US3630269A

US3630269A - Continuous casting cutoff apparatus

Info

Publication number: US3630269A
Application number: US805761A
Authority: US
Inventors: Hans Bieri
Original assignee: ERIK OLSSON AG
Current assignee: ERIK OLSSON AG
Priority date: 1968-03-11
Filing date: 1969-03-10
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: DE1912084A1; CS153501B2; CH466895A; JPS4924509B1; SE348127B

Abstract

There is disclosed an apparatus for severing a continuously formed casting into sections. It comprises a carriage having a cutting torch movable transversely across the casting while it travels with the casting. The carriage travels along a guideway in the direction of the length of the casting, and it has two sets of clamps, one set being operable to engage the casting at one side of the cut, and the other being operable to engage the severed section. Provision is made to maintain the carriage centered in the guideway, but to permit controlled lateral movement where an irregularity in the casting requires it. For a vertical cutoff carriage, provision is made to transfer the severed section to a vertical frame which swings upwardly to a horizontal position for discharge of the severed piece.

Description

United States Patent 72 Inventor Hans Bieri 3,107,404 10/1963 Armand et a1. 164/282 x Oberrick, Switzerland 3,237,251 3/1966 Thalmann 164/282 X pp 805,761 FOREIGN PATENTS g' 3 131 895,913 5/1962 Great Britain 164/282 [73] A ignee Erik 01; AG Primary Examiner-J. Spencer Overholser Zurich, Switzerland Assistant Examiner lohn E. Roethel [32] Priority Mar. 1 1, 1968 Attorney-Parmelee, Utzler & Welsh [33] Switzerland [31] 3578/68 ABSTRACT: There is disclosed an apparatus for severing a continuously formed casting into sections. It comprises a car- 54 CONTINUOUS CASTING CUTOFF APPARATUS riage having a cutting torch movable transversely across the 12 C|aims,4 Drawing Figs casting while it travels with the casting. The carriage travels along a guideway in the direction of the length of the casting, [52] 11.5. CI 164/263, and it has two Sets of clamps one Set being operable to engage 1644282366, M the casting at one side of the cut, and the other being operable Int. to g g the Severed section. provision is made to maintain L. of Search l he carriage centered in the g y, but to permit 266/23 M trolled lateral movement where an irregularity in the casting [56] References Cited requires it. For a vertical cutoff carriage, provision is made to transfer the severed section to a vertical frame which swings UNITED STATES PATENTS upwardly to a horizontal osition for dischar e of the severed P 8 2,582,329 l/l952 Harter et al 164/282 X i 2,806,263 9/1957 Hogan 164/263 PATENTEU UEC28 1971 SHEET 1 OF 2 L WW INVENTOR Hans BLeri.

Attorneys.

PATENTEnnaczalsn 3,630,269

sum 2 OF 2 i 4 IO F 'i B. P '1 '5.

INVENTOR. Hans Bieri.

Attorneys.

CONTINUOUS CASTING CUTOFF APPARATUS This invention relates to the art of continuous casting and is for an improved mechanism for severing the casting into individual sections and guiding the severed sections.

It has heretofore been the practice with both vertical continuous casting apparatus and in continuous casting apparatus where the casting is curved from a vertical to a horizontal direction of travel, to provide a carriage which moves along with the casting, and which has a torch or other cutofl means to sever a length from the leading end of the casting, after which the carriage returns to a starting position to make the next cut. A difficulty with such devices arises from the fact that control of the section which is removed is terminated so that its travel is not properly timed with respect to a previously cut section and it may not be properly guided. This disadvantage becomes greater as the cut pieces become shorter.

