Lower tool with friction reduction device

Abstract

A lower tool for a bending machine, in particular die bending machine, includes a longitudinally extended base body, which has, on its bottom side, a tool shank for being received in a guide slot of a tool holder and optionally tool shoulders in the transverse direction, and at least one friction reduction device on the bottom side of the base body for reducing a frictional force between the bottom side and the tool holder in the event of a displacement of the lower tool in the longitudinal direction, wherein the at least one friction reduction device is configured such that a weight force of the lower tool acting on the tool holder, while applying a prestressing force in the direction of the weight force, causes a resulting normal force of the lower tool onto the tool holder that is lower relative to the weight force.

Claims

1. A lower die for a bending machine, comprising: a longitudinally extended base body extending along a longitudinal direction and comprising: a tool shank created as a one-piece unit with the base body and disposed on a bottom side of the base body for being received in a guide slot of a tool holder; tool shoulders formed by the bottom side of the base body and extending in a transverse direction to the longitudinal direction, wherein the tool shank is located between the tool shoulders and the tool shoulders are built to transfer vertically directed bending forces onto the tool holder, which vertically directed bending forces are generatable by the bending machine and are acting onto an upper side of the lower die; and a groove disposed on an upper side of the base body and having a V-shaped cross-section, the groove extending in the longitudinal direction; and at least one friction reduction device on the bottom side of the base body for reducing a frictional force between the bottom side of the base body and the tool holder in the event of a displacement of the lower die relative to the tool holder in the longitudinal direction and when no vertically directed bending forces are acting onto the upper side of the lower die, wherein the at least one friction reduction device is configured such that a weight force of the lower die acting on the tool holder, while a reactionary force is applied onto the lower die causes a resulting net force of the lower die onto the tool holder that is lower than the weight force, and wherein the at least one friction reduction device is arranged in a receiving space in the tool shoulders of the lower die such that the friction reduction device is configured so as to be movable with respect to the bottom side at least in the direction of the weight force.

2. The lower die according to claim 1, wherein the friction reduction device comprises an adjustable spring element for adjusting the reactionary force.

3. The lower die according to claim 1, wherein the reactionary force amounts to at least 20% of the weight force of the lower die.

4. The lower die according to claim 1, wherein the friction reduction device comprises a coating and the lower die further comprises a wear sensor connected to a system control, wherein the wear sensor is configured to monitor a minimum thickness of the coating of the friction reduction device.

5. The lower die according to claim 4, further comprising a wireless transmitter connected to the wear sensor for transferring wear data to the system control.

6. The lower die according to claim 1, further comprising a fixation means coupled to the lower die for securing the friction reduction device against falling out.

7. The lower die according to claim 1, further comprising a first side and a second side, wherein the friction reduction device is arranged so as to be aligned in a substantially vertical direction of loading and/or in a direction transverse to the substantially vertical direction of loading on the first side and the second side of the lower die.

8. The lower die according to claim 1, wherein the friction reduction device has a coating for contacting a surface of the tool holder.

9. The lower die according to claim 8, wherein the friction reduction device comprises a sliding element, wherein a friction coefficient of the coating with respect to the tool holder is lower than a friction coefficient of the lower die with respect to the tool holder.

10. The lower die according to claim 9, wherein the sliding element and/or the coating of the sliding element has slanted and/or rounded edges.

11. The lower die according to claim 9, further comprising two wedge planes which are oblique in the longitudinal direction and disposed within the receiving space, wherein the friction reduction device comprises a sliding wedge that is movable along said wedge planes, and wherein a friction coefficient of the sliding wedge with respect to the wedge planes is lower than a friction coefficient of the friction reduction device with respect to the tool holder sliding wedge.

12. The lower die according to claim 1, further comprising two wedge planes which are oblique in the longitudinal direction and disposed within the receiving space, and the friction reduction device comprises a roller having a roller axle configured to be movable along the wedge planes, and wherein the receiving space is delimited in the longitudinal direction by means of a stop, and wherein a friction coefficient of the roller axle with respect to the wedge planes is lower than a friction coefficient of the roller with respect to the tool holder and the friction coefficient of the roller with respect to the tool holder is greater than the friction coefficient of the lower die with respect to the tool holder.

