PRESS BRAKE FOR BENDING SHEETS
The present invention relates to a press brake for bending metal sheets wherein: at least one stopper is disposed in each slot, each stopper comprising a first wedge having a first end secured to the first slot edge and a second end forming a first surface, and a second wedge having a first end secured to the second slot edge and a second end forming a first surface; and the first surface of at least one of the first and second wedges has a central portion that is domed or protuberant relative to the other portions of said surface so that the contact between the first and the second wedges is established essentially over said central portion.
Latest Amada Europe Patents:
The present invention relates to a bending press or “press brake” having tables with controlled deformation.
BACKGROUND OF THE INVENTIONBending presses are machine tools of a type that is itself well known. As shown in accompanying
A metal sheet or lamination F is placed on the bending matrices 18 of the lower table 12. The sheet F may be of a length that varies widely depending on the circumstances. Under drive from the pistons of the actuators V1 and V2, the punches 22 mounted on the upper table 14 move towards the sheet placed on the matrices of the lower table. As soon as the punch 22 comes into contact with the sheet F, force begins to increase within the sheet as the punch penetrates therein, initially in the elastic range and subsequently in the plastic range, thereby enabling the sheet to be bent permanently.
Because the force is applied to the upper table by the actuators V1 and V2 acting on the ends of the table, the linear load distributed between the two ends of the tables corresponds to the upper table being deformed along a line in the form of a concave arc with deformation maximas close to the midplane of the table. This means that, for bending purposes, at the end of bending, the central portions of the punches have penetrated into the sheet less than have the end portions. If bending were to be performed on a matrix that, itself, were to remain perfectly straight during bending, then the result would be that a workpiece would be obtained having a bend angle that was wider in its central portion than at its ends. Such a result is naturally unacceptable.
In order to remedy that drawback, various solutions have been proposed for the purpose of controlling these deformations at the edges of the tables by using various means in order to obtain a bend that is substantially identical over the entire length of the bent workpiece.
Conventionally, these solutions involve providing slots, such as the slots 24 and 26 shown in
With slots 24 and 26 of conventional type, i.e. that leave between them a slot-free portion 28 of length b, substantially parallel deformations are obtained for the edges of the upper and lower tables 14 and 12. This ensures that proper bending is achieved. Nevertheless, this result is obtained only when the metal lamination or sheet F for bending has a length that is substantially equal to the total length of the lower or upper tables 12 or 14. In contrast, when the length of the sheet F is less than the total length of the lower or upper table 12 or 14, both of the deformations of the lower and upper tables 12 and 14 are concave.
In addition to the difficulty of proposing a bending press that is suitable for enabling the metal lamination or sheet F for bending to be deformed substantially uniformly over the entire length of said lamination or sheet F, regardless of whether its length is short compared with the length of the tables 12, 14 of the press or, on the contrary, is equal to the length of the tables 12, 14 of the press, there exists an additional difficulty related to the top edges 24″, 26″ of the slots 24, 26 deforming while the bending force of the moving table 14 is being applied to the stationary table 12, and said force is being taken up on the bottom edges 24′, 26′ of the slots 24, 26.
OBJECT AND SUMMARY OF THE INVENTIONAn object of the present invention is to remedy these two problems by proposing to dispose at least one stopper in each of the slots 24, 26, which stopper is made up of two elements or wedges that have first surfaces fastened to respective ones of the edges of the slots, and second surfaces adapted for localized mutual contact substantially in the centers of the wedges, in a manner such as to ensure excellent transmission of the bending force from the top edges of the slots to the bottom edges of the slots.
