JP2934000B2 - Manufacturing method of manhole frame by loss casting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a manhole frame by a vanishing casting method, and particularly to manufacturing a manhole frame in a manhole lid device by a vanishing casting method using a foamed resin model. It is about a practical method.

(Background art) Conventionally, maintenance and maintenance of underground
For example, a manhole cover device as shown in FIG. 1 is provided in an opening of a manhole as an entrance used for management. This manhole cover device is composed of a manhole cover 4 for opening and closing the opening of the manhole 2 and a manhole frame (receiving frame) 6 having a cylindrical tubular wall into which the manhole cover 4 is fitted. The manhole frame 6 has a lower outer flange 8 extending radially outward from the lower portion thereof at a predetermined length as shown in the figure, and the lower outer flange 8 is placed on a foundation concrete 10 forming an opening of the manhole and supported. It is set up by letting go. In FIG. 1, reference numeral 12 denotes a soil layer, on which a concrete layer 14 and an asphalt layer 16 are provided, thereby forming an upper surface of an upper outer flange portion 18 provided on an upper portion of a cylindrical wall portion of the manhole frame 6. And the same road surface is formed.

By the way, with the increasing sewerage penetration rate in recent years, and the importance of urban beauty,
As the number of manholes has increased along with the increase in underground burials such as power lines, the number of manhole cover devices installed in the openings has inevitably increased. In order to meet not only the functional requirements of opening and closing the opening, but also the demand for designs that match the aesthetics of the city, the need for designs that match the aesthetics of the city, the prevention of flying and detachment of the lid, and the locking of locks, etc. Various functions are provided, and various mechanisms are provided inside and outside the cover or frame of the manhole cover device in order to satisfy the many functions, and the form is complicated. It is going on all the time.

Thus, most of manhole cover devices are used as castings by a casting method that easily appears in such a shape because the complicated shape is formed. For the production of a), due to its unique cyclic structure, a)
A large molding machine is required because the central part is a space and there is a necessary part only on the outer periphery. B) In order to make a frame having a cross section as shown in FIG. 1, a three-frame molding is required. There are many problems, such as difficulty in mass production.

On the other hand, the vanishing casting method, which is known as one of the casting methods for obtaining a cast product having a predetermined shape, is capable of realizing the same shape as the model because it is replaced with a cast product using a foamed resin model such as a styrofoam model. Also, unlike sand casting, it has the feature that casting burrs due to the combined surface of the mold do not appear, which has the advantage of reducing casting finishing and machining, and is suitable for high-mix low-volume production, etc. If these features are utilized to the fullest and applied to the casting of manhole frames (frames) of complex shapes, the number of finishing steps is reduced; molding is easier, and productivity is higher. It is possible to enjoy advantages such as cost reduction because a core or the like is not used.

However, when a manhole is cast in accordance with such a vanishing casting method, the resulting cast product (manhole frame) is distorted, and deformation is caused in a lower outer flange portion extending radially outward from a lower portion of the cylindrical wall portion, in particular, It is recognized that the deformation amount reaches 3 to 5 mm, and it cannot be put to practical use as a product.Therefore, while the above features are recognized, the production of manhole frames by the loss casting method is still in practical use. Is not reached.

In view of such circumstances, the present inventors have conducted various studies on the manufacture of manhole frames by the vanishing casting method. The fact that has brought about.

That is, in the vanishing casting method, at the molding stage of the mold, the molding sand is filled around the coated foamed resin model, and further, in order to improve the filling density, vibration by a vibrator is applied. However, such filling with sand tends to be insufficient at a portion below the foamed resin model buried in the mold. For example, FIG. 2 (a)
As shown in the figure, the foamed resin model 20 molded corresponding to the shape of the target manhole frame has a coating layer on its surface.
In a state in which the molding 22 is formed, the molding sand 24 is filled around the molding 22, but the lower portion (cross-hatched portion) below the lower outer flange portion 20 a and the upper outer flange portion 20 b of the model 20 has sand. Can not be supplied sufficiently, and therefore the filling of sand tends to be insufficient,
In particular, since the lower outer flange portion 20a is filled with such insufficient sand and sand pressure is applied from above, it is difficult to maintain the shape only with the strength of the mold wash layer (22). When the casting is performed under such a deformed state, as shown by a broken line in FIG. 2 (b), the lower part of the obtained manhole frame (casting) 6 is formed. The outer flange portion 8 is greatly deformed.

