Gripping device for a thin element, and associated system and method

Abstract

The invention relates to a gripping device suitable for lifting a thin element. It comprises a gripping means (4) attached to a support (2), wherein the gripping means (4) comprises an accessory (5) that can be brought into contact with the thin element (6) and can adhere to a surface of the thin element. It comprises at least two rods (7) having a free end that is movable in a longitudinal direction (L). It also comprises a return means (9) designed to move a free end of each rod into a plane farther from a reference surface (201) of the support (2) in the longitudinal direction (L) than a longitudinal end of the accessory (5). The invention also relates to a system comprising such a device associated with a robot, and to a method for manufacturing a composite material part using such a system.

Description

[0001] Gripping device for thin element, associated system and method

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] The field of the invention is that of industrial devices for gripping and handling parts, in particular thin elements.

[0004]

[0002] It finds a particular application in the gripping and positioning of plates (also referred to as "chips") of low and regular thickness which can be used as reinforcement, in a matrix, to obtain a part in composite material.

[0005]

[0003] More specifically, the invention relates to a gripping device suitable for gripping thin elements and in particular chips containing carbon fibers. The gripping device can be used in a system, also the subject of the present invention, which also makes it possible to position the thin elements in a deposition zone. Gripping chips containing carbon fibers and depositing them in a mold for producing a part made of composite material thus constitutes a preferred application of the present invention.

[0006] STATE OF THE ART

[0007]

[0004] For various industrial applications, it is necessary to take and transport thin elements, in the form of sheets, cards, wafers, etc.

[0008]

[0005] Gripping this type of element is not easy, for many reasons. Thin parts cannot generally be gripped by their edges, due to their thinness and, where appropriate, the deformations of the part that this could cause. This is why suction cup grippers have been developed to lift a thin part using one or more suction cups, linked by vacuum to the surface of such a part.

[0009]

[0006] Nevertheless, adhesion phenomena are created between thin and flat pieces, such as sheets, when they are stacked, when the upper piece is lifted, which tend to oppose the separation of the first piece from the stack or to lift one or more pieces located below it when this first piece is lifted.

[0010]

[0007] To overcome this problem, solutions have been developed for certain applications.

[0011]

[0008] Document FR2376052 describes a gripping and transport system for handling thin and sensitive metal sheets. In the system described in this document, a suction means makes it possible to grip a sheet thanks to the depression it creates, then this vacuum is lifted which then applies the sheet to a bending device formed by a concave structure which bends the sheet. The sheet is then brought onto a transport frame, so that its ends arrive in clamps which have the role of extending the sheet on the frame.

[0012]

[0009] Document JP2005263414 presents a fairly similar device, comprising a cup formed around a suction means, the cup causing local deformation of the sheet which is handled.

[0013]

[0010] Document CN104057439 discloses a gripping apparatus particularly suitable for gripping and stacking plates, in this case so-called positive plates and so-called negative plates during the manufacture of a lithium battery. For this purpose, this document proposes a gripper comprising at least three suction cups, the central suction cup of which can be moved to a lower plane than that of the suction cups surrounding it.

[0014]

[0011] Document FR3102696 describes a device for gripping objects, such as automobile windshields, which uses a suction cup. This suction cup has a rigid support and a flexible lip. The flexible lip forms a contact surface with the object. In addition, the device includes a plate fixed to the rigid support. The plate extends parallel to the contact face and extends 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. They can thus touch the object and help to orient the suction cup correctly.

[0015]

[0012] These solutions are nevertheless complex and poorly suited to gripping small elements. Furthermore, they would be complex to adapt to gripping thin elements of various sizes and shapes, having varied mechanical properties, particularly with regard to their rigidity.

[0016]

[0013] Furthermore, for gripping chips that are in the form of thin plates, for example made of a material that can serve as reinforcement in a composite material and which therefore typically comprises fibers such as carbon fibers, the above-mentioned problem of lifting several elements when lifting the element located at the top of a stack is increased by the fact that these chips generally have a certain porosity. Thus, when trying to lift a chip using a suction cup or any other vacuum system, the vacuum may be partly transmitted to one or more chips located below the chip that must be gripped by the gripper, which leads to an increased risk of gripping several chips at once.

