Device for holding a sheet and related method

Abstract

A holding unit (10) for holding a sheet (200), comprising: a stabilizer device (11) having gripping members (12, 13), at least one of which is movable relative to the other along a gripping and releasing axis (Z) for holding the sheet (200); and a drive unit (14) comprising an actuator (16) associated with the movable gripping member (12, 13) and a feed circuit (17) configured to feed the actuator (16).

Description

Technical Field

[0001] The present invention relates to a holding unit for holding the periphery of a sheet material (such as a sheet made of glass or a glass substitute material), especially when processing the periphery edge thereof, and a corresponding holding method. Such a unit is usually inserted into a device for processing sheets. Background Art

[0002] Equipment for processing pre-cut glass sheets of various shapes (rectangular, triangular, trapezoidal, etc.) and then further processing (usually removing material) to produce finished or semi-finished products is well known.

[0003] The known apparatuses generally comprise one or more sheet moving units and at least one fixed processing unit having a processing head which is slidable in a substantially vertical direction and is provided with one or more tools.

[0004] Such devices also comprise a holding unit equipped with an angularly adjustable stabilizer device, which is attached to the processing head and is able to be temporarily coupled to the peripheral edge of the sheet in order to fix its position and avoid unnecessary and harmful vibrations.

[0005] The stabilizer device includes a pair of jaws or clamping members on which are mounted idler wheels or other holding elements, which members have an opening and closing movement so that the idler wheels can hold the sheet of material.

[0006] One of the main problems affecting existing stabilizer devices is that it is difficult to achieve a predetermined and optimal thrust and calibration value on the sheet. In fact, the unevenness of the sheet surface and the variations in thickness values ​​(i.e. non-uniformity) can determine an unbalanced situation of the thrust exerted by the clamping members on the sheet itself.

[0007] In addition to shortening the life of the tool, this can result in a poor quality finished product, which can manifest itself in the following aspects: dimensional tolerances are not met; surface finish is mediocre or unacceptable; any nanotechnology coatings are damaged; sheets sometimes break during processing, especially when the sheet thickness is reduced; and sometimes certain parts of the equipment are damaged.

[0008] A conventional machine for processing the peripheral edge of a sheet is described in European patent EP3170622A1. Other solutions that teach how to hold a sheet are described in prior art documents (US4716686A, EP3106275A1 and CN111882991A).

[0009] Therefore, there is a need to improve a unit for holding sheets and a related method to overcome at least one of the shortcomings of the prior art.

[0010] One purpose of the present invention, corresponding to the technical problem to be solved, is to provide a unit and a related method for holding a sheet during processing, which method can ensure correct and uniform holding of the sheet, and will not affect the quality of the finished product even in the event of thickness changes or surface unevenness.

[0011] 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

[0012] The invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the invention or variants to the main inventive idea.

[0013] According to the above-mentioned purpose, and in a new and original way to solve the technical problem, and also to achieve considerable advantages compared with the prior art, the holding unit for holding the sheet material according to the present invention comprises:

[0014] - a stabilizer device having clamping members, at least one of which is movable relative to the other clamping member along a clamping and releasing axis (Z) in order to retain said sheet; and

[0015] - a drive unit comprising an actuator associated with the movable gripping member and a feed circuit configured to feed the actuator.

[0016] According to one aspect of the present invention, the feed circuit comprises:

[0017] - a delivery line and a return line fluidly connected to the actuator;

[0018] - a first solenoid valve for controlling the delivery and return lines, wherein the delivery line is configured to supply the actuator with an advantageously incompressible liquid;

[0019] - Additional solenoid valves, wherein a first additional solenoid valve is located on the delivery line and a second additional solenoid valve is located on the return line between the first solenoid valve and the actuator.

[0020] Here and in the following description, the term "incompressible liquid" refers to a fluid with low or very low compressibility, such as hydraulic oil. In its basic expression, compressibility represents the change in a unit volume of a liquid caused by a unit increase in pressure. Therefore, an incompressible liquid is a liquid with a compressibility value of less than about 1% (expressed as the percentage change in volume when the pressure changes by 100 bar at 25°C).

