High speed flying shear

Abstract: A flying shear (10) has leader and follower blades (28,24) rotating in opposite directions abut parallel axes (14,16) located above and below a horizontal plane (P H ). The radius of rotation of the leader blade (R L ) is longer than the radius of the follower blade (R F ). The blades are configured and arranged to coact in a radially overlapping relationship at a cutting zone (Z 1 , Z 2 ) spaced vertically from the horizontal plane. A switch (30) directs longitudinally moving products such as bars, rods, and the like from the horizontal plane across the cutting zone for separation by the rotating blades into leading and trailing segments.

Description: This invention relates to flying shears for cropping the front and tail ends of hot rolled steel rods and other like products being delivered from a continuous high speed rolling mill, (see for example EP-A-0 655 291). Rods, bars, and other like long products produced by a continuous hot rolling process inevitably have off gauge front and tail ends that must be "cropped", i.e., severed and discarded. This can be accomplished by manual trimming after the products have left the rolling line. However, manual trimming requires the constant attention of mill personnel, and is both inefficient and expensive. Preferably, therefore, cropping is effected by so-called "flying shears" designed to operate automatically on line at mill delivery speeds. Although flying shears have operated successfully in the past, improvements in their design have failed to keep pace with ever increasing mill delivery speeds, which in modern day high speed rod mills are now reaching 100-120 m/sec. The objective of the present invention is the provision of an improved flying shear which is fully capable of operating reliably at all mill delivery speeds, including the highest delivery speeds of modern day rod mills. Accordingly the present invention provides a shear for subdividing an elongated product moving longitudinally in a plane, said shear comprising: leader and follower blades mounted for rotation about parallel axes located on opposite sides of said plane, said blades being arranged to coact in a radially overlapping relationship at a cutting zone located between said axes and spaced vertically from said plane, the radius of rotation of said leader blade being longer than the radius of rotation of said follower blade; means for continuously rotating said blades at equal angular velocities, with said leader blade preceding said follower blade in said cutting zone; and switch means located upstream of said cutting zone, said switch means being operable in a first mode to direct said product along a path bypassing said cutting zone, and being operable in a second mode to divert said product from said path into said cutting zone for cutting by said blades into leading and trailing segments, said blades being configured and arranged to deflect the tail end of said leading segment away from said plane while directing the front end of said trailing segment toward said plane. In accordance with another aspect of the present invention, the shear is preferably provided with two sets of the aforesaid blades arranged in a side-by-side arrangement, one set being operable to crop a product front end, and the other set being operable to crop the product tail end. In accordance with still another aspect of the present invention, the cropped ends and intermediate acceptable product lengths are received in the separate guide passageways of a stationary trough located downstream of the cutting zone. Chopping shears operate to subdivide the cropped ends into shorter scrap pieces. These and other features and objectives of the present invention will now be described in great detail with reference to the accompanying drawings, wherein: Figure 1 is a view in side elevation of a shear in accordance with the present invention; Figure 2 is a top plan view of the shear; Figure 3 is a sectional view taken along line 3-3 of Figure 1; Figure 4 is a diagrammatic illustration of the speed relationship between the leader and follower blades; Figure 5 is an enlarged plan view of the switch assembly; Figure 6A is a view taken along line 6A-6A of Figure 5; Figure 6B is a sectional view taken along line 6B-6B of Figure 5; Figure 7 is a sectional view on an enlarged scale taken along line 7-7 of Figure 1; Figure 8 is a view of the cropping discs and blades taken along line 8-8 of Figure 1; Figure 9 is a partial view of the cropping discs and blades with the stationary trough shown in the background; Figures 10A-10D are schematic illustrations showing a typical cropping cycle; and Figure 11 is a schematic view showing the path of travel of the product as it is directed across the two cutting zones of the cropping shear. Referring initially to Figures 1-3, a shear in accordance with the present invention is depicted generally at 10. The shear includes a stationary housing 12 rotatably supporting a parallel pair of upper and lower shafts 14, 16. The shafts are mechanically coupled by intermeshed gears 18, with the lower shaft 16 being driven continuously by a motor 20. An upper rotor 21 is mounted in cantilever fashion on the upper shaft 14. As can best be seen by additional reference to Figures 8 and 9, rotor 21 has axially spaced rims 22 each carrying an upper "follower" blade 24. A lower rotor 25 is similarly mounted in cantilever fashion on the lower shaft 16. Rotor 25 has axially spaced rims 26 each carrying a lower "leader" blade 28. As can best be seen when viewed from left to right in Figures 8, 9 and 11, the rims 26 are each laterally preceded by ramps 29 having gradually increasing diameters. The shafts 14, 16 and their respective rotors 21, 25 and blades 24, 28 are contrarotated continuously by the motor 20 at equal angular velocities as shown by the arrows identified at V a in Figure 