JPH04367327A - Hydraulic blank holder for single-acting press - Google Patents

Abstract

PURPOSE: To lower the flow rate of a pressure medium and to enable sensitive control by providing a blank holder with plural pressure liquid chambers actively connected to a pressure regulator and closing the pressure medium outlets of these pressure liquid chambers not connected to this pressure regulator during a throttling process. CONSTITUTION: This blank holder is provided with at least four pressure coupling sections each having a tightening cylinder 10 between a cross beam 17 connected to a press ram 1 and a blank holder ring 4. At least one pressure-tight sliding elements formed as the pressure liquid chambers 13 are arranged in the respective pressure coupling sections. At least one pressure liquid chamber 13 is actively connected by the pressure regulator 23 to each of the respective pressure coupling sections so that the pressure liquid chamber 13 not connected to the pressure regulator 23 during the throttling process may be closed from the pressure medium outlet. All the pressure liquid chambers 13 are thus actively connected to a pressure liquid vessel 19.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a hydraulic blank for forming sheet metal in a single-acting press, especially a mechanical press, for suppressing it with a small force during the forming process, and for extruding the sheet metal after the forming process is finished. Regarding the holder.

0002

BACKGROUND OF THE INVENTION German Democratic Republic Patent No. 267204 discloses a hydraulic blank holder for a single-acting press, which clamps a workpiece against a ram and eliminates the need for the ram to operate against this force. It is being The device consists of at least one hydraulically actuated piston connected to a press ram and at least one hydraulically actuated piston connected to a pressure piston plate, the pistons being operatively connected to each other. Thereby, by building up pressure in the pressure medium chamber of the pressure medium unit at or just before the start of the drawing process,
A force acting against the movable press ram is exerted between the upper die and the drawing ring by means of the pressure pin plate. Furthermore, an output of an auxiliary working cylinder and/or an adjustable pressure transducer are arranged in the connecting line between the pressure medium chamber and the pressure medium balancing vessel, the piston rod of which acts on the pressure pin plate. connected.

With this known method, it is not possible to adjust the different forces on the circumference of the blank holder ring and the different forces acting on the blank holder ring during the drawing process. In the case of the drawing device of the press in European Patent Application No. 0173755, a pressure cylinder cooperating with a pressure wall and a blank holder is rigidly connected to a cylinder housing. In that case, the piston of the pressure cylinder is withdrawn from the cylinder housing on both sides via piston rods and cooperates with the blank holder on the one hand and with the pressure wall on the other hand. The cylinder chamber of each pressure cylinder is connected, on the piston side opposite the blank holder, to the outlet for passive control and to the pressure outlet for active control, via valves that vary the flow rate separately. Connected to medium pressure device. This method requires a large amount of energy during the holding action, ie during the blank holding period. Furthermore, since the volume exclusion principle controls a very large volume of conveying flow in order to control the force at the die cushion, a valve with a large internal diameter is required. This makes force control less sensitive than smaller diameter valves. Small diameter valves have low mass, inertia and control time.

Federal Republic of Germany Patent Application No. 3807
No. 683 describes a drawing device in the drawing stage of a press which includes all the functions of a die cushion. This drawing device consists of a blank holder that holds the drawn part from below and loads it through a pressing wall, a pressure cylinder that holds the blank during drawing, and a control to lift the blank holder after forming the drawn part. It consists of a pressure cylinder. Its pressure wall is guided in the press platform and acts on the blank holder from below. Each blank holding pressure cylinder is associated with a pressure cylinder for lifting the blank holder, which pressure cylinders are arranged concentrically and have a piston operatively connected thereto. Additionally, devices are used that move multiple pressure cylinders simultaneously and uniformly. This system also utilizes the volume exclusion principle and therefore requires a large amount of energy during the suppression action and requires a valve with a large internal diameter. Furthermore, this throttling device requires a high outlay for the synchronous control of each pressure cylinder.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to generate a large blank holding force with a small amount of energy in a single-acting press by using appropriate technical means, and also to improve the three-dimensional shape of the workpiece plane during the drawing process. The aim is to obtain an optimum blank holding force in accordance with the technical conditions of each drawn part in terms of arrangement and flexible size.

