[0001] The present invention relates to a gas venting arrangement in an injection molding
apparatus such as a die casting machine. More, particularly, the invention relates
to a metal mold structure having a gas venting unit provided separately and detachably
from a stationary or movable metal mold of the metal mold structure, and a jig for
facilitating a removal of the gas venting unit from the stationary or movable metal
mold.
[0002] One example of a conventional injection molding apparatus is described in Japanese
Patent Application Kokai No. Sho-63-313645. The disclosed apparatus is shown in Fig.
8. In the injection molding apparatus shown in Fig. 8, a stationary metal mold 1 and
a movable metal mold 3 are provided, and a mold cavity 9 is formed therebetween. The
mold cavity 9 has a lower end portion in communication with a runner 5 through a gate
7. At a lower portion of the stationary metal mold 1, a casting sleeve 11 is insertedly
disposed which is in communication with a lower end of the runner 5. The casting sleeve
11 has another end formed with a casting port 13 through which the molten metal is
casted. Within the casting sleeve 11, a plunger 15 is slidably accommodated which
is reciprocable in an axial direction of the casting sleeve 11. The plunger 15 is
connected to an injection cylinder 19 through a plunger rod 17. Upon operation of
the injection cylinder 19, the plunger 15 is reciprocable within the casting sleeve
11 for urging the molten metal toward the mold cavity 9. A striker 21 is provided
on the plunger rod 17. Further, a limit switch 23 for starting vacuum evacuation and
a high speed limit switch 25 are provided at positions along a moving stroke of the
striker 21. In accordance with the axial motion of the plunger rod 17, the striker
21 is abuttable against the limit switches 23 and 25.
[0003] A parting faces 27 are defined at confronting surfaces of the stationary and the
movable metal molds 1 and 3. and a gas vent passage 29 is formed at an upper portion
of the parting face 27. The gas vent passage 29 is connected to a vacuum suction means
33 through a pipe 31. The vacuum suction means 33 includes an electromagnetic change-over
valve 35, a tank 37, a vacuum pump 39 and a drive motor 41. The electromagnetic change-over
valve 35 has a first change-over position 35a and a second change-over position 35b,
and when the valve 35 is changed over to the first change-over position 35a, the gas
vent passage 29 is brought to fluid communication with the vacuum suction means 33.
[0004] A gas vent valve 43 is positioned in the gas vent passage 29. The gas vent valve
43 is opened or closed by a valve driving mechanism 45. That is, the gas vent valve
43 includes a valve body 47 and a valve stem 49 which is connected to a piston 53
slidably disposed in a valve driving cylinder 51. The valve driving mechanism 45 includes
a compressor 55 and an electromagnetic change-over valve 57. The compressor 55 is
connected to the valve driving cylinder 51 through the electromagnetic change-over
valve 57 and pipes 59,61. A compressed airfrom the compressor 55 is applied to one
of a front chamber 63 and a rear chamber 65 of the valve driving cylinder 51 through
the valve 57 and one of the pipes 59 and 61.
[0005] Thus, the piston 53 is slidably moved in the cylinder 51 so as to move the valve
body 47 toward and away from a valve seat portion 67 for closing or opening the gas
vent valve. The electromagnetic valve 57 has a first change-over position 57a and
a second change-over position 57b. When the valve 57 has the first change over position
57a, the compressive air is supplied to the front chamber 63 through the pipe 59 for
retractingly moving the piston 53 to seat the valve body 47 onto the valve seat 67,
to thereby shut off the fluid communication between the gas vent passage 29 and the
pipe 31. On the other hand, when the electromagnetic valve 57 has the second change-over
position 57b, the compressed air is supplied to the rear chamber 65 through the pipe
61 for frontwardly moving the piston 53 to move the valve body 47 away from the valve
seat 67, to thereby provide fluid communication between the gas vent passage 29 and
the pipe 31.
[0006] Further, a detection rod 69 is disposed at the gas vent passage 29. The detection
rod 69 detects the molten metal urged upwardly in the gas vent passage for transmitting
a molten metal detection signal to an electrical or electron ic circu it (not shown).
In response to the detection signal, the electrical circuit will send control signal
to the electromagnetic change-over valve 57 for closing the gas vent valve 43.
[0007] With the structure thus organized, an operation will be described. With the gas vent
valve 43 being opened, the molten metal is casted into the casting sleeve 11 through
the casting port 13. Then, the injection cylinder 19 is driven for slidingly moving
the plunger 15 toward the stationary metal mold 1. By the sliding movement of the
plunger 15, the casting port 13 is closed by the plunger, and further, the vacuum
start limit switch 23 is actuated by the striker 21. In response to the actuation
of the vacuum start switch 23, the electromagnetic change-over valve 35 is changed-over
to the first change-over position 35a by way of the electric circuit (not shown).
