The present invention relates to a blanking device, in particular a so-called fineblanking device. Such a device and method for using it are widely employed in industry for cutting metal parts from strip material, for example for manufacturing of metal transverse segments for continuously variable transmission drive belts. This well-known drive belt is provided with at least one endless carrier element, which typically comprises a set of mutually nested, flat and flexible metal bands, and a number of transverse segments that are incorporated in the drive belt in an essentially continuous row along the circumference of the endless carrier element. The European patent publication No. EP-1699579-A1 discusses the basic working principles of the known fine-blanking method and device, specifically in relation to such transverse segments.

In the known fine-blanking method, each transverse segment is shaped and cut from a strip of base material by means of a fine-blanking device. The known fineblanking device includes a punch and an ejector are applied on opposite sides of the said strip material. The (outer) contours of the punch and the ejector essentially follow the (plan view) contour shape of the transverse segment. Furthermore, a guide plate and a die plate are applied therein, likewise on opposite sides of the said strip material. The guide plate defines an opening wherein the punch is accommodated and the die plate defines an opening wherein the ejector is accommodated. The (inner) contours of the openings in the guide plate and the die plate also essentially follow the contour shape of the transverse segment, with some clearance being applied between these plates, on the one hand, and the punch and the ejector on the other.

To form the transverse segment, the strip material is clamped between the guide plate and the die plate, whereafter the punch is pressed into and ultimately through the strip material strip under the influence of a punch force exerted on the strip material by the punch. At the same time, the ejector is pushed against on the strip material opposite the punch, such that the ejector exerts an ejector force that partly, but not completely, counteracts the punch force. That is to say that the punch force exceeds the ejector force. Thus, a section of the strip material that will form the transverse segment is clamped between the punch and the ejector and, together, these three parts are moved relative to the guide plate, the die plate and surrounding parts of the strip material. This relative movement is continued until the punch has pierced completely through the strip material into die plate opening, at which point the transverse segment is cut loose the said surrounding parts of the strip. Thereafter, the punch is retracted fully into the opening of the guide plate, the guide plate and the die plate are moved away from one another, to release the strip material, and the ejector is raised, to allow the extraction of the transverse segment from the fine-blanking device. Finally, i.e. to complete a blanking (stroke) cycle, the strip material is advanced relative to the fine-blanking device and the blanking cycle starts again from the beginning, i.e. by clamping the strip material between the guide plate and the die plate, etc.

It is noted that, in practice, the said relative movement between the punch and the ejector, on the one hand, and the strip material, on the other hand, is typically realised, at least in part, by the forced reciprocation, i.e. the cyclical up and down movement of the die plate. In this case, the punch force can be realised simply by fixing the punch in place relative to the die plate and the ejector force can be realised by means of a spring, located between the press ram and an end face of the ejector opposite to its working surface that acts on the strip material. Nevertheless, preferably one of the punch force and the ejector force is realised by a controllable hydraulic pressure acting on the punch or the ejector respectively, in particular acting on an end face thereof opposite to its respective working surface acting on the strip material.

Such known fine-blanking method and device are widely adopted, not only to provide the transverse segments with a relatively smooth precisely cut circumference surface, but also to simultaneously shape and calibrate the main body surfaces of the transverse segments with high accuracy. In particular in this latter respect, a convex curvature is applied to a part of one of the main body surface of the transverse segment. This convexly curved surface part serves to allow the adjacent transverse segments in the drive belt to rotate relative to one another while remaining in mutual contact and is often denoted the rocking edge.

It is a well-known aspect of the known fine-blanking method and device process that a burr is formed therein on the cut circumference surface of the blanked part. In particular, such blanking burr is formed on an edge between the cut circumference surface of the blanked part and its main body surface on the side of the punch. In particular in relation to the application of the transverse segment in the drive belt, but generally for any fine-blanked part, such blanking burr is undesirable in principle and potentially even detrimental to the performance and/or service life. Therefore, after the fine-blanking thereof, the blanked parts are typically processed to remove the said blanking burr, for example in a well-known process step of (stone) tumbling, (sand/water/glass bead) blasting, laser deburring, etc.