[0021] The holding unit configured in this way ensures optimal holding of the sheet even in the presence of thickness variations or surface irregularities. In fact, once the sheet holding position has been reached, closing the feed circuit by means of an additional valve makes it possible to isolate the circuit section on the actuator side. The latter remains locked in position because the liquid (for example oil) that feeds it is an incompressible fluid that completely fills this section of the circuit and the actuator chamber, allowing the actuator rod to remain in position regardless of possible stresses that may arise in contact with the sheet surface due to variations in sheet thickness or irregularities.

[0022] According to another aspect of the invention, the supply line and the return line can be fluidically connected to a compressed air and exhaust line on the other side relative to the connection side of the actuator.

[0023] According to another aspect of the invention, the first solenoid valve is advantageously a pneumatic solenoid valve for pneumatic control of the supply and return lines.

[0024] According to another aspect of the present invention, a fluid containing liquid and gas can be fed into the delivery pipeline and the return pipeline. The liquid can be hydraulic oil, and the gas can be air.

[0025] According to another aspect of the present invention, the feed circuit may include an air-oil separator, between the actuator and the first solenoid valve, a first air-oil separator is located on the delivery pipeline, and a second air-oil separator is located on the return pipeline.

[0026] According to another aspect of the present invention, the feed circuit comprises a pressure regulator, which is arranged on the delivery pipeline and located between the first solenoid valve and the corresponding gas-oil separator.

[0027] According to another aspect of the present invention, the additional solenoid valve is an oil-powered solenoid valve and is located between the corresponding gas-oil separator and the actuator.

[0028] According to an embodiment variant of the invention, only one liquid can be fed into the delivery line and only one gas can be fed into the return line.

[0029] According to another aspect of the invention, the holding unit may comprise at least one control sensor associated with the clamping members and configured to measure a control parameter of the movement of one or both of the clamping members.

[0030] According to another aspect of the present invention, the control sensor is a displacement sensor configured to detect the distance between the clamping members.

[0031] According to another aspect of the invention, the control sensor may be a vibration sensor configured to detect a vibration state of one or both of the clamping members in terms of velocity and / or acceleration.

[0032] According to another aspect of the present invention, the control sensor is attached to the movable clamping member.

[0033] According to another aspect of the present invention, the holding unit includes a controller, which is operably connected to at least the first solenoid valve and the additional solenoid valve to realize their opening / closing operations, and is operably connected to the pressure regulator and the at least one control sensor.

[0034] According to another aspect of the invention, the controller is configured to control the pressure regulator in feedback based at least on a signal feedback received from the at least one control sensor to process a subsequent sheet.

[0035] An embodiment of the present invention also refers to a method for holding the sheet by reciprocating the clamping members along the clamping and releasing axes, wherein at least one of the clamping members is driven by the actuator, which is a hydraulic actuator and is supplied with a preferably incompressible liquid (especially oil) by the feed circuit.

[0036] According to one aspect of the invention, once a level corresponding to the thickness is reached and at least one of the clamping components has a predetermined thrust value, the drive circuit is switched from open to closed by the additional oil-powered solenoid valve to keep at least a portion of the drive circuit, including the actuator, completely invaded by the liquid, thereby stabilizing the reciprocating position of the clamping member.

[0037] According to another aspect of the invention, the method provides for measuring a control parameter of the movement of one or both of the gripping members by means of at least one control sensor associated with one or both of the gripping members.

[0038] According to another aspect of the invention, the method provides for controlling the movement of one or both of the clamping members by a controller, wherein the controller is operably connected to at least the first solenoid valve and the additional solenoid valve to achieve their opening / closing operation, and is operably connected to the pressure regulator and the at least one control sensor.

[0039] According to another aspect of the invention, the controller is configured to control the pressure regulator in feedback based at least on a signal feedback received from the at least one control sensor to process a subsequent sheet.

[0040] According to another aspect of the present invention, the liquid fed into the drive circuit is contained in an air-oil separator. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] These and other aspects, features and advantages of the invention will become apparent from the description of certain embodiments thereof given by way of non-limiting example with reference to the accompanying drawings, in which:

[0042] - Figure 1 is a schematic diagram of an apparatus for processing a sheet material according to the present invention, the apparatus comprising a holding unit;

[0043] - Figure 2 is a schematic diagram of a holding unit according to the present invention.

