BOBBIN SUPPORT ARM WITH MODULATION OF MOTION TRANSMISSION BETWEEN THE ROLLER AND BOBBIN

Abstract: A bobbin support arm with modulation of the motion transmission between the roller and bobbin to prevent ribbing, by means of a rocker movement between the bobbin and roller determined by the oscillation of the arm both in the horizontal plane and in the vertical plane.

Description: This invention relates to a bobbin support arm for roller-driven bobbin winding stations, wherein the motion transmitted by a drive roller to a driven bobbin is modulated in order to prevent rib formation. The invention is described with reference to a winding machine, but can also find advantageous application in other operations in the textile industry, such as twisting and the like. It relates to bobbin winding both in machines in which the yarn is guided by slots or grooves provided along a spiral path in the bobbin drive roller, and in machines with a separate yarn guide. The bobbin is commonly driven by a rotary drum - in a form of a right cylinder or cone of small taper - which is kept in contact therewith along a generating line common to the two members. The technical problem to which the present invention relates derives from the fact that during winding, the rotary drum remains of constant shape and size, whereas the bobbin which gradually grows because of the yarn wound on it changes continuously in terms of its size and/or shape. If motion takes place under perfect friction, the peripheral speed of the drive drum coincides substantially with the linear winding speed of the yarn. In a very common type of winding machine, the drive drum, usually known as the roller, carries in that surface which engages the bobbin a spiral groove in which the yarn is engaged and guided so as to wind on the bobbin in a spiral pattern. In another type of winding machine, now obsolete because of its poor productivity, the yarn is distributed over the bobbin surface by a yarn guide made to travel with reciprocating motion along the bobbin generating line. As the bobbin size increases, its linear yarn winding speed remains substantially constant - and this is a necessary condition for proper execution of this operation - but its angular speed decreases linearly. As the yarn travels along the contact generating line in a constant time, the number of turns wound for each travel stroke of the yarn guide decreases slightly but continuously with each successive layer. The number of turns used for forming the complete spiral layer therefore decreases, as the turns become longer. The phenomenon therefore occurs in which when the spiral generated by the to-and-fro travel of the yarn contains an exact whole number of turns, the next spiral commences exactly superimposed on the preceding. An analogous drawback - although increasingly less serious - takes place when, instead of a whole number, the generated spiral contains a number of turns n¹/2, n¹/3, n¹/4 ...., where n is a positive whole number, and corresponds to generating 2, 3, 4 ... layers of spirals which each commence superimposed on the preceding. This phenomenon is commonly known as ribbing, and means that the bobbin becomes either unusable or of poor quality. Ribbed bobbins are difficult to unwind in the subsequent operations, are of variable compactness between their parts so that they cannot be correctly dyed and there is the risk of having to then discard them, and in addition the quantity of wound yarn no longer corresponds to the bobbin size. To prevent rib formation it is therefore necessary to avoid an exact ratio - at least for a short time - between the bobbin being wound and the yarn guide device. The known art uses various expedients for this purpose. The most common expedients are based on discontinuity of roller operation. This can be obtained by periodically raising the bobbin out of contact with the drive roller. The bobbin continues to rotate while slowing down, until contact with the roller is restored. Alternatively, the roller operation can be interrupted periodically by switching off the supply to its electric drive motor or by disconnecting the roller from the motor. In more sophisticated versions, the motor speed can be periodically varied. This type of expedient, although widely used, has considerable drawbacks because its effect varies as the size of the bobbin being formed varies. Its application to right cylindrical bobbins is also problematic because on restoring operation, consistency of the contact speed must be re-established along the entire generating line. A different expedient uses axial reciprocal movement between the drive roller and bobbin, produced by periodically displacing their shafts, for example by the action of a cam. In this manner, the spiral is made to terminate either before or after the preceding