The present invention relates to a press brake for bending a workpiece (a sheet metal) and a bending method.
An upper table that holds a punch tool (an upper tool) is provided so as to be vertically movable at an upper part of a main frame in a press brake, and the upper table extends in the lateral direction. A pair of elevating cylinders that elevate the upper table are provided at the upper part of the main frame, and the pair of elevating cylinders are separated in the lateral direction. Further, a lower table that holds a die tool (a lower tool) is provided at a lower part of the main frame, and the lower table extends in the lateral direction.
After a workpiece is positioned in the front-rear direction with respect to the die tool, the upper table is lowered by driving the pair of elevating cylinders. The workpiece is bent by corporation between the punch tool and the die tool, which results in the workpiece bent and shaped at a predetermined angle.
When the workpiece is bent, a bending load (a bending pressurizing force) by the elevating cylinders acts on the both ends of the upper table, but due to the influence of a reaction force from the workpiece, a lower surface of the upper table is deflected in a concave shape and an upper surface of the lower table is also deflected in a concave shape. In such a case, a closing interval (a vertical interval) between the upper table and the lower table is not uniform along the lateral direction. As a result, if the bending length of the workpiece is slightly shorter than or substantially the same as the total length of the lower table, the bending angle will not be constant along the bending length direction of the workpiece. Then, the “longitudinal accuracy (a degree of accuracy of the bending angle in the bending length direction of the workpiece)” is decreased.
In order to suppress the decrease in the longitudinal accuracy of the bending, a press brake has been developed that includes a pair of slits formed in a lower table for controlling deflection of the lower table (see Patent Literatures 1 and 2 below). The pair of slits extending in the lateral direction are formed in the lower table. The outer end portion of each slit is opened on the side surface of the lower table. As a result, the upper surface of the lower table is deflected in a convex shape to reduce the change in the closing interval between the upper table and the lower table in the lateral direction, thereby making it possible to suppress the decrease in the longitudinal accuracy.
In the press brake disclosed in Patent Literature 1, fixed blocks for adjusting the deflection of the lower table are respectively provided in the pair of slits that are formed in the lower table and opened at the lower table side edge. Further, in the press brake disclosed in Patent Literature 2, a coil spring for adjusting the deflection of the lower table is fixedly provided at the open end of the pair of slits that are opened at the lower table side edge.
Patent Literature 1: Japanese Patent Application Laid-Open Publication No. 2010-228004
Patent Literature 2: Japanese Patent Application Laid-Open Publication No. 2000-343125
The deflection state (curving state) at the time of bending the upper and lower tables in the press brake disclosed in Patent Literature 1 is schematically shown in
In the press brake disclosed in Patent Literature 1, for example, when the medium thickness plate is bent, as shown in
Further, when the thick plate is bent, as shown in
On the other hand, as described above, in the press brake disclosed in Patent Literature 2, the coil spring is fixedly provided at the open end of the slit. In other words, the deflection of the lower table is adjusted by providing the coil spring instead of the fixed block in the slit of Patent Literature 1. However, the press brake disclosed in Patent Literature 2 still has the above problem in the same manner as in Patent Literature 1.
That is, in the press brakes disclosed in Patent Literatures 1 and 2, the longitudinal accuracy of the bending is not sufficiently improved regardless of the thickness of the workpiece.
An object of the present invention is to provide a press brake and a bending method capable of bringing a closing interval between an upper table and a lower table close to a substantially uniform state along the lateral direction regardless of a thickness of a workpiece.
A first aspect of the present invention is to provide a press brake, which is equipped with an upper table provided so as to be vertically movable at an upper part of a main frame and configured to hold a punch tool on a lower side thereof, a lower table provided at a lower part of the main frame and including a pair of slits formed therein, the pair of slits extending symmetrically in a lateral direction, an end portion of each of the slits on an outer side in the lateral direction being opened, the lower table being configured to hold a die tool on an upper side thereof, and an elastic member provided at the end portion of each of the slits on the outer side in the lateral direction and configured to be switchable between a load-receiving state for receiving a bending load acting on the lower table and a released state in which the load-receiving state is released.
A second aspect of the present invention is to provide a bending method for bending a workpiece by cooperation between a punch tool and a die tool with use of the press brake described below, the bending method including, when a workpiece of a thin plate having a thickness of less than 1.2 mm is bent, putting the elastic member into the load-receiving state and putting the movable block into the first load-receiving state, as necessary. The press brake used here is the press brake according to the first aspect described above, which is further equipped with a movable block provided on an inner portion of each of the slits and movable in the lateral direction, in which the movable block includes a pair of a first load-receiving surface and a second load-receiving surface lined in the lateral direction to receive the bending load, and the movable block is configured to be switchable between a first load-receiving state and a second load-receiving state, the first load-receiving surface vertically facing an inner surface of the slit with a first clearance in the first load-receiving state, the second load-receiving surface vertically facing the inner surface of the slit with a second clearance smaller than the first clearance in the second load-receiving state.
