CA1217665A

CA1217665A - Apparatus for supporting the mandrel back-up bar of an axial piercing machine for hotworking billets, ingots and the like

Info

Publication number: CA1217665A
Application number: CA000429508A
Authority: CA
Inventors: Carlo Rigamonti; Emanuele Gancia
Original assignee: Innse Innocenti Santeustacchio SpA
Current assignee: SMS Group SpA
Priority date: 1982-06-03
Filing date: 1983-06-02
Publication date: 1987-02-10
Also published as: GB8314725D0; IT8221675A0; GB2121338B; FR2527948A1; DE3319809A1; FR2527948B1; JPS58218310A; GB2121338A; IT1151443B; IT8221675A1

Abstract

ABSTRACT
Apparatus is described for increasing the rigidity and providing centering support for a mandrel back-up bar on the rolling and piercing axis of a press-piercing rolling mill, the apparatus comprising a plurality of substantially cradle-like structures aligned along the piercing axis and each supporting a trio of rollers which are angularly displaceable towards and away from the axis with substantially self-centering movements.
Each trio of rollers forms a substantially rigid rink around the mandrel back-up bar but provides a basically bezel-type support for the pierced intermediate blank as it is advanced along the bar.

Description

The present invention relaxes to apparatus for supporting the mandrel back-up bar of an axial piercing machine for hot working billets, ingots and the like. More particularly the invention concerns apparatus for increasing the rigidity and pro-voiding centering support for the mandrel back-up bar on the piercing axis of a press-piercing rolling mill.
A press piercing mill is a machine which can convert a square billet into an axially pierced, round, intermediate blank. This machine comprises a rolling stand with two driven rolls defining a circular gorge, a piercing mandrel carried at one end of an associated bar extending along the rolling and piercing axis from the exit side of the stand and a pusher for thrusting a square billet between the rolls and against the piercing mandrel.
In order to effect hot axial piercing of a billet ingot, bar, or the like, with as small a degree of eccentricity as possible, it is necessary for the mandrel back-up bar of a press-piercing mill to be firmly held on the piercing axis so as to provide a considerable degree of rigidity. This requirement is particularly necessary at the beginning of the piercing operation, and, particularly, when the ratio between the length and the diameter of the piercing to be made is of the order of 25 or more.
Up till now the mandrel back-up bar has been supported and retained on the piercing axis by a plurality of pairs of constraining elements supported by a suitable bed and located in two parallel lines which are symmetrical relative to the piercing axis. Each constraining element is basically constituted by a vertical-axis roller supported at one end of an arm, the other end of which is rotatable mounted on a vertical pin carried by a slide. An hydraulic cylinder, or similar actuator, provides for the angular displacement of the arm about the corresponding vertical pin to position the roller in contact with the mandrel back-up bar or to space it therefrom The slide mentioned above is movable on horizontal guides perpendicular to the piercing axis and its position is adjustable on the guides. In this manner, the vertical rollers of each pair of constraining elements may be located at different distances from the piercing axis to suit mandrel back-up bars of different transverse dimensions.
This method of supporting the mandrel back-up bar, although widely used, has the disadvantage of not giving the bar itself sufficient rigidity to withstand all the considerable forces mandrel loads) exerted thereon during operation of the press-piercing mill. Indeed, in accordance with the said method, the mandrel back-up bar is supported and retained in correspondence with two diametrally opposite generatrices by pairs of vertical rollers while it is completely free above and below. The known method thus achieves a substantially pincer lice grip on the mandrel back-up bar.
Moreover, as piercing proceeds, the load situation on the mandrel back-up bar gradually worsens. Indeed, while, on the one hand, the number of constraints which hold the mandrel back-up bar diminishes since successive pairs of constraining elements are opened to allow the passage of the pierced blank, on the other hand, a gradually increasing lateral load is added to the manure].

