Zamo', Giampietro (Via Bariglaria, 382 Udine, I-33100, IT)
De Luca, Andrea (Via Malignani, 13/6 Remanzacco, I-33047, IT)
| 1. | Continuously rotating shears for shearing to size a rolled product (16) continuously advancing at a set speed of advance (Vl), comprising two drums (12,13) rotating on parallel axes, at least a shearing blade (14a, 15a or 14b, 15b) mounted on each of said drums (12,13), drive means (21) to take said drums (12,13) into counter. rotating rotation and circuit means (22) to control said drive means (21), the shears being characterised in that said circuit means (22) are suitable to control said drive means (21) so as to impress on said drums (12,13) an angular velocity (Va) such that, at least around the moment of shearing, the peripheral velocity (Vp) of said blades (14a, 15a or 14b, 15b) is greater than said speed of advance (Vl) of said rolled stock (16) and that in the time interval (Te) between one shearing operation and another of said rolled stock (16) said circuit means (22) are suitable to feed said drive means (21) in a pendular manner, with at least a deceleration step and an acceleration step according to the pendular velocity (Vm), so as to take a pair of said shearing blades (14a, 15a or 14b, 15b) to a shearing point exactly after the passage of the desired length of the rolled stock (16) to be sheared. |
| 2. | Shears as in Claim 1, characterised in that said circuit means (22) comprise a processor (23) connected to a first transducer (26) suitable to monitor said speed of advance (Vl), said processor (23) being suitable to determine both said time (Te) and said angular velocity (Va) and said pendular velocity (Vm) according to said speed of advance (Vl) and the actual length (Le) to which said rolled stock (16) is to be sheared. |
| 3. | Shears as in Claim 2, characterised in that said drive means comprise an electric motor (21) and said circuit means (22) to achieve said pendular feed of said motor (21) are suitable to decelerate and accelerate said motor (21) for deceleration times (T2) and respectively acceleration times (T4) calculated by said processor (23) as fractions of said interval of time (Te) between one shearing operation and another of said rolled stock (16). |
| 4. | Shears as in Claim 3, characterised in that said deceleration times (T2) and acceleration times (T4) are equal. |
| 5. | Shears as in Claim 3, characterised in that said circuit means (22) are suitable to maintain said motor (21) at an angular velocity (Va) substantially constant for a time (T1) preceding said deceleration time (T2) and for a time (T5) subsequent to said acceleration time (T4), calculated by said processor (23) as fractions of said interval of time (Te) between one shearing operation and another of said rolled stock (16). |
| 6. | Shears as in Claim 3, characterised in that said circuit means (22) are suitable to maintain said motor (21) at said pendular velocity (Vm) for a brief time (T3) and that said pendular velocity (Vm) and said brief time (T3) are suitable to be calculated by said processor (23). |
| 7. | Shears as in Claim 2, wherein each of said drums (12, 13) supports at least two shearing blades (14a, 14b and 15a, 15b) angularly distanced from each other by a set pitch (p), characterised in that said processor (23) is suitable to calculate the number (Np) of pitches (p) which said drums (12,13) must perform in that period of time (Te) between one shearing operation and another of said rolled stock (16), according to said speed of advance (Vl) of said rolled stock (16) and the actual length (Le) to which said rolled stock (16) must be sheared. |
| 8. | Shears as in Claim 7, characterised in that said processor (23) is suitable to calculate the difference (Ld) between said actual length (Le) and the length (Lp) which can be obtained with said number (Np) of pitches (p) nearest said actual length (Le). |
| 9. | Shears as in Claim 8, characterised in that said processor (23) is suitable to determine an additional number (Na) of said pitches (p) associated with the set superspeed, or the difference between the peripheral speed of rotation of the drums (12,13) and the speed of advance (Vl) of the rolled stock (16). |
| 10. | Shears as in Claim 9, characterised in that said processor (23) is suitable to determine the value of said pendular velocity (Vm) according to the total number (Nt = Np + Na) of said pitches (p) to follow and according to said difference (Ld). |
| 11. | Shears as in Claim 10, characterised in that said processor (23) is suitable to determine the value of said pendular velocity (Vm), maximum and minimum, according to the pre. set tolerance of said actual length (Le). |