[0044] We must expressly point out that the words and terms used in this specification, as well as the illustrations described in the accompanying drawings, have the sole purpose of better illustrating and explaining the present invention and their function is to provide a non-limiting example of the present invention, as the scope of protection is defined by the claims.

[0045] To facilitate understanding, where possible, the same reference numerals have been used to designate the same elements common to the figures. It should be understood that elements and features of one embodiment may be conveniently combined or incorporated into other embodiments without further clarification. DETAILED DESCRIPTION

[0046] Reference Figure 1 , which shows an apparatus 100 according to the invention, which is configured for material removal processing of a sheet 200 made of glass (or more generally a sheet of a brittle material having glass-like properties).

[0047] Reference Figure 1 and Figure 2 Each sheet 200 has a first side or front face 210, an opposing second side or rear face 211, and a peripheral edge 212 having a known or previously measured thickness T. Figure 2 ). The side surfaces 210, 211 are substantially flat and may be rectangular, circular, elliptical, curved, trapezoidal, triangular or polygonal or a combination thereof.

[0048] For example, from Figure 1 As can be seen in FIG. 2 , in the case of a triangular sheet, the peripheral edge 212 may be defined by a front side 212A′, an opposing rear side 212B′, and an underside 212C′.

[0049] According to some embodiments, the apparatus 100 comprises a feeding section A for providing one or more sheets 200 to be processed, and a discharging section B, at which the processed sheets 200 are discharged from the apparatus 100 .

[0050] The apparatus 100 comprises a processing plane P, such as Figure 1 As shown by the dashed line, the plane is substantially vertical and the sheet 200 lies on the plane relative to the side 210 .

[0051] The device 100 includes a first moving unit 111 (for example, a roller-type moving unit 119, 120), which includes: a feed conveyor 117 and a discharge conveyor 118, which are configured to move one or more of the sheets 200 along a forward direction F on a working plane P, thereby supporting and dragging the sheet from below, and the forward direction F leads from a feed section A to a discharge section B.

[0052] The device 100 also includes a second mobile unit 112 (slide-type mobile unit 121), which has a suction cup 122, and the suction cup 122 is configured to hold and move the sheet 200 on the processing plane P along the forward direction F, that is, to drag it laterally relative to its first side 21O (that is, the front surface) or more advantageously relative to its second side 211 (that is, the rear surface).

[0053] The first and second moving units 111 , 112 can be activated simultaneously to coordinate the movement of the same sheet 200 , or can be activated independently.

[0054] The apparatus 100 comprises at least one processing unit 113 which is arranged vertically or inclined, is substantially parallel to the working plane P and is arranged at a middle section C between the feeding section A and the discharging section B.

[0055] The machining unit 113 comprises a machining head 123 and a guide rail 124 which extends along a machining axis Y and along which the machining head 123 is slidable.

[0056] The machining unit 113 comprises a machining tool 125 associated with a machining head 123. The machining tool 125 is fastened on a spindle associated with the machining head 123 by means of a key in a manner known per se.

[0057] In the embodiment described herein, the machining tool 125 is a grinding wheel. However, it cannot be excluded that the machining tool 125 is configured to perform other machining operations.

[0058] Special References Figure 2The apparatus 100 further comprises a holding unit 10 for holding the peripheral edge 212 of the sheet 200 during its processing. Certain parts of the holding unit 10 are associated with the processing unit 113, as will be described in more detail below.

[0059] The device 100 comprises a central control unit 116 which is configured at least to manage the first mobile unit 111 , the second mobile unit 112 and the processing unit 113 (including a working head 123 with a processing tool 125 and a holding unit 10 ) to ensure that optimized processing is performed on the sheet 200 .

[0060] The holding unit 10 according to the invention comprises a stabilizer device 11 ( Figure 1 and Figure 2 ), the stabilizer device 11 is provided with a first clamping member 12 and a second clamping member 13 which are relative and facing each other, and is configured to clamp the peripheral edge 212 of the sheet 200 therebetween near the processing tool 125, thereby stabilizing its position to avoid vibration during processing.

