PUNCHING MACHINE"

FIELD OF THE INVENTION

The present invention concerns a detection device able to detect the force, even very high force up to 50,000 N and more, applied by a high-speed punching machine with a frequency in the range of 900-1000 cycles per minute and more, on a punch of a removable tool-carrier. The device is applicable both to punching machines having a single punch and also to those with tool-carriers having a plurality of punches, and is able to detect the force used by the punch selected and to generate a corresponding electric signal which can be processed to optimize both the functioning of the punching machine and also the use of the punches.

BACKGROUND OF THE INVENTION

It is known that a high-speed punching machine, that is, one able to perform 900-1000 cycles a minute, and even more, imparts a very high force, even in the range of 50,000 N and more, on the piece to be punched, for example metal sheet, in order to make an incision, a hole, a notch, a nibble or to draw it.

In particular punching machines are known that have an actuation member with which a tool-carrier or punch-bearer is associated, of the removable and interchangeable type, on which one or more punches are mounted.

In this field, the need to monitor said force on each individual work station is very strongly felt, so that then the force can possibly be modified by acting on the command means and, where possible, can be limited to what is necessary so as to save energy.

As of today, however, simple and reliable detection devices have not yet been produced, to be applied on tool-carriers of the removable type to be used, for example, on a high-speed punching machine, of the type with exchangeable tool- carriers, in order to detect the force actually applied on the selected punch and hence on the piece being worked, so that it is then possible to use the value of force detected in order to set the machine itself and to optimize the work cycles.

The Japanese patent application JP-A-2003/094123 discloses a device to control the operativity of a punch mounted on a punching machine operating at low pressure and low speed, in which a load cell is associated with the actuation member of the punching machine in order to detect the pressure applied by the latter on the punch. However, this device is not able to detect the actual force applied by the punch on the piece being worked.

The British patent application GB-A-2.254.281 discloses a shearing press in which there is a pressure sensor associated with the actuation member of the press, to detect the pressure with which the punch is actuated, and also a detector of the travel actually effected by the actuation member. This device too, which is very complicated and costly, is not able to detect the actual force applied by the punch on the piece being worked.

The Japanese patent application JP-A-7032065 discloses a device suitable to detect the force applied by the actuation member of a punching machine to a group of punches and to generate a corresponding electric signal which is compared with a predetermined value so as to stop the punching machine when the value detected is abnormal. However, this device is not able to detect the actual force applied by the punch on the piece being worked either.

One purpose of the present invention is to achieve a detection device which is able to detect, simply and actually, at least the force actually applied on a punch by a punching machine, in particular but not exclusively for working sheet metal and of the high-speed type, and to generate a corresponding electric signal, proportionate to the force detected, to send it to a main and/or auxiliary control unit, internal and/or external, of the punching machine, so that it can process the signal to optimize the punching operations, according to determinate parameters. Another purpose of the present invention is to achieve a detection device able to detect the actual punching force too, net of the resistant force, such as for example that of the return means, consisting of springs for example, and also the extraction force of the punch from the punched piece.

Another purpose of the present invention is to achieve a detection device which is able to detect the resistant force of one or more return means.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION The present invention is set forth and characterized in the independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, a device to detect the force actually applied on a punch by a high-speed punching machine, having command means able to selectively command the displacement of an actuation member toward a piece to be punched, and a tool-carrier disposed removably between the actuation member and the piece to be punched. The tool-carrier can be of the type that comprises a containing body in which are mounted, axially sliding, at least a punch and at least a hammer associated with the punch, so that the latter can selectively move axially between an inactive position and a work position when actuated by the hammer.

According to a characteristic feature of the present invention, at least one force sensor is associated with the hammer, to detect the force applied by the command means to the punch. In particular, the force sensor is disposed between the hammer and the punch.

According to a variant of the present invention, two force sensors are provided, at least one of which is associated with the hammer.

In a first form of embodiment of the variant, both the force sensors are disposed in the tool-carrier, one in correspondence with the upper part of the hammer and the other between the hammer and the punch.

In another form of embodiment of the variant, one of the two force sensors is disposed in the actuation member, while the other force sensor is disposed in the tool-carrier, between the hammer and the punch.

Each of the force sensors is able to generate an electric signal proportionate to the force detected, which is able to be transmitted to the control unit and/or the command means, by means of transmission means, which can be with or without wires.

