WO2001096038A1

WO2001096038A1 - Rectilinear, non-slip wiredrawing machine

Info

Publication number: WO2001096038A1
Application number: PCT/IT2001/000310
Authority: WO
Inventors: Giulio Lisciani
Original assignee: R Lisciani Trafilerie Srl
Current assignee: R Lisciani Trafilerie Srl
Priority date: 2000-06-16
Filing date: 2001-06-15
Publication date: 2001-12-20
Anticipated expiration: 2002-12-16
Also published as: ITRN20000027A1; AU2001270983A1

Abstract

A rectilinear, non-slip, wiredrawing machine for metal wires (2) comprises dies (3); motorized capstans (4) able to receive and supply the wire (2) with tangential winding and unwinding, said capstans comprising two separate concentric and coaxial parts (5, 6), i.e. a first part (5), moved by an associated actuating motor (7), being provided with a zone (8) for pulling the wire (2), and a second part (6) comprising a rotating ring incorporating an output zone (9) where the wire (2) leaves the capstan (4), being pulled by a following capstan (4); and means (10) for synchronizing the movement of the capstans (4). Oscillating drive means (12; 16, 20) located in between and connecting directly the first part (5) and second part (6) of each capstan (4) are provided so as to allow a limited relative angular displacement thereof subject to a counter-pull torque exerted via control of the means (10) for synchronization of the movement of the capstans (4).

Description

RECTILINEAR, NON-SLIP WIREDRAWING MACHINE

Description Technical field

The present invention relates to the drawing of semifinished metallurgical products for the production of metal wire and relates in particular to a rectilinear, non-slip, wiredrawing machine with consecutive capstans which are arranged in-line and between which dies are located in an ordered manner. The wire is unwound tangentially from each capstan and passes from one capstan to the other, passing through the dies where it undergoes a gradual reduction in cross-section and simultaneous elongation. Background art As regards the drawing of metal wire, in accordance with the methods described above, the document IT 01238280 in the name of the same Applicant discloses a wiredrawing machine in which each of the various capstans is formed as two separate concentric and coaxial parts which are independently supported by the structure of the machine. A first part, incorporating a zone for pulling the wire reaching the capstan, is forced to rotate by a motor for actuating the said capstan. The second part, which is realised as an idle and freely rotating ring and which incorporates in turn an output zone where the wire leaves the capstan, is instead made to rotate by the pulling force which is exerted on the wire by the following capstan or the associated pulling zone. A synchronization device controls the direct transmission of the wire between one capstan and the next, operating the actuating motor of each capstan so as to adjust the speed of rotation of the first part of the capstan, correcting it depending on the difference between the angular displacements detected at each instant between the first and the second part of the said capstan.

Braking means connected to the second part of the capstan react to the active torque - or the so-called "pull torque" which is correlated to the pulling force produced by the capstan located after the one in question - opposing it with its own braking torque, or so-called "counter-pull torque" which, in combination with the active torque, ensures that the turns of the wire on the rotating ring are always kept close together.

The wiredrawing machines of the known type described above have proved to satisfy fully the objects for which they were designed. However, the maximum value of the counter-pull torques constitutes for these machines, as moreover for all wiredrawing machines of the known type, a critical parameter from many points of view, i.e. design, plant engineering and cost. On the other hand, in certain operating conditions, it is desirable to have a fairly large counter-pull torque: for example, for the drawing of iron and steel semifinished products which have a high percentage of carbon in their chemical composition; or for the drawing of large-diameter wires; or also for the high-speed drawing of small-diameter wires where, however, a high counter-pull torque ensures stabilisation of the wound wire leaving the various capstans . From a constructional point of view, independently of the constructional design of a generic wiredrawing machine, a counter-pull torque of suitable intensity may be generated using dissipative braking means or regenerative braking means. Dissipative braking, however, involves high energy consumption, problems of heat disposal and the need for dedicated cooling systems.

Regenerative braking, if provided by means of a direct-current motor operating as a generator able to recover the braking power and reintroduce into the system as electrical power, would overcome these drawbacks, but would involve considerable constructional complications and high costs.

In the specific case of a wiredrawing machine of the type described in the already mentioned document IT 01238280, in addition to the drawbacks of a general nature associated with the braking means, there are also further drawbacks associated with the fact that the two characteristic parts of each capstan are connected to one end of two coaxial shafts, the opposite ends of which are connected to two encoders which are able to detect the relative angular phase- difference between said capstan parts and which are operationally interconnected with means for synchronization of the associated actuating motors.

