US3916981A

US3916981A - Apparatus for producing sleeves or sheets for feeder heads formed in metal casting

Info

Publication number: US3916981A
Application number: US390407A
Authority: US
Inventors: Masamitsu Miki
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-07
Filing date: 1973-08-22
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04

Abstract

An apparatus for producing feeder head sheets for use in metal molding, which comprises a cotton-opening mixer having rotating blades for cotton-opening and mixing in the dry state granular, refractory materials and fibrous materials; a kneader for kneading, in the wet state, the materials cotton-opened and mixed by said cotton-opening mixer; and molding machines for molding, in a mold under air pressure, the materials kneaded by the kneader.

Description

' United States Patent Miki Nov. 4, 1975 APPARATUS FOR PRODUCING SLEEVES 2,671,496 3/1954 Chavannes et a1 264/122 x ()R SHEETS FOR DE HEADS FORMED 3,345,442 10/1967 Oxel 3,439,734 4/1969 Eastwood 164/33 X IN METAL CASTING Masamitsu Miki, No. 25-15, l-chrome, Nakahara, Mitaka, Tokyo, Japan Filed: Aug. 22, 1973 Appl. No.: 390,407

Related US. Application Data Continuation-impart of Ser. No. 129,778, March 13, 1971, Pat. No. 3,776,992.

Inventor:

Foreign Application Priority Data Sept. 7, 1970 Japan 45-77948 Sept. 7, 1970 Japan 45-77949 US. Cl 164/159; 425/205 Int. Cl. B22C 15/22 Field of Search 164/6, 33, 159; 264/260,

Primary ExaminerE-Frtmcis S. Husar Assistant ExaminerJohn E. Roethel Attorney, Agent, or FirmObl0n, Fisher, Spivak, McClelland & Maier [57] ABSTRACT An apparatus for producing feeder head sheets for use in metal molding-which comprises a cotton-opening mixer having rotating blades for cotton-opening and mixing in the dry state granular, refractory materials and fibrous materials; a kneader for kneading, in the wet state, the materials cotton-opened and mixed by said cotton-opening mixer; and molding machines for molding, in a mold under air pressure, the materials kneaded by the kneader.

8 Claims, 13 Drawing Figures U.S. Patent Nov. 4, 1975 Sheet 1 of5 3,916,981

2.552: Q2 8 8 R E 8 8 8 8 e 0 U8. Patent Nov. 4, 1975 Sheet 2 of5 3,916,981

cop oom oom oow -oom oow ooh MIJLLLITITTQJ Y Q 88 I lblll lIl- IIIIO [1 Patent Nov. 4, 1975 Sheet 3 of5 3,916,981

FIG. [0

FIG. 6

FIG. 7

US. Patent Nov. 4, 1975 Sheet4 of5 3,916,981

FIG.

US. Patent NOV.4, 1975 SheetSofS 3,916,981

APPARATUS FOR PRODUCING SLEEVES OR SHEETS FOR FEEDER HEADS FORMED IN METAL CASTING This application is a continuation-in-part of application Ser. No. 129,778 filed Mar. 13, l97l, now US. Pat. No. 3,776,992.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an appara tus of producing sleeves or sheets for feeder heads formed in metal casting. More particularly, this invention relates to an apparatus of continuously producing exothermic or heat-insulating sleeves or sheets for feeder heads formed in metal casting in which large quantities of fibrous materials are added.

2. Description of the Prior Art Various exothermic or heat-insulating materials have been previously used for making feeder head sleeves formed in metal castings, particularly castings of steel, iron or the like. They have also been formed into sheets or slabs for framing feeder heads formed in molds used for steel ingot making. Large volumes of data and knowledge are available regarding the shape, structure and production method of such sleeves, sheets or slabs. However, recently upgraded requirements for such a sleeve or sheet demand a higher heat-insulating effect, lighter weight, higher strength, and particularly higher flexibility in order to obtain more effective and economical feeder heads. Efforts for this purpose have been directed to the development of new materials for making such sleeves or sheets by the addition of inexpensive organic or inorganic fibrous materials, rather than addition of expensive exothermic materials, as components to the refractory materials, thereby attaining refractory materials of lighter weight, higher strength, and increased porosity.