(Solution problem) The present invention has been completed by elucidating such a fact, and an object thereof is to provide a practical manufacturing method of a manhole frame by a lost casting method. Another object of the present invention is to cast a manhole frame excellent in product quality by preventing deformation of an outer flange portion provided at a lower portion of the manhole frame so as to improve its dimensional accuracy.

(Solution) In order to solve such a problem, in the present invention, a cylindrical tubular wall portion into which a manhole cover for opening and closing an opening of a manhole is fitted; When manufacturing a manhole frame provided at an opening of a manhole and having a lower outer flange portion extending radially outward from a lower portion of the portion by a vanishing casting method, (a) corresponding to the shape of the manhole frame Having a cylindrical tubular wall portion and a lower outer flange portion and disappearing during casting to give the manhole frame, a step of preparing a painted foamed resin model,
(B) preparing a heat-resistant support ring having sufficient rigidity to support a lower outer flange portion of the foamed resin model; and (c) storing the foamed resin model in a predetermined casting flask. The support ring is arranged below the lower outer flange portion of the foamed resin model, and under a state in which deformation of the lower outer flange portion is prevented, filling with molding sand is performed to remove the foamed resin model. (D) pouring a predetermined molten metal into the casting mold obtained by the molding, and dissipating the foamed resin model by the heat; And filling the molten metal and casting a target manhole frame.

(Operation) As described above, in the present invention, a heat-resistant support ring having sufficient rigidity to support the lower outer flange of the foamed resin model that provides the manhole frame is used, and this support ring is used for the foamed resin model. Since it is arranged below the lower outer flange to fill the molding sand, the support ring serves as a back sand, and the lower part of the lower outer flange of the foamed resin model. Can be effectively reduced or eliminated, and since the lower outer flange portion is supported from below by the support ring, even if the sand pressure of the molding sand from above is applied, Even if the strength of the coating layer on the surface of the foamed resin model is reduced due to heat during casting, the lower outer flange portion can be effectively prevented from being distorted and deformed. As a result, a manhole cover having excellent dimensional accuracy can be advantageously cast.

(Specific Configurations / Examples) By the way, as for the manhole frame cast according to the method of the present invention, any known various types including the manhole frame (6) illustrated in FIG. They comprise at least a cylindrical tubular wall portion into which a manhole cover for opening and closing the opening of the manhole is fitted, and a lower outer flange portion extending radially outward from a lower portion of the cylindrical wall portion. ing. As shown in FIG. 1, this manhole frame is installed on a foundation concrete 10 forming an opening of the manhole, and is fixedly supported. Although always provided, the upper outer flange portion 18 is not indispensable, and some of them do not include such an upper outer flange portion 18 depending on the type of manhole frame.

And in order to manufacture such a manhole frame,
First, corresponding to the shape of such a manhole frame, it has a cylindrical tubular wall portion and a lower outer flange portion, which disappears during casting,
A foamed resin model for providing the manhole frame is prepared. That is, as shown in FIG. 3 (a), a foamed resin model 30 having a substantially similar shape to the shape of the target manhole frame is molded by the same foam molding technique as that of the related art. Therefore, such a model 30 has a cylindrical wall portion 32 corresponding to the cylindrical wall portion of the manhole frame and a cylindrical wall portion 32 corresponding to the outer flange portion at the lower portion of the manhole frame, as is apparent from the drawing. A lower outer flange portion 34 extending radially outward from a lower portion of the cylinder, and an upper outer flange portion 36 extending radially outward at an upper portion of the cylindrical wall portion 32 corresponding to the outer flange portion of the upper portion of the manhole frame. ing. In addition, such a foamed resin model 30 is subjected to a drying operation as necessary after the foam molding, thereby stabilizing product dimensions. Further, as the resin material for providing the model 30, various known materials can be appropriately selected and used, but generally, a styrene resin (polystyrene resin) is preferably used.

