Tools and associated pressing methods for pressing down plies of material such as prepreg

Abstract

The present invention relates to a hold-down tool (100), comprising a holder (10) and at least one pressure bagging membrane (20) fixed to the holder (10), the pressure bagging membrane (20) being inflatable with a fluid and configured such that, at a predetermined pressure applied by the fluid-inflated pressure bagging membrane (20) against a surface (S) to be held down, the pressure bagging membrane (20) deforms to ensure surface contact forming a support surface (S') with a surface area included within a predetermined surface area range, the pressure bagging membrane (20) abutting against the surface (S) to be held down.

Description

[Technical Field]

[0001] The present invention relates generally to the technical field of composite ply lay-up.

[0002] The present invention more particularly relates to a hold-down tool and an associated hold-down method for holding down at least one ply of material, such as a prepreg, particularly intended to form at least part of a composite material part. [Background technology]

[0003] As is well known in the art, composite parts can be made from fiber reinforcements that are pre-impregnated with resin. Such fiber reinforcements may be made of carbon, aramid, or any other suitable material depending on the intended use of the part. The resin may be of various types, such as epoxy or polyester resins.

[0004] In the first stage, known as layup, plies of impregnated fiber reinforcement are placed on a negative tool to form a pre-part known as a preform or blank. During this layup, it is customary to use a "debulking" roller, also known as a "hold-down tool," to expel air from the laminate and homogenize the layers of fiber reinforcement. The pre-part can then be pre-compacted under vacuum in an optional compression step, in which the plies are pressed against a mold or negative tool using negative pressure.

[0005] In the next step, known as loading, the spare part is placed on the tool. During this step, the spare part is covered with a stack of films (called a laminate) that have different functions depending on the part required. The laminate may comprise several films, such as a release ply that is generally placed only on the spare part, a waterproof film, a breather fabric to cover the waterproof film, and / or a vacuum bag to seal the laminate.

[0006] In the third stage, known as polymerization, the laminated spare part is placed in a vacuum enclosure and subjected to temperature and pressure cycles to compact it and obtain a part made of composite material known as a blank. After polymerization, the raw part is removed from the tool and inspected (for defects, surface finish, and dimensions).

[0007] Today's press-down tools used in composite layup are vector-type, i.e., they move along an axis. This is the case, for example, when the tool is shaped like a roller. Such a shape is advantageous in that it features a large contact area and can press down a relatively large surface area of ​​the prepreg ply.

[0008] However, depending on their configuration, these tools cannot change rotation or trajectory without risking shearing and potentially damaging the material.

[0009] Additionally, positive or negative corners and / or point supports also require point support tools with appropriate geometries, which generally requires the use of several different tools specifically tailored to a given area.

[0010] As a result, the push down process often has low yields, especially due to the return path and tooling changes that avoid shearing the material.

[0011] After use of these tools, a global vacuum is applied through the bag and purged environment. In addition to expelling air from the laminate and making the layers of fiber reinforcement more uniform, the push-down process limits the appearance of folds in the fiber reinforcement plies that can cause inaccuracies during layup and localized lumps in the material that is set in place during this vacuum process. Summary of the Invention [Problem to be solved by the invention]

[0012] The aim of the present invention is to remedy some or all of the drawbacks of the current prior art, in particular by proposing a solution that does not require purely vectorial tool movements and that is able to adapt to complex lay-up surface profiles. [Means for solving the problem]

[0013] Therefore, according to a first aspect of the present invention, a hold-down tool is proposed, comprising a holder and at least one pressure bagging membrane fixed to the holder, the pressure bagging membrane being inflatable with a fluid and configured such that at a predetermined pressure applied by the fluid-inflated pressure bagging membrane against the surface to be held down, the pressure bagging membrane deforms to ensure surface contact forming a support surface of a surface area included within a predetermined surface area range, the pressure bagging membrane abutting against the surface to be held down.

[0014] This combination of features allows the hold-down tool to deform to conform to the shape of the surface against which it moves and to move along that surface.

[0015] According to one embodiment, the hold-down tool comprises: a fluid inlet opening into the interior space of the pressure bagging membrane and connected to a first connection interface configured to be connected to an external fluid network; a fluid outlet connected to a second connection interface configured to be connected to an external fluid network, the second connection interface opening into the interior space of the pressure bagging membrane; wherein a preferably continuous flow of fluid from the inlet to the outlet can cross the inflatable pressure bagging membrane.

[0016] According to one embodiment, the depressing tool comprises gripping means configured to engage with the element to be depressing, the gripping means preferably comprising a suction cup.

[0017] According to one embodiment, the pressure bagging membrane is at least partially arranged between the holder and the gripping means, the pressure bagging membrane being expandable between two states, namely a contracted state and a fluid-inflated state, and the hold-down tool is configured, in a position for gripping the element to be depressed, such that in the contracted state the pressure bagging membrane does not apply force to the element to be depressed, while in the fluid-inflated state the pressure bagging membrane applies a force to the element to be depressed that is greater than the holding force that the gripping means applies to the element to be depressed.

[0018] According to one embodiment, the hold-down tool comprises at least part of a heating means for heating the fluid inside the membrane, the fluid heating means comprising, for example, an infrared radiation source, for example, located within the pressure bagging membrane. Such heating means integrated into the hold-down tool improves the adhesive performance of the prepreg ply fabric during hold-down, increasing the tackiness of the fabric.

[0019] According to one embodiment, the walls of the pressure bagging membrane are of varying thickness, preferably thicker at the side walls and thinner at the walls that are further from the holder and intended to form all or part of the support surface of the pressure bagging membrane against the surface to be pressed down, and the side walls of the pressure bagging membrane at least partially surround the distal wall.

