Press drive comprising two working areas

Abstract

The invention relates to a press drive for a press or a press having a press drive. The invention also relates to a method for controlling the press drive by means of a control unit. The press drive is used for moving a ram of the press in a stroke direction H between an upper return point OT and a lower return point UT. It comprises a knee lever gear having a first lever and a second lever. A connecting rod engages on the knee lever of the two levers and is connected on the other end to an eccentric of an eccentric drive. The control unit can drive the eccentric drive in a first operating mode B1 or a second operating mode B2 or, in particular, also a third operating mode B3. In the first and the second operating modes B1, B2, the eccentric oscillates in a respectively different angle region W1, W2 about a rotation axis D of the eccentric drive, thus resulting in different force and movement states of the ram in both operating modes.

Claims

1. A press drive (16) for a press (10) comprising: a knee lever gear (24) having a first lever (25) and a second lever (26) that are pivotally supported on a hinged joint (27), wherein the knee lever gear (24) has a first bearing (28) which supports the first lever (25) on a press frame (11), as well as a second bearing (29) at which the second lever (26) is connected to a ram (15) of the press (10); a connecting rod (32) whose one end is pivotally supported on the hinged joint (27) and whose other end (34) is connected to an eccentric (35) of an eccentric drive (33), said eccentric being movable about a rotation axis (D); a control device (40) is configured to activate and to drive the eccentric drive (33) in at least one of a first operating mode (B1) and a second operating mode (B2); wherein the eccentric (35) is driven in a prespecified first angle region (W1) in a rotation-oscillating manner in the first operating mode (B1) and is driven in a rotation-oscillating manner in a prespecified second angle region (W2) in the second operating mode (B2); the press drive (16) is configured such that the ram (15) reaches a lower return point (UT) of the ram (15) twice during a complete rotation of the eccentric (35) at a second angle of rotation (α1) and a third angle of rotation (α2); in the first operating mode (B1) the eccentric (35) is driven in the rotation-oscillating manner in the first angle region (W1) about the second angle of rotation (α1) and in the second operating mode (B2) the eccentric (35) is driven in the rotation-oscillating manner in the second angle region (W2) about the third angle of rotation (α2); a first angle (β1) is enclosed between a longitudinal axis (L) of the connecting rod (32) and an axis (A) connecting the first bearing (28) and the second bearing (29) when the ram (15) is at the lower return point (UT) in the first operating mode (B1) and a second angle (β2) is enclosed between the longitudinal axis (L) of the connecting rod (32) and the axis (A) connecting the first bearing (28) and the second bearing (29) when the ram (15) is at the lower return point (UT) in the second operating mode (B2); in the first operating mode (B1), a first maximum press force of the ram (15) is available, and, in the second operating mode (B2), a second maximum press force of the ram (15) is available, wherein the first maximum press force is greater than the second maximum press force; the control unit (40) is configured to automatically set the first operating mode (B1) if a required press force is greater than the second maximum press force; the control unit (40) is configured to initiate a test stroke of the ram (15) in a test operating mode to sensorically detect at least a part of required parameters (P) and suggest at least one of the first and second operating modes (B1, B2).

2. The press drive of claim 1, characterized in that the hinged joint (27) is moved through the axis (A) connecting the first bearing (28) and the second bearing (29) in one of the first or the second operating modes (B1, B2).

3. The press drive of claim 1, characterized in that the hinged joint (27) is moved at most up to the axis (A) connecting the first bearing (28) and the second bearing (29) in one of the first or second operating modes (B1, B2).

4. The press drive of claim 1, characterized in that the control device (40) is configured to activate and to drive the eccentric drive (33) in a fourth operating mode or in the first operating mode (B1) or the second operating mode (B2) such that the eccentric (35) of the eccentric drive (33) is driven in an oscillating manner in a prespecified angle region, in which case the hinged joint (27) neither reaches the axis (A) connecting the first bearing (28) and the second bearing (29) nor is said hinged joint (27) moved through said axis (A).

