JPS6147621B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is particularly useful for the production of hollow body cores, and can be further developed to be used for the production of solid cores, and is a novel centrifugal core forming method that can be applied to foundry cores in general. The purpose is to provide a method.

As shown in Fig. 1, for example, in centrifugal force casting of a cast iron pipe 1 having a socket at the end, the end of the centrifugal force casting mold 2 is provided with a hollow body in order to obtain the required socket shape. It is necessary to set child 3. In general, when casting products, including not only those for this type of centrifugal force casting but also ordinary pouring casting, various hollow body cores are used depending on the shape of the product. This is extremely common.

By the way, looking at the manufacturing method of such a hollow body core for casting, the conventional method is as shown in Figure 2.
A mandrel 5 is set in the center of a corer (centering mold) 4 formed into a suitably split mold, and in this state, the gap between the corer 4 and the mandrel 5 is filled with molding sand 6 while being tamped. It was customary to make the mold using the same method.
However, according to this conventional core molding method,
The tamping operation requires time and effort, and especially when molding a core with a complex external shape, the work becomes extremely complicated, and the sand is not evenly filled to the inner details of the corer 4, resulting in dimensional accuracy. There was also a lack of quality, and there were still many points that needed to be improved in terms of both productivity and quality.

In view of these circumstances, the present invention has succeeded in developing an innovative core-forming method that can easily and quickly manufacture a hollow core having any complex external shape. The feature of this method is that thermosetting molding sand is put into the inner surface of a hollow corer that is rotated around the axis and heated in advance, and the molding sand is formed into a hollow core by centrifugal force. In the formed state, flame or hot air is injected onto the inner surface of the foundry sand to solidify it, and after solidification, the core is taken out from the corer.

The present invention will be explained below based on the illustrated embodiments.
FIG. 3 shows an example of a test device for carrying out the method of the present invention. In this device, an existing metal frame 7 for centrifugal force casting is conveniently used, and a hollow centering device 8 according to the present invention is appropriately fixed to one end of the metal frame 7. The centering device 8 is connected and attached via a tool 9, and the centering device 8 is driven to rotate integrally with the metal frame 7 about its horizontal axis by a plurality of pairs of rotating rollers 10 that support the metal frame 7. This illustrated device is, of course, just an example of a simple testing device, and in actual industry, it is reasonable to adopt a means of directly rotating the corer 8 without using the metal frame 7. For example, as shown in FIG. 5, a centering device 8 is removably fixed to a turntable 12 that is rotatably supported by a shaft 11 that is linked to a rotational drive body such as a motor (not shown), and An example may also be a device that directly drives the device 8 to rotate around its vertical axis. In any case, the rotation means of the centering device 8 and the direction of its rotation axis are free.

According to the centrifugal core forming method of the present invention, a sand hopper or the like is moved onto the inner surface of the hollow corer 8, which is rotated around its axis by appropriate means, as shown in FIGS. 4 and 5. Foundry sand 14 is introduced from a freely disposed sand supply means 13, and is applied to the inner surface of the corer 8 by centrifugal force to form it into a hollow core shape. The molding sand 14 is shaped by centrifugal force in exactly the same manner as the centrifugal casting method, and in the method of the present invention, instead of the molten metal used in the centrifugal casting method, casting sand is introduced. It is. Therefore, if the rotation speed of the corer 8 is set so that the required centrifugal force acts on the foundry sand 14,
A hollow core with an outer surface that conforms to any inner surface shape of the corer 8, which has been previously formed into a desired shape, is molded, and the thickness of the core at this time depends on the amount of molding sand 14 input. and can be easily adjusted. actual,
In the centrifugal force core forming method of the present invention, the magnitude of the centrifugal force required to form the hollow core uniformly filled with the foundry sand 14 is in the range of GNo. 5 to 100, and more generally In general, G No. 10 to 40 is sufficient. Within this range, the poorer the fluidity of the foundry sand 14 and the more complex the internal shape of the corer 8, the higher the GNo. value is set. In addition, core remover 8
If you apply vibration at the same time while rotating,
It is also possible to reduce the required GNo. value to some extent.

In the centrifugal force core making method of the present invention, a core (foundry sand) formed by centrifugal force on the inner surface of the corer 8 as described above is used.
is then solidified into the molded state in the corer 8, and after the core has solidified, it is taken out from the corer 8 and used as a core for casting.
That is, the foundry sand 14 is quickly solidified in the centering device 8 from the time of charging to after the completion of charging by an appropriate solidifying means described later, and is solidified into a predetermined molded state by centrifugal force.

In addition, in the method of the present invention, after the core is solidified, it is taken out from the corer 8 and used, so when manufacturing a core with a complicated shape, it is necessary to It is necessary to form the centering device 8 into a split mold that is divided into axial and radial directions. For example, in a centering device with an inner surface shape as shown in FIG.
It is detachable at the radial dividing surface A via a fastener 15, and is also formed into a split mold having an appropriate number of dividing surfaces (not shown) in the axial direction. Also, core remover 8
It is preferable to apply a mold release agent to the inner surface of the corer 8 in advance in order to facilitate the separation of the two cores and to prevent the core from losing its shape when the core is taken out. If this mold release agent exhibits good performance, when manufacturing cores with simple shapes such as cylinders, the core can be removed from the corer 8 without using a split mold. It is also possible to take it out by pulling it out.

