FR2633539A1 - Tension generator - Google Patents

Abstract

Wire tension generator for a power saw. The invention makes it possible to have available, for carrying out various power sawing work, a cutting wire tension generator which is simple, accurate, stable and capable of generating a wire tension at a predetermined value, or of making this tension vary during the power sawing according to a procedure which is specific to a particular sawing operation. It consists for example of identical wire guides, of a tensioning cylinder 14 moved by a system of spindles, connecting rods and jack 18, of an electronic regulator slaved to the force of the jack, this force is thus continuously adjusted to a fixed or modulated value depending on a law which is specific to the sawing envisaged. This device makes it possible to control the parameters for sawing with a wire and with an abrasive strip, and to produce cuts which fall broadly within the tolerances required by the electronics industry.

Description

 In the industry, wire saws are used for several fields of application.

 Some saws have a single wire, others several; some are alternative with one or more wires stretched between frames, others, rotary, have cylinders which organize a chain that can contain several wires.

 All are equipped with VOLTAGE GENERATORS acting upstream and downstream of the cutting area.

 For certain applications, only the cut is sought, the quality of the sawn surfaces not involved in the following machining operations.

 For other applications (electronic optics), sawing must be the machining giving the cut and the surface quality.

 Generally, in the current technical state of these wire saws, the tension is produced for example - by VOLTAGE GENERATORS with static load from weights or springs, - by dynamic VOLTAGE GENERATORS acting from mechanisms controlled by motors.

 These two types of VOLTAGE GENERATORS are not very precise, not very stable, they have the following drawbacks, both when stopped and in dynamic mode.

 They do not make it possible to establish a predetermined tension with great precision and to maintain it rigorously over time.

 They generally require very expensive mechanical, electrical or electronic regulation.

 They generate tensions with significant cyclic or random inaccuracies, due to friction, response times of the regulations and / or various inertias.

 For certain precision industrial projects, for example the production of electronic components, the sawn silicon base plates must have the following three characteristics 1. a surface condition free of scratches, 2. rigorous flatness of the faces of the cut parts, 3 perfect parallelism between the faces of the sawn pieces.

 The best current conventional wire saws do not make it possible to obtain the above characteristics and produce parts with the following defects 1. a surface condition with accidental scratches which can range, inter alia, up to 50 microns in depth.

2. a surface condition with a roughness giving significant hollows of up to 100 microns.

3. a defect in flatness giving a large cylindrical-conical bulge of up to 200 microns for example.

4. a systematic defect in parallelism of the sawed faces which can go up to 40 microns for example.

5. vibrational phenomena organizing the roughness faults according to geometric figures, which vary according to the natural frequency of the saw and its harmonics.

 These characteristics are mainly the result of the realization of the cutting line tension management, which does not allow to choose, measure and rigorously stabilize a wire tension before the initiation of a cutting cycle and even less during this time. cycle, independently 1 - of the voltage variations produced before and after the cutting zone during the sawing cycle of the workpiece, 2 - of the wire unwinding speed, whatever the acceleration or deceleration.

 The invention which is the subject of this patent applies to rotary saws with wires equipped with cylinder wire guides and aims to obviate these drawbacks by allowing in particular - to tension the cutting line directly in the active sawing area without modify the tension before and after this zone, - lengthen a wire by a predetermined quantity (in millimeters per meter for example) and produce it strictly at this value at all gaits of the cutting, - establish in the section of the wire used a constraint at a predetermined value (in megapascal for example) and to maintain it strictly at this value at all paces of the cutting, - to generate the tension of a wire at a predetermined value (in Newton for example ) to maintain it rigorously at this value at all stages of cutting, - to generate and regulate the three above functions with a simple regulation system, apart from disturbances due friction or various inertias, at all stages of the cutting operation, - to choose, measure and continuously regulate the tension and stress of the wires in the active cutting area independently of the voltage fluctuations occurring before and after the sectioning area, at all cutting speeds, - to change the tension of the wires during sawing, or to vary this tension according to a cutting procedure adapted to the section of the ingot to be sawed, - and finally to create three zones of tension of the cutting line completely independent of each other.

 The first area AA called the upstream part, the second BB said the middle cutting part, the third CC said the downstream part.

 In the middle part of section BB, the tension of the threads is generated and maintained by the tensioning cylinder 14. This tension established in the cross-section of the thread the stress chosen inside the elastic limit of the material of the thread used .

 The so-called primary upstream voltage may be little different from or equal to the downstream voltage, and both of the order of 40 years of the voltage generated in the middle section of section BB.

 This set of tension and wire movement management is designed symmetrical to ensure identically bi-directional operation, it comprises three parts, AA, BB and CC.

 The upstream part AA unwinds the wire towards the middle cutting part BB by regulating the tension to the so-called primary value.

 The middle cutting section BB where the secondary cutting tension is produced by the tensioning cylinder.

 The downstream part CC which winds the wire coming from the middle cutting part BB, by regulating the so-called primary tension.

