DESCRIPTION

The present invention relates to the technical sector of machines for mechanical processing.

In particular, the present invention relates to a centring device of the type usable in a machine for processing metal sheets, for example a press.

In the industrial field, the continuing need to improve production performance, in particular in terms of volumes of articles produced or processed, brings with it the need to provide machines and plants equipped with high precision.

In fact, this characteristic is essential in order to maintain the quality of the processes carried out unchanged even in the face of a significant increase in the number of products processed per unit of time.

In the context of machines for processing metal sheets, for example presses, it is especially necessary to ensure the correct positioning within the work area of the metal sheet to be subjected to processing.

The presses for the processing of metal sheets can comprise a mould having two half-moulds, a first half-mould configured to retain and convey the metal sheets to be processed and a second half-mould usually having one or more tools capable of performing a processing on the metal sheet.

In order to therefore ensure the correct positioning of the metal sheet inside the press, in particular with respect to the tools that are associated thereto, centring devices are known which perform the dual function of ensuring the correct positioning of the metal sheet and maintaining it in position during the processing.

These devices are made by means of a centring pin rigidly connected with a half-mould and configured to engage a seat of the second half-mould when these close on the metal sheet.

The pin then passes through the metal sheet, preferably crossing a through seat thereof (which can have been suitably provided in the previous processing steps), centring the metal sheet in the work area of the machine in which it is inserted.

Such devices can also comprise a pressing member configured to abut against the metal sheet by applying a pressure thereon aimed at maintaining it in position, thereby avoiding the risk that the metal sheet moves during the processing.

However, the known centring devices have disadvantages which make their use inefficient and potentially harmful for the machine on which they are installed.

In fact, in the case where the metal sheet has not been correctly transferred to the machine, or problems have arisen upstream in the production process which result in an incorrect arrangement and/or realisation of the through seats in the metal sheet, the centring pin fails to properly insert in the appropriate seat.

In this situation, the centring pin is then subjected to an axial stress which can cause the breaking thereof with the additional risk of also damaging the press itself.

To obviate the described problem, it is known to realise plates which serve as frangible elements and which are placed in contact with the end of the pin opposite to that which is intended to pass through the through seat of the metal sheet.

In this way, when the centring pin does not properly engage the through seat of the metal sheet or the seat of the half-mould where it must be inserted, it can unload the axial stress to which it is subjected onto the frangible element, which breaks and thereby avoids the pin being damaged or the machine to which it belongs being damaged.

However, this solution is also not free from some criticalities that render its use not always feasible and have serious side effects on the quality of the processing performed by the machine.

In fact, the operator has no way of noticing the timely entry into operation of the frangible element, thus there is the possibility that the machine continues to operate even after the breaking of the frangible element (and the consequent displacement of the centring pin) with the risk of producing components that do not comply with that which has been designed (because the metal sheet is not centred properly, and any pressing member no longer performs its proper function).

In other words, in the known devices, it is not possible to precisely and immediately identify the occurrence of an abnormal situation that makes the press unable to operate correctly.

The problems and inefficiencies highlighted above are also attributable to presses aimed at carrying out punching processes, in which the centring pin serves a punching function.

Also in this situation, anomalous situations can lead to the application of an excessive mechanical stress on the pin.

It is for example possible that an undesired misalignment of the various press components occurs over time, in particular of the two half-moulds, up to the point where, when these close again on the metal sheet to process it, the pin does not meet and is not inserted any more properly on the seat realised in the half-mould opposite to that on which it is installed.

In this situation, the frangible element will have a sufficient force to support the pulse resulting from the impact of the pin against the metal sheet without breaking, instead it will break when the pin is subjected to a much greater force resulting from the fact of being crushed against a surface of a half-mould.

In this context, the technical task underpinning the present invention is to provide a centring device which obviates at least some of the drawbacks in the prior art as described above.

