Gripping device for sheet elements, related system and method

Abstract

The invention relates to a gripping device suitable for lifting a sheet element. The device comprises a gripping mechanism (4) fixed on a support (2), said gripping mechanism (4) comprising an appendage (5) able to come into contact with and adhere to the surface of a sheet element (6). The device comprises at least two rods (7) having a free end that is movable in the longitudinal direction (L). The device also comprises a return mechanism (9) suitable for bringing the free end of each rod to a plane further from a reference surface (201) of the support (2) than the longitudinal end of the appendage (5) in the longitudinal direction (L). The invention also relates to a system comprising such a device in combination with a robot, and to a method for manufacturing a composite workpiece using such a system.

Description

Technical Field

[0001] This invention relates to the field of industrial devices for gripping and manipulating workpieces, particularly sheet elements.

[0002] This invention has particular applications in gripping and positioning thin, uniformly thick sheets (also known as “chips”) that can be used as reinforcing materials in a matrix to obtain workpieces made of composite materials.

[0003] More specifically, the present invention relates to a gripping device suitable for gripping sheet elements, particularly chips containing carbon fibers. This gripping device can be used in systems that also serve the purpose of this invention, systems that allow the sheet elements to be positioned in a placement area. Gripping the carbon fiber-containing chips and placing them in a mold to manufacture composite material workpieces thus constitutes a preferred application of the invention. Background Technology

[0004] For various industrial applications, there is a need to grasp and transport thin components, such as components in the form of sheets, cards, and wafers.

[0005] Grasping these types of components is not straightforward for a variety of reasons. Thin workpieces often cannot be gripped through their edges due to their thinness and the potential for deformation. Therefore, suction cup grippers have been developed that allow thin workpieces to be lifted by using one or more suction cups to connect with the surface of such workpieces through negative pressure.

[0006] However, when thin, flat workpieces (such as sheets) are stacked, adhesion occurs when lifting the top workpiece, which often prevents the first workpiece from separating from the stack, or lifts one or more workpieces below it.

[0007] To address this issue, solutions have been developed for certain applications.

[0008] Document FR2376052 describes a gripping and transporting system for manipulating thin, sensitive metal sheets. In this system, a suction device grips the sheet using the negative pressure it generates, then lifts the suction device, pressing the sheet against a bending device formed by a concave structure, thus bending the sheet. The sheet is then brought onto a transport frame, with its ends entering clamping jaws that unfold the sheet onto the frame.

[0009] Document JP2005263414 proposes a fairly similar device, which includes a cup formed around the suction device that causes localized deformation of the manipulated sheet.

[0010] Document CN104057439 discloses a gripping device particularly suitable for picking up and stacking plates, specifically for picking up and stacking so-called positive and negative plates during lithium battery manufacturing. To this end, the document proposes a gripper comprising at least three suction cups, wherein the central suction cup can be moved to a plane lower than the surrounding suction cups.

[0011] Document FR3102696 describes a gripping device for grasping objects, such as car windshields, using a suction cup. The suction cup has a rigid support and a flexible lip. The flexible lip forms a contact surface with the object. Furthermore, the device includes a plate fixed to the rigid support. This plate extends parallel to the contact surface and beyond the flexible lip. One or more fingers are supported by the plate. These fingers extend forward until they reach a plane aligned with the flexible lip. Therefore, they can contact the object, thus aiding in the proper orientation of the suction cup.

[0012] However, these solutions are complex and not well-suited for gripping small components. Furthermore, they struggle to grip sheet components of various sizes and shapes with different mechanical properties, particularly in terms of stiffness.

[0013] Furthermore, when grasping chips presented in sheet form, such as sheets composed of materials that can be used as composite reinforcements and typically contain fibers like carbon fibers, the aforementioned problem of lifting multiple components when raising top-stacked components is exacerbated by the porosity of these chips. Therefore, when attempting to lift chips using suction cups or any other negative pressure system, the negative pressure may be partially transferred to one or more chips located below the chip that should be grasped by the gripper, increasing the risk of grasping multiple chips simultaneously.

