DEVICE AND METHOD FOR CONTROLLING THE PRIMARY DRIVE OF A FINE BLANKING PRESS

Abstract

In an apparatus and a method for controlling the primary drive of a hydraulically driven fine blanking press, the hydraulic circuit is simplified due to the elimination of hydraulic tubes, and the amount of hydraulic fluid is reduced, while increasing the number of strokes and achieving a simple design for the press.

Claims

1. A apparatus for controlling the primary drive of a hydraulically driven fine blanking press, comprising a main cylinder chamber, which is disposed in a base and in which a main piston guided, pressure chambers, for the main piston configured to act upon the piston with hydraulic fluid so that the piston carries out a stroke movement between a lower dead point UT and and an upper dead point OT, a table supported by the main piston, double-acting fast stroke pistons which are guided in fast stroke cylinders and include piston rods, pressure chambers for the fast stroke pistons configured to act upon the pistons with hydraulic fluid, the piston rods being configured to engage the table for the rapid approach stroke of the main piston and the table, and a hydraulic system, which includes at least one hydraulic pump unit, configured to supply the pressure chambers with hydraulic fluid that is set by a central control unit to a predetermined working pressure, wherein the main piston comprises disk shaped protruding working surfaces partitioning the main cylinder chamber into a first pressure chamber above second pressure chambers fluid channels and second fluid channels in the base opening into the first and second pressure chamber respectively and being connected to the hydraulic system, bypass channels in the base connecting the first fluid channels to the second fluid channels, the bypass channels together with the first and second fluid channels and the first and second pressure chambers comprising the hydraulic system, by pressure-controlled proportional valves, the central control unit being configured to open the proportional valves during rapid approach of the table to the OT during which displacement of the hydraulic fluid from the first into the second pressure chamber occurs, to close the proportional valves during the power stroke so that, during the power stroke, at least one of the second fluid channels is a power stroke channel and the first pressure chamber is connected to a vent channel, the power stroke channel being connected to a supply channel and a branch channel for supplying hydraulic fluid having a predetermined pressure into the second pressure chamber, and the vent channel is connected to a collection tank for discharging the hydraulic fluid that is displaced from the first pressure chamber via a tank valve.

2. The apparatus according to claim 1, wherein the central control unit is configured that, during the power stroke, the second pressure chamber is connected to the hydraulic pump unit via a safety valve, at least one pressure pick-up for pressure detection of delivery flow of the hydraulic fluid, at least one pressure control valve for limiting the pressure of the delivery flow, and a proportional valve for setting the delivery volume.

3. (canceled)

4. The apparatus according to claim 1, wherein the proportional valves and the tank valve (30) are pressure-controlled built-in valves.

5. The apparatus according to claim 1, wherein the fast stroke piston partitions each of the fast stroke cylinders into pressure chambers having differently sized working surfaces in the fast stroke cylinder, channels provided in the base connect the fast stroke cylinder pressure chamber to the hydraulic system, wherein the pressure chamber having the larger effective surface is integrated into a hydraulic branch comprised of a double check valve, a 4/3-way proportional valve, a safety valve, and a high pressure accumulator, and the pressure chamber having the smaller effective surface is connected via the 4/3-way proportional valve to the collection tank.

6. The apparatus according to claim 1, further comprising, in the base at opposite sides of the table, two opposing fast stroke cylinders oriented parallel to a stroke axis of the pistons, the piston rods of the cylinders being connected to carriers, which are each attached to a respective side wall of the table.

7. The apparatus according to claim 6, wherein each of the fast stroke cylinder cylinders is closed in a pressure-tight manner by a cover, through which a respective of the piston rods extend.

8. The apparatus according to claim 1, wherein the hydraulic pump unit comprises a proportional valve configured to set the delivery volume, a pressure pick-up configured to activate the delivery volume setting proportional valve, and a pressure control valve for limiting pressure of the delivery flow.

9. The device according to claim 1, further comprising a displacement measuring unit configured to detect the OT position of the main piston.

