METHOD OF SHEARING METAL STRIP AND APPARATUS THEREFOR

Abstract: The invention relates to an apparatus for cutting metal strip comprising first and second rotatable drums (6, 7) with corresponding first and second cutting means arranged side-by-side so that the metal strip may pass between them, the first and second cutting blade means (8, 9) is retractable between a first retracted position in which the strip is permitted to pass freely between the drums (6, 7) whilst they are rotating and a second extended position in which the blade means (8, 9) extends ourwardly from the drum (6, 7) to cut the strip. The first and second drums (6, 7) are provided with an actuator rod (21, 22) arranged axially in the drum such that axial movement of the actuator rod (21, 22) results in corresponding extension or retraction of the cutting blade means. The first cutting blade means may be fixed and the second cutting blade means is retractable or alternatively both may be retractable. Axial movement of the actuating rod (21, 22) causes extension followed by retraction of the blade in a single movement of the actuating rod (21, 22) by means of an external surface which undulates along its length.

Description: Method of Shearing Metal Strip and Apparatus Therefor The invention relates to a method of shearing metal strip and apparatus therefor. In particular the invention relates to the shearing of continuous strip at the end of its production into finite lengths which are coiled onto a spool. In many strip production facilities the shearing has to take place whilst the strip is moving at high speed and modern strip production requires the strip to be moving at higher and higher speeds to ever greater efficiencies in production costs. Typically in known systems, a rotary shear is used to cut metal strip which is moving. Such a conventional rotary shear is shown schematically in fig. 1. The shear consists of two rotating drums 1 , 2, each of which has cutting blades 3, 4. The two drums rotate in opposite directions as indicated by the aiTOws and are usually geared together. Separate guide means are usually provided to guide the strip onto a coil at the end of a rolling mill line and to transfer the strip to a second coil when a first coil is complete, whilst at the same time permitting the continuous production of the strip at an uninteiTupted rate. The strip 5 passes between the two drums as shown. When the strip is to be cut, the two drums are accelerated from rest until the peripheral speed of the blades is equal to the strip speed. The peripheral speed of the blades needs to be closely matched to the speed of the strip otherwise the shear will cause a tension snatch in the strip which could damage the strip, the shear or other equipment in the line. After the blades have cut the strip, the drums are then decelerated back to rest. With such a conventional rotary shear, since the drums cannot be allowed to rotate through the cutting position more than once, the maximum speed at which the strip can be cut is limited by the power required to accelerate and decelerate the drums within a fraction of one revolution. To accelerate the drums to a higher speed requires more power which in turn requires a bigger drive motor which in turn increases the total inertia of the system and thus demands even more power. It is possible for rotary shears of this type to have more than one set of blades. In these cases the problem of accelerating and decelerating the drums is even more pronounced because a smaller fraction of a revolution is available for acceleration and deceleration. It is therefore an objective of the present invention to provide a shearing apparatus which can cut strip at higher speeds. It is also an objective of the invention to provide a shearing apparatus which can incorporate more than one set of blades and still cut at high speed. According to the invention there is provided an apparatus for cutting metal strip comprising first and second rotatable drums arranged side-by-side so that the metal strip may pass between them, the first drum being provided with a first cutting blade means and the second drum being provided with a second cutting blade means, characterised in that at least one of the first and second cutting blade means is retractable between a first retracted position in which the strip is permitted to pass freely between the drums whilst the drums are rotating and a second extended position in which the blade extends outwardly from the drum to cut the strip and that at least one of the first and second drums is provided with an actuator rod arranged axially in the drum such that axial movement of the actuator rod results in corresponding extension or retraction of the cutting blade means. Preferably the first cutting blade means is fixed and the second cutting blade means is retractable. Alternatively both the first and second cutting blade means are retractable. The first and second cutting blade means may comprise corresponding first and second cutting edges said first and second cutting edges having different longitudinal profiles. Preferably, stops are provided to limit the movement of the cutting blade means. Preferably the actuator rod(s) comprise(s) an external surface which undulates along its length and is arranged axially in the drum such that axial movement of the actuator rod results in corresponding extension and retraction of the cutting blade means. Preferably, rollers are provided between the actuator rod and the cutting blade means. Each of the first and second drums may comprise a corresponding first and second actuator rod, said first and second actuator rods being coupled together to synchronise the movement of the first and second cutting blade means. The first and/or second drum may be provided with a hydraulic cylinder which is operable to move the corresponding cutting blade means between the first and second positions. Alternatively, at