In fact, the application of a high counter-pull torque, applied torsionally to a long and slender shaft and moreover applied to the inner shaft of the two coaxial shafts - i.e. the shaft which is connected to the freely rotating ring of the capstan - implies the need for an inner shaft with a large diameter; consequently, the outer shaft, which contains the said inner shaft, must be designed with correspondingly larger dimensions: as a result the location of suitable supports is problematic and costly and generally results in larger dimensions of the whole wiredrawing machine.

Despite these constructional drawbacks, such a wiredrawing machine still offers numerous and undeniable advantages such that the problem of overcoming these drawbacks has become a pressing requirement in the sector.

It is also necessary to point out that the freely rotating part of the capstan, which constitutes one of the fundamental preconditions for synchronization control, gives rise to certain problems during insertion of the wire, for which a one-piece integral condition - albeit temporary - is required between the first and the second part of the generic capstan. Two different techniques have been adopted in order to deal with this problem: one consists in connecting manually the two parts using a pin and a matching seat which are suitably provided in the two parts of the capstan; the other one consists in using a friction clutch which is engaged and disengaged depending on the various operating conditions of the wiredrawing machine.

The pin/matching seat solution has proved to be simple and inexpensive to realise, but is not easy to manage on a practical level since the seat tends to become blocked fairly easily as a result of the lubricating powders used during the drawing process which is performed in notoriously dry conditions.

The use of the friction clutch allows the operations to be automated, but involves constructional complications and consequent further increased costs. Disclosure of the invention

The primary object of the present invention is to eliminate all the abovementioned drawbacks by means of a wiredrawing machine which is able to combine all the advantages of a rectilinear, non-slip, wiredrawing machine of the type described in the document IT 01238280, without having any of the associated limitations as regards the maximum counter-pull torque.

A second object is that of providing a regenerative braking system which is simple, effective and has an inexpensive constructional design. A further object is that of achieving highly reliable and totally automatic control of the wiredrawing machine also during the wire-insertion steps.

In accordance with the invention, these objects are achieved by a rectilinear, non-slip, wiredrawing machine for metal wires, comprising dies; consecutive motorized capstans arranged in an ordered manner between the dies and able to receive and supply the wire with tangential winding and unwinding, said capstans each comprising two separate concentric and coaxial parts, i.e. a first part, moved by an associated actuating motor, being provided with a zone for pulling the metal wire, and a second part comprising a rotating ring incorporating an output zone where the wire leaves said capstan, being pulled by a following capstan; and means for synchronization of the capstans, characterized in that it comprises oscillating drive means located in between and connecting directly the first part and second part of each capstan so as to allow a limited relative angular displacement thereof within a limited range of variation of said displacement and subject to a resistive torque of variable intensity exerted via control of the device for synchronization of the capstan speed.

Brief description of the drawings

The technical characteristics of the invention, in accordance with the abovementioned ob ects, may be clearly determined from the contents of the claims indicated below and the advantages thereof will emerge more clearly from the detailed description which follows, with reference to the accompanying drawings which show a purely exemplary and non-limiting embodiment thereof, in which: - Figure 1 is a schematic representation of a capstan used in the wiredrawing machine according to the invention;

- Figure 2 is top view of the capstan according to Figure 1; - Figure 3 is a schematic view of the structure of one of the said capstans with certain essential parts for formation of the speed synchronization means;

- Figure 4 is a view of the capstan according to Figure 3 sectioned along the line IV-IV;

Figure 5 is a diagram showing certain particular hydraulic devices used in conjunction with the invention;

- Figure 5a is a view illustrating an alternative example of embodiment of a detail of the invention;

-¹ Figure 6 shows a functional block diagram of the synchronism means with which the wiredrawing machine according to the invention is equipped;

- Figure 7 shows in schematic form a wiredrawing machine of the type in question. Detailed description of the preferred embodiment (s)

With reference to the accompanying drawings, 1 denotes in its entirety (Figure 7) a rectilinear, non- slip, wiredrawing machine for metal wires 2, essentially comprising dies 3 and consecutive capstans 4 which are arranged alternating with the dies 3 in an ordered manner and are individually motorized and are able to receive and supply the wire 2 with tangential winding and unwinding (Figure 2) , while the wire, passing simultaneously through the dies 3, undergoes - in manner which is well-known - a gradual reduction in cross-section and an elongation proportional to the latter.

The capstans 4 (Figures 1 and 3) each comprise two separate, concentric and coaxial parts 5,6. A first part 5, moved by an associated actuating motor 7, is provided with a zone 8 for pulling the metal wire 2. A second part 6 comprises, on the other hand, a rotating ring incorporating an output zone 9 where the file 2 leaves this capstan 4 and is instead pulled by a following capstan 4.

