Device for clamping a workpiece to a machine tool

Abstract

1. An apparatus (1) for clamping a workpiece to a machine tool, comprising: a base frame (2) fixable to a machine tool (M) for machining a workpiece (P); a clamping unit (3); hydraulic actuators (22, 23) with a first chamber (26), the first chamber (26) being capable of being supplied with a first pressurized hydraulic fluid and being connectable to a first sensing device (27) for sensing the pressure of the first hydraulic fluid; and a sensing channel (15) being capable of being supplied with compressed air and being connectable to a sensing sensor (16) for sensing the pressure of the air; the first sensing device (27) and the sensing sensor (16) being connectable to a control system, the control system being adapted to allow machining of the workpiece (P) when the pressure of the first hydraulic fluid and the pressure of the air are simultaneously higher than their respective threshold values.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for clamping a workpiece to a machine tool. [Background technology]

[0002] As is known, in the mass production of mechanical workpieces that require machining on machine tools, the use of systems with a high level of automation is widespread, in which humanoid robots carry the workpieces to be machined to the machine tools, and special devices of the hydraulic type receive the workpieces and clamp them in place to enable their machining.

[0003] When the machining process is completed, the above-mentioned means release the machined workpiece, which is then removed again by the robot.

[0004] The clamping device must be capable of applying very high clamping forces to the workpiece being machined.

[0005] This need is particularly felt, for example, in the automotive industry, where the constant need to optimize production cycles leads to the use of tools that operate at very high speeds, exerting very high forces and vibrations on the workpieces, which must be counteracted by the clamping system.

[0006] Also in the automotive industry, the use of particularly light materials such as aluminum is becoming more widespread, but these cannot guarantee the same resistance during processing as materials such as cast iron and steel.

[0007] Therefore, in addition to applying very large forces, the clamping device must be able to locate predetermined points on the workpiece with high precision and in a reproducible manner each time a new workpiece is mounted on the machine tool, otherwise the large forces applied by the clamping device may actually cause deformation of the workpiece, which impairs the quality of the processing, and there is a risk of obtaining an unacceptable workpiece.

[0008] In such automated systems, the level of operational reliability of the individual components, including the devices for clamping the workpieces, is generally very high.

[0009] Nevertheless, machine workpieces to be machined are sometimes not positioned accurately and precisely, and the clamping device therefor does not fully clamp the workpiece (or fully clamps it but in the wrong position), thereby ruining the entire machining process and risking damage to the workpiece and / or the machine tool and / or the clamping device.

[0010] Similar problems may arise when the workpiece is removed at the end of the machining process: in fact, if the clamping device does not completely and correctly release the machined workpiece, the robot moving the workpiece may pick up (or attempt to pick up) the incompletely released workpiece, with the risk of causing serious damage to the workpiece, and / or the clamping device, and / or the robot itself.

[0011] In this context, it is important to emphasize that in highly automated systems, any malfunction that stops the process can easily turn into loss of productivity, or even worse, into damage to the system and subsequent non-negligible economic losses. Summary of the Invention [Problem to be solved by the invention]

[0012] The main object of the present invention is to devise a device for clamping a workpiece on a machine tool, which makes it possible to avoid performing machining operations on a workpiece that is not properly installed and clamped on the machine tool.

[0013] Another object of the invention is to devise a device for clamping a workpiece to a machine tool that makes it possible to avoid detachments in which the machined workpiece is released incompletely and improperly.

[0014] Finally, among other things, it is an object of the present invention to devise a device for clamping a workpiece to a machine tool with high reliability and precision of operation.

[0015] A further object of the present invention is to devise a device for clamping a workpiece to a machine tool that makes it possible to avoid undesirable defects and damage to the workpiece being machined and / or the tooling of the machine tool and / or the robot moving the workpiece and / or its clamping device.

