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Publication numberWO2003092924 A1
Publication typeApplication
Application numberPCT/EP2003/004241
Publication date13 Nov 2003
Filing date23 Apr 2003
Priority date3 May 2002
Publication numberPCT/2003/4241, PCT/EP/2003/004241, PCT/EP/2003/04241, PCT/EP/3/004241, PCT/EP/3/04241, PCT/EP2003/004241, PCT/EP2003/04241, PCT/EP2003004241, PCT/EP200304241, PCT/EP3/004241, PCT/EP3/04241, PCT/EP3004241, PCT/EP304241, WO 03092924 A1, WO 03092924A1, WO 2003/092924 A1, WO 2003092924 A1, WO 2003092924A1, WO-A1-03092924, WO-A1-2003092924, WO03092924 A1, WO03092924A1, WO2003/092924A1, WO2003092924 A1, WO2003092924A1
InventorsPedretti Franco Foppa
ApplicantPro Form S.R.L.
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
Bending control method and device for a hollow punch production plant
WO 2003092924 A1
Abstract
An improved bending control method for a hollow punch (20) production plant, the hollow punch (20) production plant comprising a bending station (10) wherein one of said hollow punches (20) is bent with a series of bending operations driven by a control unit; the method comprises at least one bending detection phase of the hollow punch (20), said detection being transmitted to the control unit which drives the subsequent bending operations. The invention also relates to an improved bending control device (22) for a hollow punch (20) production plant, wherein a control unit drives a relative movement between a bending tool (14) and a gripping element (12); said control device (22) comprises a bending detection unit (24) for the hollow punch (20), the bending detection unit (24) supplying information to the control unit.
Claims  (OCR text may contain errors)
1. An improved bending control method for a hollow punch (20) production plant, said hollow punch (20) production plant comprising a bending station (10) wherein one of said hollow punches (20) is bent with a series of bending operations driven by a control unit, characterized in that the method comprises at least one bending detection phase of the hollow punch (20), said detection being transmitted to said control unit which drives the subsequent bending operations.
2. The bending control method according to claim 1, characterized in that, when said detection indicates a deformation in a zone of said hollow punch (20) which shifts from the desired form, said hollow punch (20) un- dergoes a further bending operation in said zone of said hollow punch (20) .
3. The bending control method according to claim 1, characterized in that, when said detection indicates a deformation in a zone of said hollow punch (20) which shifts to a minimum extent from the desired form, said hollow punch (20) undergoes a further bending operation in another zone of said hollow punch (20) .
4. An improved bending control device (22) for a hollow punch (20) production plant, said hollow punch production plant (20) comprising a bending station (10) wherein one of said hollow punches (20) is bent with a series of bending operations driven by a control unit, said control unit driving a relative movement between a bending tool (14), which acts on a portion of said hollow punch (20), and a gripping element (12) , whereby another portion of said hollow punch (20) is blocked, characterized in that it comprises a bending detection unit (24) for said hollow punch (20), said bending detection unit (24) supplying information to said control unit.
5. The bending control device (22) according to claim
4, characterized in that said detection unit (24) comprises a support (26) equipped with at least one position sensor (28), which is passed along the side of an edge of said hollow punch (20) , close to its portion deformed by said bending tool (14) .
6. The bending control device (22) according to claim
5, characterized in that said support (26) rotates around a shaft (30) situated at one of its ends.
7. The bending control device (22) according to claim 5, characterized in that said support (26) moves along a straight guide or has any pre-established movement above said edge of said hollow punch (20) .
8. The bending control device (22) according to claim 5, characterized in that said position sensor (28) is of the inductive type.
9. The bending control device (22) according to claim
5, characterized in that there are three position sensors (28) of the inductive type, said three sensors (28) being in an aligned arrangement.
10. The bending control device (22) according to claim
6, characterized in that said shaft (30) is connected to a motor (32) of the step-by-step type.
11. The bending control device (22) according to claim 6, characterized in that said shaft (30) is connected to a motor (32) and is associated with a position transducer or encoder.
12. The bending control device (22) according to claim
4, characterized in that said control unit is electronic, said gripping element (12) consists of pliers and said bending tool (14) is a pin.
13. The bending control device (22) according to claim
5, characterized in that said edge of said hollow punch (20) has been previously processed to make it sharp.
14. The bending control device (22) according to claim 4, characterized in that said bending detection unit (24) is passed twice above said edge of said hollow punch (20), with a forward and a backward passage.
15. The bending control device (22) according to claim 5, characterized in that said position sensor (28) is of the optical type or is a video-camera.
Description  (OCR text may contain errors)

BENDING CONTROL METHOD AND DEVICE FOR A HOLLOW PUNCH PRODUCTION PLANT

The present invention relates to an improved bending control method for a hollow punch production plant.