Also, a foamed resin model obtained by foam molding in this way
30 is subjected to a coating process using a coating material similar to the conventional one, and as shown in FIGS. 3 (b) and (c), the model
On the surface of 30, a coating layer 38 having a predetermined thickness is formed. This mold wash layer 38 adjusts the surface shape of a casting product obtained by casting, and realizes a smooth casting surface, and the strength of the model 30 is also increased to a certain extent by such a mold wash layer 38. Will be enhanced. The coating material for forming the coating layer 38 is in the form of a slurry containing silica sand and a binder similar to the conventional one, and is subjected to one or more coating operations according to a conventional method such as dipping. Is carried out, and usually, a coating layer 38 having a predetermined thickness is formed on the entire surface of the model 30.

Meanwhile, in order to use the vanishing casting method according to the present invention, an annular support ring 40 as shown in FIG. 4 corresponding to the lower outer flange portion 34 of the foamed resin model 30 is prepared. The support ring 40 has sufficient rigidity to support the outer flange portion 34 at the lower part of the foamed resin model 30, and does not deform due to the heat of the molten metal poured at the time of casting. It is provided with. As will be described later, such a service ring 40 is disposed below the outer flange portion 34 below the foamed resin model 30, and the outer flange portion 34 is deformed so as to prevent deformation of the outer flange portion 34. Because of the support, it is generally formed with a width equal to or greater than the width of the outer flange portion 34 and a thickness that provides sufficient rigidity (strength). In the foam resin model that gives a frame, at a thickness of about 10 to 15 mm,
Since the object can be sufficiently achieved, the support ring 40 is formed at least in such a thickness or more.

The support ring 40 can be formed using various known materials as long as the above requirements are satisfied. Generally, the support ring 40 is formed using self-hardening molding sand or shell sand used for shell molding. And can also be formed using a refractory such as ceramics. In order to further increase the rigidity of the support ring 40, embedding a core material therein is also an effective means.

In the present invention, a target manhole frame is manufactured by a vanishing casting method using the foamed resin model (30) and the support ring (40) prepared as described above.

That is, as illustrated in FIG. 5, first, a predetermined casting flask 42 is filled with floor sand 44 using molding sand (a).

Next, as shown in FIG. 5 (b), the foamed resin model 30 is placed on the floor sand 44 filled in the casting flask 42 via the support ring 40 in a form such as flat placement. . At this time, the lower surface of the lower outer flange portion 34 of the foamed resin model 30 and the upper surface of the support ring 40 are made as close as possible, and the lower outer flange portion 34 and the support ring 40 are It is placed so that its position is fixed. The lower outer flange portion of the foam resin model 30
As shown in FIG. 6, it is desirable that the close fixation between the support ring 40 and the support ring 40 be performed using a suitable fixing means such as a taping 60, so that even if a vibration operation is applied, An effective fixed positional relationship between them is maintained. Further, a gate 46 made of the same foamed resin material as the foamed resin model 30 is arranged inside the cylindrical wall portion of the foamed resin model 30 in order to form a runner at the time of pouring. The gate 46 is formed in a cross shape at the lower part,
The tip of the cross-shaped portion is brought into contact with the inner surface corresponding to the portion where the lower outer flange portion 34 of the foamed resin model 30 is provided, thereby pouring the foamed resin model 30 as described later. Can be performed well.

Then, in this manner, the foamed resin model 30 is placed on the floor sand 44 via the support ring 40, and the deformation of the lower outer flange portion 34 of the foamed resin model 30 is prevented. In the casting mold 42, a molding sand 48 is further supplied, and in the same manner as in the prior art, a shaking machine is used to vibrate the sand so that the sand is in a fluid state to increase the packing density and stabilize the model 30. Then, the molding sand 48 is filled, and as shown in FIG. 5 (c), a casting mold 54 in which the foamed resin model 30 is buried is formed.

In this way, by molding the intended casting mold 54, for the lower part of the buried foam resin model 30,
In particular, even when the weight (sand pressure) of the upper sand is applied to the lower outer flange portion 34, the support ring 40 exists below the lower outer flange portion 34, and serves as a back sand. In addition, since the lower outer flange portion 34 is supported, even if a defective filling occurs below the support ring 40, the deformation of the lower outer flange portion 34 can be satisfactorily avoided.