[0016] Another goal of the present invention is to provide a method for clamping a workpiece to a machine tool, which is to devise an apparatus for clamping a workpiece to a machine tool that overcomes the aforementioned drawbacks of the prior art within a solution that is simple to use, rational, easy, efficient, and affordable. [Means for solving the problem]

[0017] The above-mentioned goal is achieved by the device for clamping a workpiece to a machine tool, which has the features of claim 1.

[0018] Other features and advantages of the present invention will become more apparent from the description of some preferred, but not exclusive, embodiments of an apparatus for clamping a workpiece to a machine tool, shown by way of non-limiting representation in the accompanying drawings. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an axonometric view of a first embodiment of the device according to the invention; FIG. [Figure 2] FIG. 2 is an exploded view of the device of FIG. 1. [Figure 3] 2 is a cross-sectional view of the device of FIG. 1 in a clamped position. [Figure 4] 2 is a cross-sectional view of the device of FIG. 1 in an intermediate transition position. [Figure 5] 2 is a cross-sectional view of the device of FIG. 1 in a released position. [Figure 6] FIG. 2 is a cross-sectional view of a second embodiment of the device according to the invention. [Figure 7] FIG. 10 is an exploded view of a third embodiment of the device according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring in detail to the embodiment shown in Figures 1 to 5, reference numeral 1 generally indicates an apparatus for clamping a workpiece to a machine tool.

[0021] The device 1 is in particular intended to clamp a workpiece P after it has been placed on a worktop L of a machine tool M and before machining begins.

[0022] Preferably, the machine tool M is of a highly automated type, and a humanoid robot is dedicated to loading the workpiece P to be machined and to removing the machined workpiece P.

[0023] It should be noted that the machine tool M is provided with a number of devices 1 arranged in suitable locations and in a reasonable number depending on the shape of the workpiece P and the type of machining to be performed.

[0024] In the drawings and the remainder of this disclosure, unless otherwise indicated, reference will be made to a single apparatus 1 for the sake of simplicity.

[0025] The apparatus 1 comprises at least one base frame 2 which is fixable to the machine tool M, for example to its worktop L, its bedplate or any other part thereof.

[0026] The device 1 comprises at least one clamping unit 3 associated with a base frame 2 in a movable manner between a release position and a clamping position of the workpiece P, passing through a plurality of intermediate transition positions.

[0027] Advantageously, the clamping unit 3 comprises: - at least one bracket element 4 hinged to the mobile part 5 about a first hinge axis A and adapted to contact the workpiece P in the clamping position; at least one hinge connection 6, 7 hinged to the base frame 2 about a second hinge axis B and to the bracket element 4 about a third hinge axis C; Equipped with.

[0028] Advantageously, the hinge axes A, B, C are substantially parallel to one another.

[0029] Due to the shape of the clamping unit 3, in fact in the released position the bracket element 4 is placed in an approximately vertical position, which provides free access to the worktop L for positioning and removing the workpiece P. On the other hand in the clamping position the bracket element 4 is positioned in a substantially horizontal position and over the worktop L, so as to clamp the workpiece P between the bracket element 4 and the worktop L.

[0030] The hinge connection between the bracket element 4 and the movable part 5 about the first hinge axis A is defined by a series of first holes 8 formed in the bracket element 4 and the movable part 5, and by first pins 9 aligned with one another and inserted into the first holes 8.

[0031] For example, the hinge joint 6,7 comprises a first connecting rod 6 and a second connecting rod 7, both hinged about second and third hinge axes B,C.

[0032] Advantageously, the connecting rods 6 , 7 are arranged symmetrically at both ends of the bracket element 4 as well as at both ends of the hinged portion 10 of the base frame 2 .

[0033] The hinge between the connecting rods 6, 7 and the base frame 2 about the second hinge axis B is defined by a series of second holes 11 formed in the connecting rods 6, 7 and the hinged part 10, and by second pins 12 aligned with one another and inserted into the second holes 11.

