VARIABLE RAKE SHEAR

Abstract

A variable rake shear comprises a housing (8), a first blade (1) mounted in a first blade mounting (4), a second blade (2) mounted in a second blade mounting (3); and a control device (5) to control movement of one blade mounting to shear the material. Each blade mounting is movable in at least one dimension relative to the housing. One blade is an active blade (1) and the other blade is a passive blade (2). A rake adjustment mechanism (6a, 6b) for at least one of the mountings (3, 4) and the mounting (4) for the active blade (1) has a torque tube linkage mechanism (10, 11, 12).

Claims

1. A method of operating a variable rake shear to shear material, the method comprising; mounting a first blade in a first blade mounting, mounting a second blade in a second blade mounting, wherein each blade mounting is movable in at least one dimension relative to the housing to move the blades toward and past each other for shearing; applying a rake angle to one of the first and second blade mountings; wherein one blade is an active blade and the other blade is a passive blade; connecting the first blade mounting of the active blade to a torque tube linkage mechanism configured for; and controlling movement of the first blade mounting of the active blade to shear the material.

2. A method according to claim 1, further comprising applying the rake to the active blade by disconnecting a clutch in the torque tube linkage mechanism of the blade mounting, adjusting the rake angle of the blade in the blade mounting; and reconnecting the clutch.

3. A method according to claim 1, further comprising applying the rake to the passive blade by adjusting one or more mechanical adjusters connected between the housing and the blade mounting of the passive blade.

4. A method according to claim 3, comprising setting a minimum vertical gap between the blades before shearing a material by using at least two of the adjusters.

5. A method according to claim 1, comprising the adjusting of the rake angle is according to the thickness and strength of the material to be sheared.

6. A method according to claim 1, comprising altering the rake of one or both blades between successive cuts on the same piece of material.

7. A method according to claim 1, further comprising applying the rake to at least one of the first and second blade mountings.

8. A method according to claim 1, further comprising applying the rake to the blade contacting a part of the material to be scrapped.

9. A method according to claim 1, further comprising varying stroke of movement of the active blade according to at least one of the rake angle of the or each blade, the width of material being sheared, the position of the material relative to the centreline of the shear and the elongation to fracture of the material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] An example of a variable rake shear in accordance with the present invention will now be described with reference to the accompanying drawings in which:

[0042] FIG. 1A illustrates a front view of a conventional prior art up-cut hydraulic shear;

[0043] FIG. 1B illustrates a bottom view thereof;

[0044] FIG. 2A illustrates an example of a variable rake shear according to the present invention before varying the rake;

[0045] FIG. 2B is a bottom view which shows torque linkage elements of FIG. 2A in more detail;

[0046] FIG. 2C shows one side of FIG. 2A from outside its housing;

[0047] FIG. 2D shows one side of FIG. 2A from inside its housing;

[0048] FIG. 3 shows the example of FIG. 2A, with the top blade raked;

[0049] FIG. 4A illustrates an example of a variable rake shear according to the present invention before varying the rake;

[0050] FIG. 4B shows the torque linkage elements of FIG. 4A in more detail;

[0051] FIG. 4C shows one side of FIG. 4A from outside its housing;

[0052] FIG. 4D shows one side of FIG. 4A from inside its housing;

[0053] FIG. 5 shows the example of FIG. 4A with the bottom blade raked;

[0054] FIG. 6A-6D show a first alternative blade rake adjuster for the embodiments in FIG. 4;

[0055] FIGS. 7A-7D show a second alternative blade rake adjuster for the embodiments in FIG. 4;

[0056] FIGS. 8A-8D show a third alternative blade rake adjuster for the embodiments in FIG. 4;

[0057] FIGS. 9A-9D show a fourth alternative blade rake adjuster for the embodiments in FIG. 4; and

[0058] FIGS. 10A-10D show corresponding embodiments to the embodiments in FIG. 4, except that the top blade is the active blade, the torque tube linkage is connected to the top beam, the torque tube linkage and appropriate other components of the variable rake shear of FIGS. 4A-4D have been moved accordingly, and a control device is shown in FIG. 10B.

DESCRIPTION OF AN EMBODIMENT

[0059] For the purpose of this disclosure, the term rake means the angle of the top blade relative to the bottom blade in the plane of the cut. An example of a variable rake shear according to the present invention is illustrated in FIGS. 2A-2D and 3. FIG. 2A is a view from in front of the shear, with both blades 1, 2 in their initial positions. A first blade 1 is mounted in one upwardly facing edge of a first beam 4 which is able to move vertically within the structure of a housing 8 on slideways, via guides 9, one guide at each side of the beam and thereby at each side of the housing. Some surfaces of the beam 4 may make contact with each side wall of the guides 9 as shown in FIGS. 2C and 2D. The beam is supported on cutting cylinders 5. In the preferred embodiment there are two cutting cylinders 5 so that the cutting forces can be easily and directly transferred into the two sides of the housing 8, but embodiments with a single cutting cylinder or with more than two cylinders are also possible. The beam 4 is also connected to a torque linkage 10, 11, 12, 13, illustrated in more detail in FIG. 2B. The torque linkage comprises a torque tube 12 on torque tube bearings 13 and torque links 10 on torque tube arms 11 connected to the torque tube 12. The other end of the torque links 10 connect to the beam 4. The torque linkage ensures that the bottom beam 4 and blade 1 stay almost horizontal whatever the moments on the beam 4 from the cutting force and the cylinder forces acting on the beam.