load due to the weight of the blink itself. The forces on the mandrel back-up bar may thus make it bend, starting a stress-deformation situation which is highly undesirable since it may increase the degree of eccentricity of the resulting piercing to unacceptable levels.
In addition, the inevitable existence in each con-straining element, of play in the couplings button the Swede and the corresponding guide, in the pivot couplings of the roller-carrying arm to the corresponding slide and to the hydraulic actuator, results in inexact positioning of the constraining element itself relative to the piercing axis, and, hence, increases the eccentricity of the mandrel back-up bar relative to the axis to a greater or lesser extent.
The problem which is solved by this invention is the provision of apparatus for supporting the mandrel back-up bar in a central position on the rolling and piercing axis of a press-piercing rolling mill, which has structural and functional characteristics such as to ensure correct and efficient rigidifying constraint of the bar itself, as well as supporting it in exact alignment with the piercing axis, even during the progressive advance of the pierced blank thrilling.
This problem is resolved, according to the invention, by apparatus for increasing the rigidity and for providing center-in support for a mandrel back-up bar on the piercing axis of a press-piercing rolling mill. The apparatus comprising three levers pivoted on respective horizontal pins parallel to the piercing axis, intersections of the axes of the pins with a I

vertical plane perpendicular to-the piercing axis, being disposed at the vertices of an equilateral triangle, the sauntered of which is the intersection of the piercing axis with the vertical plane, three rollers each mounted for free rotation a-t the end owe a respective lever and at the same distance from the corresponding pins, the axes of rotation of the rollers lying in a common vertical plane, perpendicular to the piercing axis and each intersecting in the same plane the axis of the corresponding pin, and drive members for angularly displacing the levers and their respective rollers about the pins towards and away from the piercing axis with substantially self-centering type movements, two of the rollers being contemporaneously moved towards the piercing axis along respective ascending paths, the third roller being moved towards the piercing axis along a descending path, and the lever of the third roller being angularly displaceable about the corresponding pin by an associated drive member independently of the other two levers.
Further characteristics and advantages of the invention will become clearer from the description given below of a presently preferred embodiment of the apparatus according to the invention for supporting and increasing the rigidity of the mandrel back-up bar of a press-piercing mill, reference being made to the appended drawings, given purely by way of non-limiting example, in which:
Figure 1 is a schematic side elevation Al view of apparatus according to the invention;
Figure 2 is a schematic plan view of -the apparatus of Figure l;
Figure 3 is a schematic sectional view, on an enlarged scale, taken on line III-III of Figure 2; and Figures 4 through 6 show details of Figure 3, schematic-,.......

- pa -ally and on an enlarged scale, in different conditions of operation.
Referring first to Figure 1, reference numeral 1 generally indicates apparatus according to the invention for supporting and increasing the rigidity of a mandrel back-up bar

2, used in a press piercing rolling mill 3, the rolling stand of the mill being schematically indicated as 4 and the rolls as Al 6.
This apparatus includes a plurality of identical cradle-shaped supporting structures 7, aligned along a horizontal axis (A) coincident with the rolling and piercing axis of the mill 3.
In the embodiment illustrated, the apparatus 1 includes seven cradle structures of the aforesaid form, disposed in three successive groups which are mutually spaced apart by predetermined distances.
Since the cradle structures 7 are all identical r both structurally and functionally, only one of these is described below the description being with particular reference to Figures

