JPS5831260B2 - Casting method for impeller with screw hole - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for casting an Evan propeller having a screw hole for attaching a shaft end.

Normally, to attach the impeller of a centrifugal pump to the shaft, the shaft end is threaded through the boss of the impeller, and the threaded end is tightened with a nut. When using a pump that handles a motor, there is a risk of the impeller coming off due to wear due to corrosion, etc., so as shown in Figure 1, provide a blind screw hole 2 in the impeller 1 and fix it to the shaft end 3 with a screw. The structure is used (
・Ru.

However, since the impeller is made of wear-resistant hard cast steel, it is difficult to machine the screw holes after casting, so a soft steel material is inserted around the screw holes using a cast-in. A method of thread machining was used.

However, with this method, the joining of the cast iron may be insufficient, resulting in low reliability in terms of strength, and the screw processing cost is extremely high (・
(For example, the cost was several times more than the casting cost.)

As a method to improve this, a conventional method has been used in which a screw core is used to form a screw hole by casting.

In this case, as shown in Fig. 2, the casting model 4 (wooden mold) of the impeller is provided with a baseboard 5 in order to provide a hole in the sand mold to support the screw core, and this is used for the upper mold. 6 and lower mold 7 are made.

After removing the casting model 4, a pre-made screw core 9 is placed in the holding hole 8 made by the baseboard 5.

The screw core 9 consists of a threaded portion 1° and a sand mold insertion portion 11,
The sand mold insertion part 11 is inserted into the holding hole 8.

In this case, since the holding hole 8 is provided with a draft angle L to remove the casting model 4, a gap 12 as shown by hatching is created between the holding hole 8 and the sand mold insertion part 11.

Therefore, the screw core 9 is erected while filling this gap 12 with sand, but at this time, it is quite difficult to accurately align the screw core 9 with the axis of the impeller and erect it firmly.

If the impeller is misaligned with the axial center or tilted, problems such as machining difficulty or impossibility will occur because the impeller must be machined with the screw hole in the correct position.

In addition, the screw cores tend to float when pouring, so it was necessary to hold the cores down with wire, which made the process troublesome.

The present invention uses a casting model unit that holds a screw core in a casting model and makes a sand mold, leaves the screw core in the sand mold, and casts it using a mold. Except for the above-mentioned drawbacks of the conventional method, it is extremely easy and reliable to align the screw core to the desired position of the casting.
Moreover, there is no risk of the screw core floating during pouring, and there is no need to use a screw core holder. Casting with screw holes is simple, easy to manufacture, highly reliable, and extremely inexpensive to manufacture. The purpose is to provide a method.

The present invention involves separately producing a casting model of a casting and a ceramic screw core for inserting a screw having a prismatic hole provided along the axial direction in the center, and adding the core to the casting model. is provided with a holding hole into which the threaded part of the screw core is inserted and held;
The screw core is provided with a sand mold insertion part in addition to the thread part,
Insert the threaded part of the threaded core into the holding hole, and with the sand mold insertion part protruding, use the integrated casting model unit to clean the threaded core with sand. The square hole is not substantially filled with sand, and in the following steps, the threaded core is retained in the sand mold, and the casting model is removed, and casting is performed in the mold formed by L. The method for casting a casting with a threaded hole is characterized in that the threaded core is then disintegrated and removed.

The present invention will be explained with reference to the drawings regarding an embodiment of the present invention for an impeller. FIG. 4 shows a casting model 4 (wooden pattern) of an impeller, and as shown in FIG. A holding hole 13 for accommodating and holding the part 10 is provided.

The screw core 9 is provided with a sand mold insertion part 11 in addition to the threaded part 10.

The screw core 9 is, for example, a fired ceramic core, and is provided with a rectangular hole 14 in the center as shown in FIG.

This hole 14 allows the screw core 9 to collapse naturally after the impeller is cast, making it easy to take out.The hole 14 is long in the axial direction at the center, and is prismatic, so it causes stress concentration at the corners and prevents collapse. It becomes easier.

The screw core 9 is held in this casting model 4, and the casting model unit with the sand mold insertion part 11 protruding is used to sand the upper mold 6 and the lower mold as shown in FIG. 7, and as shown in Fig. 8, cast model 4 with screw core 9 left.
remove.

In this case, the screw core 9 is firmly supported by the casting model 4,
It is sanded and fixed while being precisely aligned with the axis of the impeller, and since the sanding can be done firmly, it is firmly held in the sand mold.

Hot water is poured into the mold thus formed to obtain an impeller 1 having blind screw holes 2 as shown in FIG.

In this case, since the ceramic screw core 9 is provided with an angular hole 10, stress is applied when the poured metal solidifies, causing the ceramic screw core 9 to self-destruct.

Therefore, caustic treatment to remove the screw core 9 is not necessary, and of course, machining of the threaded portion is also not necessary.

However, the blind screw hole 2 of the lever can be very easily and reliably aligned with the axis of the impeller 1.

Moreover, since the screw core 9 is firmly held even during pouring, there is no risk of it floating up, and there is no need to hold the core down with a wire or the like, making the work easier.

According to the present invention, castings having screw holes precisely aligned with desired positions can be produced in a simple and easy manner with high reliability and extremely low manufacturing costs.In addition, there is no need for core holding work, which saves time and effort. It is possible to provide a casting method for castings with threaded holes, and has extremely practical effects.

[Brief explanation of drawings]

Figure 1 is a sectional view of the vicinity of the pump impeller, Figure 2 is a sectional view showing the conventional method, Figure 3 is a sectional view of the screw core installed in the conventional method, and Figure 4 Fig. 9 relates to an embodiment of the present invention to an impeller, Fig. 4 is a sectional view of a casting model, Fig. 5 is a front view of the screw core, Fig. 6 is a plan view thereof, and Fig. 7 is a cross-sectional view of a cast model. 8 is a sectional view showing the state immediately before pouring, and FIG. 9 is a sectional view of the completed impeller. 1... Impeller, 2... Blind screw hole, 3... Shaft end, 4... Casting model, 5... Baseboard, 6... Upper mold,
7... Lower mold, 8... Holding hole, 9... Screw core, 1
0...Thread part, 11...Sand mold insertion part, 12...Gap, 13...Holding hole, 14...Hole.

Claims (1)

[Claims] 1. A casting model of the casting and a ceramic screw core with an L-shaped screw Otsuki in which a square hole is provided in the center along the axial direction in a prismatic shape are manufactured separately, and the casting model has the above-mentioned A holding hole is provided for inserting and holding a threaded part of a screw core, the threaded core is provided with a sand mold insertion part in addition to the threaded part, and the threaded part of the screw core is inserted into the holding hole. The integrated casting model unit with the sand mold insertion part protruding was used to remove sand, and the angular hole of the screw core was not substantially filled with sand, and the next step was performed. After removing the casting model while leaving the screw core held in the sand mold with L, casting is performed in the casting mold formed by L.
A method for casting a casting with a threaded hole, characterized in that the threaded core is disintegrated and removed.