WO2005039812A1

WO2005039812A1 - Cutting process for the manufacture of a ring, cutting device, ring and push belt provided with the ring

Info

Publication number: WO2005039812A1
Application number: PCT/NL2004/000714
Authority: WO
Inventors: Cornelis Hendricus Maria Van Oirschot
Original assignee: Robert Bosch Gmbh
Priority date: 2003-10-24
Filing date: 2004-10-11
Publication date: 2005-05-06
Also published as: JP4966660B2; CN1871091A; NL1024614C2; JP2007508955A; CN100450682C

Abstract

Slitting process for producing a ring intended to be incorporated in a push belt, in which a tube (1) is clamped rotatably in a slitting device, and in which this slitting device is provided with an inner blade (3), and with an outer blade (2). The slitting process comprises a sub-phase (IIA) in which a blade (2), over at least one complete revolution of the tube (1), is guided down to a certain depth less than the wall thickness of the tube (1) , and in a second sub-phase (IIB) the blade (2) is guided through the remaining wall thickness.

Description

CUTTING PROCESS FOR THE MANUFACTURE OF A RING, CUTTING DE/ICE, RING AND PUSH BELT PROVIDED WITH A RING

The present invention relates to a method for producing a ring for a push belt for a continuously variable transmission. Rings of this type, in the remachined state and in combination with one another, form an endless tensioning element of a push belt . The rings are formed by cutting or slitting them from tubes formed from sheet material and are then, inter alia, barrel-polished to remove burrs and finally rolled and heat-treated. The ring is cut from the tube in a manner known per se with the aid of a slitting process. The slitting process is carried out with the aid of a slitting device in which the tube is clamped and which is provided with at least two interacting, cylindrical and rotatable blades, one of which is disposed on the inner side of a clamped tube and the other of which is disposed opposite it on the outer side of the clamped tube. The outermost or slitting blade is first of all, in what is known as a cutting-in phase, guided radially inwards through the wall of the tube, in rotation, over part of a revolution of the tube. The innermost or supporting blade is in the process held in the same radial position. After the tube has been cut into in this way and the slitting blade has been positioned through the entire wall thickness at least at one position on the circumference of the tube, in a final slitting phase the slitting blade, through further rotation thereof and of the tube, is guided through the material of the tube wall over the entire circumference of the tube, including the circumferential part over which the initial incision was made. In the known form of slitting, the tube is deformed by the shape of the blades and the nature of the slitting movement, and tends at least to change its inclination or to rotate in its clamping arrangement^ This combination of circumstances leads to the incision - which is intended to coincide with an imaginary plane oriented at right angles to the longitudinal direction of the tube - running in the axial direction during the slitting movement. This means that, in particular at the circumferential part of the tube where the incision was made, a burr is formed, while moreover at the end of the slitting process a broken surface is formed with residual material which projects beyond the nominal width of the ring. This burr and the residual material have to be removed, for example by barrel polishing, which is relatively difficult and slow, inter alia on account of the fact that the material to be removed has become very hard as a result of cold deformation. Therefore, it is an object of the invention to arrive at a slitting process which is more technically expedient and ultimately more advantageous, in which an axial side face of a ring which has been cut by slitting is less unpredictable and/or rough, so that the remachining time for the side face can be reduced and, moreover, it is possible to save on material required for the remachining. According to the invention, this object, with the associated advantages, is achieved if the measure described in the characterizing clause of Claim 1 is carried out. According to this measure, the cutting-in phase is to be carried out in two stages; in a first sub-phase, i.e. a running-in phase, thereof, the slitting blade is guided or forced a relatively short radial depth into the material of the tube over the entire circumference of the latter. Then, in a second sub-phase, i.e. a running-through phase of the cutting-in phase, in which the blades are guided through the entire wall thickness of the tube in the radial direction, the blades will be able to come to bear in the axial direction, against the axially oriented (partially) cut surfaces realized in this way over the tube. These circumstances and also the relatively low slitting force in the run-in phase greatly limits the abovementioned running of the incision in the axial direction. To boost this effect still further, it is preferable for the running-through phase to be distributed over at least one and preferably a number of revolutions of the tube. After the tube has been cut into over the entire wall thickness in this way, it is possible to move to the final slitting phase, which may be identical to that which is used in the known slitting process and in which the slitting blade preferably projects beyond the tube wall in the radial direction with a certain margin. In addition to an improvement in the cutting quality of the slitting process, moreover, the invention makes it possible to simultaneously cut and/or slit off a plurality of, or at least two, rings from a tube. This expedient doubling of the capacity of a slitting device is obtained if one of the said blades, preferably the outermost or slitting blade, has the same width as the ring that is to be slit off and is provided with a cutting edge on either side. The opposite blade, i.e. preferably the supporting blade, is in this case of double design, with each slitting blade interacting with one of the two cutting edges of the slitting blade. According to a further refinement of the invention, not all the blades are driven, but rather the innermost blade or innermost blades. In this way, the risk of an unfavourable orientation of the tube can be reduced further. In addition, it is preferable for the tube to be driven in a manner which causes it to follow the velocity of the supporting blade. The invention will be explained in more detail, by way of example, on the basis of a drawing, in which: Figure 1 diagrammatically depicts the existing process, which is known per se, for creating rings from a tube; Figure 2 uses cross sections to illustrate the effect of an offset, i.e. of an incision running in the existing process; Figure 3 represents a typical photographic image of a cross section through a ring produced using the known process; Figure 4 diagrammatically depicts the novel process for creating rings from a tube; Figure 5 uses cross sections to illustrate the effect of the measure according to the invention on the said offset in the novel process, or at least the effect of this on a ring; Figure 6 represents a typical photographic image of a cross section through a ring produced using the novel process. In the figures, identical reference symbols denote identical or at least corresponding design and/or functional properties of the present process and product . Figure 1 uses a cross section at right angles to the longitudinal direction of the tubular staring material, that is to say the tube for short, to diagrammatically depict a sub-process from the process used to produce a push belt which comprises an endless tensioning element and a multiplicity of transverse elements. The tension element comprises a multiplicity of what are known as cords which are held around one another, are continuous and are formed from metal rings, inter alia with the aid of a rolling treatment and a heat treatment. The metal rings are generally obtained from a tube which has been welded from material in sheet form, specifically by slitting or cutting these rings from the tube. Figure 1 illustrates a tube 1 around which the circles 2 indicate relative radial positions of a slitting blade 2 with respect to the tube 1. However, in reality the slitting blade 2 is in a fixed position in the tangential direction. During this slitting process, the tube 1 is clamped in a rotatable holder, which is not shown in more detail . On the inner side of the tube 1 there is an innermost blade or supporting blade 3, on the outer side of the tube 1 there is an opposite, slitting blade