1. The leader blades 28 precede the follower blades 24 in a radially overlapping relationship as they rotate through laterally spaced cutting zones Z 1 , Z 2 . With reference to the diagrammatic depiction in Figure 4, it will be understood that the radius of rotation RL of the leader blades 28 (measured from the axis of rotation of shaft 16 to the outermost tip of the blade) is longer than the radius of rotation RF of the follower blades 24. It follows, therefore, that for any given angular blade velocity V a , the tangential tip velocity V TF of the leader blades 28 will exceed the tangential tip velocity V TF of the follower blades 24. Thus, as shown by the overlapping tangential velocity profiles P L , P F of the leader and follower blades 28, 24, at each point in the area of radial blade overlap in the cutting zones, the tangential speed of the leader blades will exceed that of the follower blades. This speed differential allows for maximum blade overlap without attendant damaging interference between the coacting blades. With reference additionally to Figures 6A and 6B, it will be seen that a switch 30 is located upstream of the cutting zones Z 1 , Z 2 . The switch includes a guide pipe 32 mounted as at 34 for pivotal movement in a horizontal plane P H in which the product to be cropped, e.g., hot rolled steel rod R, exits from the mill. The pipe 32 may be pivoted by any appropriate mechanism, such as a servo motor 36 acting through a gear head 38 to rotate a drive gear 40. Gear 40 meshes with a rack 42 on an arm pivotally connected to and extending laterally from the pipe 32. As shown in Figure 5, the pipe 32 is pivotally shiftable between positions indicated at "a", "b" and "c". A stationary guide trough 44 is arranged downstream of the cutting zones Z 1 , Z 1 . As can be best seen by additional reference to Figure 7, the guide trough is internally divided by walls 46 into three passageways 48a, 48b, and 48c. The walls 46 each have a horizontal segment defining a ledge 46 positioned slightly above the horizontal plane P H . The housing 12 also rotatably supports additional upper and lower parallel shafts 48, 50 downstream of the stationary trough 44. The shafts 48, 50 are mechanically coupled by gears similar to those shown at 18 in Figure 3, and carry side-by-side cantilevered discs 52, 54. These discs carry multiple chopping blades 56 designed to coact at cutting zones aligned with the passageways 48a, 48, of the upstream trough 44. The chopping blades are contrarotated continuously by a drive motor 58 connected to the lower shaft 50. Referring now to Figures 2, 9 and 10A-10D, the shear operates in the following manner: Front End Crop At the beginning of a front end cropping sequence, the guide pipe 32 of switch 30 is shifted to the position indicated at "a". This causes the off gauge front end of the product to bypass cutting zone Z 1 and to pass through guide passageway 48a of trough 44 for subdivision by the chopping blades 56 on disc 52. At the appropriate time, the switch pipe 32 is traversed from position "a" to position "b" thus directing the product across cutting zone Z 1 , where it is subdivided into a leading segment which continues through guide passageways 48 a , and a trailing section (in this case, the acceptable intermediate product length), which continues between the cutting zones Z 1 , Z 2 , and through guide passageway 48b between the cropping shear discs 52, 54 to other material handling equipment, typically a pinch roll unit preceding a laying head (not shown). The cutting sequence is sequentially depicted diagrammatically in Figures 10A to 10D. Figure 10A shows the blades 24, 28 approaching the cutting zone Z 1 . The product front end passing through trough passageway 48a begins to traverse across the cutting zone Z 1 and while being lifted above plane P H as it rides up shoulder 29. Figure 10B shows the product severed into leading and trailing segments by the blades, 24,28. The leader blade 28 has preceded the follower blade 24 into the cutting zone and has begun to lift the tail end of the leading segment away from the front end of the trailing segment. Figure 10C shows the blades 24, 28 in their condition of maximum radial overlap in the cutting zone Z 1 . The leader blade 28 continued to lift the tail end of the leading segment away from the plane P H . The follower blade 24 now serves to redirect the front end of the trailing segment back to plane P H while it contacts and begins to exert a lifting action on the tail end of the leading segment. In Figure 10D, the blades 24, 28 are moving out of the cutting zone. The trailing blade 24 continues to lift the tail end of the leading segment away from the front end of the trailing segment. The leader blade 28 is now out of contact with the product, and the front end of the trailing segment has passed beneath the ledge 46' of the trough wall 46 into the central guide passageway 48b. Tail End Crop As the product tail end approaches the shear, the guide pipe 32 of switch 30 will be shifted from position "b" to position "c". The product will be severed in cutting zone Z 2 , in the manner described above, with the leading segment continuing on through guide passageway 48b, and with the trailing segment being directed into trough passageway 48c for subdivision by the chopping blades 56 on disc 54. The path of the product as it is directed through the successive cutting zones Z 1 , Z 2 is diagrammatically shown in Figure 11. Positions "a", "b" and "c" coincide with the same settings of the guide pipe 32. During the interval between billet lengths of product being rolled, the switch pipe 32 is returned to position "a" in readiness for the next front and tail end cropping sequence. It will now be appreciated by those skilled in the art that the present invention provides a number of significant advantages not available with conventional prior art