JP5551456B2 - Molding method for centrifugal casting core - Google Patents

Description

  The present invention relates to a method for molding a core for centrifugal casting, and more particularly to a molding method from molding a core with a mold to taking out the core from the mold.

Centrifugal casting has been used as a method for producing cast iron pipes. As shown in FIGS. 4 to 5, this is because a core 70 is attached to one end of a cylindrical mold M (mold) and the mold M is rotated at a high speed. It is a casting method that pours.
The poured molten metal a is attached to the inner surface of the mold by receiving a centrifugal force, and flows between the mold M and the core 70 and also contacts the outer surface of the core 70. Then, after the molten metal a is cooled and solidified into a pipe shape, the pipe (cast iron pipe P) is extracted from the mold M.
At this time, the inner surface of one end of the cast iron pipe P extracted from the mold is completed in the same shape as the outer surface of the core 70 attached to the mold.

The core is molded using a core mold as shown in FIG.
The core mold has a structure in which the inner frame 72 is fitted inside the outer frame 71, and a space (filling space 73) is formed between the inner surface of the outer frame and the outer surface of the inner frame. After filling the filling space 73 with sand mixed with resin from above the core mold, the resin is cured and the core 70 having the same shape as the filling space 73 is molded. At this time, a flange 75 protruding in the outer diameter direction of the core is formed on the molded core 70. (See Figure 7 (a))
Here, as shown in FIG. 8, the outer frame 71 is formed by combining two split dies 74 with a split surface 76. The split mold 74 is a half-shaped member formed by vertically dividing the outer frame 71 into two, and a split surface that divides the outer frame vertically in half is called a split surface.

When the molding is completed, the outer frame 71 is moved upward and separated from the inner frame 72. At that time, the core 70 is supported by meshing with the concave and convex portions on the inner surface of the outer frame 71 and moves together with the outer frame above the inner frame. (See Fig. 7 (b))
Next, after placing the outer frame 71 on the floor, it is divided vertically by the split surface 76 into two split molds 74, and the two split molds are horizontally moved in opposite directions so as to be separated from each other. To go. Then, the engagement between the inner surface of the outer frame and the outer surface of the core gradually decreases, and finally the core 70 and the outer frame 71 (split mold 74) are completely separated, and the core is taken out. (See Fig. 7 (c) to (d))
At this time, since the core is not supported by meshing with the outer frame (split mold), it falls if there is no other support. In order to prevent the fall, it is necessary to newly support the core, for example, by supporting the inner surface of the core with the arm h. (See Patent Document 1)

Japanese Utility Model Publication No. 4-64445

  Until now, the outer frame 71 extracted on the inner frame together with the core has been placed on the floor and then vertically divided by the split surface 76 to take out the core 70. In this case, since the lower end of the core 70 is above the lower end of the outer frame 71 in contact with the floor surface, when the outer frame 71 is divided and the core is taken out, the core 70 falls to the floor surface, The core could be damaged.

It is not preferable in terms of casting quality to cast using a core with a flaw because the flaw may appear on the inner surface of one end of the cast iron pipe.
In order to prevent the core from being damaged, machines and people have supported the core to prevent the core from falling when the core is removed from the outer frame. This has led to complex equipment and increased burden on the workers.
An object of the present invention is to provide a molding method that reduces the complexity of equipment and the burden of work and prevents the core from being damaged.

  In order to solve the above-described problems, the molding method of the present invention forms an outer frame having a circular hole-shaped inward molding surface by combining a split mold having an arcuate surface with a split surface, and inside the outer frame. The inner frame with the outward molding surface is fitted from below, the receiving portion provided at the lower part of the outer molding surface of the outer frame is aligned with the protrusion provided at the lower part of the outer molding surface of the inner frame, and extends in the circumferential direction. A filling space is formed between the inward molding surface with grooves or ridges and the outward molding surface with a draft angle for extracting the molded core upward, and sand is poured into the filling space from above. Fill and mold the core, and after the molding is completed, the core and outer frame that engage with the outer frame with grooves or ridges are integrated and pulled out on the inner frame, then the outer frame is inverted, and the upper surface of the outer frame With the facing down, the split mold is separated by a split surface in the radial direction of the core, the outer frame is separated from the core, and the core is removed. Thing was the in it.

