EP3181343B1

EP3181343B1 - Hydraulic actuating device for a press

Info

Publication number: EP3181343B1
Application number: EP16382532.6A
Authority: EP
Inventors: Luis DEL TESO DÍEZ; Kepa ARAMBARRI ARREGUI
Original assignee: Nitrogas S A U; Nitrogas Sau
Current assignee: Nitrogas S A U; Nitrogas Sau
Priority date: 2015-12-14
Filing date: 2016-11-15
Publication date: 2018-09-05
Anticipated expiration: 2036-11-15
Also published as: EP3181343A1; ES2686989T3

Description

TECHNICAL FIELD

The present invention relates to press-driven folding units or transverse punching units.

PRIOR ART

The use of hydraulic assemblies comprising at least two hydraulic cylinders along with presses has become increasingly widespread due to their flexibility. Assemblies of this type comprise a vertical cylinder which is actuated by a moving part of a press (generally an upper die fixed to the press), causing the vertical movement of a rod of said cylinder with said actuation. This movement in turn causes actuation of a second cylinder of the assembly which is fluidically communicated with the former. The second cylinder causes actuation of a specific tool to perform the desired operation. This allows, among others, using a plurality of assemblies (or one or more assemblies with more than one cylinder of the mentioned second cylinder type) actuated with one and the same moving part of the press, which allows a plurality of simultaneous actuations with one and the same movement (actuation of the moving part).
However, if the moving part acts on the cylinder with excessive force, there is a risk of at least said cylinder (or even the entire assembly) breaking or exploding.
Patent document EP1057550A2 discloses an actuator of this type, said actuator comprising a hydraulic assembly with two fluidically communicated cylinders. The first hydraulic cylinder comprises a fixed casing and a rod which moves between a passive position and an active position, as a result of the actuation of the moving part. The hydraulic cylinder comprises a first chamber with a fluid therein delimited between the rod and the casing, and the rod is formed by a sleeve receiving the blow from the press, a piston, and a second chamber defined between the piston and the sleeve and comprising therein a fluid at a specific pressure. This pressure is used for calibrating the maximum external force the cylinder supports (cylinder rating), such that the piston moves towards the press only if the pressure of the fluid in the first chamber exceeds the pressure of the fluid in the second chamber. The cylinder itself thereby comprises a safety mechanism which prevents it from breaking down when it supports an external force exceeding its rated maximum force (at least for a small margin).
Another hydraulic actuating device is known from DE 9405764 U1 .

DISCLOSURE OF THE INVENTION

The object of the invention is to provide a hydraulic actuating device for a press, as described below.
The hydraulic actuating device of the invention is adapted for use in presses. The device comprises a hydraulic actuator, a working cylinder and a conduit fluidically communicating the hydraulic actuator and the working cylinder to one another. The hydraulic actuator comprises a casing, a rod which moves between a passive position and an active position, and a chamber delimited between the rod and the casing, and the working cylinder comprises a casing, a rod which moves between a passive position and an active position, and a chamber delimited between the rod and the casing. The conduit fluidically communicates the chamber of the hydraulic actuator with the chamber of the working cylinder.
The device further comprises an actuating cylinder adapted for being fixed to a moving part of the press, specifically to an upper die that is fixed to the press, such that when fixed to the press it acts on the rod of the hydraulic actuator as a result of the movement of the moving part towards the hydraulic actuator.
The actuating cylinder comprises an interchangeable actuating element arranged facing the rod of the hydraulic actuator when said actuating cylinder is fixed to the moving part of the press. Said actuating element comprises a weakening area rated at a specific maximum force, such that when the press, through the moving part, causes the actuating cylinder to act on the hydraulic actuator with a force equal to or greater than said specific maximum force of the weakening area, said weakening area breaks, the external force to be supported by the hydraulic actuator being at least partially reduced.
In this manner, the hydraulic cylinder which must support the action of the press is assured to a greater extent, without making its design more complex, since if the force set as the maximum force exerted by the press that can be supported by said hydraulic cylinder is exceeded, additional safety means (the actuating cylinder with the actuating element) are added to prevent said excess force (at least in part) from being transferred to said hydraulic cylinder (said excess force is "absorbed" by said means).
These and other advantages and features of the invention will become evident in view of the drawings and the detailed description of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a section-view of one embodiment of the device of the invention.
Figure 2 is a section-view of the assembly of the device of Figure 1 formed by the hydraulic actuator and the working cylinder.
Figure 3 is a section-view of the actuating cylinder of the device of Figure 1.

