US 3277540 A
Description (OCR text may contain errors)
E. BUHRER Oct. 11, 1966 DEVICE FOR REFINING FOUNDRY SAND IN A CONTINUOUS MANNER Filed Sept. 6, 1963 INVENT OR ERWIN BUHRER ATTORNEY United States Patent 3,277,540 DEVICE FOR REFINING FOUNDRY SAND IN A CONTINUOUS MANNER Erwin Biihrer, Breitenaustrasse 164, Schafihausen,
' Switzerland Filed Sept. 6, 1963, Ser. No. 307,233 Claims priority, application Switzerland, May 2, 1963, 5,561/ 63 1 Claim. (Cl. 22-89) The present invention relates to an apparatus for reclaiming foundry sand in a continuous manner while employing a rotatable unilaterally closed drum with inclined axis, the length of said drum being less than the diameter of the drum.
It is a well-known fact that in molds containing the cast metal, the foundry sand directly adjacent the cast piece is heated to a considerable extent. With increasing distance from the cast piece, the temperature of the sand decreases. In the remote said layers in which the temperature of the foundry sand reaches the condensation temperature of the water steam or is even below said temperature, an over-humidified sand layer is encountered.
Therefore, when emptying a mold, in addition to hot sand which is completely dry, there is also obtained the sand of a relatively low temperature which is strongly over-humidified. The strongly over-humidified portion of the foundry sand has the tendency to form clumps of different sizes when it intermixes with the dried-out sand, for instance when the sand is handled. Since, however, for the further reclaiming of the sand, it is of importance that the sand is as free from clumps as possible and has a substantially uni-form humidity and temperature, numerous attempts have been made to obtain this desirable condition. Attempts to obtain a certain uniformity and equalization by means of a paddle mixer have failed. The application of vibration troughs feeding the sand to a transversely moving conveyor belt likewise failed to yield satisfactory results. Mixing drums open at both sides and having a length in excess of the diameter of the drum, in which the sand is introduced into the drum at one. side thereof and is withdrawn from the drum at the other side thereof, have proved to be unable to produce a suflicient mixing effect.
For purposes of mixing granular material there has been developed a device comprising a rotating mixing bowl open at the top and adapted to have its rotating shaft adjusted along an incline, while a rotating agitator is eccentrically arranged with regard to the axis of the mixing bowl. This device could realize the desired mixing set forth above only by means of an agitator which latter, however, is liable to considerable and fast wear in view of the grinding effect of the sand.
If the foundry sand is subsequently to be cooled in a device, a prior humidification is indispensable. However, when humidifying greater quantities of foundry sand, the ditficulty is encountered that differently sized clumps are formed and that the difference in the size of the clumps is even greater than is the case with the sand being withdrawn from the mold following the casting. In this connection, the fact makes itself felt that the hot sand is water-repellent and therefore can only be poorly humidified.
In foundries it is unavoidable that also molds containing no casting have to be emptied. The foundry sand encountered in such instances is not hot but cold and is not dry but humid. Efforts have been made to mitigate this sudden change of the properties of the foundry sand by the installation of silos.
It is, therefore, an object of the present invention to overcome the above mentioned drawbacks.
It is another object of this invention to provide an apparatus for reclaiming foundry sand in an uninterrupted manner which will make it possible to assure a uniform humidification of the sand without the formation of undue clumps.
It is another object of this invention to provide an apparatus for reclaiming foundry sand in an uninterrupted manner which will make it possible to secure a uniform temperature of the sand without the formation of undue clumps.
It is still another object 'of this invention to provide an apparatus as set forth above, which will make it possible to introduce into the mixing drum not only the water required for a subsequent cooling of the foundry.
sand but additionally the total quantity of water required by the sand for all reclaiming processes without the formation of undue clumps.
It is still another object of this invention to introduce into the mixing drum slurry consist-ing e.g. of bonding clay, coal dust or other substances without formation of undue clumps.