10. A method for controlling the primary drive of a hydraulically driven fine blanking press with the apparatus of claim 1, in displacing the main piston, together with the table, during the rapid approach stroke between UT and OT, or OT and UT, by pressurizing the pressure chambers of a the fast stroke pistons, then, in a power stroke subsequent to the rapid stroke carrying out a blanking or shaping operation, by applying working pressure of a hydraulic fluid to the pressure chambers of the main piston, from the hydraulic system generated by the hydraulic pump unit and controlled by the control unit, wherein, during the rapid approach stroke, feeding the pressure chambers of the fast stroke piston a high pressure accumulator that is permanently set to the working pressure, and at the same time, disconnecting the pressure chambers of the main piston from the hydraulic system and connecting the pressure chambers of the main cylinder to each other via fluid channels and bypass channels (26) so as to displace the hydraulic fluid from the first pressure chamber into the second pressure chamber in a substantially depressurized state during the rapid approach stroke of the fast stroke piston.

11. The method according to claim 10, further comprising setting the working pressure in the pressure chamber of the fast stroke piston having the larger effective surface with the central control unit via a double check valve, a 4/3-way proportional valve, a controllable proportional valve, and a high pressure accumulator, and setting the working pressure in the pressure chamber of the fast stroke piston having the smaller effective surface is set via the 4/3-way proportional valve.

12. The method according to claim 10, further comprising, during the power stroke, setting the working pressure in the second pressure chamber of the main piston is set with the central control unit via a safety valve, at least one pressure pick-up for pressure detection, at least one pressure control valve for limiting the pressure of the delivery flow, and a proportional valve for the delivery volume, and setting pressure of the hydraulic pump unit delivery flow, and the pressure in the first pressure chamber via the tank valve and a collection tank.

13. The method according to claim 10, further comprising setting the OT position of the main piston with the central control unit via a displacement measuring system, wherein the delivery volume of the hydraulic pump unit is reduced before the OT is reached, and a counter pressure is generated by the tank valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a perspective view of a fine blanking press connected to the hydraulic system;

[0033] FIG. 2 shows a perspective view of the base together with the table;

[0034] FIG. 3 shows a section of the base together with the table along line III-Ill from FIG. 2;

[0035] FIGS. 4a and 4b each show a perspective view of the base, with an illustration of the locations of the fluid channels and of the vent channel;

[0036] FIG. 5 shows a section of the base together with the table along line V-V from FIG. 2;

[0037] FIG. 6 shows a section of the base together with the table along line VI-VI from FIG. 2;

[0038] FIGS. 7a and 7b show schematic representations of the displacement of the hydraulic fluid from one pressure chamber into the other pressure chamber of the main piston as a function of the stroke position of the fast stroke piston; and

[0039] FIG. 8 shows a schematic representation of the flow of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0040] FIG. 1 shows a perspective representation of a hydraulically driven fine blanking press 1, the main piston 2 of which essentially carries out a stroke movement between a lower dead point and an upper dead point OT in the direction of the stroke axis HU from the bottom to the top. The body 3 of the press 1 comprises a head piece 4, a base 5, box-shaped hollow pillars 6, and tie rods 7.

[0041] As is illustrated in FIGS. 2 and 3, a table 8, which supports the bottom tool part (not shown in more detail), is disposed on the upper face OS of the base 5.

[0042] Approximately centrally, two opposing fast stroke cylinders 9 oriented parallel to the stroke axis HU are introduced into the base 5, which each receive a double-acting fast stroke piston 10 and are closed by a cover 11. The fast stroke piston 10 includes a piston rod 12, which extends through the cover 11 and is connected to a carrier 13, which is attached to a side wall 14 of the table 8. The fast stroke piston 10 partitions a first and a second pressure chamber 15a and 15b (see also FIG. 3) in the fast stroke cylinder 9. The pressure chamber 15a and the pressure chamber 15b are connected via a channel 16a and 16b, respectively, which are introduced in the base 5, to the hydraulic tube 17 of the hydraulic system 18 so as to be acted upon by hydraulic fluid having a predefined pressure, such that it is possible to vertically displace the table 8 during the rapid approach in the direction of the head piece 4.