[0060] When cutting, there is an active and a passive blade. In this example the bottom blade is the active blade and with more than one cylinder, the total cutting force applied to the blade is equal to the sum of the cutting forces from all the cylinders. However, if the active blade has no torque tube linkage (as is the case in the conventional up-cut shear described above), then the forces in the cylinders vary during the cutting cycle. At the start of the cut cycle the cylinder associated with the leading end of the blade sees a high force while the cylinder associated with the trailing end of the blade sees a low force. At the end of the cutting cycle it is the trailing end cylinder which sees the high force while the leading end cylinder sees the low force. Added together, the cylinder forces at any point during the cutting cycle equal the cutting force, but the maximum forces seen by the cylinders at any point in the cutting cycle when added together amount to significantly more cutting force, for two cylinders this is approximately double. The advantage of the torque tube linkage is that the load is shared between the cylinders 5 equally, so the sum of the maximum forces in the cylinders is equal to the maximum cutting force. Thus, the two cutting cylinders 5 only need to produce approximately half of the maximum cutting force each and each cylinder can be smaller than without the torque tube linkage.

[0061] A second blade 2 is mounted in one downwardly facing edge of a second upper beam 3 which is also able to move within the structure of a housing 8 on slideways, via guides 9 and some surfaces of the second beam 3 may come into contact with each side wall of the guides 9 as shown in FIGS. 2C and 2D. The beam 3 is connected at positions located toward its opposite side edges to adjusters 6a, 6b, typically mechanical adjusters. Such mechanical adjusters may be selected from various alternatives. The two such adjusters allow the rake of the shear to be adjusted by operating each adjuster in a respective manner.

[0062] Adjusters 6a and 6b in FIGS. 2A, 3 and FIGS. 4A-4D are screws which extend from upper beam 3 through threaded openings 21 in housing part 8a. Adjustment of each screw determines the rake.

[0063] The mechanical adjusters, which take the form of adjusters 6a and 6b in FIGS. 2A, 3, and 4A-4D, are, in FIGS. 6A-6D, movable supports 22a, 22b with three height steps 23, 24, 25. Respective shift mechanism 26 for each support 22a, 22b moves a selected one of the steps of that support between one end region of the beam 3 and the housing 8 for adjusting the rake. The selection of a respective step of each support determines the rake.

[0064] The mechanical adjusters, movable wedges 27a, 27b, shown in FIGS. 7A-7D, are movable like movable supports 22 a, 22b, in FIGS. 6A-6D. Each wedge is moved by a respective shift mechanism 28 to adjust the spacing between the beam 3 and the housing 8. Each wedge has a top surface 29a, 29b that engages a cam block 30 supported on housing part 8a to cause the adjustment.

[0065] The mechanical adjusters, adjustable eccentrics 31 shown in FIGS. 8A-8D each comprise a rockable beam 31a, 31b on the beam 3, an eccentric connection at 32 to a rotatable disk 33, which rotates on a support 34. Rotation of the disk 33 by a handle 34a adjusts the rake of the blade 2.

[0066] Cams 35a, 35b shown in FIGS. 9A-9D operate like the eccentrics 31 shown in FIGS. 8A-8D. Each support 36a, 36b on the housing part 8a supports a cam 35a, 35b to rotate. The cams 35a, 35b also contact a respective cam follower 37a, 37b fixed on the beam 3. Rotation of the cam by the handle 39 causes the shaped profile 40 of each cam to adjust the spacing between the beam 3 and the housing part 8.

[0067] FIGS. 10A-10D show the embodiments of FIG. 4A-4D, except that the top blade 2 has become the active blade, instead of the passive blade, as shown in FIGS. 4A-4D, and the bottom blade 1 has become the passive blade, instead of the active blade, as shown in FIGS. 4A-4D, and the torque tube linkage 10, 11, 12, 13, the cutting cylinders 5a, 5b, the hydraulic balancing cylinder 7, and the adjusters 6a, 6b have been moved accordingly. In particular, torque tube linkage 10, 11, 12, 13 and cutting cylinders 5a, 5b are now located above upper beam 3, instead of being below bottom beam 4, in FIGS. 4A-4D. Torque tube linkage 10, 11, 12, 13 is connected to upper beam 3, instead of being connected to bottom beam 4, as shown in FIGS. 4A-4D. Adjusters 6a and 6b and hydraulic balancing cylinders 7 are now located below bottom beam 4, instead of being above upper beam 3, as shown in FIGS. 4A-4D. In addition, FIGS. 10B shows control device 20 controlling torque tube linkage 10, 11, 12, 13 so as to control movement of the blade mounting, upper beam 3, to which torque tube linkage 10, 11, 12, 13 is connected.

