Note: Descriptions are shown in the official language in which they were submitted.
1328988
DEVICE FOR RESHAPING THE CONTOUR SURFACE OF
THE PLASTIC INJECTION HOLE OF A METAL MOLD
Background of the Invention
Field of the Invention
The present invention relates to a device for
reshaping the contour surface of the plastic
injection hole of a metal mold, which metal mold is
used in a plastic injection molding apparatus.
Description of Prior Art
Every time plastic material is injected into a
plastic injection metal mold, the injection nozzle
is pushed against the injection hole of the metal
mold, and accordingly the contour surface of the
~ injection hole of the metal mold wears. Then, a gap
¦~ 15 appears between the metal mold and the nozzle tip,
thus allowing plastic to leak through the gap space.
¦~ The resulting burr of the plastic mold product is
caught by the metal mold around its injection hole,
thus making it inconvenient to remove the plastic
mold product from the metal mold. Therefore, it is
necessary to machine the contour surface of the
injection entrance to its original shape, so that
` the gap between the metal mold and the nozzle tip
may be reduced when the nozzle tip is applied to the
injection hole of the metal mold.
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The reshaping work, however, requires removal of a
heavy metal mold from a molding apparatus and subsequent
attachment of the metal mold to a lathe. This is a
tedious and time consuming work. Also, disadvantageously
5 the molding work is interrupted for a relatively long
time, and accordingly the efficiency with which molding
is effected, lowers.
Summary of the Invention
With the above in mind one object of the present
10 invention is to provide a device for reshaping the
contour surface of the plastic injection hole of a metal
mold which device permits necessary reshaping work in
situ without removing the worn metal mold from a molding
apparatus and attaching it to a lathe.
To attain this object a device for reshaping the
contour sruface of the plastic injection hole of a metal
mold according to the present invention comprises: a
magnetic block comprising upper and lower intervenient
barrier sections of non-magnetic material and opposite
20 concave pieces of magnetic material sandwiching the non-
magnetic barrier sections to define a circular hole, and
a permanent magnet cylinder rotatably fitted in the
circular hole thus defined, thereby causing appearance
of the magnetic field across the opposite ends of the
25 magnetic block when the permanent magnet cylinder is
rotated to the position in which its poles N and S are
on a line parallel to the bottom of the magnetic block,
and causing disappearance of the magnetic field across
the opposite ends of the magnetic block when the
30 permanent magnet cylinder is rotated to the position in
which its poles N and S are on a line perpendicular to
the bottom of the magnetic block; an arm one end of
which is fixed to the magnetic block and the other end
of which arm has a translational rod movable in
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alignment with the central axis of the contour surface
of the plastic injection hole of the metal mold; and a
cutter tool comprising a housing, a spring-biased trunk
contained in and movably fixed to the housing and a
5 cutter blade which is operatively connected to the
spring-bias`ed trunk so as to move back and forth under
the influence of a spring.
The reshaping device may further comprise a jig
which is adapted to be detachably fixed to the magnetic
10 block. The jig has a pointing rod in alignment with the
translational rod on the free end of the arm.
According to a preferred embodiment the cutter
blade is fixed to the front end of the trunk; the rear
colsed end of the housing has a reentrancy to accomodate
15 the tip of the translational rod, and the spring is put
in the space between the rear closed end of the housing
and the rear end of the trunk.
According to another preferred embodiment the
cutter blade is fixed to the front end of the housing,
20 and the trunk is fitted in and movably connented to the
housing. The rear of the trunk has a reentrancy to
accomodate the tip of the translational rod, and the
spring is put in the space between the front end of the
trunk and the bottom of the housing.
A retractable arm which is capable of adjusting
its length, can be used in place of the arm having a
translational rod at its free end.
In use the jig is attaced to the magnetic block,
and the permanent magnet cylinder is rotated to the
30 demagnetizing position. The magnetic bolck is moved on
the metal mold A until its pointing rod is put in
alignment with the injection hole of the metal mold.
Then, the permanent magnet cylinder is rotated to the
magnetizing position, thereby causing the magnetic block
35 to attach itself to the metal mold. The jig is removed
from the magnetic block, and-then the translational rod
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is automatically put in alignment with the central axis
i of the contour surface of the injection hole.
J. The translational rod is made to advance to
sandwich the cutter tool between the contour surface of
5 the injection hole of the metal mold and the
translational rod. Then, the cutter blade is rotated by
holding and rotating the tool housing by hand until the
contour surface of the injection hole is cut to its
original shape.
The cutter tool is removed from the arm by
¦ withdrawing the translational rod, and then the the
permanent magnet cylinder is rotated to the
demagnetizing position, thereby permitting the removal
of the magnetic block from the metal mold.
Other objects and advantages of the present
invention will be understood from the following
description of a preferred embodiment, which is shown in
accompanying drawings:
Fig.1 is a side view of a reshaping device
20 according to an embodiment of the present invention in
its reshaping position;
Fig.2 is a similar side view, but showing the
reshaping device with its jig attaced in place of its
) cutting tool;
Fig.3 is a side view of another cutting tool,
partly broken and shown in section;
Fig.4 is a perspectïve view of the reshaping
device with its jig attaced in place of its cutting
tool;
f 30 Fig.5 is a perspective view of the jig;
Fi9.6 is a cross section of a magnetic bolck in
its demagnetizing position;
Fig.7 is a cross section of a magnetic block in
its magnetizing position; and
' 35 Fig.8 shows a metal mold in section and an
injection nozzle tip.