2 which can move in the radial direction towards the axis of the tube 1. Both blades are cylindrical and rotatable in design and are preferably provided at least with corresponding diameters. In this case, the diameter of the innermost blade 3 is preferably only slightly smaller than the diameter of the inner circumference of the tube 1. During the slitting process, both the said blades 2, 3 and the tube 1 rotate, for which purpose at least one component 1, 2,

3 is driven in rotation. In the figure, the arrows indicate the relative direction of rotation of the components . A number of relative radial positions of the slitting blade 2, which as has been stated in reality is in a fixed arrangement in the circumferential direction of the tube and in this case positioned opposite the supporting blade 3, are indicated with the aid of Roman numerals. These radial positions I, IIA, IIB and III illustrated for the slitting blade 2 show the various phases of the slitting process. In this case radial position I indicates the result of a first or positioning phase, in which the slitting blade II is placed against the tube 1. In the radial position IIA, the slitting blade 2 is in a second or cutting-in phase, in which the tube 1, in this example, has been rotated through approximately 90° and the slitting blade 2 has cut into approximately two thirds of the wall thickness of the tube 1 in the radial direction. In radial position IIB, the slitting blade 2 has cut through the entire wall thickness of the tube 1 after rotation over virtually half the circumference thereof and the cutting-in phase is then complete. In this cutting-in phase, the slitting blade 2 forms a helical cutting line S in the material of the tube 1. From the moment at which the latter radial position IIB is reached, in a final or cutting-off phase, the blades 2, 3 execute a slitting movement over the entire circumference of the tube 1, specifically in an intended ideal plane oriented at right angles to the longitudinal direction of the tube. The radial position III of the slitting blade 2 illustrates this cutting- off phase, in which the slitting blade 2 cuts completely through the tube 1 and in which a ring 10 is cut off the tube 1. It should be noted that the cutting-in phase of the slitting process as outlined, in which the slitting blade is gradually moved from the radial position I to the position IIB, may in practice vary in the order from a few percent to 100% of the circumference of the tube 1, depending on process settings, type of blades 2, 3, wall thickness, circumference and material of the tube 1 and the like. Figure 2A uses a cross section over the length of the tube 1 to represent the radial position I, sketched in Figure 1, of the blades 2, 3 as a result of the positioning phase of the slitting process. In this case, tube part 1A is a clamped part 1A of the tube, and the tube part IB which is to be cut off corresponds to the ring 10 which is to be cut off from the tube 1. Figure 2B shows a corresponding representation of the radial position IIA of the slitting blade 2 in the cutting-in phase. The cross section illustrated is located approximately halfway through the distance over which the cutting-in phase extends along cutting line S from Figure 1. By deformation and/or displacement of the tube 1 and/or the clamping of the latter as a result of the level and type of slitting forces occurring, at least in the cutting-in phase, as the slitting process advances, the cutting line S between the clamped tube part 1A and the ring part IB which is to be cut off is formed not only in the desired radial direction but also runs at least to some extent in the axial direction of the tube 1. In practice, therefore, the cutting line S is more or less helical. As a result, in the cutting-off phase, which is illustrated in Figure 2C on the basis of the radial position III of the slitting blade 2, the substantially axially oriented cutting plane between the clamped tube part 1A and the tube part IB which is to be cut off is at least in part formed next to the cutting line S formed in the cutting-in phase, with a distance between them decreasing along the cutting line S over the wall thickness of the tube 1 from the outside inwards in the radial direction. The material of the tube 1 which is located between the said cutting plane and the cutting line S in the axial direction generally occurs as a burr 4 on the cut-off ring 10. The volume of material of this burr 4 is greatest at the location of the radial position I of the cutting blade 2 shown in Figure 1 as a result of the positioning phase and decreases over the circumference of the ring 10 formed in the direction of