A push belt for a continuously variable transmission is generally known. Usually, such a push belt comprises two endless, ribbon-like carriers shaped like a closed loop for carrying a relatively large number of transverse elements. The transverse elements are movably arranged along the entire circumference of the carriers, wherein, during operation, they are able to transmit forces which are related to a movement of the push belt.

In the following description of the transverse element, the mentioned directions refer to the situation in which the transverse element is part of the push belt. A longitudinal direction of the transverse element corresponds to a circumferential direction of the push belt. A vertical transverse direction of the transverse element corresponds to a radial direction of the push belt. A horizontal transverse direction of the transverse element corresponds to a direction perpendicular to both the longitudinal direction and the vertical transverse direction. The indication of any transverse element as subsequent transverse element or previous transverse element with respect to an adjacent transverse element is related to a direction of movement of the push belt.

In the horizontal transverse direction, on opposite sides, the transverse element is provided with recesses for receiving the carriers. For the purpose of supporting the carriers, the transverse element comprises carrying surfaces. In the horizontal transverse direction, on opposite sides, for the purpose of contact between the transverse element and pulley sheaves of a pulley of a continuously variable transmission, the transverse element is provided with pulley sheave contact surfaces, which are divergent in the direction of the carrying surfaces. The terms"top"and"bottom", which are hereinafter applied, are related to the direction of divergence; this is defined as being from bottom to top.

In the vertical transverse direction, from bottom to top, the transverse element comprises successively a basic portion, a neck portion and a top portion, wherein, in the horizontal transverse direction, the dimensions of the neck portion are relatively small.

The basic portion comprises the carrying surfaces and the pulley sheave contact surfaces. In the push belt, the basic portion is located at the side of the inner circumference of the push belt, whereas the top portion is located at the side of the outer circumference of the push belt.

The top portion comprises two retaining surfaces which are located opposite to the carrying surfaces. When the transverse element is arranged in a push belt, a position of the carriers in the radial direction is delimited by the carrying surfaces on the one hand, and by the retaining surfaces on the other hand.

The transverse element has two main body surfaces, namely a front surface and a back surface, which extend substantially parallel with respect to each other, substantially perpendicular to the longitudinal direction. At least a portion of the front surface of the transverse element is designed to contact at least a part of the back surface of a subsequent transverse element in the push belt, whereas at least a part of the back surface of the transverse element is designed to contact at least a part of the front surface of a previous transverse element in the push belt.

A circumferential surface, of which the carrying surfaces and the pulley sheave contact surfaces are part, extends between the two main body surfaces. In the longitudinal direction of the transverse element, a dimension of the circumferential surface is relatively small.

By means of a blanking process, the transverse element is manufactured out of basic material shaped like a sheet. In the blanking process, a cutting member and a supporting member are applied, wherein the cutting member is designed to cut the transverse element out of the basic material under the influence of a cutting force, and wherein the supporting member is designed to support the transverse element by a supporting force during the blanking process. The circumference of both the supporting surface and the cutting surface is substantially equal to the circumference of the transverse element. During the blanking process, the cutting member penetrates the basic material under the influence of pressure, wherein a mutual movement of transverse element to be blanked and the basic material is allowed. At that moment, the transverse element to be blanked is clamped between the cutting member and the supporting member.

Furthermore, in the blanking process, a mould is applied, which is provided with a receiving space for receiving the transverse element to be blanked, the supporting member and an end of the cutting member. The inner circumference of the receiving space substantially corresponds to the circumference of the cutting member, the supporting member, as well as the transverse element to be blanked, so that the receiving space is capable of receiving the transverse element to be blanked, practically without any play.

In conformity with that which has already been indicated, the transverse element has a basic portion and a top portion, which are connected to each other via a relatively narrow neck portion. Due to the fact that the transverse element is manufactured by means of a blanking process as described above, limitations apply to the design of the transverse element having the said portions. For example, a value of a relation between dimensions of the basic portion and dimensions of the top portion needs to be within a certain range.