By the change-over operation of the electromagnetic change-over valve 35, the gas
vent passage 29 becomes communicated with the vacuum suction means 33. Therefore,
gas in the casting sleeve 11, the runner 5 and the mold cavity 9 is sucked and discharged
through the gas vent passage 29 and the pipe 31.
[0008] When the plunger 15 is further slidingly moved, the casted molten metal is filled
in the mold cavity 9 and is flowed into the gas vent passage 29, so that the molten
metal is brought into contact with the detection rod 69. Therefore, the molten metal
detection signal is generated. In response to the detection signal from the detection
rod 69, the electromagnetic change-over valve 57 is changed-over to the first change-over
position 57a by way of the electrical circuit (not shown). By the actuation of the
electromagnetic change-over valve 57, the compressed air from the compressor 55 is
supplied to the front chamber 63 of the cylinder 51, to thereby retractingly move
the piston 53 (rightwardly in Fig. 8). When the piston 53 is retracted to a predetermined
position, the valve body 47 is seated onto the valve seat 67 to provide the valve
closing position. By the closure of the gas vent valve 43, the gas vent passage 29
is shut off for suspending the vacuum sucking operation by the vacuum suction means
33.
[0009] Generally, in the conventional injection molding apparatus, the molten metal may
be entered into the gas vent passage 29 and the gas vent valve 43 during the injection
molding operation. Due to the repeated injection molding operations, a small mass
of solidified molten metal may be deposited onto a position adjacent the valve stem
49 and the valve body 47. Further, oil may also be adhered to the valve stem 49, and
is baked and deposited thereon. Accordingly, the gas vent valve 43 is rendered inoperable
due to the deposited materials. In this case, maintenance and inspection have to be
carried out for removing the adhered or deposited materials. Alternatively, required
is the replacement of several mechanical component by new components.
[0010] However, in the conventional arrangement, the gas vent passage 29 is directly formed
in the metal molds 1 and 3, and the gas vent valve 43 or ambient components are not
easily disassembleable from the stationary metal mold 1 or the movable metal mold
3. Therefore, it would be difficult to achieve the above described maintenance, inspection
and replacement work.
[0011] Further, in order to deal with this problem, a proposal is made such that a component
around the gas vent passage 29 and the gas vent valve 43 is provided as a separate
unit it so as to permit the u nit to be detachable from the stationary and movable
metal molds 1 and 3. However, in case of the detachment of the unit, molten metal
flash and relative surface deformation between the molds and the unit may render the
detaching work difficult.
[0012] The present invention has been established in view of the above described standpoint,
and it is an object of the present invention to provide a metal mold structure having
a gas venting unit in which a part of a gas vent passage and a gas vent valve are
provided, which unit is provided detachably from a stationary or movable metal mold,
and to provide ajig forfacilitating removal of the gas venting unit from the metal
molds in an injection molding apparatus.
[0013] This and other object of the invention will be attained by providing a metal mold
structure in an injection molding apparatus, the metal mold structure including a
metal mold in which a mold cavity is formed, and a gas venting arrangement in which
a gas vent passage is communicated with the mold cavity and the gas vent passage is
selectively shut off from an exterior by means of a gas vent valve means; the metal
mold structure comprising (a) a metal mold whose one surface defines a parting face
and formed with an upper opening at a side of the parting face, (b) a gas venting
unit provided separate from the metal mold and having a given external contour, the
gas vent valve means being disposed in the gas venting unit, (c) an insertion segment
fittingly insertable into a part of the upper opening, a unit insertion recessed portion
being defined by the upper opening and the insertion segment when the insertion segment
is inserted thereinto, the unit insertion recessed portion having an configuration
substantially coincident with the external contour of the gas venting unit for receiving
the unit into the unit insertion recessed portion, and (d) a fixing means for fixing
the gas venting unit in the unit insertion recessed portion.
[0014] In another aspect of the invention there is provided a combination comprising the
metal mold structure in an injection molding apparatus, and a jig device. The metal
mold structure comprises the metal mold, the gas venting unit, the insertion segment,
and the fixing means. The gas venting unit has a top portion formed with an exhaust
pipe attachment hole. The jig device is adapted for removing a gas venting unit from
the unit insertion recessed portion of the metal mold structure, and the jig device
comprises (a) a jig body mounted on the metal mold at a position in confrontation
with the exhaust pipe attachment hole, the jig body being formed with a through hole
alignable with the exhaust pipe attachment hole, (b) a bolt-like moving means comprising
a head portion and a shaft portion integral therewith and formed with a threaded portion
at least at a tip end portion thereof, the shaft portion being passable through the
through hole and the threaded portion being threadingly engageable with the exhaust
pipe attachment hole, and (c) means for driving the bolt-like moving means, the driving
means being positioned between the bolt-like moving means and the jig body and being
driven for upwardly moving the bolt-like moving means, to thereby lift the gas venting
unit engaged with the bolt-like moving means for removing the gas venting unit from
the unit insertion recessed portion.
