Pressure generator and actuator system comprising said pressure generator with a useful actuator

Abstract

The present invention relates to a pressure generator comprising a film cushion, two expansion-blocking elements, connected to one another, for the film cushion, and two electrically contactable electrode layers. The invention also relates to an actuator system comprising said pressure generator and a useful actuator.

Description

[0001] Fraunhofer Society...eV

[0002] P149579PC00

[0003] Pressure generator and actuator system containing this pressure generator with a utility actuator

[0004] The present invention relates to a pressure generator with a foil cushion, two interconnected expansion barrier elements for the foil cushion, and two electrically contactable electrode layers. The invention also relates to an actuator system comprising this pressure generator and a utility actuator.

[0005] Actuators play a crucial role in numerous technical fields. Virtually all mechanical processes, such as the movement or deformation of objects, are generated by actuators in technical systems. This includes drives for vehicles, machines, robots, and much more. These drives are currently implemented by motors with various operating mechanisms. Primarily, internal combustion and electric motors are used, converting chemical or electrical energy into mechanical work.

[0006] These motors are typically rigid, hard, and heavy technical systems with a complex design. They consist primarily of heavy metals such as steel and copper. While such long-established drives are robust and capable of generating high forces and high speeds, they exhibit limited mechanical adaptability when in contact with sensitive environments. Robots exemplify this deficiency. Although they play a crucial role in repetitive industrial manufacturing processes, their rigid design limits their suitability for collaboration with humans. In these cases, softer, more flexible, and thus mechanically compliant actuators are often preferred. Another example of the application of soft actuators is the handling of delicate objects such as food (e.g., grasping fruits and vegetables).Soft, deformable (compliant) actuators are also needed in medical procedures on humans, such as surgeries, or in the care of people; these actuators are used, for example, to move grasping tools. The human hand, with its high dexterity due to its fingers with multiple degrees of freedom and its pronounced sensitivity when grasping delicate objects, serves as a model for such soft and deformable actuators.

[0007] In recent decades, numerous new actuators with diverse operating mechanisms have been developed. Various actuator principles utilize the intrinsic capabilities of smart materials to generate movement. This involves converting electrical, magnetic, or thermal energy into mechanical work, which leads to deformation of the material upon electrical, magnetic, or thermal activation. While various smart materials are already used in specialized technical applications, their scope is often severely limited. Piezoelectric materials can generate high actuator forces, but their expansion in an electric field is very small. Shape memory alloys exhibit significantly greater expansion, but the deformation process is very slow, especially during cooling, due to the thermal activation. Furthermore, these materials are hard, such as ceramics and metals.

[0008] Over the past two decades, actuators based on electroactive polymers (EAPs) have attracted considerable attention. By definition, these are polymer materials with lower hardness than ceramics and metals. To date, various types of soft, electrically controlled actuators capable of significant deformation have been realized using different EAP materials. One example is dielectric elastomer actuators (DEAs), which exhibit expansions exceeding 10% but achieve large actuator strokes and simultaneously high forces only with a structure consisting of many elastomer layers. A more recent electrohydraulic operating principle is used in so-called HASEL (Hydraulically Amplified Self-healing Electrostatic) actuators. In this process, electrostatic attraction forces displace a fluid between two polymer films, and a so-called zipping process generates deformation of the actuator.This allows for larger dimensions and higher forces than with the DEA principle, but this actuator principle is also insufficient for many applications.

[0009] Several types of zipping actuators are already known. US Patent 2020 / 0032822 describes an electrohydraulic or hydraulically amplified self-healing electrostatic (HASEL) actuator consisting of a deformable shell with two opposing electrodes on its outer surfaces, the shell being filled with a liquid dielectric. When an electrical voltage is applied, the electrodes attract each other and displace the liquid dielectric between them in a zipping process. This transports the liquid dielectric to a different location within the shell, causing the shell to expand at that location. US Patent 2021 / 0172460 describes a similar electrohydraulic zipping actuator, also consisting of a deformable shell with two opposing electrodes on its outer surfaces, the shell being filled with a liquid dielectric.Furthermore, it is required that the deformation of the actuator occurs in a direction that is orthogonal to the direction of progression of the zipping process.

[0010] US patent 2022 / 0158570 describes further modifications of HASEL actuators, consisting of composites of different layers that vary in their mechanical and electrical properties. The closed structure of HASEL actuators leads to a redistribution of the liquid dielectric, resulting in an expansion of the deformable shell.

[0011] US Patent 2021 / 0316446 describes a dielectric actuator with a cavity filled with a dielectric fluid and a reversibly stretchable membrane. The cavity is bounded by a base plate with an electrode and a flexible membrane with the counter electrode. Applying an electrical voltage between the electrodes results in a zipping process.