Means 10 for synchronizing the movement of the capstans 4 are provided in order to synchronize the speed of rotation of the capstans 4 so as to have, despite the geometric variations in the wire 2 , a constant flow of material which passes from one capstan 4 to the other.

The wiredrawing machine 1 also comprises, for each capstan 4, oscillating drive means 13; 16, 20 arranged in between and directly connecting the first part 5 and the second part 6 of each capstan 4.

These oscillating drive means 13; 16, 20, which are defined more fully in the remainder of the present description, are designed so as to allow a relative mobility, in the angular sense, between the first part 5 of a generic capstan 4, which, as mentioned, is directly motorized, and the second part 6 of the same capstan 4 which instead is able to rotate with respect to the first part since - as described in the document IT 01238280 which forms an integral part of the present description and to the text of which reference may be made - its movement is dependent upon the driving action imparted to it by the following capstan 4. The relative angular displacement between the first part 5 and the second part 6 of the capstan 4 is nevertheless limited within a range of variation which is fairly small, roughly in the region of a few degrees of amplitude. The angular displacement is also subject to a counter-pull torque of variable intensity which is exerted on the wire 2 via control of the means 10 for synchronization of the movement of the following capstans 4, said means detecting in an instantaneous manner the operating speeds of a pair of consecutive capstans and managing the associated motor systems, driving on the basis of the error detected - in a kind of "master/slave" relationship - the two parts 5,6 forming a same capstan 4.

The oscillating drive means incorporate means 13; 16 for actuating the counter-pull torque to be applied to the wire 2 being unwound from the capstan 4. These means for actuating the counter-pull torque include a hydraulic torque actuator 13 having its ends 14,15 connected in an active and reactive relationship to said first part 5 and second part 6 of the capstan 4.

The torque actuator 13 may be provided in many constructional forms. A first of these may consist in the use of a hydraulic piston 16 having a rod 17 and a cylinder 18 which are respectively connected to the first part 5 and to the second part 6 of each capstan 4 and mounted with an eccentric orientation with respect to an axis of rotation 19 common to this first part 5 and second part 6 of the capstan 4. A different constructional form of the torque actuator 13, shown in Figures 3 and 4, instead comprises two mutually counter-reacting pistons 16 located on either side of the axis 19 of rotation common to the first part 5 and second part 6 of the capstan 4.

It is necessary to emphasize the fact that the torque produced by the torque actuator 13, whatever the preferred embodiment of the latter, is not transmitted outside the capstan 4, but remains - owing to the active and reactive play between the parts joined together - all inside the capstan 4: this obviously means that each capstan 4 is intrinsically regenerative from an energy point of view.

The oscillating drive means also include first transducer means 20; 21, 22, 23 intended to exchange with the synchronization means 10 signals correlated to the relative angular position of the first part 5 and second part 6 of each capstan 4.

In particular, the first transducer means include (Figure 5) a hydraulic circuit - denoted in its entirety by 20 - comprising a power supply line 21 for each torque actuator 13 (see also Figure 3) ; and a hydraulic piston 22. The power supply line comprises a rotating hydraulic coupling 50 which disengages the movement of the capstan 4 from the fixed part of the circuit 20. The hydraulic piston 22 is provided with a pressing plunger 23 which acts on the incompressible - hydraulic fluid of said circuit 20 and which is provided with a rod 24 associated, in turn, with second means 2,7; 28a, 28b for transducing its position and with means 29 for actuating the hydraulic piston 22 itself.

The characteristics of incompressibility of the hydraulic fluid are used in order to transduce the position of the rod 17 with respect to the cylinder 18 and consequently the phase relationship of the second part 6 of the capstan 4 with respect to the first part 5.

The second transducer means may be applicable in structurally different, but functionally equivalent forms. A first example of embodiment of these means includes a potentiometer 27 interconnected with the synchronization means 10 and able to transduce the movements of the rod into proportional electric signals which are exchanged with the synchronization means 10.

Differently from this embodiment, the second transducer means may include (Figure 5a) an inductive sensor which is interfaced with the synchronization means 10 and which comprises a detector 28a and a facing frustoconical projection 28b integral with the rod 24.

As for the operating means, from Figure' 5 it can be seen that these are actuated by a pneumatic circuit 29 which operates a plunger 42 connected to the rod 24 and movable inside a closed chamber 43 into which i at a constant predetermined pressure is introduced, said air producing the resistive counter-pull torque: depending, therefore, on the air pressure, it will be possible to set the intensity of the desired counter- pull torque.