[0017]

[0014] Furthermore, since the chips are intended to be placed in a mold containing a liquid resin, it is advisable to prevent the suction cup(s) (or other means used to grip the chip) from coming into contact with the resin when the chip is deposited in the mold. Such contact could lead to a short-term malfunction of the gripper, whether during the gripping of the chip or its deposit, the chip being able, for example, to remain stuck to the gripper. When a suction cup is used, the resin could quickly damage it, for example making it less flexible, and / or degrade its operation by accumulation of resin. When a suction system is used, there is a risk of resin being sucked into the system.

[0018]

[0015] The systems known in the prior art therefore do not respond, or only imperfectly, to these problems.

[0019] STATEMENT OF THE INVENTION

[0020]

[0016] The present invention aims to remedy all or part of the drawbacks of the state of the art cited above.

[0021]

[0017] To this end, the invention relates to a gripping device adapted to lift a thin element, the gripping device comprising a support and a gripping means fixed to the support, the gripping means comprising an accessory adapted to be brought into contact with the thin element and to adhere to a surface of said thin element. The gripping device comprises at least two rods, each rod having a free end movable in a longitudinal direction, the gripping device comprising a return means, the return means being adapted to bring the free end of each rod into a plane further from the reference surface of the support, in the longitudinal direction, than a longitudinal end of the accessory of the gripping means.

[0022]

[0018] The return means is adjustable so as to adapt the force that it applies. According to various embodiments, the adjustment of the force applied by the return means can be carried out outside the use of the device (for example by a change of spring, when the return means is thus constituted) or during the use of the device (when the return means is active). This makes it possible in particular to adapt the device to the elements handled, in particular to their flexibility. The use that can be made of the return means to assist in the ejection of the thin element during its deposition is also described below.

[0023]

[0019] The device thus makes it possible, by the action of the rods on a thin element held by the accessory of the gripping means, to bend this thin element. The rods may for example comprise end pieces, which, by pressing on the thin element, bend it. In particular, the gripping means maintains a central zone of the thin element at a given distance from the support of the gripping means while the rods tend to move the edges of the thin element further away from the support. This curvature ensures that only one thin element at a time is lifted by the gripping device.

[0020] The rods may be straight and may extend substantially parallel in the longitudinal direction, the rods being slidably mounted relative to the support on either side of the gripping means.

[0024]

[0021] The use of rods pushed by a return means makes it possible to obtain a compact device, making it possible to grip small elements of low thickness. The gripping device is of particular interest in the handling of chips comprising carbon fibers which can be used in the manufacture of a part made of composite material. Insofar as the accessory of the gripping means is located in a plane closer to the support of the gripping device than the free ends of the rods, for example formed by end pieces, which press on the element of low thickness (for example the chip), when the element of low thickness is deposited in a mold containing a liquid resin, the risk of the accessory being in contact with the resin during the deposition of the element of low thickness is limited.

[0025]

[0022] By thin element is meant an element, flat in the absence of external force tending to deform it, whose average thickness (e) which is substantially constant is small compared to its other dimensions, and in particular to its largest dimension (d). Advantageously, the ratio (e) / (d) is between 0.05 and 0.0005, preferably between 0.01 and 0.001 and even more preferably between 0.005 and 0.001. By “substantially constant” thickness, it is understood that an observer spontaneously perceives the thin element as a flat element not exhibiting a significant variation in thickness. Nevertheless, since the thickness is small compared to the other dimensions of the element, a thin element exhibiting a variation in thickness of 30%, which represents a small variation in absolute value compared to the other dimensions, may where appropriate be considered as having a substantially constant thickness.

[0026]

[0023] The gripping means may be mounted so as to slide relative to the support, and a second return means then tends to bring, in the absence of external constraint, the accessory into a given position relative to the support and the reference surface. The second return means may comprise a spring. The parts of the gripping device in contact with the thin element are thus all mounted with return means which provide the device with the necessary flexibility, in particular when gripping an element.