  According to this method, since the outer frame is divided with the core sand injection surface (end surface on the flange portion 75 side) facing down, the sand input surface of the core is already grounded, and the outer frame and Even if the core does not fall when the core is separated, or even if the core falls, the sand throwing surface (end surface on the flange portion 75 side) of the core becomes the grounding surface, and the grounding area increases. It is hard to break and is hard to be damaged. In addition, even if the sand input surface (end surface on the flange portion 75 side) that becomes the ground contact surface is damaged, this portion does not come into contact with the molten metal during casting. Will not be adversely affected.

  A pair of rotating shafts projecting to the outer periphery of the outer frame when the core and the outer frame, which are engaged with the outer frame by grooves or ridges, are integrated with each other and pulled out on the inner frame to reverse the outer frame. If the outer frame is supported at, the outer frame can be reversed smoothly.

  If the rotation axis is cylindrical or columnar and the axis line passes through the center of gravity of the outer frame, the outer frame can be reversed with a lighter force around the rotation axis.

  According to the present invention, as described above, the outer frame is reversed during core molding, and further, the rotating shaft that is supported at the time of the reversal is provided on the outer frame. Therefore, damage to the core can be easily prevented.

It is a longitudinal cross-sectional view showing the state in the core shaping | molding in embodiment of this invention. It is a top view of an outer frame equally. FIG. 6 is a longitudinal sectional view showing a molding operation after completion of core molding. It is explanatory drawing of centrifugal force casting. It is a cross-sectional detail drawing of a receiving part at the time of centrifugal force casting. It is a perspective view of a core and a holder. It is explanatory drawing of the conventional core molding method. FIG. 6 is a plan view of a conventional outer frame.

An embodiment of the present invention will be described with reference to FIGS.
The core is an object that forms the inner surface shape of one end (receiving portion) of the cast iron pipe P. As shown in FIGS. 4 to 6, the mold and the shaft center are aligned with the metal holder 80. , Attached to one end of the mold M, and used for casting a cast iron pipe.
When the mold with the core set at one end is rotated and molten metal a is poured from the other end to the inner surface of the mold, the molten metal a also flows between the inner surface of the mold and the outer surface of the core, forming one end (receiving part) of the cast iron pipe. To do. (See Figure 5)

The core 40 is molded by using a core mold composed of the outer frame 1 and the inner frame 20.
FIG. 1 is a longitudinal sectional view showing a state in which a core is being molded. A state in which a cylindrical inner frame 20 is inserted inside a cylindrical outer frame 1 and fitted under the two frames. Represents. Sand is poured into a space (filling space 41) formed between the outer surface of the inner frame and the inner surface of the outer frame in the fitted state. The sand is coated with a resin in advance, and as the curing reaction of the resin proceeds, the filled sand hardens and the core 40 is molded.

The upper side of the filling space 41 is open, and sand is poured into the opening from above.
The lower side of the filling space 41 is closed by the fitting of the outer frame 1 and the inner frame 20, and no sand leaks from here during filling.
The inner surface of the outer frame 1 that forms the filling space 41 has a large number of irregularities that protrude or dent in the radial direction. These ridges extend in the circumferential direction and circulate around the ridge 8 that protrudes inward or recessed outward. A groove 7 is formed. Thus, the inner surface (inward molding surface 9) of the outer frame has a complicated shape complicated in the radial direction.
Since the sand flows into the ridges 8 and the grooves 7 and is filled without a gap, the core 40 to be molded is molded in the same shape as the filling space 41. For this reason, the outer surface of the core 40 meshes with the inner surface (inward molding surface 9) of the outer frame 1 without a gap.