When, for instance, the top portion is relatively too small, there is a chance that the cutting member breaks during the blanking process. Also, a distance between a carrying surface and an opposite retaining surface needs to be larger than a certain minimum distance. The smaller this distance is chosen to be, the smaller an elongated portion of the mould which is positioned in a recess of the transverse element during the blanking process needs to be, and the larger the chance that this elongated portion breaks off of the other portion of the mould under the influence of the forces prevailing during the blanking process.

According to the present invention, during the blanking process, use is made of a mould consisting of at least two separate mould components, wherein each mould component comprises a portion of an inner surface of the receiving space. This has important advantages, a number of which will now be described.

In the first place, by applying a divided mould, it is possible to obtain more freedom in respect of the design of the transverse element, on the basis of the fact that it is possible to adapt the division of the mould in mould components to the division of forces during the blanking process, wherein the latter division is related to the design of the transverse element. For example, it is possible to realize as separate mould components the elongated portions of the mould which are positioned in the recesses of the transverse element during the blanking process. In this way, breakage of the mould is prevented.

In the second place, as a result of the division of the mould in several mould components, the manufacturing process of the mould is simplified. In the case of a mould according to the state of the art, which is formed as one piece, advanced techniques such as wire sparking need to be applied for the purpose of forming the receiving space in the mould. Usually, after the receiving space has been formed, at least a portion of the inner surface of the receiving space is provided with a coating, in order to obtain a desired quality of the surface or to prolong the tool life of the mould, for example. Applying the coating in the receiving space having an inner circumference which substantially corresponds to the circumference of the transverse element is a cumbersome process. In this respect, the fact that the mould has a certain height, among other things for the purpose of being capable of accommodating the supporting member, plays a role, because, as a consequence, at some places of the inner surface of the receiving space, narrow channels are present, as it were.

In the case of a mould according to the present invention, the mould components are separately formed, wherein more conventional techniques may be applied. This is related to the general fact that it is easier to accurately shape an outer surface of an arbitrary element than an inner surface of a space in an arbitrary element. As far as coating is concerned, it is also true that it is easier to coat an outer surface of an arbitrary element than an inner surface of a space in an arbitrary element. Therefore, it is strongly preferred to coat the mould components previous to composing the mould by joining the mould components.

In the third place, the application of separate mould components allows for performing maintenance of the mould in a more goal-oriented manner. For example, it is important that portions of the inner surface of the receiving space serving to come into contact with the pulley sheave contact surfaces of the transverse element are provided with a certain relief. When this relief is worn out, it needs to be provided again, for example by means of grinding, unless the extent to which the relief is worn out is above a certain upper limit. In the case of the mould according to the present invention, it is possible that the relief is present on two separate mould components, which may each be removed and processed when the relief is worn out. Also, when separate mould components are applied, it is also possible to only replace components when necessary. According to the state of the art, in case a portion of the inner surface of the receiving space gets obsolete, it is necessary to replace or process the entire mould, which is more expensive than replacing or processing a few mould components.

In the fourth place, the division of the mould in mould components offers the possibility of manufacturing different mould components from different materials. Because the required surface quality of the circumferential surface of the transverse element is different for different portions of the circumferential surface, it is not necessary that all mould components have the same surface quality. Therefore, it is also not necessary that all mould components are manufactured from the same material. For example, in the case of mould components which are allowed to have a relatively low surface quality, a cheaper material may be applied than in the case of mould components which need to have a relatively high surface quality. It is also an option to provide at least a portion of mould components which, as a consequence of their application during the blanking process, wear out at the highest pace with wear- resistant material, which is usually relatively expensive.

