holder 15...Shiatsu spring. Holding mechanism c, 8 at the upper end of the lead provided to hold the lead
a...Curved case lid, 12...Protection pipe. Holding mechanism at the lower end of the core D・16...Hood, 1γ・
...Rubber gasket, 18...Tightening tube, 1
9...Natsuto, 20...Spring,
21... Space, 22.22a... Spring, 23... Core holder. Lead up/down mechanism E that raises and lowers the lead as you draw,
25...Clutch body, 26...7-
Par IJ, 2γ...Ball, 28...
...Spring, 29...Second renoid,
29b...Operating shaft, 31...Lever. Core chuck holder lifting mechanism F, 36...Rank, 3γ...-M-shaped gear shaft 38...Rotary solenoid, 39.40...Sensor.

Claims (1)

[Scope of Claims] 1. A S with a core attached to a core chuck holder configured to apply a predetermined pressure in the direction of the drawing surface.
A lead chuck is provided that releases the holding of the lead when the head moves forward and detects lead wear, and when the lead chuck is released to detect lead wear and change the lead clamp position, the head body A lead chuck holder lifting mechanism is provided which can raise the lead chuck holder by a predetermined pitch against the pressing force while leaving the lead in the lead lower end holding mechanism which is held in a predetermined position against the drawing. A drawing head for a drafting machine, wherein a lead moving space is provided between the lead chuck and the lead lower end holding mechanism, in which the lead chuck can move toward the drawing board surface as the lead wears out relative to the lead lower end holding mechanism. 2. A drawing head for a drafting machine according to claim 1, wherein a protective pipe is provided above a case connected to a lead chuck holder to hold and hang a long lead. 3. The drawing according to claim 1 or 2, in which the pressurizing mechanism is constituted by a holder provided in the head body, which is provided with a spring receiver containing a bad spring for pressurizing the core chuck holder. Machine drawing head. 4. A core chuck body that can be raised and lowered, with a core insertion hole in the center, a reverse tapered surface on the outer peripheral surface of the tip, and several slits formed in the axial direction upward from the tip, and a reverse taper. The core chuck consists of a ring that engages and disengages from the surface to tighten and release the core in the core chuck body, and a stopper provided on the core chuck holder that contacts the ring and releases the reversely tapered surface. A drawing head for a drafting machine according to any one of claims 1 to 3. 5. A first element responsive to the core eliminating net detecting means for lowering the core chuck body against the force of the spring, thereby bringing the ring into contact with the stopper of the core chuck holder and releasing the collet of the core chuck body. A drawing head for a drafting machine according to any one of claims 1 to 4, which is provided in a case that connects a solenoid to a core chuck holder. 6. Claims 1 to 6, wherein a certain core movement space is provided between the core chuck holder and the lower surface of the head body, and a movable core holder supported from above and below by a spring is installed inside the space. A drawing head for a drafting machine according to any one of Item 5. 1. Claim No. 1, comprising a core chuck holder lifting mechanism in which a fan-shaped gear driven by a rotary solenoid activated by detecting wear of the core is engaged with a rack of a case connected to the core chuck holder. A drawing head for a drafting machine according to any one of items 1 to 6. 8 A detector for detecting core wear is composed of a sensor shielding plate provided in a case connected to the core chuck holder and a light emitting element provided in the head body, and the sensor shielding plate intercepts the light from the light emitting element. A drawing head for a drafting machine according to any one of claims 1 to 1, further comprising a detection means that blocks the light from being received by the light receiving element.