Method and device for feeding a sheet metal panel to a punch press

Abstract

The procedure followed for aligning a metal sheet in the correct position for inserting it into a punch press is that the aligned position in the feed direction is adjusted by means of stops. The alignment in the second direction orthogonal to the feed direction is such that the position of the metal sheet in the second direction is determined by a sensor and a control unit, and the deviation of the metal sheet from the predetermined aligned position in the second direction from the control unit is determined. Next, the alignment in the second direction is controlled by means of the gripping arrangement which is provided for the feed of the metal sheet to the punch press by controlling the gripping arrangement in such a way that the deviation is compensated and the metal sheet is aligned correctly.

Claims

1. A method for aligning a metal sheet upon feeding the metal sheet to a processing station, wherein the feed takes place in a first direction (Y axis) of two orthogonal directions (X axis and Y axis), wherein in a first alignment step, the alignment of the metal sheet takes place in the first direction (Y axis) and in a second step the alignment takes place in the second direction (X axis) to achieve a predetermined aligned position of the metal sheet, and wherein for feeding the metal sheet is gripped by a gripper arrangement and is moved towards the processing station and introduced into the processing station and is additionally moved back and forth in the second direction for achieving the desired processing pattern, wherein the alignment of the metal sheet in the second direction (X axis) is provided by the following steps: determining the position of the metal sheet in the second direction (X axis) by a sensor means; detecting the deviation of the metal sheet from its predetermined aligned position in the second direction by analyzing the sensor signal by a control unit; adapting the position of the gripping arrangement to the detected position of the sheet to eliminate the detected deviation by displacing the gripping arrangement in the second direction according to the deviation and the detected position of the sheet before gripping of the sheet at the sheet's determined position for movement in the second direction; and correcting the deviation of the aligned position from the predetermined aligned position in the second direction (X axis) after gripping the metal sheet by means of the gripping arrangement, in that the gripping arrangement, controlled by the control unit, performs the movement of the metal sheet into the predetermined aligned position in the second direction in combination with the feed movement of the metal sheet to the processing station.

2. The method according to claim 1, wherein the step of determining the position of the metal sheet in the second direction is determined by a stationary sensor of the sensor means.

3. The method according to claim 1, wherein the step of determining the position of the metal sheet in the second direction is determined by a movable sensor of the sensor means.

4. The method according to claim 3, wherein the movable sensor is arranged on the gripping arrangement and is moved by the gripping arrangement over the metal sheet.

5. The method according to claim 1, wherein a line sensor with or without a reflector is a sensor of the sensor means and/or a camera with image processing is a sensor of the sensor means.

6. The method according to claim 1, wherein a sensor of the sensor means is arranged above or below the position of the metal sheet or a sensor of the sensor means is provided both above and below the position of the metal sheet.

7. The method according to claim 1, wherein the position of the metal sheet is detected on one edge or on the other edge of the metal sheet which lies in the X direction.

8. The method according to claim 1, wherein the position of the metal sheet position is detected by several different optical sensors of the sensor means.

9. A device for alignment of a metal sheet upon feeding the metal sheet to a processing station comprising: a control unit and a gripping arrangement with at least one gripper, said gripping arrangement being provided to implement feeding of the metal sheet, under control by the control unit, to the processing station, in a first direction (Y axis) of two orthogonal directions (X axis and Y axis), and being additionally provided for the movement of the metal sheet in the second direction; sensor means connected to the control unit and producing a sensor signal indicating the position of the metal sheet in the second direction (X axis), and the control unit being adapted to determine from the sensor signal the deviation of the metal sheet from a predetermined aligned position in the second direction, and cause the gripping arrangement to be displaced in the second coordinate direction before gripping the metal sheet to compensate for any deviation of the metal sheet from the predetermined aligned position, and then grip the metal sheet and execute movement of the metal sheet into the predetermined aligned position in the second direction during the feeding movement of the metal sheet to the processing station.

10. The device according to claim 9, wherein the sensor means for determining the position in the second direction is a stationary sensor.

11. The device according to claim 9, wherein the sensor means is a movable sensor for determining the location in the second direction.

12. The device according to claim 11, wherein the movable sensor of the sensor means is arranged on the gripping arrangement and can be moved by it over the metal sheet.

13. The device according to claim 9, wherein the sensor means is a line sensor with or without a reflector, or a camera with image processing.

14. The device according to claim 9, wherein the sensor of the sensor means is arranged above or below the metal sheet position, or the sensor means is comprised of sensors above and below the metal sheet position.