[0014] Furthermore, since the chips are intended to be placed in a mold containing liquid resin, contact between the suction cups (or other devices used to grip the chips) and the resin should be avoided when placing the chips into the mold. Such contact can cause gripper malfunction in the short term, whether gripping or placing the chips, for example, as the chips may adhere to the gripping device. When using suction cups, the resin can quickly degrade them, for example, making them less flexible, and / or reducing their functionality due to resin buildup. When using a suction system, there is a risk of resin being drawn into the system.

[0015] Therefore, existing systems cannot completely solve these problems, or can only solve them in an imperfect way. Summary of the Invention

[0016] The present invention aims to overcome all or part of the disadvantages of the prior art described above.

[0017] Therefore, the present invention relates to a gripping device suitable for lifting sheet elements, the gripping device comprising a support and a gripping mechanism fixed to the support, the gripping mechanism including an attachment adapted to contact and adhere to the surface of the sheet element. The gripping device includes at least two rods, each rod having a free end movable in a longitudinal direction, and a reset mechanism adapted to bring the free end of each rod to a plane further in the longitudinal direction from a reference surface of the support than the longitudinal end of the attachment of the gripping mechanism.

[0018] The reset mechanism is adjustable to adjust the force it applies. Depending on the implementation, the adjustment of the force applied by the reset mechanism can be performed outside of device use (e.g., by replacing the spring when the reset mechanism is spring-driven) or during device use (when the reset mechanism is an active reset mechanism). This allows the device to be adapted to the manipulated element, particularly its flexibility. The use of the reset mechanism in assisting in ejecting sheet elements during placement will also be described below.

[0019] Therefore, the device bends the sheet element held by the gripping mechanism's attachment by acting on a lever. For example, the lever may include an end that bends the sheet element by pressing against it. Specifically, the gripping mechanism holds the central region of the sheet element at a given distance from its support, while the lever tends to move the edge of the sheet element further away from the support. This bending ensures that the gripping device lifts only one sheet element at a time.

[0020] The rod can be a straight rod and can extend substantially parallel in the longitudinal direction. The rod is slidably mounted on both sides of the gripping mechanism relative to the support.

[0021] A compact device can be achieved using a lever driven by a reset mechanism, allowing for the gripping of small sheet elements. This gripping device is particularly significant in manipulating chips containing carbon fibers, which can be used to manufacture composite workpieces. Because the attachment of the gripping mechanism is located closer to the plane of the gripping device support than the free ends of the lever (e.g., formed by the ends), which press against the sheet element (e.g., the chip), the risk of the attachment coming into contact with the resin when the sheet element is placed in a mold containing liquid resin is limited.

[0022] A sheet element is a planar element that is not deformed by external force, with a substantially constant average thickness (e) that is small compared to other dimensions, particularly its largest dimension (d). Advantageously, the ratio (e) / (d) is between 0.05 and 0.0005, preferably between 0.01 and 0.001, and more preferably between 0.005 and 0.001. "Substantially constant" thickness means that an observer spontaneously perceives the sheet element as a planar element that does not exhibit significant thickness variation. However, because the thickness is small relative to other dimensions of the element, a sheet element exhibiting a 30% thickness variation, which represents a small change in absolute value compared to other dimensions, can be considered to have substantially constant thickness in some cases.

[0023] The gripping mechanism can be slidably mounted relative to the support, while the second reset mechanism tends to bring the attachment to a given position relative to the support and reference surface without external constraints. The second reset mechanism may include a spring. Components of the gripping device that come into contact with the sheet element are therefore equipped with reset mechanisms to provide the necessary flexibility to the device, especially when picking up the element.