spiral. This expedient enables the ribs to be flattened but not eliminated, because excessive travel would deform the bobbin in an unacceptable manner. A further expedient was based - in the case of the obsolete yarn-guide winding machines - on varying their drive transmission ration, so varying the travel time (varying the travel time would be equivalent to the previously described expedient). With the obsolescence of yarn-guide winding machines, this expedient is no longer implemented, but even in yarn-guide winding machines these reciprocating motion members presented considerable problems in varying their speed. A further expedient, known from GB-A-699 137, uses periodic rocking action of the bobbin in the plane of the axes of the bobbin and the drive roller about an axis orthogonal to this plane, whereby the rocking axis intersects the generating line of contact between the drive roller and the bobbin, or passes in very close proximity thereto, and does not change its position as the diameter of the bobbin increases. In this way, a variation of the effective contact diameter between the drive roller and the bobbin and therefore a variation in the bobbin speed is obtained, enabling the spiral commencement points to be offset. This expedient offers substantially no drawback when forming conical bobbins, whereas drawbacks are encountered when this action is used in the production of right cylindrical bobbins. Varying the effective contact diameter is somewhat difficult, because the mass of yarn already wound and accumulated on the bobbin has to be significantly deformed. This can become substantially impracticable particularly in the initial stage. In contrast, the present invention enables the transmission ratio between the roller and bobbin to be regulated by varying the relative position of these latter in a rocking manner not fixed by the generating line, while keeping them always in contact, and thus without requiring substantial deformation even in the case of right cylindrical bobbins. For a correct understanding of the interactions between a conical bobbin and a right cylindrical roller which rotate in contact along a generating line, it must be remembered that within the contact segment there exists only one point on the conical bobbin, known as the neutral point, which is driven at the same peripheral speed as that at which the roller rotates. The peripheral speed increases from that point in the direction of the major base and consequently the bobbin slides on the roller and proceeds faster than it, whereas from that point in the direction of the minor base the bobbin slides on the roller and proceeds slower than it. The aforesaid rocking action in effect moves this neutral point along the contact segment. As the bobbin is deformable, this translation of the contact point takes place gradually along the line of contact. The present invention consists of a bobbin support arm as claimed in claim 1. The invention is described hereinafter in terms of a typical embodiment shown on the accompanying drawings. Figure 1 is a perspective overall view, Figure 2 is a view on the horizontal plane xy, Figure 2A is a side view on the plane yz, Figures 3A and 3B schematically show the movements of the bobbin respectively in the planes xy and xz. The driver roller 1, provided with yarn guide grooves, not shown, rotates about a fixed axis to consistently drive the bobbin 2, which rotates in the opposite direction. The bobbin 2 is wound on a tube supported on a pair of opposite centres 3 and 4 supported by an asymmetric fork 5, which is of a size sufficient to house the finished bobbin. The fork 5 comprises in its end 6 a cylindrical cavity in which a long pin 7 is disposed, which extends substantially orthogonal to the axis of the centres 3,4. The fork 5 is fixed to the pin 7 by a dowel 8 - or an equivalent means - which enables to adjust the angular position of the fork 5 about the axis of the pin 7, i.e. to adjust the inclination of the axis of the centres 3 and 4 to the axis of the roller 1, in order to be able to use tubes of different taper. On the extension of the end 6, and adjacent thereto, there is located a member 9 provided with a precision through bore for receiving the pin 7, which extends beyond that face of the member 9 distant from the end 6. The member 9 is rotatable about the axis of the pin 7 and forms part of an articulated quadrilateral connection comprising two substantially parallel members 9 and 12 and two non-parallel connecting rods 10 and 11 which latter pivotally connect the members 9 and 12 together and enable the member 9 to move with rocking motion about a centre C defined by the point at which the axes of the connecting rods 10 and 11 intersect. The support member 12 is pivotable only in a vertical plane a the pivot axis 13 parallel to the