15. The device according to claim 9, wherein sensor means has a plurality of different sensors for detecting the metal sheet position.

16. A system for producing punched parts from metal sheets, the system including a destacker for destacking individual metal sheets from a stack, a punch press for forming the punched parts from the respective metal sheet and having a device according to claim 9 for aligning the respective metal sheets upon feeding them to the punch press.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional embodiments, advantages and applications of the invention are derived from the dependent claims and from the description which now follows with reference to the figures, in which:

(2) FIG. 1 shows schematically a destacker and a punch press as well as a coordinate system to illustrate the feed of a metal sheet from the destacker to the punch press in both the prior art and in a procedure according to the invention;

(3) FIGS. 2 through 6 show a procedure according to the prior art;

(4) FIGS. 7 through 11 show a procedure and a device according to one exemplary embodiment of the invention; and

(5) FIG. 12 shows an example of a gripper of the gripper arrangement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) To illustrate an exemplary embodiment of the invention, reference is also made to the coordinate system according to FIG. 1. The prior art has already been explained with reference to FIGS. 2 through 6, to which reference is made here.

(7) FIG. 7 shows a centering table 15 of one exemplary embodiment of the invention in which a sensor means 16 is provided with at least one sensor and as the case may be any illumination means and/or reflectors, said sensor means being able to detect the position of the edge of a metal sheet, which comes to lie on the table within the detection range of the sensor means, and detect the position of the edge in the X coordinate, which will be explained further below. Thus, together with a control unit 18 which receives the signal of the sensor means 16, the position of the metal sheet can be detected in the X coordinate and/or the deviation of the metal sheet 1 from the desired predetermined aligned position in the X coordinate. FIG. 7 as well as FIGS. 8 and 9 do not show the gripper arrangement in order to simplify the figures. However, a gripper arrangement is present and will be explained later with reference to FIGS. 10, 11 and 12. FIG. 7 also shows conveyor belts 3, 4 and 5 by means of which the respective metal sheet 1 can be moved back and forth on the centering table in the Y coordinate direction. Instead of or in addition to conveyor belts, other means may also be provided for this movement, for example, rollers partially countersunk in the table. The table 15 may be provided with means for facilitating the movement of metal sheets on the table in a known manner, for example, with roller bodies arranged in a regular placement or with means for producing air cushions. The skilled person will be aware of such means which will not be discussed further here.

(8) FIG. 8 shows a metal sheet 1 which has been deposited on the centering table and first on the conveyor belts 3 and 4. By means of the conveyor belts 3, 4 and 5, the metal sheet is aligned in the Y direction by shifting the metal sheet 1 first in the Y+ direction. Once the metal sheet has reached a position in which it sits only on the conveyor belt 5 as shown in FIG. 9, it is displaced in the Y (Yminus) direction toward the two stops 6 and 7, as explained already in the prior art, and as shown here in FIG. 10. This is the preferred type of alignment in the Y direction. Other known types of alignment in the Y direction may also be used.

(9) In the figures in the exemplary embodiment, the sensor means 16 comprise at least one stationary sensor 17 with a longitudinal extent in the X coordinate direction. This sensor is, for example, a line sensor having a plurality of light-sensitive sensor elements arranged in a row and thus capable of emitting a signal which can determine the position of an object above the sensor, by detecting which sensor elements are darkened by the object and which sensor elements are not darkened. In this example, such a sensor is arranged in a recess 13 in the tabletop, so that it comes to lie beneath the metal sheet 1. Furthermore, it is arranged in such a way that, with the metal sheet 1 aligned in the Y coordinate, the position of the edge 1 in the X coordinate can be emitted as a sensor signal via the sensor. It can be seen in FIG. 10 that the edge 1 of the metal sheet 1 lies above the sensor so that a portion 17 of the sensor is covered by the metal sheet 1. The portion of the sensor of the sensor means which lies in the X+ direction and is not covered by the metal sheet 1 is labeled as 17. The sensor is connected to a control unit 18 which analyzes the sensor signal and thus can calculate the deviation of the position of the metal sheet 1 in the X coordinate from the desired aligned position of the metal sheet. This control unit also controls the drive of the gripper 11 in the gripper arrangement. The precise position of the metal sheet by the sensor means can be detected by means of just one sensor, for example, using the abovementioned line sensor, and with or without illumination means and/or reflectors, or the sensor means may include multiple sensors whose signals are analyzed in the control unit. The sensor means may also include an optical system, for example, a camera with image processing, which is used in addition to a sensor or instead of a sensor. Sensors or cameras of the sensor means may be arranged above the metal sheet position and/or beneath the metal sheet position as illustrated in this example. For reasons of precision, multiple detections may be performed. This position of the metal sheet can be detected on one edge or the other of the metal sheet and/or in the case of scrolled sheets having two edges on each side that can be scanned, this may be carried out on both edges of one side or on both edges of one or both sides.