The device according to the present invention thus allows to detect easily and accurately both the punching force and the extraction force for each tool or punch associated with the punching machine. Furthermore, once the parameters of each tool have been set, such as shape, measurement, type of sharpening, thickness and type of material, it is possible to calculate if the force detected is suitable or not for the type of work to be done, whether it is an incision, a hole, a notch, a nibble or drawing, and therefore to set, for each tool, the admissible amount of stress that it can support both during punching and during extraction. This can even occur automatically in a self-learning mode, for example by attributing a fixed percentage to the force normally required, in order to send a signal to the control means of the punching machine, for example to stop working and emit an acoustic alarm, or to work with a twin tool, previously set.

In fact it is known that the tool wears during working and that it progressively requires more force, both to make the holes, and to be extracted from the holed piece, for example metal sheet, until it breaks when it exceeds its physical limit. This also occurs if the matrix is worn. But, in this case too, the device according to the present invention is able to detect the entity of wear which is equal or proportionate to the force detected.

Therefore, the device according to the present invention allows to carry out at least the following two intervention options: a) to stop working and send an acoustic alarm and/or an electronic signal that informs an office or an operator, by means of any known transmission system, including a text message, and thus gives the possibility of replacing the worn tools, or to carry out maintenance and/or sharpen the tools; b) to allow the punching machine to continue working with a twin tool previously programmed.

Moreover it is known that this type of working often occurs without any human presence and that some difficult or delicate processes can condition the quality of the result, single or multiple, in the case of punching machines with a loading and unloading system.

Therefore, the present invention solves these and many other problems known to the persons of skill in the field.

Indeed the device according to the present invention is able to detect any type of force actually applied on a punch by a punching machine, also allowing to safeguard tools with small sections and hence very delicate and thus to give the possibility of not ruining the sheet metal, or in general the pieces being worked, and also to protect the tool itself from wear and/or anomalies such as sudden increases in resistance to the cutting due to quality variations in the products worked. Furthermore, in the case of swarf being lifted with the punch (a well known and problematic phenomenon in this technique), the tool may find itself in the condition of having to cut a double thickness, with serious consequences such as breakage thereof, or damage to the worked product.

In the case of wear by abrasion of the side of the tool, the anchorage of particles of worked material increases exponentially with every passage. This cohesive effect not only increases the force required for holing but also increases the extraction force, exponentially, until the point of the punch is blocked inside the metal sheet. When this happens, the work is blocked and the grippers that move the sheet on the plane of the punching machine either cause the tool to break, or cause the sheet itself to crumple.

Therefore, by detecting the force of each individual tool and processing the signal generated by the device according to the present invention, each punching machine can monitor the workings and the wear of its main components which, when desired, can be re-ordered in safety and with their own code: indeed in this field the difficulty implicit in attributing the exact code for the correct reordering of a worn tool is known and is strongly felt.

Since it is possible to pre-set the work parameters, a suitable software or program of the control unit of the punching machine can detect the station of appurtenance, the shape, measurements, type of sharpening, thickness and type of material and, by means of a code configurer, can give the exact and relative reordering code of the worn elements in electronic format, such as the punch- bearer or tool-carrier device, the punch, the extractor and the matrix, with a play suitable for that particular working. This code or these codes can be moved into a sort of "purchase trolley" for multiple orders, or can be sent (by means of any known system) directly to the purchasing office or, if connected to the Internet, directly to the supplier.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a three-dimensional view of a punching machine with a tool-carrier in which a detection device according to the present invention is mounted;

- fig. 2 is a three-dimensional view of a tool-carrier on which a detection device according to the present invention is mounted in a first form of embodiment;

- fig. 3 is a view from above of the tool-carrier in fig. 2;

- fig. 4 is a median longitudinal section from IV to IV in fig. 3;

- fig. 5 is a median longitudinal section of a tool-carrier on which a detection device according to the present invention is mounted in a second form of embodiment;

- fig. 6 is a three-dimensional view of a detail of the punching machine in fig. 1 in which a detection device according to the present invention is mounted in a third form of embodiment;

- fig. 7 is a view from above of the detail in fig. 6;

- fig. 8 is a median longitudinal section from VIII to VIII in fig. 7;

- fig. 9 is a three-dimensional view of a detail of the punching machine in fig. 1 in which a detection device according to the present invention is mounted in a fourth form of embodiment;

- fig. 10 is a view from above of the detail in fig. 9;

- fig. 1 1 is a median longitudinal section from XI to XI in fig. 10;

- fig. 12 is a first diagram which shows schematically the development of the force, expressed in tons (Ton), with respect to the time (T) expressed in milliseconds (ms), detected by a detection device according to the present invention and that refers to the working of a piece with a 1.5 mm thickness;