[0027]

[0024] The accessory of the gripping means may comprise a suction cup. According to other embodiments, the accessory of the gripping means may comprise an adhesive part. According to still other embodiments, the accessory of the gripping means may comprise a surface adapted to be covered with a resin.

[0025] Different means for lifting a thin element may thus be envisaged. The use of a suction cup is a simple and known means of lifting an element. The suction cup may be a conventional suction cup or be provided with a suction means, to actively generate a depression in the accessory of the gripping means. An adhesive means has the advantage of not being impacted in its effectiveness by the porosity (or more precisely its permeability to air) of the material constituting the thin element.

[0028]

[0026] The rods of the gripping device may be two in number.

[0029]

[0027] Two rods allow a curvature to be obtained around a single axis, which is the most effective solution for curving the thin element and obtaining the desired separation effect between two elements.

[0030]

[0028] The return means may comprise a spring. The return means may comprise an electromagnet.

[0031]

[0029] The return means can thus be active or passive. As will be detailed below, passive elements are simple to implement, do not require an external connection, in particular an electrical or pneumatic connection, they are effective with a vacuum gripping means, for example a suction cup, and can be particularly compact, while an active return means offers more adaptability to the gripping device and is necessary when the gripping means is an adhesive means.

[0032]

[0030] The invention also relates to a system comprising a gripping device as defined above, and a robot configured to move the gripping means between a container which contains one or more stacks of thin elements and a deposit zone for the thin element.

[0033]

[0031] The robot used can have two, three, four, five, or six axes in particular.

[0034]

[0032] The thin element may be a chip comprising carbon fibers in a hardened matrix and the deposition zone is a mold for manufacturing a part made of composite material. Such a system constitutes a preferred embodiment of the invention. The gripping device developed within the framework of the present invention makes it possible to solve the problem of gripping a single chip containing carbon fibers on a stack of chips, and the robot makes it possible to deposit the chip very precisely in a mold to ultimately produce the reinforcements of a composite material.

[0035]

[0033] The invention finally relates to a method for manufacturing a part made of composite material, the method comprising: providing a system comprising a gripping device adapted to lift a thin element, the gripping device comprising a support and a gripping means fixed to the support, the gripping means comprising an accessory adapted to be brought into contact with the thin element and to adhere to a surface of said thin element, the gripping device comprising at least two rods, each rod having a free end movable in a longitudinal direction, the gripping device comprising a return means, the return means being adapted to bring the free end of each rod into a plane further from a reference surface of the support, in the longitudinal direction, than a longitudinal end of the accessory of the gripping means,and a robot configured to move the gripping means between a container that contains one or more stacks of thin elements and a deposit area for the thin element, gripping a thin element in the container by the accessory of the gripping means, applying by the rods a force causing a curvature of the thin element, transporting the gripping means to the deposit area, and depositing the thin element in the deposit area.,

[0036]

[0034] When taking the thin element, the permeability of said thin element can be measured.

[0037]

[0035] When applying a force by the rods causing a curvature of the thin element, it is possible to determine the forces applied by the thin element on the rods and / or the longitudinal position of the free ends of said rods in order to confirm the presence of a thin element held by the gripping device, and / or in order to mechanically characterize the thin element.

[0038]

[0036] The method may comprise an adaptation of at least one operating parameter of the gripping device as a function of the measured permeability and the determined mechanical characteristics.

[0039]

[0037] This adaptation of at least one operating parameter of the gripping device may be conditioned by detection of a given event, for example an unexpected release of a thin element by the gripping device.

[0040]

[0038] In this method, the deposition of the thin element can be carried out by deactivating the gripping means and / or by increasing the distance between the accessory of the gripping means and the plane in which the free ends of the rods are located.

[0041]

[0039] The use of a system as described above to carry out such a method thus makes it possible to precisely position thin elements.

[0042]

[0040] After the thin element has been deposited, its position in the deposition zone can be corrected by pushing the thin element laterally using the rods.