The invention also relates to an improved bending control device, again relating to a hollow punch production plant, which implements said method. Hollow punches are tools used for the total or partial cutting of shaped profiles on a sheet of material.

A wide variety of materials can be used, depending on the applications.

Among the possible fields of application, the tech- nical paper industry in which the above material is generally paper or cardboard, can be mentioned as a purely illustrative but non-limiting example. There is also the shoe industry, normally relating to materials such as leather, rubber and hide. Another field is the clothes industry and leather goods in which fabrics and hides are processed.

Hollow punches are produced by manufacturing plants known in the art. A strip, generally made of steel, is processed on one side until a sharp edge is obtained. The strip then undergoes numerous bending phases in a bending station, until the desired profile is obtained, which generally forms a closed line.

In the current state of the art, the bending is obtained by blocking the strip in a point using a gripping element, such as pliers, and deforming it in another point by means of bending tools which substantially move in an orthogonal direction with respect to the strip thus blocked.

The movement of the bending tools is caused by a bending control device, in relation to the material of the strip and specific characteristics of the bending station.

However sophisticated the bending control method may be, however, the control device of the known art has great difficulty in handling all the bending variables.

It can be mentioned, for example, that the mechanical characteristics of the strip are never uniform for the whole length of the strip. Furthermore, the bending tools themselves wear with time and is obviously another source of uncertainty. An objective of the present invention is therefore to overcome the drawbacks described above and in particular to indicate an improved bending control method for a hollow punch production plant which allows bending errors to be minimized.

Another objective of the present invention is to provide an improved bending control device for a hollow punch production plant, which implements said method and allows less importance to be given to the exact determi- nation of the mechanical characteristics of the strip undergoing processing and the state of wear of the bending tools used.

A further objective of the present invention is to indicate an improved bending control method for a hollow punch production plant and to provide a relative improved bending control device which are particularly reliable, simple, functional and at relatively low costs.

These and other objectives according to the present invention are achieved by means of an improved bending control method for a hollow punch production plant as illustrated in claim 1, together with an improved bending control device as described in claim 4.

Further characteristics are included in the other claims . The characteristics and advantages of an improved bending control method for a hollow punch production plant and a relative improved bending control device according to the present invention will appear more evident from the following illustrative but non-limiting descrip- tion, referring to the enclosed schematic drawings, in which: figure 1 is an axonometric view of a bending station of a hollow punch production plant, showing an improved bending control device according to the present inven- tion, comprising a support with position sensors; figure 2 is an enlarged axonometric view of the bending station of figure 1, in which the support of the improved bending device is in a rotated position with respect to that illustrated in figure 1. With reference to the figures, these show a bending station, indicated as a whole with 10, of .a hollow punch 20 production plant. The bending station 10 is equipped with an improved bending control device 22, according to the present invention. In the example illustrated, the bending station 10 comprises a gripping element 12, such as pliers, with which a portion of the hollow punch 20, is blocked, and at least one bending tool 14, such as a pin, which acts on another portion of the hollow punch 20. The improved bending control device 22 comprises a control unit, for example electronic, which drives the relative movement between the bending tool 14 and the gripping element 12.

The control device 22 also comprises, according to the present invention, a bending detection unit 24.

The detection unit 24 includes a support 26 with position sensors 28, such as sensors of the inductive type. In the example illustrated in the figures, there are three sensors 28, which are aligned. The support 26 is passed along one side of an edge of the hollow punch 20, close to its portion deformed by the bending tool 14. In the example of the figures, the support 26 rotates around a shaft 30 situated at one of its ends. The shaft 30 is connected to a motor 32. The motor 32 can be of the step-by-step or another type, if associated with a position transducer or encoder.

An improved bending control method for a hollow punch 20 production plant according to the invention is evident from the above description relating to the improved bending control device 22, with reference to the figures, and is briefly as follows.

The hollow punch 20 is produced starting from a strip made of a metallic material, generally steel, of which one of the edges is processed to make it sharp. In the bending station 10, the strip leaves a slit created by the gripping element 12. The bending tool 14 moves in a substantially orthogonal direction with respect to the strip, creating a deformation on the strip. The moving of the bending tool 14, in the known art, is run by the control unit of the control device in relation to the mechanical characteristics of the material of the strip and the geometrical characteristics of the bending station 10. The improved control device 22 according to the present invention also comprises the bending detection unit 24. Said detection unit 24 reveals the profile formed by the strip following the action of the bending tool 14.

The detection unit 24 feeds back this information to the control unit of the control device 22, so that, in a subsequent bending operation, the control unit can also process this information which is particularly useful.

If, in fact, the positions found by the detection unit 24 after a bending operation show a shifting with respect to the desired form, the control unit of the control device 22 drives one or more supplementary operating phases of the bending tool 14.