[0015] With the structure, the gas venting unit is a separate unit in which gas vent valve
is disposed, and the unit is detachably insertable into the unit insertion recessed
portion defined by a combination of the upper opening of the metal mold and the insertion
segment inserted in the upper opening. Therefore, the gas venting unit can be easily
detached at any time, which in turn facilitates maintenance, inspection and replacement
work to the gas venting unit.
[0016] For removing the gas venting unit from the unit insertion recessed portion by using
the jig device, the jig is firstly mounted on the metal mold. then, the tip end of
the bolt-like moving means is threadingly engaged with the gas venting unit. Thereafter,
the drive means is operated for upwardly moving the bolt-like moving means. As a result,
the gas venting unit positioned in the recessed portion can be easily removed therefrom.
[0017] In the drawings;
Fig. 1 is an exploded perspective segmental view showing a metal mold structure according
to a first embodiment of the present invention;
Fig. 2 is an exploded perspective segmental view showing a metal mold structure according
to a second embodiment of the present invention;
Fig. 3 is an exploded perspective segmental view showing a metal mold structure according
to a third embodiment of the present invention;
Fig. 4 is an exploded perspective segmental view showing a metal mold structure according
to a fourth embodiment of the present invention;
Fig. 5 is a side view showing a jig for removing a gas venting unit from a metal mold
according to one embodiment of this invention;
Fig. 6 is a side view for description of operation of the jig of the first embodiment
shown in Fig. 5;
Fig. 7 is a side view showing a jig for removing the gas venting unit according to
another embodiment of this invention; and
Fig. 8 is a schematic cross-sectional view showing a conventional injection molding
apparatus.
[0018] A metal mold structure having a gas venting unit in an injection molding apparatus
according to a first embodiment of the present invention will be described with reference
to Fig. 1. The metal mold structure according to this embodiment generally includes
a stationary metal mold 101, an insertion segment 105 and a gas venting unit 113.
The stationary metal mold 101 has an upper surface portion confronting a movable metal
mold (not shown) formed with a T-shaped opening 103 (in horizontal cross section)
for receiving therein the insertion segment 105. Upon fitting engagement of the insertion
segment 105 with the T-shaped opening 103, a cruciform shaped opening (unit insertion
recessed portion) 111 is provided into which the gas venting unit 113 is insertable.
[0019] The T-shaped opening 103 is formed at an uppermost portion of the stationary metal
mold 101 at a position close to the movable metal mold (not shown). A head or arm
portion of the T-shaped opening 103 has a height equal to a height of the insertion
segment 105. Further, a leg portion of the T-shaped opening 103 has a height equal
to a height of the gas venting unit 113. Furthermore, the arm portion of the T-shaped
opening is provided with abutting surfaces d' and f'.
[0020] The insertion segment 105 is inserted into the arm portion of the T-shaped opening
103. The insertion segment 105 is formed with a T-shaped grooved portion 109. Thus,
upon insertion of the insertion segment 105 into the T-shaped opening 103, the cruciform
shaped opening (unit insertion recessed portion) 111 is provided. In the unit insertion
recessed portion 111, the gas venting unit 113 is detachably inserted. In an interior
of the venting unit 113, a cylinder, a piston, a valve body and a valve seat, such
as those described in the "Background of the Invention" section are assembled. The
gas venting unit 113 has a cruciform shape in a horizontal cross-section, and includes
frontward/rearward positioning protrusions 113a, 113b and a lateral positioning protrusion
113c extending perpendicular to the protrusions 113a, 113b and in a direction from
the stationary metal mold 101 to the movable metal mold (not shown).
[0021] A width (in a direction X in Fig. 1) and a length (in a direction Y in Fig. 1) of
the lateral positioning protrusion 113c are equal to a width and a length of the leg
portion of the T-shaped grooved portion 109 of the insertion segment 105. The lateral
positioning protrusion 113c has abutting surfaces a and b at lateral end faces thereof
in the widthwise direction (X), and has a bottom abutting surface g. Further, the
frontward/rearward positioning protrusions 113a and 113b are formed with abutting
surfaces e, f, and c, d. A width (in the direction Y in Fig. 1) of the frontward/rearward
positioning protrusions 113a, 113b is equal to a distance between the abutting surface
c', e' of the insertion segment 105 and the abutting surface d', f of the T-shaped
opening 103 of the stationary metal mold 101. Further, a distance between the lateral
end surfaces of the frontward/rearward positioning protrusions 113a, 113b of the gas
venting unit 113 (in the X direction in Fig. 1) is made slightly smaller than the
length (in the X direction) of the head portion of the T-shaped groove 109 of the
insertion segment 105. Furthermore, a width (X direction) and a length (Y direction)
of the major portion of the gas venting unit 113 are made slightly smaller than the
width and the length of the leg portion of the T-shaped opening 103 of the stationary
metal mold 101. That is, an external contour of the gas venting unit 113 is substantially
similar to the cruciform shaped opening 111 defined by the T-shaped opening 103 of
the stationary metal mold 101 and the T-shaped grooved portion 109 of the insertion
segment 105. With this arrangement, the gas venting unit 113 can be detachably and
position- adjustably inserted with respect to the cruciform shaped opening 111.