Consequently, the air contained in the chamber 43 also produces an elastic damping effect as a result of which the oscillating drive means are able to oscillate elastically about their equilibrium position.

The synchronization means 10, which are shown schematically in Figure 6, include a generic capstan Cn, a first comparator 30 for receiving feedback signals Vc and Vcn+1 which are respectively correlated to the speed of the first part 5 of the capstan Cn and the first part 5 of a following capstan Cn+1. The first comparator 30 compares the abovementioned signals and sends at its output a difference signal to the integration block 31 which emits at its output a current phase signal 32 for the capstans Cn and Cn+1_F Obviously, the integration block 31 shown in the diagram according to Figure 6 is a symbolic mathematical representation of a physical device which in reality is formed by the first part 5 and by the second part 6 of the capstan 4.

A second comparator 33 - for receiving the current phase signal 32 and a reference phase signal emitted by a block 35 which in turn receives a predefined reference signal Rifn for the capstan Cn - outputs a difference signal 36 to a block 37.

Finally, a third comparator 38 for receiving a signal emitted by the block 37 and the signal Rifn outputs a corrected reference signal 40 which is sent to the input of a device 41 for controlling the speed of the motor 7 of the generic capstan Cn and which is differentiated in order to determine a reference value Rifn-1 for a capstan Cn-1 preceding the capstan Cn. The device for controlling the speed of the motor 7 is represented in particular by a block 41 which identifies a conventional speed actuating system and which includes an amplifier 44 and a speedometer dynamo 45.

As a result of the synchronization means described above it is possible to manage speed control of the wiredrawing machine 1 in an optimum manner; moreover, when the wiredrawing machine is inactive, namely is at zero speed, they allow the first and the second part 5,6 of the capstan 4 to be automatically locked together so as to ensure easier and more reliable insertion of the wire 2.

Finally, the synchronization means 10 include electronic calculating means (not shown in that entirely conventional) able to input into the proportional integration block 37 a suitably calculated error signal to be used in the operating transient where the wiredrawing machine 1 passes from a condition in which the first part 5 and second part 6 of the capstan 4 are mutually locked together, to an operating condition at the rated speed in which said first part 4 and second part 6 are movable angularly and relatively via control of the oscillating drive means 13; 16, 20.

The abovementioned electronic means, consisting in particular of a PLC equipped with suitable software, are able to eliminate some of the drawbacks when the wiredrawing machine 1 is started up again. In fact, during re-starting of the wiredrawing machine 1, the torque converter 13, which is constantly supplied with the hydraulic fluid, tends to bring the parts 5, 6 of the capstan 4 into the condition of maximum possible relative angular displacement with respect to each other. This condition corresponds to the end-of-travel position reached by the cylinders 16; in this condition the synchronization means are unable to perform regulation. This drawback is therefore overcome by the electronic calculating means which provide the regulating system with resultant calculation information regarding the location of the theoretical reference point to which operation of the synchronization means should be referred. As the operating speed of the wiredrawing machine increases from the initial zero value to its rated value, the relative position of the first part 5 and second part 6 of the capstan 4 moves from the maximum angular displacement condition and increasingly approaches the central position in the regulation range.

It must be pointed out moreover that, as stated, the means 10 for synchronization of the wiredrawing machine 1 allow the relative position of the first part 5 and second part 6 of each capstan 4 to be correlated to a displacement of the rod 14 of the first transducer means by means of this incompressible hydraulic column and therefore, by means of the second transducer means, allow the generation of an output signal which can be electronically processed without the aid of other physical devices. This allows the electronic structure of the control means to be simplified considerably with further obvious advantageous implications in terms of reliability and plant costs .

The invention thus conceived may obviously be applied on an industrial level; moreover it may be subject to numerous modifications and variations all falling within the scope of the inventive idea. Furthermore, all the details may be replaced by technically equivalent elements.

Claims

1. Rectilinear non-slip wiredrawing machine for metal wires (2), comprising dies (3); consecutive motorized capstans (4) arranged in an ordered manner alternately with the dies (3) and able to receive and supply the wire (2) with tangential winding and unwinding, said capstans (4) each comprising two separate concentric and coaxial parts (5,6), i.e. a first part (5) , moved by an associated actuating motor (7), being provided with a zone (8) for pulling the metal wire (2), and a second part (6) comprising a rotating ring incorporating an output zone (9) where the wire (2) leaves said capstan (4), being pulled by a following capstan (4); and means (10) for synchronization of the movement of the capstans (4) , characterized in that it comprises oscillating drive means (13; 16, 20) located in between and connecting directly said first part (5) and second part (6) of each capstan (4) so as to allow a limited relative angular displacement thereof within a limited range of variation of said displacement itself and subject to a counter-pull torque of variable intensity exerted via control of the means (10) for synchronization of the movement of the capstans (4) .

