US3504732A - Apparatus for continuously casting metals - Google Patents

Description

April 7, 1970 A. J. WERTLI 3,504,732

APPARATUS FOR CONTINUOUSLY CASTING METALS Filed Sept. 5, 1967 lnvenlor:

A'IL. FRED J. WE? TL w EA TOR United States Patent 3,504,732 APPARATUS FOR CONTINUOUSLY CASTING METALS Alfred J. Wertli, 15 Poststrasse, 8406 Winterthur, Switzerland Filed Sept. 5, 1967, Ser. No. 665,616 Claims priority, application Switzerland, Sept. 3, 1966,

Int. Cl. B2241 11/12 US. Cl. 164282 Claims ABSTRACT OF THE DISCLOSURE The rollers which grip the emerging cast strand and advance the cast strand in a series of short rapid strokes are driven through a hydraulic motor. The hydraulic motor is operated in an intermittent manner through a pressure medium which is delivered to the hydraulic motor in similar intermittent manner.

This invention relates to an apparatus for continuously casting metals. More particularly, this invention relates to an apparatus for continuously casting metal in a horizontal direction.

Heretofore, in the horizontal continuous casting of metals utilizing at least one pair of gripping rollers to grip and intermittently advance a strand from a mold, the drive for the rollers has been provided by electric motors or by electric motors having electro-magnetic clutches. These motors have generally been switched off after each forward stroke of the rollers and then switched on again to feed the strand further forward by one stroke. However, since relatively long time constants occur upon starting and braking of the motors or upon engagement and disengagement of the electro-magnetic clutches, only a relatively few strokes per minute, for example, less than 40, can be carried out.

Since it has been shown that the homogeneity of the structure of a cast strand is better, the shorter the stroke and the more often the strand is fed forward by one stroke per unit of time, the number of strokes per unit time should desirably be increased considerably over the above-exemplified number. Further, the stroke should be smaller than the smallest cross-sectional dimension of the strand being cast.

Accordingly, it is an object of the invention to advance a cast strand from a mold in a series of small strokes at a rapid rate of strokes.

It is another object of the invention to dispense with electric motors or electric motors having electro-magnetic clutches for driving the gripping rollers advancing the strand.

It is another object of the invention to advance a cast strand from a mold in a series of intermittent strokes of from 1 to 20 mm. at a rate of 20 to 300 strokes per minute.

Briefly, the invention provides a continuous casting apparatus for withdrawing a cast strand horizontally from a casting mold of a furnace in a series of intermittent strokes. The apparatus includes at least one pair of gripping rollers for gripping the cast strand downstream of the mold, a hydraulic motor which is connected to at least one of the rollers to exert a rotary movement on the roller and a means for intermittently feeding a pressure medium to the hydraulic motor. Upon feeding of the pressure medium to the hydraulic motor, the motor causes the gripping rollers to rotate in a manner to advance the cast strand in a forward direction away from the mold. Upon completion of the pressure medium feed to the motor, the motor stops and correspondingly 3,504,732 Patented Apr. 7, 1970 stops the gripping rollers from advancing the cast strand. This effects one stroke of the cast strand. At the same time, the pressure medium is expelled from the motor and recycled. Thereafter, subsequent feeding of pressure medium to the hydraulic motor causes a repeated effect on the cast strand. The feeding of the pressure medium is carried out in a rapid intermittent manner while the hydraulic motor is started and braked with relatively small time constants so that a relatively large number of short strokes can be made.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a continuous casting apparatus of the invention; and

FIG. 2 illustrates a graph of the movement of a cast strand as a function of time.

Referring to FIG. 1, the continuous casting apparatus includes a furnace 1 containing a molten metal, at least one mold 2 disposed substantially horizontally near the base of the furnace 1, a cooling device 3 surrounding each mold 2 to cool the molten metal flowing through the mold 2 and a withdrawal unit 4 downstream of the mold 2. The molten metal in the furnace 1 flows into the mold 2, is cooled in the mold 2 by the cooling device 3 to solidify, and leaves the mold 2 as a strand 6 in the direction indicated by the arrow 7. The strand then passes through four pairs of gripping rollers which constitute the withdrawal unit 4 and passes onto a roller conveyor (not shown).

The gripping rollers of the withdrawal unit 4 are composed of upper clamping rollers 8 and lower rollers 9. The upper rollers 8 are mounted so as to be pressed against the strand 6 towards the lower rollers 9 and released from the strand 6 in a manner not shown in detail, for example, by a suitable electric, hydraulic or pneumatic means. The lower rollers 9 are operably connected to each other through an endless chain 10 which engages a suitable chain sprocket on each roller 9 and are driven through a shaft 11 connecting the foremost roller 9 to a gear 13 which is also coupled to a hydraulic motor 15 of known construction through a shaft 16. The hydraulic motor 15 connects with a pressure medium feed pipe 12 at one end and a pressure medium discharge pipe 14 at the other end. The gear 13 allows the use of a hydraulic motor having a number of revolutions which is, for example, 10 to 15 times higher than the lowest number of revolutions for driving the rollers and thus permits the dimensions of the motor to be made smaller. However, the gear 13 can be omitted and the foremost lower roller 9 can be coupled directly to the hydraulic motor 15.