FIG. 2 is a plan view of the outer frame.
The outer frame 1 is formed by combining a pair of split molds 2 and 2 ′ with a split surface 10. The inner surface of the outer frame 1 has a circular hole shape formed by combining the two split molds 2 and 2 'arcuate surfaces 90 and 90'. As described above, the surface of the outer frame 1 has a protrusion 8 extending in the circumferential direction. And a groove 7 is formed.
The split molds 2 and 2 'are arcuate shapes in which the cylinder is divided in half in the axial direction, and the split molds 2 and 2' are fixed with a removable fixture (not shown). Match the faces together.

A single rotating shaft 4, 4 ′ protruding outward is firmly attached to the center of the outer peripheral arcs 91, 91 ′ of the split molds 2, 2 ′.
When the two split molds 2 and 2 ′ are combined with the split surface 10 to form the outer frame 1, the shaft centers 11 and 11 ′ of the rotary shafts 4 and 4 ′ attached to the split molds coincide with each other. At that time, the extension lines of the shaft centers 11 and 11 ′ pass through the center of gravity of the outer frame 1.
One end of each of the rotating shafts 4 and 4 ′ is firmly attached to the outer periphery of the split molds 2 and 2 ′, and the other end of the disk 5 having a larger diameter than the rotating shafts 4 and 4 ′ is welded. The disk 5 prevents the suspension from coming off the rotation shaft when a suspension such as a wire 50 is hung on the rotation shaft 4 or 4 ′.

At the lower end of the inner surface of the outer frame 1 (split molds 2 and 2 ′), there is a dent recessed outward in the radial direction, and this dent circles in the circumferential direction and is fitted with the inner frame 20. Is forming. When the inner frame 20 is inserted into the inner side of the outer frame 1 from below, the receiving portion 6 hits a protrusion 21 provided at the lower end of the outer surface of the inner frame 20. (See Fig. 3 (a))
When the outer frame 1 and the inner frame 20 are fitted, the receiving portion 6 and the projection 21 are fitted with a narrow gap, so that sand does not enter the fitting portion.
The split surface 10 is smoothly finished so as not to cause a gap through which sand leaks when the two split molds 2 and 2 ′ are combined and tightened with a metal fixture (not shown).

The protrusion 21 at the lower end of the outer surface of the inner frame 20 is a step protruding outward in the radial direction, and this step goes around in the circumferential direction. When the outer frame 1 is fitted onto the inner frame 20 from above, the receiving portion 6 on the inner surface of the outer frame and the protrusion 21 are fitted. (See Fig. 3 (a))
The outer surface of the inner frame 20 is a flat outward molding surface 22 except for its lower part. Further, the outer shape of the inner frame 20 has a gentle taper shape in which the outer diameter of the upper end of the inner frame is slightly smaller than the outer diameter of the lower portion of the inner frame in order to take the draft of the core after molding.
The lower end of the inner frame 20 is fixed to the upper surface of the circular plate-like pedestal 30 with bolts (not shown).

FIG. 3 is a view for explaining how to take out the core after completion of the core molding.
After filling and filling the filling space 41 with sand, and after the resin mixed in the sand has been cured, the core 40 is taken out.

First, as shown to Fig.3 (a), the wire 50 is hung on each of a pair of rotating shafts 4 and 4 ', and each wire is pulled up simultaneously with a crane etc. As shown in FIG. If it does so, the outer frame 1 and the core 40 will be lifted up integrally, leaving the inner frame 20 and the base 30 below.
This completes the work of removing the outer frame 1 and the core 40 from the inner frame 20.