[0012] US Patent 2020 / 0112269 describes an electrostatic actuator that performs a bending deformation of two electrodes relative to each other, separated by an insulator. Since one of the electrodes is flexible, applying an electrical voltage between them causes a zipping process, resulting in the electrodes moving closer together. A mobile dielectric is located in the gap between one electrode and the insulator; this dielectric is displaced and shifted during the zipping process.

[0013] Based on this, the object of the present invention was to provide a pressure generator for a novel actuator mechanism, as well as an actuator system comprising this pressure generator and a utility actuator, which enable both large deformations and high actuator forces, thus offering high potential for a wide variety of applications. This object is achieved by the pressure generator with the features of claim 1 and the actuator system with the features of claim 11.

[0014] According to the invention, a pressure generator is provided which has the following components:

[0015] • a foil cushion containing at least one flexible film and a cavity filled with a fluid medium,

[0016] • two interconnected and fixed expansion barrier elements for the foil cushion, whose position and orientation relative to each other cannot be changed during operation, as well as

[0017] • two electrically contactable electrode layers, each arranged on an inner side of the foil cushion facing the cavity or on an outer side of the foil cushion facing an expansion barrier element or on an expansion barrier element for the foil cushion, wherein at least one of the two electrode layers is arranged on the at least one flexible foil and an electrically insulating layer and at least a part of the cavity containing the fluid medium are located between the two electrode layers.

[0018] In the pressure generator according to the invention, the foil cushion can be compressed by applying an electrical voltage between the two electrode layers or between the two electrode layers and a further electrode layer in the areas of the foil cushion covered by electrode layers, and is prevented by the expansion barrier elements from expanding further than the expansion barrier elements allow.

[0019] The compression of the foil cushion by applying an electrical voltage between the electrode layers is a process known as zipping. In this process, the electrode layers attract each other due to electrostatic attraction, starting from the areas where the electrode layers are closest to each other. This reduces the distance between other areas, resulting in increased electrostatic attraction there as well.

[0020] The pressure generator according to the invention allows a hydraulic or pneumatic pressure of more than 1 bar to be easily generated by applying an electrical voltage. This pressure can be precisely adjusted and maintained statically by the applied voltage. A particular advantage is that no conventional motor is required, which is associated with a large footprint, high weight, and potentially disruptive noise.

[0021] In a simple embodiment, the pressure generator according to the invention comprises a foil cushion filled with a fluid medium and two electrode layers. The foil material is generally a polymer and serves as a dielectric. The foil cushion's casing usually consists of flexible polymer films. The dielectric is an electrically insulating layer, which is also referred to as an electrically insulating dielectric layer in the following. Similarly, a dielectric film is also called an electrically insulating dielectric film.

[0022] To further describe the invention, the following two terms are introduced, which relate to the geometric properties of the foil cushion.

[0023] The term "connection zone" describes an edge area of ​​the foil cushion in which two sides of the foil cushion are connected to each other over a flat surface.

[0024] The term "expansion zone" describes the part of the foil pad where the internal distance between the two sides increases from zero in the connection zone to a maximum value determined by the distance between the two expansion-stop elements that prevent further expansion of the foil pad. If the foil pad is not made by joining two separate foils, the expansion zone is the area on the foil pad where the distance between the opposite sides of the foil pad, on which the electrode layers are located, increases from zero at the edge to the maximum value. In known zipping actuators, this can cover the entire surface of the foil pad.In the pressure generators according to the invention, the expansion zone typically occupies only a small part of the area of ​​the foil cushion, since in the preferred case, where the two expansion barrier elements are arranged parallel to each other, the distance between the opposite sides of the foil cushion is also constant over a large part of the area of ​​the foil cushion due to the constant distance between the two expansion barrier elements.

[0025] The following three variants are preferred for the construction of the film cushion: a) the film cushion is formed from two films connected to each other at the edges in a connecting zone, wherein the first film is the flexible film and the second film is a flexible or rigid film, wherein the films are preferably connected to each other by a material bond, in particular by gluing or welding, or by a force bond, in particular by a clamping connection, or b) the film cushion is formed from the flexible film in the form of a bag folded into two partial films at the circumferential edges in a connecting zone, or c) the film cushion is formed from one of the two expansion barrier elements and the flexible film, wherein the flexible film is connected to the expansion barrier element at the edges in a connecting zone.

[0026] Variant a) is particularly preferred, in which the casing is manufactured from two films that are joined or sealed at their edges in the bonding zone, for example by welding or gluing. This bonding zone can, for example, be a sealing seam. Such a two-film casing structure is easy to manufacture. Each film has an electrode layer. The first film is the flexible film, and the second film is either flexible or rigid.

