US3442145A - Oscillation drive mechanism - Google Patents

Description

y 6, 1969 H. LEMPER 45 OSCILLATION DRIVE MECHANISM Filed Aug. 8. 1967 z/vmwmaa ilk/ 601 6 lie/22,001?

y 6, 1969 H. LEMPEIQ 3,442,145

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United States Patent 3,442,145 OSCILLATION DRIVE MECHANISM Herbert Lemper, Pittsburgh, Pa., assignor to Mesta Machine Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 8, 1967, Ser. No. 659,210 Int. Cl. B22d 27/08; F16h 25/08, 54/04 U.S. C]. 74-54 8 Claims ABSTRACT OF THE DISCLDSURE An oscillation drive mechanism is disclosed particularly for use in oscillating the mold structure of a continuous casting machine and for analogous applications. The mechanism includes an output cam member having a plurality of generally parallel camming surfaces thereon. The cam member is keyed for rotation with an elongated output shaft but is slidably movable therealong to juxtapose a selected one of the camming surfaces to a cam follower. The camming surfaces can be individually shaped to produce a substantially similar movement of the cam follower in one direction at a given rotational speed of the cam member but to produce correspondingly differing rates of cam follower movement in the opposite direction at such given rotation speed. The oscillation drive mechanism is particularly useful in connection with a continuous casting machine wherein the mold structure may be driven at different rates in the forward direction depending upon the casting speed but desirably is returned as quickly as possible in the opposite direction irrespective of casting speed for maximum production.

The present invention relates to an oscillation drive mechanism and more particularly to such mechanism arranged for producing optimum mold oscillation in continuous casting machines for analogous application. Specifically, the invention relates to novel means of the character described for moving a mold somewhat faster than the casting speed in the casting direction but is returned in the opposite direction at several times this speed and preferably as rapidly as practical irrespective of the forward or downward speed.

My invention is exemplarly useful with continuous casting machines such as are disclosed in the copending and coassigned application of Herbert Lemper et al. filed Mar. 6, 1967, Ser. No. 620,779". Such continuous casting machines are commonly utilized throughout the steel industry for the continuous production of slab or billet strands. A continuous casting machine may be capable of producing one or more of such strands depending upon the particular machine in question. Each of the strands usually originates at an oscillated mold structure provided with a cooling jacket.

The molten steel or other metal poured into the continuous casting mold forms a solidified outer shell adjacent the walls of the mold. Successive shell portions are stripped off by the oscillating mold structure and as the strand travels away from the mold the molten internal portion thereof progressively solidify.

In order to eliminate thickening of the casting to the mold and to avoid the application of tensil stresses to the newly formed casting, the casting desirably is subjected to negative stripping, i.e., the mold structure is moved somewhat faster forwardly or in the direction of the moving strand to strip that casting portion within the mold structure. When the mold structure is returned in the opposite direction it is desirable to move the mold structure as fast as possible in order to achieve maximum production. The return cycle of the mold oscillation, of

course, separates the stripped casting portion from the mold so that the mold structure can be refilled.

In conventional continuous casting machines, the mold structure is oscillated by means of suitable drive mechanism including a cam. The cam must be provided with a configuration to render an optimum oscillation curve at the highest anticipated casting speed. At such speeds the mold structure is desirably returned at a speed which is two to three times faster than the forward motion or negative strip of the mold structure. Unfortunately, when the continuous casting machine is slowed down as demanded by particular casting operations or conditions, the return stroke of the mold structure is correspondingly but unduly slowed, although the speed of the forward stroke is satisfactory. The time wasted during the correspondingly slower reverse strokes would provide time for a greater number of forward strokes. Hence, if it were possible to reduce the forward speed of the mold structure without at the same time reducing the return speed thereof the overall casting speed and attendant production of the continuous casting machine could be increased, in comparison to conventional practices, when slower forward rates are resorted to. Putting the matter somewhat differently, it is highly desirable to return the mold structure to its starting position as fast as possible during each oscillation irrespective of its forward speed. A realization of this desirable result would obtain an optimum mold oscillation characteristic and attendantly a maximum production rate.

This desirable result has previously been attempted -with hydraulic drives. These attempts have not been eminently successful owing to the high maintenance costs of the hydraulic drives, particularly in the high temperature environment to which they are subjected. Further, hydraulic drives introduce intolerable inaccuracies into the oscillation characteristic of the mold structure as a result of load changes and the inevitable leakage and changes in fluid viscosity of the hydraulic fluid.