The invention will be explained on the basis of the following description of preferred embodiments of the invention with reference to the drawing, in which equal reference signs indicate equal or similar components, and in which: figure 1 is a diagrammatical side view of a continuously variable transmission having a push belt; figure 2 is a front view of a transverse element for a push belt for a continuously variable transmission; figure 3 is a side view of the transverse element shown in figure 2; figure 4 shows a diagrammatical longitudinal section of a blanking area of a blanking device, as well as basic material placed in there; figure 5a diagrammatically shows a first stage of a blanking movement; figure 5b diagrammatically shows a second stage of the blanking movement; figure 5c diagrammatically shows a third stage of the blanking movement; and figure 5d diagrammatically shows a fourth stage of the blanking movement; figure 6 is a top view of a divided mould according to a first preferred embodiment of the present invention; and figure 7 is a top view of a divided mould according to a second preferred embodiment of the present invention.

Figure 1 diagrammatically 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. An endless push belt 6 being shaped like a closed loop is arranged around the pulleys 4,5, and serves for transmitting torque between the pulley shafts 2,3. Each of the pulleys 4,5 comprises two pulley sheaves, wherein the push 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 push belt 6.

The push belt 6 comprises two endless carriers 7, which are usually composed of a number of rings. Along the entire length of the carrier 7, transverse elements 10 are arranged, wherein the transverse elements 10 are mutually adjacent to each other and are moveable with respect to the carrier 7 in the circumferential direction. For the sake of simplicity, only a number of these transverse elements 10 is shown in figure 1.

Figures 2 and 3 show a transverse element 10. A front surface of the transverse element 10 is indicated in general by the reference sign 11, whereas a back surface of the transverse element 10 is indicated in general by the reference sign 12. In the following, both the front surface 11 and the back surface 12 are also indicated as main body surface 11, 12. A circumferential surface 19 extends between the main body surfaces 11,12.

In the vertical transverse direction, the transverse element 10 comprises successively a basic portion 13, a relatively narrow neck portion 14, and a top portion 15 shaped like the tip of an arrow. In the push belt 6, the basic portion 13 is located at the side of the inner circumference of the push belt 6, whereas the top portion 15 is located at the side of the outer circumference of the push belt 6. Furthermore, in a push belt 6, at least a portion of the front surface 11 of the transverse element 10 contacts at least a portion of the back surface 12 of a subsequent transverse element 10, whereas at least a portion of the back surface 12 of the transverse element 10 contacts against at least a portion of the front surface 11 of a preceding transverse element 10. At the transition to the neck portion 14, the basic portion 13 of the transverse element 10 as shown in figure 2 comprises two carrying surfaces 16 which serve for supporting two carriers 7. Furthermore, the basic portion 13 comprises two pulley sheave contact surfaces 17. When the transverse element 10 moves over the pulley 4,5, contact between the transverse element 10 and contact surfaces of the pulley sheaves is realized through said pulley sheave contact surfaces 17. A bottom surface 18 extends between the pulley sheave contact surfaces 17.

The carrying surfaces 16, the pulley sheave contact surfaces 17, as well as the bottom surface 18 are part of the circumferential surface 19.

The top portion 15 comprises two retaining surfaces 23 which are located opposite to the carrying surfaces 16. When the transverse element 10 is arranged in a push belt 6, a position of the carriers 7 in the radial direction is delimited by the carrying surfaces 16 on the one hand, and by the retaining surfaces 23 on the other hand. Furthermore, the top portion 15 comprises two top surfaces 24 which are connected to each other. At an end, each of the top surfaces 24 is connected to a retaining surface 23 of the top portion 15. Both the retaining surfaces 23 and the top surfaces 24 are part of the circumferential surface 19.

A blanking process known per se of the transverse element 10 will now be explained on the basis of figures 4 and 5a to 5d.

In figure 4, a blanking area of a blanking device 60 and basic material 50 being placed in there are diagrammatically depicted. The blanking device 60 comprises a cutting member 30 which is designed to cut the transverse element 10 out of the basic material 50. The cutting member 30 is accommodated in a guiding space 36 in a guiding plate 35, an important function of which is guiding the cutting member 30 during a blanking movement. A supporting member 40 is in line with the cutting member 30, which is designed to support the transverse element 10 during the blanking process. The circumference of both the cutting member 30 and the supporting member 40 substantially corresponds to the circumference of the transverse element 10 to be blanked. The supporting member 40 is accommodated in a receiving space 46 in a mould 45, an important function of which is guiding the cutting member 30, the supporting member 40, as well as the transverse element 10 during a blanking movement. The inner circumference of the receiving space 46 substantially corresponds to the circumference of the cutting member 30, the supporting member 40, as well as the transverse element 10.