5. The press drive of claim 1, wherein the first angle (β1) and the second angle (β2) have different sizes.

6. The press drive of claim 5, characterized in that the size of the first angle (β1) is greater than the size of the second angle (β2).

7. The press drive of claim 1, characterized in that a ram velocity (V) about the lower return point (UT), with the same rotational speed (ω) of the eccentric (35), is lower in the first operating mode (B1) than in the second operating mode (B2).

8. The press drive of claim 1, characterized in that the first bearing (28) is non-displaceably arranged on the press frame (11).

9. The press drive of claim 1, characterized in that at least one of the lengths of the two levers (25, 26) and the length of the connecting rod (32) are unchangeable.

10. The press drive of claim 1, characterized in that at least one of the position of the rotation axis (D) of the eccentric drive (33) relative to the press frame (11) and an eccentricity (E) of said eccentric (35) are unchangeable.

11. The press drive of claim 1, characterized in that one of the first lever (25) or the second lever (26) or the connecting rod (32) is configured as a triangular control arm (36) having three linkage points.

12. The press drive of claim 11, wherein the triangular control arm (36) includes a hinged joint (27) having a pivot axis proximate each of a first spaced apart linkage point (27a) and a second spaced apart linkage point (27b).

13. The press drive of claim 12, wherein the pivot axes of the hinged joint (27) proximate the first spaced apart linkage point (27a) and the second space apart linkage point (27b) extend parallel to each other.

14. The press drive of claim 13, wherein when the first lever (25) is configured as the triangular control arm (36), the second lever (26) comes into engagement at the first spaced apart linkage point (27a) and the connecting rod (32) comes into engagement at the second spaced apart linkage point (27b).

15. The press drive of claim 13, wherein when the second lever (26) is configured as the triangular control arm (36), the first lever (25) comes into engagement at the first spaced apart linkage point (27a) and the connecting rod (32) comes into engagement at the second spaced apart linkage point (27b).

16. The press drive of claim 13, wherein when the connecting rod (32) is configured as the triangular control arm (36), the first lever (25) comes into engagement at the first spaced apart linkage point (27a) and the second lever (26) comes into engagement at the second spaced apart linkage point (27b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantageous embodiments of the invention can be inferred from the description as well as from the dependent patent claims. The description is restricted to essential features of the invention. The drawings may be used for additional reference. Hereinafter the invention will be explained with the use of an exemplary embodiment and by making reference to the drawings. They show in:

(2) FIG. 1 a schematic representation in a manner similar to a block diagram, of a press with an exemplary embodiment of a press drive in accordance with the present invention;

(3) FIG. 2 a schematic diagram of a first exemplary embodiment of the press drive for a press in accordance with FIG. 1, in a first operating mode;

(4) FIG. 3 a schematic diagram of the first exemplary embodiment of the press drive for a press, in a second operating mode;

(5) FIG. 4 the ram position and the ram velocity as a function of the rotational position of the eccentric about the rotation axis of the eccentric drive for the first exemplary embodiment of the press drive; and

(6) FIGS. 5 through 7 schematic diagrams of additional exemplary embodiments of the press drive for a press according to FIG. 1, each with a triangular control arm.

DETAILED DESCRIPTION OF THE PARTICULAR EMBODIMENTS

(7) FIG. 1 shows a press 10 represented in the manner of a simplified block diagram. The press 10 comprises a press frame 11 by means of which the press 10 is set, or mounted to, a supporting surface 12.

(8) Furthermore, the press 10 comprises a press bed 13 on which is provided a lower tool 14.

(9) A ram 15 of the press 10 can be moved back and forth in a stroke direction H by means of a press drive 16. The stroke direction H is preferably oriented in vertical direction. An upper tool part 17 may be provided on the ram 15, said tool part interacting with the lower tool part 14 in order to process, for example form, a workpiece. Via a guide device 18, the ram is movably supported in stroke direction H by the press frame 11 and/or by the press bed 13. The guide device 18 is schematically represented in FIG. 1 by two guide rails 19, along which the ram 15 is guided back and forth.