[0043]

[0041] The configuration of the gripping device proposed within the framework of the present invention allows this function. BRIEF DESCRIPTION OF THE FIGURES

[0044]

[0042] Other advantages, aims and particular characteristics of the present invention will emerge from the following non-limiting description of at least one particular embodiment of the devices and methods which are the subject of the present invention, with reference to the appended drawings, in which: Figure 1 is a schematic view of a gripping device according to one embodiment of the invention; Figure 2 is another schematic view of the gripping device of Figure 1; Figure 3 is a three-dimensional view of a variant of the device of Figure 1 and Figure 2; Figure 4 is a detailed view of a gripping means included in the gripping device of Figures 1 and 2, Figure 5 is a principle view of a gripping device according to another embodiment of the invention, in a first position; Figure 6 and Figure 7 show the device of Figure 5 in two other positions.

[0045] DETAILED DESCRIPTION OF THE INVENTION

[0046]

[0043] The present description is given as a non-limiting example of embodiment.

[0047]

[0044] Figure 1 and Figure 2 show a gripping device according to one embodiment of the invention and are described together below.

[0048]

[0045] Figure 1 is a so-called front view of the gripping device, and Figure 2 is a so-called profile view of the gripping device, at 90° to the front view. The same references are applied to Figure 3.

[0049]

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

[0050]

[0047] A gripping means 4 is fixed to the support 2. The gripping means 4 is a means adapted to grip and hold a thin element. For this purpose, it comprises an accessory 5 capable of temporarily bonding to a surface of the thin element. In the example shown here, the accessory 5 is a suction cup 501. The suction cup 501 has an internal volume which can be put under vacuum by crushing the suction cup 501 on the surface of the element to be gripped, and / or by applying a vacuum using a vacuum source connected to the suction cup (not shown in the figures). Thus, a pipe of a vacuum circuit (not shown in the figures) is connected to the suction cup 501, for example by arriving through the support 2 in the axis of the support and the suction cup.

[0051]

[0048] The accessory 5 is mounted to slide along at least one axis on the support 2. For example, the accessory 5 can be mounted to slide relative to the support 2, along a main axis of longitudinal direction L, and be mounted on a spring. In particular, the accessory 5 is here mounted fixed relative to a carriage 502, which is mounted in a longitudinal slide on a longitudinal shaft 201 of the support 2.

[0052]

[0049] The thin element 6, visible in FIG. 4, may in particular be a plate or chip formed from a composite material comprising reinforcing fibers.

[0053]

[0050] The thin element may in particular be a chip having a substantially constant thickness defined between two parallel opposite faces of the chip, comprising carbon fibers at least partly included in a hardened matrix. At least a majority of said fibers of the chip may extend substantially parallel to the opposite faces of the chip.

[0054]

[0051] The thickness of the chips may for example be between 200 μm and 1 mm, for chips whose largest dimension is a few centimeters. For example, the largest dimension of the chips may be less than or equal to 120 mm, for example of the order of 60 mm.

[0055]

[0052] The gripping device further comprises two rods 7. The two rods 7 are straight and are mounted to slide relative to the support 2, parallel to the main axis of the accessory and to the longitudinal direction L. In particular, each rod 7 is mounted in a tube 8 with a small functional clearance allowing the translation of the rod 7 in the tube 8. If the rod 7 is of circular section and has a given diameter, the tube 8 will have a very slightly larger internal diameter so as to allow the translation of the rod 7 in the tube 8.

[0056]

[0053] Each rod 7 comprises a first end piece 701 and a second end piece 702. The first end piece 701 is fixed (for example glued or screwed) to form a first end of the rod 7 and the second end piece 702 is fixed (for example glued or screwed) to form a second end of the rod 7.

[0057]

[0054] The first end piece 701 and the second end piece 702 are too large to pass into the tube 8 and thus prevent the rod 7 from exiting said tube 8.

[0058]

[0055] Obviously, any other slide configuration allowing longitudinal translation of the rods 7 can be successfully used in other embodiments of the invention.