The present invention aims to improve upon the known fine-blanking method and device in terms of the size of the said blanking burr formed therein. In particular, the present invention seeks to minimise the extend of the burr-removal processing that is required after fine-blanking and, ideally, to avoid such deburring after-processing altogether.

According to the present invention, such aim is realised with a novel fineblanking method that additionally comprises the step of pressing the ejector towards the punch under the influence of the ejector force that thereto exceeds the punch force, whereby the ejector cuts into the strip material until it reaches a certain fraction of the thickness of the strip material. In particular this additional step is included in the fine-blanking method after the step of clamping the strip material between the guide plate and the die plate and before the step of pressing the punch towards the ejector under the influence of a punch force that exceeds the ejector force. Effectively by this novel method, the cut between the blanked part and the surrounding parts of the strip material is made in two phases: a first cutting phase, wherein the strip material is partly cut from the side of the ejector, and a second cutting phase, wherein the strip material is cut from the side of the punch, which latter, second cut completes the first cut made by the ejector. By this novel fine-blanking method the extend of the blanking burr on the side of the punch can be advantageously reduced remarkably, potentially can be eliminated altogether.

According to the present invention, to complete the said additional step of the novel fine-blanking method, i.e. to complete the said first cutting phase thereof, either the punch force is raised relative to the ejector force, the ejector force is lowered relative to the punch force, or both. This latter option of both lowering the ejector force and raising the punch force is preferred when also shaping and calibrating the main body surfaces of the blanked part during the fine-blanking thereof, such as in case of the transverse segment. Moreover according to the invention, the thickness fraction of the cut made by the ejector in the said first cutting phase amounts to between 33% and 67% and preferably is essentially equal to 50%.

The present invention also concerns a novel fine-blanking device that is capable of carrying out the novel fine-blanking method, as well as further details of such novel method that explained hereinafter with reference to the drawing, in which: figure 1 is a schematic side view of a continuously variable transmission having a drive belt; figure 2 is a front view of a transverse segment for the drive belt for the continuously variable transmission; figure 3 is a side view of the transverse segment shown in figure 2; figures 4.1 and 4.2 schematically show a longitudinal section of a blanking area of a known fine-blanking device, and of a strip of base material being placed in there at two instances in a blanking (stroke) cycle; figure 5 illustrates a novel known fine-blanking device according to the present invention in a preferred embodiment and by way of a cross-section of its essential components; figures 6.1 to 6.8 schematically show the novel fine-blanking device of figure 5 at eight instances in the blanking cycle; and figure 7 is a graph indicating three of the forces at play in the novel fine-blanking device during the blanking cycle.

Figure 1 schematically shows a continuously variable transmission, such as for utilization in a motor vehicle. The continuously variable transmission is indicated in general by the reference sign 1.

The continuously variable transmission 1 comprises two pulleys 4, 5 being arranged on separate pulley shafts 2, 3. A drive belt 6 is provided in a closed loop around the pulleys 4, 5 and serves for transmitting torque between the pulley shafts 2, 3. The pulleys 4, 5 are each provided with two pulley sheaves, wherein the drive belt 6 is positioned and clamped between said two pulley sheaves, so that with the help of friction a force may be transmitted between the pulleys 4, 5 and the drive belt 6.

The drive belt 6 comprises two endless carriers elements 7 that are composed of a bundle of a number of mutually nested continuous bands. Transverse segments 10 are arranged on the carrier elements 7 forming an essentially contiguous row along the entire circumference thereof. The transverse segments 10 are provided movable with respect to the carrier elements 7, at least in the circumferential direction thereof. For the sake of simplicity, only a few of these transverse segments 10 are shown in figure 1.