In particular, an object of the present invention is to provide an efficient and reliable centring device which allows identifying, in a timely manner, the occurrence of any operational situations which are potentially harmful or such as to achieve non-conforming items.

The technical task set and the objects specified are substantially attained by a centring device, comprising the technical characteristics as set out in one or more of the accompanying claims.

According to the present invention, a centring device is shown for a press mould for the processing of metal sheets which comprises a centring pin, a frangible element and a circuit element.

The centring pin has a first end configured for the insertion in a seat of a first half-mould of a press mould.

The frangible element is associated with a portion of the centring pin which is distal with respect to the first end and is stably associable with a second half-mould of the press mould.

The frangible element is configured to be subject to breaking when the centring pin is subjected to an axial force greater than a predetermined value.

The circuit element is associated with the frangible element so that the breaking of the frangible element determines an electrical transmissibility variation thereof.

Advantageously, the electrical transmissibility variation of the circuit element can be detected by suitable devices that are connectable thereto, providing an immediate and easy to read indicator of any breaking of the frangible element.

Further characteristics and advantages of the present invention will become more apparent from the indicative and thus non-limiting description of a preferred but non-exclusive embodiment of a measurement device, as illustrated in the appended drawings, in which:

- figure 1 shows a centring device according to the present invention;

- figure 2 shows a press mould for the processing of metal sheets in a non-operating configuration;

- figure 3A shows the press mould in a correct operating configuration;

- figure 3B shows the press mould in an incorrect operating configuration;

- figure 4 shows a view of the frangible element to which a circuit element has been associated. In the accompanying figures, reference numeral 1 indicates the centring device according to the present invention, which will be indicated in the following description as device 1.

The device 1 is in particular applicable and usable in a press mould 10 which comprises a first half-mould 1 1 and a second half-mould 12 which will be described in greater detail below.

The device 1 comprises a centring pin 2, a frangible element 3 and a circuit element 4.

In particular, the centring pin 2 has a first end 2a configured for the insertion in a suitable seat 1 1 a realised in the first half-mould 1 1 of the press mould 10.

In other words, the centring pin 2 has a shape and dimensions such that they allow the insertion inside the seat 1 1 a.

The frangible element 3 is associated with a portion of the centring pin 2 which is distal with respect to the first end 2a, preferably this portion is a second end 2b of the centring pin 2.

Furthermore, the frangible element 3 is stably associable and integral with the second half-mould 12 of the press mould 10, such that it is possible to implement a movement of the frangible element 3 and the centring pin 2 constrained thereto by means of a movement of the second half-mould 12. The frangible element 3 therefore allows constraining the device 1 to the press mould 10, in particular to the second half-mould 12.

Operationally, if the centring pin 2 incorrectly engages the seat 1 1 a, therefore for example impacting against an edge thereof or against another portion of the surface of the first half-mould 1 1 not designed to receive it in insertion, said pin is subjected to a high axial force that could lead to the breaking of the centring pin 2 itself or even to damage other components of a press or press mould 10.

In this context, the frangible element 3 is configured to be subject to breaking so as to allow the centring pin 2 to unload the force to which it is subjected, dispersing it and avoiding the risk of being damaged or damaging other components of the press or press mould 10.

In practice, the frangible element 3 performs the function of a sacrificial element that breaks to ensure that other more delicate, expensive and/or difficult to replace components of a press or press mould 10 are not damaged.

The circuit element 4 is instead associated with the frangible element 3 such that the breaking of the latter causes an electrical transmissibility variation of the circuit element 4 itself.

What is indicated above implies that, if the device operates in an incorrect condition, i.e. in a condition that could lead to damaging part of the device 1 of a press or press mould 10 in which it is installed, the breaking of the frangible element 3 has repercussions on the circuit element 4, changing its electrical transmissibility.

The expression "change its electrical transmissibility thereof" means that the breaking of the frangible element 3 directly and immediately causes a variation in the ability of the circuit element to transfer an electrical signal. To ensure that the breaking of the frangible element 3 produces the maximum possible effect on the circuit element 4, ensuring a proper detection of any breaking which has occurred, the circuit element 4 is at least partially inserted inside the frangible element 3.