DETAILED DISCLOSURE OF THE INVENTION

Figure 1 shows an embodiment of the hydraulic actuating device of the invention. The device comprises a hydraulic actuator 1, a working cylinder 2 and a conduit 3 fluidically communicating the hydraulic actuator 1 with the working cylinder 2, forming a hydraulic assembly 9. As shown in Figure 2 by way of example, the hydraulic actuator 1 comprises a casing 10, a rod 11 which can be moved between a passive position shown in said Figure 2 and an active position (representing the maximum movement of said rod 11 in a direction of movement Y1), and a chamber 12 delimited between the rod 11 and the casing 10. When the device is installed, the rod 11 is arranged facing a moving part 1001 of a press, such that when the moving part 1001 moves towards the hydraulic actuator 1 it acts on the rod 11, causing the movement thereof from the passive position towards the active position. The hydraulic actuator 1 is preferably arranged in a vertical position (the rod 11 is arranged vertically, the direction of movement Y1 being vertical), facing the moving part 1001 of the press.
The working cylinder 2 in turn comprises a casing 20, a rod 21 which can be moved between a passive position shown in said Figure 2 and an active position (representing the maximum movement of said rod in a direction of movement X), and a chamber 22 delimited between the rod 21 and the casing 20. The working cylinder 2 is preferably arranged in a horizontal position, perpendicular to the hydraulic actuator 1 (the rod 21 is arranged horizontally, the direction of movement X being horizontal). The conduit 3 fluidically communicates the chamber 12 of the hydraulic actuator 1 with the chamber 22 of the working cylinder 2. The hydraulic actuator 1 and the working cylinder 2, as well as the conduit 3, can be housed in one and the same body 90, forming the hydraulic assembly 9.
The moving part 1001 preferably is an upper die that is fixed to the press, and the hydraulic assembly 9 is fixed to a corresponding lower die that is also fixed in the press and not depicted in the drawings.
The moving part 1001 moves both ways in an actuating direction Y2 towards the hydraulic actuator 1 and away from the hydraulic actuator 1 during its normal operation, and when it is moved towards the hydraulic actuator 1, it pushes the rod 11 of said hydraulic actuator 1. Said pushing causes the movement of said rod 11 in a direction of movement Y1, and with said movement the rod 11 in turn pushes the fluid present in the chamber 12. Said fluid in turn pushes the rod 21 of the working cylinder 2, as a result of the conduit 3, such that said rod 21 moves in the direction of movement X when it is pushed by said fluid. Since the rod 21 moves in the direction of movement X, said rod 21 causes the required final actuation (punching a sheet facing the rod 21, for example, by means of an appropriate tool 8 fixed to an end of said rod 21). When the moving part 1001 moves away from the hydraulic actuator 1, the fluid tends to return to its original position, causing the movement of the rods 11 and 21 in directions opposite to Y1 and X, respectively.
The pressure of the chamber 12 increases as the rod 11 moves. The movement of the moving part 1001 is controlled so that it does not cause movements of the rod 11 which cause a specific pressure in said chamber 12 to be exceeded, but sometimes a movement of the rod 11 that causes higher pressures in said chamber 12 is caused accidentally (for example, by an erroneous control of the movement of the moving part 1001, lack of control of the movement thereof or the unintentional omission of an element, such as a tool, for example, between the hydraulic actuator 1 and the moving part 1001). If this occurs, the hydraulic actuator 1 can be irreversibly damaged, and more serious still, can even explode causing major damage to the surroundings (and to the people in the surroundings). To prevent this situation, the hydraulic actuator 1 usually has an integrated safety mechanism. Said mechanism involves rating the external force to be supported by the hydraulic actuator 1, which causes a higher pressure in the chamber 12. Said hydraulic actuator 1 is therefore provided with an additional travel margin, and said hydraulic actuator 1 is capable of absorbing excess external force.
The device of the invention comprises an actuating cylinder 4 adapted for being fixed to the moving part 1001 of the press, such that when it is fixed to the moving part 1001, said actuating cylinder 4 acts against the rod 11 of the hydraulic actuator 1 as a result of a movement of said moving part 1001 towards said hydraulic actuator 1. The moving part 1001 preferably comprises a housing for housing the actuating cylinder 4 at least partially when said actuating cylinder 4 is fixed to said moving part 1001. As shown in Figure 3 by way of example, the actuating cylinder 4 comprises an interchangeable actuating element 43 which is arranged facing said rod 11 when the actuating cylinder 4 is fixed to the moving part 1001, and said actuating element 43 comprises a weakening area 43a rated at a specific maximum force (it supports, at most, said force before breaking). The specific maximum force is set depending on the maximum working force allowable for the device.