[0020] According to one embodiment, the hold-down tool comprises a secondary hold-down tool at least partially housed within the pressure bagging membrane, the secondary hold-down tool comprising, for example, at least one roller or spatula.

[0021] According to one embodiment, the inflatable pressure bagging membrane is made of a polymeric material such as plastic or silicone.

[0022] According to one embodiment, the lower limit of the predetermined surface area range is 900 mm 2 is the smallest area.

[0023] According to one embodiment, the upper limit of the predetermined surface area range is 2.25 m2 It is the largest area.

[0024] According to another aspect of the invention, the invention relates to a robotic arm, for example a cobot, characterized in that it comprises a hold-down tool as disclosed above.

[0025] Furthermore, according to another aspect, the invention relates to a hold-down robot comprising a robot arm fitted with a hold-down tool as described above, and control means for controlling the movement of the robot arm.

[0026] According to one embodiment, the push-down robot comprises a fluid network for circulating fluid in the pressure bagging membrane from a fluid inlet to a fluid outlet of said pressure bagging membrane, the fluid network being at least partly controlled by the robot arm control means.

[0027] According to one embodiment, the hold-down robot comprises at least some heating means for heating the fluid inside the membrane, the heating means being offset from the hold-down tool and preferably also from the robot arm.

[0028] According to one embodiment, the fluid consists of air. According to another embodiment, the fluid may consist of oil. In general, any fluid having a boiling point that does not exceed a predetermined maximum operating temperature related to the maximum allowable temperature before polymerization may be suitable. Preferably, this temperature should not exceed 50 degrees. According to one embodiment, the fluid has a boiling point of 50 degrees Celsius or less.

[0029] According to a further aspect, the invention relates to a method for depressing a surface to be depressing by a depressing tool as described above, characterized in that the depressing membrane is inflated by a fluid and moves over the surface to be depressing while maintaining a contact interface between the depressing membrane and the surface to be depressing.

[0030] According to one embodiment, the hold-down method is carried out by a hold-down robot as described above.

[0031] According to one embodiment, the depression method comprises: an initial step of inflating the pressure bagging membrane to a predetermined average internal pressure that is strictly lower than the maximum internal pressure of the pressure bagging membrane; - placing a pressure bagging membrane against the surface to be depressed and applying a predetermined force to the surface; moving the pressure bagging membrane along the surface to be depressed; Includes.

[0032] According to one embodiment, the depression method includes the steps of moving the pressure bagging membrane along the surface to be depressed while simultaneously varying the internal pressure of the pressure bagging membrane.

[0033] According to one embodiment, the depression tool moves over the surface to be depressed along a trajectory characterized by at least one curved portion.

[0034] According to one embodiment, the hold-down tool moves over the surface to be held down by sliding an inflatable pressure bagging membrane over the surface to be held down.

[0035] According to one embodiment, the step of positioning the pressure bagging membrane against the surface to be depressed and applying a predetermined force to the surface to be depressed may be a step of moving a tool by a robot to move the pressure bagging membrane towards and against the surface to be depressed.

[0036] According to one embodiment, the hold-down tool comprises a gripping means configured to engage with the element to be held down, and the hold-down method preferably comprises a step of gripping the element to be held down by the gripping means before the initial step of inflating the pressure bagging membrane.

[0037] According to one embodiment, the hold-down method preferably includes, prior to the step of moving the hold-down membrane along the surface to be held down, a step of expanding the hold-down membrane until the hold-down membrane exerts a force on the element to be held down that is greater than the holding force exerted by the gripping means on the element to be held down, at least to separate the element to be held down from the gripping means.

[0038] According to one embodiment, the hold-down tool comprises a secondary hold-down tool at least partially housed within the pressure bagging membrane, preferably completely housed within the pressure bagging membrane, and the hold-down method comprises a step of holding down the surface to be held down by the secondary hold-down tool.

[0039] According to one embodiment, the step of depressing the surface to be depressed with a secondary depressing tool includes a step of moving the secondary depressing tool along the surface to be depressed, the secondary depressing tool housed within the membrane preferably exerting a force on the element to be depressed through the wall of the membrane that is greater than or equal to the force that the depressing membrane exerts on the element to be depressed.

[0040] According to one embodiment, the step of depressing the depressed surface with the secondary depressing tool may be performed independently of the movement of the membrane during the depressing by said membrane, in other words, the step of depressing the depressed surface with the secondary depressing tool may be performed while the depressing membrane is moving along the depressed surface or without the membrane moving relative to the depressed surface.

[0041] According to one embodiment, the step of depressing the depressed surface with the secondary depressing tool is performed when the force exerted by the pressure bagging membrane on the depressed element has a value equal to or greater than a predetermined threshold value. [Brief explanation of the drawings]

[0042] Other features and advantages of the present invention will become apparent from a consideration of the following description taken in conjunction with the accompanying drawings.