the end point of the cutting line S at the radially inner surface of the tube 1 which corresponds to the radial position IIB of the slitting blade 2 after the cutting-in phase has ended. This burr material necessarily seeks to find a way out in the cutting-off phase between the supporting blade 3 and the tube part IB which is to be cut off, and the latter is as a result forced radially outwards. The reason that the burr 4 is not cut off the ring 10 during the slitting process is that the tube part IB which is to be cut off, at least towards the end of the cutting-off phase, has so much freedom of movement that it slides inwards. The profile of the slitting process, i.e. the end of the cutting-off phase, is also characterized by the ring 10 being broken off the tube 1 rather than being cut off it in a controlled way. Figure 3 shows a typical photographic representation of a cross section, as described above, of the cut-off ring 10, clearly showing the burr 4 formed in the known slitting process. Figure 4 diagrammatically depicts the slitting process according to the invention corresponding to the illustration of the known slitting process shown in Figure 1. The slitting process according to the invention makes it possible to eliminate the above- described phenomenon of burring, at least to a considerable extent. For this purpose, according to the invention the second or cutting-in phase of the slitting process, in which the tube 1 is cut into by the slitting blade 2, after the latter, in the first phase, has been positioned against the tube 1 in the radial position I, is carried out in at least two stages or sub-phases. In a first sub-phase or running-in phase of the cutting-in phase, an incision is made in the material of the tube 1 to a relatively low depth, known as the insertion depth, over the entire circumference of the tube 1. According to the invention, the insertion depth is in this case preferably at least 10% and at most half of the wall thickness of the tube 1. In the said radial position IIA the slitting blade 2 is in a first part of the running-in phase, in which it is guided and/or forced from the radially outer surface of the tube 1 to the insertion depth through the material of the tube 1, and position IIB shows the slitting blade 2 in the vicinity of the end of the running-in phase, in which, in this example, the tube 1 has been rotated through approximately 450°, so that it has been cut into down to the desired insertion depth over the entire circumference. In the running-in phase, the slitting blade 2 forms a first section SI of the cutting line S between the clamped tube part 1A and the tube part IB which is to be cut off. On account of the relatively low radial depth of an incision of this type, known as the insertion depth, the slitting forces are so low that the above-mentioned deformation and/or displacement in the slitting direction scarcely occurs, and consequently the incision, or the said cutting line S, will advantageously lie in a virtually axially oriented plane. Then, in a second sub-phase, or cutting-through phase, of the cutting-in phase, which is illustrated by radial position IIC of the slitting blade 2, the remaining wall thickness of the tube 1 is cut into during a rotation of, in this example, approximately 90° of the tube. In the running-through phase, the slitting blade 2 forms a second section S2 of the cutting line S between the clamped tube part 1A and the tube part IB which is to be cut off. The running-through phase and therefore the total cutting- in phase is complete when the slitting blade 2 is in the radial position IID. From the moment at which the latter radial position IID is reached, in the known final or cutting- off phase using the blades 2, 3, a slitting movement is carried out over the entire circumference of the tube 1, specifically in an intended ideal plane oriented at right angles to the longitudinal direction of the tube. The radial position III of the slitting blade 2 illustrates the cutting-off phase, in which the slitting blade 2 cuts completely through the tube 1, with a certain margin, for example 25% of the wall thickness, with respect to its wall thickness, and in which a ring 10 is cut off the tube 1. In this novel execution of the slitting process, the burr 4 described above is not formed during the cutting-off phase. Moreover, in this case the breaking in the final part of the cutting-off phase is relatively slight and flat and specifically is substantially in the same plane as the plane in which the said cutting line S was formed in the previous phase, i.e. the cutting-in phase. In a more detailed refinement of the invention, the running-through phase is