shears. To begin with, by rotating the leader blades 28 on a radius R L which is longer than the radius of rotation R F of the follower blades, for any given angular blade velocity V a the tangential speed V TL of the leader blades at any point of blade overlap will equal or preferably slightly exceed the tangential speed V TF of the follower blades. Thus, the extent of blade overlap in the cutting zone can be maximized without experiencing damaging contact between the blades. Maximizing blade overlap is important to effecting a clean cut of the product into leading and trailing segments. The difference in rotational radii R 1 , R L of the blades 24, 28 and the resulting maximum blade overlap is further beneficial in that during a cropping sequence, the tail end of the leading segment is lifted away from the front end of the trading segment, while allowing the front end of the trailing segment to continued in the horizontal plane P H beneath the downstream ledge 46' of the trough dividing wall. By lifting the tail end of the leading segment out of the path of the advancing front end of the trailing segment, troublesome contact between to two is avoided. This is accomplished with minimal deflection of the front end of the trailing segment, which is important to the avoidance of cobbles, particularly when cropping products moving at speeds on the order of 100/120 m/sec. and higher. A further advantage stems from employing two sets of cutting blades in a side-by-side relationship to provide two cutting zones Z 1 , Z 2 one for cropping front ends and the other for cropping tail ends. Since only one set of blades operates in each cutting zone, more time is available for effecting product traverse across each cutting zone. Those skilled in the art will appreciate that various changes and modifications may be made to the above described shear without departing from the invention which is described by the appended claims. For example, other mechanically equivalent mechanisms may be employed to adjust the switch pipe to its different settings. The orientation of the follower and leader blades 24, 28 and the associated guide trough 44 can be turned 180°. Different blade designs may be employed.

Claims: A shear (10) for subdividing an elongated product (R) moving longitudinally in a plane (P H ), said shear comprising: leader and follower blades (28,24) mounted for rotation about parallel axes located on opposite sides of said plane, said blades being arranged to coact in a radially overlapping relationship at a cutting zone (Z 1 ) located between said axes and spaced vertically from said plane, the radius of rotation (R L ) of said leader blade being longer than the radius of rotation (R F ) of said follower blade; means for continuously rotating said blades at equal angular velocities, with said leader blade preceding said follower blade in said cutting zone; and switch means (30) located upstream of said cutting zone, said switch means being operable in a first mode to direct said product along a path bypassing said cutting zone, and being operable in a second mode to divert said product from said path into said cutting zone for cutting by said blades into leading and trailing segments, characterised by said blades being configured and arranged to deflect the tail end of said leading segment away from said plane while directing the front end of said trailing segment toward said plane. The shear as claimed in claim 1 wherein said plane is substantially horizontal, and the rotational axes of said leader and follower blades are respectively located below and above said plane. The shear as claimed in claim 2 further comprising a stationary receiving trough (44) having first and second channels (48a,48b) separated by an intermediate wall (46), said channels being positioned respectively to receive said leading and trailing segments. The shear as claimed in claim 3 wherein said intermediate wall includes a horizontal ledge (46) located above said horizontal plane. The shear as claimed in claim 1 wherein first and second sets of said upper and lower continuously rotating blades (28, 24) respectively coact in radially overlapping relationships at first and second laterally disposed cutting zones (Z 1 , Z 2 ) located above said plane; and wherein said switch means (30) operates sequentially: (i) to direct said product along a first path by passing said cutting zones; (ii) to divert said product from said first path into said first cutting zone for cutting the blades of said first set into a leading segment continuing along said first path and intermediate segment continuing along a second path; and (iii) to divert said product from said second path into said second cutting zone for cutting the blades of said second set to separate said intermediate segment continuing along said second path from a trailing segment continuing along a third path. The shear as claimed in claim 5 further comprising a stationary receiving trough (44) located downstream of said cutting zones, said receiving trough being subdivided into first, second and third channels (48a, 48b, 48c) by intermediate walls (46), said first and third channels being positioned respectively to receive said leading and trailing segments, and said second channel being positioned to receive said intermediate segment. The shear as claimed in claim 6 wherein said intermediate walls include horizontal ledges (46') located above said horizontal plane. The shear as claimed in claim 1 wherein said leader and follower blades are mounted respectively on rotors (25, 21), and wherein said switch means operates in said second mode in concert with said rotor (25).

Inventors: SHEN XIAOLAN, SHORE T MICHAEL, SHEN, XIAOLAN, SHORE, T. MICHAEL
Applicants: MORGAN CONSTRUCTION CO, MORGAN CONSTRUCTION COMPANY
Application year: 2000
Main classification: B23D25
IPC codes: B23D25, B23D33, B21B15, B26D3