[0024] The attachments to the gripping mechanism may include suction cups. According to other embodiments, the attachments to the gripping mechanism may include adhesive portions. According to other embodiments, the attachments to the gripping mechanism may include a surface suitable for being coated with resin.

[0025] Therefore, different methods of lifting sheet elements can be envisioned. Using a suction cup is a simple and known method for lifting elements. The suction cup can be a conventional suction cup or one equipped with a suction device to actively generate negative pressure in the attachment of the gripping mechanism. The advantage of the adhesion device is that its efficiency is not affected by the porosity (or more precisely, its permeability) of the material constituting the sheet element.

[0026] The gripping device can have two levers.

[0027] The two rods enable bending around a single axis, which is the most efficient solution for bending sheet elements and achieving the desired separation between the two elements.

[0028] The reset mechanism may include a spring. The reset mechanism may include an electromagnet.

[0029] The reset mechanism can therefore be active or passive. As detailed below, passive components are easy to implement, require no external connections, especially electrical or pneumatic connections, work effectively with negative pressure gripping mechanisms (such as suction cups), and can be particularly compact, while active reset mechanisms provide more adaptability to the gripping device and are necessary when the gripping mechanism is an adhesive device.

[0030] The present invention also relates to a system comprising a gripping device as defined above and a robot configured to move the gripping mechanism between a container containing one or more stacked sheet elements and a placement area for the sheet elements.

[0031] The robots used can be, in particular, two-axis, three-axis, four-axis, five-axis, or six-axis robots.

[0032] The sheet element can be a chip containing carbon fibers in a cured matrix, and the placement area is a mold for manufacturing composite workpieces. This system constitutes a preferred embodiment of the invention. The gripping device developed within the framework of the invention solves the problem of gripping only one chip containing carbon fibers from a chip stack, and the robot can place the chip very precisely in the mold to ultimately achieve reinforcement of the composite material.

[0033] Finally, this invention relates to a method for manufacturing a composite material workpiece, the method comprising: A system is provided comprising a gripping device adapted to lift sheet elements, the gripping device including a support and a gripping mechanism fixed to the support, the gripping mechanism including an attachment adapted to contact and adhere to the surface of the sheet elements, the gripping device including at least two rods, each rod having a free end movable in a longitudinal direction, the gripping device including a reset mechanism adapted to bring the free end of each rod to a plane further away from a reference surface of the support in the longitudinal direction than the longitudinal end of the attachment of the gripping mechanism, and a robot configured to move the gripping mechanism between a container containing a stack of one or more sheet elements and a placement area of ​​the sheet elements. The attachment of the gripping mechanism grips the sheet components in the container. A force is applied by a rod to bend the sheet element. Transport the gripping mechanism to the placement area, and Place the sheet element in the placement area.

[0034] When grasping the sheet element, the air permeability of the sheet element can be measured.

[0035] When a force is applied through the rod to bend the sheet element, the force applied to the rod by the sheet element and / or the longitudinal position of the free end of the rod can be determined to confirm that the gripping device holds the sheet element and / or to mechanically characterize the sheet element.

[0036] The method may include adjusting at least one operating parameter of the gripping device based on measured air permeability and determined mechanical properties.

[0037] The adjustment of at least one operating parameter of the gripping device can be conditional upon the detection of a given event, such as the gripping device accidentally releasing a sheet element.

[0038] In this method, the placement of the sheet element can be achieved by disabling the gripping mechanism and / or increasing the distance between the attachment of the gripping mechanism and the plane containing the free end of the rod.

[0039] This method is implemented using the system described above, thus enabling precise positioning of the sheet element.

[0040] After the sheet element is placed, its position in the placement area can be corrected by using a rod to push the sheet element laterally.

