Reel unwinding unit and corresponding stranding machine

Abstract

Unwinding unit (10) comprising a support structure (11) on which there are mounted both a reel (12), containing a wire (13) wound into coils, said reel (12) being rotatable around an axis of rotation (X) thereof as a consequence of the application of a traction force (T) on said wire (13), and also braking means (14) configured to apply a variable brake torque on said reel (12).

Description

[0001] “REEL UNWINDING UNIT AND CORRESPONDING STRANDING MACHINE”

[0002] FIELD OF THE INVENTION The present invention concerns a reel unwinding unit from which a metal wire, for example made of steel, is pulled with a certain traction force while the tension on the wire is kept constant regardless of the quantity of wire present on the reel, the diameter of the wire, the traction force applied or other anomalies.

[0003] These reel unwinding units are typically used in stranding machines, known to those skilled in the art as stranding machines or stranders, which are configured to receive a plurality of metal wires and transform them into strands intended as ropes, or cables, consisting of several wires interwoven together, possibly on a central core, which can consist of one of the wires. By way of example and without limitation, the strands can be used in the construction sectors in general or in the most diverse civil infrastructures.

[0004] BACKGROUND OF THE INVENTION

[0005] Stranding machines are known, which comprise a plurality of unwinding units, each of which has a support structure or cradle on which, using a variety of support systems such as shafts or hinges, a respective reel is rotatably mounted, containing a metal wire, wound in coils. The wire, unwound from each reel, is usually made to exit from the front part of the cradle through an eyelet commonly made of wearresistant material.

[0006] The machine also comprises a stranding unit configured to receive the wires and transform them into a strand. A drawing unit is positioned downstream of the stranding unit to exert the traction force necessary to unwind the wires and close the strand.

[0007] Each unwinding unit is also provided with a braking device the function of which is to adjust the tension of the wire unwound during the unwinding step, but also to interrupt the rotation of the reel as quickly as possible in the event of machine blockage or breakage of the wire.

[0008] In fact, the tension of the wire during unwinding is never constant essentially because the wire on the reel is wound randomly and because the tension on the wire necessary to rotate the reel is different when the reel is full or almost empty. If the initial braking force is adjusted for a full reel, the same braking force applied to a partially spent reel could cause unwanted stretching or breaking of the wire.

[0009] The braking devices of traditional unwinding units normally comprise a dancer roll which rests against the outermost coils of the reel to control, in a geometric and approximate manner, the quantity of wire still present on the reel.

[0010] The dancer roll is coupled with an adjustment brake which determines a braking action proportional to the quantity of wire still present on the reel.

[0011] These braking devices have the disadvantage that they are not able to compensate for irregularities due to how the wire is wound on the reel, to the diameter of the wire, to the type of material the wire is made of, which determines different elastic properties, as well as the acceleration and deceleration of the reel itself.

[0012] Therefore, excessive tension on the wire can still occur when the reel is accelerated, or an overfeed of wire during a deceleration or abrupt stoppage of the reel, as well as different tensions on the wires which can cause the formation of a strand with one or more slack wires.

[0013] Another disadvantage of the unwinding units currently on the market is due to their excessive length which directly impacts the overall bulk of the stranding machine, and is due to the fact that the distance between the axis of rotation of the reel and the eyelet through the which the wire exits from the cradle cannot be reduced below certain limits because in such cases the angle at which the wire enters the eyelet would be too steep and the wire could be damaged or break due to the excessive tension required to make it pass through the eyelet itself.

[0014] There is therefore a need to perfect a reel unwinding unit and corresponding stranding machine that can overcome at least one of the disadvantages of the state of the art.

[0015] To do this it is necessary to solve the technical problem of adjusting the tension on the unwinding wire in a particularly effective way, keeping it constant regardless of the quantity of wire present on the reel, the diameter of the wire, the traction force applied or other anomalies.

[0016] In particular, one purpose of the present invention is to create an unwinding unit for a reel able to adjust the tension on the wire continuously and according to the portion of wire gradually being unwound. Another purpose of the present invention is to create a reel unwinding unit able to block the reel almost instantly in the event of wire breakages or sudden stoppage of the machine.

[0017] Another purpose of the present invention is to create an unwinding unit for a reel which, secondarily, is also able to direct the wire into the eyelet without imparting further tensions which could damage it.