I overcome these disadvantages by providing an electromechanica-l arrangement for approximating the aforementioned optimum oscillation characteristic Without encountering any of the aforementioned disadvantages associated with hydraulic drives. More specifically, I provide a drive mechanism for mold oscillation involving a plurality of camming surfaces which are appropriately contoured to produce the desired forward speed of the mold structure and to return the mold structure as rapidly as possible irrespective of the selected forward rate. I also provide novel means for supporting and shifting the camming surfaces as part of my disclosed oscillation drive mechanism. The drive mechanism can include the selflocking worm gear and helical or spur gear train, disclosed in the aforementioned copending application, for coupling the camming surfaces to suitable drive means.

I accomplish these desirable results by providing an oscillation drive mechanism including output camming means, a cam follower engageable with said camming means, means for rotatably mounting said camming means, means for rotating said cam means, said camming means having a plurality of camming surfaces positioned thereon, and means for selectively juxtaposing said camming surfaces to said cam follower.

I also desirably provide an oscillation drive mechanism wherein said camming means are mounted upon an elongated output shaft for rotation therewith, slidably engageable keying means are positioned on said shaft and on said camming means, and said camming means slidably engage said shaft and for movement therealong.

I also desirably provide an oscillation. drive mechanism wherein pivoted positioning means are mounted for movement generally parallel to said output shaft, said positioning means having an extension engaging a journal therefor on said camming means for slidably moving said camming means with pivoting movements of positioning means.

I also desirably provide an oscillation drive mechanism wherein said camming surfaces are provided with similar camming portions so that movements of said cam follower in one direction thereof are at substantially the same rate for a given speed of said mechanism irrespective of the preselected one of said camming surfaces, but said camming surfaces are provided with respectively differing camming surfaces for moving said cam follower in a generally opposite direction of movement at correspondingly differing rates at said given speed.

During the foregoing discussion, various objects, features and advantages of the invention have been set forth. These and other objects, features and advantages of the invention together with structural details thereof will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention and presently preferred methods of practicing the same.

In the accompanying drawings I have shown certain presently preferred embodiments of the invention and have illustrated certain presently preferred methods of practicing the same, wherein:

FIGURE 1 is a front elevational view of one form of mold oscillation drive mechanism arranged in accordance with my invention;

FIGURE 2 is a vertically sectioned view of the apparatus shown in FIGURE 1 and taken along reference line IIII thereof;

FIGURE 3 is a partial right side elevational view of the apparatus as shown in FIGURE 1;

FIGURE 4 is an enlarged, partial, sectional view of the apparatus as shown in FIGURE 3 and taken along reference line IV-IV thereof;

FIGURE 5 is a partial cross sectional view of the apparatus as shown in FIGURE 2 and showing one of the cam lobes thereof;

FIGURE 6 is a similar view of another of the cam lobes;

FIGURE 7 is a similar view showing another of the cam lobes;

FIGURE 8 is a graph showing the development of the camming surfaces of the aforementioned cam lobes; and

FIGURE 9 is a graph illustrating comparative rates of oscillatory movement of the mold structure corresponding to use of the aforementioned cam lobes;

FIGURE 10 is a graph illustrating optimum useage of the aforementioned cam lobes for a given application.

Referring now more particularly to the drawings and initially to FIGURES 1 and 2 thereof, an exemplary form of my novel oscillation drive mechanism 10 is shown therein. The drive mechanism 10 includes an electric motor 12 provided with tachometer 14 and coupled to worm shaft 16 through a conventional flexible coupling 18. The shaft 16 is rotatably mounted on bearings 20, 22, and Worm 24 mounted on the shaft 16 for rotation therewith engages worm gear 26 as better shown in FIGURE 2. Worm gear shaft 28 is coupled to cam shaft 30 through enmeshed left and right hand helical gears 32 and 34. Understandably, of course, spur gears (not shown) can be substituted for the helical gears 32, 34. The worm gear shaft 28 is rotatably mounted on bearing assemblies 36 and 38 which in turn are mounted on power train case 40. The cam shaft 30 is similarly mounted.

A multilobed camming member 42 is slidably mounted on the cam shaft 30 but is keyed for rotation therewith by a pair of splines 44 and 46 seated in grooves 48 extending longitudinally in the outer surface of the cam shaft 30 as better shown in FIGURE 2. The cam member 42 includes a complementary central opening and thus is free to slide along the length of the cam shaft 30 between its helical gear 34 on the one hand, and cam shaft bearing 38 on the other. Such lateral movement of the cam member 42 is controlled, however, by means described below. In this example, the cam member 42 is provided with three lobes or camming surfaces 50, 52 and 54, the individual contours of which are better shown in FIGURE 1 of the drawings. Although three of said camming lobes are illustrated, it will be readily understood that a different number can be employed depending upon the application of the invention.