[0043] [Figure 1] 1 illustrates a diagram of a cobot with a hold-down tool according to one embodiment. [Figure 2] 1 illustrates a top perspective view of a hold-down tool according to one embodiment. [Figure 3] 3 shows a parallel perspective view from below of the hold-down tool according to the embodiment of FIG. 2; [Figure 4] 3 shows a side view of the hold-down tool according to the embodiment of FIG. 2; [Figure 5] 3 shows a side view of the hold-down tool according to the embodiment of FIG. 2, with the pressure bagging membrane in a slightly expanded state. [Figure 6] 3 shows a side view of the hold-down tool according to the embodiment of FIG. 2, with the pressure bagging membrane in an inflated state. [Figure 7] 3 shows a side view of the hold-down tool according to the embodiment of FIG. 2, approaching the surface to be held down. [Figure 8] 3 shows a side view of the hold-down tool according to the embodiment of FIG. 2 in contact with the surface to be held down. [Figure 9] 3 shows a perspective view of a hold-down tool according to the embodiment of FIG. 2 in contact with a surface to be held down; [Figure 10] 3 shows a partial cross-sectional side view of a hold-down tool according to the embodiment of FIG. 2 with the pressure bagging membrane in an inflated state and with a secondary hold-down tool housed within the pressure bagging membrane.

[0044] For the sake of clarity, identical or similar elements are identified by the same reference numerals in all figures. DETAILED DESCRIPTION OF THE INVENTION

[0045] FIG. 1 shows a diagram of a robot 1, in this case a cobot, with a robotic arm 2. In other words, this embodiment includes a "collaborative" robot 1, i.e., a robot 1 configured to work in a common space and interact with humans. Cobots generally rely on an operator for their actions. For example, when applied to an automated production line, several cobots are likely to work alongside or in close proximity to a human operator.

[0046] The robot 1 has at the distal end of the articulated arm 2 an interface configured to fix a hold-down tool 100, the properties of which, in particular with regard to dimensions, may vary depending on the shape and size of the tool 100 to be gripped.

[0047] The hold-down tool 100 also has an interface for attachment to the arm 2 of the robot 1 .

[0048] The hold-down tool 100 in particular consists of a holder 10 axially oriented along a reference axis A, with its proximal or rear side facing the distal end of the articulated arm 2 and its distal or front side facing axially opposite the rear side, towards the front or surface S to be held down (see FIG. 5). The interface of the hold-down tool 100 is located on the rear side 10A of the holder 10. The interface for assembling the hold-down tool 100 to the arm 1 of the robot 2 is configured so that the reference axis A is coaxial with the reference axis of the reference end 2' of the articulated arm 2 of the robot 1 when the hold-down tool 100 is assembled to the arm 2 of the robot 1 as shown in FIG.

[0049] The function of the hold-down tool 100 is to hold down the surface of, for example, a prepreg ply. In particular, a relatively wide tool 100, such as a roller, is used so that as it moves against the surface being held down, it can extend along a dimension in the plane of the surface being held down that is wide enough to cover the entire range of average air bubbles trapped in the prepreg ply. Another advantage of having the tool 100 cover a dimension that is wide enough in the plane of the surface being held down is that a relatively large surface area S to be held down can be covered, thus increasing efficiency and output. However, such rollers do not allow complex movements due to their shape, which limits gestures and, further, the risk that such movements may shear and damage the material.

[0050] For the purposes of the present invention, and contrary to common belief, the hold-down tool 100 comprises a pressure bagging membrane 20 fixed to a holder 10, the pressure bagging membrane 20 being inflatable by a fluid. In this case, the fluid used is air. The pneumatic membrane 20 is arranged on the front side of the holder 10 so that it can abut against the surface S to be held down. The pressure bagging membrane 20 is configured to ensure a surface contact which deforms and forms a support surface S' of the pressure bagging membrane 20 abutting against the surface S to be held down.

[0051] The pressure bagging membrane 20 comprises walls 22 that define an internal space 21 of the pressure bagging membrane 20 and define an envelope configured to contain a fluid. The walls 22 of the membrane 20 are fluid-tight. In particular, the pressure bagging membrane 20 comprises at least one distal wall 22B, which is a wall intended to abut against the surface S to be pressed down, so as to form all or part of the support surface S' of the membrane 20. Axially opposite this distal wall 22B of the membrane 20, the pressure bagging membrane 20 comprises a proximal wall that directly faces the holder 10 and is intended to be fastened to this support 10. These proximal and distal walls 22B are connected by at least one side wall 22A of the membrane 20. The side wall 22A of the pressure bagging membrane thus surrounds and frames the distal wall 22B. The proximal wall, the distal wall 22B, and the side wall 22A cooperate to define an interior space 21 of the membrane 20.

[0052] When the pressure bagging membrane 20 is in an expanded state, away from the depressed surface S, and is free from stress, i.e., not in contact with the depressed surface, and there is no pressure applied to the pressure bagging membrane 20 by an external element, the proximal and distal walls 22B of the membrane 20 extend approximately parallel to each other and in planes each oriented approximately perpendicular to the reference axis A.

[0053] In certain configurations, the walls 22 of the pressure bagging membrane 20 have different thicknesses such that the thickness of the walls 22 of the membrane 20 varies depending on its location. In particular, the walls 22 are thicker at the side walls 22A and thinner at the distal walls 22B. In the illustrated embodiment, the side walls 22A have a thickness between 5 and 8 mm, and the distal walls 22B have a thickness between 0.5 and 8 mm.

[0054] Generally speaking, each side wall 22A has a thickness of 3 mm or greater, more preferably 5 mm or greater, and / or 10 mm or greater, and more preferably 8 mm or greater. Additionally or alternatively, distal wall 22B has a thickness of 0.5 mm or greater, more preferably 1 mm or greater, and / or 3 mm or greater, and more preferably 2 mm or greater.

[0055] Such a configuration, in which the proximal and distal walls 22B of the membrane 20 are thinner than the side wall 22A and are reinforced by a particularly greater thickness at the side wall 22A, facilitates the inflatable membrane 20 to pass along the variable geometry of the mottled surface S while maintaining maximum contact with such surface S, thus ensuring the largest possible support surface S' of the membrane 20 during movement of the membrane 20, despite the non-zero gradient of the topography of the mottled surface S.