[0034] On the other hand, the hinge between the connecting rods 6, 7 and the bracket element 4 about the third hinge axis C is defined by a series of third holes 13 formed in the connecting rods 6, 7 and the bracket element 4, and by third pins 14 inserted into the mutually aligned third holes 13.

[0035] The device 1 comprises at least one sensing channel 15 formed in either the base frame 2 or the clamping unit 3 .

[0036] The sensing channel 15 can be supplied with compressed air and can be connected to a sensing sensor 16 adapted to sense the pressure of this compressed air.

[0037] More particularly, the sensing channel 15 is connected to a first pneumatic circuit 17 adapted to supply compressed air.

[0038] The first pneumatic circuit 17 is provided with a sensing sensor 16 (such as a compression switch) by means of which the air pressure inside the sensing channel 15 can be known.

[0039] The sensing channel 15 is hermetically sealed when the clamping unit 3 is in the clamping position and is open to the outside at least when the clamping unit 3 is in the intermediate transition position.

[0040] Thus, when the clamping unit 3 is in the clamping position, the air supplied under pressure into the sensing channel 15 remains trapped within the sensing channel itself, and its pressure tends to increase, but in the intermediate transition position, the air is able to vent to the outside, and its pressure tends to decrease.

[0041] Conveniently, the sensing channel 15 is formed in the base frame 2 and the hinge joints 6,7 are configured to open and close the sensing channel 15 based on the position of the hinge joints 6,7.

[0042] More specifically, the sensing channel 15 emerges at a first surface 18 of the base frame 2 , for example formed at the hinge portion 10 .

[0043] The first connecting rod 6 rotatably rests on a first surface 18 and is provided with a first ventilation recess 19 .

[0044] Associated with the first connecting rod 6 are first pre-installation means 20, 21. The pre-installation means 20, 21 are adapted to keep the first connecting rod 6 in sealing contact at the first surface 18 and to keep the sensing channel 15 normally closed.

[0045] The first pre-assembly means 20, 21 consist for example of a cup spring 20 and a washer 21 attached to the second pin 12 and the third pin 14 and act to press the connecting rods 6, 7 against the hinged portion 10 and against the bracket element 4.

[0046] In this way, on the one hand, it is ensured that the gaps existing between the base frame 2, the connecting rods 6, 7 and the bracket element 4 are reconfigured to achieve a more stable and precise assembly operation, and on the other hand, a sealed closure of the sensing channel 15 is achieved without the need for rubber seals or other flexible materials.

[0047] The opening of the sensing channel 15 actually occurs only when the first ventilation recess 19 at least partially overlaps the sensing channel 15, which occurs when the clamping unit 3 moves to the intermediate transition position as described above.

[0048] As described and shown, sensing channel 15 is formed in base frame 2, and hinge connections 6, 7 are configured to open and close sensing channel 15. However, alternative embodiments cannot be excluded in which sensing channel 15 is positioned differently and its opening and closing is achieved by components other than hinge connections 6, 7.

[0049] For the movement of the clamping unit between the release position and the clamping position, the device 1 comprises at least one hydraulic actuator 22, 23. The hydraulic actuator 22, 23 is provided with a fixed part 24 associated with the base frame 2 and a movable part 5 connected to the clamping unit 3.

[0050] The moving part 5 of the hydraulic actuators 22, 23 advantageously coincides with the moving part to which the bracket element 4 is hinged about the first hinge axis A.

[0051] For example, the hydraulic actuator 22, 23 comprises a cylinder 22 defining a fixed portion 24, and a stem portion 23. The stem portion 23 is provided with a plunger 25 that exits the cylinder 22 and defines the movable portion 5.

[0052] The cylinders 22 of the hydraulic actuators 22 , 23 are formed in a single piece with the base frame 2 .

[0053] Inside the cylinder, the hydraulic actuator 22, 23 comprises at least a first chamber 26 to which a first pressurized hydraulic fluid is supplied, making it possible to move the clamping unit 3 from a release position to a clamping position.