According to the present invention there is provided a carriage with means for moving it in either direction lengthwise of the casting, and through which the casting passes from an entering end to an exit end of the carriage. A cutting torch is arranged intermediate the ends of the casting, and there is a clamping means on the carriage intermediate its ends. There is one casting clamping means on the carriage between the cutting torch and the entering end of the carriage, and another between the torch and the exit end of the carriage. These clamping means can operate independently so that the carriage may first be clamped to the emerging casting with both clamping means, and the carriage then travels with the casting, and after a cut is made, the first clamping means is released while the severed piece remains clamped to the carriage. The speed of the carriage may then be increased by operating it with the carriage driving means to deliver the severed piece onto a receiving table or conveyor of some kind, after which the second clamping means is released from the severed piece and the carriage, after which the carriage is then returned to the starting position in time to repeat the operation. In this way the timing of the release of the severed section can be lengthened with respect to the time when the actual cutting takes place to assure proper spacing of the cut sections as well as the guiding of the cut section being controlled between the time it is severed and the time when it is released.

The invention provides spaced guide rails along which the carriage moves with rollers at each side of the carriage that are maintained in contact with the rails by oppositely acting biasing means, such as fluid pressure cylinders which normally keep the carriage centered with respect to the casting, but which will yieldably permit controlled sidewise movement when some condition in the casting requires it.

The invention further provides a transfer device of novel construction for use where the vertically moving casting is cut into sections, with clamping means for holding the severed section after it has been released from the clamping means on the carriage and raising the severed section to a horizontal position where it may be discharged from the transfer device.

In the drawings, illustrating somewhat diagrammatically a preferred embodiment of the invention for use with a vertically moving casting:

FIG. I is a generally schematic view of the cutoff and transfer apparatus;

FIG. 2 is a transverse section in the plane of line II-II of FIG. 1 with the carriage in the dotted line position of FIG. 1, certain parts being omitted for clarity of illustration;

FIG. 3 is a side elevation of the carriage with the cutting torch omitted; and

FIG. 4 is a horizontal section on a larger scale in the plane of line IVIV of FIG. 3, the suction box being also omitted, the view showing diagrammatically the fluid pressure system.

In the drawings, 2 designates a location, such as a pit, under a continuous casting apparatus (not shown) which is located high enough above the top of the pit for the continuously descending casting 3 to be sufliciently solidified to be cut into sections before ti reaches the top of the pit. All of this is well understood in the art.

According to the present invention there are two vertical channels 4 confronting each other in the plane of the descending casting. They are supported on a fixed part 5 of the casting plant structure and extend down along each side of the casting from the top support to approximately the level aa in FIG. I These channels are only indicated in broken lines in FIG. I in order not to confuse other parts of the drawing, but their location is clearly seen in FIG. 2.

There is a carriage designated generally as 6 movable up and down in the vertical guideway provided by these channels. This carriage comprises a frame which is generally rectangular in elevation as seen in FIG. 3, and rectangular when viewed from the top, as seenin FIG. 2. There is a central opening or passage 7 extending vertically through the frame through I which the casting 3 may pass with clearance between the casting and frame all the way around the casting. The top of the carriage is the entering end, and the bottom the exit end. The opposed long sides of the rectangular boxlike frame are designated 8 and 9, and as most clearly seen in FIG. 4, the frame is fabricated from plate metal with spaced inner and outer walls. The opposite end walls of the carriage frame are designated 10 and 11.

As seen in FIGS. 1 and 3, the surface of the long side 8 of this frame has a slot 12 thereacross with outwardly diverging top and bottom walls. A cutting torch, schematically indicated at 13 in FIG. 1, is supported for movement crosswise of the face of the casting 3 for severing the portion of the casting below the torch from the part above it. Cutting off torches for this purpose are known in the art and form no part per se of the invention.

On each wide face of the carriage above the level of the slot 12 are cooperating clamping means. As best seen in FIG. 2 this clamping means comprises a pair of spaced cylinders 14 on one face 8 above the slot 12 with pistons 15 having castingengaging pads or feet 16 and an exactly similar cylinder 14 with piston 15 and pads 16 directly opposite the first ones on the upper part of the opposite face 9 of the frame.

Similarly arranged on the

wide faces

8 and 9 of the carriage frame below the level of the slot 12 are similar clamping means comprising cylinder and piston units 17 with pistons similarly arranged with clamping pads or feet. The upper clamping cylinders are spaced so that the casting is engaged at approximately equal distances each of the center, and the lower clamping cylinders are directly under the upper ones.