Next, the outer frame 1 integrated with the core 40 is half-rotated by a human hand around the substantially horizontal rotating shafts 4 and 4 ′ while being lifted. Thus, the upper surface of the outer frame 1 is directed downward, and the inversion of the outer frame 1 is completed.
At this time, since the core 40 and the outer frame 1 are fitted in the protrusions 8 and the grooves 7, the core 40 does not come off from the outer frame 1 or fall off.
As shown in FIG. 3 (b), the outer frame 1 integrated with the core 40 is moved by the operation of a crane or the like with the upper surface of the outer frame 1 facing downward (inverted state). Lower it on the table 60. At this time, the division direction of the split molds 2 and 2 ′ and the rotation direction of the roller are matched.
Thus, the end surface of the core on the sand input side (the flange portion 42 side) is in contact with the roller base 60 or faces the roller base 60 with a slight gap.

  Next, a fixing tool (not shown) that fixes the split molds 2 and 2 'is removed, the fixing is released, and the split molds 2 and 2' can be divided by the split surface 10, and then the split mold 2 and 2 ′ are horizontally moved on the roller table 60 in opposite directions (directions in which the split surfaces 10 are separated from each other).

When the split molds are separated from each other, the meshing between the outer surface of the core and the inner surface of the split mold (outer frame) gradually decreases, and finally the meshing is lost, and the core 40 is supported by the split molds 2 and 2 '. Disappears.
When the core 40 is no longer supported by the split molds 2 and 2 ′, if the end surface of the core 40 on the flange portion 42 side is in contact with the upper surface of the roller base 60, a roller is used instead of the split molds 2 and 2 ′. The base 60 supports the core. (See Fig. 3 (c))
Further, when the core 40 is no longer supported by the split molds 2 and 2 ′, and there is a gap between the end surface of the core 42 on the flange portion 42 side and the upper surface of the roller base 60, the core on the upper surface of the roller base The core 40 falls until the end surface on the side of the flange portion 42 contacts, and then the upper surface of the roller base 60 supports the core 40.

  Finally, each split mold 2, 2 'is moved to a position where it does not interfere with the removal of the core 40. This completes the removal of the core 40 from the outer frame 1, completes the molding process of the core, and conveys the removed core to the next step.

1,71 Outer frame
2, 2 ', 74, Split mold 4, 4' Rotating shaft 5 Disc 6 Receiving part 7 Groove 8 Projection 9 Inward molding surface 10, 76 Split surface 11, 11 'Axes 20, 72 Inner frame 21 Projection 22 Outward molding surface 30 Base 40, 70 Core 41, 73 Filling space 42, 75 Head portion 50 Wire 60 Roller base 80 Holder 90, 90 'Arc surface 91, 91' Outer arc P Cast iron pipe M Mold a Molten h arm

Claims (1)

A split mold having an arc surface is combined with the split face to form an outer frame with a circular inward molding surface, and an inner frame with an outward molding surface is fitted into the outer frame from below, The receiving part provided on the lower part of the inward molding surface of the outer frame and the protrusion provided on the lower part of the inner molding surface of the inner frame are combined and molded with an inward molding surface with grooves or ridges extending in the circumferential direction. A filling space is formed with the outward molding surface with a draft angle for extracting the core upward, sand is poured into the filling space from the top, and the core is molded. Alternatively, the core and outer frame that engage with the outer frame with the ridges are integrated and pulled out on the inner frame, and then the split mold is separated by a split surface in the radial direction of the core to separate the outer frame from the core. A method of molding a core for centrifugal casting to take out the core,
After the core has been molded, the core and outer frame that engage with the outer frame with grooves or ridges are integrated into the outer frame , and then extracted onto the inner frame, and then a pair of cylindrical or columnar rotating shafts that project to the outer periphery of the outer frame Rotate the outer frame that is supported by the center axis of the rotating shaft through the center of gravity of the outer frame halfway around the rotating shaft, invert the core and outer frame together, and turn the upper surface of the outer frame downward And then separating the outer mold from the core and taking out the core by separating the split mold in the radial direction of the core, and taking out the core.

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