[0059]

[0056] Similarly, alternatively, the rods can themselves form a spring so as to deform longitudinally. The rods then also form the return means.

[0057] A return means 9, here formed by a spring 901, is interposed between the first end piece 701 and one end 801 of the tube 8. The spring 901 tends to bring the second end piece 702 into contact with a second end 802 of the tube 8, and the free end of the rod formed by the first end piece 701 is brought into a plane P1 remote from the support 2, in the longitudinal direction L.

[0058] In particular, the plane P1 is located, in the absence of external force applied to the rod 7, at a distance D1, measured in the longitudinal direction L, from a reference transverse surface 201 of the support 2.

[0060]

[0059] A second return means 10, visible in FIG. 3, for example a spring mounted between a fixed element of the support and the carriage 502, tends to bring the accessory, in particular its longitudinal end, at a distance from the reference surface 201 of the support 2. More particularly, in the absence of external force applied to the accessory 5, its end is located relative to the reference surface 201, at a distance D2, measured longitudinally, less than D1.

[0061]

[0060] Figure 4 shows the part of the gripping means 4 interfacing with a thin element 6 when the latter is gripped by the accessory 5 of the gripping means on a stack of thin elements (6, 61, 62). The thin elements may be, for example, chips as described above.

[0062]

[0061] Just as in figures 1 to 3, the accessory 5 of the gripping means is a suction cup 501.

[0063]

[0062] To take the thin element 6, the accessory 5 is brought into contact with its surface 601 which is designated the upper surface. The movement of the gripping device can be ensured by a robot to which it is linked, for example a 6-axis robot (or other).

[0064]

[0063] The two rods 7 are pushed upwards, the return means 9, namely the springs 901, are compressed and the first ends of the rods, formed by the first end pieces 701, align in the same plane as the longitudinal end of the accessory 5 (for example the contact plane of the suction cup 501).

[0065]

[0064] A depression is generated in the suction cup 501, which sucks in the thin part and binds it to the suction cup 501.

[0066]

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

[0067]

[0066] The springs 901 tend to relax and the rods 7, in particular their first end pieces 701, apply a force by pressing on the thin element 6 on either side of the suction cup 501. Due to its thinness, the thin element 6 bends, curves. This creates a space between the thin element 6 and the following element 601, which ensures that only one thin element at a time is lifted by the gripping device.

[0068]

[0067] Advantageously, the return means is adjustable. It is in particular configured to adjust the force that it exerts, via the end pieces 701, on the thin element. Thus, the return means 9 is adjustable so as to adjust the force necessary to move the end piece 701 of the rod longitudinally when this end piece is in the plane P1, that is to say in the position that it adopts in the absence of force external to the device exerting itself on the rod.

[0069]

[0068] This makes it possible in particular to adjust the device to different types of thin elements, the mechanical properties of which may vary. This ultimately makes it possible to obtain the desired curvature of the thin element.

[0070]

[0069] When the return means is active, and in particular comprises an actuator, this adjustment generally comprises suitable control of the return means, for example control of the voltage applied to an electromagnet which the return means comprises, or control of the pressure in a pneumatic or hydraulic return means.

[0071]

[0070] Whether the return means 9 is active or passive, a mechanical adjustment to adapt the force exerted by the return means can be provided.

[0072]

[0071] In the example shown here comprising a spring 901, and simply as examples, various solutions are applicable for adjusting the force exerted by the return means. When the end piece 701 is removable (for example when it is screwed), this end piece 701 can be removed in order to change the spring for a spring having different characteristics, or to add a spring preload ring. The thickness of this preload ring then makes it possible to adjust the force exerted by the spring. Alternatively, the return means 9 can comprise any other mechanical means for adjusting the preload of the spring 901, such as a stop for the spring 901 adjustable longitudinally on a thread formed on the rod 7.