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1328988
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Embodiments
Fig. 8 shows a plastic injection mold A and the
injection nozzle S of a plastic injection molding
apparatus. Every time plastic material is injected
into the mold, the nozzle S is pushed against the
injection hole of the metal mold A, and accordingly
the contour surface T of the injection hole of the
metal mold wears. Then, a gap appears between the
metal mold and the nozzle tip, thus allowing plastic
to leak through the gap space. The resulting burr
of the plastic mold product is caught by the metal
mold around its injection hole, thus making it
inconvenient to remove the plastic mold product from
the metal mold. Therefore, it is necessary to
machine the contour surface of the injection
entrance to its original shape, so that the gap
between the metal mold and the nozzle tip may be
reduced when the nozzle tip is applied to the
injection hole of the metal mold.
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Referring to Fig.4, 6 and 7, a magnetic block 3 is
shown as comprising upper and lower intervenient barrier
sections of non-magnetic material 1 and opposite concave
5 pieces of ma~netic material 2 sandwiching the non-
magnetic barrier sections 1 to define a circular hole,
and a permanent magnet cylinder 4 rotatably fitted in
the circular hole thus defined. The permanent magnet
cylinder 4 is chamfered on opposite sides as indicated
10 at 5, and it has N and S poles. As best shown in Fig.4 a
rotary cap H is put on the top of the cylinder 4. The
magnetic field will appear across the opposite ends 6 of
the magnetic block 3 when the permanent magnet cylinder
4 is rotated by the rotary cap H to the magnetizing
'(~ 15 position in which its poles N and S are on a horizontal
line parallel to the bottom of the magnetic block 3 (See
Fig.7). The magnetic field across the opposite ends 6 of
the magnetic block 3 will disappear when the permanent
magnet cylinder 4 is rotated to the demagnetization
20 position in which its poles N and S are on a vertical
line perpendicular to the bottom of the magnetic block 3
(See Fig.6).
One end of an arm 7 is fixed to the magnetic block
3 and the other end of the arm 7 has a translational
25 screw rod 8 movable in alignment with the central axis
s of the contour surface T of the plastic injection hole
of a metal mold A.
As shown in Fig.1, a cutter tool comprises a
housing 11, a spring-biased trunk 10 contained in and
30 movably fixed to the housing 11 and a cutter blade 9
fixed to the spring-biased trunk 10 so as to move back
and forth under the influence of a spring 12.
Specifically the trunk 10 has a key slot 18 on its
circumference, and the housing 11 has a key 17. The
35 trunk 10 is inserted in the housing 11 with the key 17
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extending in the key slot 18 of the trunk surface. The
spring 12 is put in the space between the rear closed
end of the housing 11 and the rear end of the trunk 10,
thus applying a resilient push to the trunk 10 all the
time.
Preferably the cutter blade 9 may have a centering
' projection 9a to assure that the cutter blade 9 is put
¦ in exact alignment with the center axis of the injection
s hole 15 of the metal mold A. The rear end of the housing
10 11 has a seat metal 19. It has a reentrancy to
accomodate the tip of the translational screw rod 8.
As shown in Fig.1, the worn contour surface T of
therinjection hole can be reshaped to its original shape
simply by rotating the cutter tool by hand, which tool
15 is resiriently pushed against the metal mold A all the
time. In this position metal chips cannot enter the
cavity C of the metal mold.
Fig.3 shows another cutter tool as comprising a
houseing 11 having a cutter blade 9 fixed to its closed
20 front and a trunk 10 fitted in and movably fixed to the
housing. Specifically the trunk 10 has a key slot 18 and
the housing has a key 17. The trunk 10 is fitted in the
hollow space of the housing 10 with the key 17 inserted
in the key slot 18.
Fig.5 shows a jig 13 of a transparent synthetic
resin, which jig can be detachably fixed to the magnetic
block 3. The jig 13 has two opposite legs 13a and a
; pointing rod 16. The pointing rod 16 will be put in
' alignment with the translational screw rod 8 on the free
j 30 end of the arm 7 when the jig 3 is attached to the
magnetic block 2 with its legs 13a put on the opposite
sides of the magnetic block 2.
Then, the magnetic cylinder 4 is rotated to put
the magnetic block 3 in its demagnetizing position. The
35 magnetic block 3 is moved on the metal mold A until it
reached the position in which the pointing rod 16 can be
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1328988
inserted in the injection hole 15 of the metal mold A.
After inserting the pointing rod 16 in the
injection hole 15 of the metal mold A the magnetic
cylinder 4 is rotated to put the magnetic block 3 in its
5 magnetizing position. Then, the magnetic block 3 is
attached to the metal mold A, and the jig 3 along with
its pointing rod 16 is removed from the magnetic block
3. The blade 9 of the cutter tool is pushed against the
injection hole of the metal mold A, and the
10 translational screw rod 8 is made to advance and push
the rear end of the cutter tool until the trunk 10
yieldingly withdraws in the housing 11. Thus, the cutter
tool is resiliently supported between the metal mold A
and the translational screw rod 8, and then the cutter
15 tool is put in the exact alignment with the center of
the injiction hole of the metal mold A. Reshaping can be
effected simply by rotating the cutter tool by hand.
A retractable arm which is capable of adjusting
its length, can be used in place of the arm 7 having a
screw rod 8 at its free end.
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