Each narrow end wall or panel 10 and 11 of the carriage has upper and lower cylinders 20 thereon, each with a piston 21. Rotatable about the axis of each piston 21 is a guide roller 22, and these roll in the guide channels 4. Also each piston 21 has at its outer end a small thrust roller 23 and these bear against the webs of the respective channels 4 in which they are engaged to provide a low friction end thrust for guiding the carriage between the rails.

The fluid pressure circuit for the upper clamping cylinders 14 is indicated in FIG. 4, as is also the fluid pressure system for the end cylinders 20. The fluid pressure system for the lower cylinders 17 is not shown, but is identical with, but separate from the system for clamping cylinders 14. For the cylinders 14 there is a fluid pressure supply line 25 with a three-way valve 26 from which leads a pipe 27 having a branch 28 leading to the end of each cylinder 14. A second pressure line 29 has branches 30 leading to the opposite ends of the cylinders 14 back of the piston. When the casting is to be clamped, pressure is admitted through valve 26 to the cylinders 14 to drive the pistons to the clamping position shown in FIG. 4 against the constant pressure on the opposite but smaller area of the pistons exerted by pressure in line 29. When the clamps are to be released, the valve 26 is turned to shut off the flow of fluid from supply line 25 and exhaust it from pipe 27 and the cylinders 14, so that the pressure in line 29 will instantly effect a retracting movement of the pistons 15.

The end cylinders 20 are under constant pressure by fluid in line 31 with branches 32 to the cylinders 20. If the carriage, under the influence of the casting, tends to drift to the left, for

example, there is a flow of fluid from the left cylinder 20 to the right, yieldably permitting slight sidewise movement without stressing the carriage frame. Ordinarily, however, equal pressures in the two cylinders 20 tend to centralize the carriage in the guideway provided by the two channels.

The side face 9 of the panel has a pair of lugs 40 projecting therefrom, between which is a flattened terminal at the top of a vertical cylinder 41 having a piston 42 that is pivotally anchored at 43 to the foundation under the machine, the cylinder and piston comprising a hydraulic jack. With this arrangement the cylinder may travel vertically while the piston remains stationary. Vertical movement of the cylinder 41 is transmitted to the carriage to move it vertically in the guide rails 4.

For receiving the cutoff section of the casting there is a roller table designated generally as 50, at least some rollers of which are power driven. This roller table is carried between two widely spaced arms 51 which are fixed on a rock shaft 52 supported in the frame structure, the support not being shown, but the arrangement is such that when the rock shaft 52 is rotated by mechanism (not shown), the arms 51 with the table 50 can be moved from the vertical position to the horizontal dotted line position in FIG. 1 so that the section which has been cut off can be lifted to a horizontal plane and run off onto a receiving conveyor (not shown).

The roller table 50, when it is in the vertical position, is so located with respect to the descending casting that the descending casting will bear against the rollers on the roller table. In other words, the roller table is properly aligned to receive the casting as it descends. The arms and roller table have a structure 53 in which are carried opposed pairs of clamping cylinders 54 which are in all respects similar to the cylinders 14 with their pistons 15 and pads 16, and these cylinder and piston units are positioned near the top of the roller table and below the ends of the guides which terminate at approximately line a-a. When the pistons of the clamping elements 54 are retracted, the cut section of the casting can move freely between them down the outer surface of the roller table, but when the pistons are extended to clamping position, they grip and hold the casting immovably on the roller table.