| 12. | Method to shear to size, by means of a continuously rotating shears (10), a rolled product (16) continuously advancing at a set high speed (Vl), wherein said shears (10) comprises two drums (12,13) rotating on parallel axes, at least a shearing blade (14a, 15a or 14b, 15b) mounted on each of said drums (12,13), drive means (21) to take said drums (12,13) into counter. rotating rotation and circuit means (22) to control said drive means (21), the method being characterised in that said circuit means (22) control said drive means (21) so as to impress on said drums (12, 13) an angular velocity (Va) such that, at least around the moment of shearing, the peripheral velocity (Vp) of said blades (14a, 15a or 14b, 15b) is greater than said speed of advance (Vl) of said rolled stock (16) and that in the time interval (Te) between one shearing operation and another of said rolled stock (16) said circuit means (22) feed said drive means (21) in a pendular manner, with at least a deceleration step and an acceleration step according to the pendular velocity (Vm), so as to take a pair of said shearing blades (14a, 15a or 14b, 15b) to a shearing point exactly after the passage of the desired length of the rolled stock (16) to be sheared. |
| 13. | Method as in Claim 12, characterised in that a first transducer (26) monitors said speed of advance (Vl) and a processor (23) connected to said first transducer (26) determines said time (Te) and said pendular velocity (Vm) and said angular velocity (Va) according to said speed of advance (Vl) and the actual length (Le) to which said rolled stock (16) must be sheared. |
| 14. | Method as in Claim 13, characterised in that said drive means comprise an electric motor (21) and that said circuit means (22) in order to achieve said pendular feed to said motor (21) decelerate and accelerate said motor (21) for deceleration times (T2) and respective acceleration times (T4) calculated by said processor (23) as a fraction of said interval of time (Te) between one shearing operation and another of said rolled stock (16). |
| 15. | Method as in Claim 14, characterised in that said times of acceleration (T2) and deceleration (T4) are equal. |
| 16. | Method as in Claim 13, characterised in that said circuit means (22) maintain said motor (21) at an angular velocity (Va) substantially constant for a time (T1) preceding said deceleration time (T2) and for a time (T5) subsequent to said acceleration time (T4), calculated by said processor (23) as fractions of said interval of time (Te) between one shearing operation and another of said rolled stock (16). |
| 17. | Method as in Claim 13, characterised in that said circuit means (22) maintain said motor (21) at said pendular velocity (Vm) for a brief time (T3) and that said pendular velocity (Vm) and said brief time (T3) are suitable to be calculated by said processor (23). |
| 18. | Method as in Claim 13, wherein each of said drums (12, 13) supports at least two shearing blades (14a, 14b and 15a, 15b) angularly distanced from each other by a set pitch (p), characterised in that said processor (23) calculates the number of pitches (p) which said drums (12,13) must perform in that period of time (Te) between one shearing operation and another of said rolled stock (16), according to the actual length (Le) to which said rolled stock (16) must be sheared and according to the peripheral velocity (Vp) of said shearing blades (14a, 14b and 15a, 15b). |
| 19. | Method as in Claim 18, characterised in that said pendular velocity (Vm) can be more or less than said angular velocity (Va), according to the number of pitches (p). |
| 20. | Method as in Claim 12, characterised in that said angular velocity (Va) is such that said peripheral velocity (Vp) of said shearing blades (14a, 14b and 15a, 15b) is equal to said high speed of advance (Vl) plus a set superspeed and that said superspeed can be set irrespective of said high speed of advance (Vl) and the actual length (Le) to which said rolled stock (16) must be sheared. |
| 21. | Method as in claim 12, characterised in that said pendular velocity (Vm) is verified with every shearing operation of said rolled stock (16) so as to keep each shearing operation within a pre. set tolerance. |
To be more exact, the invention concerns a flying shears, wherein the blade-bearing drums are made to rotate continuously, in opposite directions, so as to shear to size, to the desired length, rolled stock of a thickness or diameter of around 6'-10 mm or more, travelling at very high speeds, in the region of 45-50 metres per second and more.