[0027] In variant b), the casing is formed from a single flexible film in the shape of a pouch. This pouch-shaped film has flat electrode layers on two opposite sides. The connecting zone, consisting of two segments of the pouch, surrounds the electrode surfaces. The pouch formed from the film encloses a cavity filled with the fluid medium. This structure is thus similar to that of a film cushion, which consists of two films sealed together at the edges.

[0028] In the embodiment according to variant c), the pressure generator comprises only a flexible film, preferably a polymer film with a constant thickness across its surface, which serves as a dielectric and is located between two rigid plates acting as expansion barriers. These plates are mechanically connected so tightly that their distance from each other does not change during operation of the pressure generator (apart from a slight, unavoidable deflection under pressure). The flexible film is connected to one of the two rigid plates (expansion barrier) at its edge, which encloses a surface, in a bonding zone, for example by welding or bonding. This bonding zone consists of the edge of the film and the portion of the rigid plate (expansion barrier) connected to this edge.On the surface enclosed by the connection zone, the flexible film is completely or partially covered with an electrode layer on the side facing away from the rigid plate (expansion barrier element) connected within the connection zone. The rigid plate is also completely or partially covered with an electrode layer on the side facing the film (inside) within the surface enclosed by the connection zone. Where the film does not directly rest on the rigid plate to which it is connected within the connection zone, a cavity is formed between the film and the rigid plate, filled with a fluid medium. In this case, the flexible film, the rigid plate connected to it, and the fluid medium in the cavity formed within it constitute the film cushion.In a more general embodiment than described previously, the pressure generator comprises two films, the first of which is flexible and the second either flexible or rigid (i.e., stiff). A rigid film can also be referred to as a "plate," but this should not be confused with the previously mentioned rigid plates (expansion barriers) that prevent expansion of the film cushion. Another specific and preferred embodiment arises when the two films are flexible and connected in the bonding zone, each covered on its outer surface by an electrode layer within the bonding zone, and surrounded by two rigid plates as expansion barriers that are mechanically connected so tightly that their distance from each other does not change during operation of the pressure generator.The two flexible films, joined together in the connection zone, with electrode layers on their outer surfaces and a cavity filled with a fluid medium, form the film cushion. Based on a broader design that includes the possibility of one film being rigid and the electrode layers being positioned other than on the outer surfaces of the two flexible films, the following modifications to the pressure generator design are possible, among others:

[0029] One of the two electrode layers is located on the inside of one of the two films. The other electrode layer is located on the outside of the other film. Thus, only one of the two films serves as an electrically insulating dielectric film between the electrode layers.

[0030] The foil cushion is bonded across one side to one of the two rigid plates, acting as an expansion barrier, thus rendering that particular foil inflexible. Here too, one of the two electrode layers can be located on the inside of one of the two flexible foils, and the other electrode layer on the outside of the other foil. If one of the two foils is inflexible, only that foil can be bonded to one of the two rigid plates as an expansion barrier, as otherwise the foil cushion would lose its flexibility.

[0031] The foil cushion, consisting of two flexible films, each with an electrode layer, also contains a third film acting as a dielectric between the two outer flexible films. This third film in the middle can be flexible or rigid. In this modification of the design, the electrode layers on the two outer flexible films can be arranged either on the inside or outside, or one electrode layer on the inside and the other on the outside. Preferably, however, the electrode layers are located on the inner surfaces of the outer flexible films, since the middle film already provides an electrically insulating dielectric layer between the two electrode layers. With only one electrically insulating dielectric layer between the electrode layers, lower voltages can be used than with multiple electrically insulating dielectric layers.

[0032] Referring to the preceding modification, the inner electrically insulating dielectric film can contain a third electrode layer. Preferably, this electrically conductive third electrode layer is covered on both sides by two electrically insulating dielectric layers. In this modification as well, the electrode layers on the two outer flexible films can be arranged either on the inside or outside, or one electrode layer on the inside and the other on the outside. Preferably, in this modification, the inner electrode is set to voltage potential and the two outer electrodes to ground potential during the zipping process.

[0033] The foil cushion, consisting of two flexible films joined or sealed at their perimeter, contains an electrically conductive, semiconducting, or insulating layer in the bonding zone between the two flexible films. The two flexible films again form a cavity filled with a fluid medium. Preferably, the outer surfaces of the two films are covered with electrode layers that extend into the bonding zone (seal seam). When an electrical voltage is applied between the two electrode layers, charge carriers are induced in the intermediate layer by the electrically conductive or semiconducting layer in the bonding zone. An electrically conductive layer in the bonding zone can also be used as a protective electrode, which is connected to ground potential and thus prevents arcing to other electrical devices in the vicinity.An electrically insulating layer in the connection zone increases the minimum distance between the electrode layers to prevent electrical breakdown, because the sealing process can reduce the thickness of the films and thus the distance between the electrode layers. Materials are considered electrically conductive here if they have a specific electrical conductivity of at least 10. 4 exhibiting S / cm. Electrically semiconducting materials are defined here as those that exhibit a specific electrical conductivity between IO and IO. -8 S / cm and 10 4 S / cm. Materials considered electrically insulating here are those with a specific electrical conductivity of at most IO. -8 exhibit S / cm.