[0073]

[0072] As a simple example, for gripping small-sized elements, the suction cup (or other accessory, as will be described below) may have a small diameter, for example between 10 mm and 20 mm, such as 16 mm. The rods 7 may extend in the immediate vicinity of the suction cup, and have a center distance between them, for example between 14 mm and 25 mm, depending on the size of the accessory of the gripping means.

[0074]

[0073] Depending on the thin elements to be grasped and manipulated, the spring 901 may be changed to suit said thin element. For example, when chips containing carbon fibers are used, chips of different shape, thickness, and constitution may be used. The height and stiffness of the springs may be adapted so as to obtain the desired curvature effect with the chips used (or other thin elements).

[0075]

[0074] After the thin element has been grasped, the robot brings the gripping device into a deposition zone where the thin element must be deposited, at a precise location and in a precise orientation. The deposition zone is typically a mold for the manufacture of a part made of composite material in which the thin element participates in constituting the reinforcements.

[0075] The thin element is placed where it must be deposited. In particular, the center of the accessory 5 of the gripping means is aligned with the center of the intended deposition location.

[0076]

[0076] The “deactivation” of the suction cup, that is to say the release of the depression in the suction cup allows the thin element to be released. The rods 7, by pushing the thin element longitudinally, under the effect of the springs 901, help to hold it in position.

[0077]

[0077] When the thin element 6 is a chip that must be deposited in a mold that contains liquid resin, this allows the chip to be released while the suction cup 501 is above the resin, and is not in contact with it. Contact with the resin could damage the suction cup, or even cause resin to be sucked into the device (in particular into the vacuum circuit). The rods 7, by pushing on the chip, ensure that it is pressed into position. If necessary, it may be permissible for the first end pieces 701 to be in contact with liquid resin when the chip is deposited.

[0078]

[0078] Furthermore, in certain embodiments the contact of the rods 7 on the chip (or other thin element) can be used to correct the position of said chip once it has been released by the gripping device. For this, the robot moves the gripping device in order to move the rods 7 which press on the chip, which allows it to slide in the desired direction and / or to correct its orientation. This correction can, if necessary, be carried out while the chip is immersed in the resin.

[0079]

[0079] Figure 5 illustrates two aspects that may be implemented in embodiments of the present invention.

[0080]

[0080] According to a first aspect, the return means 9 comprises an electromagnet 11. The electromagnet 11 makes it possible to control the longitudinal position of the rods 7, and in particular of the first end piece 701, and / or the force that they exert on the thin element 6.

[0081]

[0081] According to the second aspect presented in Figures 5 to 7, the gripping means 4 here comprises, as an accessory, an adhesive part 12. The use of a self-adhesive means such as the adhesive part 12 makes it possible to overcome the problems that can arise from an air-permeable material in being caught by a suction cup. Adhesive part is any flat self-adhesive means, regardless of its shape.

[0082]

[0082] One of the difficulties that may nevertheless arise when using an adhesive part is that it must be changed or cleaned frequently to retain all of its adhesive character. This problem can be resolved by ensuring automated replacement of the adhesive part 12.

[0083]

[0083] For example, the adhesive part can be provided on an element that can be gripped using a suction cup (or a clamp, etc.) that the gripping device then includes. It is thus easy to replace it, the robot carrying the gripping device being able to ensure automatic replacement.

[0084] Preferably, the adhesive part may be formed from a portion of an adhesive roll mounted in a dispenser, and the gripping device is adapted to automatically grip and actuate the dispenser.

[0084]

[0085] As in the case of a “passive” suction cup, i.e. one which is not powered, in a controllable manner, by a vacuum source, it is noted that it is not possible to control the release of the gripping of the thin element when an adhesive means is used for gripping. Therefore, the use of a controllable return means 9, for example using an electromagnet actuator as shown here, is necessary to cause the ejection of the element with respect to the gripping device when the thin element is deposited.

[0085]

[0086] The use of such a controllable recall means is explained with reference to Figures 5 to 7.