The shearing method provides that, in the time interval between one shearing operation and the next, the speed of rotation of the blade-bearing drums is controlled and determined by a processor which, irrespective of the pre-set nominal reference velocity (shearing velocity), manages their pendular oscillation-being taken to mean acceleration and deceleration and/or deceleration and acceleration-so that the blades shear the rolled stock exactly to the desired length.
BACKGROUND OF THE INVENTION The state of the art includes various shears employed in the metallurgical field to shear to size products emerging from the rolling train.
Among the shears known in the state of the art, the so- called flying shears, using counter-rotating blades mounted on blade-bearing drums, have proved themselves to be the most suitable, also for the shearing of rolled stock travelling at high velocity.
These flying shears comprise a counter-positioned pair of counter-rotating drums, on the circumference of each of
which there is mounted an equal number of shearing blades, at an equal angular distance from each other.
Upstream of the blade-bearing drums there is a switching device suitable to convey the rolled stock longitudinally; it is movable on a horizontal plane to take the rolled stock from an inactive position, adjacent to the rotating blades, to a shearing position, between the counter-rotating blades, exactly at the desired moment of shearing.
The lateral displacement velocity of the switching devices is correlated to the circumferential position and the speed of rotation of the drums, so that the moment at which the rolled stock passes between the blades coincides with the desired shearing position of the blades.
The drums are normally made to rotate continuously at a pre-set constant angular velocity, such that the peripheral or tangential velocity of the shearing blades is greater than the speed of advance of the rolled stock which is to be sheared.
The peripheral velocity of the blades is pre-set according to the speed of advance of the rolled stock, the desired length to which the rolled stock is to be sheared and the pitch between the shearing blades. The peripheral velocity of the blades, moreover, must be pre-set so that, with a finite number of rotation pitches of the blade-bearing drums, it is possible to obtain a plurality of consecutive cuts of the desired length.
However, this leads to high tolerances in the length of the product to be sheared, mainly for the following reasons: there is an inevitable slow-down which the drums are subject to, due to the impact of the blades with the rolled stock while the latter is being sheared; the velocity of rotation of the blades is subordinated to the actual length to which the rolled stock is to be sheared to size; the possibility
of adjusting the velocity of the blades according to the characteristics of the rolled stock is limited.
These are serious problems for those businessmen operating in this field, especially for very high rolling speeds, for example in the range of 45-50 metres per second and more.
BE-A-630.233 describes a flying shears with counter- rotating drums to shear and measure rolled products.
This document teaches to regulate the peripheral speed of the blades so that this speed is equal to the speed of advance of the rolled stock around the shearing operation; the document does not teach, however, to regulate the speed of the drums in the interval between two successive shearing operations so that, after a whole number of pitches, the blades are in a position for shearing a pre-set length of the rolled stock.
FR-A-2.333.604 describes a shears with counter-rotating drums, wherein there are cam means to displace at least one of the drums from a position distanced from the other drum to a position close to the other drum, wherein the respective shearing elements are in a position of cooperation in order to perform the shearing operation.
The present Applicant has designed and embodied this invention to overcome the shortcomings of shears which are known to the state of the art, to improve shearing precision and to obtain further advantages as will be shown hereafter.
SUMMARY OF THE INVENTION The continuously rotating shears for shearing to size rolled stock and the relative shearing method according to the invention are set forth and characterised in the respective main claims, while the dependent claims describe other characteristics of the main embodiment.
The purpose of the invention is to achieve a flying shears which will allow to obtain precise shearing operations of
the rolled stock which passes through at high velocity, for example emerging from a finishing train.
In accordance with this purpose, the shears according to the invention provides that the velocity of rotation of the drums and hence the peripheral velocity of the blades is regulated with every shearing cycle in a manner which is to a certain extent independent of the actual speed of advance of the rolled stock and the actual length of the shearing to size.