axis of the drive roller 1. The pivotal movement of the support member 12 is determined by the increase in the diameter of the bobbin or by external action to raise the fork 5, and results in the inclination of the rocking plane of the member 9. Rigid with the member 12 there is a device 14 for driving the member 9 with reciprocating motion in the direction of the axis of the pin 7, and indicated by way of example as a rotating cam, but which can be in the form of a connecting rod and crank or other linkages known in the art, to cause the member 9 to oscillate about the centre C and induce an oscillatory movement in the bobbin 2 by way of the pin 7, the fork 5 and the centres 3 and 4. The pin 7 terminates in a transverse bar 15 connected to a fixed part by two ball joints 16 and 17 which are connected together by an intermediate bar 18. The centre of rotation of the second joint 17 directly connected to the fixed part lies preferably on the pivot axis 13 or in proximity to it. With reference to Figure 3A, it is apparent that the operation of the device 14 causes the member 9 to oscillate, and this oscillation influences the contact of the bobbin 2 - which for ease of representation is shown in its initial stage - with the roller 1. The bobbin 2 moves continuously from the position shown by full lines, which corresponds to the member 9 in its position of maximum withdrawal, to the position shown by dashed lines, which corresponds to the member 9 in its opposite position of maximum advancement. As a result of the oscillation of the member 9, which causes consistent oscillation of the axis of the pin 7 substantially in the plane of rods 10 and 11, the restraint formed by the ball joints 16 and 17 causes the pin 7 to also rotate about its axis. This rotation generates in the fork 5 and bobbin 2 a rocking movement in the vertical plane as shown in Figure 3B. The result is a combined rocking and translating movement of the axis of the centres 3,4, i.e. of the bobbin 2, generating a neutral point trajectory which no longer coincides with the generating line. With regard to the behaviour of cylindrical bobbins, it should be noted that the motion shown in Figure 3A consists both of an axial translation and of rotation of an inclination of the bobbin axis with respect to the roller axis, these consequently no longer lying in the same plane. As a consequence of said inclination, the speed - both peripheral and angular - of the bobbin 2 is reduced by the cosine of α, where α is the angular value of the inclination. Even for small values of α, this speed variation is sufficient to prevent bobbin ribbing.

Claims: A bobbin support arm for roller-driven bobbin winding stations wherein the motion transmitted by a drive roller (1) to a driven bobbin (2) is modulated in order to prevent rib formation and the drive roller (1) is rotatable about a fixed axis, comprising a fork (5) having opposite centres (3,4) for supporting a tube on which the bobbin (2) is wound, said fork (5) being rockable about an axis of a pin (7) substantially orthogonal to the axis of the centres (3,4) - i.e. of the bobbin (2) -, characterized in that said pin (7) is connected at its end opposite the fork (5) to a fixed part by means of a double ball joint (16,17), in that an articulated quadrilateral connection is provided comprising two substantially parallel members (9 ,12), one (12) whereof is pivotable substantially in a vertical plane about an axis (13) parallel to the axis of the drive roller (1) and the other (9) whereof has a through bore receiving said pin (7) to enable said other member (9) to rotate about the axis of the pin (7), and two non-parallel connecting rods (10,11) pivotally connecting said members (9,12) together and determining a rocking movement of said other member (9) substantially about a centre (C) lying at the point at which the axes of the connecting rods (10,11) intersect, and in that a driving device (14) is provided for generating a reciprocating motion of said other member (9) in the direction of the axis of the pin (7) and about the centre (c) to generate a combined rocking and translating movement of the axis connecting the centres (3,4). A bobbin support arm as claimed in claim 1, characterized in that the centre of the ball joint (17) directly connected to the fixed part lies on, or is proximate to, the pivot axis (13) of said one member (12). A bobbin support arm as claimd in claim 1, characterized in that said driving device (14) consists of a rotating cam or a connecting rod and crank. A bobbin support arm as claimed in claim 1, characterized in that the fork (5) is angularly adjustable about the axis of the pin (7).

Inventors: BERTOLI, LUCIANO, COLLI, LUIGI, DE BENEDET, SERGIO
Applicants: SAVIO S.P.A.
Application year: 1987
Main classification: B65H54
IPC codes: B65H54