[0086]

[0087] In these embodiments, the return means 9 comprises an electromagnet 11, in a linear actuator. The rod 7 is connected to the actuator which makes it possible to adjust the longitudinal position of this rod 7. The return means further comprises an actuator spring 902 which tends to bring the rod into a rest position, in which, when the electromagnet is not activated, the first end piece 701 of the rod 7 is located in a transverse plane closer to the support 2 of the gripping device than the adhesive part 12. In other words, in this position shown in FIG. 5, the electromagnet is not activated and when the adhesive part is brought into contact with a thin element to be gripped, there remains a clearance j between the first end piece 701 and the thin element 6, or, at the very least, the first end piece 701 does not press on the thin element 6.

[0087]

[0088] Figure 6 illustrates the position in which the thin element is lifted by the gripping device. The electromagnet 11 is activated by a small current passing through its coil. It exerts on the rod 7 a force sufficient to overcome the force exerted by the actuator spring 902, and thus exerts a moderate force on the thin element 6, weak enough not to detach it from the adhesive part, but sufficient to bend it slightly as explained with reference to Figure 4.

[0088]

[0089] Once the system robot has brought the gripping device into the deposition area, to release the thin element, the current in the coil of the electromagnet 11 is increased. This has the effect of increasing the force exerted by the rods 7 on the thin element, until it causes it to detach from the adhesive part 12, as shown in Figure 7.

[0089]

[0090] Obviously, the same operation can be used with a "passive" suction cup. Also, the adhesive means can be produced, in an alternative embodiment, by covering a surface of a resin gripping accessory. In particular, when seeking to place chips in a mold for manufacturing a part made of composite material, this mold containing a liquid resin, it is possible to put this surface in contact with the resin present in the mold (or in a container containing the same resin) before gripping a chip. The resin then serves as an adhesive, due to the shear force induced in the resin by the weight of the chip (or other element). In this case, the surface can be recharged with resin each time a chip is deposited in the mold. Furthermore, according to one embodiment, resin can be extruded into the mold directly by or at the level of the accessory of the gripping means.

[0090]

[0091] Furthermore, it is obvious that the electromagnet actuators described above can be replaced by other suitable types of actuators.

[0091]

[0092] Furthermore, when gripping a thin element, a measurement of the permeability of this thin element can be carried out. This measurement can be used to characterize the material constituting the thin element and adapt the parameters allowing its gripping (for example the vacuum level if it is gripped by depression). This measurement can also make it possible, since the material is known, to provide information on the creep of the resin in the thin element.

[0092]

[0093] The forces applied by the thin element to the rods 7, and / or the longitudinal position of the end of said rods 7 when a thin element is held by the device, can make it possible to confirm the actual presence of a thin element (for example a chip) held by the gripping device, and / or can make it possible to mechanically characterize the thin element (in particular its flexural modulus).

[0093]

[0094] The information thus collected by the gripping device can be used to feed a dynamic algorithm and adapt the operating parameters of the gripping device.

[0094]

[0095] For example, if a thin element such as a chip falls from the gripping device, i.e. it is released too early and is therefore deposited imprecisely, knowledge of its permeability and knowledge of its flexural modulus make it possible to adapt the operating parameters of the gripping device for gripping and depositing the next thin element. For example, and depending on the embodiment considered, the vacuum level of the gripping means can be adjusted when the gripping means comprises a suction means, and / or the force exerted by the rods on the chip can be adapted.

[0095]

[0096] The occurrence of other events (failure when taking a thin element, too weak or too strong curvature of the thin element, etc.) may be the condition for an adaptation of the operating parameters.

[0096]

[0097] By learning the device in this way, suitable and precise chip placement can be guaranteed.

[0098] Thus, within the scope of the present invention, a gripping device is proposed that is suitable for gripping a thin element, which is suitable for small elements, for example, whose largest dimension is a few centimeters, and which guarantees that only one element is gripped in a stack of such elements. Furthermore, when the gripping device is used to place chips in a mold for manufacturing a part made of composite material that contains resin, the device makes it possible to avoid contact between the accessory of the gripping means (for example a suction cup) and the resin. The proposed device is simple and compact.