3 to 6.
Each of the cradle structures 7 supports three horizontal pins 8, 9, and 10, disposed parallel to the axis (I ore particularly, the special disposition of the pins Al 9, and 10 is such that their axes lie in a vertical plane perpendicular to the axis (~) (for example the plane of Figure 3) and constitute the vertices of an equilateral triangle, the sauntered of which coincides with the axis (A) in the vertical plane under consider-anion. On each of the pins 8, 9, and 10 is pivoted a correspond-in first-order lever 11, 12t and 13. The lever if, which is basically in the form of a crank, has a forked end ha carrying a horizontal pin I which is parallel to the pin 8. On this pin 14 is pivoted the end 15 of the shaft 16 of a hydraulic cylinder 17 pivotal supported in a conventional manner by the support structure 7.
On the other end of the cranked lever 11 it mounted an idler roller 18. A second idler roller 19 is mounted by con-ventional means (not shown) on the end aye of the lever 12. This lever is mechanically driven by the lever 11 through a rod 20, the opposite ends 21, I of which are rotatable mounted on horizontal pins 23, 24, which are disposed parallel to the pin 8 and are carried by levers 11 and 12, respectively The lever 13 also supports an idler roller 25 at its end facing inwardly of the cradle structure 7. It should be noted that the axes of rotation of the idler rollers 18, 19, and 25, lie in the same vertical plane perpendicular to the axis (A) and intersect the axes of the pins 8, 9, and 10 respectively in this plane. It should also ye noted that the rollers 18, 19, and 25, are identical, and equally spaced from the axes of the pins 8, 9, and 10, about which they are angularly displaceable towards and away from the axis (A), with a self centering type movement which will be better understood from the description given below.
A tie rod 26 has an end 27 rotatable mounted on a horizontal pin 28 which is parallel to the axis (A) and is supported in a conventional manner by the sever 12. At its other end 29, the tie rod 26 slidingly passes through a cylindrical body 30 which is rotatable mounted in a cylindrical seat 31 and Lo I; r--has a horizontal axis parallel to the axis (A). The seat 31 it formed close to the end of the lever 13 and opposite the roller 25 A stop, for example a nut 32 which is adjustable in position, is mounted on the end portion 29 of the tie foal 26 to prevent the tie rod from being withdrawn from the cylindrical body 30.
An hydraulic cylinder 33 is pivot ably supported by the cradle structure 7, and its shaft 34 is rotatable mounted on a horizontal pin 36 which is parallel to the axis (A) and is carried by a pair of lugs 35 fixed to the lever 13.
The lever 13, and its roller 25, are angularly disk placeable in an anti-clockwise sense (with reference to Figures 3-6), while the levers 11 and 12 remain fixed. Similarly these levers 11, 12 with their rollers 18, 19, can be angularly disk placed in a clockwise sense, while the lever 13 remains fixed, or even displaced angularly, in an anti clockwise sense.
The preferred disposition of the fixed pins 8, 9, 10, and of the levers 11, 12, 13, relative to these pins, is such that the idle rollers 18, 19 are moved towards the axis (A along ascending paths while the roller 25 is moved towards the axis (A) along a descending path.
With reference to Figure 2, it should be noted again that the cradle supporting structures which constitute the second and third groups are mutually interconnected and rigidified in a direction parallel to the axis (A) by tie rods and spacers shown schematically at 37, 38, and 39, 40, respectively.
Arms 41, 42 of known type operate iYI the spaces between the groups of cradle structures mentioned above, these arms being used in known manner to carry a mandrel back-up bar 2 into an operative position on the axis (A) end to move the mandrel back-up bar and a blank pa engaged thereon away from this position.
The arms 41r 42l are mounted on horizontal shafts I I
respectively supported on both sides of the apparatus of the invention, preferably in positions which are symmetrical relative to the axis I). The shafts 43, 44 are driven by drive members, not shown since they are conventional, to effect angular disk placement of the arms 41, OWE
lo At the free ends of the arms 41, I basically cradle-shaped heads 45 of known type are pivoted. The other ends of the arms are suitably counterweighted by masses 46, 47.
The operation of the apparatus described above is as follows.
In an initial operative condition (Figure 3), the trios of rollers 18, 19, 25 of each of the cradle structures 7 are maintained in firm contact with the mandrel back-up bar 2 by means of the action of the respective hydraulic cylinders 17.
In this condition the rollers 18, 19 and 25 hold the mandrel back-up bar 2 firmly centered on the piercing axis (I and form a substantially rigid ring around the bar. In other words, a constraint, is created which, by effectively stiffening the bar, improves its resistance to the loads experienced by -the mandrel.
Not only does this result in a smaller degree of eccentricity of the axial piercing of the intermediate blank produced, but it also has the advantage of enabling the use of longer bars to produce axially pierced intermediate blanks of a to greater length in accordance with current technical desiderata.