[0018] Another purpose of the present invention is to create a reel unwinding unit which is particularly compact and therefore allows to obtain a stranding machine with a reduced longitudinal bulk compared to the machines on the market. The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

[0019] SUMMARY OF THE INVENTION

[0020] The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0021] In accordance with the above purposes and to solve the technical problem as above in a new and original way, also obtaining considerable advantages compared to the state of the prior art, an unwinding unit according to the present invention for unwinding a reel of wire, typically made of metal material , comprises a support structure on which are mounted both a reel containing the wire wound in coils, the reel being rotatable around its own axis of rotation as a consequence of the application of a traction force on the wire, and also braking means configured to apply a variable brake torque on the reel. In accordance with one aspect of the present invention, the unwinding unit comprises tensioning means configured to apply a certain tension on the unwinding wire exiting from the reel, and adjustment means associated both with the tensioning means and also with the braking means to continuously determine the variable brake torque which is a function of a position assumed by the tensioning means as a consequence of a pressure applied to the wire.

[0022] In accordance with another aspect of the present invention, the tensioning means comprise a first tensioning element attached to the support structure to receive the unwinding wire resting on it, and a second tensioning element pivoted to the support structure by means of arms which allow an angular travel thereof on a substantially vertical plane to determine a variable pressure on the wire as it unwinds.

[0023] In accordance with another aspect of the present invention, the first and second tensioning elements are distinct and independent first and second idle rolls, both being parallel to the axis of rotation and arranged vertically staggered with respect to each other.

[0024] In accordance with another aspect of the present invention, the first roll is pivoted on opposite lateral walls of the support structure and has an extension equal to the distance between them, while the second idle roll has an extension smaller than that of the first idle roll.

[0025] In accordance with another aspect of the present invention, the adjustment means comprise a pair of springs with opposing forces able to adjust the variable brake torque according to the position assumed by the tensioning means. In accordance with another aspect of the present invention, a first spring is connected to the support structure and to the braking means, and is pre-adjusted with a first force to determine a maximum brake torque. A second spring is connected to one of the arms and to the braking means, generating a second force opposed to the first force and variable according to the pressure exerted on the unwinding wire.

[0026] In accordance with another aspect of the present invention, the braking means comprise a braking disc integral with the rotating reel, a block acting on the braking disc and a drive arm on which the block is mounted. The drive arm has a first connection end pivoted to the support structure and a second free connection end to which the pair of springs is connected and on which a resultant force of the forces acts, causing the variable brake torque on the block.

[0027] In accordance with another aspect of the present invention, the tensioning means comprise an actuator which can be driven to selectively determine a completely raised condition of the second tensioning element such that the second force is maximum, but slightly smaller than or at most equal to the first force.

[0028] Embodiments of the present invention also concern a stranding machine comprising a frame on which a feed apparatus and, in succession, a stranding unit are installed. The feed apparatus comprises a plurality of the unwinding units aligned in sequence along a longitudinal axis of the stranding machine.

[0029] DESCRIPTION OF THE DRAWINGS

[0030] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of one embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

[0031] - fig. 1 is a lateral view of a reel unwinding unit according to the present invention typically applicable to a stranding machine for the production of strands;

[0032] - fig. 2 is a plan view of fig. 1;

[0033] - fig. 3 is a rear view of fig. 1 ; - fig. 4 is an example of a stranding machine which comprises a plurality of unwinding units according to the present invention;

[0034] - fig. 5 is an enlarged detail illustrating one of the unwinding units installed on the stranding machine in fig. 4.

[0035] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

[0036] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications. DESCRIPTION OF ONE EMBODIMENT OF THE PRESENT INVENTION

[0037] With reference to figs. 1-3, an unwinding unit 10 according to the present invention is typically installed in a stranding machine 100 (fig. 4) for the production of threadlike metal products, in this specific case strands, and comprises a support structure, or cradle, 11 on which a reel 12 is mounted containing a wire 13 wound in coils, and braking means 14 configured to apply a variable brake torque on the reel 12 in order to keep the tension on the wire 13 constant as it unwinds.

[0038] By way of example only, the wire 13 can consist of a metal material, for example steel, and have a diameter comprised between about 2 mm and about 8 mm, while the strands obtained with the stranding machine 100 can have a diameter comprised from between about 6 mm to about 24 mm.

[0039] With reference to fig. 2, the support structure 11 comprises two opposing lateral walls 11a, l ib, hereinafter also referred to as the first and second lateral wall, between which a shaft 15 on which the reel 12 to be unwound is mounted is supported by means of bearings.

[0040] The support structure 11 is essentially symmetrical with respect to a central plane S equidistant from the lateral walls I la, 11b (fig. 2).