[0056] In this manner, the pressure bagging membrane 20 has the flexibility to locally conform to the shape of the depressed surface S. This flexibility ensures that at a given pressure of the fluid-filled pressure bagging membrane 20 against the depressed surface S, the pressure bagging membrane 20 will deform to ensure surface contact with the depressed surface S to form a support surface S' having an area within the given surface area range of the pressure bagging membrane 20.

[0057] During depression, the pressure bagging membrane 20 contacts and abuts the surface S to be depressed, and the pressure exerted by the pressure bagging membrane 20 against the surface S to be depressed allows the pressure bagging membrane 20 to slide over the surface S to be depressed as it moves relative to the surface S while ensuring its depression function.

[0058] When a tool 100 of this kind performs a pressing action against a given surface S to be pressed against, the pressure bagging membrane 20 is pressed against this surface S to be pressed against as follows. be strong enough to obtain a contact interface between the pressure bagging membrane 20 and the surface S to be depressed that has a sufficiently large area so that the depression is effective and the area of ​​the support surface S' is as uniform and continuous as possible; However, this pressure is weak enough that it does not, on the one hand, degrade the material being pressed down on, and, on the other hand, does not prevent the movement of the pressure bagging membrane 20 against the surface of the material being pressed down on.

[0059] To meet these requirements, the optimum range of the predetermined area of ​​the support surface S' is preferably limited as follows: - Lower limit: 900mm 2 and / or - Maximum 2.25m 2 The maximum area of.

[0060] In fact, if the support surface S' is too large, it will be difficult to press down on surfaces with too complex a topography, which will be detrimental to the dexterity of the tool 100 during use. Conversely, if the support surface S' is too small, the pressing efficiency and output of the tool 100 will be adversely affected. In practice, this surface can be predetermined in some way by the lateral dimensions of the pressure bagging membrane 20. For example, the surface area of ​​the distal wall 22B can be set at its lower limit of 900 mm 2 and / or have an upper limit of 2.25m 2 The surface area of ​​the substrate may be a maximum of 100 mm.

[0061] In this exemplary embodiment, the inflatable pressure bagging membrane 20 is made of a polymeric material, such as plastic or silicone. The material comprising the inflatable pressure bagging membrane 20 is selected to allow for good depression and flattening despite the presence of reliefs or obstacles on the surface being depressed. These reliefs or obstacles may be, for example, reinforcements that impart complex geometries to the surface being depressed. A material that is sufficiently elastic to deform, such as silicone, provides an inflatable pressure bagging membrane 20 whose stretched walls improve depression efficiency despite the complex geometries of the surface being depressed.

[0062] According to one embodiment, the inflatable pressure bagging membrane 20 is made of an elastomeric material. The material forming the inflatable membrane 20 preferably has a hardness of 5 Shore A or greater, even more preferably 10 Shore A or greater, and / or 40 Shore A or less, even more preferably 30 Shore A or less. Such hardness provides improved durability for use in this field of depression while imparting flexibility for depression of complex geometries by allowing the membrane to reach the most difficult corners of surfaces.

[0063] According to the invention, the hold-down tool 100 is configured to circulate a fluid, preferably in gaseous form, through the inflatable pressure bagging membrane 20. The hold-down tool 100 therefore comprises a fluid inlet 101 opening into the interior space 21 of the pressure bagging membrane 20 and connected to a first connection interface 11 configured to be connected to an external fluid network 40, and a fluid outlet 102 opening into the interior space of the pressure bagging membrane 20 and connected to a second connection interface 12 configured to be connected to the external fluid network 40. In this way, the fluid can flow, preferably continuously, through the inflatable membrane 20 from the inlet 101 to the outlet 102. It is also possible to vary the internal fluid pressure of the inflatable pressure bagging membrane 20.

[0064] The external fluid network 40 comprises a fluid source that is preferably remote from the hold-down tool 100, and even more preferably remote from the arm 2 of the robot 1. It may, for example, be carried at the base of the cobot 1, or may be offset from said cobot 1, for example near a control cabinet. The fluid network 40 includes flexible fluid circulation lines so that it can extend along the various joints of the robot without affecting its range of motion.

[0065] Thanks to this configuration of the pressing tool 100, the support surface S' of the inflatable membrane 20 can be adjusted according to the size of the inflatable membrane and the internal filling pressure of the fluid in the internal space 21 of the pressure bagging membrane 20. This internal pressure of the pressure bagging membrane 20, which depends on the fluid contained therein and circulating therethrough via the fluid network 40, can vary as a function of the robot arm 2, which can apply pressure by moving the tool 100 and bringing the tool 100, and in particular its support 10, closer to the surface S to be pressed down. In practice, the robot arm 2 is controlled to enable pressing with a given force, and in a second step, the internal pressure of the inflatable membrane 20 is adjusted in the desired direction by controlling the fluid network 40. If the pressure is too great, the membrane 20 will tend to contract in order to maintain the pressure. On the other hand, if excessive pressure is applied to the pressure bagging membrane 20, it will become too rigid and therefore will have difficulty penetrating defects in the part. Therefore, a moderate expansion is necessary so that the membrane 20 can penetrate the recesses of the mold. According to one embodiment, the pressure bagging membrane is inflated to an internal pressure of at least 2 bar, preferably at least 4 bar, and / or at most 9 bar, preferably at most 7 bar. With the materials used and wall thicknesses defined in this embodiment, an internal pressure of about 4 bar is particularly advantageous.