Figures 2 and 3 show the transverse segment 10 of the known drive belt 6 in more detail. A front surface of the transverse segment 10 is indicated in general by the reference sign 11 , whereas a back surface of the transverse segment 10 is indicated in general by the reference sign 12. In the following, the front surface 11 and the back surface 12 are generally indicated as main body surfaces 11 , 12.

In the vertical direction, the transverse segment 10 comprises successively a base portion 13 of predominantly trapezoidal shape, a relatively narrow middle portion 14 and a top portion 15 of predominantly triangular shape. In the drive belt 6, the base portion 13 is located at the radially inner circumference side of the carrier elements 7, whereas the top portion 15 is located radially outward of the carrier elements 7. Furthermore, in the drive belt 6, at least a part of the front surface 11 of the transverse segment 10 abuts against at least a part of the back surface 12 of a succeeding transverse segment 10, whereas at least a part of the back surface 12 of the transverse segment 10 abuts against at least a part of the front surface 11 of a preceding transverse segment 10.

Both to the left and the right of the middle portion 14 thereof, the transverse segment 10 defines an opening 23 that serves to receive a respective one of the carrier elements 7. These openings 23 are bound in radial inward direction by respective carrying surfaces 16 that support the carrier elements 7 in radial outward direction. Furthermore, the base portion 13 comprises two pulley sheave contact surfaces 17. When the transverse segment 10 moves over the pulley 4, 5, contact between the transverse segment 10 and contact surfaces of the pulley sheaves is established through said pulley sheave contact surfaces 17.

At the front surface 11 in the base portion 13 of the transverse segment 10, a rocking edge 18 is defined. The rocking edge 18 is represented by a convexly curved area of the front surface 11 , which area separates two portions of the said front surface 11 in the height direction, which two portions are oriented at an angle relative to one other. The rocking edge 18 is located close to, but still at some distance below, i.e. radially inward of, the carrying surfaces 16. An important function of the rocking edge 18 is to provide a mutual pushing contact between the adjacent transverse segments 10, when said transverse segments 10 are in a slightly rotated or tilted position relative to one another at the pulleys 4, 5. In order to favourable realise a minimal contact stress in the said pushing contact between the said transverse segments 10 as well as for the stability of such contact, the rocking edge 18 preferably extends along the full local width of the transverse segments 10. Moreover,

Also, at the front surface 11 of the transverse segment 10, a projection 21 is provided. In the shown example, the projection 21 is arranged in the top portion 15, and corresponds in position to a slightly larger hole provided in the back surface 12. In figure 3, the hole is depicted by means of dashed lines and indicated by the reference sign 22. In the drive belt 6, the projection 21 of the transverse segment 10 is at least partially located inside the hole 22 of an adjacent transverse segment 10. The projection 21 and the corresponding hole 22 serve to prevent or at least limit mutual displacement of adjacent transverse segments 10 in a plane perpendicular to the circumferential direction of the drive belt 6.

The transverse segment 10 is typically cut out of plate- or strip-shaped base material 50 in a fine-blanking process by means of a fine-blanking device 55. In figures 4.1 and 4.2, the fine-blanking device 55 and the strip material 50 are schematically illustrated in a cross-section thereof in two separate instances of a blanking stroke cycle. In the known fine-blanking device 55 a punch 30, an ejector 40, a guide plate 60 and a die plate 70 are applied. The punch 30 and ejector 40 serve to shape and cut the transverse segment 10 from the surrounding parts of the strip material 50. The guide plate 60 and the die plate 70 serve to both clamp such surrounding parts of the strip material 50 between them, as well as to contain and guide the punch 30 and the ejector 40, where to each such plate 60; 70 defines a respective opening 61 ; 71 .