Initially, the basic material 50 is located between the cutting member 30 and the guiding plate 35 on the one hand, and the supporting member 40 and the mould 45 on the other hand. A portion of the basic material 50 which is located between the cutting member 30 and the supporting member 40 is destined to form the transverse element 10, and will hereinafter be referred to as blanking portion 51. Another portion of the basic material 50, namely the portion that is located between the guiding plate 35 and the mould 45, will hereinafter be referred to as rest portion 52.

The mould 45 comprises a mould surface 47, an important function of which is supporting the rest portion 52 of the basic material 50. An inner surface 48 of the receiving space 46 of the mould 45 is connected to the mould surface 47.

In the following, a blanking movement is described on the basis of figures 5a to 5d, in which different successive stages of the blanking movement are diagrammatically depicted.

In a first stage or initial stage, as diagrammatically shown in figure 5a, the blanking portion 51 of the basic material 50 is clamped between the cutting member 30 and the supporting member 40, while a rest portion 52 is clamped between a guiding surface 37 of the guiding plate 35 and the mould surface 47 of the mould 45. In the process, the clamping forces act in a direction substantially perpendicular to the guiding surface 37 and the mould surface 47.

In a second stage, as diagrammatically shown in figure 5b, the entirety of cutting member 30, blanking portion 51 and supporting member 40 is moved with respect to the guiding plate 35, the rest portion 52 and the mould 45, under the influence of pressure. In the process, the direction of movement is substantially perpendicular to the guiding surface 37 and the mould surface 47. As a result of the mutual movement, the cutting member 30 penetrates the basic material 50, and the blanking portion 51 is pressed into the receiving space 46 of the mould 45.

In a third stage, as diagrammatically shown in figure 5c, the blanking portion 51 gets completely detached from the rest portion 52 as a result of the continuing mutual movement. Hereafter, the guiding plate 35 and the cutting member 30 are retracted with respect to the mould 45 and the supporting member 40, wherein the contact between the rest portion 52 and the guiding surface 37 is maintained, and wherein the contact between the rest portion 52 and the mould surface 47 is lost.

In a fourth stage, as diagrammatically shown in figure 5d, as a result of the mutual movement of the guiding plate 35 and the cutting member 30 on the one hand, and the mould 45 and the supporting member 40 on the other hand, the rest portion 52 has been put to a position at a distance from the mould surface 47. In this position, the rest portion 52 can be removed. Furthermore, the supporting member 40 has been moved with respect to the mould 45 in such a way that the blanking portion 51 has been put to a position above the level of the mould surface 47, so that the blanking portion 51 can be removed as well. In the process, the supporting member 40 may function as pushing member.

Figure 6 shows a top view of a mould 70 according to a first preferred embodiment of the present invention. For the sake of clarity, this mould 70 will hereinafter be referred to as first mould 70.

In accordance with known moulds 45, the first mould 70 has a receiving space 46 for receiving, among other things, the transverse element 10 to be blanked. According to an important aspect of the present invention, the first mould 70 comprises a number of separate mould components for delimiting the receiving space 46.

The first mould 70 comprises three mould components. For each of these three mould components, it is true that a portion of the surface thereof is part of the inner surface 48 of the receiving space 46. Said portion of the surface of the mould components will hereinafter be referred to as transverse element contact surface.

A first mould component will hereinafter be referred to as main component 71. The transverse element contact surface of this main component 71 is designed to contact, during the blanking process, both pulley sheave contact surfaces 17, the bottom surface 18 and both top surfaces 24 of the transverse element 10 to be blanked.