[0066] The holder 10 carrying the pressure bagging membrane 20 is generally plate-shaped and extends in a plane perpendicular to the reference axis A. In particular, to facilitate the dexterity of the hold-down tool 100, the holder plate 10 has a holder periphery whose template defines a shape that substantially corresponds to the shape of the cross section of the pressure bagging membrane 20. Furthermore, this holder plate supports first and second connection interfaces 11, 12 fixed thereto.

[0067] In a compaction step, the spare part is known to be pre-compacted under vacuum by using negative pressure to force the plies into a mold. Such fabric compaction steps are generally carried out using vacuum bags.

[0068] According to the invention, the tool 100 comprises gripping means 30 configured to engage with the element 200 to be depressed. These gripping means here comprise suction cups 31. These suction cups are distributed around the pressure bagging membrane 20 and are carried by the holder 10 of the tool 100.

[0069] The pressure bagging membrane 20 is at least partially disposed in the space between the holder 10 and the gripping means 30. In this way, the suction cups 31 do not interfere with the use of the inflatable membrane 20. The pressure bagging membrane 20 is inflatable between two states: a deflated state and a fluid-inflated state.

[0070] The hold-down tool 100 is configured such that, in the position for gripping the hold-down element 200 and in the contracted state, the pressure bagging membrane 20 does not exert any force on the hold-down element 200 (see FIG. 5 ). In such a configuration, the pressure bagging membrane 20 is integrally arranged in the space between the holder 10 and the gripping means 30, the pressure bagging membrane 20 being axially set back from a hooking plane P perpendicular to the reference axis A in which the suction cups 31 lie.

[0071] The hold-down tool 100 is further configured such that, in its position for gripping the hold-down element 200 and in its fluid-inflated state, the pressure-bagging membrane 20 exerts a force on the hold-down element 200 that is greater than the holding force exerted on said hold-down element 200 by the gripping means 30. In this configuration, the membrane 20 is inflated and its volume increases. Since the gripping means 30 is fixed relative to the holder 10 and the membrane 20 is fixed to the holder at its proximal wall 22, the expansion of the membrane 20 moves the distal wall 22B of the membrane 20 away from the proximal wall 22B until the distance is greater than the distance separating the hooking plane P from the holder. Thus, in the gripping position of the hold-down element 200 located in the hooking plane P, there is an interaction generated by the membrane 20 in its inflated state contacting and abutting the hold-down element 200. This position is maintained until the force that the membrane 20 exerts on the element 200 to be depressed becomes greater than the holding force of the suction cups 31 attached to the element 200 to be depressed (see FIG. 6). During the step of depression by the membrane 20, the gripping means 30 are inactive and the membrane 20 is in an expanded state so that it protrudes axially from the gripping means 30. In other words, during the step of depression in which the depression membrane 20 moves along the surface S to be depressed, the membrane 20 expands so that the distance between the distal wall 22B and the proximal wall is strictly greater than the distance separating the hooking plane P from the holder 10, until this distance is greater than the distance separating the hooking plane P from the holder 10. In such a configuration, the gripping means 30 do not hinder the progression of the membrane 20 along the surface S to be depressed, even if the surface S to be depressed has a relief.

[0072] Such a tool 100 allows the suction cups 31 to hold the fabric forming the element 200 to be pressed down and at the same time press the fabric against the mould. These steps are separate but are performed by the same tool 100. After gripping the element 200 to be pressed down in the gripping step, there comes a moment in the subsequent pressing step when the supporting force of the membrane 20 removes the force from the suction cups 31, causing them to detach.

[0073] In certain applications, it may be possible to perform the two steps of gripping and pressing simultaneously, allowing a satisfactory result to be seen and the fabric to be held. Thanks to such an arrangement, the ply can be picked up by the suction cups 31 and pressed against a mould or negative tool by the action of the inflatable membrane 20, which allows pressing against virtually any shape.

[0074] In an alternative or complementary embodiment, it is also possible to provide gripping means housed within and / or fixed to the membrane 20. For example, suction cups can be arranged on the membrane 20 itself, like the suction cups on an octopus's arms.

[0075] The gripping means 30 can be configured to be movable, preferably controlled by a control means, so that they can be moved between an extended gripping position and a position retracted towards the holder 10 so as not to interfere with the depression by the pressure bagging membrane 20. For example, by sliding a rod supporting a suction cup 31, the associated suction cup 31 can be moved between a retracted position in which it is located on the reference surface of the holder 10, and an extended position axially away from the holder 10 on the side of the pressure bagging membrane 20.

[0076] Experience has shown that the efficiency of the compression step, i.e., the bonding of the fabric to the mold, improves depending on the duration and temperature of this operation. To improve yield and ensure that the material conforms to the shape of the mold and remains bonded to it, the fluid in the interior 21 of the membrane 20 is heated to a temperature of at least 15 degrees Celsius, preferably at least 20 degrees Celsius. The circulation of a hot fluid (typically liquid or gas) inside the inflatable membrane 20 thus simulates a temperature close to that of the human body, which is typically reproduced by an operator in the pressing down method when manually forming fabrics.

[0077] To achieve such temperatures, the tool 100 includes at least some heating means for heating the fluid inside the pressure-bagging membrane 20, thus improving its efficiency. The fluid heating means are arranged along the fluid network 40 and can be located at one or more different points. For example, a primary fluid heating means may be offset from the hold-down tool 100 and from the arm 2 of the robot 1, and / or a secondary heating means separate from the primary heating means may be included inside the inflatable membrane 20, i.e., housed in the interior space 21 of the inflatable membrane 20. The continuous circulation of fluid through the inflatable membrane 20 maintains a constant or nearly constant temperature inside the inflatable membrane 20, thus preventing heat loss to the membrane that could occur due to the transfer of thermal energy between the membrane 20 and the element 20 being held down when they are in contact.