A pivotally mounted cam follower 56 having follower wheel 58 rotatably mounted thereon is positioned for engagement with a selected one of the cam member lobes 50, 52 or 54. The cam follower 56 is secured to cam follower shaft 58 which in turn is rotatably mounted on front and rear extensions 60, 62 of the upper portions of the casing 40. The follower wheel 58 is rotatably mounted on depending arm 64 of the cam follower 56.

A cam follower 56 thus is oscillated vertically (as viewed in FIGURE 1) by the engagement between one of the cam member lobes and follower wheel 58 which extends through access aperture 66 in the top of the casing 40. Desirably, the casing opening 66 is sealed by bellows 68 extending from the casing 40 to the cam follower 66 as better shown in FIGURE 1.

The oscillating movements of the cam follower 56 are translated into similar but opposed movements of mold structure 70 through pivoted beam 72 and associated link members 74 and 76.

The cam member 42 is shifted along the length of the cam shaft 30 to bring a selected one of the lobes 50-54 into engagement with follower wheel 56. As shown in FIGURE 2 of the drawings, the cam member 42 is moved to a position adjacent its right hand limit of travel such that the lobe 50 is engaged by the follower wheel 56. In accordance with another feature of my invention, I provide positioning means for quickly and positively positioning the cam member 42 to bring preselected ones of the lobes 50-54 into such engagement.

With reference now more particularly to FIGURES 1-3 of the drawings, one form of such position means includes a rotatably mounted shaft 78 having one end thereof protruding from the casing 40. A shifting arm 80 and an actuating arm 82 are affixed to the shaft 78 for rotation therewith. The shifting arm 80 is positioned within the casing -40 as better shown in FIGURE 1 and is provided with rotatably mounted cam follower wheel 84 positioned to ride in journal 86 of the cam member 42 (FIGURE 2). In furtherance of this purpose the shifting arm journal wheel 8-4 is rotatably mounted on headed stub shaft 88, which in turn is rotatably mounted on lateral extension 90 of the shifting arm 80, as better shown in FIGURE 4. By this arrangement, angular displacement of the shaft 78 induces similar movement of the arm 80 and journal wheel 84 between the solid outline position of the camming member 42 in FIGURE 2 and its chain outline position 92.

The shaft 78 and shifting arm 80 can be selectively moved between these two limiting positions by movement of actuating arm 82, which is provided with operating handle 94 for this purpose as better shown in FIGURES 1 and 3. In this arrangement, actuating arm 82 is positioned by an index plate 96 having indexing apertures 98, 100, 102 as better shown in FIGURE 3. Thus, actuating arm 82 can be juxtaposed to a selected one of the index apertures 98-102 to produce corresponding movements of the shifting arms 80 as noted by its solid outline position in FIGURE 2 and chain outline positions 104, 106 of its journal wheel 84 respectively to selectively position cam member 42 at its solid outline position (FIGURE 2), its chain outline position 108 and its chain outline position 92. These movements selectively bring cam lobes 50, 52 and 5 4 respectively into engagement with the follower wheel 58.

The handle 94 is of conventional construction and includes a spring loaded plunger 110 (FIGURE 3) capable of partial entry into a selected one of indexing apertures 98, 100, 102 to retain the handle '94 and actuating arm 82 thereat.

Referring to FIGURES 1, 2, 5-9 of the drawings, exemplary camming configuration of the cam lobes 50-54 are illustrated. As better shown in FIGURE 1, it is assumed that cam member 42 is rotated in the direction of arrow 134 to produce oscillatory movements of the mold structure 70 as noted by arrows 136 and 138. Thus, each of the cam lobes 50-54 is provided with configurations 140, 141, 142 (FIGURES 5-7) respectively whose first differentials are substantially linear (FIGURE '8) and which produce corresponding upward movements of cam follower 56 and downward movements of the mold structure 70 at substantially constant velocities 143, 144, 145 respectively (FIGURE *9) as denoted by arrow 136. Accordingly, the mold structure 70 is moved downwardly twice (FIGURES 5-9) during each revolution of the cam member 42. With this arrangement then the downward or forward cycles of the mold structure oscillations will be at substantially constant but differing and progressively slower velocities for a given speed of the oscillation drive mechanism depending upon that one of the lobes 50-54 which is engaged with the cam follower 56, owing to the first differential line of the rise camming portions 140-142 of all of the cam member lobes 50-54; Constant velocities in the forward direction of the mold structure are highly desirable for efiicient negative stripping.