As shown in FIG. 5 (d), the casting mold 54 thus obtained is provided with a metal 46 such as a molten cast iron from a ladle 52 or the like, through a gate 46 exposed on the upper surface of the casting mold 54.
By being poured into the gate formed in the part,
The heat of the molten metal 50 causes the gate 46 and further the foamed resin model 30 to disappear, the cavity formed therein is filled with the molten metal 50, and the desired manhole frame is cast. At the time of pouring the molten metal 50, the casting mold 54 is connected to a pressure reducing source as in the related art, and is operated under a reduced pressure for suction and removal of gas generated during pouring in the mold. Will be held.

Thereafter, from the mold 54 in which the manhole frame has been cast in this way, the cast product (manhole frame) is taken out from the mold 54 in the same manner as in the related art, and the cast product is applied thereto. In the manhole frame obtained according to the above, the deformation of the lower outer flange portion is advantageously suppressed or prevented, and the dimensional accuracy is enhanced, so that the finishing can be easily completed. .

(Effects of the Invention) As is clear from the above description, according to the present invention, the deformation of the obtained manhole frame, that is, the deformation of the outer flange portion located below the manhole frame can be suppressed or prevented satisfactorily. Since the dimensional accuracy can be improved, a practical manufacturing method of the manhole frame by the lost casting method has been established here, and while making the most of the features of the lost casting method, it is complicated. The manhole frame in the form can be advantageously manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory longitudinal sectional view showing a construction state of a manhole cover device, and FIG. 2 (a) is for explaining a filling state of sand in a mold formed by burying a foamed resin model providing a manhole frame. FIG. 2 (b) is an enlarged partial view of a main part of FIG.
FIG. 2 is an enlarged sectional partial view showing a modified form of an outer flange portion at a lower portion of a manhole frame cast by a conventional vanishing casting method. FIG. 3 shows an example of a foamed resin model prepared in the present invention. FIG. 3 (a) is an explanatory longitudinal sectional view of a foamed model, and FIG. The figure which shows the state by which a type | mold is given, (c) is
It is an enlarged explanatory view of A part in (b). FIG.
It is a perspective view showing an example of a support ring prepared in the present invention. FIG. 5 is a process diagram showing an example of a molding process and a casting process of a mold according to the present invention, wherein FIG. 5 (a) is a cross-sectional explanatory view showing a state where floor sand is filled, and FIG. Cross-sectional explanatory view showing the arrangement state of the ring,
(C) is a sectional explanatory view showing a casting mold in which a foamed resin model is buried, and (d) is a sectional explanatory view showing a state in which a molten metal is poured into the casting mold. FIG. 6 is a partially enlarged cross-sectional explanatory view showing a desirable fixing form of the support ring to the lower outer flange portion of the foamed resin model. 2: Manhole, 4: Manhole cover 6: Manhole frame, 8: Lower outer flange 30: Foam resin model, 32: Tube wall 34: Lower outer flange, 38: Coating layer 40: Support ring, 42: Casting Frame 44: Floor sand, 46: Gate 48: Foundry sand, 50: Molten metal 54: Casting mold, 60: Taping

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-11228 (JP, A) JP-A-2-165584 (JP, A) JP-A-62-54547 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) B22C 9/04 B22D 25/02 E02D 29/14

Claims (1)

(57) [Claims] 1. A cylinder-shaped cylindrical wall into which a manhole cover for opening and closing an opening of a manhole is fitted, and a lower outer flange extending radially outward from a lower portion of the cylindrical wall. Further, a method for manufacturing a manhole frame installed in an opening of a manhole by a vanishing casting method, comprising a cylindrical tube wall portion and a lower outer flange portion corresponding to the shape of the manhole frame, A step of preparing a coated foamed resin film mold that gives up the manhole frame, and provides a heat-resistant support ring having sufficient rigidity to support the lower outer flange portion of the foamed resin model Receiving the foamed resin model in a predetermined casting frame, disposing the support ring below the lower outer flange portion of the foamed resin model, and preventing deformation of the lower outer flange portion. Under the condition A step of filling a molding sand and molding a casting mold in which the foamed resin model is buried, pouring a predetermined molten metal into the casting mold obtained by the molding, Removing the foamed resin model, filling the resulting cavity with the molten metal, and casting a target manhole frame.