least one of the first and second drums may be provided with a central cam rod having a non-circular cam-shaped circumference such that rotation of the central cam rod causes the corresponding cutting blade means to move between the first and second positions. Preferably, a balance weight is provided at the opposite side to the cutting blade means. According to the invention there is provided a method of cutting metal strip using the apparatus of claim 1 , characterised in that the drums are rotated at a speed which is approximately the same as the speed of the metal strip and, at the desired time, the cutting blade means is extended and cuts the strip, and is subsequently retracted before a revolution of the drum is completed. The drum may be accelerated and decelerated to and from the speed of the strip before and after the cutting action, and the acceleration or deceleration continues over an angular rotation of more than one revolution of the drum. Alternatively, the drums may rotate continuously at approximately the speed of the strip. An exemplary embodiment of the apparatus and method of the invention comprising two drums each with a single retractable blade will now be described will the aid of the appended drawings in which: l ; ig. 1 is a schematic side view of a known rotatable shear means; Fig. 2 is a schematic side view of a rotatable shear of the invention, Fig. 3 is a schematic side view of a rotatable shear of the invention in an alternative position, Fig. 4 is a schematic side view of a rotatable shear of the invention, immediately after the cutting position, Fig. 5 is a more detailed cross section of the rotating shear of the invention through the axis of the drum, and Fig. 6 is a transverse cross section of the drums in fig. 5. The prior art rotatable shear of fig. 1 is discussed above. Figures 2, 3 and 4 are schematic views of a side elevation of the apparatus and method of an exemplary embodiment of the invention. The strip is travelling in the direction of arrow A. The two drums 6, 7 contain blades 8, 9 which can be retracted into the drum, which is the position shown in figure 2, or which can be extended to a position in which they would cut the strip as shown in figs. 3 and 4. With the blades in the retracted position the drums are able to rotate fully without the blades coming into contact with the strip. With this apparatus, it is not necessary to accelerate the drums to match the strip speed within the space of less than one revolution; the acceleration of the drums up to strip speed can occupy more than one full revolution, typically two or more revolutions. Alternatively the drums could rotate continuously at strip speed. The blades 8, 9 comprise corresponding first and second cutting edges said first and second cutting edges which may have different longitudinal profiles. When a cut is required, the blades 8, 9 are moved to the extended position as shown in figure 3, and the drums continue rotating until the cut is made as shown in figure 4, after which the blades are retracted again back to the position shown in figure 2. In the more detailed exemplary embodiment of the invention shown in figures 5 and 6, the blades 13,14 are retracted and extended by a rod which runs down the centre of each drum. Figure 5 is a cross-section of the apparatus showing the two drums 10, 1 1 each with a retractable blade 13, 14. For illustration purposes, the blade 14 is shown in the retracted position whilst blade 13 is shown in the extended position. In practise the movement of the two blades is synchronised by the cross piece 20 so that both blades are extended or retracted together. It will be readily apparent that axial movement of the rods 15, 16 causes the profiled sections 21 and 22 to move axially and, since the blade assemblies are prevented from moving axially, the rollers 23, 24 follow the profiles 21 , 22 and hence move the blades in or out radially. In the exemplary embodiment the rods 15, 16 are moved by a hydraulic cylinder 17. Thrust bearings 18, 19 are used so that the rods can rotate with the drums but the cylinder and cross piece can remain stationary with respect to the rotation of the rod. A transverse cross section of the drums 10, 1 1 , the blades 13, 14, the profiled section of the actuating rods 21 and 22 and the rollers 23, 24 is illustrated in figure 6. The upper drum 10 is shown with the blade out and the larger diameter sections of the rod 21 engage the rollers 24, forcing the blade means 13 outwards from the drum 10. The lower drum 1 1 is shown with the smaller diameter sections of the rod 22 engaging the rollers 24 and the larger diameter sections of the rod act on the rollers 23 which forces the blade means back into the drum 1 1. In an alternative embodiment of the invention which is not shown, the first and/or second drum is provided with a hydraulic cylinder which is operable to move the corresponding cutting blade means between the first and second positions. Stops (not shown) are preferably provided on the drums to limit the movement of the cutting blade means. In a further alternative embodiment of the invention which is not shown, the first and/or second drum is provided with a central cam rod having a non- circular cam-shaped circumference such that rotation of the central cam rod causes the corresponding cutting blade means to move between the first and second positions. Preferably, a balance weight is provided at the opposite side to the cutting blade means. It will be appreciated that by means of the invention a considerable increase in the speed of operation of the shear can be achieved as well as a considerable reduction in the power required to accelerate and decelerate the drums. It will also be appreciated that the invention is not limited to the exemplary embodiment described above, but is intended to include any other embodiment within the concept of the invention as defined in the appended claims.