(10) The press drive 16 comprises a knee lever gear 24. The knee lever gear 24 comprises a first lever 25 and a second lever 26 that are supported next to each other on a hinged joint 27 so that they can be pivoted together. The first lever 25 is supported by a first bearing 28 on its side opposite the hinge joint 27 so as to be pivotable on the press frame 11. The first bearing 28 is stationarily mounted to the press frame 11. The second lever 26 is connected, via a second bearing 29, so as to be pivotable with the ram 15.

(11) A connecting rod 32 comes into engagement with the hinged joint 27. On its one end, the connecting rod 32 is arranged so as to be pivotable about the pivot axis of the hinged joint 27. The opposite end of the connecting rod 32 is associated with an eccentric drive 33 and thus represents the drive end 34 of the connecting rod 32. The drive end 34 is pivotally attached to an eccentric 35 of the eccentric drive 33. The eccentric 35 can be driven in a rotating manner and, in particular, in a rotation-oscillating manner, about a rotation axis D. The distance between the eccentric 35 and the rotation axis D is referred to as eccentricity E and cannot be changed (FIGS. 2 and 3). The eccentric drive 33 is mounted to the press frame 11. The position of the rotation axis D relative to the press frame cannot be changed in the case of the exemplary embodiment. Likewise, the lengths of the connecting rod 32 and the two levers 25, 26 are constant and cannot be changed by adjustment means. Consequently, the press drive 16 is designed in a technically simple manner.

(12) Each of FIGS. 5 through 7 shows an embodiment of the press drive 16 that has been modified compared to the exemplary embodiment of FIG. 3. In that case, the hinged joint 27 is formed by two linkage points 27a, 27b. In the extended position of the two levers 25, 26, the two linkage points 27a, 27b can be arranged approximately vertically or horizontally next to each other. Either the connecting rod 32 (FIG. 5) or the first lever 25 (FIG. 6) or the second lever 26 (FIG. 7) may be configured as the triangular control arm 36. The course of the movement of the ram as shown by FIG. 4 relates to the embodiment shown by FIG. 3 and changes depending on the kinematics of the press drive 16 defined by the arrangement and embodiment of the levers 25, 26 and the connecting rod 32.

(13) The eccentric drive 33 is activated by a control unit 40. It pre-specifies the movement, as well as its chronological derivations such as the rotational speed ω or the angular acceleration. Furthermore, the control device 40 determines the torque of the eccentric drive 33. The latter may be embodied as an electric motor and, in particular, as a servo motor or torque motor. For example, the eccentric drive 33 may comprise an asynchronous machine and/or a gear, in particular a planetary gear. The control unit 40 may comprise an inverter for activating the eccentric drive 33.

(14) Furthermore, the press drive 16 may comprise one or more sensors for detecting specific parameters during the operation of the press 10. In the present exemplary embodiment, a force sensor 41 is shown, said sensor being associated with the first bearing 28. With the aid of the sensor signal of the force sensor 41, it is possible for the control unit 40 to determine the actual press force F.

(15) In the example, there is also a position sensor 42 whose sensor signal is transmitted to the control unit 40. With the aid of the senor signal of the position sensor 42, it is possible to determine the ram position Z. It is also possible to provide the control device 40 with additional sensor signals or parameters.

(16) In the exemplary embodiment described here, there is also an operating unit 43 by means of which an operator can input or prespecify operating parameters (BP). The operating parameters BP are conveyed to the control unit 40. The control unit 40 may be disposed for regulating the ram position Z and/or the press force F.

(17) Considering the technical design of the press drive 16 in accordance with the present exemplary embodiment, the rotation axis D of the eccentric drive 33 in stroke direction H is located above the first bearing 28. The eccentricity E is selected in such a manner that the eccentric 35, viewed in stroke direction H, may be located above or below the first bearing 28, depending on the angle of rotation α.