[0068] Although the adjustment mechanism could be implemented by hydraulic cylinders, that would add unnecessary cost and complication to the shear because the hydraulic cylinders would need to able to withstand the full cutting force unless they were combined with a mechanical locking system or a mechanical leverage system. The adjustment of the rake of the blade is usually only done at set-up, so a mechanical adjuster which can easily be adjusted when there is no cutting force and can then be locked in position during cutting is quite sufficient. Another mechanical adjustment option would be a series of moveable blocks or packers between the housing and the beam to allow the beam to be supported at different heights at each end, according to which block or packer was in use at each end. This is a less precise, but lower cost option, which is acceptable if precise top blade positioning is not required.

[0069] For ease of set-up, as illustrated in this embodiment, the beam 3 hangs from a hydraulic balancing cylinder 7, but this could be omitted with the screws, or other mechanical adjustment mechanism, supporting the beam, as well as adjusting its rake angle. Alternatively, a single screw towards one end of the beam may provide both support and adjustment, with a fixed support in the housing guide at the opposite end providing a surface on which the other end of the beam 3 pivots.

[0070] FIG. 3 shows the embodiment of FIG. 2A, with the second blade 2 at a raked angle. This is achieved by extending the screw 6a and by retracting the screw 6b, so that the second beam 3 pivots in the housing guide 9, resulting in the relative angle of the first blade and second blade varying. The rake of the second blade is varied so that it is optimised for the material being cut. In addition, the blade height position may also be varied by suitable adjustments to the length of the screws. Before the cut takes place, there is a gap between the lowest part of the top blade and the uppermost part of the bottom blade. This gap is chosen according to the thickness of the material to be cut. Position control is provided on the lift of the up-cut blade, so that the stroke is appropriate for the variable top blade geometry. When the rake angle of the blade is steep the bottom blade 1 clearly has to lift up much further to complete the cut than when the rake angle is shallow. If desired the stroke of the up movement to carry out the cut can also be adjusted according to the width of the material being cut, the position of the material relative to the centre-line of the shear and/or the elongation to fracture of the material being cut. Position measurement is required for limited stroke control and this is typically provided by position transducers mounted within the cutting cylinders 5 or by position transducers attached between the bottom beam 4 and the housing 8 (not shown).

[0071] Having set up the rake angle and initial position of the up-cut blade, material is passed along the line for shearing, and transported along roller tables at each side of the shear. A controller (not shown) actuates the cylinders 5 to perform the cut between the first and second blades.

[0072] The design of the present invention allows the rake angle to be set according to the specific requirements of the material to be cut, so for example, a high rake angle is only used for the very hardest, thickest slabs, whereas for thinner slabs or plates the rake angle is far less and in some cases may even be zero. The optimisation of angle may be based on real mill set up or actual slab conditions, rather than a pre-set assumption, so for example, when the temperature of thick or hard slab is high, then the rake angle can be reduced accordingly. Operating at lower rake angles, wherever possible, reduces side thrust.

[0073] Without the variation in rake angle provided by the invention, all material, whatever its thickness would be subject to the same amount of lift and impact as it dropped back onto the table, but the invention means there is only high lift only for the hardest, thickest plates and thinner plates are lifted far less distance and so suffer reduced impact from drop back onto the table compared to the impact the plate or slab would have suffered in a conventional up-cut raked shear. This reduces damage and marking of the slab.

[0074] Another advantage of setting the rake angle only as high as necessary for the specific material passing through the shear is that the cycle time for thin, or soft, slabs is reduced because of a reduced stroke requirement. Also the distortion of the thinner and softer slabs is minimised by setting the rake angle as low as possible.

[0075] Furthermore, the invention is easily adapted to suit different widths of shears and different maximum slab thicknesses. The use of a mechanical adjuster is safer and has no energy consumption when in stationary position, nor risk of leakage of hydraulic fluid onto the material, as there would be with hydraulic cylinders located above the material. The same mechanism allows for both long stroke adjustment for different slab thickness and for differential positioning to adjust the rake angle. The system is able to fit with a mill set up system and operate efficiently.