[0061] The stabilizer device 11 can be oriented according to a certain angle. The rotation according to the orientation angle is used to correctly orient the first and second clamping members 12 , 13 relative to the sheet 200 .

[0062] The first and second clamping members 12, 13 each comprise a support element 12a, 13a, which may be a jaw, for example, and at least one respective contact element 12b, 13b, which in the present case is a wheel or an idler roller, the axis of which is orthogonal to the axis of rotation of the machining tool 125. The contact element 12b, 13b preferably has a cylindrical shape and a peripheral coating made of an elastic material.

[0063] The contact elements 12b, 13b are configured to hold the sheet 200 in a sliding manner in contact with at least two corresponding contact areas located on the first and second sides 210, 211. In a more general sense, these contact areas may correspond to respective contact zones, having a rectangular or other shape, which are more or less extended depending on the degree of deformation constituted by the contact elements 12b, 13b or their coatings.

[0064] During use, the first and second clamping members 12, 13 are located on one side and the other side of the sheet 200 respectively, and at least one of them can be selectively moved along a clamping and release axis Z orthogonal to the sides 210, 211 according to a suitably calibrated relative approach / advance movement.

[0065] exist Figure 2In the example of , the second clamping member 13 is movable, whereas the first clamping member is fixed.

[0066] The holding unit 10 comprises a drive unit 14 operatively connected to the stabilizer device 11 to determine the movement of one or both of the clamping members 12 , 13 along the clamping and releasing axis Z.

[0067] The drive unit 14 comprises an actuator 16 associated with the movable gripping members 13 , 12 and a feed circuit 17 configured to feed the actuator 16 with material.

[0068] The actuator 16 is in particular a hydraulic cylinder, in particular an oil-powered hydraulic cylinder.

[0069] The actuator 16 is a double-acting actuator.

[0070] The actuator 16 comprises a jacket 16a and a movable plunger 16b in the jacket 16a. The movable plunger 16b is connected to the movable clamping members 13, 12 and divides the interior of the jacket into two variable volume compartments, namely a first compartment 16a', called a "positive pressure compartment", and a second compartment 16a", called a "negative pressure compartment".

[0071] The feed circuit 17 comprises a delivery line A and a return line B, one side of which is fluidically connected to the actuator 16 and the other side is fluidically connected to the compressed air line and the air exhaust line. On the actuator 16 side, the delivery line A is fluidically connected to the first compartment 16a' and the return line B is fluidically connected to the second compartment 16a".

[0072] The feed circuit 17 includes a first pneumatic solenoid valve 18, which is located on the delivery line A and the return line B, between the actuator 16 and the compressed air and discharge lines; and two air-oil separators 19, 20, wherein the first air-oil separator is located on the delivery line A, and the second air-oil separator is located on the return line B, between the actuator 16 and the first solenoid valve 18.

[0073] The air-oil separators 19 , 20 are actually two tanks in which a certain amount of liquid, such as oil, required for the operation of the actuator 16 is stored. The air present therein is managed under pressure to move the oil towards the actuator 16 .

[0074] According to a variant, the first solenoid valve 18 can be replaced by two independent solenoid valves, which are located on the supply line A and the return line B, respectively.

[0075] The feed circuit 17 further comprises two additional oil-powered solenoid valves 22 and 23, wherein the first oil-powered solenoid valve 22 is located on the delivery line A, and the second oil-powered solenoid valve 23 is located on the return line B, and are respectively located between the gas-oil separators 19 and 20 and the actuator 16. The portions of the delivery line A and the return line B (including the two compartments 16a′ and 16a″) contained between the two additional solenoid valves 22 and 23 and the actuator 16 are preferably completely filled with oil, at least in the state of holding the sheet 200, in order to maintain stable holding of the sheet 200, because oil is an incompressible fluid, or has the characteristics of low or very low compressibility.

[0076] exist Figure 2 In the example shown, the first solenoid valve 18 is a 5 / 3 center open solenoid valve, while the two additional solenoid valves 22 , 23 are 2 / 2 normally closed monostable solenoid valves.

[0077] The solenoid valves 22 , 23 are normally in a closed state, but can be selectively (especially simultaneously) switched to an open state.

