Title:
Apparatus for treating metals
United States Patent 2198637


Abstract:
The present invention relates to apparatus for the treatment of metals, particularly molten metals during solidification, in order to obtain a fine-grained structure in the solidified metal. More particularly the present invention relates to an apparatus for vibrating metal-containing molds...



Inventors:
Smith, Edward W.
Application Number:
US24761038A
Publication Date:
04/30/1940
Filing Date:
12/24/1938
Assignee:
SUBMARINE SIGNAL CO
Primary Class:
Other Classes:
29/252, 99/348, 310/29, 366/108
International Classes:
B22D27/08
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Description:

The present invention relates to apparatus for the treatment of metals, particularly molten metals during solidification, in order to obtain a fine-grained structure in the solidified metal. More particularly the present invention relates to an apparatus for vibrating metal-containing molds or crucibles.

Various forms of apparatus for this purpose were shown in my United States Patent No. 2,116,367, granted May 3, 1938. In that patent I pointed out the desirability of constructing a mold-vibrating, apparatus as a two-mass resonant vibratory system composed of two freely vibratable independent mass elements and an elastic ]5 element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, one of the mass elements including the container for the molten metal and the other mass element being a compensating mass.

SIn this system the elastic element is given a sufflcient elasticity to make the vibratory system resonant at the desired frequency of vibration.

The present invention also relates to vibrating apparatus of the type in which a two-mass resonant vibratory system is employed and particularly 25 to such a system in which the mold is to be vibrated along a vertical axis. The present invention provides an improved arrangement for supporting the mass elements of the vibratory system.

The invention will best be understood from the following description taken in connection with the accompanying drawing which shows schematically the arrangement in accordance with the invention.

In the drawing the container for the molten metal such as a mold or crucible is shown at I.

The mold is supported and rigidly fixed in any suitable manner to a table 2. The table 2 is arranged so that it can execute substantially free 40 vertical vibrations by being mounted on leaf springs Z of which there may be any suitable number The leaf springs have their outer ends fixed, as by the bolts 4, to steel members 5 which are firmly fixed to the floor or other portion of the 45 foundry. They may, for example, as shown in the drawing, be embedded in the concrete walls 6 of a well formed in the foundry floor. A compensating mass 7 is similarly supported on leaf springs 8. The compensating mass preferably has a mass substantially equal to the mass of the mold plus ancillary elements which move therewith. The two masses are coupled together by a coil spring 9 which has a sufficient stiffness to make the system resonant at the desired frequency of vibration. This frequency can be determined mathematically from the formula 1= 1n--m1m2 where w=27r times the frequency, u is the stiffness 6 of the spring and mi and m2 are the two mass elements; mi may, for instance, comprise the mass of mold I and its contents plus the mass of the table 2 plus the mass of all the ancillary elements directly connected thereto and which vibrate together in phase. Similarly the mass m2 comprises the mass of the compensating element plus the mass of all the ancillary elements which are connected to it and move in phase with it. Now, n order to preserve as nearly as possible the theoretically perfect requirement that both masses be free to vibrate, it is necessary that the leaf springs 3, 8 which support the masses have as small a stiffness as possible. This is necessary particularly to avoid the transmission of vibratory energy to the building or foundations. I have found that the leaf springs form a satisfactory suspension for the vibratory system if they have a total stiffness not substantially greater than one-fifth of that of the coupling 25 spring 9.

It will be understood that the vibratory system just described may be set into vibration by any suitable means. I prefer, however, to use an30 electromagnetic driving arrangement as shown in the drawing. To this end, a guide rod i0 is fixed to the table 2 and projects into an aperture SI in the compensating mass 7. Fixed to the rod 10 is the armature 12 of the electromagnetic system. Below the armature is a plug 3 also fixed 35 to the rod 10. This plug has its external surface cut in a helix to fit inside one or more turns of the spring 9. By this means one end of the spring 9 is firmly fixed both to the armature and the table 2. The other end of the spring 0 is ` fastened to a similar plug 14 which is fixed to the compensating mass 7. The mass 7 also carries the field magnet 15 having one or more windings 16. The magnet 15 may be fixed to the mass 7 by means of the bolts 17.