[0043] FIGS. 4a, 4b and 5 show the spatial locations of the fluid channels 24a to 24h and of the vent channel 29 in the base 5 in a transparent representation and in a section along line V-V from FIG. 2.

[0044] A main cylinder chamber 19 is formed in the base 5, the axis HA of which is located on the stroke axis HU of the fine blanking press and receives the double-acting main piston 20. The main piston 20 has a cylindrical shaft 21, which comprises disk-like working surfaces 22a and 22b protruding perpendicularly to the axis HA, which partition the main cylinder chamber 19 into a first (top) pressure chamber 23a and a second (bottom) pressure chamber 23b having a low stroke height, so that the base 5 is compact and has a low height.

[0045] The main cylinder chamber 19, and thus the pressure chamber 23a, is closed in a pressure-tight manner by a cover 27, which is attached to the base 5.

[0046] The first (top) fluid channels 24a, 24b, 24c and 24d and the second (bottom) fluid channels 24e, 24f, 24g and 24h, which are located in the base 5 on top of one another perpendicularly to the stroke axis HU corresponding to the heights of the pressure chambers 23a and 23b, lead into the pressure chambers 23a and 23b of the main piston 20. The fluid channels 24a to 24d are connected to the fluid channels 24e to 24h by a respective bypass channel 26.

[0047] Furthermore, a pressure-controlled proportional valve 25a, 25b, 25c and 25d is inserted as a built-in valve into each of the second (bottom) fluid channels 24e to 24h, the valve closing the respective bypass channel 26 when the second pressure chamber 23b is acted upon by hydraulic fluid having a predefined pressure from the hydraulic system 18.

[0048] During the rapid approach, the main piston 20 carries out a corresponding stroke movement between lower dead point UT and upper dead point OT and, when the proportional valve 25a to 25d is open, displaces the hydraulic fluid present in the first (top) pressure chamber 23a via the first (top) fluid channels 24a to 24d, the bypass channels 26, and the second (bottom) fluid channels 24e to 24h into the second (bottom) pressure chamber 23b. The first (top) pressure chamber 23a, the first (bottom) fluid channels 24a to 24d, the bypass channels 26, the bottom fluid channels 24e to 24h, and the second (bottom) pressure chamber 24b thus form a closed hydraulic system, which can be opened or closed, depending on the position of the proportional valves 25a to 25d, so that the first (top) pressure chamber 23a and the second (bottom) pressure chamber 23b are substantially depressurized, and the hydraulic fluid is displaced into the second (bottom) pressure chamber 23b of the main piston 20, and a fluid column can be created in the movement direction BR of the fast stroke piston 10 during the rapid approach.

[0049] When the fast stroke piston reaches the target position thereof during the rapid approach, the proportional valves 25a to 25d switch into the closed position, and the power stroke begins, which is described in more detail hereafter based on FIG. 6.

[0050] FIG. 6 shows the base 5 in a further section along line VI-VI from FIG. 2, which illustrates the locations of the fluid channel 24e and of the vent channel 29 (see also FIG. 4a).

[0051] The vent channel 29 opens into the first pressure chamber 23a of the main piston 20, and the fluid channel 24e opens into the second pressure chamber 23b, which are disposed on top of one another perpendicular to the stroke axis HU corresponding to the heights of the pressure chambers 23a and 23b.

[0052] A tank valve 30 for opening and closing the vent channel 29 is inserted into the vent channel 29 as a built-in valve, which is in the open position when, during the power stroke, the hydraulic fluid present in the pressure chamber 23a is displaced into the collection tank 44.

[0053] The fluid channel 24e is connected to a supply channel 32, which is situated parallel to the stroke axis HU in the base 5, and to a branch channel 33, which branches off this supply channel and via which the hydraulic system 18, which is not shown in detail, is connected.