Before the actual cutting of the transverse segment 10 in (fine-)blanking, firstly the guide plate 60 and the die plate 70 clamp the strip material 50 between them. Then also a working surface 31 of the punch 30 and a working surface 41 of the ejector 40 are pressed against the strip material 50, at mutually opposite sides thereof, with the part 51 of the strip material 50 that is located between the punch 30 and the ejector 40 being destined to become the transverse segment 10. Accordingly, the said working surfaces 31 , 41 have a contour that substantially corresponds to the frontal shape of the transverse segment 10 illustrated in figure 2.

During the actual cutting of the transverse segment 10, the punch 30 and the ejector 40 are moved in unison relative to the guide plate 60 and the die plate 70 and in the general direction from the guide plate 60 towards the die plate 70, until the punch 30 has pierced the strip material 50 completely in its thickness direction. Hereby, the transverse segment 10 is cut loose from the surrounding strip material 50 along a cutting edge 72 of the die plate 70 outlining the said opening 71 thereof. To facilitate such blanking cutting, the cutting edge 72 of the die plate 70 is chamfered, as illustrated in figures 4.1 and 4.2. In reality, however, the amount of chamfering is much less than what is illustrated herein for clarity. For example, typically, a width and height the chamfer of the cutting edge 72 amounts to approximately one tenth of the thickness of the strip material 50.

In addition to the said punch 30, ejector 40, guide plate 60 and die plate 70, the known fine-blanking device 55 further includes an upper support (not illustrated; see figure 5, reference No. 80) and a lower support (not illustrated; see figure 5, reference No. 90). The upper support supports the punch 30 and the guide plate 60, whereas the lower support supports the ejector 40 and the die plate 70. At least one of these upper and lower supports is cyclically driven up and down by a press ram of the fine-blanking device 55, whereas the respective other support is fixed in place relative thereto. In particular, the driven support cycles between a so-called “top dead centre” position closest to the said fixed support (which position is reached just after the transverse segment 10 is cut loose from the surrounding strip material 50) and a so-called “bottom dead centre” position, wherein the punch 30 and the ejector 40, on the one hand, and the guide plate 60 and die plate 70, on the other hand, are mutually spaced apart to allow extraction of the blanked transverse segment 10, as well as the advancement of the strip material 50 for the following blanking stroke. Typically the underlying reciprocating movement of the press ram is mechanically realised by a rotating cam shaft (not illustrated). Typically also, the press ram acts on the said lower support and the said upper support is fixed in place, which particular setup is considered hereinafter.

It is noted that the terms upper, lower, top, bottom downward and upward are used herein with reference to the accompanying drawing figures and in order to conveniently describe the mutual position and relative movement of the respective parts of the fine-blanking device. However, these terms and drawing figures do not necessarily relate to or align with the direction of gravity.

It is a well-known feature of the above-described, known fine-blanking device 55 that a burr is formed at an edge E of the cut surfaces of the transverse segment 10 on the side of the punch 70. In order to avoid, or at least substantially reduce the size of such blanking burr, the present invention provides for a novel fine-blanking device 100 that is illustrated in figure 5 in a cross-section thereof.

In addition to the components that have already been discussed in relation to the known fine-blanking device 55, namely the punch 30, the ejector 40, the guide plate 60, the die plate 70, the upper support 80 and the lower support 90, the novel fine-blanking device 100 includes a compression-type spring 33 between the punch 30 and the upper support 80. Moreover, the punch 30 is provided with an abutment 32 that interacts with both an upper punch abutment surface 81 and a lower punch abutment surface 82 of the upper support 80, limiting both an upward and a downward displacement of the punch 30 relative to such upper support 80. Together the punch spring 33 and the upper support 80 -once the upper punch abutment surface 81 thereof acts on the punch 30- determine the force Fp that is exerted on the strip material 50 by the punch 30 -once the punch 30 is lifted of off the lower punch abutment surface 82 of the upper support 80 by the ejector force 40-.