[0041] The configuration of the gripping device proposed within the framework of this invention enables this function. Attached Figure Description

[0042] Other advantages, objects, and specific features of the invention will become apparent from the following non-limiting description of at least one specific embodiment of the apparatus and method of the invention, with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of a gripping device according to one embodiment of the present invention; Figure 2 yes Figure 1 Another schematic diagram of the gripping device; Figure 3 yes Figure 1 and Figure 2 A three-dimensional view of a variant of the device; Figure 4 yes Figure 1 and Figure 2 A detailed view of the gripping mechanism included in the gripping device. Figure 5 This is a schematic diagram of a gripping device in a first position according to another embodiment of the present invention; Figure 6 and Figure 7 Showing Figure 5 The device is located in two other positions. Detailed Implementation

[0043] This description is given as a non-limiting example.

[0044] Figure 1 and Figure 2 This refers to a gripping device conforming to one embodiment of the present invention, which will be described below.

[0045] Figure 1 This is the so-called front view of the gripping device. Figure 2 This is the so-called side view of the gripping device, which is at 90° to the front view. The same reference numerals are applied to... Figure 3 .

[0046] The gripping device 1 includes a support member 2. The support member 2 is adapted to be fixed to the robot, for example, via a flange 3.

[0047] The gripping mechanism 4 is fixed to the support 2. The gripping mechanism 4 is a mechanism adapted to grip and hold the sheet element. For this purpose, it includes an attachment 5 that can be temporarily attached to the surface of the sheet element. In the example shown here, the attachment 5 is a suction cup 501. The suction cup 501 has an internal volume that can generate negative pressure by pressing the suction cup 501 against the surface of the element to be gripped, and / or by applying negative pressure (not shown) through a vacuum source connected to the suction cup. Therefore, a conduit (not shown) for the vacuum circuit is connected to the suction cup 501, for example, via the support 2 along the axis of the support and the suction cup.

[0048] Attachment 5 is slidably mounted relative to support 2 along at least one axis. For example, attachment 5 can be slidably mounted relative to the main axis of support 2 in the longitudinal direction L and mounted on a spring. In particular, attachment 5 is fixedly mounted here relative to slider 502, which is mounted on the longitudinal axis 201 of support 2 in a longitudinal slide rail manner.

[0049] Thin-film element 6, such as Figure 4 As shown, it can be a sheet or chip formed from a composite material containing reinforcing fibers.

[0050] The sheet element may in particular be a chip with a substantially constant thickness defined between two opposing parallel planes of the chip, comprising carbon fibers at least partially embedded in a cured matrix. At least a majority of the fibers of the chip may extend substantially parallel to the opposing planes of the chip.

[0051] The thickness of the chips can be, for example, between 200 μm and 1 mm, for chips with a maximum size of several centimeters. For example, the maximum chip size can be less than or equal to 120 mm, such as about 60 mm.

[0052] The gripping device also includes two rods 7. The two rods 7 are straight and slidably mounted relative to the support 2, parallel to the main axis of the attachment and in the longitudinal direction L. Specifically, each rod 7 is mounted within a tube 8 to allow for small functional clearances in which the rod 7 can translate within the tube 8. If the rod 7 has a circular cross-section and a given diameter, the tube 8 will have a slightly larger inner diameter, thus allowing the rod 7 to translate within the tube 8.

[0053] Each rod 7 includes a first end 701 and a second end 702. The first end 701 is fixed (e.g., glued or screwed) to form a first end of the rod 7, and the second end 702 is fixed (e.g., glued or screwed) to form a second end of the rod 7.

[0054] The dimensions of the first end 701 and the second end 702 are too large to pass through the tube 8, thus preventing the rod 7 from coming out of the tube 8.

[0055] Clearly, any other slide rail configuration that allows for longitudinal translation of rod 7 can be successfully used in other embodiments of the invention.

[0056] Similarly, as an alternative, the rod itself can function as a spring to deform in the longitudinal direction, in which case the rod itself also forms a reset mechanism.