[0022] At one face of the gas venting unit 113 (the face confronting the movable metal mold)
and at the face of the lateral positioning protrusion 113c, a valve hole 115 is opened,
and at an upper face of the gas venting unit 113 an exhaust pipe attachment hole 117
is formed with which an exhaust pipe (not shown) is threadingly engageable. The exhaust
pipe attachment hole 117 is in fluid communication with the valve hole 115 within
the unit 113, and the above described valve body and the valve seat are provided at
the communicating portion. A female thread is formed at an inner peripheral surface
of the exhaust pipe attachment hole 117. The hole 117 is threadingly engageable with
a pipe (see 31 in Fig. 8) which is connected to a vacuum pump (see 39 of Fig. 8) through
an electromagnetic change-over valve (see 35 in Fig. 8).
[0023] The metal mold structure of this embodiment is also provided with a fixing means
119 for fixing the gas venting unit 113 to the stationary metal mold 101. The fixing
means 119 includes a bolt 121 and a plate member 125 formed with an elongated slot
123 to allow a shaft portion of the bolt 121 to pass therethrough. At an upper portion
of the insertion segment 105, a pair of threaded bores 127 are formed for threading
engagement with the bolt 121. The bolt 121 is threadingly engaged with the threaded
bore 127 with interposing the plate member 125 therebetween. The plate member 125
has a sufficient area such that when the plate member 125 is fixed to the insertion
segment 105 by the bolt 121, the plate member 125 abuts and depresses the top surface
of the gas venting unit 113 for fixing the same 113 at the cruciform shaped opening
or gas venting unit insertion recessed portion 111.
[0024] Next, assembling work with the thus described metal mold structure will be described.
Firstly, the insertion segment 105 is fitted with the head portion of the T-shaped
opening 103 of the stationary metal mold 101. Therefore, the cruciform shaped opening
111 is provided by the opening 103 and the T-shaped grooved portion 109 of the insertion
segment 105. Next, the gas venting unit 113 is fitted within the cruciform shaped
opening 111. In this case, the positioning of the gas venting unit 113 with respect
to rightward and leftward direction in Fig. 1 (X direction) is fulfilled by the surface
abutment between the abutment surfaces a and b of the gas venting unit 113 and the
abutment surfaces a',b' of the T-shaped grooved portion 109. Further, the positioning
with respect to frontward and rearward direction in Fig. 1 (Y direction) is fulfilled
by the surface abutment between the abutment surfaces c, d, e, f and the abutment
surfaces c', d', e' and f'. Furthermore, the positioning with respect to the vertical
direction is achieved by the abutment between the surfaces g of the gas venting unit
113 and the abutment surface g'.
[0025] Upon completion of the fitting engagement of the gas venting unit 113 with the cruciform
shaped opening 111, the gas venting unit 113 is urgedly held into the cruciform shaped
opening 111 by the fixing means 119. Firstly, the plate member 125 is positioned on
the top surface of the insertion segment 105. In this case, the elongated slot 123
of the plate member 125 is aligned with the threaded hole 127 formed at the top portion
of the insertion segment 105, and a part of the plate member 125 is also positioned
on the top surface of the gas venting unit 113. Then, the bolt 121 is inserted through
the elongated lot 123, and is threadingly engaged with the threaded hole 127. If necessary,
another pair of the bolt 121 and the plate member 125 are prepared for threadingly
engaging with the other threaded hole 127. Upon fastening of the bolt 121, the plate
member 125 is firmly contacted with the top surfaces of the insertion segment 105
and the gas venting unit 113 for preventing the unit 113 from removing out of the
cruciform shaped opening 111.
[0026] In order to remove the gas venting unit 113 from the stationary metal mold 101, the
bolt 121 is unfastened for moving the plate member 123 away from the top surfaces
of the gas venting unit 113. Then, a jig (described later) for removing the gas venting
unit is employed for removing the unit 113 from the stationary metal mold 101.
[0027] Next, a metal mold structure according to a second embodiment of this invention will
be described with reference to Fig. 2, wherein essential construction is substantially
the same as that of the first embodiment, and therefore, fixing means (119 in Fig.
1) is omitted for simplicity. The primary difference between the first and the second
embodiments resides in an external contour of the gas venting unit 113' and a cruciform
shaped opening 111' which receives the unit 113' therein.
[0028] More specifically, a stationary metal mold 101' is formed with a T-shaped opening,
and an insertion segment 105' is formed with a T-shaped grooved portion similar to
the first embodiment. Further, similar to the first embodiment, a cruciform shaped
opening (unit insertion recessed portion) 111' is defined by the T-shaped opening
and the T-shaped grooved portion upon insertion of the insertion segment into the
T-shaped opening of the stationary metal mold 101'.