[0078] The feed circuit 17 may further include a pressure regulator 24 , which is disposed on the delivery line A between the first solenoid valve 18 and the corresponding gas-oil separator 19 .

[0079] The holding unit 10 may be equipped with its own controller 30, or it may be directly managed by the central control unit 116 of the device 100. Therefore, the controller 30 may coincide with the central control unit 116, or the latter may be two independent and separate components, but in any case, they must exchange information with each other to achieve the information transfer related to the overall process management.

[0080] exist Figure 2 In the example shown, the solenoid valves 18 , 22 , 23 are operatively connected to a controller 30 which determines the opening or closing of the clamping members 12 , 13 according to the position of the sheet 200 in the advancing direction F (eg received from the central control unit 116 ).

[0081] The pressure regulator 24 may also be operably connected to a controller 30 .

[0082] The controller 30 sends a signal containing the required pressure value to the pressure regulator 24, depending on the thickness T of the sheet 200 and its material type (resistance to concentrated orthogonal loads), the degree of deformation of the contact elements 12b, 13b or their coating, and the freedom of mutual sliding between the contact elements 12b, 13b and the sheet 200 (without damaging any coating of the sheet 200). The information listed above can be contained in the central control unit 116 and sent to the controller 30.

[0083] The feed circuit 17 may further include two manual valves 31 , 32 , which are located on the delivery line A and the return line B between the gas-oil separators 19 , 20 and the additional solenoid valves 22 , 23 .

[0084] According to the invention, the drive unit 14 may further comprise at least one measuring sensor 26 , 27 , 28 arranged on one or both of the clamping members 12 , 13 for measuring the position, velocity or mutual acceleration between the clamping members 12 , 13 or relative to the sheet 200 .

[0085] At least one measuring sensor 26 , 27 , 28 is advantageously arranged on said movable holding member 13 , 12 .

[0086] The measuring sensors 26 , 27 , 28 are advantageously arranged on the supporting elements 13 a , 12 a of the movable holding members 13 , 12 .

[0087] According to a variant, the measuring sensors 26 , 27 , 28 can be associated with or integrated in the contact elements 12 b , 13 b in some way.

[0088] At least one measuring sensor 26 , 27 , 28 may be a position measuring sensor 26 selected from the group consisting of a potentiometer, a laser sensor, an inductive LVDT (Linear Variable Differential Transformer) sensor, which is able to acquire the physical magnitude of a displacement.

[0089] According to another embodiment, at least one measuring sensor 26, 27, 28 may be a vibration measuring sensor 27, 28, for example it may be an accelerometer capable of obtaining the physical magnitude of velocity and / or acceleration, such as a piezoelectric, capacitive, laser, LVDT accelerometer.

[0090] At least one control sensor 26, 27, 28 is operatively connected to the controller 30 or the central control unit 116, to which it sends a corresponding measurement signal containing the value of the acquired physical magnitude (position, velocity, acceleration).

[0091] The controller 30 compares the obtained physical size value with the normality, pre-alarm and alarm intervals stored in its own memory module. Therefore, the controller 30 can command an automatic intervention, or can suggest to the operator an intervention to be performed, in order to correct the control parameters of the feed circuit 17. The above control parameters can be related to the degassing operation of the portion of the delivery line A or the return line B included between the gas-oil separator 19, 20 and the actuator 16 to eliminate any trapped bubbles, or to correct the input value of the thickness T of the sheet 200.

[0092] Thanks to the presence of control sensors 26, 27, 28, the controller 30 is able to implement feedback control, thereby avoiding compromises in: processing quality (vibrations during polishing will change the processing quality); the service life of the processing tools 125 (especially those tools used for polishing that are most susceptible to wear); the production efficiency of the device 100 and the integrity of its mechanical components.

[0093] The control sensors 26 , 27 , 28 are also useful in the field of predictive maintenance, since the values ​​they detect can be used not only for the control of the stabilizer device 11 , but also for predicting the occurrence of more serious failures, which can significantly save maintenance costs and improve the productivity of the device 100 .

[0094] As described above, the operation of the holding unit 10 corresponding to the method of the invention is to reciprocate the gripping members 12 , 13 relative to each other along the gripping and releasing axis Z. In particular, at least one of the gripping members 12 , 13 is driven by an actuator 16 fed by a feed circuit 17 through a first solenoid valve 18 .