[0057] The reset mechanism 9, formed here by spring 901, is inserted between the first end 701 and the end 801 of tube 8. Spring 901 tends to bring the second end 702 into contact with the second end 802 of tube 8, and the free end of the rod formed by the first end 701 is brought into the plane P1 away from the support 2 in the longitudinal direction L.

[0058] In particular, when no external force is applied to the rod 7, the plane P1 is located at a distance D1 from the reference transverse surface 201 of the support 2, which is measured in the longitudinal direction L.

[0059] The second reset mechanism 10, such as Figure 3 As shown, for example, a spring installed between the fixing element of the support and the slider 502 tends to cause the attachment, particularly its longitudinal end, to move away from the reference surface 201 of the support 2. More specifically, in the absence of an external force applied to the attachment 5, its end is located at a longitudinally measured distance D2 relative to the reference surface 201, which is less than D1.

[0060] Figure 4 The image shows the portion of the gripping mechanism 4 that interfaces with the sheet element 6 when the sheet element 6 is gripped from the sheet element stack (6, 61, 62) by the attachment 5 of the gripping mechanism. The sheet element can be, for example, a chip as described above.

[0061] and Figures 1 to 3 Similarly, Appendix 5 of the grasping mechanism is suction cup 501.

[0062] In order to grasp the sheet element 6, attachment 5 is brought into contact with its surface 601, which is called the upper surface. The movement of the grasping device can be ensured by a robot attached to it, such as a 6-axis robot (or others).

[0063] When the two rods 7 are pushed upward, the reset mechanism 9, i.e., the spring 901, is compressed, and the first end of the rod formed by the first end 701 is aligned with the longitudinal end of the accessory 5 (e.g., the contact plane of the suction cup 501) in the same plane.

[0064] A negative pressure is generated in the suction cup 501, which picks up the sheet workpiece and attaches it to the suction cup 501.

[0065] The gripping device is then lifted by the robot it is connected to.

[0066] Spring 901 tends to extend, and rod 7, particularly its first end 701, applies force by pressing against the sheet element 6 on both sides of suction cup 501. Due to its thin thickness, sheet element 6 bends and flexes. This creates space between sheet element 6 and the next element 601, ensuring that the gripping device lifts only one sheet element at a time.

[0067] Advantageously, the reset mechanism is adjustable. It is specifically configured to adjust the force it applies to the sheet element through end 701. Thus, the reset mechanism 9 is adjustable to adjust the force required to longitudinally move end 701 of the rod when the end is in plane P1, i.e., when no external force is applied to the rod.

[0068] This particularly allows the device to be adapted to different types of sheet elements, which may have different mechanical properties. Ultimately, this makes it possible to achieve the desired bending of the sheet elements.

[0069] When the reset mechanism is active, especially when it includes an actuator, this regulation typically involves appropriate control of the reset mechanism, such as controlling the applied voltage to the electromagnets included in the reset mechanism, or controlling the pressure in a pneumatic or hydraulic reset mechanism.

[0070] Whether the reset mechanism 9 is active or passive, mechanical adjustment can be provided to adjust the force applied by the reset mechanism.

[0071] In the example shown here including spring 901, which is merely an example, various solutions can be applied to adjust the force applied by the reset mechanism. When end 701 is removable (e.g., when it is screwed), end 701 can be removed to replace it with a spring with different characteristics, or a spring preload ring can be added. The thickness of the preload ring can adjust the force applied by the spring. Alternatively, the reset mechanism 9 can include any other mechanical means to adjust the preload of spring 901, such as a longitudinally adjustable spring 901 stop on a thread formed on rod 7.

[0072] As an example only, for gripping small components, the suction cup (or other attachments, as described below) can have a small diameter, such as between 10 mm and 20 mm, like 16 mm. The rods 7 can extend close to the suction cup, and the center distance between them can be, for example, between 14 mm and 25 mm, depending on the size of the gripping mechanism attachment.