In order to obtain this result, the electric motor associated with the drums is continuously controlled and governed by a control circuit comprising an electronic processor able to calculate the optimum velocity of the motor between one shearing operation and the next, to take the shearing blades, after a pre-set whole number of pitches, to shear the rolled stock at the desired point, to the desired length and within the pre-set tolerance.
According to one characteristic of the invention, the motor associated with the blade-bearing drums, between one shearing operation and the next, is made to oscillate, that is to say, it is decelerated or accelerated with respect to a nominal reference velocity of rotation (shearing velocity) and then accelerated or decelerated until it again reaches the nominal reference velocity of rotation, in order to annul any possible difference (either ahead or delayed) of the rotary blades with respect to the exact moment of shearing the rolled stock.
It is therefore within the spirit of this invention to calculate the whole number of rotation pitches of the drums which correspond to the measurement closest to the length of shearing required and, according to the nominal reference velocity, to define the pendular velocity of the motor in such a manner as to recover the missing length of the rolled
stock, whether it be more or less, with respect to the desired shearing length. The nominal reference velocity, that is to say, the shearing velocity, is equal to the speed of advance of the rolled stock plus the extra speed.
Therefore, according to the invention, with every shearing operation to be carried out, the pendular velocity of the blade-bearing drums, or the deceleration and acceleration curves, is rephased according to the nominal shearing length to be obtained and the actual speed of advance of the rolled stock, while the nominal reference velocity of the blade- bearing drums remains unchanged.
The invention provides a shears with two drums, facing each other and in continuous counter-rotation, equipped with specific blades for shearing to size and possibly other blades, located adjacent to the first, in order to scrap the leading and trailing ends of the rolled stock.
It is possible to mount on the same drums other blades, arranged adjacent to the scrapping blades, to cut segments of the rolled stock to be used as samples.
According to the invention, next to the shearing to size blades, to separate them from the scrapping blades, there are two spaces without blades which serve for the rolled stock to pass through both on the right and on the left of the shearing to size blades during the step wherein the usable portion of rolled stock is passing through.
BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the invention will become clear from the following description of a preferred form of embodiment, given as a non-restrictive example, with the aid of the attached drawings wherein: Fig. 1 is a view from above, in diagram form, of a shears according to the invention; Fig. 2 is a partial and enlarged view from A to A of Fig. 1;
Fig. 3 is a graph showing the development of the angular velocity of the motor of the shears shown in Fig. 1; and Fig. 4 is a graph showing the development of the torque of the motor of the shears shown in Fig. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT With reference to the attached Figures, a shears 10 according to the invention comprises a vertical frame 11 on which two rotating shearing drums 12 and 13 are mounted, arranged with their axes of rotation horizontal and parallel.
On the central zone of each drum 12 and 13 two blades 14a, 14b and respectively 15a, 15b (Fig. 2) are mounted lengthwise and on diametrically opposite sides. The latter are suitable to shear to size rolled stock 16 emerging from a finishing train 17 (Fig. 1) of a hot rolling mill, located upstream of the shears 10. The rolled stock 16 can be for example a bar, a rod or similar.
Near the lateral edges of the drums 12 and 13, four blades 18 and respectively 19 (Fig. 2) can also be mounted to scrap the segments of the leading and trailing ends of the rolled stock 16.
There are empty spaces 20 both on the left and on the right of the blades 14a, 15a and 14b, 15b so that the rolled stock 16 can pass through during the step when the usable part of the rolled stock 16 is passing.
The drums 12 and 13 are counter-rotating, so that with every rotation through 180° the blades 14a, 15a and 14b, 15b are in the shearing position shown in Fig. 2.
The drums 12 and 13 are made to rotate on command from a single electric motor 21, the shaft of which is connected to the drums 12 and 13 by means of a reduction gear, of a known type, arranged inside the frame 11 and which is not shown in
the drawings.