Claims

Claims 1. Gripping device adapted to lift a thin element (6), the gripping device comprising a support and a gripping means (4) fixed to the support (2), the gripping means (4) comprising an accessory (5) adapted to be brought into contact with the thin element (6) and to adhere to a surface of said thin 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 return means (9), the return means (9) being adapted to bring the free end of each rod into a plane further from a reference surface (201) of the support (2), in the longitudinal direction (L), than a longitudinal end of the accessory (5) of the gripping means (4), characterized in that the return means (9) is adjustable so as to adapt the force that it applies.

2. Device according to claim 1, in which the rods (7) are straight and extend substantially parallel in the longitudinal direction (L), the rods (7) being mounted to slide relative to the support (2) on either side of the gripping means (4).

3. Gripping device according to claim 1 or claim 2, in which the gripping means (4) is mounted to slide longitudinally with respect to the support (2), and a second return means (10) tends to bring, in the absence of external constraint, the accessory (5) into a given longitudinal position with respect to the support (2) and the reference surface (201).

4. Gripping device according to any one of claims 1 to 3, in which the accessory (5) of the gripping means (4) comprises a suction cup (501).

5. Gripping device according to any one of claims 1 to 3, in which the accessory (5) of the gripping means (4) comprises an adhesive part (12).

6. Gripping device according to any one of claims 1 to 3, wherein the accessory (5) of the gripping means (4) comprises a surface adapted to be covered with a resin.

7. Gripping device according to any one of the preceding claims, in which the rods (7) are two in number.

8. Gripping device according to any one of the preceding claims, in which the return means (9) comprises a spring (901).

9. Gripping device according to any one of the preceding claims, in which the return means (9) comprises an electromagnet (11).

10. System comprising a gripping device according to any one of the preceding claims and a robot configured to move the gripping means (4) between a container which contains one or more stacks of thin elements and a deposit zone for the thin element (6).

11. System according to claim 10, in which the thin element (6) is a chip comprising carbon fibers in a hardened matrix and the deposition zone is a mold for the manufacture of a part in composite material.

12. A method of manufacturing a part made of composite material, the method comprising providing a system comprising a gripping device adapted to lift a thin element (6), the gripping device comprising a support and a gripping means (4) fixed to the support (2), the gripping means (4) comprising an accessory (5) adapted to be brought into contact with the thin element (6) and to adhere to a surface of said thin 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 return means (9), the return means (9) being adapted to bring the free end of each rod into a plane further from a reference surface (201) of the support (2), in the longitudinal direction (L), than a longitudinal end of the accessory (5) of the gripping means (4),and a robot configured to move the gripping means (4) between a container that contains one or more stacks of thin elements and a deposit area of ​​the thin element (6), the gripping of a thin element (6) in the container by the accessory (5) of the gripping means (4), the application by the rods (7) of a force causing a curvature of the thin element (6), the transport of the gripping means (4) towards the deposit area, and the deposit of the thin element (6) in the deposit area., 13. The method of claim 12, wherein: when the thin element is taken, the permeability of said thin element is measured, and when the rods (7) apply the force causing the curvature of the thin element, the forces applied by the thin element to the rods (7) and / or the longitudinal position of the free ends of said rods (7) are determined in order to confirm the presence of a thin element held by the gripping device, and in order to determine the mechanical characteristics of the thin element.

14. Method according to claim 13, wherein the method comprises an adaptation of at least one operating parameter of the gripping device as a function of the measured permeability and the determined mechanical characteristics.

15. Method according to claim 14, in which the adaptation of at least one operating parameter of the gripping device is conditioned on a detection of a given event, for example an unexpected release of a thin element by the gripping device.

16. Method according to one of claims 12 to 15, in which the deposition of the thin element (6) is carried out by deactivating the gripping means (4) and / or by increasing the distance between the accessory (5) of the gripping means (4) and the plane in which the free ends of the rods (7) are located.

17. Method according to claim 16, wherein, after the deposition of the thin element (6), its position in the deposition zone is corrected by pushing the thin element (6) laterally using the rods (7).

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