The pressure medium feed pipe 12 is supplied with pressure medium from a reservoir 18 by means of a pump 17 which draws the pressure medium from the reservoir 18. The pump 17 feeds the pressure medium to the hydraulic motor 15 through a valve 19 and through a fiow regulator 20 which controls the quantity of pres sure medium fed to the hydraulic motor 15 under a pressure of, for example, 50 kp./sq. cm. The pressure medium actuates the hydraulic motor 15 so as to rotate the motor shaft 16. The rotation of the motor-shaft 16 causes rotation of the lower rollers 9 in a clockwise manner as viewed by way of the gear 13, shaft 11 and chain 10 transmission. Upon rotation of rollers 9, the upper clamping rollers 8 being simultaneously pressed against the strand 6, the strand 6 is moved in the direction indicated by the arrow 7. After performing the above work in the hydraulic motor 15, the pressure medium flows through the discharge pipe 14 back into the reservoir 18.

In order to move the cast strand in an intermittent manner, the valve 19 is periodically opened and closed by means of a rotatable cam 21 which is driven by a variable speed gear (not shown) and motor (not shown) The periodic opening and closing of the valve 19 effects the actuation of the hydraulic motor 15 by controlling the delivery of the pressure medium in the feed pipe 14 to the hydraulic motor 15.

In order to vary the number of strokes per unit time of the cast strand 6, the rotational speed of the cam 21 is varied. In addition, in order to alter the relation between the period of movement and the period of rest within each cycle T of the cam 21, different shaped cams are substituted for cam 21. For example, referring to FIG. 2, the cycle T which has a ratio B/R of period of movement to period of rest of 1:2 can be altered to have a period of movement to period of rest ratio B/ R of 3:1 as shown in dot-dash lines.

A magnetic valve operated by an electrical or electronic pulse generator can also be provided in place of the camcontrolled valve 19. With the aid of this impulse generator, the length of the cycle, the period of movement and the period of rest can likewise be varied in a simple manner.

The above-described apparatus can be modified so that both rollers 8, 9 of the pairs of gripping rollers are pressed against the strand 6. Also, instead of driving the chain, each lower roller 9 or several or all of the lower rollers 9 can be driven separately by its own hydraulic motor. Further, any number of the upper roller 8 can be moditied to be driven. If several rollers are driven by their own motor, the motors are connected in parallel so as to increase the torque acting on the moving strand.

It hasbeen found with the invention that the time constant of the hydraulic motor when starting and braking is very small. Thus, the use of such a motor for driving the rollers Withdrawing the strand makes it possible to cast a strand at considerably higher casting speed than hitherto, e.g., at 200 to 300 strokes per minute, each stroke of which has a length of only 1 to 20 mm. The strand will thus have a very uniform and fine structure.

With the apparatus according to the invention, it is further possible, in a simple manner and within one individual cycle to vary the period of movement and the period of rest of the strand and, moreover, to vary even the length of the cycle itself. This is advantageous insofar as it thus becomes possible to adapt the operation of the apparatus to the properties of the pure metals and alloys to be cast. Also, any variation of the length of the cycle and the period of movement and rest within each cycle can be carried out while the apparatus is in operation. Additionally, a further continuous feeding of the strand can be carried out.

What I claim is: I

1. An apparatus for the continuous casting of metals comprising 4 a furnace for containing a molten metal,

a mold connected to said furnace for forming a cast strand,

at least one pair of gripping rollers spaced from said furnace for gripping a cast strand emerging from said mold therebetween, and

means for rotating said pair of gripping rollers to intermittently advance the cast strand away from said mold, said means including a hydraulic motor operably connected to one of said pair of gripping rollers to rotate said one gripping roller upon actuation and means for intermittently feeding a pressure medium to .said hydraulic motor to actuate said hydraulic motor, said means for feeding a pressure medium including a regulator for varying the quantity of pressure medium fed to said hydraulic motor.

2. An apparatus as set forth in claim 1 wherein said means for feeding a pressure medium includes a valve for controlling the feeding of pressure medium to said hydrauiic motor and a means for periodically opening and closing said valve to correspondingly intermittently actuate. said hydraulic motor.

3. An apparatus as set forth in claim 2 wherein said means for periodically opening and closing said valve includes a rotatably mounted cam operatively connected to said valve for periodically opening and closing said valve upon rotation thereof.

4. An apparatus as set forth in claim 1 wherein said means for rotating further includes a gear operatively connected between said hydraulic motor and said one gripping roller for changing the gear ratio between said motor and said one gripping roller.

5. An apparatus as set forth in claim 1 which comprises a plurality of pairs of gripping rollers for gripping the cast strand and said means for rotating further includes an endless chain operatively connected to one roller of each of said pairs of gripping rollers for simultaneously rotating said rollers in response to rotation of said one roller through said hydraulic motor.

References Cited UNITED STATES PATENTS 2,667,673 2/1953 Harrison 164282 X 2,938,501 5/1960 Titcornb 9139 X 3,107,404 10/ 1963 Armand et al 164-70 FOREIGN PATENTS 1,060,910 4/1954 France.

1,395,479 3/1965 France.

J. SPENCER OVERHOLSERJrimary Examiner R. S. ANNEAR, Assistant Examiner

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