US3319899A

US3319899A - Crust breaking device for electrolysis furnaces

Info

Publication number: US3319899A
Application number: US348520A
Authority: US
Inventors: Strom Johan Nikolai; Heggstad Gudmund
Original assignee: Alcan Aluminum Ltd
Current assignee: Rio Tinto Alcan Inc
Priority date: 1963-03-04
Filing date: 1964-03-02
Publication date: 1967-05-16
Anticipated expiration: 1984-05-16
Also published as: GB1017163A; FR1383632A; DE1235001B; CH402423A; AT268708B; NL6402147A; SE314524B

Description

y 16, 1967 J. N. sTROM ETAL 3,319,399

CRUST BREAKING DEVICE FOR ELECTROLYSIS FURNACES Filed March 2, 1964 C 8 o o .2 9 i s o Iwear ls 4% haw United States Patent 9 Claims. a. 241-283) The present invention relates to means for the breaking of the crust which is formed on the top surface of the electrolyte bath during the operation of electrolytic furnaces, for example aluminum extraction furnaces, for the purpose of enabling the supply to the bath of such substances, in particular aluminum oxide, as are required for the operation of the furnaces.

There are known a plurality of devices, both manual and mechanical, for this purpose, some in combination with means for the feeding of oxide and other substances which are to be supplied to the furnaces.

The present invention relates to a crust breaking device which is to operate with the least possible manual attendance and which will cause a minimum of noise and dust formation. According to the invention, this aim is achieved by arranging that the device is adapted for continuous movement along a row of furnaces during the crust breaking and comprises an arm which extends transversely to the longitudinal axis of the row and is pivotally mounted, at the end :remote from the furnaces, about a horizontal axis extending parallel to the length of the row of furnaces, and a head which is situated at the free end of the pivotable arm and is adapted to act upon the furnace crust during the movement of the device. Thus, with the device of the invention, the crust is not broken by any crow bar or chisel action, such as in the case of the conventional crust breakers, but the crust is forced downwardly by the head of the pivotable arm which subject the crust to repeated blows, or may roll on the same.

Conveniently, the device is such that the arm, with its head, is given a rhythmically oscillating motion in a vertical plane, so that the head exercises an impact action, as a sledge, against the crust. If the head is formed as a wheel, it may be provided with projections spaced along the circumference and may also be caused to perform a positive turning movement about the axis of the pivotable arm. 7

A mentioned, the device is also such that the head may roll on the crust. Thus, the weight of the head and the arm may be suflicient to develop a suflicient pressure to break down the crust, but it may also be convenient to make provision that the arm with the head is subjeoted to a positive downward pressure for the purpose of securing a sufiicient breaking force of the head against the crust.

For the purpose of taking into consideration a variable hardness of the crust, i.e. a variable resistance met by the head, it is convenient to connect the pivotable arm with its activating means through a spring device. This spring device conveniently, when the head is impacting the crust, i.e. when the arm is exercising a rhythmic oscillating movement, is so made that the device provides softer spring action during upwardly directed arm movements than during downward-1y directed movements, to the end that sharp downwardly directed blows, but less abrupt upward movements, are obtained. With a fixed, nonrolling head, the spring action of the arm may also be supplemented with anelastic support in the direction of progression of the device, in order that the arm is not subjected to horizontal breaking forces.

When in operation, the wheel formed head of the pivotr. 3,319,399 Ce Patented May 16, 1967 able arm may roll on and in the crust during its breaking activity. For this reason, the arm is adapted to perform a free or a positive rotational movement about its own axis.

The entire device is preferably adapted for automatic operation and, for this purpose, is provided with electrical or other contacts which, in cooperation with stationary contacts, cause starting and stopping of the various movements, such as when the device is passing from one furnace to the next during its movement along the row of furnaces or when changing over from impacting to rolling.

The invention is now to be further explained with ref erence to the annexed drawing which illustrates :an embodiment of a crust breaker in operational position adjacent to one electrolysis furnace of an aligned row of furnaces.