[0006]

According to the invention, this object is achieved by providing for each blank holder at least four pressure connections with clamping cylinders, each pressure connection having at least one pressure connection formed as a pressure fluid chamber. one pressure-tight sliding element is arranged and at least one pressure liquid chamber per pressure connection is operatively connected by a pressure regulating device;
During the throttling process, pressure liquid chambers that are not connected to the pressure regulating device can be closed to the pressure medium outlet, which is achieved in that all pressure liquid chambers are operatively connected to the pressure liquid container. Advantageous embodiments of the invention are described in the patent claims 2 to 9. An advantage of the invention is that the flow rate of the pressure medium to control the force during blank holding is low. This allows the use of small diameter valves with correspondingly low masses, inertia forces and control times, allowing sensitive force control.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail with reference to the drawings, which illustrate various embodiments of hydraulic blank holders. 1 to 5 show a hydraulic blank holder and a mold in cross-section, each with the necessary control devices. The differences between the embodiments are in the pressure connections and pressure control methods. By pressure connection is meant the active element which is subjected to pressure during the drawing process between the lower pressure point 16 on the cross beam 17 and the pressure point 5 on the blank holder ring 4.

A common feature in all the embodiments is that at least four pressure connections, which are arranged in particular in the corner areas of the press table, are equipped with pressure-tight sliding elements, which are designed as pressure liquid chambers 13. . This sliding element is bounded by an upper working piston 9 and a lower working piston 14. The pressure liquid chamber 13 is connected to the pressure liquid container 19 via piping. This piping includes a check valve 21 that can be opened and a pressure limiting valve 2 that acts as a safety valve.
2 are arranged in parallel. The non-return valve 21 then blocks off the pressure fluid chamber 13 in the outflow direction, and the pressure limiting valve 22 is arranged to act as a safety valve. The pressure liquid container 19 is given a bias pressure using air pressure. This pressure is variably regulated by a pressure regulator 18.

A further common feature in all embodiments is that in each pressure connection at least one pressure liquid chamber 13 and/or one pressure liquid chamber 26 is connected in accordance with the prior art to a pressure regulating device 23 to 29; The advantage lies in the fact that the pressure adjustment in the pressure connection can be carried out independently of one another during the drawing process. In that case, as an example, each pressure liquid chamber 1
A proportional directional control valve or a proportional pressure limiting valve is installed in the outlet pipes 3 and 26. The hydraulic blank holder in Figures 1 to 5 is disclosed in German Democratic Republic Patent No. 26720.
4, in which a press ram 1, preferably with four connecting rods 12, is suitably arranged under a press table 20 and is firmly connected for reciprocating movement. It is connected to the cross beam 17.

In FIG. 1, at least four pressure connections between the lower pressure point 16 and the upper pressure point 5 are arranged in the area of the press platform, each of these pressure connections having a
a piston rod 15, a lower working piston 14, a pressure liquid chamber 13, an upper working piston 9 with a contact support on the underside of the pressure pin plate 8, a pressure pin 7 located above the pressure pin plate 8, an intermediate pin 6 , blank holder ring 4
and is operatively connected to the upper mold 2 through the workpiece 3 during the drawing process, i.e. supported in relative contact with each other, so that a blank holding force is exerted between the upper mold 2 and the blank holder ring 4 without any acting force of the press ram 1. is generated.

The pressure in the pressure fluid chamber 13 then determines the blank holding force in the respective pressure connection. The pressure liquid chamber 13 of each clamping cylinder 10 is respectively connected to a pressure measuring transducer 11, which pressure measuring transducer 1
1 measures pressure, converts it into an electrical signal, and pressure regulator 2
The target pressure is controlled via the proportional valve No. 3. press ram 1
From the top dead center to the start of drawing, the lower working piston 1
4 follows the press ram 1 according to the cross beam 17. In that case, the pressure liquid chamber 13 is replenished via the non-return valve 21 with the pressure liquid of the pneumatically biased pressure liquid container 19, while the upper working piston 9 remains in the upper mechanical end position. .