The motor 21 is controlled by an electric circuit 22, which comprises an electronic processor 23 and a command console 24.
A first transducer 26 is mounted in correspondence with a guide 28 to guide the rolled stock 16 to monitor the actual speed of advance Vl thereof, a second transducer 27a is mounted inside the frame 11 to monitor the angular position of the shearing blades 14a, 15a and 14b, 15b, and a third transducer 27b is assembled on the motor 21 to monitor the angular velocity Va of the drums 12 and 13.
The transducers 26,27a and 27b are suitable to send corresponding electric, analogic or digital signals to the processor 23.
A single-channel switching device 30 is arranged upstream of the shears 10 and is suitable to oscillate on a horizontal plane to guide the rolled stock 16 towards the shearing to size blades 14a, 15a and 14b, 15b, towards the scrapping blades 18 and 19, if included, and towards the empty spaces 20 next to the blades 14a, 15a and 14b, 15b.
An actuator 31, controlled by the processor 23, is suitable to command the displacement of the switching device 30. A fourth transducer 32 is assembled on the actuator 31 to monitor the position of the switching device and to send a corresponding electric, analogic or digital signal to the processor 23.
Downstream of the shears 10 there is a central guide channel 33 and two lateral guide channels 34, to guide the rolled stock 16 towards other processing stations of the rolling mill, of a known type and not shown in the drawings and, respectively, any possible scrapped segments towards containers, which are also of a known type and are not shown in the drawings.
In the example shown here, the diameter of the shearing to size blades 14a, 14b, and respectively 15a, 15b is 605 mm, and therefore the pitch"p"between the two blades of the same drum 12 and 13, which in this case corresponds to half the circumference, is equal to 950.33 mm. It is obvious that there may be more than two shearing to size blades for each drum 12 and 13, advantageously a multiple of two, in which case the pitch"p"will be proportionately reduced.
Normally the rolled stock 16 is sheared to form bars of a set nominal length Ln, for example 60m (60,000 mm).
Considering that the rolled stock 16 leaves the finishing train 17 at a temperature of about 850° and to take into account that the rolled stock 16 will contract in the cooling bed, downstream of the shears 10, the actual length Le of the bar to be sheared is increased by about one per cent, and therefore Le is around 60600 mm.
The speed of advance Vl of the rolled stock 16 in modern rolling plants is in the region of 45 metres per second, therefore the transit time Te=Le/Vl of the length Le is 1.347 secs.
So as not to slow down the advance of the rolled stock 16 during the shearing operation, the drums 12 and 13 are made to rotate at an angular velocity Va such that the peripheral velocity Vp of the blades 14a, 14b, 15a and 15b is more than the rolling velocity Vl, at least during the shearing steps.
The angular velocity Va is pre-set irrespective of the actual length Le and of the shearing to size tolerance.
Moreover, so that the blades 14a and 15a alternate with the blades 14b and 15b in shearing the rolled stock 16, the shearing must take place after an odd number of pitches"p".
It is also indispensable that the rolled stock 16 should be sheared to the set length Le after a whole number of pitches"p".
If the drums 12 and 13 rotated at a constant velocity, such that the peripheral velocity Vp were equal to the rolling velocity Vl, it would be possible to obtain only cuts with a length equal to whole multiples of the pitch <BR> <BR> <BR> <BR> <BR> p<BR> "p".
According to one characteristic of the invention, the peripheral velocity Vp of the blades 14a, 14b, 15a and 15b is calculated by the processor 23 so as to keep it equal to the reference nominal velocity a little before and a little after the shearing operation, and so that it is such as to take one pair of blades 14a-15a, or 14b-15b to the shearing point exactly when the point of the rolled stock 16 which has to be sheared to the desired length is passing.
Thus, for example, to obtain a length Le of 60600 mm, by keeping the drums rotating at a velocity of Vp=Vl, 63 pitches would not be enough, while 65 pitches would be too many.