[0034] The electrode layers on the inner or outer surfaces of the two flexible films, which are joined at their perimeter, do not cover the flexible films in the bonding zone at all. Instead, they maintain a distance from the bonding zone throughout and thus terminate in the expansion zone of the film cushion, where the distance between the two flexible films increases towards the center of the film cushion. This also increases the minimum distance between the electrode layers to prevent electrical breakdown.

[0035] The electrode layers on the inner or outer surfaces of the two flexible films, which are joined at their perimeter, are spaced from the bonding zone on one part of this edge and extend to or onto the bonding zone on the other part. This allows the zipping process to be controlled as desired by starting where the electrode layers extend to or onto the bonding zone.

[0036] Typically, the thickness of the two films is constant across their surface. In a preferred embodiment, the two films in the connection zone are largely or even completely covered by an electrode layer on the outer surfaces of the film cushion. The two films thus serve as a dielectric between the electrode layers.

[0037] Where the two films do not lie directly on top of each other within the area enclosed by the bonding zone, a cavity is formed between the two films, which is filled with a fluid medium. This fluid medium can be an oil or another liquid, but also a gas such as air. Preferably, it is a liquid with very low electrical conductivity, for example, an oil such as a hydrocarbon oil, a silicone oil, or a vegetable oil.

[0038] In a preferred embodiment of the pressure generator according to the invention, the foil cushion filled with the fluid medium and containing two electrode layers is located between two mechanically rigid, i.e., inflexible, planar elements acting as expansion barriers. These elements are mechanically connected so tightly that their distance from each other does not change during operation of the pressure generator (apart from an unavoidable slight deflection under pressure). Due to this rigid connection, the position and orientation of one rigid element relative to the other do not change. The rigid elements serve to prevent the expansion of the foil cushion during operation of the pressure generator. They represent a variant of the expansion barrier elements. These planar elements are typically rigid, i.e.,inflexible plates, but they can also have a different shape if they fulfill the same function of not deforming under pressure exerted by the foil cushion.

[0039] By "rigid" here, it means that each of the two plates serving as expansion barriers deforms by a maximum of 10 mm during operation of the pressure generator (at a differential pressure of 10 kPa between the two sides of a plate), preferably by a maximum of 1 mm, and particularly preferably by a maximum of 0.1 mm. However, this does not preclude the possibility of adjusting the distance between the two plates for other operating conditions of the pressure generator. Preferably, the two plates have a constant distance from each other across the surface of the electrode layers, i.e., their inner surfaces are aligned parallel to each other. However, the distance between the two plates can also be variable, i.e., the distance between the two plates differs on different surface segments of the plates.For example, the two plates can be arranged at an angle to each other, so that the distance between them changes continuously in one direction. Typically, the two rigid plates acting as expansion barriers are flat, but they can also be curved or have another shape. To prevent the position and orientation of the two rigid plates from changing relative to each other, they must be mechanically connected. This connection is usually achieved by spacers or side walls between the two plates. The side walls then form a housing with the two rigid plates, enclosing the foil cushion. This housing thus acts as a holding device that prevents the foil cushion from expanding during operation.

[0040] The two expansion-stop elements can also be components of a housing made from one or more parts. Here, for example, they represent two opposing walls of the housing. Such a definition of the expansion-stop elements is also expressly included in the present invention.

[0041] The distance between the two outer surfaces of the foil cushion, which encloses the cavity containing the fluid medium, is determined directly or indirectly by the distance between the two rigid plates, except for the circumferential connection zone and an adjacent area within the surface enclosed by the connection zone, such as the expansion zone. Direct contact means that the flexible foils are in direct contact with the surrounding expansion barrier elements. Indirect contact means that another object is located between a flexible foil and one of the expansion barrier elements. This object should also be rigid, i.e., non-deformable, as otherwise it would allow expansion of the foil cushion.

[0042] It follows that the foil cushion, completely filled with the fluid medium, cannot expand beyond the limits defined by the expansion barrier elements. The volume of the foil cushion that can be filled with the fluid medium is limited by the distance between the expansion barrier elements.