[0054] Within this disclosure, hydraulic fluid refers to any liquid in a liquid state (and therefore ideally incompressible) that is used as a carrier for transmitting energy in a hydraulic circuit. Preferably, the hydraulic fluid consists of conventional synthetic lubricating oil, although alternative embodiments, which may be mineral oil, vegetable oil, water, etc., cannot be excluded.

[0055] The first chamber 26 operates on one side of the plunger 25 .

[0056] The first chamber 26 is connectable to a first sensing device 27 for sensing the pressure of the first pressurized hydraulic fluid.

[0057] More specifically, the first chamber 26 is connected to a first duct 28 formed in the cylinder of the hydraulic actuator 22, 23, which in turn is connected to a first hydraulic circuit 29 adapted to supply a first hydraulic fluid.

[0058] The first hydraulic circuit 29 is provided with a first sensing sensor 27 (such as a compression switch) by means of which the pressure of the first pressurized hydraulic fluid inside the first chamber 26 can be known.

[0059] The first sensing device 27 and the sensing sensor 16 are connectable to a control system adapted to allow machining of the workpiece P when the pressure of the first hydraulic fluid under pressure in the first chamber 26 and the pressure of the air in the sensing channel 15 are simultaneously higher than their respective threshold values.

[0060] The control system is not shown, but may comprise, for example, a control unit (electronic, hydraulic, or a combination of both) that manages the operation of the machine tool M.

[0061] Indeed, to authorize the start of machining on the workpiece P, the control system performs a double check: the control system checks whether the first chamber 26 is pressurized, i.e. whether it is supplied with the first pressurized hydraulic fluid; and The control system checks whether the sensing channel 15 is pressurized, i.e. whether the sensing channel 15 is closed and air is not vented to the outside.

[0062] If both of these situations occur simultaneously, the control system senses that the clamping unit is correctly positioned in the clamping position and authorizes the tool of the machine tool M to perform the machining operation. These situations are shown in Figure 3.

[0063] On the other hand, Figure 4 shows a situation in which the workpiece P is installed on the machine tool M in an incorrect position and the bracket element 4 does not reach the clamping position because the bracket element 4 is in contact with the workpiece P when the clamping unit 3 is still in one of the intermediate transition positions.

[0064] Under this circumstance, the first hydraulic fluid in the first chamber 26 is pressurized and the first sensing device 27 detects this pressure, but on the other hand, the first vent recess 19 at least partially overlaps the sensing channel 15, the compressed air vents to the outside, and the sensing sensor 16 detects that the pressure in the sensing channel 15 is not higher than the threshold value.

[0065] Therefore, under this circumstance, the control system knows that the clamping unit 3 has not reached the clamping position and does not allow the machining operation to start.

[0066] Disallowance protects the workpiece P and the machine tool M by preventing operations that are potentially dangerous to the integrity of the machine tool M from being performed.

[0067] In response to the disallowance, a protocol may be initiated, such as repositioning of the workpiece P and / or operator intervention, aimed at restoring normal working conditions.

[0068] In the embodiment shown in Figures 1 to 5, the hydraulic actuator is of the double-acting type and comprises at least a second chamber 30. The second chamber 30 can be supplied with a second pressurized hydraulic fluid for moving the clamping unit 3 from the clamping position to the release position.

[0069] Preferably, the second hydraulic fluid is the same as the first hydraulic fluid used as a carrier to set under pressure the first chamber 26. In other words, the same hydraulic fluid may be pumped into the first chamber 26 and the second chamber 30 as needed.

[0070] However, an alternative embodiment cannot be excluded in which two different hydraulic fluids are used.

[0071] The second chamber 30 operates on one side of the plunger 25 opposite the first chamber 26 .

[0072] The second chamber 30 is connectable to a second sensing device 31 for pressure in the second pressurized hydraulic fluid.