13. A lower die for a bending machine, comprising: a longitudinally extended base body extending along a longitudinal direction and comprising: a tool shank created as a one-piece unit with the base body and disposed on a bottom side of the base body for being received in a guide slot of a tool holder; tool shoulders formed by the bottom side of the base body and extending in a transverse direction to the longitudinal direction, wherein the tool shank is located between the tool shoulders and the tool shoulders are built to transfer vertically directed bending forces onto the tool holder, which vertically directed bending forces are generatable by the bending machine and are acting onto an upper side of the lower die; and, a groove disposed on an upper side of the base body and having a V-shaped cross section, the groove extending in the longitudinal direction; and at least one friction reduction device on the bottom side of the base body for reducing a frictional force between the bottom side of the base body and the tool holder in the event of a displacement of the lower die relative to the tool holder in the longitudinal direction and when no vertically directed bending forces are acting onto the upper side of the lower die, wherein the at least one friction reduction device is configured such that a weight force of the lower die acting on the tool holder, while a reactionary force is applied onto the lower die, causes the weight force of the lower die to be transferred completely from the friction reduction device to the tool holder, and wherein the at least one friction reduction device is arranged in a receiving space in the tool shoulders of the lower die such that the friction reduction device is configured so as to be movable with respect to the bottom side at least in the direction of the weight force.

Description

(1) These show in a respectively very simplified schematic representation:

(2) FIG. 1 an example of a bending machine;

(3) FIG. 2 a schematic exploded view of a lower tool having friction reduction devices and tool holder;

(4) FIG. 3 a schematic representation of the general force ratio upon frictional contact of two bodies;

(5) FIG. 4 a schematic representation of an exemplary embodiment of a friction reduction device for applying a pretension with a sliding element;

(6) FIG. 5 a schematic representation of an exemplary embodiment of a friction reduction device for applying a pretension with a sliding wedge;

(7) FIG. 6 a schematic representation of an exemplary embodiment of a friction reduction device for applying a pretension with a roller.

(8) First of all, it is to be noted that in the different embodiments described, equal parts are provided with equal reference numbers and/or equal component designations, where the disclosures contained in the entire description may be analogously transferred to equal parts with equal reference numbers and/or equal component designations. Moreover, the specifications of location, such as at the top, at the bottom, at the side, chosen in the description refer to the directly described and depicted figure and in case of a change of position, these specifications of location are to be analogously transferred to the new position.

(9) In FIG. 1, a schematic representation of a bending machine 1 having a system control 22, an upper tool 2 and a lower tool 3 is shown, which is arranged on a tool holder 10. The schematic representation further shows the substantially vertical direction of loading 14 as well as the longitudinal direction 12, along which the lower tool 3 is to be displaceable in a guide slot 9 of the tool holder 10. Further, it can be seen that the transverse direction 13 is orthogonal to the longitudinal direction 12 and/or direction of loading 14.

(10) In FIG. 2, a schematic exploded view of a lower tool 3 having a base body 5 as well as tool shoulders 7 formed laterally in the transverse direction 13 can be seen. The base body 5 has a tool shank 8 for being received in the corresponding guide slot 9 of the tool holder 10. In FIG. 2, possible positions for the arrangement of the at least one friction reduction device 11 can be seen. As is shown schematically, multiple friction reduction devices 11 can be formed in the longitudinal direction 12 in receiving spaces 20, which are respectively provided therefor, on the bottom side 6 of the lower tool 3. Moreover, it is possible to provide a friction reduction device 11 on the bottom side 6 of the lower tool 3 in the tool shoulders 7. Friction reduction devices 11 arranged like this can, for support and/or an momentum compensation, be used for avoiding an unwanted tool jamming in the case of an eccentric, meaning arranged to deviate from a vertical axis of the tool holder, center of gravity of the lower tool 3.

(11) In FIG. 3, a schematic representation of the occurring force ratios of a lower tool 3, which contacts a tool holder 10, is shown. Usually, the estimate of a frictional force 15 can be performed using the product of the weight force 17 with a friction coefficient μ.sub.1 30 between the lower tool 3 and the tool holder 10. The displacement force 19 in the longitudinal direction 12 must be greater than the frictional force 15. As is evident from FIG. 3, the entire weight of the lower tool 3 normally weighs on a region of the tool holder 10 as weight force 17.