[0043] The preceding description refers to the state of the pressure generator in which no electrical voltage is applied between the electrode layers. The foil cushion consists of two flexible films, each covered with an electrode layer, with the fluid medium located between them. The two flexible films contact a rigid plate directly or indirectly, acting as expansion barriers. "Directly" here means that they make full contact with the rigid plate, while "indirectly" refers to contact with an intervening body. For the foil cushion to make full contact with the expansion barriers, it must be sufficiently filled with the fluid medium. Preferably, in the state without applied electrical voltage, the foil cushion between the two expansion barriers is filled with the fluid medium to the extent permitted by the distance between the two expansion barriers.

[0044] The surface area of ​​the electrode layers can differ from that of the expansion zone of the foil pad. It may not cover the expansion zone at all, may partially cover the expansion zone, or may completely cover the expansion zone.

[0045] If the expansion zone is completely covered by the surface of the electrode layers, it can also extend into the connection zone. When an electrical voltage is applied between the two electrode layers on the flexible films, the electrode layers attract each other electrostatically. The attractive force is strongest where the distance between the two electrode layers is smallest. This is the case in the connection zone if the electrode layers extend into the connection zone, or in the expansion zone adjacent to the connection zone if the electrode layers only extend into the expansion zone. Starting from the points with the smallest distance between the electrode layers, the two flexible films with the electrode layers contract.This reduces the distance between the electrode layers in other surface segments as well, causing the electrode layers to attract each other electrostatically more strongly there too. The contraction of the flexible films eventually spreads across the entire electrode surface, unless a counter-pressure creates a pressure equilibrium. The successive contraction of the flexible films displaces the fluid medium between them. This so-called zipping process is already known. Such an actuator is called a zipping actuator. However, a zipping actuator with two expansion-stop elements on either side, which prevent the expansion of the film cushion beyond the space defined by the expansion-stop elements and thus enable the generation of higher pressures, is not yet known.

[0046] Without the two expansion-stop elements, the fluid medium displaced at one point on the electrode surface by the zipping process can force the two flexible films apart at another point, thus counteracting the zipping process. This is the case with known zipping actuators. In the pressure generator according to the invention, such expansion is prevented by the two expansion-stop elements.

[0047] The inclusion of the two expansion stop elements is a crucial prerequisite for generating high pressures.

[0048] The cavity enclosed by the two films can either be sealed to the outside or have a connection to the outside, for example, through an outlet opening in a seal seam in the connection zone. This results in different embodiments of the pressure generator. In the first case, the pressure generator operates solely as an actuator capable of performing mechanical work. In the second case, the pressure generator is connected to an external actuator to form an actuator system in which the actuator performs the mechanical work.

[0049] In one embodiment of the pressure generator, the foil cushion has no outlet opening through which the fluid medium is forced out. Instead, a usually smaller portion of the foil cushion is not located between the two expansion-stop elements and can therefore expand and generate outward pressure. Preferably, in this embodiment of the pressure generator, the electrode layers do not extend over the entire surface of the foil cushion. Only the generally larger portion of the foil cushion, located between the two expansion-stop elements and whose expansion during the zipping process is thus blocked, has electrode layers.

[0050] In another embodiment of the pressure generator, the foil cushion has an outlet opening through which, during the zipping process, the fluid medium is increasingly forced out of the cavity between the two flexible films as the electrical voltage increases. This process can continue until the fluid medium is almost completely or even completely displaced from the cavity between the two flexible films. When the fluid medium is completely displaced, the cavity between the two flexible films disappears. Even during this process, the foil cushion between the two expansion-stop elements cannot expand. This distinguishes the pressure generator according to the invention from other zipping actuators, in which the flexible films can bulge further outwards due to the lack of mechanical resistance.

[0051] When the electrical voltage between the electrode layers is reduced or switched off, the fluid medium displaced from an open foil cushion between the two expansion barrier elements is transported back into the foil cushion by a suitable mechanism. Preferably, the fluid medium returns elastically to the receiving volume into which it was previously forced. This elastic return generates a counter-pressure that is in equilibrium with the pressure generated by the pressure generator. Alternatively, a counter-pressure can be generated by another passive mechanism, such as a force of gravity, which transports the fluid medium back into the foil cushion as soon as the electrical voltage is reduced or switched off.

[0052] When the electrical voltage is switched off, the foil cushion deforms back into its original shape due to the counter-pressure. This occurs as the returning fluid medium forces the flexible films apart to the extent permitted by the distance between the two expansion-stop elements. This state is a preferred initial state for the pressure generator, from which pressure generation begins by applying an electrical voltage between the electrode layers. Alternatively, the pressure generator can be permanently under counter-pressure, which must first be overcome by applying a minimum electrical voltage. This ensures that when the voltage is switched off, the fluid medium is forced back into the pressure generator or into the area between the two expansion-stop elements.Even with an open pressure generator, the return of the fluid medium by means of a counter-pressure is advantageous, for example by a weight force acting on the receiving volume into which the fluid medium was previously pressed.