On the other hand, the dwell configurations 146, 147, 148 (FIGURES 5-7) of cam lobes 50, 52, 54 respectively are of progressively lesser angular segments (cf. FIGURE 8) of their related cam lobes 50-54. (In this connotation the term rise and dwell refer to the corresponding directional movements of cam follower 56.) The dwell configurations 146-148 permit the cam follower 56 when selectively engaged with the camming lobes 50-54 to descend with suitable acceleration and deceleration as indicated by the cam development curves 146, 147, 148 of FIGURE 8 and by corresponding rate curves 149, 150, 151 of FIGURE 9, which as noted previously are the first differentials of the cam development curves of FIGURE 8. Thus the acceleration- deceleration curves 149, 150, 151 of FIGURE 9 denote average rates in this example of two, three, and five times that of the corresponding ascending rate curves 143, 144, 145. The mold structure 70, during its return stroke is moved first at an accelerating rate 149a, 15011, or 151a (FIGURE 9) followed by a decelerating rate 1491;, 150b, 1511;. These acceleration and deceleration rates are adjusted as denoted by the dwell development curves 146, 147, 148 of FIGURE 8 such that the integrated areas under the return rate curves 149-151 of FIGURE 9 are equal to /2, A and /5 the integrated areas under forward velocity curves 143-145 respectively. This establishes the necessary average rates of the mold structure 70 during its return strokes to re turn the mold structure within time intervals equal to /z, /3 and /5 of the forward stroke time intervals when the cam follower 56 is selectively engaged with cam lobes 50, 52, 54 respectively.

From the exemplary configurations of the several cam lobes 50-54 as shown, it will be seen that the cam lobe 50 in this example is provided with a rise time to dwell time ratio of 2:1 producing a corresponding average reverse speed of the mold structure equal to twice its forward velocity. Cam lobe 52 affords a similar speed ratio of 3:1 and cam lobe 54, 5:1. These typical ratios can readily be varied to meet production ranges in specific applications of my invention. Thus, one or more of the aforementioned speed ratios can be changed by varying the rise and dwell configurations of one or more of the cam lobes 50-54 in accord with the principles of the invention inherent in FIGURES 8 and 9.

With the arrangement shown, the mold structure 70 can be returned at a maximum speed during its reverse stroke although its forward stroke is slowed considerably by decreasing the speed. of the oscillation drive mechanism 10 in accordance with production conditions. Ac-

cordingly, loss of production is not entailed by slow return strokes of the mold structure 70 although certain casting conditions require slowing down the forward strokes of the mold structure 70.

A typical useage of my oscillation drive mechanism 10 is illustrated in FIGURE 10 of the drawings, wherein oscillations per minute of the mold structure is plotted against casting speed in inches per minute. The variously shaded areas 152, 154, 156 correspond respectively to useage of cam lobes 50, 52, 54 of the oscillation drive mechanism 10. Emperical curves 158, 160 denote the optimum times for shifting the cam member 42, in this application, from the cam lobe 50 to the cam lobe 52 and from the cam lobe 52 to the cam lobe 54 respectively depending upon production conditions. The families of curves shown in each shaded area 152, 154, or 156 correspond to indicated oscillational amplitudes, in this example of /2 inch to 1 /2 inches respectively, or inch to 1 /2 inches for the shaded area 152, resulting from use of a selected one of cam follower apertures 158, 160, 162, 164, 166 respectively (FIGURE 1).

Of course, it will be understood that different amplitudes of mold structure oscillation can be selected depending upon the application of the invention.

FIGURE 10 illustrates the manner in which one of the cam lobes 50-54 can be selected to produce an optimum production rate at differing speeds and other production variables affecting the operation of the continuous casting machine. For example, the cam lobe 50' desirably is employed, as denoted by the shaded area 152, when the casting machine is operated at maximum casting speeds to produce a product of relatively small cross section. At this time the drive mechanism 10 is operated to produce maximum or near-maximum number of oscillations per minute.

When a product of medium cross section area or configuration is being cast, the drive mechanism 10 is operated at medium speed in accordance: with the reduced casting speed. At this time, employment of the cam lobe 52 provides a correspondingly more rapid return stroke of the mold structure 70 in comparison to the necessarily slowed forward stroke to produce a correspondingly increased production of the medium sized casting as denoted by the shaded curve section 154 (FIG- URES 8 and 10). If the cam lobe 50 be employed instead, the return strokes of the mold structure 70 would become undesirably slowed with reduction in casting speed.