[0073] More specifically, the second chamber 30 is connected to a second duct 32 formed in the cylinder of the hydraulic actuator 22, 23, which in turn is connected to a second hydraulic circuit 33 adapted to supply a second hydraulic fluid.

[0074] The second hydraulic circuit 33 is provided with a second sensing sensor 31 (such as a compression switch) by which the pressure of the second pressurized hydraulic fluid inside the second chamber 30 can be known.

[0075] Advantageously, the sensing channel 15 is hermetically closed when the clamping unit is in the released position, and the second sensing device 31 and the sensing sensor 16 are connectable to a control system adapted to allow the workpiece P to be picked up from the machine tool M when the pressure of the second hydraulic fluid in the second chamber 30 and the pressure of the air in the sensing channel 15 are simultaneously higher than their respective threshold values.

[0076] The control system intended to allow the picking up of the workpiece P advantageously coincides with the control system intended to allow the machining of the workpiece P and is composed, for example, of a control unit that manages the operation of the machine tool M.

[0077] Indeed, to authorize the picking up of the workpiece P after the completion of the machining operation, the control system performs a double check: the control system checks whether the second chamber 30 is pressurized, i.e. whether it is supplied with the second pressurized hydraulic fluid; and The control system checks whether the sensing channel 15 is pressurized, i.e. whether the sensing channel 15 is closed and air is not vented to the outside.

[0078] If both of these situations occur simultaneously, then the control system senses that the clamping unit is correctly positioned in the release position, allowing robot movement of the workpiece P to pick it up from the machine tool M. Such a situation is shown in FIG.

[0079] The apparatus 1 described and shown in Figures 1-5 has several components that come into contact with hydraulic fluid, and therefore special seals are placed at various points in the apparatus 1. For ease of illustration, they are commonly identified by the reference numeral 34.

[0080] Figure 6 shows a second embodiment of the invention, in which the device 1 is identical to the embodiment of figures 1 to 5, except that the hydraulic actuators 22, 23 are of the single-acting type and are provided with at least one rebound element 35 for moving the clamping unit 3 from the clamping position to the release position.

[0081] The recoil element 35 consists, for example, of a helical spring acting on the plunger 25 on the side opposite to the first chamber 26 .

[0082] In this embodiment, the apparatus 1 is provided with a first chamber 26 connected to a first sensing device 27 but without a second chamber 30 and a second sensing device 31 .

[0083] Therefore, with the device 1 of Figure 6 it is not possible to reliably recognize the achievement of the release position by the clamping unit 3, as was the case in the embodiment of Figures 1 to 5. However, it is still possible to reliably identify the start of the clamping position and the achievement of the machining operation when it is checked that the pressure of the first hydraulic fluid in the first chamber 26 and the air pressure in the sensing channel 15 are simultaneously higher than their respective threshold values.

[0084] A third embodiment of the invention is shown in Figure 7. Here the hydraulic actuators 22, 23 are again of the single-acting type and are provided with a rebound element 35 which enables the clamping unit 3 to move from the clamping position to the release position.

[0085] However, unlike the embodiment of FIG. 6, the device 1 comprises at least one auxiliary channel 36 located either in the base frame 2 or in the clamping unit 3 .

[0086] The auxiliary channel 36 can be supplied with compressed air and can be connected to an auxiliary sensor 37 adapted to sense the pressure of this compressed air.

[0087] More particularly, the auxiliary channel 36 is connected to a second pneumatic circuit 38 adapted to supply air under pressure.

[0088] The second pneumatic circuit 38 is provided with an auxiliary sensor 37 (such as a compression switch) by means of which the air pressure inside the auxiliary channel 36 can be known.

[0089] The auxiliary channel 36 is hermetically sealed when the clamping unit 3 is in the release position and is open to the outside at least when the clamping unit 3 is in the intermediate transition position.