carried out in a number of revolutions of the tube 1, with the cutting blade 2 being forced further into the material of the tube over a relatively short radial distance, for example 25% of the total wall thickness of the tube 1, during or in each case after one revolution. Figure 5, in sub-figures 5A to 5E, shows cross sections over the length of the tube 1 illustrating the various phases of the novel slitting process described above. Figure 5A represents the radial position I, sketched in Figure 4, of the blades 2, 3 as a result of the positioning phase of the slitting process. In this case, tube part 1A is a clamped part 1A of the tube 1, and the tube part IB which is to be cut off corresponds to the ring 10 which is to be cut off the tube 1. Figure 5B shows a corresponding representation of the radial position IIA of the slitting blade 2 in the first sub-phase, or running-in phase, of the cutting-in phase, in which a first section SI of the cutting line S is formed between the clamped tube part 1A and the tube part IB which is to be cut off. The cross section illustrated is located at the start of this first section SI of the cutting line S, in which the slitting blade 2 is moved through the material of the tube 1 from the radially outer surface of the tube 1 to the said insertion depth. In this context, it should be noted that the cutting into of the tube 1 is associated with a material contraction 6 which is distinguished by a natural rounded shape 6 and should not be confused with the axial profile which is known from the known slitting process. Figure 5C shows a cross section through the tube 1 at the end of this first section SI of the cutting line S, in which the slitting blade 2 is moved through the material of the tube in the radial position IIB from Figure 4, i.e. at the insertion depth. The cross section illustrated, i.e. the position on the circumference of the tube 1, coincides with the position in which the start of the first section SI of the cutting line S shown in Figure 5B was formed. It can be seen from Figures 5B and 5C that there is still an offset 7 or axial displacement or running of the cutting line S over the circumference of the tube 1 during the slitting movement in the novel slitting process according to the invention. The difference compared to the known slitting process, however, is both the said material contraction 6 and the said offset 7, on account of the small insertion depth over which the tube 1 is cut into in a first revolution thereof, is significantly smaller. Another significant difference is that the supporting blade 3, in the second sub-phase or running-through phase of the cutting-in phase, in which the second section S2 of the cutting line S is formed, which sub-phase is illustrated in Figure 5D, bears in the axial direction against a cut surface 8, extending in the radial direction, of the tube 1, so that this blade 3 and the tube 1 are guided with respect to one another and additional axial running of the cutting line S is largely avoided. On account of the relatively low slitting forces in the two sub-phases mentioned, the incision, i.e. the cutting line S, is therefore only displaced in the axial direction to a greatly reduced extent, and consequently only a small amount of material will be located in the axial direction between the cutting line S and the cutting plane between the clamped tube part 1A and the tube part IB which is to be cut off during the cutting-off phase. Figure 5E illustrates the cutting-off phase of the slitting process, in which the slitting blade is in the radial position III with respect to the tube 1 and the supporting blade 3. Ultimately, therefore, relatively flat and at least virtually burr-free, axially oriented side faces are obtained for both the clamped tube part 1A and the ring 10 which is formed, with the result that the above-mentioned barrel remachining process can be carried out less intensively, for example for a shorter time. The abovementioned advantageous aspects of the slitting process according to the invention can be boosted still further if the section S2 of the cutting line S is formed in a number of revolutions of the tube. Finally, Figure 6 shows a typical photographic illustration of a cross section through the ring 10 formed using the slitting process according to the invention, in which the above-mentioned burr 4 is present in only rudimentary form or is even at least virtually absent. The invention is not restricted to what has been described above, but rather also relates to everything which the person skilled in the art can unambiguously infer from the figures as well as what is presented in the following set of claims.