2. Wiredrawing machine according to Claim 1, characterized in that said oscillating drive means incorporate means (13; 16) for actuating the counter- pull torque to be applied to the wire (2) being unwound from the capstan (4) .

3. Wiredrawing machine according to Claim 2, characterized in that said means for actuating the counter-pull torque incorporate at least one hydraulic torque actuator (13) having its ends (14,15) connected in an active and reactive relationship respectively to said first part (5) and second part (6) of the capstan (4).

4. Wiredrawing machine according to Claim 3, characterized in that said torque actuator (13) comprises at least one hydraulic piston (16) with a rod (17) and a cylinder (18) respectively connected to the first part (5) and to the second part (6) of said capstan (4), said piston (16) being mounted with an eccentric orientation with respect to an axis (19) of rotation common to said first part (5) and second part (6) of the capstan (4) .

5. Wiredrawing machine according to Claim 4, characterized in that said torque actuator (13) comprises two said pistons (16) mutually counter- reacting and located on either side of said common axis of rotation (19) .

6. Wiredrawing machine according to one of Claims 3 to 5, characterized in that said oscillating drive means include first transducer means

(20; 21, 22, 23) for exchanging with the synchronization means (10) signals correlated to the relative angular position of the first part (5) and the second part (6) of each said capstan (4) .

7. Wiredrawing machine according to Claim 6, characterized in that said first transducer means include a hydraulic circuit (20) comprising a power

Supply line (21) for said one or each torque actuator

(13); and a hydraulic piston (22), said hydraulic piston (22) being provided with a presser plunger (23) acting on the hydraulic fluid of said circuit (20) and being provided with a rod (24) associated with second means (27; 28a, 28b) for transducing its position and with means (29) for actuating the hydraulic piston

(22) .

8. Wiredrawing machine according to Claim 1 , characterized in that said hydraulic circuit (20) includes elastically yielding means (42,43) able to allow said torque actuator (13) to oscillate elastically about its equilibrium position.

9. Wiredrawing machine according to Claim 7, characterized in that said second transducer means include a potentiometer (27) interconnected with the synchronization means (10) and able to transduce the movements of the rod (24) into proportional electrical signals exchanged with said synchronization means (10) .

10. Wiredrawing machine according to Claim 7, characterized in that said second transducer means include an inductive sensor (28a, 28b) interfaced with the synchronization means (10) .

11. Wiredrawing machine according to Claim 7, characterized in that said actuating means include a pneumatic circuit actuating the movement of the rod

(24) and controlled by the synchronization means (10) .

12. Wiredrawing machine according to Claim 1, characterized in that the synchronization means (10) include, for a generic capstan (Cn) , a first comparator (30) for receiving feedback signals (Vc) and (Vcn+1) respectively correlated to the speed of the first part (5) of the capstan (Cn) and the first part (5) of a following capstan (Cn+1), said first comparator (30) comparing said signals and outputting a difference signal to an integration block (31) which emits at its output a current phase signal (32) for said capstans (Cn and Cn+1) ; a second comparator (33) for receiving said current phase signal (32) and a reference phase signal (34) emitted by a block (35) receiving, in turn, a predefined reference signal (Rifn) for a capstan (Cn) , outputting a difference signal (36) to a block (37) ; and a third comparator (38) for receiving a signal (39) emitted by the block (37) and the signal (Rifn) , outputting a corrected reference signal (40) which is sent to the input of a device (41) for controlling the speed of the motor (7) of the generic capstan (Cn) and which is differentiated in order to define a reference value (Rifn-1) for a capstan (Cn-1) preceding the capstan (Cn) .

13. Wiredrawing machine according to Claim 11, characterized in that said synchronization means (10) include electronic calculating means able to input into said block (37) a suitably calculated error signal to be used in the operating transient during which the wiredrawing machine (1) passes from a condition in which the first part (5) and the second part (6) of the capstan are mutually locked together into an operating condition at the rated speed where said first part (4) and second part (6) are angularly and relatively movable via control of the oscillating drive means (13;16,20) .

14. Wiredrawing machine according to the preceding claims and in accordance with that described and illustrated with reference to the figures of the accompanying drawings and for the objects mentioned.