[0090] Thus, when the clamping unit 3 is in the release position, the air supplied under pressure into the auxiliary channel 36 remains trapped within the sensing channel itself and its pressure tends to increase, but in the intermediate transition position, the air is able to vent to the outside and its pressure tends to decrease.

[0091] Conveniently, the auxiliary channel 36 is formed in the base frame 2 and the hinge connections 6,7 are shaped to open and close the auxiliary channel 36 based on the position of the hinge connections 6,7.

[0092] More specifically, the auxiliary channel 36 emerges in a second surface 39 of the base frame 2 , the second surface 39 being formed in the hinge portion 10 opposite the first surface 18 .

[0093] The second connecting rod 7 rotatably rests against the second surface 39 and is provided with a second ventilation recess 40 .

[0094] The second pre-installation means is associated with the second connecting rod 7. The second pre-installation means is adapted to keep the second connecting rod 7 in sealing contact at the second surface 39 and to keep the auxiliary channel 36 normally closed.

[0095] The second pre-installed means usefully coincides with the first pre-installed means 20,21.

[0096] In effect, the cup spring 20 and washer 21 act to press both connecting rods 6 , 7 against the hinge portion 10 and bracket element 4 .

[0097] The opening of the auxiliary channel 36 actually occurs only when the second ventilation recess 40 at least partially overlaps the auxiliary channel 36, which occurs when the clamping unit 3 moves to the intermediate transition position as described above.

[0098] 7, the first sensing device 27 and the auxiliary sensor 37 are connectable to a control system adapted to allow the workpiece P to be picked up from the machine tool M when the pressure of the first hydraulic fluid in the first chamber 26 is below a respective threshold value and, simultaneously, when the pressure of the air in the auxiliary channel 36 is above a respective threshold value.

[0099] Furthermore, the control system intended to allow the workpiece P to be picked up in the embodiment of FIG. 7 may advantageously coincide with the control system intended to allow the workpiece P to be machined and may be constituted, for example, by a control unit that manages the operation of the machine tool M.

[0100] Indeed, to authorize the picking up of the workpiece P after the completion of the machining operation, the control system performs a double check: the control system checks whether the first chamber 26 is not pressurized, i.e. whether it is not supplied with the first pressurized hydraulic fluid; and The control system checks whether the auxiliary channel 36 is pressurized, i.e. whether the auxiliary channel 36 is closed and air cannot vent to the outside.

[0101] If both of these situations occur simultaneously, then the control system senses that the clamping unit 3 is correctly positioned in the release position, allowing robot movement of the workpiece P to pick up the workpiece P from the machine tool M.

Claims

1. A device (1) for clamping a workpiece to a machine tool, comprising: At least one base frame (2) that can be fixed to a machine tool (M) for machining a workpiece (P); at least one clamping unit (3) connected to the base frame (2) in a movable manner passing through intermediate transition positions between a release position and a clamping position of the workpiece (P); at least one hydraulic actuator (22, 23) provided with a fixed part (24) fixed to the foundation frame (2) and a movable part (5) connected to the clamping unit (3), the at least one hydraulic actuator (22, 23) comprising at least a first chamber (26) to which a first pressurized hydraulic fluid can be supplied in order to move the clamping unit (3) from the release position to the clamping position, the first chamber (26) being connectable to a first sensing device (27) for sensing the pressure of the first pressurized hydraulic fluid; Equipped with The device (1) comprises: at least one sensing channel (15) formed in at least one of the base frame (2) and the clamping unit (3), the sensing channel (15) being capable of being supplied with compressed air and being connectable to a sensing sensor (16) for sensing the pressure of the compressed air, the sensing channel (15) being hermetically sealed when the clamping unit (3) is in the clamping position and communicating with the outside when the clamping unit (3) is in at least the intermediate transition position; the first sensing device (27) and the sensing sensor (16) are connectable to a control system, the control system being adapted to allow processing of the workpiece (P) when the pressure in the first chamber (26) and the pressure of the compressed air in the sensing channel (15) are simultaneously higher than their respective threshold values; the hydraulic actuators (22, 23) are of double-acting type and comprise at least a second chamber (30) to which a second pressurized hydraulic fluid can be supplied in order to move the clamping unit (3) from the clamping position to the release position, the second chamber (30) being connectable to a second sensing device (31) for the pressure of the second pressurized hydraulic fluid; the sensing channel (15) is hermetically sealed when the clamping unit (3) is in the release position; and the second sensing device (31) and the sensing sensor (16) are connectable to a control system, the control system being adapted to allow the workpiece (P) to be removed from the machine tool (M) when the pressure of the second pressurized hydraulic fluid in the second chamber (30) and the pressure of the compressed air in the sensing channel (15) are simultaneously higher than their respective threshold values. Device (1).