(10) The sensor means may also include detection of the sheet metal edge by means of at least one movable sensor instead of at least one stationary sensor or in addition to a stationary sensor. For example, as shown in FIG. 10, a sensor 17a of the sensor means may be arranged on the gripper 11 and, for determination of the position of the metal sheet, the gripper 11 is moved over the metal sheet in such a way that its position in the X coordinate is determined. Since the control unit is usually adapted to know the position of the gripper of the gripper arrangement, it may also in this case derive the position of the metal sheet from the sensor signal. In this case, it is possible to omit a line sensor and a simpler sensor may be used.

(11) At any rate, the sensor means may also comprise a sensor that is movable separately from the gripper. For example, a movable proximity switch may be provided. In this case detection of the sheet metal edge may take place by means of a time calculation. Since the starting position of the sensor is known and the rate of movement of the sensor is known, the time at which the sensor detects the edge of the sheet metal can be determined. An accurate position can be deduced from this time. However, to eliminate maintenance, sensor means which operate with a stationary sensor or with a stationary camera or with a movable sensor arranged on the gripper or with a camera arranged on the gripper are preferred.

(12) Due to the determination of the position of the metal sheet in the second direction (X axis) by the sensor means 16 and detection of the deviation of the metal sheet from its predetermined aligned position in the second direction by analysis of the sensor signal by the control unit, the deviation can be corrected subsequently in feeding and/or transporting the metal sheet to the press. FIG. 10 shows that a deviation X in the position of the metal sheet in the X coordinate from the desired alignment and/or centering has been determined by the sensor 17 of the sensor means and by the control unit 18. This deviation is then corrected by the gripper arrangement.

(13) The correction of the deviation of the aligned position from the predetermined aligned position in the second direction (X axis) takes place after the metal sheet has been gripped by means of the gripping arrangement in that the gripping arrangement executes the movement of the metal sheet into the predetermined aligned position in the second direction during the feed movement of the metal sheet to the processing station, controlled by the control unit. This may take place in such a way that the gripper arrangement with the gripper 11, which is known to be movable by the control unit in X and Y directions, can be moved by means of corresponding drives of the gripper, first executes a movement in the X (Xminus) direction to correct the amount X and then executes the movement toward the press 20 in the direction Y+. However, a combined X and Y movement of the gripper 11 is preferred so that it is moved in the direction of the arrow K wherein the movement in the direction X takes place only as long as the deviation X has been eliminated.

(14) It is preferable for the location of the gripper arrangement to be adapted to the recognized location of the sheet, which deviates in the second direction before the gripping of the sheet by displacing the gripper arrangement accordingly in two directions in order to provide the gripping of the sheet in the location on the sheet provided for this purpose. This is shown in FIG. 10 by the fact that the gripper 11 of the gripper arrangement is also displaced essentially by the amount X in the second direction, likewise before the gripping, in order to grip the sheet 1 at the location provided for this purpose.

(15) Then the gripper 11 brings the metal sheet into the press 20 and carries out the known punching movement in X and Y directions, as shown in FIG. 11. The gripper arrangement may also have two grippers in a known way with the metal sheet 1 aligned by the first gripper being transferred between them. The gripper 11 in FIG. 10 then carries out the correction movement in the X direction and the Y movement toward the punch press and carries out all the punching actions on at least one row of the punch pattern (usually two or three punch rows), after which a second gripper of the gripper arrangement takes up the metal sheet and performs the punching action while the first gripper is returned back to the point of transfer of the following metal sheet.

(16) FIG. 12 shows a known gripper of the gripping arrangement such as it is already used in traditional devices and as it is also used for the present invention. The gripper 11 can be moved by corresponding drives in the X direction and in the Y direction, where these drives are controlled by the control unit. The gripper has two tongs 19, by means of which the metal sheet can be gripped at its rear edge as seen in the Y+ direction and can then be released again. This is known and will not be discussed further here.

(17) Although preferred embodiments of the invention are described in the present patent application, it should be pointed out clearly that the invention is not limited to them and can also be carried out in another way within the scope of the following claims.