To avoid possible interference between the circuit element 4 and the frangible element 3, the device 1 comprises an electrically insulating sheath 4a positioned so as to be interposed between the two.

The device 1 also comprises a detection device 5 which is electrically connected to the circuit element 4, in such a way that it can detect any possible electrical transmissibility variation thereof which can occur following a breaking of the frangible element 4.

This detection device 5 thus allows identifying any breaking of the frangible element 4 in a timely manner through a detection of the changed operating conditions of the circuit element 4.

In particular, the detection device 5 comprises at least one acoustic and/or luminous indicator configured to be activated following an electrical transmissibility variation of the circuit element.

In other words, it is possible to alert an operator of the onset of an incorrect operating condition through appropriate indicators which can either be of the optical type, such as a LED lamp that illuminates, or of the acoustic type, such as a siren.

In this way the operator is put in condition to promptly stop the machine without it continuing to operate and produce non-conforming products.

The detection device 5 can be connected to the control system of the press so as to block it suddenly and automatically following the detection of changed operating conditions of the circuit element 4.

In this way the press mould (10), which requires the movement of the press to produce components, is promptly stopped without continuing to operate and producing non-conforming products.

The detection device 5 can further comprise an electrical power source capable of supplying the electrical circuit that is realised by the connection between the circuit element 4 and the detection device 5 itself and a voltage detector through which the operator can view any changes in the behaviour of the circuit due to variation in the operating conditions of the circuit element 4.

In particular, the breaking of the frangible element 3 can have different effects on the circuit element 4 depending on the specific structural characteristics of the latter.

In fact, in accordance with a first possible embodiment, the circuit element 4 is configured to deform following the breaking of the frangible element 3 without in turn breaking.

In this case the deformation of the circuit element 4 causes a structural variation intended to modify the electrical transmissibility thereof, thus being detected by the detection device 5.

In accordance with this embodiment, the circuit element can comprise a resistor. In accordance with a further possible embodiment, the circuit element 4 is configured to disconnect from the detection device 5 following the breaking of the frangible element 3.

In other words, the detection device 5 is connected to the circuit element 4 such that the perturbation of the latter, generated by the breaking of the frangible element 3, causes the electrical interruption in the circuit element and the detection device.

In this context, the circuit element 4 is connected to the detection device 5 for example by means of clamps, or other similar reversible connection devices, configured to release the terminal of the circuit element 4 following the breaking of the frangible element 3.

Alternatively, in accordance with a further possible embodiment, the circuit element 4 is configured to break following the breaking of the frangible element 3.

In this context, the circuit element 4 has structural characteristics such that the stress to which it is subjected during the breaking of the frangible element 3 causes a breaking which interrupts the electrical circuit in which it is inserted.

In accordance with this embodiment, the circuit element 4 comprises a fuse. Alternatively, instead of breaking, the circuit element 4 can comprise electrical contacts intended to disengage following the breaking of the frangible element 3 so as to switch to define an open circuit.

Advantageously, the frangible element 3 has at least one programmed yielding point such that the breaking does not occur in an uncontrolled manner but only through the separation of defined portions of the frangible element 3, in particular delimited by the positioning profile of at least one programmed yielding point.

Preferably, and with reference to figure 4, the frangible element 3 has at least one programmed yielding point 3a.

Still more preferably, the frangible element 3 has a pair of programmed yielding lines 3a. In particular, the circuit element 4 can be arranged at said at least one programmed yielding point.

In this way it is ensured that the breaking of the frangible element 3 will also at least partially affect the circuit element 4.

In accordance with a preferred embodiment, the frangible element 3 has a substantially cylindrical shape, in which a base surface 3b is intended to allow the connection with the centring pin 2 and preferably also with the second half-mould 12.