 The upstream part AA is identical to the downstream part CC to ensure bidirectional operation.

 The description below is given by way of nonlimiting example of embodiment of the invention.

 FIG. 1 represents the perspective view of the tension generator for cutting wires in a wire saw.

 FIG. 2 represents the type of groove groove with the V-shaped sides and a depth equal to the diameter of the wire.

 FIG. 3 represents the diagram of the tensioning roller 14 with the jack 18 its servo-control 16 and the wire guides A and B.

 FIG. 4 represents the section W-W according to FIG. 3.

 FIG. 5 represents the diagram of the tensioning roller 14 with the jack 18 its servo-control 16 and the wire guides A and B.

 FIG. 9 represents the type of groove groove with circular bottom, of depth equal to the diameter of the wire.

 FIG. 10 represents the type of groove groove with the V-shaped sides, of depth equal to the diameter of the wire.

 Figure 11 shows the type of groove groove with circular bottom and deep equal to the radius of the wire.

 FIG. 12 represents the type of groove groove with trapezoidal profile, of depth equal to the diameter of the wire.

 The thread tension generator described below has two identical thread guides A and B fig. 1, a tensioning cylinder 14, a device with a jack 18 actuating a reference 6, driving the shaft 7 rotating, the levers 8 & 9 which move the tensioning cylinder 14; all assembled on a conventional frame with bearings and motor driving the shafts 4.

 An assembly, force sensor 15, its logic and regulation 16, of known type, controls the jack 18 which applies to the wire web 13 by means of the tensioning cylinder 14, the set force requested by the current cutting procedure.

 A thread guide A or B fig. 1 comprises a rotation shaft 4 on which is assembled a grooved cylinder divided into three tension zones 1, 2, 3, zones 1 and 3 known as regulators have the same length The length of the median zone 2 known as tension depends on the work to be done.

 The conditions of use of the wire saw determines the center distance C, the diameter of the wire guides A and B and that of the tensioning cylinder 14.

 The surfaces of the wire guides and of the tensioning cylinder Fig 1 are coated with an anti-wear layer 11 of known plastic material with characteristics suitable for treatment.

 The surfaces of the wire guides and of the tensioning cylinder Fig. 1 have circular grooves 10, contained in planes perpendicular to the shaft 4; these grooves 10 are machined in the thickness of the anti-wear layer 11.

 The spacing L of these grooves 10 is a function of the cutting work for which the wire guides are constructed.

 The number of these grooves 10 is a function of the sectioning work for which the wire guides are constructed.

 The depth P of the grooves 10 and the shape of their section Figs 2 and 6 to 10 is a function of the sawing work and of the wire 13 for which the wire guides are constructed.

 The modification of the surface hardness qualities of the wire guides and of the faces of the grooves is a function of the wire used and the work required of the generator, the coating can be carried out using micro-thickness deposition of carbide or metallic ceramic.

 Two identical, bidirectional reel-unwinders of known type, one located at the input of the generator ensures the supply of wire, the other located at the exit of the generator ensures the rewinding of the wire used.

 Among all the possible routes, the one described below is given by way of nonlimiting example.

 The wire 13 is supplied with R from the unwinding device (unwinder reel) from top to bottom.

 It is engaged vertically in the first groove of the regulating cylinder AA 1. After 1/4 of contact turn, it leaves this groove horizontally in the lower part to be engaged in the first groove in the lower part of the regulating cylinder AA 31 or it is wound of a half-turn to the upper part in X, from where it leaves this groove horizontally to engage in the upper part in the second groove of the cylinder AA 1 or it is wound up by a half-turn to the lower part , it leaves this groove horizontally to engage in the lower part in the second groove of the cylinder AA 31 or it is wound by a half-turn up to the upper part in X, and so on until the last groove in the upper part in D of cylinder AA 31.

From point D of cylinder AA 31, the wire passes through E into the first groove of cylinder BB 3 tensor where it is wound half a turn to the lower part. The wire then leaves the groove horizontally to be engaged in the lower part in the first groove of the tensioning cylinder BB 32 where it is wound by a half turn to the upper part at F, it leaves this groove horizontally to be engaged in the upper part in G in the second groove of the cylinder
BB 2 tensor and so on until the last groove of the cylinder BB 32 tensor at H, from where the wire will pass through the first I-groove of the regulating cylinder CC 3 where it is wound half a turn up to '' in the lower part, it leaves this groove horizontally to be engaged in the lower part in the first groove of the CC 33 regulator cylinder on which it is wound half a turn to the upper part in J, from where it will go horizontally in K, and so on to the lower part of the last groove of the CC 33 regulating cylinder, where it is wound a quarter turn to M to leave the stress generator vertically in S from bottom to top towards the winding device (winder unwinder) of the outgoing wire.

 The speed of rotation of the two wire guides and the variations of this speed are strictly synchronized.

 From point R to point D the wires are outside the action of the tensor cylinder, not being deflected they retain the so-called primary tension.