[0078] Examples of primary or secondary heating means contained within the inflatable membrane 20 or carried externally, for example by the holder 10, may comprise one or more infrared radiation sources.

[0079] The heating means is configured so that the heat generated and supplied to the membrane is limited to avoid inducing polymerization of the prepreg plies. Preferably, the heating means is configured to heat the fluid circulating within the membrane 20 to a temperature of 15° C. or higher, preferably 25° C. or higher and / or 50° C. or lower, even more preferably 40° C. or higher. In this embodiment, the air within the membrane is heated to a temperature of 40° C. This temperature improves the adhesion of the prepreg.

[0080] In an alternative or complementary embodiment, the heating means can be configured so that the heat generated and supplied to the membrane is sufficient to initiate the entire polymerization reaction. In this case, the hold-down tool, and in particular the material from which the membrane is made, must be adapted to withstand such heat. This heat can be, for example, 180 degrees Celsius.

[0081] The hold-down robot 1 comprises an arm 2 of the robot 1 to which a hold-down tool 100 is attached, and control means for controlling the movement of the arm 2 of the robot 1 and the hold-down tool 100 itself. Just as the control means can be used to control the gripping means 30 and the heating means, the same control means can be used to control the flow of fluid through the fluid network 40, and in particular the flow of fluid within the pressure bagging membrane 20 from the fluid inlet 101 to the fluid outlet 102 of the pressure bagging membrane 20.

[0082] The method of use of hold-down tool 100 will be better understood from the following description.

[0083] The process of pressing down the surface S to be pressed down by such a pressing down tool 100 of the present invention essentially consists of expanding the pressing down membrane 20 with a fluid and moving the pressing down membrane 20 above the surface S to be pressed down while maintaining a contact interface between the pressing down membrane 20 and the surface S to be pressed down.

[0084] In the initial inflation step, the pressure bagging membrane 20 is inflated to a predetermined average internal pressure that is strictly below the maximum internal pressure of the pressure bagging membrane 20 .

[0085] The pressure bagging membrane 20 is then moved towards the depressed surface S in a moving step, abutting against the depressed surface S and applying a predetermined force to the depressed surface S. The pressure bagging membrane 20 is then moved along the depressed surface S.

[0086] Simultaneously with the step of moving the pressure bagging membrane 20 along the surface S to be depressed, a step of varying the internal pressure of the pressure bagging membrane 20 is carried out to adapt the pressure to the changing relief of the surface S to be depressed.

[0087] In this method, the pressure may be varied or maintained at a constant level depending on the area of ​​the surface to be coated or the geometry of the surface.

[0088] The internal pressure of the pressure bagging membrane 20 can be varied according to various parameters controlled by the robot, or more precisely by the control means. These parameters can be, for example, the distance separating the hold-down tool 100 from the surface S to be held down, making it possible to vary the internal pressure of the pressure bagging membrane 20 at a constant fluid volume within the membrane 20. In particular, by varying the distance between the surface S to be held down and the holder 10, it is possible to vary the pressure exerted by the membrane 20. Similarly, the control means can vary the speed of circulation of fluid in the inflatable membrane 20 to vary its internal pressure.

[0089] In this depression method, the arm 2 of the robot 1 is moved to apply a predetermined force to the surface S to be depressed, after an initial step of expanding the pressure bagging membrane 20 towards and abutting the surface S to be depressed.

[0090] In effect, the hold-down tool 100 presses the surface S to be held down with a given force solely through the pressure bagging membrane 20, and the control means allows for management of the pressure of the inflatable membrane 20. In this effort, if the pressure of the pressure bagging membrane 20 on the surface S to be held down is too great, the pressure bagging membrane 20 will tend to contract in order to maintain the pressure due to the constant flow of air circulating inside. Therefore, if too much pressure is applied, the pressure bagging membrane 20 will expand further before pressing down, and the pressure bagging membrane 20 will penetrate less or not at all into the defects in the part.

[0091] For this reason, the control means preferably inflate the pressure bagging membrane 20 with a relatively limited internal pressure to fit into the mold recess, the aim being to keep the internal pressure as constant as possible during pressing down. According to one embodiment, the pressure bagging membrane is inflated to an internal pressure of at least 2 bar, preferably at least 4 bar, and / or at most 9 bar, preferably at most 7 bar. With the materials used and wall thicknesses defined in this embodiment, an internal pressure of about 4 bar is particularly advantageous.

[0092] 10 illustrates an embodiment that differs from those described above essentially in that the hold-down tool 100 comprises at least one secondary hold-down tool 120 housed at least partially within the pressure bagging membrane 20. Such a tool is in fact an active tool that performs the hold-down function independently of the pressure bagging membrane 20. It is therefore not a passive structure without a hold-down function, such as a secondary tool 120 or a spacer mechanism that may be provided to protect the membrane from premature wear due to rubbing against the holder 10.

[0093] According to one embodiment, such a secondary tool 120 separate from the membrane may comprise a tool selected from at least one roller, at least one spatula (not shown), and at least one push-down ball (not shown).

[0094] In the case of a push-down ball, the secondary tool 120 can, for example, comprise a holder and a push-down ball rotatably held by the holder of the secondary tool 120, the push-down ball preferably being configured such that at a predetermined pressure of the push-down ball against the surface being pushed down, the push-down ball elastically deforms to ensure surface contact that forms a bearing surface for the push-down ball against the surface being pushed down. This type of tool provides a small contact surface and multi-directional movement.