(18) When the eccentric 35 rotates once fully about its rotation axis D (angle of rotation α=0° to α=360°, the hinged joint 27 is moved twice through an axis A, said axis connecting the first bearing 28 and the second bearing 29. In other words, the hinged joint 28 assumes its extended position twice, in which position the two levers 25, 26 are aligned along axis A. In this extended position of the hinged joint 27, the ram 15 is at its lower return point UT. When the hinged joint 27 is at its greatest-possible distance from the axis A, the ram 15 is at its upper return point OT. In the diagram in accordance with FIG. 4, the definition provides that the ram 15 reaches its upper return point OT at α=0° (corresponds also to α=360° and at a first angle of rotation α0. The first angle of rotation α0 divides one complete rotation of the eccentric 35 into a first area S1 and a second area S2. In the first area S1, the ram 15 reaches its lower return point UT at a second angle of rotation α1 and, in the second area S2, the ram 15 reaches its lower return point UT at a third angle of rotation α2. Due to the kinematics of the knee lever gear 24, the movement of the ram 15 is not the same in the two areas S1, S2. This is due to the fact that the position of the connecting rod 32 relative to the two levers 25, 26 is different in both areas S1, S2.

(19) The control unit 40 is disposed to operate the eccentric drive 16 in a first operating mode B1, a second operating mode B2 or a third operating mode B3. The first operating mode B1 is performed in such a manner that the eccentric 35 is driven in a rotation-oscillating manner in a first angle region W1 about the second angle of rotation α1. The first angle region W1 is located in the first area S1, and is at most as large as this first area S1. In the second operating mode B2, the eccentric 35 is driven in a rotation-oscillating manner about the rotation axis D in a second angle region W2 about the third angle of rotation α2. The second angle region W2 is located within the second area S2 and is at most as large as the second area S2. The size of the two angle regions W1 and W2 is a function of the required stroke of the ram 15. If the angle regions W1, W2 are smaller than the respectively associated area S1, S2, the maximum possible stroke of the ram 15 is not fully utilized and only a part of the motion characteristic Z(α) shown in FIG. 4 is utilized. The upper return point OT then shifts toward OT′ or OT″.

(20) In the third operating mode B3, the eccentric 35 is driven in a pre-specified direction of rotation in manner so as to rotate about the rotation axis D. Consequently, the eccentric 35 moves on a circular orbit about the rotation axis D. During each orbit, the first, as well as the second, angle region W1, W2 is passed twice.

(21) The longitudinal axis L of the connecting rod 32 connects the pivot axis of the joint hinge 27 with the pivot axis between the eccentric 35 and the drive end 34 of the connecting rod 32. If the angle of rotation α corresponds to the second angle of rotation α1, the ram 15 is in the first operating mode B1 at its lower return point UT. In the first operating mode B1, the longitudinal axis L and the axis A through the first bearing 28 and the second bearing 29 subtend a first angle β1 (FIG. 2) when the ram 15 is at its lower return point UT. Correspondingly, in the second operating mode B2, the longitudinal axis L of the connecting rod 32 and the axis A subtend a second angle β2 when the ram 15 is in the second operating mode B2 at its lower return point UT (FIG. 3). Respectively, the smaller angle between the longitudinal axis L and the axis A are measured as the first and second angles β1 and β2. The angles β1 and β2 are acute angles. The size of the first angle β1 is larger and, in accordance with the example, larger by the factor of 1.3 to 1.5, than the size of the second angle β2. For this reason, the maximum press force Fmax made available by the ram 15 at a specific torque of the eccentric drive 22 in the first operating mode B1 is greater than in the second operating mode B2.

(22) The motion characteristic Z(α) is flatter in the first angle region W1 in the first operating mode B1 than in the second angle region W2 in the second operating mode B2. Therefore, the ram velocity V at the lower return point UT in the first operating mode B1 is lower than in the second operating mode B2. Therefore, a higher press force F of the ram 15 can be made available in the first operating mode B1. In the second operating mode B2, with the same stroke of the ram 15, it is possible to achieve greater stroke numbers due to the higher ram velocity V and thus a greater output of the press 10. FIG. 4 shows the ram velocity characteristic V(α) as a function of the angle of rotation α.