However, even when such sleeves or sheets are made by adding said large quantities of fibrous materials to the refractory materials that their apparent specific gravities are below 1 (therefore lighter than water), great difficulties still arise in molding such sleeves or sheets. This is because heretofore, a large volume of water had to be used to make a uniform, a pasty or muddy mixture of powdered or granular refractory materials with the large quantities of fibrous materials, with or without the addition of an exothermic agent, an oxidizer, or the like. This large quantity of water thereafter had to be removed during the sleeve molding step, which makes that step very complicated and difficult. In conventional molding methods removal of this large quantity of water was accomplished by use of a vacuum system. According to this method, molding is carried out by using net type molds, while the water is sucked out by the vacuum system. Sleeves or sheets made in this manner, however, are inferior in strength to the sleeves or sheets made by pressing. Moreover, any method using a vacuum water-removal system is unsuitable for the mass production of sleeves or sheets. Therefore, a special mold had to be developed for pressing in the sleeve molding step of the conventional methods. This enabledthe production of sleeves of higher strength, but efficient mass production of such sleeves was still unattainable.

By conventional methods using either a vacuum system or special molds for pressing, molding is difficult because a large volume of water must be removed; par- 2 ticularly difficult is molding with metal molds which are shaped like sleeves, because muddy materials are apt to slip off the molds and because product molds themselves tend to break.

Therefore, the addition of large quantities of fibrous materials is difficult, in conventional molding methods. and thus it is very difficult, using such methods, to produce feeder head sleeves or sheets which have an apparent specific gravity of below I and still retain high strength. Even if this were theoretically possible, there is no practical way of applying the so-molded sleeves to commercial metal castings that use a core shooter. molding machine, or the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for economical, continuous production of exothermic or heat-insulating feeder head sleeves or sheets formed in metal casting which have an apparent specific gravity of below 1 together with high strength, good heat insulation and moisture repellence.

Another object of the present invention is to provide an apparatus for the continuous production of feeder head sleeves formed in metal casting of sheets or slabs, such as for framing feeder heads formed in molds for steel ingot-making, from a mixture of refractory materials of powder or granular form with large quantities of inorganic and organic fibrous materials in which the molding of such sleeves, sheets or slabs is carried out through pressing by using a core shooter for metal casting, a core-producing machine, or the like.

In order to achieve the abovementioned objects, the present invention is constructed, as follows:

The present invention is so characterized that an apparatus for producing feeder head sheets for use in metal molding comprises a cotton-opening mixer having rotating blades for cotton-opening and mixing in the dry state granular, refractory materials and fibrous materials; a kneader for kneading, in the wet state, the materials cotton-opened and mixed by said cottonopening mixer; and molding machines for molding, in a mold under air pressure, the materials kneaded by the kneader.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features and attendant advantages of this invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying Drawings, wherein:

FIG. 1 shows an operation flow-sheet describing the method and apparatus of the present invention;

FIG. 2A shows a diagrammatic sectional view of the molding step in the method of the present invention;

FIG. 2B shows an enlarged view of area IIB in FIG. 2A;

FIG. 3 shows a perspective view of a sleeve and sheet made by the method of the present invention;

FIG. 4 is a curve comparing the heat insulation property of sleeves produced by the method of the present invention with sleeves produced by the conventional methods;

FIG. 5 shows comparative sectional views of feeder heads formed by using sleeves produced by the method of the present invention and feeder heads formed by conventional methods.

FIG. 6 is a front view of the molding machine of the present invention.

FIG. 7 shows the principal section ofthe molding machine of FIG. 6, part of which is exploded for further illustration.

FIG. 8 is a perspective view of a sleeve, which is an element of the over-all mold of the present invention.

FIG. 9 and FIG. are cross-sectional views, respectively, of the inner metal mold and the outer metal mold according to the present invention.

FIG. 11 is a side view of the apparatus consisting of a cotton-opening mixer and a kneader incorporated into one entity according to the present invention, partially cut away for illustration of its cross-section.

FIG. 12 is a side view of kneading blades of the kneader shown in FIG. 11.

DESCRIPTION OF PREFERRED EMBODIMENTS The following is a description of the present invention using a preferred embodiment illustrated in the Drawings:

The method of the present invention is explained, as follows, using an operation flow-sheet of a continuous production apparatus shown in FIG. 1. It is noted that practice of the method of the present invention is not limited to the use of such a continuous production apparatus.

The whole process of the method of the present invention is divided into four or five steps: the first step for blending raw materials (if not required, this step may be omitted); the second step for cotton-opening; the third step for kneading; the fourth step for molding; and the fifth step for drying.