In practice, thanks to the detection unit 24, the bending operation of the hollow punch 20 is fed back: the process errors are thus reduced to the minimum and the bending station 10 is, in practice, automatically calibrated. In relation to the programming of the control unit, it is also possible to establish an increase in the feedback gain, if an excessive number of bending steps for obtaining a certain profile of the hollow punch 20, is detected.

Position sensors 28 of the inductive type, are advantageously used.

These are passed along the side of the edge of the hollow punch 20. When a sensor 28 arrives close to the edge of the hollow punch 20, as the hollow punch 20 is made of a ferromagnetic material, the electromagnetic field created by the sensor 28 itself is varied, and the instant in which this takes place is thus signaled to the control unit. The control unit associates with this instant, information on the present position of the sensor 28, defined by the presence of a motor 32 of the step-by- step type, or by means of a position transducer in the case of another type of motor 32. More specifically, the sensor 28 passes along the side of the edge of the hollow punch which has been previously processed to make it sharp. In particular, a sharp cusp is formed, which can be more or less centered with respect to the thickness of the strip. With the inductive sensor 28, the position of the cusp can be revealed quite accurately, by processing the instants when the sensor 28 itself is activated and when it is de-activated, as the sensor 28 is passed once along the side of the edge of the hollow punch 20. The determination of the position of the cusp is further improved if there is a double passage of the sensor 28 above the edge of the hollow punch 20, which is obtained with one forward and one backward passage.

In this way, the control unit is able to render the detection of the position of the cusp practically independent of the geometry of the edge of the hollow punch 20, by obtaining the average of two pairs of positioning values; each pair is linked to the activation and deacti- vation of the inductive sensor 28 which takes place in the passage over the cusp of the edge of the hollow punch 20.

Furthermore, the. inductive sensor 28 has its own delay, essentially associated with the operating temperature of the sensor 28 and the passage rate over the cusp. With the forward and backward passage, the error of the inductive sensor 28 is, in practice, brought to zero, as this is an algebraic sum of two equal errors but with an opposite sign, thus rendering the information independent of the operating conditions and above all of the passage rate of the support 26 which carries the sensor 28 it- self.

Alternatively, instead of a sensor 28 of the inductive type, a sensor 28 of the optical type or video- camera, can be used. In these cases, however, problems must be solved such as an undesired reflection of the light radiation on the cusp of the sharp edge, or, image resolution, respectively.

In the non-limiting example of the figures, the support 26 which carries the three aligned sensors 28, ro- tates around the shaft 30 which is situated in correspondence with the portion of the hollow punch 20 blocked in the slit of the gripping element 12. This is not binding: on the contrary, instead of rotating around the shaft 30, the support 26 can move along a straight guide or have any pre-established movement above the profile of the hollow punch 20.

It should be noted that the detection unit 24 can also function with only one inductive sensor 28, even if, by increasing the number of sensors 28, the control unit can obviously receive better information for reconstructing the current profile of the hollow punch 20 and evaluate the shifting with respect to the desired profile.

The improved bending control method for a hollow punch 20 production plant, according to the present in- vention, substantially comprises, after each bending step or operation effected by the bending tool 14, a bending detection phase, i.e. at least one passage of the detection unit 24 above the profile of the hollow punch 20. When a deformation is obtained which shifts even to a minimum extent from the desired form, the strip advances and a new bending phase is effected, which is also controlled and fed back by the control device 22, and so on. The characteristics of the improved bending control method for a hollow punch production plant and the rela- tive improved bending control device, object of the present invention, appear evident from the above description, as also the relative advantages, among which the following can be mentioned:

- considerable improvement in the operating precision; - the determination of the exact characteristics of the material of the hollow punch belt before being processed, as supplied, is not important;

- the control of the state of wear of the bending tool is not important for the purposes of the bending precision; - accurate detection of the cusp of the sharp edge of the hollow punch; limited costs, if compared with the advantages obtainable

Finally, numerous modifications and variations, all included in the scope of the invention, can obviously be applied to the improved bending control method for a hollow punch production plant and the relative improved bending control device thus conceived; furthermore all the details can be substituted by technically equivalent elements. In practice, the materials used as also the forms and dimensions, can vary according to technical demands .

The protection scope of the invention is therefore delimited by the enclosed claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
WO1996021529A1 *8 Jan 199618 Jul 1996British United Shoe Machinery Ltd.A profile definition system
US4562754 *28 Feb 19837 Jan 1986Usm CorporationMethods for constructing cutting tools
US5461893 *28 May 199331 Oct 1995Cnc CorporationMethod and apparatus for bending steel rule
Classifications
International ClassificationB21D53/64, B21D11/10
Cooperative ClassificationB21D11/10, B21D7/14, B21D53/64
European ClassificationB21D7/14, B21D53/64, B21D11/10
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