A second mould component and a third mould component will hereinafter be referred to as middle components, wherein one of the middle components is indicated by reference sign 72a in figure 6, whereas another of the middle components is indicated by reference sign 72b in figure 6. The transverse element contact surface of the middle components 72a, 72b is designed to contact, during the blanking process, a portion of the circumferential surface 19 of the transverse element 10 to be blanked, which extends from a transition surface between a pulley sheave contact surface 17 and a carrying surface 16 toward a transition surface between a retaining surface 23 and a top surface 24, at one side of the transverse element 10 to be blanked.

Both the second mould component 72a and the third mould component 72b are provided with a projection (not shown) or the like, in order to prevent a situation in which the mould component 72a, 72b is capable of moving along with a transverse element 10 that is pushed from the receiving space 46 by the supporting member 40. For this purpose, the projection is positioned such that it contacts a bottom surface of the main component 71, and is not capable of moving beyond that surface, wherein the term"bottom surfaces used to indicate a surface which is located at another side of the mould 70 than the mould surface 47.

After a rough version of the transverse element 10 has been cut out of the basic material 50 during a blanking process, the circumferential surface 19 of the transverse element 10 is shaped particularly by the inner surface 48 of the first mould 70. For the purpose of a proper functioning of the transverse element 10 in a push belt 6 for a continuously variable transmission 1, it is important that portions of the circumferential surface 19 which can come into contact with the carriers 7 of the push belt 6 have a good surface quality. These portions comprise the carrying surfaces 16 and the retaining surfaces 23. In case the surface quality of the portions would be insufficient, damage of a carrier 7 might occur, which may eventually lead to breakage of the carrier 7. For the sake of completeness, it is noted that the surface quality is related to the roughness of the surface in question. In general, it is true that the rougher the surface, the lower the surface quality.

In the first mould 70, the middle components 72a, 72b are designed to contact the portions of the circumferential surface 19 of the transverse element 10, mentioned in the preceding paragraph.

Consequently, the surface quality of the transverse element contact surface of the middle components 72a, 72b needs to meet higher requirements than the surface quality of the transverse element contact surface of the main component 71. It is also important that the occurrence of adhesion phenomena between the transverse element contact surface of the middle components 72a, 72b and the circumferential surface 19 of the transverse element 10 is limited as much as possible during the blanking process. For example, these conditions may be met by choosing a high-quality material such as hard metal for the middle components 72a, 72b. Another material which meets the conditions is high-speed steel. It is also possible that at least the transverse element contact surface of the middle components 72a, 72b is provided with a coating. In case of the middle components 72a, 72b comprising high-speed steel, it is even preferred to apply a coating to the middle components 72a, 72b.

Given the fact that less high demands are made on the transverse element contact surface of the main component 71, it is possible to choose a cheaper material for this main component 71, and to omit the coating of the transverse element contact surface.

It is clear from the preceding paragraph that it is possible to have an embodiment of the first mould 70 according to the present invention, wherein the main component 71 comprises high-speed steel.

Additionally, the transverse element contact surface of the main component 71 may be provided with a coating, for example the coating titanium nitrate (TiN), which is known in practice. The middle components 72a, 72b may comprise the same material as the main component 71, but may also comprise hard metal, for example. In view of the cutting quality, the latter option is advantageous.

In practice, under the influence of the forces prevailing during the blanking process, it may occur that material of the transverse element 10 to be formed is pushed in a seam between two adjacent mould components 71,72a, 72b, as a result of which a bulge is formed on the circumferential surface 19 of the transverse element 10. Preferably, the division of the first mould 70 in components and the associated positioning of the seams between the components is therefore chosen such that the possible bulges can not be formed on the carrying surfaces 16, the pulley sheave contact surfaces 17 or the retaining surfaces 23, but can only be formed on transition surfaces extending between a carrying surface 16 and a pulley sheave contact surface 17, and on portions of the circumferential surface 19 comprising both a top surface 24 and a transition surface extending between a retaining surface 23 and a top surface 24. In this way, damage of the carrying surfaces 16, the pulley sheave contact surfaces 17 and the retaining surfaces 23 as a result of the removal of the bulges during final processing of the transverse element 10 is prevented.