In order to obtain heat-insulating sleeves having an apparent specific gravity below 1 according to the method consisting of the abovementioned steps, blending of the raw materials in the first step is as follows:

10 5O '7( by weight 60 7r by weight 5 "/2 by weight 5 30 by weight Note: In the above case, the total of inorganic fibrous materials (b) and organic fibrous materials (c) should be greater than 30 percent. For producing exothermic and heat-insulating sleeves, the refractory materials should contain an exothermic material and its oxidizing agent.

Whether having been pre-mixed or not, the abovementioned materials in the abovementioned ratios are charged to a hopper 2 using a charging bucket l. The materials all then continuously sliced out of the hopper by a slicer 3 into a lot of the desired amount, and delivered into a cotton-opening mixer 4 at the second step. The first step may be omitted so that the raw materials are charged directly into cotton-opening mixer 4, as shown by the dotted lines.

Cotton-opening mixer 4 is equipped, on its inside, with a screw 5 having blades to cut or cotton-open fibrous materials, and with an agitating bar 6. The cotton-opening mixer, rotated by a motor 7 set above it, minces and efficiently cotton-opens the charged mixture of raw materials, particularly fibrous materials (b) and (c), in the dry state, and mixes the so-cottonopened materials with other materials of powder or granular form, such as refractory materials. Herein, cotton opening" means unravelling and loosening interwined fibers of organic or inorganic nature and cutting them into short pieces, if they are long. In general,

such inorganic fibers as of asbestos and such organic ones as of pulp are in the interwined state, where the mixing of such fibers with refractory materials of granular state would not produce a mixture of good uniformity and would contain lumps and the like. In order to avoid such complications, there is used a cotton-opening mixer 4 consisting of rotating blades 5 rotating at high rate and an agitating bar 6, according to the present invention. Thus, the interwined fibriform materials are struck, unravelled and loosened by the rotating blades rotating at high speed, and long-sized fibers of them are cut into slender or short pieces. On the other hand, the rotation at high rate of the rotating blades, produces a wind, causing the unravelled fibers and particles of the refractory materials to float in the air and make the mixing uniform. Cotton-opening at the second step is novel and has not been adopted by any known methods other than the method of the present invention. Then a mixture containing the so-cottonopened materials is sent from the bottom of the cottonopening mixer 4 into an aqueduct shaped hopper 9 set at one end of a kneader 8.

Less than 150 percent, preferably between and percent water is supplied to this mixture by a pump 10, and while it is being kneaded, it is sent by a screwconveyor 11 driven by a motor 12 disposed at to the left end of kneader 8 so as to fall from its right end into an alternating hopper 13.

As the mixture has been cotton-opened and well mixed in the second step, it can be kneaded in the kneader 8 by using a small amount of water, such as about percent, so that even though it is kneaded with water, such kneading does not need a great quantity of water, and the kneaded mixture is kept in the original powder or granular form, which is quite different from that obtained according to conventional methods.

The process of making such a mixture hold in the powder, granular, or solid form with water without being a slurry or pasty and muddy, is impossible or quite new to the conventional methods, and constitutes an important characteristic element of the present invention. Moreover, this process makes possible continuous molding of sleeves by pressing at the fourth step.

The mixture of powder or granular form which has been put into said alternating hopper 13 is sent to the fourth step, where it is charged by an alternating dumper l4 alternately into a hopper 17 and a hopper 18 set respectively on

molding machines

19 and 20. Molding by the

molding machines

19 and 20 at the fourth step is carried out as shown in FIG. 2A. As the two molding series follow the same operation process, only one series is described in the following explanation. The mixture of powder or granular form 25 in one of the hoppers 18 is charged into

molds

22 and 23 as the volume of one lot which has been sliced out from dumper 26. As the molds are filled with the mixture 25, the dumper 26 is shut, and the so charged mixture is pressed from top to bottom under a pressure of 5 or 6 Kg/cm by compressed air 27.

inserted in the outer metal mold 34 a ring-shaped space is formed between the inner metal mold 35 and the outer metal mold 34 constituting an over-all mold 33.

The inside of the injection head 31 constitutes a cylindrical, blank space 36, which contains a sleeve 37 which many slits 38 each being produced vertically thereon with a width of 0.4 to 0.6mm.

At the top of the injection head 31 there is provided a hopper 39 receiving kneaded material. There is a shutter 41 operating on an air cylinder 40 for connection and disconnection between the hopper 39 and said blank space 36. On the bottom surface of the injection head 31 there is provided an annular, charging inlet 42, through which the blank space 36 and the space between the two

metal molds

34 and 35 are connected.

On the right of the injection head 31 there is provided a compressed air chamber 43, which is connected with the blank space 36 through an air blasting valve 44. On the left of the injection head 31, there is provided an exhaust valve 45 having a piston actuator 46.