Hereinafter, a press brake 10 according to the embodiment will be described with reference to
As shown in
An upper table 20 extending in the lateral direction is provided so as to be vertically movable at the upper part of the main frame 16. The upper table 20 holds the punch tool 12 on the lower side thereof so as to be able to be installed and removed via a punch holder 22 extending in the lateral direction. An elevating cylinder 24 is provided on the upper part of each side plate 18 as an elevating actuator for elevating the upper table 20. The pair of elevating cylinders 24 are separated from each other in the lateral direction. Further, a lower table 26 extending in the lateral direction is provided at the lower part of the main frame 16. The lower table 26 vertically faces the upper table 20. The lower table 26 holds the die tool 14 on the upper side thereof so as to be able to be installed and removed via a die holder 28 extending in the lateral direction. Note that instead of the hydraulic elevating cylinder 24, an elevating servomotor (not shown) may be used as the elevating actuator.
As shown in
Note that the slit 30 is not limited to the one including the outer horizontal portion 30a, the outer inclined portion 30b, and the like, and the shape of the slit 30 can be changed as appropriate. For example, the inner inclined portion 30d may be omitted, or another horizontal portion (not shown) may be arranged on the inner side of the inner inclined portion 30d in the lateral direction.
A fixed block 32 that receives a bending load acting on an upper portion 26u above the slit 30 of the lower table 26 is provided on the lower inner wall of the inner horizontal portion 30c of the slit 30. The fixed block 32 includes a flat load-receiving surface 32f for receiving the bending load described above. The load-receiving surface 32f vertically faces a flat surface 30ca on the upper inner wall of the inner horizontal portion 30c. In the present embodiment, a clearance AC between the load-receiving surface 32f and the flat surface 30ca (a clearance of the fixed block 32) is set to be, for example, 0.1 mm.
As shown in
The movable block 36 includes a pair of flat load-receiving surfaces (a first load-receiving surface 36f and a second load-receiving surface 36s) for receiving the bending load acting on the upper portion 26u. The height of the first load-receiving surface 36f is set to be lower than the height of the second load-receiving surface 36s. The movable block 36 is configured to be switchable between a first load-receiving state and a second load-receiving state by the movement thereof in the lateral direction. The first load-receiving state is a state in which the first load-receiving surface 36f vertically faces the flat surface 30cb described above (see
In the present embodiment, the first clearance BC1 is set to be larger than the clearance AC of the fixed block 32 described above (for example, 0.7 mm). The second clearance BC2 is set to be larger than the clearance AC of the fixed block 32 and smaller than the first clearance BC1 (for example, 0.4 mm).
Note that the fixed block 32 may be provided on the upper inner wall of the inner horizontal portion 30c instead of the lower inner wall thereof. In this case, the fixed block 32 receives the bending load acting on the upper portion 26u relative to the lower table 26. The load-receiving surface 32f vertically faces a flat surface (not shown) of the lower inner wall of the inner horizontal portion 30c. In the same manner, the movable block 36 may also be provided on the upper inner wall of the inner horizontal portion 30c instead of the lower inner wall thereof. In this case, the movable block 36 receives the bending load acting on the upper portion 26u relative to the lower table 26. The load-receiving surfaces 36f and 36s of the movable block 36 vertically face a flat surface (not shown) of the lower inner wall of the inner horizontal portion 30c.
As shown in
Note that instead of the first magnet 42 and the second magnet 44, two operation actuators (not shown) may be used as the first state holding portion and the second state holding portion. Each operation actuator includes a shot pin (not shown) that can be engaged in an engaging hole (not shown) formed in the movable block 36.
As shown in
A plurality of elastic members 54 that receive the bending load acting on the upper portion 26u are provided to the housing case 50 via a mounting shaft 56. The elastic members 54 are arranged along the front-rear direction. In other words, the housing case 50 houses the lower portions of the plurality of elastic members 54 lined in the front-rear direction. Each elastic member 54 is composed of a plurality of disc springs 58 laminated vertically, and can be elastically deformed in the vertical direction. Note that instead of the plurality of disc springs 58, a hard rubber such as an urethane rubber may be used as the elastic member 54.