[0029] The gas venting unit 113' has a cruciform shape in a horizontal cross-section similar
to the first embodiment. That is, the unit 113' includes a lateral positioning protrusion
113c' extending toward a movable metal mold (not shown), and frontward/rearward positioning
protrusions 113a', 113b' extending from a root portion of the protrusion 113c' in
a direction perpendicular thereto. As shown in Fig. 2, each of the positioning protrusions
113a', 113b' and 113c' are so configured that widths of these protrusions are gradually
small toward a bottom of the gas venting unit 113. That is, a distance between abutment
surfaces a and b, between abutment surfaces c and d and between abutment surfaces
e and f are gradually small toward the bottom. In conformity with these slanting abutment
surfaces, corresponding portions of the cruciform shaped opening 111' also have slanting
abutment surfaces a', b', c', d', e' and f'.
[0030] More specifically, the abutment surfaces a and b provided at the lateral positioning
protrusion 113c' are slantingly and symmetrically oriented so as to gradually reduce
its width toward a bottom. Further, abutment surfaces a' and b' at the T-shaped grooved
portion formed in the insertion segment 105' have inclination angles the same as those
of the abutment surfaces a and b. Similarly, abutment surfaces c and e of the frontward/rearward
positioning protrusions 113a' and 113b' are also inclined, and corresponding abutment
surfaces c' and e' formed at the insertion segment 105' are inclined to mate with
the inclination angles of the surfaces c and e.
[0031] In the second embodiment, the abutment surfaces a, b, c, e and a', b', c' and e'
are inclined with respect to a vertical plane. However, instead of the inclination
of the surfaces c, e and c', e', the abutment surfaces d and f of the frontward/rearward
protrusions 113a' and 113b' and corresponding abutment surfaces d' and f of the stationary
metal mold 101' can be slantingly formed. In the latter case, the abutment surfaces
a, b, d and f and a',b', d' and f' are inclined. Alternatively, all abutment surfaces
a through f and a' through f' can be inclined so as to provide a gradually thinner
wall and thinner groove or opening toward a bottom. With such arrangement, when the
gas venting unit 113' is inserted into the cruciform shaped opening or the unit insertion
recessed portion 111', the unit 113' can be easily inserted thereinto. For example,
when attention is drawn to the inclination surfaces a and b of the lateral positioning
protrusion 113c' and the inclination surfaces a' and b' of the cruciform shaped opening
111', since a distance between upper edgelines of the inclination surfaces a' and
b' is greater than a distance between lower edgelines of the inclination surfaces
a and b, the lateral positioning protrusion 113c' can be easily inserted into the
unit insertion recessed portion 111'. However, when the insertion is completed, the
gas venting unit 113' is brought into intimate contact with the unit insertion recessed
portion 111', similar to the first embodiment.
[0032] Next, a metal mold structure according to a third embodiment of this invention will
be described with reference to Fig. 3. The third embodiment is fundamentally similar
to the first embodiment, and therefore, the fixing means 119 is omitted. The third
embodiment has a cross-sectional structure of a gas venting unit 213 different from
that of the first embodiment, and has a configuration of a unit insertion recessed
portion defined by a T-shaped opening of a stationary metal mold 201 and a T-shaped
grooved portion of an insertion segment 205, which configuration is different from
that of the first embodiment.
[0033] The stationary metal mold 201 is formed with a T-shaped opening 203 similar to the
first embodiment. Into the T-shaped opening 203, the insertion segment 209 formed
with the T-shaped grooved portion 209 is inserted. However, the figure T of the T-shaped
groove portion 209 is oriented in a direction opposite to the first embodiment. At
confronting end faces of a head portion of the T-shaped grooved portion 209, abutment
surfaces a' and b' are defined, and at one side of the head portion thereof, abutment
surfaces c' and d' are defined as shown in Fig. 3.
[0034] For insertion of the insertion segment into the T-shaped opening 203, a leg portion
of the T-shaped grooved portion 209 is directed in a direction the same as a leg portion
of the T-shaped opening 203. As a result, a unit insertion recessed portion 211 is
defined, in which two major sides of a rectangle have inwardly protruded rectangular
notches so as to provide a generally H-shaped recess in a horizontal cross-section.
In this case, the insertion segment 205 has surfaces, which confront the leg portion
of the T-shaped opening 203, serving as abutment surfaces d' and f'.
[0035] The gas venting unit 213 has a horizontal cross-section the same as the generally
H-shaped unit insertion recessed portion 211. That is, the unit 213 is formed with
a pair of symmetrically arranged rectangular notches 213b and 213c at major sides
thereof, where abutment surfaces c, d, e, and f are defined. Further, by the formation
of the rectangular notches 213b and 213c, a T-shaped head portion 213a is provided,
where abutment surfaces a and b are defined. In the third embodiment, the external
contour of the gas venting unit 213 is substantially the same as the contour of the
unit insertion recessed portion 211, and therefore, the gas venting unit 213 can be
inserted into the unit insertion recessed portion 211.