According to the centrifugal force core forming method of the present invention, the outer surface shape of the hollow core to be molded can be freely changed in addition to that illustrated in FIG. 4. For example, the planar shape is schematically shown in FIG. 6. (16, 17, 18 in the diagram)
is a core, and B, C, and D are the dividing surfaces of the centering device).It can be easily manufactured with any external shape.
By filling the hollow portion with foundry sand again, a solid core can also be manufactured by the method of the present invention.
In the centrifugal core forming method of the present invention, the corer 8
is long in the axial direction, and has 2 holes on its inner surface.
Needless to say, by intermittently forming a core molding surface of one or more core molding surfaces, it is possible to remove a plurality of cores at the same time.

The foundry sand 14 used in the method of the present invention and its solidification means in the corer 8 will be explained below.
First, as the foundry sand 14, any type of sand that is generally used for making cores can be used.

Among these, a so-called hot box type foundry sand which is blended with a thermosetting resin as a binder will be described as a preferred specific example for use in the method of the present invention.As a representative example of this type of foundry sand, An example is general shell sand, which uses silica sand as an aggregate and mainly uses a phenol resin (in addition, a resin and a hardening agent may be added) as a binder. As is well known, this hot box type foundry sand has the property of being rapidly sintered and solidified by heating to an appropriate temperature.

Therefore, also in the centrifugal core forming method of the present invention,
It is sufficient to adopt heating means as a means for solidifying this type of foundry sand, and the simplest and basically
itself at an appropriate temperature (usually 250~250°C for shell sand)
350° C.), thereby making it possible to easily and quickly solidify the core (foundry sand) formed in the corer 8. For example, as foundry sand 14, shell sand (6# silica sand + 3%
According to an example of centrifugally cored sand with a thickness of 20 to 40 mm using corer 8 (phenol resin) and preheated to 250°C, a bending strength of 60 Kg/2 minutes was achieved by sintering for 2 minutes. It is possible to produce cores solidified to ^cm2 .

Next, another heating means effective as a means for solidifying or promoting solidification of the hot box type foundry sand will be described with reference to FIGS. 7 and 8. The heating means shown in FIG. 7 inserts an injection pipe 19 into the hollow part of the corer 8 during or after the molding of the foundry sand 14 is completed, and from this injection pipe 19 a flame is applied to the inner surface of the foundry sand 14. Alternatively, hot air 20 is injected. Also the 8th
Similarly, the heating means shown in the figure is used to seal the inside of the corer 8 by placing a sealing lid 21 on the open end of the corer 8 during or after the molding of the foundry sand 14 is completed. Pressurized hot air 20 is blown into the inner surface of the foundry sand 14 from the pouring pipe 19', and on the other hand, the corer 8 is previously provided with a large number of ventilation holes 22 such as vent plugs communicating with the outside, and the pressurized hot air 20' is blown into the casting sand 14. sand 1
4 and is discharged to the outside. Flame or hot air 20 is applied to the inner surface of these foundry sands 14.
The heating means that injects the molding sand 14 and the heating means that allows the pressurized hot air 20' to pass through the molding sand 14 can be effective means for solidifying the molding sand 14, respectively.
In addition, when used in combination with a means for preheating the corer 8 itself, it becomes a means for significantly promoting solidification.

Although the molding sand 14 used as the binder is described above, the concept of the present invention can be similarly applied to the use of other molding sands, such as self-hardening molding sand, etc. When using other foundry sand, it is sufficient to take appropriate solidifying means depending on the type of foundry sand, such as blowing in a reactive gas depending on the blended binder.

As explained above, the centrifugal force core forming method of the present invention involves introducing foundry sand into a rotating hollow corer, forming it into a hollow core by centrifugal force, and
The molded core is solidified and the molded and solidified core is taken out and used. According to the method of the present invention, a mandrel is not required when molding a hollow body core, and there is no need for any complicated tamping work. This makes it possible to easily and quickly produce a core that is compatible with this and has an evenly filled outer surface shape. Therefore, the method of the present invention significantly improves both productivity and quality in the production of cores, especially hollow body cores, and furthermore, if the hollow part is separately filled with foundry sand after the hollow body core is manufactured, This makes it possible to easily produce solid cores, and the present invention can be said to be an innovative core-making method that can be applied to all casting cores.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a centrifugal casting mold showing an example of the usage state of a hollow body core, Fig. 2 is a sectional view showing a conventional hollow body core manufacturing method, and Fig. 3 is a sectional view of a centrifugal casting mold showing an example of the usage state of a hollow body core. 4 is an enlarged cross-sectional view of the main part of FIG. 3; FIG. 5 is a partially cutaway front view showing an example of a practical device for carrying out the present invention;
Figures 6a, b, and c are explanatory views showing examples of planar shapes of cores that can be manufactured by the method of the present invention, and Figures 7 and 8 are sectional views showing core solidifying means in the corer, respectively. It is. 8...Hollow corer, 14...Casting sand (core).

Claims (1)

[Claims] 1. Thermosetting molding sand is poured into the inner surface of a hollow corer that is rotated around the axis and heated in advance, and the molding sand is formed into a hollow core by centrifugal force, and
A centrifugal core making method characterized by injecting flame or hot air onto the inner surface of the foundry sand in its formed state to solidify it, and after solidifying, taking out the core from a corer.