(12) The lower tool 3 according to the invention is explained with the aid of some schematic representations of FIGS. 4 to 6 in combination with FIGS. 2 and 3. In order to make the frictional force 15 between the bottom side 6 and the tool holder 10 possible in the case of a displacement of the lower tool 3 in the longitudinal direction 12, a prestressing force 16 is applied according to the invention in the direction of the weight force 17 by means of the friction reduction device 11. As can be seen schematically in FIG. 4, according to the invention, a friction reduction device 11 is arranged in a receiving space 20 of the lower tool 3. The weight force 17 of the lower tool 3, which force acts on the tool holder 10, is seemingly reduced to a resulting normal force 18 by the application of a prestressing force 16 by means of one friction reduction device 11 each, wherein the application of the weight force 17 takes place at least partially via the friction reduction device 11. As is shown schematically in FIGS. 4, 5 and 6, the dashed arrow of the weight force 17 can be reduced to the resulting normal force 18 by means of the prestressing force 16 which acts on the sliding element, a sliding wedge or a roller. The arrow lengths can be understood as a graphic illustration of the amount of the individual forces. Thus, a majority of the weight force 17 can be transferred to the tool holder 10 via the friction reduction device 11. The sliding element 26 shown in FIG. 4, is configured to be displaceable in the direction of the application of force and/or the direction of loading 14. The application of the prestressing force 16 to the sliding element 26 is carried out by a spring element 21 which is depicted, by way of example, as a spiral spring. A fixation means 25, which is depicted, by way of example, as a screw, allows for a clearance of the sliding element 26 in the direction of loading 14 and/or the longitudinal direction 12 while preventing a falling out of the friction reduction device 11 upon removal of the lower tool 3.

(13) As an optional possibility, the sliding element 26 is designed having a coating 27 in FIG. 4. Moreover, slanted edges of the coating 27 as well as of the sliding element 26 can be seen. Furthermore, it can be seen from FIG. 4 that a wear sensor 23 is arranged within the lower tool 3, such that at least one side of the sliding element 26 and/or of an optional coating 27 can be detected. Upon reaching a minimum thickness of the sliding element 26 and/or the coating 27, a signal can be sent, preferably by means of a wireless transmission device 24, to a system control 22.

(14) For the ease of understanding, the principle according to the invention is briefly explained by reference to the following calculation example of the frictional force 15, F.sub.R, on the basis of exemplary values and is to be understood analogously for all exemplary embodiments in combination with FIG. 1 to FIG. 6: weight force 17 of the lower tool 3=F.sub.G=200 N; prestressing force 16 of two friction reduction devices 11=F.sub.V: 50N+50 N=100 N; resulting normal force 18=F.sub.N=F.sub.G−F.sub.V=100 N; friction coefficient μ.sub.1 30 between lower tool and tool holder 30=0.5; friction coefficient μ.sub.2 31 between friction reduction device and tool holder=0.2.

(15) Normally, the frictional force 15 is equivalent to F.sub.R=μ.sub.1*F.sub.G=0.5*200 N=100 N, whereby a displacement force 19 of more than 100 N is necessary for displacing the lower tool 3. Assuming, in a simplified manner, that the reduction of the weight force 17 F.sub.G=200 N by the prestressing force 16 F.sub.V=100 N to a resulting normal force 18 by means of the friction reduction device 11 according to the invention is carried out by F.sub.N=F.sub.G−F.sub.V=200 N−100 N=100 N, the occurring frictional force 15 of the overall system, and thus the required displacement force 19, can be reduced. The total frictional force F.sub.R-Sum can be estimated by putting together the component frictional forces of the lower tool F.sub.R1 and of the sliding element F.sub.R2. Therefore, the following applies:
F.sub.R-Sum=F.sub.R1+F.sub.R2=μ.sub.1*F.sub.N+μ.sub.2*F.sub.V=0.5*100N+0.2*100N=70N.