Claims

1. Slitting process for producing a ring (10) intended to be incorporated in an endless tensioning element of a push belt, in which a tube (1) formed from the material for the rings is clamped rotatably in a slitting device, and in which this slitting device is provided with an inner blade (3) , which acts on the inner side of the tube (1) , and with an outer blade (2) , which acts on the outer side of the tube (1) , in which slitting process, in a cutting-in phase, one (2) of the two blades (2, 3) is guided at least in the radial direction through the material of the tube (1) across the entire wall thickness thereof, and in a final phase the respective blade (2) is moved in the tangential direction through the material of the tube (1) for at least one complete revolution of the latter, characterized in that the cutting-in phase comprises at least two sub-phases, and in that in a first sub-phase thereof the respective blade (2) , in at least one complete revolution of the tube (1) , is guided to a certain depth in the radial direction through the material of the tube (1) , which depth is less than the wall thickness of the tube (1) , and in that in a second sub-phase thereof the respective blade (2) is guided at least in the radial direction through the remaining wall thickness of the tube (1) .

2. Slitting process according to Claim 1, characterized in that the said depth from the first sub-phase of the cutting-in phase is significantly less than the wall thickness of the tube (1) , in particular less than half the wall thickness.

3. Slitting process according to Claim 1 or 2, characterized in that the said depth from the first sub-phase of the cutting-in phase amounts to approximately 10% to 25% of the wall thickness of the tube (1) and is preferably virtually equal to 10% thereof .

4. Slitting process according to Claim 1, 2 or 3, characterized in that in the first sub-phase of the cutting-in phase an incision is made over the entire circumference of the tube (1) with a minimum depth in the radial direction in the range between approximately 10% and 25% of the wall thickness of the tube (1) , preferably at least 10% thereof.

5. Slitting process according to one of the preceding claims, characterized in that the second sub-phase of the cutting-in phase is carried out in at least one complete revolution of the tube (1) , but preferably with a radial displacement of the respective blade (2) per revolution of the tube (1) of approximately 15% to 35% of the wall thickness thereof.

6. Slitting process according to one of the preceding claims, characterized in that the innermost blade (3) and the outermost blade (2) are cylindrical and rotatable.

7. Slitting process according to Claim 6, characterized in that of the blades (2, 3) only the innermost blade (3) is driven in rotation.

8. Slitting process according to Claim 7 characterized in that the tube (1) is driven out of its clamping position, preferably, at least virtually, following the rotational speed of the innermost blade (3) .

9. Slitting process according to one of the preceding claims, characterized in that two or more innermost blades (3) and/or outermost blades (2) act simultaneously.

10. Ring (10) for an endless tensioning element of a push belt which, at least in part, is formed using the slitting process according to one of the preceding claims .

11. Push belt provided with a ring (10) according to Claim 10.

12. Slitting device for cutting a ring (10) for an endless tensioning element of a push belt from a tube (1) with the aid of a slitting process, provided with a clamping arrangement for a tube (1) , with a first, cylindrically formed and rotatable blade (3) , which acts on the inner side of the tube (1) , and with a second, cylindrically formed and rotatable blade (2) , which acts on the outer side of the tube (1) , characterized in that a third blade, which likewise acts on the inner side of the tube (1) , is provided at an axial distance from the first blade (3) .

13. Slitting device according to Claim 12, characterized in that the second blade (2) , as seen in an axial direction with respect to the tube (1) , has a dimension which corresponds to an axial dimension of the ring (10) which is to be cut off, and is provided with a right-angled cutting edge on either side.