[0073] Depending on the sheet element to be grasped and manipulated, the spring 901 can be replaced to accommodate the sheet element. For example, when using chips containing carbon fiber, chips of different shapes, thicknesses, and compositions can be used. The height and stiffness of the spring can be adjusted to achieve the desired bending effect with the chips (or other sheet elements) used.

[0074] After the sheet element is grasped, the robot carries the gripper to the placement area, where the sheet element must be placed in a precise position and orientation. The placement area is typically a mold used to manufacture composite workpieces, in which the sheet element participates in forming the reinforcing material.

[0075] The sheet element is placed in its intended position. In particular, the center of attachment 5 of the gripping mechanism is aligned with the center of the predetermined placement position.

[0076] Deactivating the suction cup, i.e., releasing the negative pressure in the suction cup, allows the sheet element to be released. Rod 7, under the action of spring 901, pushes the sheet element longitudinally, helping to press it into the appropriate position.

[0077] When the sheet element 6 is a chip that must be placed in a mold containing liquid resin, this allows the chip to be released while the suction cup 501 is above the resin but not in contact with it. Contact with the resin could damage the suction cup or even cause the resin to be drawn into the device (especially in a vacuum circuit). The rod 7 ensures that the chip is held in place by pressing it against it. If necessary, the first end 701 may be allowed to contact the liquid resin when placing the chip.

[0078] Furthermore, in some embodiments, the contact between the lever 7 and the chip (or other sheet element) can be used to correct its position after the gripper releases the chip. For this purpose, the robot moves the gripper to move the lever 7 pressing against the chip, which allows it to slide to the desired orientation and / or correct its orientation. If necessary, this correction can be performed while the chip is immersed in resin.

[0079] Figure 5 This describes two aspects that can be implemented in embodiments of the present invention.

[0080] According to the first aspect, the reset mechanism 9 includes an electromagnet 11. The electromagnet 11 can be used to control the longitudinal position of the lever 7, particularly the position of the first end 701, and / or the force they apply to the sheet element 6.

[0081] according to Figures 5 to 7 In the second aspect shown, the gripping mechanism 4 here includes an adhesive attachment 12 as an accessory. Using a self-adhesive device such as adhesive attachment 12 avoids problems that may arise when breathable materials are gripped by the suction cup. An adhesive attachment refers to any planar self-adhesive device, regardless of its shape.

[0082] However, one of the difficulties that may arise when using adhesive attachments is that they must be frequently replaced or cleaned to maintain their full adhesive properties. This problem can be solved by ensuring the automatic replacement of adhesive attachment 12.

[0083] For example, adhesive attachments can be applied to components that can be grasped using a gripping device, such as a suction cup (or clamp). This makes replacement easy, and robots equipped with gripping devices can ensure automatic replacement.

[0084] Preferably, the adhesive attachment may be formed from a portion of an adhesive tape roll installed in the dispenser, and the gripping device is adapted to automatically pick up and operate the dispenser.

[0085] Similar to the case of "passive" suction cups (i.e., not supplied by a vacuum source in a controllable manner), it should be noted that when using an adhesion device for gripping, it is impossible to command the release of the grip on the sheet element. Therefore, it is necessary to use a controllable reset mechanism 9, such as an electromagnet actuator as shown here, to cause the element to pop out relative to the gripping device when the sheet element is placed.

[0086] Reference Figures 5 to 7 Explain the use of this controllable reset mechanism.

[0087] In these embodiments, the reset mechanism 9 includes an electromagnet 11 in a linear actuator. A lever 7 is connected to an actuator that can adjust the longitudinal position of the lever 7. The reset mechanism also includes an actuator spring 902 that tends to bring the lever to a rest position, where, when the electromagnet is not activated, the first end 701 of the lever 7 is located in a transverse plane closer to the gripping device support 2 than the adhesive attachment 12. In other words, in Figure 5 In the position shown, the electromagnet is not activated, and when the adhesive comes into contact with the sheet element to be grasped, a gap j is maintained between the first end 701 and the sheet element 6, or at least the first end 701 does not press on the sheet element 6.