The invention thus provides a press brake for bending at least one metal sheet, said press brake comprising:
-
- an upper table having a bottom edge carrying first bending tools, and a lower table having a top edge carrying second bending tools, the two tables being movable relative to each other to exert a bending force on the sheet;
said press brake presenting a vertical midplane, one of said tables having, through its entire thickness, two slots disposed symmetrically about the midplane, each slot having a first edge and a second edge, and an open first end opening out in a side edge of the table, as well as a closed end;
wherein:
at least one stopper is disposed in each slot, each stopper comprising a first wedge having a first end secured to the first slot edge and a second end forming a first surface, and a second wedge having a first end secured to the second slot edge and a second end forming a first surface; and
the first surface of at least one of the first and second wedges has a central portion that is domed or protuberant relative to the other portions of said surface so that the contact between the first and the second wedges is established essentially over said central portion.
The expression “secured to the first/second edge” is used to mean that the wedge in question is connected to the first or second edge, it being understood that said wedge may be movable relative to said edge of the slot.
Other characteristics of the press brake of the invention are indicated below:
-
- advantageously, the first surface of the first wedge and the first surface of the second wedge both have respective central portions that are domed or protuberant relative to the other portions of said first surfaces;
- in an embodiment, the first surface of the first wedge and/or the first surface of the second wedge is a convex surface;
- in an embodiment of the invention, the first surface of one of the wedges presents a concave surface while the first surface of the other wedge presents a convex surface;
- in an embodiment of the invention, the first surface of at least the first wedge and/or of the second wedge is a spherical surface portion;
- advantageously, at least in the zone of the stoppers, the slots present constant height so that the first edge and the second edge are parallel, in the absence of bending force for bending the metal sheet F;
- advantageously, the first surfaces of the wedges are inclined relative to the parallel edges of the slots;
- preferably, the first surfaces of the wedges are inclined at a slope lying in the range 1% to 40% and preferably in the range 5% to 10%, relative to an axis or a plane that is parallel to the edges of the slots;
- in an embodiment of the invention, the first surface of at least the first wedge or of the second wedge presents a plurality of inclined plane peripheral portions connecting to the central portion;
- the central portion presents a height or protrusion lying in the range 0.05 millimeters (mm) to 0.25 mm relative to the other portions of the first surface for a wedge of length substantially equal to 80 mm;
- advantageously, the wedges are mounted on supports connected to respective ones of the edges of the slots; at least one of the supports is movable laterally, i.e. along an axis parallel to the parallel edges of the slot on which it is mounted;
- in a possibility offered by the invention, the two wedges are offset relative to each other laterally, i.e. along an axis parallel to the parallel edges of the slot;
- in a possibility offered by the invention, in the absence of bending force for bending the metal sheet F, the first and second wedges present clearance between them; and
- advantageously, the press brake of the invention has a plurality of stoppers disposed in respective ones of the slots symmetrically about the midplane P′P.
Other characteristics and advantages of the invention appear more clearly on reading the following description of preferred embodiments of the invention given by way of non-limiting example. The description refers to the accompanying drawings, in which:
Each of the wedges 28, 29 is mounted on a respective support 40, 41 connected to a respective edge 24′, 26′ or 24″, 26″ of a respective one of the slots 24 and 26. The function of each wedge 28, 28′, 29, 29′/stopper 27 is to control the extent to which the edges 24′, 24″ and 26′, 26″ of each slot 24, 26 move towards each other when the bending force is applied. By controlling the extent to which the edges 24′, 24″ and 26′, 26″ of the slot 24 or 26 move towards each other, it is possible to control the deformation of the top edge 24″, 26″ of the slot 24, 26, and therefore the deformation of the top edge 12a of the lower table 12.
At least one of the supports 40 or 41, and optionally both of the supports 40 and 41 is/are mounted to move laterally, i.e. along an axis parallel to the parallel edges 24′, 26′ and 24″, 26″ of the slots 24, 26 on which it is mounted. In the example shown to illustrate the invention in
Naturally, it is possible to make provision for the set of actuators 60, or for a distinct drive mechanism, also to enable the supports 41 and thus the wedges 28 to move. By way of example,
In order to allow only limited lateral movement, the supports 40 are provided with slots or holes 62 that extend linearly to define the axes along which the moving supports 40 move, inside which slots guide pins 63 are disposed that are adapted to fit said slots 62. The movement of the supports 40 and of the wedges 29 is ideally parallel to the edges 24′, 26′ of the slots 24, 26. It should be noted that, advantageously, the edges 24′, 24″, and 26′, 26″ of each of the slots 24, 26 are parallel, at least at the wedges 28, 29/stoppers 27.