[0095] Once a level corresponding to the thickness T of the sheet 200 is reached and at least one of the clamping members 12, 13 has a predetermined thrust value (this thrust is determined by the setting of the pressure regulator 24), the drive circuit 17 is switched from open to closed through the additional solenoid valves 22, 23 to keep at least a part of the drive circuit 17, including the two compartments 16a', 16a" of the actuator 16, completely filled with oil, thereby stabilizing the reciprocating position of the clamping members.

[0096] For the operation of the approach / closing step of the clamping members 12, 13, the normally closed additional solenoid valves 22, 23 are switched to the open position, and the first solenoid valve 18 with an open center is also switched to this position to conduct compressed air to the air / oil separator 19 of the delivery line A at a pressure regulated by the pressure regulator 24 to drive the actuator 16.

[0097] Therefore, the first positive pressure compartment 16a′ is filled, and the rod 16b of the actuator 16 performs a positive stroke, that is, approaches the sheet 200 along the clamping and release axis Z, pressing the contact element 13b to the front 211 of the sheet 200 with a controllable force value (determined by the setting of the pressure regulator 24).

[0098] Without damaging any coating of the sheet 200, the following force values ​​must be considered comprehensively: the deformation capacity of the peripheral volume of the elastic material of the contact elements 12b, 13b; the ability of the sheet 200 to withstand loads; and the reciprocating sliding freedom between the contact elements 12b, 13b and the sheet 200.

[0099] At the same time, the oil contained in the second compartment 16a" of the actuator 16 is returned to the air / oil separator 20 of the return line B, and the air above it is discharged into a special air discharge line through the first solenoid valve 18.

[0100] Under the conditions thus achieved, the normally closed additional solenoid valves 22, 23 (at this time in the open position) are deactivated. That is, they return to the normally closed state, so that the circuit volume between them and the compartments 16a' and 16a" of the actuator 16 is completely invaded only by oil, which is incompressible, resulting in the distance between the contact elements 12b, 13b remaining unchanged, i.e. calibrated to the level achieved in the closed state of the solenoid valves 22, 23, thus ensuring the required retention and guidance of the peripheral edge 212 of the sheet 200 throughout the path defined by the ongoing processing.

[0101] Due to the dimensional tolerances specified in the relevant specifications, the thickness T of the peripheral edge 212 of the sheet 200 varies slightly (these variations are in any case within the range of a few tenths of a millimeter), which can be absorbed by the deformability of the contact elements 12b, 13b or their coatings.

[0102] from Figure 2 It can be learned from reading the pneumatic / hydraulic schematic diagram that in the negative stroke state of the actuator 16 (ie, when the clamping members 12, 13 are moving away / opening), the states of the solenoid valves 18, 22, 23 can be immediately identified.

[0103] It is obvious that modifications and / or additions of components may be made to the method for processing a sheet material 200 described herein, without departing from the field and scope of the present invention, as defined by the appended claims.

[0104] It is also obvious that, although the invention has been described with respect to certain specific examples, a person skilled in the art will certainly be able to realize other equivalent forms of apparatus and methods for fixing and processing sheets having the features as claimed, and all of these fall within the scope of protection defined by the claims.

[0105] In the following claims, references in parentheses are provided for ease of reading only and shall not be considered as limiting factors in determining the scope of protection.

Claims

1. A holding unit (10) for holding a sheet (200), the holding unit include: - a stabilizer device (11) having clamping members (12, 13), wherein at least one of the clamping members is movable along an axis (Z) relative to the other clamping member; and - a drive unit (14) having an actuator (16) associated with the movable holding members (12, 13) and fed by a feed circuit (17), characterized in that the feed circuit (17) comprises: - a delivery line (A) and a return line (B) fluidically connected to the actuator (16), and a first solenoid valve (18) for controlling the lines (A, B), wherein the delivery line (A) is configured to supply liquid to the actuator (16); and - Additional solenoid valves (22, 23), wherein a first additional solenoid valve is located on the supply line (A) and a second additional solenoid valve is located on the return line (B) between the first solenoid valve (18) and the actuator (16).