[0088] Figure 6 This illustrates the position of the sheet element when lifted by the gripping device. Electromagnet 11 is activated by a small current flowing through its coil. It applies a force to rod 7 sufficient to overcome the force applied by actuator spring 902, thereby applying a moderate force to sheet element 6—small enough to prevent it from detaching from the adhesive, but sufficient to keep it as described above. Figure 4 It is slightly curved as explained.

[0089] Once the system's robot brings the gripper to the placement area, the current in the electromagnet 11 coil increases to release the sheet element. This causes the force exerted by the rod 7 on the sheet element to increase until it causes it to detach from the adhesive attachment 12, as... Figure 7 As shown.

[0090] Obviously, the same operation can be used with a "passive" suction cup. Similarly, in an alternative embodiment, the adhesion device can be implemented by covering the surface of the gripping attachment with resin. In particular, when seeking to place chips in a mold for manufacturing composite workpieces containing liquid resin, this surface can be brought into contact with the resin (or a container containing the same resin) present in the mold before gripping the chips. The resin acts as an adhesive due to the shear force induced in the resin by the weight of the chips (or other components). In this case, the resin can be reloaded each time chips are placed in the mold. Furthermore, according to one embodiment, the resin can be directly extruded into the mold through the attachment of the gripping mechanism or at its location.

[0091] Furthermore, it is clear that the aforementioned electromagnet actuator can be replaced by other suitable types of actuators.

[0092] Furthermore, the air permeability of the sheet element can be measured during gripping. This measurement can be used to characterize the materials constituting the sheet element and adjust parameters that allow it to grip (e.g., adjusting the vacuum level if gripping by negative pressure). The measurement can also provide information about the flow of resin within the sheet element when the material is known.

[0093] When the sheet element is held by the device, the force exerted by the sheet element on the rod 7 and / or the longitudinal position of the end of the rod 7 can be used to confirm that the gripping device is indeed holding the sheet element (e.g., chips), and / or can be used to mechanically characterize the sheet element (in particular its flexural modulus).

[0094] The information collected by the gripping device can be used to feed dynamic algorithms and adjust the operating parameters of the gripping device.

[0095] For example, if a sheet element, such as a chip, falls from the gripping device—that is, it is released prematurely, resulting in inaccurate placement—the operating parameters of the gripping device in subsequent gripping and placement of the next sheet element can be adjusted by knowing its air permeability and flexural modulus. For example, according to the considered embodiment, when the gripping mechanism includes a suction device, the vacuum level of the gripping mechanism can be adjusted, and / or the force applied to the chip by the rod can be adjusted.

[0096] Other events (failure to grasp the sheet element, excessive or insufficient bending of the sheet element, etc.) can be used as conditions for adjusting the operating parameters.

[0097] This learning ability of the device ensures proper and precise placement of the chips.

[0098] Therefore, within the framework of this invention, a gripping device suitable for grasping sheet components is proposed. This device is applicable to small-sized components, such as those with a maximum size of a few centimeters, ensuring that only one component is grasped from a stack of such components. Furthermore, when the gripping device is used to place chips in a mold for manufacturing composite workpieces containing resin, the device allows for the avoidance of contact between the gripping mechanism's attachments (e.g., suction cups) and the resin. The proposed device is simple and compact.

Claims

1. A gripping device suitable for lifting a sheet element (6), the gripping device comprising a support member and a gripping mechanism (4) fixed to the support member (2), the gripping mechanism (4) comprising an attachment (5) adapted to contact and adhere to the surface of the sheet element (6), The gripping device includes at least two rods (7), each rod having a free end movable in the longitudinal direction (L), and the gripping device includes a reset mechanism (9) adapted to bring the free end of each rod to a plane in the longitudinal direction (L) further away from the reference surface (201) of the support member (2) than the longitudinal end of the attachment (5) of the gripping mechanism (4). Its features are, The reset mechanism (9) is adjustable so as to adjust the force it applies.