In this manner, if the moving part 1001 causes the rod 11 to travel beyond what is initially allowed for said rod 11, the actuating element 43 breaks at the weakening area 43a, and complete breaking of the actuating cylinder 4 and the hydraulic actuator 1 is prevented. Sometimes, due to the unintentional omission of external elements (tools, for example) on the hydraulic actuator 1 or an excessive movement of the moving part 1001 of the press towards said hydraulic actuator 1, for example, excess external force is exerted on the hydraulic cylinder 1 which can damage it if its rated maximum external force is exceeded. The maximum external force is set depending on the pressure of the fluid inside the chamber 12 and on the diameter of said chamber 12, for example. The risk of this occurring is reduced with the actuating cylinder 4 which comprises the actuating element 43, since said actuating element 43 is caused to break first, and the moving part 1001 can therefore travel a little bit more towards the rod 11 without translating said movement to said rod 11.
If the moving part 1001 falls in an uncontrolled manner, the hydraulic cylinder 1 will be affected, but in other circumstances like those mentioned above, for example, the margin obtained as a result of the actuating cylinder 4 may be enough to assure that the hydraulic actuator 1 does not break. Furthermore, despite having added an actuating cylinder 4, said actuating cylinder 4 is not excessively affected either, since in these cases only the actuating element 43 itself breaks. Said actuating element 43 is interchangeable, such that the correct operation of the device can be recovered by simply replacing the broken element 43 with another element in good condition. The maintenance cost is therefore very low compared to cases in which the hydraulic actuator 1 must be replaced, for example. The actuating cylinder 4 can be incorporated in devices comprised in hydraulic assemblies 9 without the additional integrated mechanism, or even in devices comprised in hydraulic assemblies 9 with the safety mechanism integrated in the hydraulic actuator 1.
The actuating element 43 is hollow, the minimum width 43b of the solid surrounding the hollow defining the weakening area 43a. Preferably, the actuating element 43 is substantially cylindrical and hollow, said hollow comprising a homogenous width (although it may not be a homogeneous width). In one area of said hollow the thickness of the actuating element 43 decreases (the width of the solid surrounding the hollow decreases or the width of the cavity increases), the area of the actuating element 43 comprising a smaller thickness being the weakening area 43a.
The actuating cylinder 4 comprises a sleeve 40 adapted for being fixed to the moving part 1001 of the press, an attachment piece 44 fixed to the sleeve 40 and adapted for being fixed to the moving part 1001 of the press, the sleeve 40 being attached to said moving part 1001 by means of said attachment piece 44, and a rod 41 movable with respect to said sleeve 40, between a passive position and an active position, and projecting from the sleeve 40. The actuating element 43 is attached to the end of the rod 41 projecting from the sleeve 40, such that said actuating element 43 contacts the rod 11 and pushes it, causing the movement of the rod 21 in the actuating direction X, as explained above.
The actuating cylinder 4 can further comprise an additional safety mechanism. Said actuating cylinder 4 can comprise an additional rod 41', a first chamber 42' delimited between both rods 41 and 41', and a second chamber 44' delimited between the additional rod 41' and the sleeve 40. When an additional movement is going to be caused, first the rods 41 and 41' move in response compressing the second chamber 44'. When the pressure of the fluid in the second chamber 44' reaches the rated limit pressure of said second chamber 44', said pressure exceeds the pressure of the fluid in the first chamber 42' and the rod 41 moves towards the additional rod 41', the first chamber 42' being compressed. When both pressures become leveled off, the first rod 41 stops moving, and the weakening area 43a is designed to break at that time.
In this manner, as a result of the actuating cylinder 4 the safety margin of the device is significantly increased as a result of the two chambers 42' and 44', the two rods 41 and 41', and the weakening area 43a.