In the machine having the abovementioned structure, the shutter 41 operates periodically and automatically, so as to supply a certain amount of kneaded materials from the hopper 39 into the sleeve 37 which is provided in the injection head 31. When materials have been charged in the sleeve 37 to the full, the shutter 41 closes, and the air blasting valve 44 opens, so that compressed air goes from the compressed air chamber 43 into the sleeve 37 through the air blasting valve 44 and the slits 38 of the sleeve 37. The materials in the sleeve 37 are pushed by air pressure and injected into the over-all mold 33 which is constructed with the two

metal molds

34 and 35.

When the injection of materials into the over-all mold 33 finishes, the air blasting valve 44 closes, and the exhaust valve 45 opens, so as to exhaust the com pressed air remaining unused in the blank space 36.

The feeder head sleeve having been thus produced, the table 32 is allowed to descend, carrying thereon the inner metal mold 35 as this is vibrated by a vibrater (not shown), thereby taking the inner metal mold 35 off the so molded feeder head sleeve. Then, the holding arm 48 rotates about the axle 49 of the removal apparatus 47 as the center of such turning; and the outer metal mold 34 containing the so molded feeder head sleeve, is moved to the ejection apparatus 47, which pushes the feeder head sleeve out of the outer metal mold 34 by means of a pusher 50 equipped with an air cylinder.

All the abovementioned process are carried out automatically.

In the course of such molding, compressed air presses the mixture 25, and is then let out from the mixture 25 through a great number of air-water vent holes 24, 24 provided on

molds

22 and 23. Molding can be done simply and rapidly in the same manner as used in the case of producing cores for metal casting. If there is more water than necessary in the to-be-pressed mixture, such excess water will be removed together with air through the vent holes 24, but there is very little water to be removed in the case of molding according to the present invention. If there should be very much water to be removed, the molding process of the present invention can still be done, but with difficulty. Therefore, according to the present invention, a mixture is kneaded at the kneading step so as not to make it slurry, or pasty and muddy, but as holding the powder, granular, or solid form with less than 150 percent water added, as mentioned above; the so-made mixture makes possible continuous molding by pressing with compressed air. As shown in FIG. 2B, an enlarged view of FIG. 2A, each of said vent holes 24 is constructed as a cluster ofa great number of minute holes 24', so as to prevent passage of the mixture of powder or granular form. y

nos. 8, 9 and l0show another embodiment or the apparatus of the present invention, in which the overall mold is constructed with a thin-walled sleeve made of copper and a strong frame. 1

As shown in FIG. 8, a sleeve 52 is 2 or 3 mm thick, and has slender slits 53 each being 40 to mm long and 0.2 to 0.4 mm wide which are arranged bit the sleeve in parallel with the axis, that is, perpendicularly, and in staggered relation each with next one. lfthis sleeve is used alone, it will easily deform or break, making it necessary to reinforce it in any way. i

FIG. 9 shows one example of the inner metal mold 51 having a frame 54 inserted inside the sleeve 52, such frame having square openings 55 thereon. FIG. 10 shows one example of the outer metal mold 56, the sleeve 52 of which has a frame 57 provided outside thereof, such frame having a number of round holds 58 thereon, which however can be replaced by square openings. in case the metal mold is constructed with a sleeve having a number of slender slits, products produced by using such mold maintain fixed shape, and

can be well drained.

The size and. number of slits of the sleeve and the shape of the frame are open for choice according to the shape and size of products.

Such molding is also possible with a light'pressing, either manually or with a machine,'instead of using compressed air.

FIG. 11 show another embodiment of the apparatus of the present invention, where a cotton-opening mixer and a kneader are incorporated into one entity.

The vessel 62 of the cotton-opening mixer 61 comprises a cylindrical part 63 and a circular truncated cone part 64, and is held by a frame 85 so that the axis of the trunk stands perpendicularlly. [t is tightly closed and the cover 65 at the top of the vessel 62 is provided with a conical frame 66 extending downward inside the vessel 62.

At the bottom end of the frame 66 and on the upper surface of said cover 65, there are fixed respectively

bearings

68 and 67. A rotating shaft.69 having an end near the bottom of the vessel 62, is supported by said

bearings

67 and 68 for free rotation, in such manner as to conicide with the central axis of the vessel 62.