(16) In a specific example, this means that using two friction reduction devices 11, each of them applying a prestressing force 16 of 50 N, which is equivalent to 25% of the weight force 17 of the lower tool 3, that a reduction of the required frictional force 15 of 30% occurs. This example merely serves for illustrating the approach and the advantage of the lower tool 3 according to the invention, in particular the friction reduction device 11 formed and arranged according to the invention. With the aid of this simple example of the sliding element 26, it is possible for the person skilled in the art to transfer the necessary conclusions for the calculation and interpretation analogously to a sliding wedge 29 and/or a roller 35, which is why a detailed discussion is refrained from at this point.

(17) In FIG. 5, a further and potentially independent embodiment of a lower tool having a friction reduction device in the form of a sliding wedge 29 is shown. In FIG. 5a, the sliding wedge 29 is in the rest position and the lower tool 3 rests on the tool holder 10. Analogously to the description of the previously explained functional principle, a prestressing force 16 is applied, by means of the spring element 21, to the tool holder 10 via the sliding wedge 29. This leads to the reduction of the resulting normal force 18 relative to the weight force 17 of the lower tool 3. The sliding wedge 29 is configured to be movable in the longitudinal direction 12 and the direction of loading 14 within the receiving space 20. The sliding wedge has a friction coefficient μ.sub.3 32 on the wedge planes 28 with respect to the lower tool. The friction coefficient between the coating 27 of the sliding wedge 29 to the tool holder 10 is shown as μ.sub.2 31. The friction coefficient between the lower tool 3 and the tool holder 10 is shown as μ.sub.1 30. Analogously to the description and the functionality of FIG. 4, a wear sensor 23 and a wireless transmission device 24 are schematically depicted and are not further explained with reference to the aforementioned discussion.

(18) In FIG. 5b, a displacement of the lower tool in the longitudinal direction 12 is adumbrated. The application of the weight force 17 takes place on the wedge plane 28 on one side of the sliding wedge 29 as well as via the spring element 21 in the direction of the tool holder 10. As can be seen from FIG. 5b, the resulting normal force 18 can constitute a comparatively small proportion of the weight force 17. In a special case, it is possible that the entire weight force 17 is transferred to the tool holder 10 via the friction reduction device 11. Such a case can arise when the friction coefficient μ.sub.3 32 is significantly lower than the friction coefficient μ.sub.2 31 and μ.sub.1 30. In the case of a displacement in the longitudinal direction 12 this can lead to the lower tool 3 being lifted due to the lower tool 3 sliding along on the wedge planes 28 on the sliding wedge 29. In this regard, the sliding wedge 29 has beveled upper sides which correspond with the wedge planes 28 in the depicted form. This way, a damage to the lower tool 3 and/or the tool holder 10 is avoided.

(19) In FIG. 6, a further and potentially independent embodiment of a lower tool 3 having a friction reduction device 11 in the form of a roller 35 is shown. Again, equal reference numbers are used for equal parts as in the preceding FIGS. 1 to 5. In order to avoid unnecessary repetitions, it is pointed to/reference is made to the detailed description in FIG. 1 to FIG. 5 preceding it. In FIG. 6a, the rest position of the friction reduction device 11 and/or of the lower tool 3 is schematically depicted. The depicted roller 35 has a coating 27 in the radial direction. In this regard, the roller 35 is configured to be movable in the longitudinal direction 12 and the direction of loading 14 within the receiving space 20. The receiving space 20 is extended to the top, against the direction of loading 14, such that the roller 35 is movable freely around the roller axle 34. The roller axle 34 always contacts, in the transverse direction 13 the wedge 30 plane 28, In this regard, the coating 27 of the rollers 35 is configured to be resilient. However, it is also conceivable to configure the roller body to be resilient, whereby a coating 27 would be avoidable. In the case of a depicted roller 35 with a coating 27, said coating 27 and/or the roller body can function as a spring element 21. In this manner, a prestressing force 16 is applied analogously to the exemplary embodiments discussed above, whereby the weight force 17 of the lower tool 3 is reduced to the resulting normal force 18. Between the roller axle 34 and the lower tool 3, the frictional force 15 is determined locally by the friction coefficient μ4 33 and the proportion of the abutting weight force 17 of the lower 5 tool 3, As can be seen in FIG. 6a, the roller 35, in the static case, is arranged at a vertex of the receiving space 20 between the wedge planes 28 due to a self-centering effect. The receiving space 20 is delimited in the longitudinal direction 12 by a stop 36.