Claims: CLAIMS 1. An apparatus for cutting metal strip comprising first and second rotatable drums (6, 7) arranged side-by-side so that the metal strip may pass between them, the first drum (6) being provided with a first cutting blade means (8) and the second drum (7) being provided with a second cutting blade (9) means, characterised in that at least one of the first and second cutting blade means (8, 9) is retractable between a first retracted position in which the strip is permitted to pass freely between the drums (6, 7) whilst the drums are rotating and a second extended position in which the at least one blade means (8, 9) extends outwardly from the drum to cut the strip and that at least one of the first and second drums (6, 7) is provided with an actuator rod (21, 22) arranged axially in the drum such that axial movement of the actuator rod (21, 22) results in corresponding extension or retraction of the cutting blade means. 2. An apparatus according to claim 1 , characterised in that the first cutting blade means (8) is fixed and the second cutting blade means is retractable (9). 3. An apparatus according to claim 1 , characterised in that both the first and second cutting blade means (8, 9) are retractable. 4. An apparatus according to claim 1 , characterised in that axial movement of the actuating rod (21 , 22) causes extension followed by retraction of the blade in a single movement of the actuating rod (21, 22). 5. An apparatus according to claim 1 , characterised in that the actuator rod (21 , 22) comprises an external surface which undulates along its length. 6. An apparatus according to claim 1 , characterised in that rollers are provided between the actuator rod (21, 22) and the cutting blade means 8,9. 7. An apparatus according to claim 1 , characterised in that each of the first and second drums (6, 7) comprises a corresponding first and second actuator rod (21. 22), said first and second actuator rods (21 , 22) being coupled together to synchronise the movement of the first and second cutting blade means (8, 9). 8. An apparatus according to claim 1 , characterised in that at least one of the first and second drums (6, 7) is provided with a hydraulic cylinder which is operable to move the corresponding cutting blade means (8, 9) between the first and second positions. 9. A method of cutting metal strip using the apparatus of claim 1 , characterised in that the drums (6,7) are rotated at a speed which is approximately the same as the speed of the metal strip and, at the desired time, the cutting blade means (8, 9) is extended and cuts the strip, and is subsequently retracted before a revolution of the drum is completed. 10. A method of cutting metal strip according to claim 13, characterised in that the drum (6, 7) is accelerated and decelerated to and from the speed of the strip before and after the cutting action, and the acceleration or deceleration continues over an angular rotation of more than one revolution of the drum.

Inventors: BERRY JOHN, COOPER BRIAN, SCHOFIELD SIMON, BERRY, JOHN, COOPER, BRIAN, SCHOFIELD, SIMON
Applicants: BERRY JOHN, COOPER BRIAN, KVAERNER TECH & RES LTD, SCHOFIELD SIMON, BERRY, JOHN, COOPER, BRIAN, KVAERNER TECHNOLOGY & RESEARCH LIMITED, SCHOFIELD, SIMON
Application year: 1998
Main classification: B23D25
IPC codes: B23D25, B26D1