There are three sets of

blades

71, 72 and 73 fixed on this rotating shaft 69, each set having four horizontallyextending blades arranged to form a cross. The first set of blades 71 is situated nearly at the center of the rotating shaft 69; the third set of blades 73 is situated at the lower end of the rotating shaft 69; and the second set of blades 72 is nearly in between the first and the third sets of blades. The length of blades is shorter, as they are situated at the lower positions. Particularly, the blades 73 of the third set are twisted so that their rotation causes upward stream of wind. The number of sets of blades is determined according to the capacity of the apparatus to two, three and more.,-

The cover 65 of the vessel 62 is provided with a fixer 74 extending horizontally, to which is connected a motor 75. The rotation of the motor 75 is transmitted by a belt transmission 76 to the rotating shaft 69, so as 7 to rotate the blades at 400 to 600 R.P.M.

Also. the vessel 62 has a section 77 for receiving materials for mixing, which is slanted toward the inside of the vessel 62. The receiving inlet 78 of said section 77 is shut or opened periodically and automatically by a sliding shutter 80 operating with an air cylinder 79. The bottom section of the cotton-opening mixer 61 is connected with a kneader 91 mentioned below, through a shutter 82 operating with an air cylinder 81.

The vessel 92 of the kneader 91 is tightly enclosed, and its lower half constitutes a semi-cylindrical trunk 93.

A rotating shaft 94 runs horizontally through the vessel 92 in such manner that its axis corresponds with the center of the curvature of said semi-cylindrical trunk 93. Both ends of the rotating shaft 94 are supported for free rotation by bearings 95 fixed on the frame 85.

On the rotating shaft 94 within the vessel 92 there are fixed, with fixing blocks 103, six kneading blades 96, each extending at a right angle from the rotation shaft 94. These blades 97 102 are fixed on the rotating shaft 92, each being shifted at lfrom the adjacent one. In FIG. 12, the blades on the

left side

97, 98 and 99 are slightly twisted. so as to shift the charged materials to the right, and the blades on the right side 100,101, and 102 are also twisted, so as to shift the charged materials to the left. The

blades

97 and 102 at both ends are twisted at the greatest angle. the resulting material pushing strength to the opposite side being the greatest. The number of blades needs not be limited to six. as in the above mentioned embodiment of the present invention. but may be changeable according to the capacity of the apparatus.

There is a motor 104 fixed on the frame 85. Its rotation is transmitted by a belt transmission 105 to the rotating shaft 94 of said kneading blades 96. These blades 96 rotate at to 50 R.R.M. for kneading materials.

There is a water supplying pipe 106 connected with the vessel 92 of the kneader 91 at the top; and the pipe is for automatic supply of properly adjusted amount of water to the materials, such adjustment being made on the opening and closing of a magnet valve 107. Also, the semi-cylindrical trunk 93 of the vessel 92 is provided with a door 109 operating on an air cylinder 108; the kneaded materials are sent out of the apparatus when the door 109 is open.

The following is explanation of the cotton-opening mixer 61 and the kneader 91 which have the abovementioned structures:

A predetermined amount of to-be-mixed materials is charged into the vessel 62 of the cotton-opening mixer 61 at its receiving inlet 78. The charged materials are struck by the blades 71 of the first set and the blades 72 of the second set; and the fibrous materials are unravelled, thus long ones are cut into small or short pieces. The so processed materials are mixed by the rotation of the blades 73 of the third set. As these blades 73 produce upward stream of wind, as mentioned above, such small pieces of the materials are made to float up in the vessel 62, making better mixing with the other materials.

When the cotton-opening and mixing of the materials finishes, the shutter 82 is opened, so that the materials drop into the vessel 92 of the kneader 91.

Then, the materials move also horizontally, as they are turned up by the rotation of the kneading blades 96, hence complete mixing can be made in short time.

When the kneading ofthe materials finishes, the door 109 is opened by means of the air cylinder 108, so that the materials drop onto a belt conveyor 110, so as to be sent to said

molding machine

19 or 20. Also, instead of the abovementioned type slicer 3, cotton-opening mixer 4, and kneader 8, any types will meet the purposes of the present invention.

Sleeves which have been molded as mentioned above are dried at about C, in a drier 21 in the fifth step. During this drying process, the mixed blending agent, e.g., phenol resin, melts and covers the powder or granular form materials so as to bind them together and make a solid sleeve. Besides, a cover with the binding agent makes the product sleeve also water-repellant, that is, highly moisture-repellant.

Physical properties of the so-produced heat-insulating sleeve product, as shown in FIG. 31 are: a transverse strength of about 20 kg/cm (nearly the same as that of products of the conventional methods); apparent specific gravity; 0.7O.9 (against 1.1-1.5 of products of conventional methods); and almost no damp absorption as compared with products of conventional methods. (Note: the products of the conventional methods for the above comparison contained no fibrous materials.)

