JPH023656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In metal casting, a method has long been used in which a desired shape is formed by a combination of a master mold set in a mold and molding sand filled and compressed around the master mold. In a typical casting process, the pattern is then removed from the sand and molten metal is poured into the cavity occupied by the pattern, shaping the metal to match the shape of the pattern.

In recent years, new methods have been used to form the master mold from a material that converts to gas when it comes into contact with molten metal. With such masters it is possible to use masters with complex shapes, for example internal passages or cavities, since it is not necessary to extract the master from the sand before casting the molten metal.

As a means of filling molding sand into the cavities of the master mold, there is a method in which air is introduced into the bottom of the mold and is caused to rise through the sand, and the force of the air flow forces the sand into the cavity of the master mold. Traditionally used. Although this method is effective for relatively simple prototypes, it is not completely satisfactory when the prototype has a large number of internal passages, cavities, etc.

In the present invention, when filling all the cavities and internal passages of the mold with sand, the mold containing the molding sand and the mold is given an acceleration greater than the acceleration due to gravity to the sand therein. Provided is a method of filling foundry sand by applying vibrations of a certain frequency and amplitude. This vibration action causes the sand to
It flows like a fluid and can completely penetrate even the smallest cavities and passages in the original model. After the formwork containing the pattern and sand has been vibrated for a sufficient period of time to allow the sand to enter all openings in the pattern, a second step is to apply vibrations to the sand to give it an acceleration somewhat lower than that due to gravity. Reduce power. This second stage of vibration effectively compacts the sand in place so that it remains in place when molten metal is later poured into the formwork.

The accompanying figures diagrammatically illustrate the steps of the method of the invention. Referring to FIG. 1, formwork 10
The prototype 11 is shown suspended within the formwork by the suspension means 12. Although the master form may be formed of any conventional material, the method of the present invention is useful when applied to complex shaped master forms that cannot be pulled out of the sand in the formwork prior to pouring molten metal. It is particularly useful for Such a complex archetype is
It is formed from materials such as polyurethane foam or styrofoam that gasify when contacted by molten metal.

The complex shape of the original shape 11 has a cavity 13 and a passage 1.
4 (which may be a blind end passage).

This original form is suspended in a predetermined position as shown in FIG. 1, and sand is introduced by conveyor 16 to completely fill the form. The formwork filled with sand is then placed on the vibrating device 17. The vibrating device 17 consists of a base 18, a table 19 suspended on the base by a spring 20, and a plurality of oscillators 21 suspended from the bottom surface of the table 19. Each oscillator 21
consists, for example, of an electric motor 22 with a shaft on which an eccentric weight 23 is mounted, the effective force of which can be varied from zero to a maximum so as to be able to vary the amplitude of the vibrations as desired. can. Preferably, it is of the type disclosed in US Pat. No. 3,358,815.

After the formwork 10 is clamped to the platform 19 by the clamps 24, the oscillator 21 is energized to apply a vibratory force to the formwork and its contents at an acceleration higher than the acceleration of gravity. Gravitational acceleration can be calculated by the formula S×F ² /70400, where S=amplitude in inches and F=frequency per minute. For example, frequency 3600 vibrations per minute,
For an amplitude of 0.007in (0.178mm), an acceleration of 1.29G is exerted on the formwork and its contents. This acceleration causes sand to flow into the cavities 13 and holes 14 (even if they are blind) until they are completely filled. Moreover, even if the holes are even narrower, they are completely filled with sand. After applying vibrations with an acceleration above the gravitational acceleration for several minutes, the amplitude of the vibrating device is reduced, thereby reducing the acceleration to a level below the gravitational acceleration. That is, the frequency of 3600 vibrations per minute is maintained, and the amplitude is reduced to, for example, 0.0045in.
(0.114mm), the acceleration will decrease to 0.92G. Vibrating for a few minutes at an acceleration of less than 1 G compacts the sand into its own position, so it stays in place and doesn't collapse when molten metal is poured into the mold.

FIG. 4 shows the step of injecting molten metal into the mold. Molten metal is injected into the master mold through a short passage. When the molten metal contacts a foam master, such as polyurethane foam, the master is gasified and dissipated as a gas, and the metal is cast into the shape of the master. The metal is then allowed to cool. Fifth
As shown, the metal completely fills the space occupied by the foam master, creating a true replica of all cavities and passageways in the master.

The method of the invention is particularly suitable for aluminum casting of engine cylinder blocks. According to the method of the invention, a master cylinder block with coolant passages and other cavities and passages can be formed and the engine cylinder block can be cast accordingly.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing a mold with a mold suspended inside it, Figure 2 is a similar view to Figure 1, showing the introduction of molding sand into the mold, and Figure 3 is a vibration device. Partial sectional view of the formwork and prototype fixed above, No. 4
The figure is a cross-sectional view showing the operation of injecting molten metal into the mold, and FIG. 5 is a cross-sectional view showing the metal cast into the original shape. 10...Formwork, 11...Prototype, 13...Cavity,
14... Passage, 17... Vibration device, 21... Oscillator.

Claims (1)

[Claims] 1. In the casting process, the step of introducing molding sand into a mold containing a master mold, and the vibration of a frequency and amplitude that imparts an acceleration higher than the acceleration of gravity to the mold and its contents. applying to the mold to fill all openings in the master mold with foundry sand, and applying vibrations of a frequency and amplitude such that the mold and its contents experience an acceleration lower than the acceleration of gravity. tamping the foundry sand into respective predetermined positions. 2. The vibrations that cause the formwork and its contents to have an acceleration higher than the gravitational acceleration are substantially vertical vibrations, and the vibrations that give the formwork and its contents an acceleration that is lower than the gravitational acceleration The foundry sand filling method according to claim 1, wherein vibration is performed in a vertical direction. 3. The foundry sand filling method according to claim 1, wherein the master mold is formed of a material that gasifies when contacted by molten metal. 4. said master form is formed of a material that gasifies when contacted by molten metal, and said vibrations imparting an acceleration greater than the acceleration of gravity to the formwork and its contents are substantially vertical vibrations; 2. The method of filling foundry sand according to claim 1, wherein the vibration imparting an acceleration lower than the gravitational acceleration to the mold and its contents is a vibration in a substantially vertical direction. 5. Said substantially vertical vibration imparting an acceleration to the formwork and its contents higher than the acceleration of gravity,
Frequency: 3600 cycles per minute, amplitude: 0.007in (0.178mm)
and said substantially vertical vibrations imparting an acceleration to the formwork and its contents less than the acceleration of gravity, with a frequency of 3600 cycles per minute and an amplitude of 0.0045 in.
(0.114 mm).