In particular, the centring pin 2 is rigidly connected to this base surface 3b in such a manner as to be moved together therewith.

In accordance with this embodiment, the frangible body 3 has a pair of programmed yielding lines 3a, arranged symmetrically with respect to a diameter of the base surface 3b.

In particular, each programmed yielding line 3a has a first portion, arranged as an arc of a circumference around the coupling point of the frangible element 3 with the centring pin 2, and a second portion, which starts from one end of the first and extends towards the edge of the base surface 3b without reaching it.

In this way, in the moment in which the centring pin 2 is subjected to an axial stress greater than the predefined value, the frangible element 3 breaks along the programmed yielding lines 3a.

Consequently, the portion enclosed between the programmed yielding lines 3a (at least partially coincident with the coupling portion with the centring pin 2) is raised like a tab, i.e. rotating around an axis coinciding with the union line "U" between the free ends of the second portions of the two controlled yielding lines 3a.

In this way, the breaking of the frangible element 3 takes place in a controlled manner, avoiding that some of its parts may disperse in an uncontrolled manner within the work area of the press or the same press mould 10.

With reference to figures 1 , 2, 3A, 3B, the device 1 further comprises a pressing member 6 rigidly connected with the centring pin 2 and configured to abut against a portion of the metal sheet“L” when the first end 2a of the centring pin 2 is inserted in the seat 1 1 a of the first half mould 11.

In accordance with a preferred embodiment, the pressing member 6 comprises a pressing body 6a fitted around the centring pin 2.

In particular, this pressing body 6a can comprise a bushing fitted around the centring pin 2.

In use, when the centring pin 2 passes through the metal sheet "L" and engages the seat 1 1 a of the first half-mould 1 1 , thus being inserted at least partially in its interior, the pressing body 6a abuts against the metal sheet "L", in particular against a portion of the surface of the metal sheet “L” which defines an edge of a through seat inside which the centring pin 2 is inserted to reach and engage the seat 1 1 a of the first half-mould 11.

In accordance with a preferred embodiment, the pressing body 6a is axially slidable along the centring pin 2 and the pressing member comprises a contrast spring 6b interposed between the pressing body 6a and the frangible element 3 and configured to exert an elastic force adapted to contrast an approach of the pressing body 6a to the frangible element 3.

In use, the centring pin 2 and the pressing body 6a therefore move rigidly until the metal sheet "L" and the seat 1 1 a of the first half-mould 11 are engaged.

At this point, the centring pin 2 is inserted into the seat 11 a of the first half mould 1 1 while the pressing body 6a, abutting against the metal sheet "L", and being blocked by it, begins to axially slide along the centring pin 2 which continues its progressive insertion inside the seat 1 1 a.

A relative approach movement results between the frangible element 3 and the pressing body 6a which compresses the contrast spring 6b interposed between the two elements.

The contrast spring 6b thus exerts an elastic force which has the effect of pushing the pressing body 6b, crushing it against the metal sheet "L".

In this way it is ensured that during the processing process the metal sheet "L" cannot move, as it is correctly positioned thanks to the centring pin 2 and rigidly maintained in position under the effect of the pressure exerted by the pressing member 6.

Advantageously, the centring device 1 of the present invention allows overcoming the drawbacks highlighted in the known art.

In particular, the introduction of a circuit element 4 associated with the frangible element 3 makes a precise, accurate and timely detection of the state of integrity of the frangible element 3 itself possible, since any breaking of the latter is reflected immediately and directly in a detectable variation of the electrical transmissibility properties of the circuit element 4. This perturbation in the operating conditions of the circuit element 4 can be suitably detected by a detection device 5 forming part of the device 1 or by an appropriate detector connected thereto.

The detection device or the detector thus alert the operator, who can intervene to return the press mould 10 to a correct operating condition.

A further object of the present invention is a press mould 10 for the processing of metal sheets which comprises at least one centring device 1 made in accordance with what is described above, a first half-mould 11 and a second half-mould 12.