Needless to say, besides the production of products which could be molded with difficulty anyway, the method of the present invention can be more easily applied to the production of sheets which can be molded without difficulty by using a device for producing molds for sheets, such as the sheets of FIG. 311.

The following are special characteristics of the above-mentioned mixtures according to the present invention:

As refractory materials (a) of granular form contained in the abovementioned mixture are use silica stone, alumina, chamot, brick powder, fly-ash, silica, etc. If necessary, such exothermic materials such as aluminum and its oxidizing agent are added thereto. The granular size of any of these materials should be between 0.2 and 1 mm. As inorganic fibrous materials (b) are used rock wool, glass wool, ore flakes, asbestos, etc., any of which is sized about 3 to 5 mm. in the longitudinal direction. As organic fibrous materials (c) are used wood chips, pulp, fiber, paper, etc., any of which is sized about 0.5 to 5 mm. in the longitudinal direction. As a binding agent (d) is used a water-insoluble snythetic resin such as phenol resin.

The purposes of mixing the abovementioned raw materials are: The refractory materials (a) such as silica and brick powder make the product fireproof and keep its form stable when used; inorganic fibrous materials (b) such as asbestos and ore flakes makes the product strong and light; and organic fibrous materials (c) such as wood powder and pulp make the product light and porous. In order to make the apparent specific gravity below 1, it is necessary to make the total of inorganic and organic fibrous materials at least 30 percent by weight of the mixture. A binding agent (d) such as phenol resin is added to melt in the molding step and cover the abovementioned mixture so as to bind the materials of granular form and make the product water-repellent and mositure-proof.

As mentioned above, according to the present invention, large quantities of inorganic and organic fibrous materials are mixed, thereby making the apparent specific gravity of product below (that is, lighter than water), and also making it strong. Because of such light 9 r weight, the product has high heatinsulation, and because of the use of a binding agent, it exhibits good moisture prevention, as mentioned above, thereby not only greatly raising feeder head effects of the product, but also reducingproduction costs.

In summary of the abovementioned heretofore, when large quantities of fibrous material have been mixed with a powderedor granular refractory materials it has been so difficult to mold such a mixture that the art has even suggested kneading the refractory-fiber mixture with water glass or the like, instead of water, such kneading being customary with the conventional methods, otherwise to restrict the quantity of fibrous materials used. In general, according to the prior art, in order to knead a mixture with a large quantity of fibrous materials by conventional methods, a great quantity of water, e.g., 500-700 percent, had to be used to form a fluid mixture to assume proper mixing. However, this makes it necessary to remove such large quantities of water in the molding step, making the molding process complicated and difficult.

According to the present invention, however, a mixture of raw materials is cotton-opened and well mixed in the dry state before being kneaded with water, thus holding itself in nearly the same condition as of a mixture containing only refractory materials according to the conventional methods, that is, in the original powder or granular form of no fluidity, with the addition of less than 150 percent water, preferably between 75 and I percent when kneaded. This makes it possible to carry out molding without any special process to remove superfluous water, and to use a pressing method for such molding, thereby again making it possible to mass-produce sleeves by using a core producing machine or the like in the molding step, and, moreover, to make such sleeves strong and heat-insulating.

As mentioned above, according to the method of the present invention and by using an apparatus therefor, it is possible to easily and continuously produce sleeves or sheets of an apparent specific gravity of below 1. However, the method of the present invention is not limitedly applied to the production of such sleeves or sheets, but is applicable also to the production of sleeves or sheets of an apparent specific gravity of about 1, to even large quantities of fibrous materials added to refractory materials, etc. That is to say, in this case, also the method of the present invention functions in cotton-opening the added fibrous materials to be well mixed in the mixing step with other materials, such as refractory materials, so that the so 'made mixture may be subjected to molding without the need of removing water in the molding step, though it has been kneaded in the previous kneading step with some water added. Thus, it is possible to mass-produce products by a pressing method, as well as making them stronger than those made otherwise.