[0076] A solution for altering the rake of the bottom blade is illustrated in FIGS. 4A-4D and FIG. 5. FIG. 4A, like FIG. 2A illustrates the two blades 1, 2 in their initial positions. The first blade 1 mounted in one edge of the first beam 4 movable within the structure of a housing 8 on slideways via guides 9. Some surfaces of the beam 4 may make contact with each side wall of the guides 9 as shown in FIGS. 4C and 4D. The beam is supported on cutting cylinders 5a, 5b. In the preferred embodiment there are two cutting cylinders 5a, 5b so that the cutting forces can be easily and directly transferred into the two sides of the housing 8, but embodiments with a single cutting cylinder, or with more than two cylinders are also possible. The beam 4 is also connected to a torque linkage 10, 11, 12, 13, illustrated in more detail in FIG. 4B. In FIG. 4B it can be seen that in this embodiment, the torque tube is split into two parts 12a and 12b and these two parts are linked by a clutch 16. This is also visible in FIG. 4D. In order to change the rake of the bottom blade 1 as illustrated in FIG. 5, the clutch 16 is released and cylinders 5a and 5b are set to different strokes, so that the blade 1 takes up the required rake. The clutch 16 is then engaged to lock the two parts of the torque tube 12a and 12b together again. As shown in FIG. 5, the links 10 require spherical bushes 17 or a similar connection where they connect to the beam 4 and torque arms 11, in order to allow the beam to take up an angle relative to the torque tube. During the cutting action the torque tube mechanism maintains the rake angle constant and ensures that each of the cylinders 5a and 5b only needs to generate half of the maximum cutting force. The term clutch for the mechanism 16 includes mechanisms which engage and disengage teeth as well as friction type clutches and other mechanisms which allow parts of the torque tube 12a and 12b to be rotated relative to one another and then locked together.

[0077] The shear may have either the top blade adjustment mechanism illustrated in FIGS. 2A-2D and 3, or the bottom blade adjustment mechanism illustrated in FIGS. 4A-4D and 5, or it may incorporate both mechanisms. The advantage of incorporating both mechanisms is that it is possible to minimise the distortion of the prime material.

[0078] The shear is often used to do both a head crop and a tail crop on the material. As an example, if the top raked blade is on the head end side of the shear and the horizontal bottom blade is on the tail end side of the shear, then for the head crop the raked top blade contacts the scrap head end material whereas the prime material of the plate is in contact with the horizontal bottom blade and therefore there is minimum distortion of the prime material. However, for the tail crop it is the prime material which is in contact with the raked top blade and the scrap tail end which is in contact with the horizontal bottom blade. Consequently there is distortion of the prime material which is not desirable.

[0079] However if the shear incorporates both the top blade adjustment mechanism and the bottom blade adjustment mechanism, then a choice of which blade is raked can be made. For the head end crop the bottom blade which is in contact with the prime material of the plate is horizontal and the top blade which is in contact with the scrap head end is raked. But for the tail end crop the top blade which is in contact with the prime material of the plate is made horizontal whilst the bottom blade which is in contact with the scrap tail end is raked. In this way any distortion of the prime material is minimised.

[0080] In the case of a divide cut where the shear is used to divide a long plate into two or more shorter plates then both the head side and the tail side of the cut are prime material and so ideally there should be minimum distortion of both sides. In this case both the top and bottom blades can be raked each at half the rake angle that would be required if only one blade was raked and thus the distortion of both the head side and the tail side of the cut are minimised.

[0081] In addition to the mechanism for adjusting the rake of the top blade and the mechanism for adjusting the rake of the bottom blade the shear can also incorporate a toggle mechanism similar to that of the prior art shear illustrated in FIGS. 1A and 1B. For example the toggle mechanism may be installed between the top of the housings 8 and the screw adjusters 6a, 6b such that the screw adjusters alter the rake of the blade and provide fine control of the gap between the blades and the toggle mechanism allows the shear to open quickly to a very large gapfor example for cobble clearanceand to close quickly to the cutting position when a cut is required.

[0082] Whilst the descriptions above refer to an up-cut type shear in which the bottom blade moves up to perform the cutting operation, mechanisms similar to those described may also be used on a down-cut type shear in which the top blade moves down to perform the cutting operation.

[0083] Many shears incorporate hold down equipment, or clamps to hold the material in place during the shearing operation. If the hold down equipment is attached to the blade beams, as is often the case, then some minor modifications to the design may be required to accommodate the varying rake of the blade beam, but these are simplefor example mounting the hold down equipment directly on the housing or having a pivoting mechanism in the hold down equipmentand will not be described in detail. In the case of a shear where both the top and bottom blades can be adjusted for rake it may be advantageous to have two sets of hold down equipment one to clamp the material against the bottom blade and a separate set to clamp the material against the top blade. If the shear is going to be operated with both blades raked, then it may be advantageous to arrange the material clamping equipment to keep the plate horizontal instead of clamping against one or other of the blades.