On the upper side of the housing case 50, a cover member 60 that covers the upper parts of the elastic members 54 is provided so as to be vertically displaceable by means of a pair of fixing bolts 62 and a pair of fixing nuts 64. The cover member 60 extends in the front-rear direction. The fixing bolts 62 are inserted into insertion holes 60h formed in the front portion and the rear portion of the cover member 60, respectively, and their tips are screwed into screw holes 50v formed in the front portion and the rear portion of the housing case 50, respectively. The fixing bolts 62 are screwed into the fixing nuts 64 so as to fix the fixing bolts 62 to the housing case 50.
As shown in
A beveled portion 66c extending in the front-rear direction is formed on the inner side of the switching member 66 in the lateral direction. A finger hole 66h into which a finger of an operator is inserted is formed on the outer side of the switching member 66 in the lateral direction. An elongated hole 66v extending in the lateral direction is formed in the switching member 66. Further, a fixing screw member 70 for fixing the switching member 66 to the cover member 60 is screwed onto the upper surface of the cover member 60. The fixing screw member 70 is inserted through the elongated hole 66v. By tightening the fixing screw member 70, the switching member 66 is fixed to the cover member 60.
Subsequently, the operation (the bending method) of the punch press according to the present embodiment will be described. The bending method according to the present embodiment is a method of bending the workpiece W by the cooperation of the punch tool 12 and the die tool 14 with use of the press brake 10. Note that when the elastic member 54 is in the released state, the upper portion 26u of the lower table 26 is usually deflected downward, firstly at the both ends thereof that are easily deflected, as the bending load is increased. After that, the upper portion 26u comes into contact with the fixed block 32 and then comes into contact with the movable block 36 (the first load-receiving surface 36f or the second load-receiving surface 36s).
When the workpiece W of a medium thickness plate (thickness: 1.2 mm or more and less than 3.0 mm) is bent, as shown in Table 1 above, the elastic member 54 is put into the released state and the movable block 36 is put into the second load-receiving state. Specifically, when the medium thickness plate is bent and the bending length of the workpiece W is sufficiently longer than the total length of the lower table 26, the switching member 66 is moved to the outer side in the lateral direction so as to be separated from the gap G. As a result, the elastic member 54 is put into the released state. Further, the movable block 36 is moved to the outer side in the lateral direction so as to be put into the second load-receiving state.
The elastic member 54 is provided to suppress the deflection at the both ends of the lower table 26 when a thin plate having a long bending length is bent. Therefore, when the medium thickness plate is bent, the elastic member 54 is not required and thus put into the released state. When the medium thickness plate is bent, the bending load thereof is smaller than the bending load in the case of the thick plate. As a result, the deflection of the upper table 20 is smaller than the deflection in the case of the thick plate. In order to adjust the deflection of the lower table 26 in accordance with the deflection of the upper table 20, the movable block 36 is put into the second load-receiving state so that the clearance from the upper portion 26u of the lower table 26 is smaller (the second clearance BC2). As a result, as shown in
Note that when the medium thickness plate is bent and the bending length of the workpiece W is sufficiently shorter than the total length of the lower table 26, the elastic member 54 is put into the released state and the movable block 36 is put into the second load-receiving state as in the case in which the bending length of the workpiece W is long. (Detailed descriptions will be given later of the case in which the bending length of the workpiece W is sufficiently short, in addition to the case of the thin plate and the thick plate.)
When the workpiece W of a thin plate (thickness: less than 1.2 mm) is bent, as shown in Table 1 above, the elastic member 54 is put into the load-receiving state and the movable block 36 is put into the first load-receiving state, as necessary. Specifically, when the thin plate is bent and the bending length of the workpiece W is slightly shorter than or substantially the same as the total length of the lower table 26, the switching member 66 is moved to the inner side in the lateral direction so as to be inserted into the gap G. As a result, the elastic member 54 is put into the load-receiving state. Further, the movable block 36 is moved to the inner side in the lateral direction so as to be put into the first load-receiving state.
Since the elastic member 54 is provided to suppress the deflection at the both ends of the lower table 26 when a thin plate having a long bending length is bent, the elastic member 54 is put into the load-receiving state so as to be utilized for this purpose. In this case, since the bending load is also relatively small, the deflection of the lower table 26 is small and thus the movable block 36 is not involved in the bending. Therefore, the elastic member 54 may be in the first receiving state or the second receiving state. In the present embodiment, in order to safely eliminate the involvement of the movable block 36, the movable block 36 is put into the first load-receiving state in which the clearance from the upper portion 26u of the lower table 26 is large. As a result, as shown in
When a thin plate having a long bending length is bent, the deflection of the lower table 26 is controlled by the elastic member 54. Here, the upper portion 26u of the lower table 26 may or may not come into contact with the fixed block 32, depending on the bending load (the thickness of the thin plate). Further, even in the case of the thin plate, the bending load will change if the thickness thereof changes. In the present embodiment, the lower table 26 are elastically supported from below at the both ends thereof by the elastic member 54. Therefore, the deflection of the lower table 26 is variably adjusted in accordance with the thickness, that is, a relatively small bending load. As a result, the longitudinal accuracy is improved.