It is a further object of the invention to provide an apparatus which will make it possible to decrease the temperature of foundry sand to at least Celsius during the passage of the foundry sand through the mixing drum.
These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:
. FIG. 1 diagrammatically illustrates a top view of an apparatus according to the present invention.
FIG. 2 is a vertical section taken along the line IIII of FIG. 1 but with the addition of an insulating layer around the drum to protect the same against heat loss.
FIG. 3 diagrammatically illustrates the operating effect of an apparatus according to the present invention.
The above mentioned objects have been realized and the outlined disadvantages have been overcome [by an apparatus according to the present invention which comprises a rotatable unilateral drum the axis of which is inclined with regard to the horizontal plane and in which the length of the drum is less than the drum diameter. This apparatus according to the invention differs from heretofore known devices of the type involved in that the axis of the drum is inclined with regard to the horizontal plane by an angle of from 5 to 30. Furthermore, driving means are provided which impart upon the drum a speed of rotation at which the pourable goods introduced into the drum and partially in a free fall, fall through the interior of the drum.
Referring now to the drawings in detail, the apparatus illustrated therein comprises a drum 1 the axis of which is inclined with regard to the horizontal plane by an angle of approximately 30. The said drum 1 has a bottom 2 and a shaft 3 rotatably journalled in bearings 4. The drum 1 is adapted to be rotated by means of a motor 5, a transmission 6 and chain drive 7. Drum 1 is, at its open side, provided with a flange or retainer wall 8 the height of which determines the quantity of the sand 9 it can hold. A conveyor belt 10 adjacent the opening of drum 1 senves for continuously feeding foundry sand into the drum, while a conveyor belt 11 takes care of the continuous withdrawal of the sand discharged above the inner periphery of the flange or retainer wall 8. A pipe 12 equipped with a nozzle 13 at one end thereof serves for the feeding of water or if desired simultaneously also of a clay-like binder and coal dust or other substances, for instance in the form of slurry, into the drum.
The apparatus illustrated in the drawings is furthermore provided with a adjusting device, generally designated 14 by means of which the inclination of the axis of drum 1 with regard to the horizontal plane may be varied in a manner known per se.
There is furthermore provided a heating device by means of which the back side of drum 1 may be heated. Such heating device may be of any suitable type, for instance -a heated radiating body. The transmission 6 is an infinitely variable transmission of any conventional type, for instance of the type set forth in German Patent No. 898,837 that is equipped with a handwheel 16, by means of which the transmission 6 may be varied in a stepless mannerto thereby adjust the proper speed of drum 1.
The operation of the apparatus according to the invention is illustrated in FIG. 3. The speed of rotation of drum 1 and the inclination of the axis of the drum relative to a horizontal plane are partially dependent on the type and the composition of the foundry sand to be reclaimed. When the speed of rotation of the drum and the inclination of its axis has been properly selected, with a unilaterally closed drum as illustrated in the drawing, the foundry sand in said drum is sub-divided into so to speak three sections or portions.
One section 17 of the sand introduced into the drum will when, during the rotation of the drum exceeding the angle of heaping, slide back in an avalanche-like manner. A further section or portion 18 of the sand will slide along the drum bottom 2 and back into its starting position and will impact upon the sliding-off portion 17 in the respective lowermost part of the drum wall. A third portion 19 of the sand which, together with the drum wall 1, moves close to the latter,'is carried beyond the angle of heaping and so to speak as a sand rain will in a free fall drop into the portions 17 and 18. This operation will assure a particularly and intensive and quick intermixture of the sand in the drum. The thus reclaimed sand will, during the rotation of the drum in a continuous manner, pass over the respective lower retaining wall section 8 (shown in FIG. 3) and be discharged onto a conveyor belt 11 by which it may be moved to a desired location.
According to the embodiment of FIGS. 1 to 3, Water is introduced into the sand in the drum by means of a pipe line 12 and a nozzle 13 at the end adjacent said drum.