When the end of the intermediate blank pa reaches a trio of rollers 18, 19, 25; for example, those of the first cradle structure 7, detection devices (not shown since they are con-ventional) send a command to the hydraulic cylinder 17 of this structure. the operation of this cylinder 17 causes an angular displacement (in an anti clockwise sense with reference to Figure 3) of the lever 11 around the axis of the pin 8, resulting in the movement of the corresponding roller 18 away from the mandrel back-up bar 2.
Because of the connection of the lever 11 to the lever 12 by the tie rod 20 and the lever 12 to the lever 13 by means of the tie rod 26, the levers 12, 13 also undergo equal angular displacements in an anti clockwise sense about the axes of their corresponding pins I 10 simultaneously with the lover 11. At the end of these simultaneous equal angular displacements in the same sense, the rollers 18, 19, 25, take up the position illustrated in Figure 4. This position is calculated to allow not only the passage and the advance of the intermediate blank pa on the bar but, also, and above all, a centered support (a bezel type of support) on the axis (A) for the blank itself during its movement.
s a consequence, the gradually increasing weight of the blank is completely supported by the trio of rollers 18, 19 and 25, and, during the entire rolling and piercing phase, the bar 2 is subject solely to the mandrel loading and not to a simultaneous lateral load such as occurred in the prior art procedures. The bar is thus not subject to bending deformations, and this contributes substantially to maintaining it in alignment with the piercing axis.
All the operations described above are then carried out for the roller trios subsequent to the first as they are reached by the blank being produced.
At the end of the piercing operation, the intermediate blank obtained, and the bar inserted therein, must be removed from the plurality of cradle structures 7, and a new mandrel back-up bar must be brought into the position thus vacated.
For this purpose the plurality of cylinders 33 are first actuated simultaneously or otherwise) in the sense so as to displace their respective levers 13 further angularly in the anti-clockwise sense about the axes of the pins lo 11 the rollers 25 (the upper rollers) are thus brought into the non-operative position illustrated in Figure 5. us already described, during the angular displacement of the levers 13, the levers 11, 12, and their rollers 18, 19, remain stationary.
The tie rods 26 do not obstruct displacement of the levers 13 since they are freely slid able in the cylindrical bodies 30 and these latter may rotate freely in their respective seats 31 of the levers 13.
When all the rollers 25 are safely in a position remote from the axis (I (the position shown in Figure 5) in which the intermediate blank and its mandrel back-up bar are supported by the rollers 18, lo, while they are upwardly free, the shaft 44 is operated, which results in the angular displacement of the corresponding over-turning arms 42 and the removal of the inter-mediate blank pa and -the mandrel back-up bar 2 engaged therein (Figure 6).
Operation of the hydraulic cylinders 17 then brings the rollers 18 and 19 into the initial position illustrated in Figure 3 to fox a support for a new mandrel back-up bar 2. This new bar is placed in position by the operation of the other shaft 43 and the corresponding over-turning arms 41. In this condition the mandrel backup bar 2 is already exactly aligned on the piercing axis (A.
Subsequently, operation of the cylinders 33 brings all rollers 25 down into contact properly with the new mandrel back-up bar 2, thus forming the desired plurality of rigid rings which lock the mandrel back-up bar in a centered position on the pierce in axis, giving it the desired rigidity.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for increasing the rigidity and providing centering support for a mandrel back-up bar on the piercing axis of a press-piercing rolling mill, said apparatus comprising a plurality of substantially cradle-like support structures aligned along a common horizontal axis coincident with the piercing axis of the mill, wherein each support structure comprises:
three levers pivoted on respective horizontal pins parallel to the said piercing axis, intersections of the axes of the pins with a vertical plane perpendicular to the said piercing axis, being disposed at the vertices of an equilateral triangle, the centroid of which is the intersection of the said piercing axis with the said vertical plane, three rollers each mounted for free rotation at the end of a respective lever and at the same distance from the corresponding pins, the axes of rotation of the rollers lying in a common vertical plane, perpendicular to the said piercing axis and each intersecting in the same plane the axis of the corre-sponding pin, and drive members for angularly displacing the levers and their respective rollers about the said pins towards and away from the said piercing axis with substantially self-centering type movements, two of said rollers being contem-poraneously moved towards the piercing axis along respective ascending paths, the third roller being moved towards said piercing axis along a descending path, and the lever of said third roller being angularly displaceable about the corresponding pin by an associated drive member independently of the other two levers.