[0095] 10 , secondary push-down tool 120 includes rollers 121 attached to holders 123 that are movable on rails 124. Rails 124 are arranged on both sides of the rollers, and each rail guides one end of a shaft that rotatably carries roller 121. Each rail 124 is fixed to holder 10, and movement of roller 121 is actuated by a cylinder 122 that is connected to holder 10 at a proximal end and connected to holder 123 at a distal end opposite the proximal end. Rails 124 are configured to guide movement of the rollers actuated by cylinder 122.

[0096] Generally speaking, such a roller-mounted secondary hold-down tool 120 provides a larger contact surface and unidirectional movement.

[0097] Preferably, the secondary hold-down tool 120 is used in a second step after the membrane 20 has pressed the fabric of the depressed element 200 against, for example, a contact surface of a mold or a layer of previously laid down fabric. In particular, the step of pressing down the depressed surface by the secondary hold-down tool 120 is performed when the force applied by the pressure bagging membrane 20 to the depressed element 200 has a value equal to or greater than a predetermined threshold. The secondary hold-down tool 120 is particularly useful for pressing down the depressed element 200 over areas that require more effort than the membrane itself.

[0098] In use, the surface to be depressed is depressed by the pressure bagging membrane. Then, when for a predetermined reason, in particular due to the topography of the part, it is necessary to apply a force above a predetermined threshold to the clad element 200, a control means controls the movement of the secondary hold-down tool 120. The secondary hold-down tool 120 is movable between a retracted position (see FIG. 10 ), axially retracted from the tapping plane P, and a deployed position, located beyond the tapping plane and abutting the element 200 to be depressed through the wall of the membrane 20.

[0099] The hold-down robot, in particular the gripping means 30, which is operated directly by the control means and in this case a suction cup 31, blocks or restricts the membrane 20 at least partially laterally, and the secondary hold-down tool 120 moves into the interior space 21 of the membrane 20 and can hold down areas of the membrane 20 that are difficult to reach, in particular when the secondary hold-down tool 120 comprises a hold-down ball.

[0100] The secondary hold-down tool 120 comprises an actuation means, such as an integrated motor, for moving the secondary hold-down tool 120 within the membrane 20. In the case of rollers 121, and for small to medium sized parts, this movement is generally unidirectional. In the case of hold-down balls, the movement may be multidirectional. In such an arrangement, the means for moving the hold-down balls, as opposed to simple rails, is configured for multidirectional movement, for example a ball joint controlled by a control means, the ball joint being arranged, preferably interposed, between the holder 10 inside the membrane 20 and the holder of the secondary tool 120.

[0101] Thus, the secondary padding tool 120 comes into action in the second step after the membrane has pressed the fabric against the contact surface.

[0102] Generally speaking, such a tool 100 is versatile and can be used for most parts. It improves the performance of the hold-down method over time by allowing at least two separate operations, namely, picking up and placing using the gripping means 30 and pressing down using the pressure bagging membrane 20, to be performed with the same tool. Furthermore, such a tool 100, like a vacuum tarpaulin, ensures a more uniform pressure across the entire contact surface, but with the flexibility to be positioned in place at any time. Furthermore, such a hold-down tool 100 also improves cycle times thanks to the ability to change the temperature of the fluid circulating within the pressure bagging membrane 20. The present invention is particularly suitable for placing a first ply on a mold and then pressing it down. This is because the first ply is subject to additional constraints compared to subsequent plies. The surface roughness of the mold is much smaller than that of the plies, resulting in greater sliding stresses. In fact, the hold-down tool according to the present invention provides very satisfactory results, especially for pressing down the first ply in a mold.

[0103] The tool 100 proposed in this technical solution is not vector-based. Therefore, it can perform straight, curved and circular trajectories and act as a support point. Also, productivity is improved in the sense that the tool 100 does not have to "peel" the pressure bagging membrane 20 from the lay-up surface S being pressed down, and does not have to go through a step (pure movement) back to the start of the trajectory.

[0104] Of course, the present invention has been described above by way of example, and it is understood that those skilled in the art can create various variant embodiments of the invention without departing from the scope of the invention.

[0105] It is emphasized that all features as would be taught to one skilled in the art from this disclosure, the drawings, and the appended claims, even if specifically described in connection with other particular features, can be combined individually or in any combination with other features or feature groups disclosed herein, unless expressly excluded or unless such combination is impossible or meaningless given the technical circumstances.

Claims

1. 1. A hold-down tool (100) comprising a holder (10) and at least one pressure bagging membrane (20) fixed to the holder (10), the pressure bagging membrane (20) being inflatable with a fluid and configured such that, at a predetermined pressure applied by the fluid-inflated pressure bagging membrane (20) to a surface (S) to be held down, the pressure bagging membrane (20) deforms to ensure surface contact forming a support surface (S') having a surface area included within a predetermined surface area range, the pressure bagging membrane (20) abutting against the surface (S) to be held down.

2. a fluid inlet (101) opening into the interior space (21) of said pressure bagging membrane (20) and connected to a first connection interface (11) adapted to be connected to an external fluid network (40); a fluid outlet (102) opening into the interior space of said pressure bagging membrane (20) and connected to a second connection interface (12) configured to be connected to an external fluid network (40); Equipped with 2. The hold-down tool (100) of claim 1, wherein a fluid flow, preferably continuously, from the inlet (101) to the outlet (102) can cross the inflatable membrane (20).

3. 3. A hold-down tool (100) according to claim 1 or 2, characterized in that it comprises gripping means (30) configured to engage with the element (200) to be held down, said gripping means (30) preferably comprising a suction cup (31).