Figure 7 shows a top view of a mould 80 according to a second preferred embodiment of the present invention. For the sake of clarity, this mould 80 will hereinafter be referred to as second mould 80.

Compared to the first mould 70, the second mould 80 comprises two extra mould components, which will hereinafter be referred to as side basis components. One of the side basis components is indicated by reference numeral 73a in figure 7, whereas another of the side basis components is indicated by reference numeral 73b in figure 7.

The transverse element contact surface of each of these side basis components 73a, 73b is designed to contact, during the blanking process, a pulley sheave contact surface 17 of the transverse element 10 to be formed.

Preferably, seams which are present between the main component 71 and the side basis components 73a, 73b extend from portions of the inner surface 48 of the receiving space 46 of the second mould 80 which are designed to contact, during the blanking process, portions of the circumferential surface 19 of the transverse element 10 comprising both a transition surface between a pulley sheave contact surface 17 and the bottom surface 18 and a portion of said bottom surface 18. In this way, it is realized that possible bulges are formed only on such a transition surface or the bottom surface 18, and are not formed on a pulley sheave contact surface 17, so that damage of the pulley sheave contact surface 17 as a consequence of the removal of the bulges during final processing of the transverse element 10 is prevented.

In conformity with that which has been noted earlier, during the application of a transverse element 10 in a push belt 6 of a continuously variable transmission 1, the pulley sheave contact surfaces 17 of the transverse element 10 are in contact with pulley sheaves of a pulley 4,5. Usually, in view of obtaining a good contact, the pulley sheave contact surfaces 17 are provided with a relief having minuscule bulges. This relief is formed on the pulley sheave contact surfaces 17 when the transverse element 10 is moved in the receiving space 46 of the mould 70,80 during the blanking process. It will be clear that portions of the inner surface 48 of the receiving space 46 of the mould 70,80 which are designed to contact the pulley sheave contact surfaces 17 during the blanking process are provided with a relief that is suitable for realizing the desired relief on the pulley sheave contact surfaces 17. When the relief on the inner surface 48 of the receiving space 46 is worn out, it may be provided again, for example by means of grinding, unless the extent to which the relief is worn out is above a certain upper limit. In the second mould 80, the relief is present on the transverse element contact surfaces of the side basis components 73a, 73b. Therefore, in the case of wear, it is very easy to provide the relief again. The only steps which need to be taken for that purpose are removing the side basis components 73a, 73b, providing the relief in the transverse element contact surfaces of these components 73a, 73b again, and putting these components 73a, 73b back in place. If so desired, the worn out set of side basis components 73a, 73b can be replaced by a new set of side basis components 73a, 73b, so that the second mould 80 is instantly fit again to be applied for the purpose of a blanking process. When a durable material such as hard metal is applied for the side basis components 73a, 73b, the wearing process of the relief on the transverse element contact surfaces of the side basis components 73a, 73b will take place at a lower pace.

It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed above, but that several amendments and modification thereof are possible without deviating from the scope of the invention as defined in the appended claims.

Within the scope of the present invention, the mould 70,80 may be divided in different mould components 71,72a, 72b, 73a, 73b in any suitable way, wherein the number of mould components may be chosen freely. It is important that the mould components 71,72a, 72b, 73a, 73b are capable of jointly delimiting a receiving space 46, wherein transverse element contact surfaces of the mould components 71,72a, 72b, 73a, 73b are shaped such that an inner circumference of the receiving space 46 substantially corresponds to a circumference of the transverse element 10 to be formed.

In comparison with the manufacturing process of an undivided mould 45, the manufacturing process of the mould 70,80 having the mould components 71,72a, 72b, 73a, 73b is simple, because in the latter case, the relatively complex shape of the receiving space 46 is obtained by simply positioning the mould components 71,72a, 72b, 73a, 73b with respect to each other in the proper way.