As the upper die 2 starts colliding with the workpiece 3, the upper working piston 9 and the lower working piston 14
are synchronously lowered at ram speed, so that the pressure liquid container 19
No exchange of pressure fluid with the fluid occurs anymore. At the same time, the proportional pressure regulator 23 is actuated by releasing a small amount of oil from the accumulator towards the pressure liquid chamber 13, whereby a variable small amount of oil is released via the proportional valve in relation to the pressure and the throttling depth. controlled. After the bottom dead center of press ram 1,
Blank holding is released by opening the check valve 21. The upper working piston 9 and the pressure pin plate 8 connected thereto reach the upper mechanical ejector position by means of bias pressure in the pressure liquid container 19. Thereafter, the lower working piston 14 moves further towards top dead center at ram speed, in which case pressure liquid is forced out of the pressure liquid chamber 13 through the check valve 21 and into the pressure liquid container 19 .

The method of this embodiment is that the pressure pin plate 8
Regardless of the ejector function described above, the stroke and time control of the pressure pin plate 8 from pre-acceleration before the start of drawing to control of the bottom dead center of the press ram is performed by a die cushion device of a known type located centrally. It will be done.

The embodiment of FIG. 2 differs from that of FIG. 1 in that a separate pressure pin plate 8 is assigned to each pressure connection. This embodiment makes it possible to better match the forces of each clamping cylinder to the pressure pins belonging to each pressure pin plate 8.

The approach of the embodiment of FIG. 3 further improves the direct force action on the blank holder ring 4. The pressure pin plate 8 is omitted here, and the forces generated in each clamping cylinder 10 act directly on the blank holder ring 4 at the upper pressure point 5. The operation of this method is shown in Figure 1.
and corresponds to the scheme in FIG.

The embodiment of FIG. 4 corresponds to the arrangement and operation of the clamping cylinder 10 of FIG. 1, but the proportional pressure regulating valve 23 is not used. The major difference from the embodiment of FIG. 1 is that a pressure cylinder 24 is arranged between the pressure pin plate 8 and each pressure pin 7. The differential piston 25 of the pressure cylinder 24 is constrained between a pressure liquid chamber 26 and an elastic element 27 (for example a disc spring). The pressure cylinder 24 determines the height position of the contact surface of the pressure pin 7 by the pressure in the pressure liquid chamber 26 . In that case, an increase in the height position of the contact surface of the pressure pin 7 means an increase in the degree of tightening between the lower pressure point 16 and the upper pressure point 5 during the drawing process, and thus the blank holder ring 4 and the upper mold This means an increase in blank holding force between 2 and 2. The pressure liquid chambers 26 are each connected to an inlet of a pressure measuring transducer 28 and a proportional pressure regulator 29, and each pressure cylinder 24 is connected to an outlet of a proportionally controlled small internal diameter. The pressure adjustment of the pressure fluid chamber 26 during the throttling process independently of one another adjusts the force at each pressure pin 7 and intermediate pin 6 variably and proportionally to the pressure, which force is applied to the upper pressure point 5 of each pressure connection. acts as a blank holding force. In the illustrated embodiment of the pressure cylinder, the differential piston 25 is mechanically adjustable in height and no stroke and force adjustments are made during the throttling process. This adjustment can also be done by a separate mechanical device.

The embodiment of FIG. 5 corresponds in operation to the embodiment of FIG. It has the function of applying bias pressure at a pressure corresponding to the total pressure pin force acting on the pin.

Furthermore, a pressure transducer 31 is connected to each pressure liquid chamber 13 via a line which can be interrupted by a directional valve 30 . The pressure height of the pressure liquid in the pressure transducer 31 is regulated by a pressure regulator 18 in the pneumatic line. A directional valve 32 in the pneumatic line between the pressure regulator 18 and the pressure transducer 31 is used for pressure relief and for filling the pressure transducer 31 with pressure liquid.

The system of the embodiment of FIG. 6 is a combination of FIG. 1 and the embodiment of FIG. In that case, the arrangement, shape and control of the pressure connection from the lower pressure point 16 to the pressure pin plate 8 corresponds to the embodiment of FIG. 1, and from there to the upper pressure point 5 the upper part corresponds to the embodiment of FIG. Corresponds to the example. In each pressure connection, the two pressure liquid chambers 13, 26 are proportionally pressure controlled in parallel during the throttling process. pressure cylinder 24
The pressure control of the tightening cylinder 10 is carried out by the pressure regulator 29 as a primary control, and the pressure control of the tightening cylinder 10 is carried out by the pressure regulator 23 as a secondary control. In that case, the data of the pressure regulator 29 is transferred to the analog-to-digital converter 33.
, a microprocessor 34 and a digital-to-analog converter 35 to the pressure regulator 23, and the pressure in the pressure liquid chamber 13 is controlled each time so that the forces acting above and below the pressure pin plate 8 are balanced. Ru.