Furthermore, one or more compression-type springs 73 are provided between the lower support 90 and the die plate 70, by which die plate springs 73 a gap G is realised between the lower support 90 and the die plate 70 in an unloaded, i.e. uncompressed (or at least minimally compressed) state thereof. Moreover, the ejector 40 is provided with an abutment 42 that limits an upward displacement thereof relative to the lower support 90. The ejector abutment 42 determines a maximum amount of protrusion of the ejector 40 beyond the lower support 90 that is determined such that:

- in the said unloaded state of the die plate spring(s) 73, i.e. when the die plate 70 is furthest from to the lower support 90, the ejector 40 does not protrude beyond the die plate 70; whereas

- in a maximally compressed state of the die plate spring(s) 73, i.e. when the die plate 70 is closest to the lower support 90, the ejector 40 protrudes beyond the die plate 70 by an amount (of protrusion) that is less than the thickness of the strip material 50, in particular having a value of between 33% and 67%, preferably of essentially 50% of such thickness.

Also the guide plate 60 is provided with an abutment 62 that interacts with the upper support 80 and that limits a displacement of the die plate 60 away from such upper support 80, i.e. in downward direction in figure 5. The guide plate abutment 62 determines that the guide plate 60 is positioned flush with the working surface 31 of the punch 30 when both are in a most downward position allowed by the guide plate abutment 62 and the punch abutment 32 respectively.

First hydraulic means are provided (not illustrated) that exert a hydraulic force Fg on the guide plate 60 in downward direction, i.e. towards the die plate 70. Second hydraulic means are provided (not illustrated) to exert a hydraulic force Fe on the ejector 40 in upward direction, i.e. towards the punch 30.

This novel fine-blanking device 100 is capable of cutting the transverse segment 10 from the (surrounding part of the) strip material 50 in two phases: a first cutting phase, wherein the strip material 50 is partly cut from the side of the ejector40 , and a second cutting phase, wherein the strip material 50 is cut from the side of the punch 30, which latter, second cut completes the first, partial cut made by the ejector 40. As a result, the extend of the blanking burr on the transverse segment 10 can be remarkably reduced.

In the following, the present invention is discussed with reference to figure 6 that depicts the novel fine-blanking device 100 of figure 5 in eight instances 6.1 to 6.8 during the blanking stroke cycle, while in figure 7 the punch force Fp (solid line), the guide plate force Fg (long-dashed line) and the ejector force Fe (short-dashed line) are graphed during such cycle, i.e. as a function of the position of the lower support 90 that is driven up and down by the press ram between the said bottom dead centre BDC and top dead centre TDC positions thereof. The positions of the lower support 90 numbered 1 through 8 in figure 7 correspond to the indices 1-8 of figure 6, i.e. correspond to the below-discussed instances 6.1-6.8 in the blanking stroke cycle. In figure 6.1 the novel fine-blanking device 100 is shown in an open position, while the lower support 90 is being driven upwards, i.e. essentially halfway between the said bottom dead centre (BDC) and top dead centre (TDC) positions thereof. The ejector force Fc causes the ejector 40 to follow such upward motion, abutting against the lower support 90 in upward direction. The punch 30 and the guide plate 60 are not (yet) in contact with the strip material 50 and, instead, both abut against the upper support 80 in downward direction under influence of the punch force Fp and the guide plate force Fg respectively. Thus, the guide plate 60 is flush with the punch 30 and the punch spring 33 is in its least compressed state. Also the die plate springs 73 are in their least compressed state, whereby the (said working surface of the) ejector 40 is located inside the (said opening of the) die plate 70, i.e. is also not (yet) in contact with the strip material 50.