[0053] Another way to return the fluid medium is through a further zipping process. This can be achieved in the following ways: If the foil cushion is connected to one of the two expansion barrier elements across its entire surface, the inside of the other (opposite) expansion barrier element has an additional electrode layer, separated from the nearest electrode layer on the foil cushion by an electrically insulating dielectric layer. By applying an electrical voltage between the electrode layer on the expansion barrier element and the nearest electrode layer on the foil cushion, the flexible foil of the foil cushion, connected to the second electrode layer, is drawn towards the expansion barrier element, thereby drawing the fluid medium previously displaced from the foil cushion back into it.

[0054] If the foil cushion is not in full contact with either of the two expansion barrier elements, each of the inner surfaces of both expansion barrier elements has an additional electrode layer, separated from the nearest electrode layer on the foil cushion by an electrically insulating dielectric layer. Applying an electrical voltage between an electrode layer on one expansion barrier element and the nearest electrode layer on the foil cushion draws the foil cushion towards both expansion barrier elements, thereby drawing the fluid medium previously displaced from the foil cushion back into it.

[0055] The two expansion-stop elements in the pressure generator prevent the foil cushion from expanding during the zipping process, allowing the pressure generator to produce higher pressures than other zipping actuators. The achievable pressure depends on the distance between the electrode layers and the thickness of the flexible, electrically insulating dielectric films, with the distance between the electrode layers being determined by the distance between the two expansion-stop elements. A theoretical estimate indicates that with a distance of 0.3 mm between the expansion-stop elements, a pressure of more than 1 bar or more than 100 kPa can be generated. This high pressure is due to the high energy density resulting from a small electrode distance. The generated pressure can be precisely and continuously adjusted via the electrical voltage applied between the electrode layers.This is a static pressure that can be increased or decreased by changing the applied voltage.

[0056] A simple embodiment of the two expansion barrier elements consists of both being rectangular and planar rigid plates of the same length and width, arranged parallel to each other, and overlapping completely. However, it is also possible for the two plates to be non-rectangular, for at least one rigid plate to have a curvature, for one plate to have a larger area than the other, for the two plates not to be parallel to each other, or for them not to overlap completely. For example, one plate could have an opening through which a closed foil cushion could expand outwards.

[0057] In the case of two rectangular, planar, rigid plates serving as expansion barrier elements with the same area and a constant distance between them, between which the foil cushion is located, the length and width of the plates are preferably at least 10 times greater than the distance between the plates, particularly preferably 30 times greater, and most preferably 100 times greater. In the case of two differently shaped plates with a constant or non-constant distance between them, between which the foil cushion is located, the square root of the smaller inner area of ​​the two plates is preferably at least 10 times greater than the distance averaged over the smaller inner area, particularly preferably 30 times greater, and most preferably 100 times greater.

[0058] A further advantage of the pressure generator according to the invention is that, unlike other zipping actuators, the flexible films only need to bend very slightly during the zipping process, as the expansion-stop elements prevent them from bending more sharply. This significantly reduces the mechanical resistance during bending, thus requiring less energy to bend the flexible films and further increasing the achievable pressure of the pressure generator. Another advantage arises from the fact that a material with a higher modulus of elasticity can be selected for the flexible films, resulting in higher dielectric strength. This allows either the zipping actuator to be operated at a higher electrical voltage for the same film thickness, or the film thickness to be reduced for the same voltage. Both of these options lead to the generation of higher pressure by the pressure generator.

[0059] The pressure generator according to the invention, with a closed foil cushion, can be used not only to generate high pressures but also as an actuator. For this purpose, the foil cushion, whose expansion is prevented between the expansion-stop elements, expands only in the area not located between the two expansion-stop elements. If the flexible films of the foil cushion are non-expandable, the action, in the form of expansion of the pressure generator, is limited. However, this pressure generator can generate very high pressures and forces.

[0060] The following section reveals some special and preferred designs of the pressure generator that differ from the designs presented so far.

[0061] All these modifications of the foil cushion result in corresponding designs of the pressure generator in which the foil cushion is arranged between two expansion barrier elements, preferably rigid plates, whose distance to each other is fixed.

[0062] Preferably, films with a thickness of no more than 500 pm are used to construct the foil cushion, with thicknesses in the range of 0.1 pm to 200 pm being particularly preferred, and in the range of 1 pm to 100 pm being most preferred. A small thickness means that particularly high electrical voltages do not need to be applied between the electrode layers to achieve the desired electric field strength. Possible materials for the flexible or non-flexible films used as electrically insulating dielectric films in the pressure generator include polymers such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), thermoplastic polyurethane (TPU), and polyvinylidene fluoride (PVDF), as well as copolymers of various polymers. In addition to organic polymers, inorganic and organo-inorganic polymers (ORMOCER®e) and elastomers are also possible.Polymers with a high electrical breakdown field strength and / or a high dielectric permittivity are preferred. The flexible or inflexible films can also consist of polymers containing particles or fibers.