The first surface 28′, 29′ of each of the wedges 28, 29 advantageously has an inclination relative to the axes or to the planes of the parallel edges 24′, 26′ and 24″, 26″ of the slots 24, 26. This inclination of the first surface 28′, 29′ of each of the wedges 28, 29 lies in the range 1% to 30%, as a function of the material forming the wedges 28, 29, or more exactly of the coefficient of friction of the materials used to constitute the contact surface 28′, 29′ of each of the wedges 28, 29. Thus, by way of example, it can be noted that the inclination of each of the wedges 28, 29 shown in
In an essential aspect of the invention, at least one of the first surfaces, or contact surfaces, 28′, 29′ of the respective wedges 28, 29 is provided with a domed or protuberant central portion 30, 31 so that the contact between the first and the second wedges 28 and 29 is established essentially over said central portion 30 or 31.
This domed or protuberant central portion 30, 31 may be of various shapes and may be present on one of the two wedges 28 or 29 only, or on both of the wedges 28, 29. In addition, as explained below through the various embodiments, due to the shape of the domed or protuberant portion 30, 31 of each of the first surfaces 28′, 29′ of the wedges 28, 29, the contact between the wedges 28, 29 may consist of contact at a point or substantially at a point, of contact along a line, or of contact over an area.
In
In general, it should be noted that, by convention, the vertex of the domed or protuberant central portion 30, 31 is considered relative to a plane P0 joining two opposite edges 80, 81 of the wedge 28 or 29, which plane P0 corresponds to the inclination of the wedge 28, 29. The vertex S is the point of the domed or protuberant central portion 30, 31 that is at the furthest distance (“protrusion”) from the plane P0. This plane P0 is shown in
Once again, in these two
The embodiment of
In addition to the tapped orifices 71, 72, and 73 serving to fasten the wedge 28 or 29 to a support 40, 41,
The wedge 28, 29 shown in
In addition, the center O1 of the cylinder on which the first surface 28′ lies is closer to said surface 28′ than the center O2 of the cylinder on which the first surface 29′ lies. Thus, the radius of the cylinder of which the first surface 28′ forms a portion is smaller than the radius of the cylinder of which the first surface 29′ forms a portion. That is why only the vertex of the central portion 30 of the first surface 28′ comes into contact over the entire width of the first surface 29′ of the wedge 29, so that the contact between the two wedges 28, 29 is linear contact.
Naturally, the contact between the first surfaces 28′, 29′ that is described as being point contact or linear contact is the first contact during or at the beginning of application of the force F0 because, after this point or linear contact, the pressure from the top wedge 28 on the bottom wedge 29 is such that the first surfaces 28′, 29′ of the wedges 28, 29 enter at least an elastic deformation stage so that a contact zone that is larger is reached. While the force F0, e.g. a force of 200 kilonewtons (kN), is being applied, the contact zone is preferably approximately in the range 20% of the total area of each of the first surfaces 28′, 29′ of the wedges 28, 29 to 50% of said total area.
In accordance with a characteristic of the invention, the domed or protuberant central portion 30, 31 may include the center C of the first surface 28′, 29′ as the center of said central portion 30, 31 so that the protrusion of the domed portion 30, 31 coincides with the geometrical center of the first surface 28′, 29′ of the wedge 28, 29, but it is also possible to make provision for said domed or protuberant central portion 30, 31 to be offset slightly relative to the center C of the first surface 28′, 29′: such an embodiment is, for example, shown in
In a possible embodiment of the invention, the wedges 28, 29 are identical, i.e. their dimensions are mutually equal and their first surfaces 28′, 29′ are mutually identical, both in shape and in size.