When the coil 16 is energized by -alternating current, the field magnet 15 and the armature 12 will move relative to each other along the vertical axis. The masses mi and m2 will, therefore, move toward and away from each other at twice the 50 frequency of the alternating current supplied to the coil 16. This frequency is preferably chosen to drive the vibratory system at substantially the resonant frequency of the vibratory system. The 5 resonant frequency will, of course, vary somewhat with variations of the amount and kind of metal in the mold I. If the frequency variation so caused is small, the vibrational amplitude may not be seriously diminished. However, if a serious frequency change occurs, it is merely necessary to vary the frequency of the alternating current supplied to the coil 16 until the new resonant frequency is reached.

If a mechanical drive is used to impart vibrational energy to the system, as by means of a motor driven eccentric shaft connected to the mold, a change in the mass of the contents of the mold will not change the amplitude of the mold since this is fixed by the mechanical drive, but will change the resonant frequency. If this change is not too great, no change in the driving motor speed is required, although the load on the driving motor will be increased as the difference between the resonant frequency and the driving frequency increases.

SHaving now described my invention, I claim: 1. Apparatus for vibrating a container for molten metal comprising a two-mass resonant vibratory system composed of two substantially freely vibratable elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the effective mass of one of said mass elements including the mass of the metal, the mass of its container and the mass of ancillary elements adapted to move therewith, said elastic element having sufficient elasticity to make the vibratory system resonant at the desired frequency of vibration and resilient means for separately supporting each of the two mass elements of the said vibratory system, the total stiffness of the said resilient means being small compared to the stiffness of the said elastic element, 2. Apparatus for vibrating a container for molten metal comprising a two-mass resonant vibratory system composed of two substantially freely vibratable mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the effective mass of one of said mass elements including the mass of the metal, the mass of its container and the mass of ancillary elements adapted to move therewith, said elastic element having sufficient elasticity to make the vibratory system resonant at the desired frequency of vibration and resilient means for separately supporting each of the two mass elements of the said vibratory system, the total stiffness of the said resilient means being substantially one-fifth of the stiffness of said elastic means.

3. Apparatus for vibrating a container for molten metal comprising a two-mass resonant vibratory system composed of two substantially freely vibratable mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the effective mass of one of said mass elements including the mass of the metal, the mass of its container and the mass of ancillary elements adapted to move therewith, said elastic element having sufficient elasticity to make the vibratory system resonant -at the desired frequency of vibration and resilient means I for separately supporting each of the two mass elements of the said vibratory system, said resilient means comprising a plurality of leaf springs, each fixed by one end to a support and by the other end to one of said mass elements. 4. Apparatus for vibrating a container for molten metal comprising a two-mass resonant vibratory system composed of two substantially freely vibratable mass elements and an elastic element fixed at one end to one of said mass elements and at the other end to the other of said mass elements, the effective mass of one of said mass elements including the mass of the metal, the mass of its container and the mass of ancillary elements adapted to move therewith, said elastic elementhaving sufficient elasticity tomake the vibratory system resonant at the desired frequency of vibration and resilient means for separately supporting each of the two mass elements of the said vibratory system, said resilient means comprising a plurality of leaf springs, each fixed by one end to a support and by the other end to one of said mass elements and having a total stiffness not substantially' greater than one-fifth of the stiffness of said elestic element. 5. Apparatus for treating metal comprising a rigid support, a plurality of leaf springs, means mounting each of said springs by one end to said support, a container for molten metal, means mounting said container upon the free ends of a 4C group of said springs, a mass element having a mass approximately equal to the mass of said container when filled, means mounting said element on the free ends of the remaining leaf springs, a helical spring, means connecting one 4V end of said helical spring to said container and the other end to said mass element, electromagnetic means for vibrating said container and said mass element, said helical spring having a stiffness equal to W2 times the product of the 5( mass of the filled container plus elements which move therewith and the mass of said mass element plus elements adapted to move therewith divided by the product of the said masses where w is equal to 2r times the frequency of vibration 5: and said leaf springs having a total stiffness not substantially .greater than one-fifth of the stiffness of said helical spring.

EDWARD W. SMITH. 6(