Field of the Invention

The present invention relates to an air-conveying apparatus for conveying powdery material such as casting sand that is used for molding a green sand mold.

Description of Prior Art

In the prior art, in conveying, simply by an air conveyor, compactible and sticky powdery material, such as casting sand that is used for molding green sand mold, the powdery material clogs the conveying pipe. This is first because the ratio of the powdery material to be conveyed to the pressurized air to convey the material that is mixed with it changes, and second, the material is intermittently conveyed by the pressurizing tank that conveys the material by applying pressure to it, and so on. For these reasons the flow of the powdery material in the pipe is delayed and the material is compacted, so that the pipe clogs.

To prevent or overcome this clogging phenomenon, secondary air-supplying structures have been located at one-meter intervals in the conveying pipe, or vibrators

have been placed in the pipe where the clogging is expected to occur.

Summary of the Invention

If as above many secondary air-supply mechanisms or vibrators are provided relative to the conveying pipe, the apparatus becomes complex and large, which makes the production costs high. Further, since a large pressurizing tank is used for conveying the material by air, energy consumption due to the air supply and exhaust becomes high.

Considering the above, the present invention provides an efficient air-conveying apparatus wherein the ratio of the powdery material to the conveying pressurized air that is mixed with it is kept constant, so that the powdery material does not clog the conveying pipe.

To attain these purposes the present invention provides an air-conveying apparatus for conveying a powdery material. It comprises an upright and elongated mixing tube 2 having its upper end communicating with a conveying pipe 1, and which pipe 1 blows up from its bottom pressurized conveying air through a filter 3, a powdery material supply tube 8, one end of which opens into the upright and elongated mixing tube 2 through its side surface, a rotatable screw-type feeding vane 10

located in the supply tube 8, a hopper 12 for accommodating the powdery material located above the supply tube 8 so as to communicate with it, and a check valve lid 16 mounted on the end of the supply tube 8 that opens into the upright and elongated mixing tube 2.

Brief Description of the Drawing

Fig. 1 is a longitudinal and cross sectional view showing important portions of an embodiment of the present invention .

Description of the Preferred Embodiment

One embodiment of the present invention will now be explained in detail by reference to the drawing. An upright and elongated mixing tube 2 communicates with a conveying pipe 1. An air-permeable filter 3 is mounted on the lower end of the upright and elongated mixing tube 2 so as to close the lower end, and the filter 3 is surrounded by a lid 4 to form an air chamber 5.

The air chamber 5 has an air-supplying aperture 6 that communicates with a pressurized air-supply source (not shown) . In the air chamber 5 an air-diffusion plate 7 is provided at the upper portion of the air-supply aperture 6.

A powdery material supply tube 8 is connected to the side of the mixing tube 2 so that one end of the supply tube opens, or more preferably, extends into it. A screw-type feeding vane 10 is located in the material supply tube 8. The vane 10 is rotatably supported by a bearing 9 and the end of the vane is connected to an electric motor 11.

Further, a hopper 12 for containing the powdery material is provided above the material supply tube 8 so as to communicate with the supply tube. At the upper and lower portions of the hopper 12 are provided upper- and lower-limit powdery material sensors 13 and 14, respectively. Also, a conveyor belt 15 is positioned above the hopper 12 so that an end of the conveyor belt extends over the hopper 12. The movement of the conveyor belt 15 is controlled, by the two sensors 13 and 14.

At the end of the material supply tube 8, namely, the end that opens into the mixing tube 2, a check valve lid 16 is freely and rotatably mounted. The lid 16 is opened as the powdery material is pushed outward from within the material supply tube 8, and when no pressure is applied from the material supply tube 8 the valve moves toward the end of the supply tube 8 to always close the end.

In this construction as in Fig. 1, when a supply valve (not shown) is opened, pressurized air is introduced into the air chamber 5 through the supply aperture 6 and is

diffused by the air diffusion plate 7. The air passes through the filter 3 and is supplied into the upright and elongated mixing tube 2 and rises so as to be supplied into the conveying pipe 1.

A short time after the air is introduced into the mixing tube 2, the electric motor 11 is driven to rotate the screw-type feeding vane 10, so that the casting sand S in the supply tube 8 is continuously pushed toward the end of the supply tube 8. When the casting sand S is so moved, the check valve lid 16 is forced to open, so that a predetermined amount of the casting sand S is continuously supplied into the elongated supply tube 2 and is mixed at a predetermined ratio with the rising pressurized air. The mixed material is conveyed by air to a predetermined location through the conveying pipe 1.

When the casting sand S in the hopper 12 decreases to below the lower limit of the powdery material sensor 14, the conveyor belt 15 is driven so that the casting sand S is supplemented, and when the casting sand S is filled up to the upper limit of the powdery material sensor 13, the conveyor belt 15 stops.

When the apparatus operates as above, the ratio of the casting sand S to the pressurized air that are mixed together are kept constant, and the casting sand S is continuously conveyed, so that the sand is conveyed

without clogging the conveying pipe 1. In the embodiment explained above, casting sand is used as compactible powdery material. But it is not limited only to it. By this apparatus almost all, especially wet, industrial powdery materials can be similarly conveyed by air.

From the above explanations, clearly the present invention provides an upright and elongated mixing tube to upwardly supply pressurized air. A powdery material supply tube having a screw-type feeding vane in it is opened into the mixing tube so as to continuously supply a predetermined amount of a powdery material into the mixing tube. The ratio of the powdery material to the pressurized air that is mixed with it is kept uniform, and the powdery material can be continuously conveyed. Thus the conveying pipe can be prevented from being clogged without using a large pressure tank and secondary air supply mechanism. Thus the apparatus of the present invention greatly reduces production costs and energy consumption .