(23) In the present exemplary embodiment, the control unit 40 is designed to automatically selectively adjust the first operating mode B1 or the second operating mode B2 as a function of the detected and/or prespecified parameters P. The parameters P are those that have been prespecified via the operating unit 43, namely the parameters BP and/or parameters that have been sensorically detected such as, for example, the press force F, the ram position Z, the stroke number of the press, the stroke of the ram, the ram velocity, the transfer time for insertion and/or removal of a workpiece in or from the press 10, or similar parameters. The said parameters can be used in any desired combination. It is also possible that the control device 40 is switched into a test operating mode and that it sensorically detects at least a part of the required parameters P during one or more test strokes of the ram 15, and suggests a suitable operating mode B1, B2. This operating mode can be indicated and suggested to the operator by an operating unit 43, for example. The operator may then accept or decline the suggested operating mode.

(24) Based on the kinematic dimensions and the maximum motor torque, it is possible to determine an available press force over the drawing path for the first and the second operating modes B1, B2. Considering the existing press force requirements in the operating mode that makes available the lower press force, a determination is made as to whether the output of the press—taking into consideration the boundary conditions prespecified by the operator—is greater with an oscillating movement of the ram in the second operating mode B2 or with a complete orbit of the eccentric in the third operating mode B3. The second operating mode B2 or the third operating mode B3 is selected accordingly. In doing so, it is preferably also taken into consideration whether the full ram stroke is needed or not. The boundary conditions prespecified by the operator are, for example, the ram velocities and/or the maximum ram velocities at certain points or in certain sections of the ram characteristic. If the press force requirement is greater, there remains only the stronger but slower first operating mode B1, and the calculated output can then only be accepted.

(25) If conflicts between the sensorically detected parameters and the parameters BP pre-specified via the operating unit are detected, a suitable operating mode B1, B2 will be suggested by the control unit via the operating unit 43, and the conflict will be indicated.

(26) The invention relates to a press drive 16 for a press 10 or a press 10 having a press drive 16. The invention also relates to a method for controlling the press drive 16 by means of a control unit 40. The press drive 16 is used for moving a ram 15 of the press in a stroke direction H between an upper return point OT and a lower return point UT. It comprises a knee lever gear 24 having a first lever 24 and a second lever 26. A connecting rod 32 engages on the knee lever 27 of the two levers 25, 26 and is connected on the other end 34 to an eccentric 35 of an eccentric drive 33. The control unit 40 can drive the eccentric drive 33 in a first operating mode B1 or a second operating mode B2 or, in particular, also a third operating mode B3. In the first and the second operating modes B1, B2, the eccentric oscillates in a respectively different angle region W1, W2 about a rotation axis D of the eccentric drive 33, thus resulting in different force and movement states of the ram 15 in both operating modes.

LIST OF REFERENCE SIGNS

(27) 10 Press 11 Press frame 12 Supporting surface 13 Press bed 14 Lower tool part 15 Ram 16 Press drive 17 Upper tool part 18 Guide device 19 Guide rail 24 Knee lever gear 25 First lever 26 Second lever 27 Hinged joint 27a, 27b Linkage point 28 First bearing 32 Connecting rod 33 Eccentric drive 34 Drive end 35 Eccentric 36 Triangular control arm 40 Control unit 41 Force sensor 42 Position sensor 43 Operating unit α Angle of rotation α0 First angle of rotation α1 Second angle of rotation α2 Third angle of rotation β1 First angle β2 Second angle ω Rotational speed A Axis B1 First operating mode B2 Second operating mode B3 Third operating mode BP Operating parameter D Rotation axis E Eccentricity F Press force Longitudinal axis OT Upper return point S1 First area S2 Second area UT Lower return point V Ram velocity W1 First angle region W2 Second angle region