It has been found advantageous to make the bottom 2 of the drum conical so that it will taper in the direction toward the shaft 3. This arrangement yields an intensive intermixture of the sand portion 17 with the sand portion 18 (FIG. 3) of the sand introduced into the drum.
In order to prevent the foundry sand from sticking to the inner side of the drum, for instance to the drum bottom, it is advantageous to provide the drum with a heating device. In the particular example shown in FIGS. 1 and 2, the drum bottom only is adapted to be heated by heat radiation. Portions of the drum which are not heated may advantageously be provided with a heat insulation 21.
If desired, the mixing eifect of the drum on the sand therein may be further increased by selecting the angle on (FIG. 2) formed by a generatrix of the conical drum bottom 2 with a plane perpendicular to the axis of drum shaft 3 so that the angle or will be greater than the angle of inclination B, i.e. the angle confined by the drum shaft 3 with a horizontal plane.
By means of the device according to the present invention, it will be possible to introduce into the drum not only the water required for a successive cooling of the foundry sand but additionally the total quantity of water required by the sand for all reclaiming operations, and furthermore to introduce the bonding clay, the coal dust or other substances, and the temperature and the moisture of the foundry sand will be equalized in one and the same device. In this way, the mixing operation of the sand which normally is expensive can be efiected in a considerably shorter time.
A device according to the present invention has the further advantage that sudden changes in the state of the sand for instance by admixing thereto the sand of molds which had not been poured with liquid metal will be equalized and will more properly be controlled automatically.
It is of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawings but also comprises any modifications within the scope of the appended claim.
What I- claim is:
In an apparatus for refining foundry sand continuously, a drum open at one end and closed at the opposite end and having a length less than its diameter, a rotatable shaft for rotating said drum connected to said closed end of said drum and inclined with regard to a horizontal plane at an angle between 5 and 30, the closed end of said drum forming the drum bottom, the major portion of said bottom having a conical shape tapering from its periphery toward said shaft at an angle to a plane perpendicular to the axis of said shaft greater than the angle between said shaft and a horizontal plane, said drum also having a cylindrical, peripheral side wall extending axially from said closed end parallel to said axis of said shaft, and an end flange on the outer end of said cylindrical side wall extending axially inwardly, said drum being adjustably mounted with said cylindrical side wall at its lower side inclined upwardly and outwardly, said end flange with said cylindrical side wall and said closed end forming a reservoir portion at the lower side of said drum for a substantial amount of material above the level of the outer end of said cylindrical side wall, means to deliver foundry sand to said drum at one side of the axis of rotation to fall freely into one side of said reservoir portion, and means to supply water to said reservoir portion, so that said sand falls back into said reservoir portion as said drum rotates and said water mixes with the sand in said reservoir portion until the mixture over flows said end flange.
References Cited by the Examiner UNITED STATES PATENTS 1,666,324 4/1928 Burn et al. 259-176 1,666,577 4/ 1928 McCabe 2226 1,905,490 4/1933 Norrick 2225 2,176,874 10/ 1939 John 259--177 2,573,296 10/ 1951 Arant 2225 2,707,314 5/1955 Horth 22217 2,783,511 3/1957 Will et al. 22217 2,877,524 3/1959 Bishop 22-89 3,060,496 10/ 1962 McDowell et al. 51163 3,151,368 10/ 1964 Dietert 2289 FOREIGN PATENTS 446,205 1/ 1948 Canada.
5,756 3/ 1906 Great Britain. 311,428 5/ 1930 Great Britain. 361,700 11/1931 Great Britain.
.1. SPENCER OVERHOLSER, Primary Examiner.
MARCUS U. LYONS, Examiner.
R. D. BALDWIN, Assistant Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 3,277,540 October 11, 1966 Erwin BL'lhrer It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
In the sheet of drawings the lower right-hand corner thereof, for "ATTORNEY" read AGENT Signed and sealed this 22nd day of August 1967.
ERNEST W. SWIDER EDWARD J. BRENNER A'ttesting Officer Commissioner of Patents