- fig. 13 is a second diagram which shows schematically the development of the force, expressed in tons (Ton), with respect to the time (T) expressed in milliseconds (ms), detected by a detection device according to the present invention and that refers to the working of a piece with a 2 mm thickness;

- fig. 14 is a third diagram which shows schematically the development of the force, expressed in tons (Ton), with respect to the time (T) expressed in milliseconds (ms), detected by a detection device according to the present invention and that refers to the functioning of an anti-swarf system.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications. DETAILED DESCRIPTION OF SOME PREFERENTIAL FORMS OF

EMBODIMENT

With reference to fig. I, a detection device 10 according to the present invention is able to detect the actual force FW (fig. 4) applied on a piece 16 to be punched by a high-speed punching machine 1 1 (fig. 1), of any known type, comprising an actuation member 12, consisting for example of a hammer which is commanded by command means 15, for example of the fluid-dynamic type, of a known type and therefore not described in detail here.

The command means 15 are able to impart to the actuation member 12 alternate movements toward the underlying piece 16 to be punched, along a central axis X, with a very high actuation force F, which may reach 50,000 N and more, and high-speed, that is, with a frequency of 900-1,000 cycles per minute, and even more.

The punching machine 1 1 also comprises for example a tool-carrier device 18, which is able to be mounted removably and interchangeably below the actuation member 12, coaxially to the central axis X.

The tool-carrier device 18 (figs. 2 to 1 1) comprises a containing body 19 inside which either a single punch 20 is axially sliding, which may consist of a single body or of several interconnected parts, as shown here, where an upper part 21 of them functions as a support or extension; or a plurality of punches, for example as in the Italian application for a patent of industrial invention n. UD2010A000156, filed on 27.07.2010 by Applicant.

In the containing body 19, in contact with the support 21 of the punch 20, a hammer 22 is also disposed, also axially sliding. Return means, in this case comprising springs 23 of the Belleville type, normally hold the support 21, the punch 20 and the hammer 22 in an inactive position, with the lower end of the punch 20 at a determinate distance, some millimeters, from the piece 16 to be punched. The resistant force RM that opposes the actuation of the punch 20 toward the piece 16 is equal to the force imparted by the return springs 23 and to the various frictions of the system possibly present. Therefore, the actual force FW applied on the piece 16 will be equal to the difference between the actuation force F and the resistant force RM (FW = F - RM).

The command means 15 are able to be commanded in a known manner by a control unit 28 (fig. 1), to move the actuation member 12 first against the hammer 22 (figs. 4, 5, 8 and 1 1) and then thrust it downward, together with the punch 20 and the support 21, against the action of the return springs 23, until the punch 20 reaches a work position in which it punches the piece 16.

The detection device 10, according to a first form of embodiment shown in figs. 2, 3 and 4, comprises a force sensor 25 mounted in a seating 24, made on the upper wall of the hammer 22, and disposed so that it too can directly receive the actuation force F imparted by the actuation member 12 on the hammer 22, but can also take into account the reaction of the resistant force RM.

The force sensor 25 in this case is a load cell, of a known type and available on the market, which is able to detect the actual force FW and to generate a corresponding electric signal proportionate thereto.

As an alternative to the load cell, a force sensor of the piezoelectric type may be used, or any other sensor of a known type, able to generate an electric signal proportionate to the force detected.

The electric signal generated by the force sensor 25 is sent, for example by means of an electric connector 26, to the control unit 28 (fig. 1), which controls the command means 15.

According to a second form of embodiment, shown in fig. 5 and which also comes within the framework of the present invention, a force sensor 35, identical to the force sensor 25, instead of being in the upper part of the hammer 22 is interposed between this and the punch 20. In particular, the force sensor 35 is housed in a cavity 29 made on the upper part of the support 21 of the punch 20 and is disposed so that it too can receive the thrust imparted by the hammer 22 on the punch 20. In this case too, the force sensor 35 is able to detect the actual force FW that will be transferred by the punch 20 to the piece 16. The force sensor 35 is connected to the control unit 28 by means of an electric connector 36, disposed so that it does not interfere with the actuation member 12.