In much the same manner cam lobe 54 is employed for relatively large casting speeds in conformance with shaded graph section 156. As seen from FIGURE 8 the return strokes of the mold structures 70 arestill more rapid in comparison to its slower forward strokes to compensate for the still slower operation of the drive mechanism 10 and the speed of the casting machine.

From the foregoing it will be apparent that novel and efiicient forms of oscillation drive mechanism have been described herein. While I have shown and described certain presently preferred embodiments of the invention and have illustrated presently preferred methods of practicing the same it is to be distinctly understood that the invention is not limited thereto but may be variously embodied and practiced within the scope of the following claims.

I claim:

1.- An oscillation drive mechanism including output camming mean, a cam follower engageable with said camming means, means for rotatably mounting said camming means, means for rotating said camming means, said camming means having a plurality of camming surfaces positioned thereon, means for selectively juxtaposing said camming surfaces to said cam follower, said camming means being mounted upon an elongated output shaft for rotation therewith, slidably engageable keying means positioned on said shaft and on said camming means, said camming means slidably engaging said shaft and said keying means for movement therealong, pivoted positioning means mounted for movement generally parallel to said output shaft, said positioning means having an extension engaging a journal therefor on said camming means for slidably moving said camming means upon pivotal movements of said positioning means, means for indexing said positioning means at positions thereof corresponding to the juxtaposition of said camming surfaces to said cam follower respectively, said indexing means including an apertured plate mounted on a casing for said mechanism and a spring loaded plunger mounted on said positioning means and shaped for partial insertion into said plate apertures.

2. An oscillation drive mechanism including output camming means, a cam follower engageable with said camming means, means for rotatably mounting said camming means, means for rotating said camming means, said camming means having a plurality of camming surfaces positioned thereon, means for selectively juxtaposing said camming surfaces to said cam follower, each of said camming surfaces having a constant velocity camming portion and an accelerational camming portion, said velocity portions being of similar character and said accelerational portions being of respectively differing character so that movements of said cam follower in one direction thereof by said velocity portions are at substantially the same constant velocity for a given speed of said mechanism irrespective of the preselected one of said camming surfaces but movements of said cam follower in the opposite direction thereof under control of said accelerational portions occur at correspondingly differing accelerational rates at said given speed.

3. The combination according to claim 2 wherein each of said camming surfaces includes a pair of constant velocity portions and a pair of accelerational portions arranged in an alternating array.

4. The combination according to claim 2 wherein each of said accelerational portions induces similar acceleration and decelerational movements of said cam follower in said opposite direction at each of said correspondingly differing rates.

5. The combination according to claim 2 wherein each of said velocity portions includes similar accelerational and decelerational sections adjacent the beginning and ending thereof respectively.

6. In a continuous casting machine, the combination comprising a mold structure mounted for oscillatory movement, an oscillational lever, an oscillational drivin-g mechanism having a support, a cam follower pivotally mounted on said support, means for pivotally mounting said oscillational lever and for connecting said lever to said cam follower and to said mold structure, said driving mechanism including camming means and means for rotata-bly mounting and driving said camming means, said camming means having a plurality of camming surfaces formed thereon, said camming means being slidably and keyingly mounted upon a shaft forming part of said driving means for rotation with said shaft, and means for slidably moving said camming means along said shaft for engaging a selected one of said camming surfaces with said cam follower to impart a correspondingly oscillatory character to the movements of said mold structure.

7. The combination according to claim 6 wherein said joining means for said lever and said cam follower include a pivoted link and a plurality of pivot connections for said link formed on said cam follower for imparting correspondingly differing amplitudes of movement of said lever and said mold structure for each of said camming surfaces.

8. The combination according to claim 6 wherein each of said camming surfaces includes a constant velocity portion for moving said mold structure at a constant rate in a forward direction at a given speed of said driving means, and said camming surfaces further include a respectively dilfering accelerational camming portion so that said camming surfaces return said mold structure at correspondingly differing speeds.

References Cited UNITED STATES PATENTS 678,409 7/1901 Lengweiler 74-54 1,720,189 7/1929 Jackson 74-568 2,295,041 9/1942 Iunghans 16483 3,258,815 7/1966 Reinfeld 16426O FRED C. MATTERN, JR., Primary Examiner.

W. S. RATLIFF, JR., Assistant Examiner.

U.S. Cl. X.R. 745 68

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