Note that even when the thin plate is bent, if the bending length of the workpiece W is sufficiently shorter than the total length of the lower table 26, the elastic member 54 is put into the released state and the movable block 36 is put into the second load-receiving state.
When the workpiece W of a thick plate (thickness: 3 mm or more) is bent, the elastic member 54 is put into the released state and the movable block 36 is put into the first load-receiving state. Specifically, when the thick plate is bent and the bending length of the workpiece W is slightly shorter than or substantially the same as the total length of the lower table 26, the switching member 66 is moved to the outer side in the lateral direction so as to be separated from the gap G. As a result, the elastic member 54 is put into the released state. Further, the movable block 36 is moved to the inner side in the lateral direction so as to be put into the first load-receiving state.
As described above, even when the thick plate is bent, the elastic member 54 is not required and thus put into the released state. When the thick plate is bent, the bending load thereof is larger than the bending load in the case of the medium thickness plate. As a result, the deflection of the upper table 20 is larger than the deflection in the case of the medium thickness plate. In order to adjust the deflection of the lower table 26 in accordance with the deflection of the upper table 20, the movable block 36 is put into the first load-receiving state so that the clearance from the upper portion 26u of the lower table 26 is larger (the first clearance BC1). As a result, as shown in
Note that even when the thick plate is bent, if the bending length of the workpiece W is sufficiently shorter than the total length of the lower table 26, the elastic member 54 is put into the released state and the movable block 36 is put into the second load-receiving state.
That is, when the bending length of the workpiece is short, the bending is performed at the center of the upper table 20 and the lower table 26. As a result, it is not necessary to suppress the deflection at the both ends of the lower table 26 by means of the elastic member 54. Therefore, when the bending length of the workpiece is short, the elastic member 54 is put into the released state for all of the thin plate, the medium thickness plate, and the thick plate. Further, when the bending length of the workpiece is short, it is not necessary to significantly deflect the lower table 26. Therefore, when the bending length of the workpiece is short, the movable block 36 is put into the second load-receiving state for all of the thin plate, the medium thickness plate, and the thick plate. As a result, the workpiece is stably bent at the center of the upper table 20 and the lower table 26.
As described above, in the present embodiment, the elastic members 54 are provided at the respective end portions on the outer side of the slit 30 in the lateral direction. The elastic member 54 is configured to be switchable between the load-receiving state for receiving the bending load acting on the lower table 26 (
Further, in the present embodiment, the movable block 36 is provided at the inner part of the slit 30. By switching the clearances (the first and second clearances) from the inner surface of the slit by means of the movable block under the released state of the elastic member 54, the deflection of the lower table 26 can be adjusted, thereby making it possible to improve the longitudinal accuracy of the medium thickness plate and the thick plate each having a long bending length.
Further, since the press brake 10 is provided with the switching member 66 for switching the elastic member 54 between the load-receiving state and the released state, the elastic member 54 can be easily switched.
Here, the press brake 10 is further provided with the housing case 50 for housing the elastic member 54 and the cover member 60 for covering the upper part of the elastic member 54. The housing case 50 and the cover member 60 can be attached to the press brake 10 so that the elastic member 54 can be easily switched by the housing case 50 and the cover member 60. Further, with this configuration, the elastic member 54 can be easily replaced.
Further, the cover member 60 is configured to be vertically displaceable with respect to the housing case 50. Therefore, in accordance with the elastic deformation of the elastic member 54 in the load-receiving state, the cover member 60 and the switching member 66 arranged above the elastic member 54 can be vertically displaced so as to reliably adjust the deflection of the lower table 26.
Note that the deflection of the upper table and the lower table in
The present invention is not limited to the description of the embodiments described above, and can be implemented in various aspects by making appropriate changes. Then, the scope of rights included in the present invention is not limited to the description of the embodiments described above.
The entire contents of Japanese Patent Application No. 2020-24127 (filed on Feb. 17, 2020) are incorporated herein by reference. Although the present invention has been described above by reference to the embodiments of the present invention, the present invention is not limited to the embodiments described above. The scope of the present invention is determined in light of the claims.
Number | Date | Country | Kind |
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2020-024127 | Feb 2020 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2021/004993 | 2/10/2021 | WO |