However, according to the conventional methods, fibrous materials are mixed, in the original form, with refractory materials of granular form and other materials, so it is necessary to add such a great volume of water, e.g. 500-700 percent in order to make the mixture pasty and muddy for kneading. This makes it necessary to adopt a molding method which requires the removal of a great volume of water by vacuum suction or by centrifugal separation. In comparison with a product according to the present invention, therefore, a product made by conventional methods is recognized to be quite different in appearance and strength as well as in EXAMPLE Mixture A (for making heat-insulating sleeves A):

(0.2 1 mm. dia.) 309? Silica Refractory brick scraps (Below 100 mesh) 20 71 Asbestos (Less than 3-- 5 mm. dia. & long) 40%. L Wood chips (Below 20 mesh) 10 7f 7 In addition to the above mixture: Phenol resin 6 7: of the V above mixture Water 75 '71 of the above mixture- Mixture B (for making adiabatic, exothermic sleeves Silica 25 7? Aluminum powder v 18 '71 Manganese dioxide l5 71 Asbestos (Less than 3 5 mm. dia. & long) 42 "/1 In addition to the above mixture:

Phenol resin 6 71 of the above mixture Water 7r of the above mixtu re By using Mixtures A and B and the method of the present invention, a sleeve l shown in FIG. 3 having an outside diameter of rnm., an inside diameter of 120 mm. and a height of 1 20 mm. was produced. The added volume of water for use in kneading at the third step was 75-100 percent, and the molding at the fourth step could be carried out by'using a core producing machine at the same rate as inithe production of cores of conventional type using'th e same machine. By drying in a gas dryer at C. for 2 hours, a heat-insulating sleeve A and an exothermic,-.heat-insulating sleeve B were produced with sufficient solidness. These results are compared with those obtained from tests conducted on sleeves made by conventional methods, as follows:

Table 1 compares the apparent specific gravity of these materials, calculated by using a formula:

Weight of sleeve Volume of sleeve 1. Sleeve C made by a conventional method contained no added fibrous materials, but was heatinsulating exothermic, and of nearly the same size as the sleeve of the present invention.

2. Sleeve D was also devoid of fibrous materials, and was heat-insulating, exothermic, and of nearly the same size as the sleeve of the present invention.

3. Mixture for the sleeve C; Aluminum powder 20 percent, aluminum ash 33 percent, iron oxide 9 percent, potassium nitrate 9 percent, silica powder 26 percent, cryolite powder 3 percent.

In addition to the above mixture: Water glass 10 percent by weight, solidified by the carbonic acid gas process and dried at about 120C.

4. Mixture for the sleeve D: Aluminum powder percent, aluminum foil and powder 5 percent, aluminum ash 42 percent, iron oxide 15 percent, potassium nitrate 10 percent, perlite powder 10 per cent, cryolite powder 3 percent.

In addition to the above mixture: Water glass 10 percent by weight, solidified by the carbonic acid gas process, and dried at about 120C.

Table 2 presents data comparing moisture resistance, of these materials.

TABLE 2 12 sult of using this sleeve B had almost no boiling of molten cast steel, with levelled surface and small size shrinkage cavities as shown at 28 of F in FIG. 5'. No sintering occurred as compared with the feeder heads E and G produced respectively by using the sleeves D and C, both made by conventional methods. I These feeder heads E, F and G had been cut off the castings. 7 As mentioned above, sleeves or sheets of the present invention are poorly water-absorbent, thus requiring no cover for moisture prevention. They can be used as molds as they are, or stocked for a long time. Besides, because of their light weight, they can be handled or transported without difficulty. Because of good heat insulation due to such light weight, a feeder head can maintain its temperature for a long period of time. Also, because of the very low heat absorption, they may be very slow in heat generation, making it possible to obtain an almost smokeless mixture, which is very Moisture prevention when exposed to air:

Water repellence by water absorption '71 (in water) Samples Test Right 5 hours 1 day 2 days 7 days 30 days State when placed Items after after after after after after on water drying Present A 07! 0% 0.7% 1.5% 2.0% 2.0% Floated for more Invention than 48 hours Present B 07: 07: 0.87r l.57r 2.0% 2.0% Floated for more Invention than 24 hours Conventional C 07 0.5% 1.571 2.0% above Strength Sank when placed products 2.0% lowered on water Conventional D 07: 0.7% 2.0% 2.0% Above Decom- Same as above products 2.07: posed 3. Strength: effective in preventing air pollution. The present inven- A test piece of 245 mm, wide and 25 mm, thick X 140 mm. long, was made from each of the sample sleeves. The transverse strength was measured of the following four test pieces:

Test piece A of the present invention: 20-25 kg/cm Test piece B of the present invention: 20-25 kg/cm Test piece C of conventional method: 25-28 kg/cm Test piece D of conventional method: l6-20 kg/cm 4. Heat-insulation characteristics:

A test piece of 210 mm. long X 210 mm. wide X mm. thick, was made from each of the sample sleeves. Heat insulation was measured of these four test pieces. One surface side was heated at 9001,000C., and the rise of temperature of the other surface side was measured, taking time into account as a factor. The test results are shown in FIG. 4. as follows: The test pieces A and B of the present invention had much slower rise of temperature than the test pieces C and D of the conventional methods, proving that the sleeve of the present invention has good heat insulation.