In figure 6.2, by the continued upward motion of the lower support 90, the strip material 50 is clamped between the guide plate 60 and the die plate 70, by the gradual compression of the die plate springs 73 under the influence of the punch force Fp and the guide plate force Fg. In particular, in the blanking cycle instance of figure 6.2, the die plate springs 73 are compressed to such an extent that the ejector 40 is now flush with the die plate 70 and in contact with the strip material 50. This instance 6.2 marks the start of the first cutting phase of the novel fine-blanking method. In such first cutting phase, the die plate springs 73 are increasingly compressed further, by the continued upward motion of the lower support 90 that is resisted the punch force Fp and the guide plate force Fg. Thus the ejector 40 increasingly protrudes from the die plate 70, cutting into the strip material 50 and displacing the said part thereof representing the (to be formed) transverse segment 10 in the direction of the punch 30 that is thereby forced upward into the (said opening of the) guide plate 60 and lifted off of the upper support 80, while increasingly compressing the punch spring 33 and raising the punch Fp. These conditions, i.e. the said first cutting phase persists until the die plate 70 rests on the lower support 90, the die plate springs 73 are maximally compressed and the ejector 40 protrudes maximally beyond the die plate 70 and has cut furthest into the strip material 50, as illustrated in figure 6.3.

At this instance 6.3 the first cutting phase ends. Nevertheless, the upward motion of the lower support 90 still continues, meaning that the punch 30, the ejector 40, the guide plate 60 and the die plate 70 move upward as a whole, whereby the punch spring 33 is compressed further and now also the guide plate 60 is lifted off the upper support 80, as illustrated in figure 6.4. These latter conditions persists until the punch 30 abuts against the upper support 90 in upward direction, as illustrated in figure 6.5.

This instance 6.5 marks the start of the second cutting phase of the novel fineblanking method, since the punch 30 can now no longer follow the (continued) upward motion of the lower support 90 and starts to cut into the strip material 50, while displacing the said part thereof representing the (to be formed) transverse segment 10 in the direction of the ejector 40. Hereby, the punch force Fp increases sharply and the ejector 40 is forced downward into the (said opening of the) die plate 70. The ejector force Fe is reduced in order to control, in particular limit the punch force Fp in this second cutting phase. These conditions persist, i.e. the said second cutting phase continues, during the remaining part of the upward motion of the lower support 90 until the said top dead centre TDC position thereof is reached.

In the top dead centre TDC position of the lower support 90 that is illustrated in figure 6.6, the punch 30 has completely pierced the strip material 50. The ejector force Fe and the guide plate force Fg can now be switched-off, i.e. reduced to zero, thereby releasing the clamping force on the strip material 50. At the same time, the lower support 90 starts to be driven downwards, meaning that (at least initially) the punch 30, the ejector 40, the guide plate 60 and the die plate 70 move downward as a whole, as illustrated in figure 6.7. Hereby, the punch spring 33 and the die plate springs 73 gradually unload and decompress.

By the continued downward motion of the lower support 90, finally the punch 30 and the guide plate 60 rest again on the upper support 80 and the novel fineblanking device 100 opens, as illustrated in figure 6.8. At this instance 6.8, a hydraulic pressure can be applied to the ejector 40 to lift the transverse segment 10 as much possible above the die plate 70, to facilitate the extraction thereof from the novel fineblanking device 100. Preferably and for the same purpose, the strip material 50 is lifted away from the die plate 70 and the ejector 40 in this instance 6.8, as likewise illustrated in figure 6.8. After such extraction of the transverse segment 10, the strip material 50 is advanced to complete the blanking stroke and the blanking cycle restarts.

The present invention, in addition to the entirety of the preceding description and all details of the accompanying figures, also concerns and includes all the features of the appended set of claims. Bracketed references in the claims do not limit the scope thereof, but are merely provided as non-binding examples of the respective features. The claimed features can be applied separately in a given product or a given process, as the case may be, but it is also possible to apply any combination of two or more of such features therein.

The invention(s) represented by the present disclosure is (are) not limited to the embodiments and/or the examples that are explicitly mentioned herein, but also encompasses amendments, modifications and practical applications thereof that lie within reach of the person skilled in the relevant art.