In the operation of the cutoff unit, it may be assumed that the carriage 6 is in the elevated position shown in full lines in FIG. 1, and that the cylinder 41 is raised to its full limit of travel. The casting 3 moves down through the passage 7 in the carriage, and when it reaches a level where a cut is to be made, the

cylinders

14 and 17 are both energized to grip the casting, and at this time the pressure is reduced in the cylinder 41 so that the carriage will move down with the descending casting, and as it moves down, the torch severs the casting. The upper clamping means comprising the cylinders 14 and their pistons are then released, and the lowering of the cylinder 41 is accelerated so that the carriage and the severed section move more rapidly than the descending casting, developing a space between the severed end of the casting and the section which has been cut ofi'. Depending on the length of the casting, the

descent of the carriage is carried down to the dotted line position shown in FIG. 1 when the severed section of the casting will be over the roller table. The clamping cylinders 54 will be operated at the same time the clamping cylinder 17 on the carriage will be released. As soon as the carriage has been released from the severed section, it is moved back to the fullline position by the cylinder and piston 41-42 for a repetition of the operation, while the arms 51 are swung to raise the table to a horizontal position shown in dotted lines in FIG. 1, and the severed piece is removed, after which the arms 51 and the roller table are swung back to the vertical position to receive the next section of the casting which is cut off.

With this arrangement therefore, the movement of the severed end is controlled and guided by the carriage during the full length of travel of the carriage, and at a controlled rate relative to the rate of descent of the casting 3, so that even when the descending casting is cut into relatively short lengths, their delivery tov the conveyor table and removal from the table can be sequenced to maintain spaced removal of the pieces. A controlled timing is secured by reason of the fact that the cutoff can be made much higher up on the descending casting than would be the case where the casting can drop freely after the cut is made, or where it is freely carried away on a roller table. In other words, the cut can be started as indicated in FIG. 1 while the carriage is practically at its highest limit of movement, and completed before the carriage has descended very far, but the severed section is still held in the carriage to move down at a controlled rate, and not drop by gravity onto the receiving table.

The carriage can be used in a similar manner where the movement of travel of the carriage is horizontal, as in a casting plant where the continuously cast ingot leaving the mold is curved from a vertical direction of travel to a horizontal direction of travel.

In FIG. 1 l have shown a box 60 attached to the wide wall 9 of the carriage, and there is a telescoping duct 61 opening into this box. The end of the duct 61 remote from the box is pivotally supported at 62 and is connected to a vacuum pump (not shown). Passages are provided so that fumes from the cutting torch may be sucked through the panel 9 of the carriage into the box 60 and drawn off through the telescoping duct 61. This telescoping duct can swing and shorten and lengthen, as necessary, to accommodate the vertical travel of the carriage.

Iclaim:

1. For use in a continuous casting plant wherein a casting is continuously discharged from an elevated mold, the invention comprising a cutoff apparatus having a. a guideway along the path of travel of the casting,

b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting which extends therethrough,

c. a first releasable clamping means arranged to clamp the casting between the cutoff means and the entering end of the carriage,

d. a second clamping means on the carriage arranged to releasably clamp the carriage to the casting between the cutoff means and the exit end of the carriage,

c. said first and second clamping means being independently operable to clamp or release the casting, whereby the carriage must travel at the same speed as the casting when both clamping means are clamped to the casting and the leading end of the casting has not been severed, but after the leading end has been severed and the first clamp released, the carriage and the then severed lead end can move at a faster speed than the succeeding portion of the casting and while controlling its direction and speed of travel, and

f. variable speed means for reciprocating the carriage in the direction in which the casting is moving and then returning it after both clamping means are released in the opposite direction to a starting position.

2. Cutoff apparatus for use in a continuous casting plant comprising:

a. a. guideway positioned along the path of travel of the continuous casting, said guideway comprising a rail at each side of and spaced from the sides of a casting moving down said path,

b. a single carriage positioned between said rails and movably guided thereon, said carriage having means thereon on the two opposed sides which confront said rails arranged to guide the carriage on the rails and yieldingly exert pressure against the rails in a direction parallel with the vertical plane common to both rails for centering the carriage between the rails,

c. a first releasable clamping means on the carriage arranged to clamp the carriage to the casting between the cutoff means and the entering end of the carriage,

d. a second clamping means on the carriage arranged to releaseably clamp the carriage to the casting between the cutoff means and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, and

e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then opposite thereto.

3. Cutoff apparatus for use in a continuous casting plant as defined in claim 2 in which the first and second clamping means on the carriage are arranged to exert equal and opposite pressure against the casting in a direction at right angles to the plane common to both rails.