The whole crust breaking device is carried by a framework 1, which may be so constructed as to have one leg to either side of ta row of the furnaces 5. The framework 1 is mounted on wheeled trucks 2 driven by means of an electric motor 3, so that the device may be run in both directions along the row. The framework is provided with a current collector (not shown) which in cooperation with conductors in the furnace building provides for current supply to the various drives of the device.

An arm 7 is mounted in the frame 1 and extends transversely to the longitudinal axis of the row of electrolytic furnaces, and the arm 7 is, at its free end, provided with a head 8 in the form of a wheel the circumferential face of which is suitably formed for the breaking of the furnace crust. Thus, the head may be provided with ribs, as shown. At the end of the arm 7 which is situated remotely from the furnace the arm 7 is pivotably mounted in the frame 1 by means of a universal connection 9, so that the arm may pivot in a vertical plane and, at the same time, rotate about its own axis.

For the purpose of applying a vertical pressure to the arm and thereby increasing the force of the head 8 on the crust in addition to its own weight, the arm 7 is, through a

rod system

10, 11, 15, connected with a driving device 12, the rod 11 being conveniently and as shown in the form of a leaf spring unit.

The device 12 may be of such a type as to apply a continuous though variable pressure on the arm 7, whereby the head 8 will force the crust downwardly while rolling forwardly in the longitudinal direction of the row of furnaces. In the example shown, the device 12 is in the form of a hydraulic motor which may provide a cont nuous downward pressure or may cause the rod 10 to perform a reciprocal vertical movement, 50 that the arm 7 will perform a rhythmic oscillating movement in a vertical plane and thereby cause the head 8 to deliver sledge blows against the crust for the purpose of breaking the same downwardly into the furnace bath.

The leaf spring unit 11 is constituted by a plurality of superimposed leaf springs, so dimensioned that the arm 7 is not subjected to any appreciable resistance when moving upwardly, but is provided with an enhanced force in its downwardly directed movement, the tension of the leaf springs being utilized during the downward movement to provide an additional force in the blow. The lower leaf springs (are stiffer and consequently accommodate the pressure from the head 8 when the same is easily penetrating the crust. In the opposite case, if the head doe not penetrate the crust on the first blow, the upper springs yield so that the rod 10 may accompany the motor 12 during its further rotation along the lower half of the crank circle.

The drawing also indicates a silo 4 mounted in the frame 1 to receive oxide or other material which is to be supplied to the furnace through the opening in the crust broken by means of the head 8. The silo 4 ends in a valve or sluice 13 provided with a feed tube 14 extending to the surface of the bath.

The device of the invention functions in the following manner: The initial position of the device is at the end of a row of furnaces. When an electric switch is manually closed, the device starts to advance towards the first furnace of the row. The arm 7 with the head 8 is then at rest in a raised position. When the device has arrived at the adjacent end of the first furnace a contact carried by the frame 1 engages a corresponding contact mounted on the furnace closes the circuit for the drive of the hydraulic motor 12 and also actuates a delay device for the temporary stopping of the drive motor 3. The delay device is such that the motor 3 may be stopped instantaneously, but starts after a short interval.

The head 8 is now forced downwardly against the crust under the influence of the motor 12 and performs a short series of sharp blows to the crust. At the same time the motor 3 is stopped so that the device does not move as a whole. When the head 8 penetrates the crust, the arm 7 adopts a low position in which it actuates a contact 21 for the purpose of stopping the motor 12 with the crank in its lowermost position. At the expiration of the aforesaid delay time the motor 3 is started and moves the whole device forwardly along the furnace, at the same time as the head 8 is forced against the crust while rolling along the same. If the crust is not broken down, by such rolling, i.e. if the contact 21 is not yet closed, the rhythmic blow activity is continued during the advance of the device until the contact 21 is closed. When the crust is broken, the head 8 remains in the lower position while the device advances so that the crust is rolled down as long as it is relatively soft. If the crust becomes harder, the head 8 will climb and the spring 11 will increase the pressure of the head against the crust. If the crust should be so hard that the head 8 climbs to the top surface of the same, the contact 21 is opened and the motor 12 re-started and causes the head 8 to deliver sledge blows on the crust, whereupon the cycle is repeated as described above.