 From point E to point H the wires are elongated by deflection of the layer of wires by the tensor cylinder displaced by the action of the jack. The deflection force is regulated at its set point by closed loop control.

 From point I to point S the wires are outside the action of the tensor cylinder, not being deflected, they retain the so-called primary tension.

 The stress generator is designed to be perfectly symmetrical to ensure identical bidirectional operation.

 The regulating cylinders 1 and 31 have a sufficient number of grooves to prevent the wire from sliding from point D to point E, just as 3 and 33 prevents the wire from being drawn from I to H.

 The regulating cylinders 1 and 31 absorb the small variations in tension possibly produced by the wire unwinder at the input.

 The regulating cylinders 3 and 33 absorb the small variations in traction possibly produced by the wire winder at the outlet.

 As an example of application, this tension generator can in particular be used - to build a new type of wire saw with a wire tension system comprising a regulation controlled by a force sensor. This closed loop regulation will maintain the value of the voltage required by the cutting-off process at its set point. The tension set point can be a fixed predetermined value reached by a progressive procedure or a tension value varying according to a law imposed by a particular cutting method adapted to a material to be sawn or responding to precise precautions required by a form ingot section.

Claims (8)

1 - Voltage generator Fig.1 characterized in that it consists, in a first embodiment, of a pair of identical one-piece wire guides A and B, of a tensioning cylinder 14, of a jack 18, d '' a right-angle reference comprising a shaft 7 and three identical rods 6 and 8, a force sensor 15 mounted in line with the jack, an electronic regulation system 16 allowing the force to be adjusted at the set point cylinder 18 pushing force. This tension generator makes it possible to tension the wire to a predetermined value, to maintain this tension rigorously at all cutting speeds as well as during acceleration. The electronic regulator 16 can also control the following tension generator a variable force, the law of variation of which is a function of the parameters of the proposed cutting.  Each of the wire guides fig. 1 comprises a rotation shaft 4.4 on which is assembled a grooved cylinder divided into three zones, the zones 1 and 3 known as regulators have the same length, the median zone 2 known as of tension has a length depending on the needs of cutting.  The center distance C, the diameter of the wire guides A and B, the diameter and the length of the tensioning cylinder, are determined by the needs of cutting; the intensity of the wire tension force is determined by the needs of sawing. A and B and of the tensioning cylinder 14 are coated with a layer 11 of known plastic anti-wear suitable for cutting.  The surfaces Fig. 2 and 7 to 10 of the cylinders of the thread guides  The surfaces Fig.l and 2 of the cylinders of the wire guides and of the tensioning cylinder 14 have circular grooves 10 contained in planes perpendicular to the shaft 4; these grooves 10 are machined in the thickness of the layer 11.  The spacing L of these grooves 10 FIG. 4 & 6 is a function of the cross-section for which the wire guides are built.  The number of these grooves 10 is a function of the sectioning for which the wire guides are constructed.  The depth P of the grooves 10 and the shape of their section FIG. 2 and 7 to 10 are a function of the cutting capacity and of the wire 13 used.  AT  The double-acting cylinder 18 is of known type, the force sensor 15 comprising the control and regulation logic 16 is a conventional model which can operate in compression or in traction. 2 - Voltage generator according to claim Nç1 characterized in that the thrust cylinder 18 is constituted by a screw and ball nut with electric stepper motor. 3 - Voltage generator according to claim N 1 characterized in that the thrust cylinder 18 is formed by a double-acting hydraulic cylinder controlled in all or nothing mode in both directions. 4 - Voltage generator according to claims 1 and 3 characterized in that the thrust cylinder 18 is formed by a double-acting hydraulic cylinder controlled in differential pressure regime giving the force of the set point. 5 - Voltage generator according to claims N41 charac terized in that the thrust cylinder 18 is formed by a double-acting compressed air cylinder controlled in all or nothing mode in both directions. 6 - Voltage generator according to claims 1 and 5 characterized in that the thrust cylinder 18 is formed by a double-acting compressed air cylinder controlled under differential pressure regime giving the force of the set point. 7 - Voltage generator according to claims 1 2 3 4 5 & 6 characterized in that the link system 6 & 8 Fig. 3 pivoting on the axis 7 Fig. 3 is replaced by an eccentric 20 Fig. 7 pivoting on the bearings 21. The displacement of the tensioning cylinder 14 FIG. 7 is ensured by rotation of the eccentric 20 which is controlled by the displacement of the jack 18 actuating the references 19 and the deflection force of the ply of wires 13 is regulated at its set point by the force sensor 15 which controls the regulating device 16.  8 - Voltage stress generator according to claims 1 2 3 4 5 6 & 7 characterized in that the anti-wear coating t0 Fig. 2 made of plastic is replaced by a surface treatment to increase the surface hardness of the wire guides, the tensioning cylinder and the groove faces.  This hardening is a function of the wire used and the work required of the generator and can be carried out using micro-thickness deposition of carbide or metallic ceramic.