[0041] The shaft 15 can be removed from the support structure 11 to allow the installation and removal of the reel 12 in a known manner. The reel 11 is rotatable around its own axis of rotation X, which corresponds to the axis of rotation of the shaft 15, as a consequence of the application of a traction force T applied to the wire 13, for example by means of a drawing unit located downstream and not shown. With reference to figs. 1 and 4, the axis of rotation X is shown in a horizontal condition. However, the entire unwinding unit 10 can also operate slightly inclined, and is able to tilt on a vertical plane as subsequently described with reference to the stranding machine 100.

[0042] With reference to figs. 1 and 2, the support structure 11 comprises a front portion 11 c on which an eyelet 16 is provided, through which the wire 13 unwound from the reel 12 is made to pass. The eyelet 16 has a passage channel 16a which develops along an exit axis Y lying on a plane parallel to a lying plane A of the axis of rotation X (fig. 1). The lying plane A is orthogonal to the central plane S. The exit axis Y is substantially orthogonal to the axis of rotation X.

[0043] The support structure 11 also comprises a rear portion l id opposite the front portion 11c. In a substantially intermediate position between the front portion 11c and the rear portion l id, toward which the lateral walls 11a, 11b converge, the shaft 15 and therefore the reel 12 are installed (fig. 2).

[0044] The unwinding unit 10, according to the invention, comprises tensioning means 17 configured to apply, continuously, a certain tension on the wire 13 being unwound and adjustment means 18 associated both with the tensioning means 17 and also with the braking means 14 in order to continuously determine the variable brake torque which is a function of a position assumed by the tensioning means 17 as a consequence of a pressure applied to the wire 13 as it unwinds.

[0045] This advantageously allows to ensure a constant tension on the wire 13 coming out of the reel 12 regardless of the quantity of wire present on the reel 12, the diameter of the wire 13, the traction force T or other anomalies, applying a continuously variable brake torque.

[0046] With reference to figs. 1-3, the tensioning means 17 comprise a first tensioning element 19 attached in correspondence with 19a, 19b to the support structure 11 and configured to receive the unwinding wire 13 and support it. In particular, the first tensioning element 19 is attached to the lateral walls I la, 1 lb of the support structure 11 (figs. 2 and 3).

[0047] The first tensioning element 19 determines a first “fixed” point of contact Pl for the wire 13 exiting the reel 12 (figs. 1 and 2). In other words, the wire 13 exiting from the reel 12 is constantly resting on an upper portion of the first tensioning element 19.

[0048] The tensioning means 17 also comprise a second tensioning element 20 pivoted to the support structure 11 by means of arms 21, 22 which allow an angular travel thereof on a substantially vertical plane, which by way of example can be the same central plane S, to determine a variable pressure on the unwinding wire 13 (fig. 2).

[0049] In a normal operating condition of the unwinding unit 10, the second tensioning element 20 (indicated by a continuous line in fig. 1) is substantially facing the eyelet 16 and oscillates up and down around the plane containing the exit axis Y. In this way the wire 13 is already partly guided toward the eyelet 16 with a very limited angle which allows to minimize possible damage or excessive entry pressure / friction.

[0050] With reference to fig. 2, a first arm 21 is pivoted to the first lateral wall 1 la, while a second arm 22 is pivoted to the second lateral wall l ib of the support structure 11 with its own pivoting ends 21a, 22a. In correspondence with the support ends 21b, 22b of the arms 21, 22, opposite to the pivoting ends 21a, 22a, the second tensioning element 20 is supported.

[0051] The second tensioning element 20 determines a second “mobile” point of contact P2 of the wire 13 exiting the reel 12. In other words, the wire 13 exiting the reel 12 is constantly resting on the upper portion of the first tensioning element

[0052] 19 and is pressed downward by the second tensioning element 20 with a variable pressure which determines its correct tensioning. For this reason, the second point of contact P2 is defined as “mobile”. With reference to figs. 1 and 2, the first and second tensioning elements 19, 20 are arranged between the reel 12, or the shaft 15, and the front portion 11c of the support structure 11 which comprises the eyelet 16. In particular, the first tensioning element 19 is located between the reel 12, or the shaft 15, and the second tensioning element 20; the second tensioning element 20 is located between the first tensioning element 19 and the front portion 1 lc, or the eyelet 16.