It is the processor 23 which, according to the value of the length Le, which can be set by means of the console 24 or programmed and memorised in an internal memory, calculates the number (Np) of pitches"p"to be made between one shearing operation and the next, or in the time Te, and also the value of the velocity of the motor 21 and hence of the drums 12 and 13, taking into account the actual value of the velocity Vl at which the rolled stock 16 advances, as monitored by the transducer 26.
In other words, given that at the moment when shearing is carried out, the speed of rotation of the drums 12 and 13 must be closely correlated to the velocity Vl, the processor 23 calculates the development of the deceleration/ acceleration curves of the drums 12,13 in the interval between two successive shearing operations so that the number of pitches made by the drums 12,13 substantially
corresponds to the length of the rolled stock 16 to be sheared.
The processor 23 also determines the value of the length nearest (Lp = p x Np) the length Le and calculates the value of the difference Ld, positive or negative, between Le and Lp.
The processor 23 is also suitable to calculate an additional number Na of pitches"p"to be associated with the superspeed set, or the difference between the peripheral speed of rotation of the drums 12,13 and the speed of advance of the rolled stock 16, and therefore the actual or total number Nt of pitches"p"will be given by the sum of Np and Na.
According to one characteristic of the invention, the period of time Te is divided into five periods T1-T5 (Fig.
3) during which the processor 23 performs the following operations: In the period of time T1, corresponding in this case to about 0.37 secs, the motor 21 is made to rotate at a constant angular velocity Va, for example 813 rpm, which, given the transmission ratio between the drive shaft and the drums 12 and 13, corresponds to an angular velocity Va of the latter of 167.95 rad/secs.
During this period T1, the processor 23 processes the data of the velocity Vl and the length Le and determines by how much, if at all, to slow down and/or accelerate the motor 21 and the drums 12 and 13 so that the shearing to size blades 14a-15a or 14b-15b are at the shearing point exactly when the rolled stock 16 has covered the length Le.
In the period of time T2, corresponding to about 0.25 secs, the motor 21 is made to decelerate until it reaches a pendular velocity Vm, for example 770 rpm, calculated by the processor 23. The value of the pendular velocity Vm will be
between a minimum and a maximum, according to the tolerance set by the actual length Le.
The pendular velocity Vm can be greater or smaller than the angular velocity Va, according to the number Nt of pitches"p". Or, if a positive difference Ld (Lp is greater than Le) corresponds to a set angular velocity Va, the pendular velocity Vm will be less than the angular velocity Va, while if a negative difference Ld (Lp is less than Le) corresponds to a set angular velocity Va, the pendular velocity Vm will be greater than the angular velocity Va.
The condition of Vm greater or less than Va is defined by the processor 23 with an opportune choice of Ld (the processor 23 will tend to always choose the value of Ld = less).
For time T3, which corresponds to 0.1 sec., the motor 21 is kept at the pendular velocity Vm and then, for the period of time T4, corresponding to about 0.25 secs, the motor is accelerated until it returns to the constant velocity Va.
For the remaining period of time T5, the motor 21 is kept at the nominal reference velocity, which coincides with the angular velocity Va, so that any possible oscillation in the velocity of the motor 21 will be mitigated and annulled.
In this way, we obtain a real programmed pendular oscillation of the motor 21; this pendular oscillation can occur with every shearing cycle of the rolled stock 16, so that with every shearing operation the length Le will actually be the set length.
As can be seen in the graph in Fig. 4, during the periods T1-T5 the torque applied to the motor 21 varies according to the individual steps of constant velocity, acceleration and deceleration.
In the example shown here, the motor torque is 453 Nm for time T1, it goes down to-1481 Nm during the deceleration
step (T2), it goes up again to 453 Nm in time T3, rises to 2387 Nm for time T4 and returns to 453 for time T5.
It is clear that the numerical values expressed here have been given only as an example; they are purely indicative and are not restrictive.
It is obvious that modifications and additions can be made to the shears 10 described heretofore, but these will remain within the spirit and scope of the invention.
For example, instead of a pair of shearing to size blades for each drum 12,13, a single blade 14a, respectively 15a could be provided.
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