In FIG. 4, the curves at the upper part indicate respectively the temperature of the heated side of test pieces, and those at the lower part indicate respectively the temperature rise on the other side.

5. Results of other tests:

The result of use of the sleeve B of the present invention for casting cast steel was so good that, as shown in FIG. 5, a feeder head F produced as a retion is characterized by such a great advantage as continuous and automatic production of sleeves for great reduction of production costs.

As used in the appended claims, the term sheets for feeder heads is intended to encompass such sheets in either slab or sleeve form.

Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit and scope of the invention as set forth in the appended Claims.

Accordingly, what is claimed is:

1. An apparatus for producing feeder head sheets for use in metal molding, which comprises:

a cotton-opening and mixing in the dry state granular, refractory materials and fibrous materials;

a kneader for kneading, in the moistened state, the

materials cotton-opened and mixed by said cottonopening mixer; and

molding apparattus for molding, in a mold under air pressure, the materials kneaded by the kneader.

2. The apparatus claimed in claim 1, wherein said cotton-opening mixer consists of a tightly enclosed vessel with the axis of its trunk being perpendicular, a rotating shaft with its axis corresponding with the axis of the trunk more than two sets of rotating blades arranged vertically and provided on the rotatingshaft, these blades of each set extending horizontally and a device for driving the rotating shaft.

3. The apparatus claimed in claim 2, wherein the blades of the set at the lowest stage of said cotton-opening mixer are so twisted as to produce upward stream of wind.

4. The apparatus claimed in claim 1, wherein said kneader consists of a device for supplying an appropriate amount of water to the cotton-opened, mixed materials, and ofa screw conveyer for turning up and kneading the materials as these are being transported.

5. The apparatus claimed in claim 1, wherein said kneader consists of a tightly enclosed vessel, a rotating shaft provided in such manner as to run horizontally through said vessel, a plurality of kneading blades each set provided at a right angle on said rotating shaft, a device for driving the rotating shaft and a device for supplying an appropriate amount of water to the cottonopened, mixed materials.

6. The apparatus claimed in claim 5, wherein the kneading blades of said kneader are twisted so as to 14 produce such a horizontally driving force as to push the materials to the opposite side.

7. The apparatus claimed in claim 1, wherein the mold of said molding machine for use in producing cylindrical feeder head sleeves, is constructed with an inner metal mold and an outer metal mold, respectively, consisting of a thin-walled sleeve and a cylindrical frame for reinforcing the sleeve, such sleeves each having a great number of slender slits running in parallel with the axis of the sleeve.

8. The apparatus claimed in claim 7, wherein the sleeve of said mold is 2 to 3 mm thick, and each slit is 40 to 50 mm long and 0.2 to 0.4 mm wide.

Claims

1. An apparatus for producing feeder head sheets for use in metal molding, which comprises: a cotton-opening and mixing in the dry state granular, refractory materials and fibrous materials; a kneader for kneading, in the moistened state, the materials cotton-opened and mixed by said cotton-opening mixer; and molding apparattus for molding, in a mold under air pressure, the materials kneaded by the kneader.

2. The apparatus claimed in claim 1, wherein said cotton-opening mixer consists of a tightly enclosed vessel with the axis of its trunk being perpendicular, a rotating shaft with its axis corresponding with the axis of the trunk more than two sets of rotating blades arranged vertically and provided on the rotating shaft, these blades of each set extending horizontally and a device for driving the rotating shaft.

4. The apparatus claimed in claim 1, wherein said kneader consists of a device for supplying an appropriate amount of water to the cotton-opened, mixed materials, and of a screw conveyer for turning up and kneading the materials as these are being transported.

5. The apparatus claimed in claim 1, wherein said kneader consists of a tightly enclosed vessel, a rotating shaft provided in such manner as to run horizontally through said vessel, a plurality of kneading blades each set provided at a right angle on said rotating shaft, a device for driving the rotating shaft and a device for supplying an appropriate amount of water to the cotton-opened, mixed materials.

6. The apparatus claimed in claim 5, wherein the kneading blades of said kneader are twisted so as to produce such a horizontally driving force as to push the materials to the opposite side.