[0036] The assembly of the gas venting unit 213 into the unit insertion recessed portion
211 can be made in a manner similar to that of the foregoing embodiment. In this case,
the positioning of the unit 213 in the lateral direction (X direction in Fig. 3) can
be achieved by the surface abutments between the abutment surfaces a, b and the abutment
surfaces a' and b'. Further, positioning in the frontward/backward direction (Y direction
in Fig. 3) is achievable by the surface abutments between the abutment surfaces c,
d, e and f of the gas venting unit 213 and the abutment surfaces c', d', e' and f'
of the insertion segment 205.
[0037] A metal mold structure according to a fourth embodiment will next be described with
reference to Fig. 4. The fourth embodiment would be substantially similar to the third
embodiment except for inclination of abutment surfaces similar to the second embodiment.
That is, as shown in Fig. 4, abutment surfaces a, b, d and f of a gas venting unit
213 are slanted with respect to a vertical plane so as to provide a gradually thin
wall thickness toward its bottom. Further, abutment surfaces a', b', d' and f' of
an insertion segment 205 are correspondingly slanted with respect to a vertical plane
so as to matingly receive the gas venting unit. Alternatively, abutment surfaces c
and e of the gas venting unit 213 can be slantingly formed, and abutment surfaces
c' and e' of the insertion segment 205 can be slanted correspondingly.
[0038] In the above described embodiments, the separate gas venting unit can be detachably
provided with respect to the stationary metal mold. However, the unit can be provided
detachably with respect to the movable metal mold.
[0039] Next, a jig for removing the gas venting unit from the metal mold will be described
with reference to Figs. 5 and 6. In the depicted embodiment, the jig is used for removing
the gas venting unit 113 of the first embodiment.
[0040] The jig 129 includes an inverted U-shaped or arch shaped jig body 131, a removing
bolt 137 movably extending through the jig body 131, and a nut 135 threadingly engageable
with the jig removing bolt 137. The jig body 131 includes two post portions 131 b
and 131c and a beam portion 131a bridging between the two post portions. The two post
portions 131 and 131c are spaced away from each other by a distance at least greater
than the lateral length of the lateral positioning protrusions 113a and 113b. At a
center portion of the beam portion 131a, formed is a through hole 131d having an inner
diameter greater than an outer diameter of a shaft portion 137b of the removing bolt
137.
[0041] The removing bolt 137 (a bolt-like moving means) has a head portion 137a having a
hexagonal shape and the shaft portion 137b integral with the head portion. The shaft
portion 137b has a length greater than a length of the post portions 131 b, 131c,
and an end portion of the shaft 137b is formed with a male thread threadingly engageable
with the threaded exhaust pipe attachment hole 117 formed at the top portion of the
gas venting unit 113. Further, the shaft portion 137b is formed with a male thread
engageable with the nut 135 (means for driving the bolt-like moving means 137) mounted
on the beam portion 131a. The nut 135 is rotatable about its axis but is stationarily
held on the beam portion 131a. With this state, the shaft portion 137b is passed through
the through hole 131d formed in the beam portion 131a. A washer 13 is interposed between
the nut 135 and the beam portion 131a.
[0042] Operation for removing the gas venting unit 113 from the metal mold by means of the
jig 129 will next be described. Firstly, the jig body 131 is mounted on the stationary
metal mold 101 in such a manner that the post portions 131b and 131c are positioned
outside the gas venting unit 113. Simultaneously, the bolt 121 of the fixing means
119 is unfastened, and the plate member 121 is moved within a stroke range defined
by a length of the elongated slot 123 so as to prevent mechanical interference between
the plate member 125 and the gas venting unit 113, so that the gas venting unit 113
becomes removable from the metal mold. Next, the removing bolt 137 is rotated, so
that the tip end of the bolt 137 is brought into engagement with the exhaust pipe
attachment hole 117 formed in the gas venting unit 113 as shown in Fig. 5. Then, the
nut 135 is rotated for upwardly moving the bolt 137 in the axial direction thereof,
to thereby removing the gas venting unit from the cruciform shaped opening 111.
[0043] As described above, since the tip end of the shaft portion 137b of the removing bolt
137 is engageable with the exhaust pipe attachment hole 117 of the gas venting unit
113, the gas venting unit 113 can be lifted in accordance with the upward movement
of the removing bolt 137, to thereby remove the unit 113 from the cruciform shaped
unit insertion recessed portion 111. Upon completion of the removal, the bolt 137
is disengaged from the exhaust pipe attachment hole 117 for maintenance, inspection
and replacement of mechanical components with respect to the gas venting valve and
the valve seat.