[0063] Other possible materials for the non-flexible films used as electrically insulating dielectric films in the pressure generator include all electrically non-conductive inorganic materials such as silicon dioxide, aluminum oxide, zirconium oxide, and various glasses. Materials with a high electrical breakdown field strength and / or a high dielectric permittivity, such as barium titanate or lead zirconate titanate, are preferred.

[0064] Whenever electrode layers are mentioned in the entire description of the invention, if the electrode layer is arranged on a flexible film, it is preferably also a flexible electrode layer. If the electrode layer is arranged on a non-flexible film, the electrode layer can also be rigid or inflexible.

[0065] Possible materials for the electrode layers on flexible, electrically insulating dielectric films include carbon particles such as carbon black, graphite, graphene, or carbon nanotubes, or metal particles in concentrated form, in a polymer matrix, or as a gel, as well as layers of poly-3,4-ethylenedioxythiophene (PEDOT) or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS). Another option is a thin metal layer, which can be applied to the flexible film, for example, by a sputtering process. Further methods for producing the electrode layers include electroplating of a metal such as copper or vapor deposition using metal atoms such as copper, silver, or gold. The same materials can be used for electrode layers on non-flexible films, but these layers can be thicker.Because flexibility is not required, rigid metal layers or metal plates can also be used as electrode layers here.

[0066] The fluid medium in the pressure generator can, in principle, be any liquid, such as an oil (mineral oil, synthetic oil, vegetable oil, silicone oil, etc.) or a mixture of different liquids. The mixture can be either homogeneous or an emulsion. It is also possible for the liquid to contain particles, for example, to influence its dielectric properties; in this case, it is a suspension. Furthermore, the fluid medium can also be a gas, such as air or nitrogen, or a combination of separate phases of a liquid and a gas. A particularly advantageous combination is a small volume of a liquid, preferably an oil, in the zipping gap of the pressure generator and a larger volume of a gas (at normal pressure), which is pressurized and compressed by the zipping process.

[0067] The expansion stop elements should be as rigid as possible, i.e., they should deform as little as possible under mechanical stress. To this end, they should preferably possess at least one of the following properties:

[0068] • a thickness in the range of 0.1 mm to 100 mm, particularly preferably in the range of 0.3 mm to 30 mm, most preferably in the range of 1 mm to 10 mm,

[0069] • has a modulus of elasticity, measured according to DIN EN ISO 178 (bending test), of at least 0.1 GPa, particularly preferably in the range of 0.5 GPa to 5000 GPa, most preferably in the range of 1 GPa to 2000 GPa,

[0070] • a bending stiffness of at least 0.1 N mm 2 , particularly preferably in the range of 1 N mm 2 up to 10 kN mm 2 , especially preferred in the range of 10 N mm 2 up to 5 kN mm 2, measured according to DIN 53350. Possible materials for the expansion barrier elements as a component of the pressure generator are all materials with a reasonably high modulus of elasticity. The higher the modulus of elasticity of the rigid plate, the thinner the rigid plate can be while still maintaining sufficient stiffness.

[0071] Preferred materials for the expansion barrier elements are various plastics due to their low density and good processability, in particular selected from the group consisting of

[0072] • Thermoplastics, in particular polyethylene (PE), polypropylene (PP), polystyrene (PS), polyamides (PA), acrylonitrile butadiene styrene (ABS), polylactide (PLA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK) and polyvinyl chloride (PVC),

[0073] • Thermosets, especially acrylates, epoxides, polyesters, vinyl esters,

[0074] • Metals, especially steel,

[0075] • Glass, ceramics or glass-ceramics,

[0076] • Concrete or reinforced concrete or

[0077] • Combinations thereof, which may also be reinforced, especially with fibers, particles or fiber mats.

[0078] It is particularly preferred if materials suitable for 3D printing are used.

[0079] In the pressure generator, the inner surfaces of the two expansion barrier elements, between which the foil cushion is located, should have a small gap in the surface segments between which the foil cushion is arranged, if high pressure is to be generated with the pressure generator. A maximum gap of 30 mm is preferred, 10 mm is particularly preferred, and a gap in the range of 0.01 pm to 3 mm is most preferred.