4. 4. The hold-down tool (100) of claim 3, wherein the pressure bagging membrane (20) is at least partially disposed between the holder (10) and the gripping means (30), the pressure bagging membrane (20) being expandable between two states, namely a contracted state and a fluid-inflated state, and the hold-down tool (100) is configured such that, when in the contracted state, the pressure bagging membrane (20) exerts no force on the element (200) to be held down, while in the fluid-inflated state the pressure bagging membrane (20) exerts a force on the element (200) that is greater than the holding force that the gripping means (30) exerts on the element (200).

5. 5. The hold-down tool (100) of any one of claims 1 to 4, characterized in that it comprises at least some heating means for heating the fluid inside the pressure bagging membrane (20), the fluid heating means comprising, for example, an infrared radiation source, for example located within the pressure bagging membrane (20).

6. 6. The hold-down tool according to claim 1, wherein the walls (22) of the pressure bagging membrane (20) are of varying thickness, preferably thicker at the side walls (22A) and thinner at the walls (22B) that are remote from the holder (10) and intended to form all or part of the support surface (S') of the pressure bagging membrane (20) against the surface (S) to be held down, and wherein the side walls (22A) of the pressure bagging membrane (20) at least partially surround the distal walls (22B).

7. The hold-down tool (100) of any one of claims 1 to 6, characterized in that it comprises a secondary hold-down tool (120) at least partially housed in the pressure bagging membrane (20), the secondary hold-down tool (120) comprising, for example, at least one roller, ball, or hold-down spatula.

8. The hold-down tool (100) according to any one of the preceding claims, characterized in that the inflatable pressure bagging membrane (20) is made of a polymer material, for example made of plastic or silicone.

9. The predetermined surface area range has a lower limit of 900 mm ２ The hold-down tool (100) according to any one of the preceding claims, characterized in that it has a minimum area of:

10. The predetermined surface area range has a lower limit of 2.25 m ２ 10. The hold-down tool (100) according to any one of the preceding claims, characterized in that it has a minimum area of:

11. An arm (2) of a robot (1), for example a cobot, characterized in that it comprises a hold-down tool (100) according to any one of claims 1 to 10.

12. A push-down robot (1) comprising an arm (2) of a robot (1) to which a push-down tool (100) according to any one of claims 1 to 10 is attached, and control means for controlling the movement of the arm (2) of the robot (1).

13. 13. A push-down robot (1) comprising at least the push-down tool (100) of claim 2, characterized in that it comprises a fluid network (40) for ensuring circulation of fluid within the pressure bagging membrane (20) from the fluid inlet (101) to the fluid outlet (102) of the pressure bagging membrane (20), the fluid network (40) being at least partially controlled by the control means of the arm (2) of the robot (1).

14. 14. The push-down robot according to claim 12 or 13, characterized in that it comprises at least part of a heating means for heating the fluid inside the pressure bagging membrane (20), the heating means being offset from the push-down tool (100), preferably also from the arm (2) of the robot (1).

15. The push-down robot according to any one of claims 12 to 14, wherein the fluid is air.

16. A method for depressing a surface to be depressed by a depressing tool according to any one of claims 1 to 10, comprising the steps of: wherein the push-down membrane (20) is expanded by the fluid and the push-down membrane (20) is moved above the surface (S) to be pushed down while maintaining a contact interface between the push-down membrane (20) and the surface (S) to be pushed down.

17. The push-down method according to claim 16, which is carried out by a push-down robot according to any one of claims 12 to 15.

18. an initial step of inflating the pressure bagging membrane (20) to a predetermined average internal pressure strictly lower than the maximum internal pressure of the pressure bagging membrane (20); - placing the pressure bagging membrane (20) against the depressed surface (S) and applying a predetermined force to the depressed surface (S); - moving the pressure bagging membrane (20) along the depressed surface (S); 18. The method of claim 16 or 17, further comprising:

19. 20. The method of claim 18, further comprising the step of varying the internal pressure of the pressure bagging membrane (20) simultaneously with the step of moving the pressure bagging membrane (20) along the surface (S) to be depressed.

20. 20. The method of any one of claims 16 to 19, wherein the hold-down tool (100) comprises gripping means (30) configured to engage with the element (200) to be held down, the method comprising the step of gripping the element (200) to be held down by the gripping means (30).

21. 21. The method of claim 20, further comprising the step of expanding the pressure bagging membrane (20) to separate the depressed element (200) from the gripping means (30) until the pressure bagging membrane (20) exerts a force on the depressed element (200) that is at least greater than the holding force exerted by the gripping means (30) on the depressed element (200).

22. 22. The method of claim 16, wherein the hold-down tool (100) is at least partially housed within the hold-down membrane (20), and preferably comprises a secondary hold-down tool (120) housed completely within the hold-down membrane (20), and the hold-down membrane includes a step of holding down the surface to be held down by the secondary hold-down tool (120).

23. 23. The method of claim 22, wherein the step of pressing down the surface to be pressed down by the secondary pressing tool (120) comprises a step of moving the secondary pressing tool (120) along the surface to be pressed down, the secondary pressing tool (120) housed within the membrane (20) exerting a force on the element to be pressed down (200) through the wall of the membrane (20), preferably greater than or equal to the force exerted by the pressing down membrane (20) on the element to be pressed down (200).

24. 24. The method of claim 23, wherein the step of depressing the depressed surface with the secondary depressing tool (120) is performed when the force exerted by the pressure bagging membrane (20) against the depressed element (200) is greater than or equal to a predetermined threshold.

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