4. Cutoff apparatus as defined in claim 2 in which said means for moving the carriage comprises a fluid pressure jack having a piston and cylinder.

5. Cutoff apparatus for use in continuous casting plant as defined in claim 3 in which the guide rails are channels in com fronting relation to each other and said means to yieldingly exert pressure against the rails comprises fluid pressure cylinders and piston units at the top and bottom of the carriage each with a roller engaged in one of the channels and urged thereagainst by its fluid pressure unit.

6. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting,

b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting passing through it,

a first clamping means on the carriage positioned to clamp the casting between the cutoff and the entering end of the carriage,

d. a second clamping means on the carriage positioned to releasably clamp the casting between the cutoff and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, and

e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then a direction opposite thereto,

f. said carriage comprising a structural frame with a central passage through which the casting passes, the frame having a slotlike opening across one face thereof transverse to the central passage, the cutoff means comprising a cutting torch positioned on the carriage to project a cutting flame through the slotlike opening to sever the casting.

7. Cutoff apparatus as defined in claim 6 wherein a vacuum exhaust arrangement is carried on the face of the boxlike frame opposite the slot to provide a vacuum exhaust for fumes from the cutoff operation, and a telescoping suction pipe connected to said exhaust arrangement.

8. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting,

c. a first clamping means on the carriage positioned to clamp the casting between the cutoff and the entering end of the carriage,

d. a second clamping means on the carriage positioned to releasably clamp the casting between the cutoff and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting,

e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then in a direction opposite thereto,

f. said cutoff apparatus being arranged for use with a casting plant wherein the casting descends vertically and the carriage moves vertically up and down through a limited ran e, and D g. a ta le below the lowermost limit of movement of the carriage positioned to receive a severed section of the casting, said table being arranged to move from a vertical position in which it receives the section which has been cutoff as such section is lowered into it by the carriage, and then upon release of said severed section by the clamping means on the carriage, lift it through an arc to a horizontal position at a level above the lowermost limit of travel of said carriage.

9. Cutoff apparatus as defined in claim 8 in which the table has clamping means thereon near its ingot-receiving end arranged to releaseably retain the severed section in position thereon.

l0. Cutoff apparatus as defined in claim 8 in which the table is a roller table with power-driven rolls.

1 l. Cutoff apparatus as defined in claim 8 in which the table is suspended from spaced arms pivotally supported at a level near but below the upper limit of travel of the carriage so that the table swings through an are between its vertical and horizontal positions, the radius of which exceeds the length of the table but the carriage can be moved to a level to clear said arms when the table moves between said two positions.

l2. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting,

e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then a direction opposite thereto, and

f. said cutoff apparatus being arranged for use with a casting plant wherein the casting descends vertically and the carriage moves up and down through a limited range, and said guideway comprises a vertical guide rail along each of two opposite sides of the carriage with means on the carriage engaging said guide rails arranged to exert pressure in opposite directions against the said rails to yieldably center the carriage between the rails, said clamping means on the carriage being arranged to exert equal and opposite pressure against two opposite faces of the continuous casting in a direction at right angles to the vertical plane common to the two guides and thereby center the casting in the carriage when the clamps engage the casting.

Claims

1. For use in a continuous casting plant wherein a casting is continuously discharged from an elevated mold, the invEntion comprising a cutoff apparatus having a. a guideway along the path of travel of the casting, b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting which extends therethrough, c. a first releasable clamping means arranged to clamp the casting between the cutoff means and the entering end of the carriage, d. a second clamping means on the carriage arranged to releasably clamp the carriage to the casting between the cutoff means and the exit end of the carriage, e. said first and second clamping means being independently operable to clamp or release the casting, whereby the carriage must travel at the same speed as the casting when both clamping means are clamped to the casting and the leading end of the casting has not been severed, but after the leading end has been severed and the first clamp released, the carriage and the then severed lead end can move at a faster speed than the succeeding portion of the casting and while controlling its direction and speed of travel, and f. variable speed means for reciprocating the carriage in the direction in which the casting is moving and then returning it after both clamping means are released in the opposite direction to a starting position.