[0053] The first and second tensioning elements 19, 20 comprise a first and second idle roll 23, 24 which are distinct and independent, both being parallel to the axis of rotation X and arranged vertically staggered with respect to each other. By idle roll we mean a roll that rotates around its own axis, in this specific case, due to the friction that the wire 13 exerts respectively in correspondence with the first and second point of contact Pl, P2 as it advances.

[0054] The first idle roll 23 has an extension substantially equal to the distance between the lateral walls I la, 1 lb of the support structure 11. This advantageously allows the wire 13 to be supported regardless of the position of the coil on the reel 12 which evidently varies in the direction of the axis of rotation X during the unwinding action.

[0055] The second idle roll 24, on the other hand, has a smaller extension, for example about half of the first idle roll 23, essentially to accompany the wire 13 to converge toward the eyelet 16.

[0056] The adjustment means 18 comprise a pair of springs 25, 26 with opposing forces Fl, F2 (figs. 1 and 3). Both forces Fl, F2 have a substantially vertical directrix of action. However, as previously specified, the entire unwinding unit 10 could also operate inclined, therefore the directrix of action would, in this case, be equally inclined.

[0057] A first spring 25 is connected to the support structure 11 , in this case to the second lateral wall 11b, and to the braking means 14, and is pre-adjusted with a first force Fl to determine a maximum brake torque on the reel 12 (figs. 1 and 3).

[0058] A second spring 26 is connected to one of the arms 21, 22, in this case to the second arm 22, and to the braking means 14, generating a second force F2 opposed to the first force F 1 and variable according to the pressure exerted on the unwinding wire 13 (figs. 1 and 3).

[0059] With particular reference to fig. 1, the second spring 26 is attached to the second arm 22 in a position between the pivoting end 22a with the second wall 1 lb and the support end 22b with the second tensioning element 20. This position is closer to the pivoting end 22a compared to the supporting end 22b.

[0060] The second force F2 is always less than the first force Fl therefore the reel 12 is always, even slightly, braked.

[0061] The braking means 14 comprise a braking disc 27 integral with the rotating reel 12, or with the shaft 15, a block 28 acting on the braking disc 27 and a drive arm

[0062] 29 on which the block 28 is mounted (fig. 1).

[0063] The drive arm 29 has a first connection end 29a pivoted to the support structure 11, in this case to the second wall 11b, and a second free connection end 29b, to which the pair of springs 25, 26 is connected and on which a resultant force F of the forces Fl, F2 acts, causing the variable brake torque on the block 28.

[0064] It should be noted that, for explanatory purposes only, the resultant force F is shown applied to the block 28. The variable brake torque is therefore equal to the product of the resultant force F and the distance of application of the resultant force

[0065] F, which corresponds to the zone of contact between the block 28 and the braking disc 27.

[0066] The block 28 is mounted in an intermediate position between the first connection end 29a and the second connection end 29b of the drive arm 29. According to possible embodiments, not shown, the braking means 14, as previously described, can be provided in a specular manner on both sides of the reel 12, in correspondence with the first wall 1 la and the second wall 1 lb. This embodiment is therefore characterized by the presence of a double brake unit with evident advantages in terms of stability, balance, balancing and effectiveness of the braking action on the reel 12.

[0067] With reference to figs. 1-3, the tensioning means 17 also comprise an actuator

[0068] 30 associated with the support structure 11, in this case with the first lateral wall I la, and connected, by means of a transmission bar 31, to the first arm 21, in correspondence with the pivoting end 21a, to selectively determine a completely raised condition of the second tensioning element 20 (indicated by a dotted line in fig. 1) such that the second force F2 is maximum, but slightly smaller than or at most equal to the first force F 1.

[0069] When the second tensioning element 20 is in the raised condition, the reel 12 is substantially free to rotate, preferably always with a minimum brake torque, and it is possible to carry out the reel change or other operations.

[0070] A completely lowered condition of the second tensioning element 20 (indicated with a line of dashes in fig. 1) is reached, on the contrary, if the force F2 becomes zero or is around zero, which happens, for example, in in the event of breakage of the wire 13 or in the event of a sudden deceleration of the reel 12 following a machine stop or other cause. In this case, the brake torque is maximum and the reel 12 is stopped almost instantaneously.

[0071] With reference to fig. 4, a stranding machine 100 is schematically shown which comprises a frame 110 on which a feed apparatus 111 and, in succession, a stranding unit 112 are installed. The stranding unit 112 is configured to form the strands starting from a plurality of individual wires 13 fed by the feed apparatus 111.