However, it is also quite possible, as described for the various accompanying figures, for the two wedges 28, 29 not to be identical, i.e. essentially for their first surfaces 28′, 29′ not to be the same, and optionally for only one of the first surfaces 28′, 29′ of said wedges 28, 29 to have a domed or protuberant central portion 30, 31.
Claims
1. A press brake for bending at least one metal sheet, said press brake comprising:
- an upper table having a bottom edge carrying first bending tools, and a lower table having a top edge carrying second bending tools, the two tables being movable relative to each other to exert a bending force on the sheet;
- said press brake presenting a vertical midplane, one of said tables having, through the entire thickness thereof, two slots disposed symmetrically about the midplane, each slot having a first edge and a second edge, and an open first end opening out in a side edge of the table, as well as a closed end;
- at least one stopper being disposed in each slot, each stopper comprising a first wedge having a first end secured to the first slot edge and a second end forming a first surface, and a second wedge having a first end secured to the second slot edge and a second end forming a first surface; and
- the first surface of at least one of the first and second wedges having a central portion that is protuberant relative to the other portions of said surface so that the contact between the first and the second wedges is established essentially over said central portion.
2. A press brake according to claim 1, wherein said central portion of at least one of the first and second wedges is domed.
3. A brake press according to claim 1, wherein the first surface of the first wedge and the first surface of the second wedge both have respective central portions that are protuberant relative to the other portions of said first surfaces.
4. A press brake according to claim 3, wherein said respective central portions are domed.
5. A press brake according to claim 1, wherein the first surface of the first wedge and/or the first surface of the second wedge is a convex surface.
6. A press brake according to claim 1, wherein the first surface of one of the wedges presents a concave surface while the first surface of the other wedge presents a convex surface.
7. A press brake according to claim 1, wherein the first surface of at least the first wedge and/or of the second wedge is a spherical surface portion.
8. A press brake according to claim 1, wherein, at least in the zone of the stoppers, the slots present constant height so that the first edge and the second edge are parallel, in the absence of bending force for bending the metal sheet.
9. A press brake according to claim 8, wherein the first surfaces of the wedges are inclined relative to the parallel edges of the slots.
10. A press brake according to claim 9, wherein the first surfaces of the wedges are inclined at a slope lying in the range 1% to 40%, relative to an axis that is parallel to the edges of the slots.
11. A press brake according to claim 10, wherein said slope lies in the range 5% to 10% relative to the axis that is parallel to the edges of the slots.
12. A press brake according to claim 1, wherein the first surface of at least one of the first wedge and the second wedge presents a plurality of inclined plane peripheral portions connecting to the central portion.
13. A press brake according to claim 1, wherein the central portion presents a protruding height lying in the range 0.05 mm to 0.25 mm relative to the other portions of the first surface for a wedge of length substantially equal to 80 mm.
14. A press brake according to claim 1, wherein the wedges are mounted on supports connected to respective ones of the edges of the slots.
15. A press brake according to claim 14, wherein at least one of the supports is movable laterally, i.e. along an axis parallel to the parallel edges of the slot on which said movable support is mounted.
16. A press brake according to claim 1, wherein the two wedges are offset relative to each other laterally, i.e. along an axis parallel to the parallel edges of the slot.
17. A press brake according to claim 1, wherein, in the absence of bending force for bending the metal sheet, the first and second wedges present clearance between them.
18. A press brake according to claim 1, having a plurality of stoppers disposed in respective ones of the slots symmetrically about the midplane.
Type: Application
Filed: Mar 11, 2010
Publication Date: Sep 16, 2010
Applicant: Amada Europe (Tremblay)
Inventor: Bjarne Hansen (Pontvallain)
Application Number: 12/721,992
International Classification: B21D 5/00 (20060101);