[0020]

An advantage of the invention is that the flow rate of the pressure medium for controlling the force during blank holding is low. This allows the use of small diameter valves with correspondingly low masses, inertia forces and control times, allowing sensitive force control.

[Brief explanation of drawings]

FIG. 1 shows a sectional view of a clamping cylinder with a proportional pressure regulator and a common pressure pin plate.

FIG. 2 shows a sectional view of a clamping cylinder with a proportional pressure regulator and a separate pressure pin plate.

FIG. 3 shows a sectional view of a clamping cylinder with a proportional pressure regulator and without a pressure pin plate.

FIG. 4 is a cross-sectional view of a slightly bias-pressured tightening cylinder with a common pressure pin plate and a pressure cylinder with proportional pressure adjustment between the pressure pin and the pressure pin plate;

5 shows a sectional view of a clamping cylinder which is subjected to a large bias pressure in accordance with the embodiment of FIG. 4;

FIG. 6 is a sectional view of a proportional pressure controlled tightening cylinder with a common pressure pin plate and a proportionally adjusted pressure cylinder between the pressure pin and the pressure pin plate;

[Explanation of symbols]

1 Press ram 4 Blank holder ring 7 Pressure pin 8 Pressure pin plate 10 Tightening cylinder 13 Pressure liquid chamber 19 Pressure liquid container 23 Pressure adjustment device 24 Pressure cylinder 29 Pressure adjustment device 31 Pressure transducer

Claims (9)

[Claims] Claim 1: A single-acting press, especially for forming sheet metal, in which the pressure connections in the press table, which support each other during the drawing process, are arranged on the cross beam connected to the press ram and on the blank holder ring of the lower mold. In hydraulic blank holders of mechanical presses, at least four pressure connections with clamping cylinders (10) are arranged per blank holder, and at least one pressure connection formed as a pressure liquid chamber (13) in each pressure connection. A dense sliding element is arranged and at least one pressure liquid chamber (13,
26) is operatively connected by the pressure regulator (23, 29), and during the throttling process the pressure liquid chamber (13) which is not connected to the pressure regulator (23) can be closed to the pressure medium outlet and all Hydraulic blank holder of a single-acting press, characterized in that the pressure liquid chamber (13) of is operatively connected to a pressure liquid container (19). 2. characterized in that a clamping cylinder (10) is arranged on the underside of a common pressure pin plate (8) in its corner area, on which the pressure pin rests. A hydraulic blank holder for a single-acting press according to claim 1. 3. Claim characterized in that each clamping cylinder (10) is arranged under a separate pressure pin plate (8), and the pressure pins rest on these pressure pin plates (8). A hydraulic blank holder for a single-acting press according to item 1. 4. Hydraulic type of single-acting press according to claim 1, characterized in that the clamping cylinder (10) is directly operatively connected to each pressure pin (7) in the area related to the mold. blank holder. Claim 5: Pressure pin plate (8) and each pressure pin (7).
Hydraulic blank holder for a single-acting press according to claim 1 or 2, characterized in that pressure cylinders (24) are arranged between the two pressure cylinders (24) and pressure is individually supplied to these pressure cylinders (24). . 6. Single-acting press according to claim 1, characterized in that the clamping cylinder (10) is biased with a constant and slight blank holding force. Hydraulic blank holder. 7. Claim characterized in that the clamping cylinders (10) are bias-pressured independently of each other with a constant pressure of a pressure transducer (31) whose size can be adjusted in relation to the mold. A hydraulic blank holder for a single-acting press according to any one of Items 1, 2, and 5. 8. Single-acting press according to claim 1, characterized in that the clamping cylinder (10) and the pressure cylinder (24) are supplied with proportional pressure control. Hydraulic blank holder. Claim 9: A pressure pin plate (8) and each pressure pin (7).
3. The hydraulic blank holder for a single-acting press according to claim 1, wherein a mechanical adjustment device is disposed between the blank holder and the blank holder.