The first half-mould 1 1 is configured to retain and convey metal sheets "L" to be processed and defines a work area within which each metal sheet "L" is subjected to the type of processing that the press mould 10 is designed to perform.

In other words, the press mould 10 can be equipped with a variety of known working tools intended to perform different mechanical processing on the metal sheet "L" when it is located within the work area.

The first half-mould 1 1 therefore has at least one seat 1 1 a adapted to receive the centring pin 2 of a respective centring device 1 in insertion.

In other words, the press mould 10 can comprise a plurality of centring devices 1 in accordance with the present invention and the first half-mould 11 will have a number of seats 11 a equal to that of the centring devices 1 used, such that each centring pin 2 is coupled to a respective seat 1 1 a.

The second half-mould 12 in turn has at least one through seat inside which the respective centring device 1 is housed.

In particular, each device 1 is constrained to the respective through seat of the second half-mould 12 through the frangible element 3.

The frangible element 3 therefore has a base surface 3b, facing in use towards the first half-mould 11 , constrained to both the centring pin 2 and the second half-mould 12.

This base surface 3b has a first portion 3c, preferably a central portion, constrained to the centring pin 2 and a second portion 3d, preferably an annular or peripheral portion, which is constrained to the edge of the through seat of the second half-mould 12.

In use, the press mould 10 is configured to allow the approach of the two half-moulds 1 1 , 12 so as to subject the metal sheet "L" to processing, which, being arranged in the work area, is interposed therebetween.

Operationally, the press mould 10 can act in a first regime, or transfer regime, in which the two half-moulds 1 1 , 12 are distanced from each other and it is therefore possible to transfer a metal sheet "L" inside the work area, transporting it and constraining it to the first half-mould 1 1.

Once the metal sheet "L" is in position, the press mould 10 is switched to a second regime, or operating regime, in which the two half-moulds 1 1 , 12 are approached (for example by means of a reciprocal approach movement, or one half-mould is fixed while only the other moves) and the centring pins 2, solidly constrained to the second half-mould 12 by means of the frangible element 3, pass through the metal sheet "L" engaging the respective seats 1 1 a of the first half-mould 1 1.

The pressing body 6a therefore abuts against the metal sheet "L", in particular against its surface facing the second half-mould 12, and under the thrust action exerted by the contrast spring 6b presses it, firmly pressing it against the first half-mould 1 1.

In accordance with a first possible embodiment, the device 1 thus performs the function of centring and retaining the metal sheet“L” in position, while the actual processing process of the same can be accomplished by means of further tools or elements associated with the press mould 10.

In accordance with a further embodiment, the centring device 1 can be further configured to perform a punching process, thus the metal sheet "L" can be transferred intact to the press mould 10, that is to say without the through seats or lead-ins for the passage of the centring pin 2 having been previously realised.

In this case, the frangible element 3 is configured to support the stress resulting from the punching process without breaking, namely deriving from the impact of the centring pin 2 against the surface of the metal sheet "L" to be punched.

It is also possible that the press mould 10 has at least one device 1 designed to solely centre and retain the metal sheet "L" in position and at least one device 1 instead designed to carry out the punching process.

In accordance with a possible embodiment, the circuit element 4 can be electrically connected to a detector, which can optionally be integrated in the press mould 10 or in a press, configured to identify and alert an operator if an electrical transmissibility variation occurs in the circuit element 4.

Alternatively, the circuit element 4 is electrically connected to a power supply circuit of the press, such that an electrical transmissibility variation of the circuit element 4 determines an interruption of the power supply circuit.

In this way, if an incorrect operating situation occurs, such as to cause the breaking of the frangible element 3, the consequent variation in the operating conditions of the circuit element 4 is immediately translated into an interruption of the operation of the mould. In this way it is possible to avoid that the press mould 10 continues to operate, also following the breaking of the frangible element 3, and thus in a condition in which the press mould 10 is not able to properly process the metal sheets "L" passing in the work area.