[0072] The feed apparatus 111 comprises a plurality of unwinding units 10, in this case seven, aligned in sequence along a longitudinal axis L of the machine. The longitudinal axis L is parallel to the exit axes XI which define the exit direction of the individual wires 13 from the respective unwinding units 10.

[0073] In the example of fig. 4, a first unwinding unit 10a is static, and can provide one of the external wires 13 that make up the strand, while the subsequent unwinding units 10b are mounted on the frame 110 by means of bearings 113 applied to the front 11c and rear l id portions of the support 11 or cradles and are therefore free to tilt around the longitudinal axis L, hence the term cradle. The central wire of the strand on which the other wires are wound is unwound by the penultimate unwinding unit 10b which, numbered with respect to the first, is the sixth in fig. 4. With reference to fig. 5, each unwinding unit 10b carries a pair of guide elements, or arches, 32 which are rotatable around the longitudinal axis X and allow to guide the wire 13 unwound by the preceding winding units 10 toward the stranding unit 112 located downstream of the machine.

[0074] It is clear that modifications and / or additions of parts may be made to the unwinding unit 10 and the stranding machine 100, without departing from the field and scope of the present invention, as defined by the claims.

[0075] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of a reel unwinding unit for a stranding machine and corresponding stranding machine, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0076] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Unwinding unit (10) comprising a support structure (11) on which there are mounted both a reel (12), containing a wire (13) wound into coils, said reel (12) being rotatable around an axis of rotation (X) thereof for the application of a traction force (T) on said wire (13), and also braking means (14) configured to apply a variable brake torque on said reel (12), characterized in that it comprises tensioning means (17) configured to apply a certain tension on said wire (13) being unwound, and adjustment means (18) associated both with said tensioning means (17) and also with said braking means (14) to continuously determine said variable brake torque, which is a function of a position assumed by said tensioning means (17) as a consequence of a pressure applied to said wire (13).

2. Unwinding unit (10) as in claim 1, characterized in that said tensioning means (17) comprise a first tensioning element (19) attached to said support structure (11) in order to receive, resting, said wire (13) being unwound, and a second tensioning element (20) pivoted to said support structure ( 11 ) by means of arms (21 , 22) which allow an angular travel thereof on a substantially vertical plane in order to determine a variable pressure on said wire (13).

3. Unwinding unit (10) as in claim 2, characterized in that said first and second tensioning elements (19, 20) are distinct and independent first and second idle rolls (23, 24), both being parallel to said axis of rotation (X) and arranged vertically offset with respect to each other.

4. Unwinding unit (10) as in claim 3, characterized in that said first roll (23) is pivoted to opposite lateral walls (11a, 1 lb) of said support structure (11) and has an extension equal to the distance between them, and in that said second idle roll (24) has a smaller extension than said first idle roll (23).

5. Unwinding unit (10) as in any claim hereinbefore, characterized in that said adjustment means (18) comprise a pair of springs (25, 26) with opposing forces (Fl, F2) able to adjust said variable brake torque as a function of the position assumed by said tensioning means (17).

6. Unwinding unit (10) as in claim 5, characterized in that a first spring (25) is connected to said support structure (11) and to said braking means (14), said first spring (25) being pre-adjusted with a first force (Fl) in order to determine a maximum brake torque, and in that a second spring (26) is connected to one ofsaid arms (21, 22) and to said braking means (14) generating a second force (F2 ) opposed to said first force (Fl) and variable as a function of the pressure exerted on said wire (13).

7. Unwinding unit (10) as in claim 5 or 6, characterized in that said braking means (14) comprise a braking disc (27) integral with said rotating reel (12), a block (28) acting on said braking disc (27), and a drive arm (29) on which said block (28) is mounted, wherein said drive arm (29) has a first connection end (29a) pivoted to said support structure (11) and a second free connection end (29b) to which said pair of springs (25, 26) is connected and on which a resultant force (F) of said forces (Fl, F2) acts, causing said variable brake torque on said block (28).

8. Unwinding unit (10) as in claim 1, characterized in that said tensioning means (17) comprise an actuator (30) able to be driven in order to selectively determine a completely raised condition of said second tensioning element (20) such that said second force (F2) is maximum, in any case slightly smaller than or at most equal to said first force (Fl).

9. Stranding machine (100) comprising a frame (110) on which a feed apparatus (111) and, in succession, a stranding unit (112) are installed, characterized in that said feed apparatus (111) comprises a plurality of unwinding units (10), as in any claim from 1 to 8, aligned in sequence along a longitudinal axis (L) of said stranding machine (100).

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