When the device reaches the opposite end of a furnace a further contact is closed so that the motor 12 causes the head 8 to stay in raised position, while the motor 3 advances the device to the next furnace.

The charging of oxide is effected when a contact in the device cooperates with a fixed contact mounted on the furnace, whereby the feed sluice 13 is activated and passes oxide from the silo 4, through the tube 14 into the opening made by the head 8 in the crust of the bath. Conveniently, the contacts of the sluice 13 and the motor 12 are made interdependent, so that the sluice is not open while the head is acting as a sledge, i.e. until an opening is formed. The sluice 13 is closed as the device reaches the end of each furnace. In this manner the device is advanced from one furnace to the next along the Whole row, whereupon the device may be moved over to a second furnace row.

When the head 8 is fixed, i.e. not rolling, the arm 7 performs a combined movement, similar to that of an oar during rowing. When the head hits the crust but does not move along the same, while the entire device is advanced along the furnace, the arm 7 is subjected to a horizontal pivotal movement relative to the device as a whole. This horizontal movement is accommodated by a pressure spring mounted to either side of the arm, so that the arm is straightened each time the head is raised from the crust.

Obviously, the device may be adapted for manual control, instead of being provided with the contacts referred to above, and it may also be provided with various instruments and meters for the supervision of the operation.

We claim:

1. A crust ibreaking device for use with electrolysis furnaces, including means for producing continuous movement of the device alongside the furnace during the crust breaking and comprising an arm which extends transversely to the direction of said movement and is pivoted at the end remote from the furnace for movement about a horizontal axis extending parallel to the said direction, and a head mounted at the free end of the pivoted arm and adapted to act upon the furnace crust during the movement of the device.

2. A device as claimed in claim 1, comprising means for causing the pivoted arm to perform a rhythmic oscillating movement in a vertical plane.

3. A device as claimed in claim 1, comprising means for applying a vertically directed pressure to the pivoted arm.

4. A device as claimed in claim 1, comprising spring means associated with the pivoted arm.

5. A device as claimed in claim 1, comprising spring means associated with the pivoted arm and adapted to exercise a stronger resistance to upwardly than to downwardly directed movements of the arm.

6. A device as claimed in claim .1, said arm being pivoted at said end for movements about a vertical axis, and

comprising spring means associated with the pivoted arm and arranged to either horizontal side of the pivoted arm.

7. A device as claimed in claim 1, wherein the pivoted arm is mounted for rotation about its own longitudinal axrs.

8. A device as claimed in claim 1, comprising drive means adapted to rotate the pivoted arm about its longitudinal axis.

9. A device as claimed in claim 1, wherein the pivoted arm is provided with electrical contact means adapted to cooperate with stationary contact means.

References Cited by the Examiner UNITED STATES PATENTS 1,888,032 11/1932 Fischer 15--104.1 1,921,503 8/1933 Calderwood 17312l X 2,731,892 1/1956 Simmonds 173121 X 2,732,197 1/1956 Cornett 17322 X 2,803,445 8/ 1957 Borrowdale 241277 3,030,713 4/1962 Hendrickson 17322 X 3,038,160 6/1962 Critchley 173121 X WILLIAM W. DYER, JR., Primary Examiner.

H. F. PEPPER, Assistant Examiner.

Claims

1. A CRUST BREAKING DEVICE FOR USE WITH ELECTROLYSIS FURNACES, INCLUDING MEANS FOR PRODUCING CONTINUOUS MOVEMENT OF THE DEVICE ALONGSIDE THE FURNACE DURING THE CRUST BREAKING AND COMPRISING AN ARM WHICH EXTENDS TRANSVERSELY TO THE DIRECTION OF SAID MOVEMENT AND IS PIVOTED AT THE END REMOTE FROM THE FURNACE FOR MOVEMENT ABOUT A HORIZONTAL AXIS EXTENDING PARALLEL TO THE SAID DIRECTION, AND A HEAD MOUNTED AT THE FREE END OF THE PIVOTED ARM AND ADAPTED TO ACT UPON THE FURNACE CRUST DURING THE MOVEMENT OF THE DEVICE.