Claims

Hydraulic actuating device for a press, comprising a hydraulic actuator (1), a working cylinder (2) and a conduit (3) fluidically communicating the hydraulic actuator (1) and the working cylinder (2), the hydraulic actuator (1) comprising a casing (10), a rod (11) which moves between a passive position and an active position, and a chamber (12) delimited between the rod (11) and the casing (10), the working cylinder (2) comprising a casing (20), a rod (21) which moves between a passive position and an active position, and a chamber (22) delimited between the rod (21) and the casing (20), and the conduit (3) fluidically communicating the chamber (12) of the hydraulic actuator (1) with the chamber (22) of the working cylinder (2), characterized in that the device further comprises an actuating cylinder (4) adapted for being fixed to a moving part (1001) of the press, such that when fixed to the moving part (1001) it acts on the rod (11) of the hydraulic actuator (1) as a result of the movement of said moving part (1001) towards the hydraulic actuator (1), the actuating cylinder (4) comprising an interchangeable actuating element (43) arranged facing the rod (11) of the hydraulic actuator (1) when said actuating cylinder (4) is fixed to the moving part (1001), and said actuating element (43) comprising a weakening area (43a) rated at a specific maximum pressure, such that when the moving part (1001) causes the actuating cylinder (4) to act on the hydraulic actuator (1) with a pressure equal to or greater than the specific determined maximum pressure of the weakening area (43a), said weakening area (43a) breaks, the pressure to be supported by the hydraulic actuator (1) being reduced.
Device according to claim 1, wherein the weakening area (43a) is rated below the rated maximum pressure of the hydraulic actuator (1).
Device according to claims 1 or 2, wherein the actuating element (43) is hollow, the width of the cavity defining the weakening area (43a).
Device according to claim 3, wherein, in the weakening area (43a), the part of the actuating element (43) surrounding the cavity of said actuating element (43) comprises a smaller width than the rest of the actuating element (43) surrounding said cavity, such that the actuating element (43) has a smaller thickness (43b) in said weakening area (43a).
Device according to claim 3, wherein in the weakening area (43a) the cavity comprises a larger width than in the rest, such that the actuating element (43) has a smaller thickness (43b) in said weakening area (43a).
Device according to any of the preceding claims, wherein the actuating cylinder (4) comprises a sleeve (40) adapted for being fixed to the moving part (1001) of the press and a rod (41) movable with respect to said sleeve (40) between a passive position and an active position, projecting from the sleeve (40), the actuating element (43) being attached to the end of the rod (41) projecting from said sleeve (40), said actuating element (43) projecting from said rod (41).
Device according to claim 6, wherein the actuating cylinder (4) comprises an attachment piece (44) fixed to the sleeve (40) and adapted for being fixed to the moving part (1001) of the press, the sleeve (40) being attached to said moving part (1001) by means of said attachment piece (44).
Device according to claim 6 or 7, wherein the actuating cylinder (4) comprises an additional rod (41'), a first chamber (42') delimited between both rods (41, 41') of the actuating cylinder (4), and a second chamber (44') delimited between the additional rod (41') and the sleeve (40).
Device according to claim 8, wherein both chambers (42', 44') of the actuating cylinder (4) comprise a fluid therein, the second chamber (44') being rated at a lower pressure than the first chamber (42'), and said first chamber (42') being rated at a lower pressure than the weakening area (43a).