2. Cutoff apparatus for use in a continuous casting plant comprising: a. a. guideway positioned along the path of travel of the continuous casting, said guideway comprising a rail at each side of and spaced from the sides of a casting moving down said path, b. a single carriage positioned between said rails and movably guided thereon, said carriage having means thereon on the two opposed sides which confront said rails arranged to guide the carriage on the rails and yieldingly exert pressure against the rails in a direction parallel with the vertical plane common to both rails for centering the carriage between the rails, c. a first releasable clamping means on the carriage arranged to clamp the carriage to the casting between the cutoff means and the entering end of the carriage, d. a second clamping means on the carriage arranged to releaseably clamp the carriage to the casting between the cutoff means and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, and e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then opposite thereto.

5. Cutoff apparatus for use in continuous casting plant as defined in claim 3 in which the guide rails are channels in confronting relation to each other and said means to yieldingly exert pressure against the rails comprises fluid pressure cylinders and piston units at the top and bottom of the carriage, each with a roller engaged in one of the channels and urged thereagainst by its fluid pressure unit.

6. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting, b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting passing through it, c. a first clamping means on the carriage positioned to clamp the casting between the cutoff and the entering end of the carriage, d. a second clamping means on the carriage positioned to releasably clamp the casting between the cutoff aNd the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, and e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then a direction opposite thereto, f. said carriage comprising a structural frame with a central passage through which the casting passes, the frame having a slotlike opening across one face thereof transverse to the central passage, the cutoff means comprising a cutting torch positioned on the carriage to project a cutting flame through the slotlike opening to sever the casting.

8. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting, b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting passing through it, c. a first clamping means on the carriage positioned to clamp the casting between the cutoff and the entering end of the carriage, d. a second clamping means on the carriage positioned to releasably clamp the casting between the cutoff and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, e. means for reciprocating the carriage lengthwise of the casting alternately in the direction in which the casting is moving and then in a direction opposite thereto, f. said cutoff apparatus being arranged for use with a casting plant wherein the casting descends vertically and the carriage moves vertically up and down through a limited range, and g. a table below the lowermost limit of movement of the carriage positioned to receive a severed section of the casting, said table being arranged to move from a vertical position in which it receives the section which has been cutoff as such section is lowered into it by the carriage, and then upon release of said severed section by the clamping means on the carriage, lift it through an arc to a horizontal position at a level above the lowermost limit of travel of said carriage.

10. Cutoff apparatus as defined in claim 8 in which the table is a roller table with power-driven rolls.

11. Cutoff apparatus as defined in claim 8 in which the table is suspended from spaced arms pivotally supported at a level near but below the upper limit of travel of the carriage so that the table swings through an arc between its vertical and horizontal positions, the radius of which exceeds the length of the table but the carriage can be moved to a level to clear said arms when the table moves between said two positions.

12. Cutoff apparatus for use in a continuous casting plant comprising a. a guideway along the path of travel of the casting, b. a single carriage movable along the guideway through which the casting passes from an entering end to an exit end with means intermediate the ends of the carriage for severing the casting passing through it, c. a first clamping means on the carriage positioned to clamp the casting between the cutoff and the entering end of the carriage, d. a second clamping means on the carriage positioned to releasably clamp the casting between the cutoff and the exit end of the carriage, said first and second clamping means being independently operable to clamp and release the casting, e. means for reciprocating the carriage lengthwise of the Casting alternately in the direction in which the casting is moving and then a direction opposite thereto, and f. said cutoff apparatus being arranged for use with a casting plant wherein the casting descends vertically and the carriage moves up and down through a limited range, and said guideway comprises a vertical guide rail along each of two opposite sides of the carriage with means on the carriage engaging said guide rails arranged to exert pressure in opposite directions against the said rails to yieldably center the carriage between the rails, said clamping means on the carriage being arranged to exert equal and opposite pressure against two opposite faces of the continuous casting in a direction at right angles to the vertical plane common to the two guides and thereby center the casting in the carriage when the clamps engage the casting.