[0044] Next, a jig of another example will be described with reference to Fig. 7. The jig
129' employs a lever member (means for driving the bolt-like moving means) 140 utilizing
a principle of the lever and fulcrum. The lever member 140 lifts a removing bolt 137'
(bolt-like moving means) whose tip end portion 137b' engages the exhaust pipe attachment
hole 117 of the gas venting unit 113. In the fourth embodiment, an inverted U-shaped
jib body 131 is provided similar to the jig of the first example. The jig body 131
has a beam portion 131a whose central portion is formed with a through hole 131d through
which a shaft portion 137b' of the removing bolt 137' extends. The shaft portion 137b'
has a threaded portion only at a tip end portion thereof for engagement with the exhaust
pipe attachment hole 117 of the gas venting unit 113.
[0045] The lever member 140 serving as means for driving the bolt-like moving means 137'
has a L-shape configuration as shown in Fig. 7. The lever member 140 has an acting
arm 140a, a power-applied arm 140b and a fulcrum point 140c. The acting arm 140a is
formed with a notched recess portion 140d engageable with the shaft portion 137b'
and abuttable on a head portion 137a' of the bolt 137'. A opening width of the notched
recess 140d is larger than the diameter of the shaft portion 137b', and smaller than
the diameter of the head portion 137a'.
[0046] The acting arm 140a of the lever member 140 is positioned immediately below the head
portion 137a' and above the beam portion 131a of the jib body 131, and the shaft portion
137b' of the bolt 137' is inserted into the notched recess 140d. After the engagement
of the notched recess 140d with the shaft portion 137b', an upper surface of the acting
arm 140a abuts the lower surface of the head portion 137a', and the fulcrum point
140c abuts the upper surface of the beam portion 131a a of the jig body 131.
[0047] In operation, similar to the case shown in Figs. 5 and 6, the jig body 131 is mounted
on the stationary metal mold 101 in such a manner that the post portions do not ride
on the gas venting unit 113. Further, the fixing means 119 is unfastened from the
gas venting unit 113, and the tip end portion of the shaft portion 137b' of the removing
bolt 137' is brought into threading engagement with the exhaust pipe attachment hole
117 of the gas venting unit 113. Then, the notched recess portion 140d at the acting
arm 140a of the lever member 140 is engaged with the shaft portion 137b', and the
power applied portion 140b is depressed toward the stationary metal mold 101 as indicated
by an arrow shown in Fig. 7. By this depression, the acting arm 140a urges the head
portion 137a' of the bolt 137' upwardly, so that the shaft portion 137b' is also lifted
upwardly. Thus, the gas venting unit 113 engaged with the bolt 137' can be moved upwardly
whereupon the gas venting unit 113 can be removed from the cruciform shaped unit insertion
recessed portion 111. Instead of the employment of the lever member 140 for lifting
the bolt 137', a jack is available.
[0048] In the above description, the jig 129 or 129' as described above is used for removing
the gas venting unit of the first embodiment. However, the jig is also apparently
available for the metal mold structures according to the second through fourth embodiments.
[0049] The metal mold structure in the injection molding apparatus according to the present
invention provides the following advantages:
Firstly, since the insertion segment is separably and detachably provided with respect
to the T-shaped opening of the metal mold and since the gas venting unit is provided
detachably with respect to the unit insertion recessed portion defined by the T-shaped
opening and the T-shaped grooved portion of the insertion segment, maintenance and
inspection such as a removal of the molten metal flash and replacement works are facilitated
because of the easy detachment of the gas venting arrangement and the insertion segment
from the metal mold.
[0050] For defining the unit insertion recessed portion, for example, the T-shaped opening
and the T-shaped grooved portion are formed in the metal mold and the insertion segment,
respectively, and these T-shaped opening and grooved portion are combined together.
Thus, the unit insertion recessed portion can be easily formed, to thereby facilitate
manufacture of the metal mold structure.
[0051] Further, insertion work of the gas venting unit into the unit insertion recessed
portion can be easily achieved by forming the slanted surfaces which define the external
contour of the gas venting unit, which slanted surface provide a bottom-thin, top-thick
arrangement of the gas venting unit and by forming the corresponding slanted surfaces
at the unit insertion recessed portion which receives therein the gas venting unit.
[0052] Furthermore, according to the jig for removing the gas venting unit of this invention,
the gas venting unit can be easily removed from the unit insertion recessed portion
by mere rotation of the nut or by mere manipulation of the lever member. Therefore,
even if deformation occurs in the gas venting unit and the stationary or movable metal
mold, or even if molten flash is provided at a portion between the gas venting unit
and one of the stationary and movable metal molds, the gas venting unit can be easily
detached. Accordingly, maintenance, inspection and replacement work to the gas venting
unit can further be facilitated to thus improve working efficiency.
[0053] While the invention has been described in detail and with reference to specific embodiments
thereof, it would be apparent to those skilled in the art thatvari- ous changes and
modifications may be made without departing from the spirit and scope of the invention.