2. The holding unit (10) according to claim 1, Features: The delivery line (A) and the return line (B) are fluidically connected to compressed air and exhaust lines on the other side relative to the connection side of the actuator (16), and the first solenoid valve (18) is a pneumatic solenoid valve for pneumatic control of the lines (A, B).

3. The holding unit (10) according to claim 1 or 2, Features: The feed circuit (17) comprises gas-oil separators (19, 20), wherein the first gas-oil separator is located on the delivery pipeline (A) between the actuator (16) and the first solenoid valve (18), and the second gas-oil separator is located on the return pipeline (B).

4. The holding unit (10) according to claim 3, Features: The feed circuit (17) comprises a pressure regulator (24) arranged in the delivery pipeline (A) between the first solenoid valve (18) and the opposite gas-oil separator (19).

5. The holding unit (10) according to claim 3, Features: The additional solenoid valves (22, 23) are oil-powered solenoid valves and are located between the corresponding gas-oil separators (19, 20) and the actuator (16).

6. The holding unit (10) according to any one of the preceding claims, Features: The holding unit (10) comprises at least one control sensor (26, 27, 28) associated with the holding members (12, 13) and configured to measure a control parameter of the movement of one or both of the holding members (12, 13).

7. The holding unit (10) according to claim 6, Features: The control sensor is a displacement sensor (26) configured to detect the distance between the clamping members (12, 13).

8. The holding unit (10) according to claim 6, Features: The control sensor is a vibration sensor (27, 28) configured to detect the vibration state of one or both of the clamping members (12, 13) in terms of velocity and / or acceleration.

9. The holding unit (10) according to claim 6, 7 or 8, Features: The control sensors (26, 27, 28) are attached to the movable clamping members (12, 13).

10. The holding unit (10) according to claim 6, Features: The holding unit (10) comprises a controller (30), which is connected to at least the first solenoid valve (18) and the additional solenoid valves (22, 23) to realize their opening / closing operations, and is connected to the pressure regulator (24) and the at least one control sensor (26, 27, 28).

11. The holding unit (10) according to claim 10, Features: The controller (30) is configured to control the pressure regulator (24) in feedback based at least on a signal feedback received from at least one of the control sensors (26, 27, 28) to process a subsequent sheet (200).

12. An apparatus (100) for processing a sheet material (200), include: - mobile devices (111, 112); It is configured to move at least one sheet (200) along a forward direction (F); - at least one machining unit (113), comprising a machining head (123) on which at least one machining tool (125) is mounted; and - A holding unit (10) according to any one of the preceding claims, in which the stabilizer device (11) is mounted on the machining head (123).

13. A method for holding a sheet material (200) having a thickness (T) by reciprocating the clamping members (12, 13) in a stabilizer device (11) along a clamping and releasing axis (Z), Features: At least one of the clamping members (12, 13) is driven by a hydraulic actuator (16), and the hydraulic actuator (16) is supplied with fluid from a corresponding supply circuit (17) through a first solenoid valve (18). When the clamping members (12, 13) reach a level corresponding to the thickness (T) of the sheet (200) and at least one of the clamping members (12, 13) has a predetermined thrust value, the drive circuit (17) is switched from open to closed through additional solenoid valves (22, 23) to keep at least a portion of the feed circuit (17), including the actuator (16), completely invaded by the liquid, thereby stabilizing the reciprocating position of the clamping members (12, 13).

14. The method according to claim 13, Features: The method provides for measuring a control parameter of a movement of one or both of the gripping members (12, 13) by means of at least one control sensor (26, 27, 28) associated with one or both of the gripping members (12, 13).

15. The method according to claim 13 or 14, Features: The method provides controlling one or both movements of the clamping members (12, 13) by means of a controller (30), the controller (30) being operably connected to at least the first solenoid valve (18) and the additional solenoid valves (22, 23) to achieve their opening / closing operation, and being operably connected to the pressure regulator (24) and at least one of the control sensors (26, 27, 28).

16. The method according to claim 15, Features: The controller (30) is configured to control the pressure regulator (24) in feedback based at least on a signal feedback received from at least one of the control sensors (26, 27, 28) to process a subsequent sheet (200).

Images