According to a third form of embodiment, which also comes within the framework of the present invention and is shown in figs. 6, 7 and 8, in addition to the force sensor 25 disposed in the upper part of the hammer 22, the device 10 also comprises, to detect the actuation force F, a second force sensor 45 disposed in the cavity 29 made on the upper part of the support 21 of the punch 20, to detect the actual punching force FW applied by the punch 20 on the piece 16. The second force sensor 45 is connected to the control unit 28 by means of an electric connector 46, disposed so that it does not interfere with the electric connector 26, which in this case is made to exit laterally, or with the actuation member 12.

According to a fourth form of embodiment, which also comes within the framework of the present invention and is shown in figs. 9, 10 and 1 1, the device 10 comprises a force sensor 55, disposed in the lower part of the actuation member 12, in particular in a cavity 58 of the latter, to detect the actuation force F, and another force sensor 65 disposed in the cavity 29 made on the upper part of the support 21 of the punch 20, to detect the actual perforating force FW applied by the punch 20 on the piece 16. The two force sensors 5 and 65 are connected to the control unit 28 by means of two corresponding electric connectors 56, respectively 66, disposed so that they do not interfere with the action of the actuation member 12.

According to a variant, not shown in the drawings, the electric signal generated by each force sensor 25, 35, 45, 55, 65 can be sent to the control unit 28 by any known wireless means, such as for example a small radio wave transmitter, or realized for example using Wi-Fi, Tag or Bluetooth technology.

It is therefore clear for the person of skill in the art that inserting at least one force sensor inside a tool-carrier device 18, instead of only into the actuation member 12 of the punching machine 1 1 , as happened in the prior state of the art, allows to obtain a much more accurate detection of the actual force applied by the punch 20 on the piece 16, and also of the development of the force over time.

It has also emerged from experiments that there is not a simple linear relationship between the various components in play - such as for example the thickness of the piece 16 to be worked and the working speed of the actuation member 12 - and the actual force FW needed to carry out the working (see figs. 12 and 13).

In these conditions it is therefore essential to be able to isolate, as can be done with the present invention, only the FW component of the overall actuation force F that is applied by the punching machine 11 which actually affects the punch 20 and the piece 16, separating it from the portion absorbed by the elastic elements 23 present in the system (RM).

Although the behavior of the elastic elements 23 is less difficult to trace to a mathematical law, and since therefore the component of force absorbed by them is quantifiable, the elastic elements 23 are in turn subject to wear and breakage, which introduces an error factor into the theoretical evaluation.

The behavior of the elastic elements 23 is also influenced by environmental elements, such as for example the temperature, which can vary the response.

Some working steps, such as for example the one that involves the functionality of the technical solutions adopted in the tools in order to prevent the working swarf from being lifted with the punch, entail a very limited force compared with others, quantifiable in the range of error size as above (see fig. 14). In particular, the part of the curve that represents the force step affected by the action of the anti-swarf systems is the one comprised between instants T2 and T3.

In the working step given as an example, which is extremely important for the correct management of the production process of the punching machine 1 1, it is therefore very difficult to carry out an evaluation of the quality of the working without being able to examine with precision only the force connected to the punch 20, thus eliminating the critical factors as above.

In the same way, the present invention allows to accurately analyze workings that entail using very small tools, where the FW component of the overall actuation force F that is applied by the punching machine 1 1 on the punch 20 and the piece 16 has a value comparable to that of the errors introduced into the theoretical evaluation by the elastic elements 23. In this technical field the problems connected to workings carried out in critical situations like those described are very well known and strongly felt: such situations often entail the breakage of the tools and/or erroneous working, with consequent discards and/or the need to rework the pieces.

The present invention also allows not only to obtain a correct evaluation of the development of the process, but also to solve the problem, well known and strongly felt by persons of skill in the art, of a reliable indication of the state of wear of each punch 20 and also of the elastic elements 23 in the tool-carrier device 18. If the progressive wear on the punch 20 leads to an increase in the force required to carry out the working, the wear on the elastic elements 23, on the contrary, results in a reduction in the component of force absorbed by them.

This means that, if we only have available the value of the overall actuation force F applied by the punching machine 11, as is possible in the state of the art, the components of wear of the punches 20 and the elastic elements 23 tend to reciprocally cancel each other out, in this case too rendering the control over the forces at play less effective.

On the contrary, the present invention allows to evaluate the forces that affect the punches 20 and the elastic elements 23 independently, each of which can therefore be correctly controlled independently by means of appropriate statistical techniques, offering a more correct and speedy indication of the state of wear of the individual components of the system.

It is clear, moreover, that modifications and/or additions of parts may be made to the device 10 as described heretofore, without departing from the field and scope of the present invention.

It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of detection devices to detect the force applied by a punching machine, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.