(20) Analogously to the exemplary embodiments discussed above, a wear sensor 23 as well as a transmission device 24 is schematically adumbrated in FIG. 6. A repetition of the functionality is forgone here with reference to the discussion in FIGS. 4 and 5.

(21) In FIG. 6b, the situation of the friction reduction device 11 during a longitudinal displacement is schematically depicted. In the event of the longitudinal displacement of the lower tool 3, a displacement of the roller axle 34 along the wedge plane 28 is caused, whereby the proportion of the prestressing force 16 relative to the resulting normal force 18 increases. In the borderline case, it is possible that the lower tool 3 is lifted in the contacting region with the tool holder 10. In this case, the lower tool 3 is fully supported on the tool holder 10 via the roller axle 34 and the roller 35. The low rolling resistance during the longitudinal displacement results in a reduction of the displacement force 19 and an effective reduction of the weight force 17 of the lower tool 3, which force acts on the tool holder 10. Upon reaching a target position in the longitudinal direction 12 on the tool holder 10, the roller can automatically assume the rest position between the wedge planes 28 due to the very low friction coefficients μ.sub.4 33 relative to the friction coefficients 1 30 and/or μ2 31. This becomes possible due to the resiliently formed roller 35 and/or the resilient coating 27. The affixing of the fixation means 25, which can be affixed to the lower tool 3 from the bottom side 6 for example by means of a flap for fixating the roller axle 34, is not depicted.

(22) All exemplary embodiments of FIGS. 4 to 6 are based on the inventive idea to reduce the weight force 17 of the lower tool 3 acting on the tool holder 10 to a resulting normal force 18 by applying a prestressing force 16 in the direction of the weight force 17 by means of the at least one friction reduction device 11. In certain cases, however, it may be advantageous that the amount of the prestressing force 16 is selected to be higher than the weight force 17 of the lower tool 3. In doing so, a complete transfer of the weight force 17 to the tool holder 10 can take place via the friction reduction device 11. This is possible, on the one hand, by adjusting the prestressing force 16 by means of spring element 21 (see especially FIG. 4), or, alternatively, it can be carried out by the lower tool 3 being supported on the wedge planes 28 during the longitudinal displacement of the lower tool 3 as is adumbrated in FIGS. 5 and 6.

(23) The exemplary embodiments show possible embodiment variants, and it should be noted in this respect that the invention is not restricted to these particular illustrated embodiment variants of it, but that rather also various combinations of the individual embodiment variants are possible and that this possibility of variation owing to the teaching for technical action provided by the present invention lies within the ability of the person skilled in the art in this technical field.

(24) The scope of protection is determined by the claims. However, the description and the drawings are to be adduced for construing the claims. Individual features or feature combinations from the different exemplary embodiments shown and described may represent independent inventive solutions. The object underlying the independent inventive solutions may be gathered from the description.

(25) All indications regarding ranges of values in the present description are to be understood such that these also comprise random and all partial ranges from it, for example, the indication 1 to 10 is to be understood such that it comprises all partial ranges based on the lower limit 1 and the upper limit 10, i.e. all partial ranges start with a lower limit of 1 or larger and end with an upper limit of 10 or less, for example 1 through 1.7, or 3.2 through 8.1, or 5.5 through 10.

(26) Finally, as a matter of form, it should be noted that for ease of understanding of the structure, elements are partially not depicted to scale and/or are enlarged and/or are reduced in size.

(27) TABLE-US-00001 List of reference numbers 1 bending machine 2 upper tool 3 lower tool 4 tool holder surface 5 base body 6 bottom side 7 tool shoulder 8 tool shank 9 guide slot 10 tool holder 11 friction reduction device 12 longitudinal direction 13 transverse direction 14 direction of loading 15 frictional force 16 prestressing force 17 weight force 18 resulting normal force 19 displacement force 20 receiving space 21 spring element 22 system control 23 wear sensor 24 transmission device 25 fixation means 26 sliding element 27 coating 28 wedge plane 29 sliding wedge 30 friction coefficient μ-1 31 friction coefficient μ-2 32 friction coefficient μ-3 33 friction coefficient μ-4 34 roller axle 35 pulley 36 stop