2. The device according to claim 1, wherein the rod (7) is straight and extends substantially parallel in the longitudinal direction (L), and the rod (7) is slidably mounted on both sides of the gripping mechanism (4) relative to the support (2).

3. The gripping device according to claim 1 or 2, wherein the gripping mechanism (4) is longitudinally slidably mounted relative to the support (2), and the second reset mechanism (10) tends to bring the attachment (5) to a given longitudinal position relative to the support (2) and the reference surface (201) without external constraints.

4. The gripping device according to any one of claims 1 to 3, wherein the attachment (5) of the gripping mechanism (4) includes a suction cup (501).

5. The gripping device according to any one of claims 1 to 3, wherein the attachment (5) of the gripping mechanism (4) includes an adhesive attachment (12).

6. The gripping device according to any one of claims 1 to 3, wherein the attachment (5) of the gripping mechanism (4) includes a surface adapted to be covered with resin.

7. The gripping device according to any one of the preceding claims, wherein the rod (7) is two rods.

8. The gripping device according to any one of the preceding claims, wherein the reset mechanism (9) comprises a spring (901).

9. The gripping device according to any one of the preceding claims, wherein the reset mechanism (9) comprises an electromagnet (11).

10. A system comprising a gripping device according to any one of the preceding claims and a robot configured to move the gripping mechanism (4) between a container containing one or more stacked sheet elements and a placement area of ​​the sheet elements (6).

11. The system of claim 10, wherein the sheet element (6) is a chip containing carbon fiber in a cured matrix, and the placement area is a mold for manufacturing composite workpieces.

12. A method for manufacturing a composite material workpiece, the method comprising: - A system is provided comprising a gripping device adapted to lift a sheet element (6), the gripping device comprising a support and a gripping mechanism (4) fixed to the support (2), the gripping mechanism (4) comprising an attachment (5) adapted to contact and adhere to the surface of the sheet element (6), the gripping device comprising at least two rods (7), each rod having a free end movable in a longitudinal direction (L), the gripping device comprising a reset mechanism (9) adapted to bring the free end of each rod to a plane in the longitudinal direction (L) further away from a reference surface (201) of the support (2) than the longitudinal end of the attachment (5) of the gripping mechanism (4), and configured to move the gripping mechanism (4) between a container containing a robot stacking one or more sheet elements and a placement area of ​​the sheet element (6). - A sheet element (6) is grasped in the container by the attachment (5) of the grasping mechanism (4). - A force is applied by the rod (7) to bend the sheet element (6). - Transport the gripping mechanism (4) to the placement area, and - Place the sheet element (6) in the placement area.

13. The method of claim 12, wherein: - When grasping the sheet element, the air permeability of the sheet element is measured, and - When a force is applied through the rod (7) to bend the sheet element, the force applied by the sheet element to the rod (7) and / or the longitudinal position of the free end of the rod (7) are determined to confirm that the gripping device holds the sheet element and to determine the mechanical properties of the sheet element.

14. The method of claim 13, wherein the method comprises adjusting at least one operating parameter of the gripping device based on measured air permeability and determined mechanical properties.

15. The method of claim 14, wherein the adjustment of at least one operating parameter of the gripping device is conditional upon detecting a given event, such as the gripping device accidentally releasing a sheet element.

16. The method according to any one of claims 12 to 15, wherein the placement of the sheet element (6) is achieved by disabling the gripping mechanism (4) and / or increasing the distance between the attachment (5) of the gripping mechanism (4) and the plane containing the free end of the rod (7).

17. The method of claim 16, wherein after the sheet element (6) is placed, its position in the placement area is corrected by laterally pushing the sheet element (6) with the rod (7).

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