[0054] FIGS. 7a and 7b schematically show the displacement of the hydraulic fluid from the first (top) pressure chamber 23a into the second (bottom) pressure chamber 23b during the stroke movement of the main piston 20 in the direction of TDC during the rapid approach, based on the example of fluid channels 24a and 24b.

[0055] The main piston 20, together with the table 8, carries out a stroke in the direction of OT due to the fast stroke piston 10. As a result of the upward motion of the working surface 22a of the main piston 20, the hydraulic fluid present in the first (top) pressure chamber 23a is displaced from the first (top) pressure chamber 23a when the tank valve 30 is closed, and when the proportional valve 25a is open, the fluid reaches the bottom pressure chamber 23b via the first fluid channel 24a, the bypass channel 26, and the second fluid channel 24e. The displacement is indicated in FIG. 7b by an arrow. In FIG. 7b, the fast stroke piston 10 has reached the top target position thereof, the proportional valve 25a closes, the proportional valve 30 opens, and the power stroke begins.

[0056] The flow of the method according to the invention will be described based on FIG. 8, which shows the hydraulic branch 41 for the rapid approach and the hydraulic branch 42 for the power stroke of the main piston 20.

[0057] The hydraulic branch 41 includes a high pressure accumulator 34 for hydraulic fluid, a logic proportional valve 36, which is activated by the central control unit 35 and which is connected to the hydraulic system 18 via the hydraulic tube 17 and sets the pressure level in the high pressure accumulator 34, a pressure pick-up 38, a safety valve 39, a 4/3-way proportional valve 37, which activates or deactivates the supply of the hydraulic fluid to the pressure chambers 15a or 15b depending on the position of the fast stroke piston 10 in the fast stroke cylinder 9, a double check valve 43 associated with the bottom pressure chamber 15b, and the pressure chambers 15a and 15b of the fast stroke pistons 10.

[0058] The pressure chambers 15a and 15b of the fast stroke piston 10 are supplied via the shared high pressure accumulator 34 with hydraulic fluid having an appropriate pressure, which is set by appropriate activation of the valve 36 by the central control unit 35 as an accumulator charge.

[0059] As soon as the fast stroke piston has reached the top target position thereof during the rapid approach, the proportional valve 25a installed in the fluid channel 24e closes, the tank valve 30 opens, and the 4/3-way proportional valve 37 switches to a center position.

[0060] The fluid channel 24e then assumes the function of a power stroke channel, in which hydraulic fluid having a predefined pressure is supplied to the second pressure chamber 23b.

[0061] The hydraulic branch 42 for the power stroke comprises a hydraulic pump unit 40, with which at least one proportional valve 45 for setting the delivery volume, at least one pressure control valve 46 for limiting the pressure of the delivery flow, and at least one pressure pick-up 47 for pressure detection for limiting the power and forwarding the pressure value to the central control unit 35 for activation of the pressure control valve 46 are associated, a safety valve 48, which activates or deactivates the supply of hydraulic fluid conducted to the bottom pressure chamber 23b, a pressure pick-up 49 for ascertaining the pressure value, which is forwarded to the central control unit for activation of the pressure control valve 46, and the pressure chambers 23a and 23b of the main piston 20.

[0062] Once the main piston 20 has reached the upper dead point OT thereof, the power stroke is ended. The safety valve 48 for the power stroke and the tank valve 30 close, at the same time the proportional valve 25a for the fluid channel 24e and the proportional valve 37 for supplying hydraulic fluid from the high pressure accumulator 34 open, and the rapid approach starts, in which the top pressure chamber 15a of the fast stroke piston 10 is acted upon by hydraulic fluid having a predefined pressure, so that the main piston 20, together with the table 8, is lowered, and reaches the bottom target position thereof. The 4/3-way proportional valve 37 switches, so that the bottom pressure chamber 15b can be acted upon by hydraulic fluid, and the fast stroke piston 10 is moved in the direction of the top target position thereof.

[0063] As soon as the fast stroke piston has reached the top target position thereof, another power stroke starts.