1. A metal mold structure in an injection molding apparatus, the metal mold structure
including a metal mold in which a mold cavity is formed, and a gas venting arrangement
in which a gas vent passage is communicated with the mold cavity and the gas vent
passage is selectively shut off from an exterior by means of a gas vent valve means;
the metal mold structure comprising:
a metal mold (101,101',201) whose one surface defines a parting face and formed with
an upper opening (103,203) at a side of the parting face;
a gas venting unit (113, 113',213) provided separate from the metal mold and having
a given external contour, the gas vent valve means being disposed in the gas venting
unit;
an insertion segment (105,105',205) fittingly insertable into a part of the upper
opening, a unit insertion recessed portion (111,111',211) being defined by the upper
opening and the insertion segment when the insertion segment is inserted thereinto,
the unit insertion recessed portion having an configuration substantially coincident
with the external contour of the gas venting unit for receiving the unit into the
unit insertion recessed portion; and
a fixing means (119) for fixing the gas venting unit in the unit insertion recessed
portion.
2. The metal mold structure according to claim 1, wherein the insertion segment (105,
105', 205) is formed with an upper grooved portion (109,209), a combination of the
upper grooved portion and the upper opening defining the unit insertion recessed portion.
3. The metal mold structure according to claim 1 or 2 wherein the gas venting unit
has at least two symmetrical abutment surfaces (a,b or c,e or d,f) extending obliquely
with respect to a vertical plane so as to provide a top thick bottom thin mass, the
symmetrical abutment surfaces defining a part of the external contour of the gas venting
unit. and wherein the unit insertion recessed portion has at least two symmetrical
surfaces (a'- b' or c',e' or d',f') each having inclination angle equal to an inclination
angle of the corresponding two symmetrical abutment surfaces.
4. The metal mold structure according to claim 1 or 2, wherein the gas venting unit
(113, 113') has a cruciform shape in horizontal cross-section, and wherein the unit
insertion recessed portion (111, 111') has a corresponding cruciform shape in horizontal
cross-section.
5. The metal mold structure according to claim 1 or 2, wherein the gas venting unit
(213) has a generally H-shape in horizontal cross-section, and wherein the unit insertion
recessed portion (211) has a corresponding H-shape in horizontal cross-section.
6. A combination comprising a metal mold structure in an injection molding apparatus,
and a jig device, the metal mold structure comprising:
a metal mold (101,101',201) whose one surface defines a parting face and formed with
an upper opening (103,203) at a side of the parting face, the metal mold being formed
with a mold cavity and a gas vent passage in communication therewith;
a gas venting unit (113,113',213) provided separate from the metal mold and having
a given external contour, the gas venting unit disposing therein a gas vent valve
means which selectively shuts off the gas vent passage and having a top portion formed
with an exhaust pipe attachment hole (117);
an insertion segment (105,105',205) fittingly insertable into a part of the upper
opening, a unit insertion recessed portion (111,111',211) being defined by the upper
opening and the insertion segment when the insertion segment is inserted thereinto,
the unit insertion recessed portion having an configuration substantially coincident
with the external contour of the gas venting unit for receiving the unit into the
unit insertion recessed portion; and
a fixing means (119) for fixing the gas venting unit in the unit insertion recessed
portion; and
the jig device being adapted for removing a gas venting unit from the unit insertion
recessed portion of a metal mold structure, and comprising:
a jig body (131) mounted on the metal mold at a position in confrontation with the
exhaust pipe attachment hole (117), the jig body being formed with a through hole
(131d) alignable with the exhaust pipe attachment hole;
a bolt-like moving means (137, 137') comprising a head portion (137a, 137a') and a
shaft portion (137b, 137b') integral therewith and formed with a threaded portion
at least at a tip end portion thereof, the shaft portion being passable through the
through hole (131 d) and the threaded portion being threadingly engageable with the
exhaust pipe attachment hole; and
means (135,140) for driving the bolt-like moving means, the driving means being positioned
between the bolt-like moving means and the jig body and being driven for upwardly
moving the bolt-like moving means, to thereby lift the gas venting unit engaged with
the bolt-like moving means for removing the gas venting unit from the unit insertion
recessed portion.
7. The combination according to claim 6, wherein the shaft portion (137b) of the bolt-like
moving means is formed with thread along its length, and wherein the driving means
comprises a nut (135) rotatable about its axis and unmovable in an axial direction
thereof, the nut being threadingly engageable with the thread portion for upwardly
lifting the bolt-like moving means together with the gas venting unit by the rotation
of the nut.
8. The combination according to claim 6, wherein the driving means comprises a L-shaped
lever member (140) having an acting arm (140a) engageable with the shaft portion (137b')
and abuttable on the head portion (137a'), a power applied portion (140b) and a fulcrum
portion (140c) mounted on the jig body (131), the acting arm (140a) urging the head
portion upwardly upon power application to the power-applied portion (140b).
9. The combination according to claim 6, wherein the jib body (131) comprises;
a pair of post portions (131b, 131c) upstandingly mounted on the metal mold and positioned
offset from the gas venting unit inserted in the unit insertion recessed portion;
and
a beam portion (131a) bridging between the pair of post portions. the through hole
being formed in the bridge portion and the driving means being mounted on the beam
portion.