2. the device (1) comprises at least one auxiliary channel (36) located in at least one of the base frame (2) or the clamping unit (3), the auxiliary channel (36) being capable of being supplied with compressed air and being connectable to an auxiliary sensor (37) adapted to sense the pressure of the compressed air in the auxiliary channel (36), the auxiliary channel (36) being hermetically sealed when the clamping unit (3) is in the release position and communicating with the outside when the clamping unit (3) is in the intermediate transition position; and 2. The apparatus (1) according to claim 1, characterized in that the first sensing device (27) and the auxiliary sensor (37) are connectable to a control system, the control system being adapted to allow the workpiece (P) to be picked up from the machine tool (M) when the pressure of the first pressurized hydraulic fluid in the first chamber (26) is lower than a threshold value and, at the same time, when the pressure of the compressed air in the auxiliary channel (36) is higher than a threshold value.

3. 3. The device (1) according to claim 1 or 2, characterized in that the hydraulic actuator (22, 23) comprises a cylinder (22) having the fixed part (24) and holding the movable part (5) out of the cylinder (22).

4. The tightening unit (3) at least one bracket element (4) hinged to said movable part (5) about a first hinge axis (A) and adapted to contact said workpiece (P) in said clamping position; at least one hinge connection (6, 7) hinged to said foundation frame (2) about a second hinge axis (B) and hinged to said bracket element (4) about a third hinge axis (C); Device (1) according to any one of claims 1 to 3, characterised in that the hinge axes (A, B, C) are parallel to one another.

5. 5. The device (1) according to claim 4, characterized in that the hinged joints (6, 7) comprise a first connecting rod (6) and a second connecting rod (7), both hinged about the second and third hinge axes (B, C).

6. 6. The device (1) according to claim 4 or 5, characterized in that the sensing channel (15) is formed in the base frame (2) and the hinge connections (6, 7) are shaped to open and close the sensing channel (15) according to the position of the hinge connections (6, 7).

7. 10. The device (1) according to claim 5 or claim 6 when referring to claim 5, characterized in that the first connecting rod (6) rotatably rests on a first surface (18) of the base frame (2) on which the sensing channel (15) is exposed and which is provided with a first ventilation recess (19), the first connecting rod (6) is fitted with first pre-installed means (20, 21) adapted to keep the connecting rod (6) in sealing contact with the first surface (18) to keep the sensing channel (15) normally closed, and the opening of the sensing channel (15) is achieved when the first ventilation recess (19) at least partially overlaps the sensing channel (15).

8. The device (1) according to claim 5 which relies on claim 2, claim 6 which relies on claim 5 which relies on claim 2, or claim 7 which relies on claim 2, characterized in that the second connecting rod (7) rotatably rests on a second surface (39) of the base frame (2) on which the auxiliary channel (36) is exposed and which is provided with a second ventilation recess (40), the second connecting rod (7) is fitted with second pre-installed means adapted to keep the connecting rod (7) in sealing contact at the second surface (39) so as to keep the auxiliary channel (36) normally closed, and the opening of the auxiliary channel (36) is effected when the second ventilation recess (40) at least partially overlaps the auxiliary channel (36).

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