[0080] Preferably, the inner surfaces of the two expansion-barrier elements, between which the foil cushion is located, are aligned parallel to each other. A constant thickness of the flexible and / or inflexible films in the foil cushion is also preferred. As mentioned previously, it is also preferred that the distance between the inner surfaces of the two expansion-barrier elements is significantly smaller than the surface dimensions of the expansion-barrier elements, such as length and width. This results in the distance between the electrode layers in the foil cushion being constant over most of the electrode area even in the state without applied voltage, since the electrode layers are aligned parallel to the inner surfaces of the expansion-barrier elements. After the zipping process has been completed under high applied voltage, the distance between the electrode layers is again constant, only significantly smaller, because the fluid medium between them has been displaced.This arrangement is a preferred embodiment of the pressure generator and differs significantly from the known zipping actuators, in which, at least in the state without electrical voltage, the electrode layers largely do not have a constant distance from each other.

[0081] Relatively high electrical voltages are required to electrically control the foil cushion in the pressure generator. A high-voltage source, which is electrically connected to the electrode layers in the pressure generator, is necessary to generate these voltages. It is particularly advantageous to combine the pressure generator and the high-voltage source into a single unit. This eliminates the need for high-voltage lines between different components of the actuator system, as the high voltage is only required within this unit. This compact design facilitates compliance with safety requirements.

[0082] The present invention also relates to an actuator system with which mechanical work can be performed in conjunction with a large actuation deformation. For this purpose, the pressure generator according to the invention is extended by an object that can be deformed by pressure, which is referred to in the present description of the invention as the "utility actuator". The pressure generator according to the invention can be modularly connected to the utility actuator to form an actuator system. With such actuator systems, different types of actuation, such as changes in length, thickness, volume, and bending deformations, can be generated and continuously controlled.

[0083] In one embodiment of the invention, the actuator is connected to the pressure generator in such a way that the fluid medium contained in the pressure generator is forced through an outlet opening in the foil cushion to the actuator by the pressure generated by the applied electrical voltage, thereby deforming the actuator. For this purpose, the actuator can be connected to the outlet opening in the foil cushion via a channel or directly to the outlet opening in the foil cushion. Alternatively, the actuator can also be a part of the foil cushion in which expansion is not restricted by the expansion-stop elements.

[0084] Examples of deformation of the actuator include lengthening or shortening, thickening, tapering, or bending, or even volume expansion, as in a balloon. Pneumatic actuators with a cylindrical shape, such as the McKibben muscle, which contracts lengthwise and thickens in diameter under air pressure, are already known. Pneumatic gripping fingers that bend under air pressure are also state of the art. Such pneumatic actuators are operated with an air compressor, which is quite complex. The actuator system with the pressure generator according to the invention offers a relatively compact alternative.

[0085] Preferably, the actuator system according to the invention includes a utility actuator that deforms elastically under pressure. When the pressure applied to the utility actuator increases, the deformation increases, for example, accompanied by an increase in the volume of the utility actuator, which contains the same fluid medium as the pressure generator. When the pressure applied to the utility actuator decreases, the deformation decreases again due to the elastic return of the utility actuator, accompanied by a decrease in the utility actuator volume. While increasing the pressure causes fluid medium to be displaced from the pressure generator towards the utility actuator, decreasing the pressure causes the opposite. Preferably, the utility actuator in the actuator system according to the invention is made of soft elastic materials, for example, elastomers. A possible model for a utility actuator is an elastically deformable bending actuator that bends under increasing pressure similarly to a human finger.

[0086] Many of the embodiments of the pressure generator according to the invention, which have been described above, can be combined with virtually any embodiment of a utility actuator. This achieves a high degree of modularity for the actuator system according to the invention.

[0087] Preferred materials for the actuator are elastomers such as silicones, thermoplastic polyurethanes (TPU), other thermoplastic elastomers, and natural rubber. A hollow body filled with a fluid medium is constructed from such materials. When the pressure generator forces the fluid medium into the actuator, the actuator deforms elastically and, upon reduction of the pressure exerted by the pressure generator, forces the fluid medium back towards the pressure generator. However, the actuator can also contain non-elastically deformable materials such as plastics, metals, ceramics, and glass. Components made from such non-elastically deformable materials can be used to influence the deformation of the actuator in a desired manner.

[0088] The planar shape of the pressure generator, parallel to the two expansion barriers with an outlet opening of the foil cushion, can be rectangular. However, a more fluid-efficient shape is advantageous for forcing the fluid medium out of the foil cushion. A shape is preferred in which the planar shape of the foil cushion tapers towards its outlet opening. This can be achieved by a rounded shape or a funnel-shaped contour of the foil cushion's surface parallel to the two expansion barriers on the side where the foil cushion's outlet opening is located.

[0089] A valve can be located between the pressure generator and the actuator to block the backflow of the fluid medium between them. This ensures that the deformation of the actuator caused by applying an electrical voltage between the electrode layers in the pressure generator is maintained even when the voltage is switched off. In this way, energy can be saved by maintaining the actuator's deformation. When the valve opens, the actuator's elastic return to its original shape upon pressure release. Preferred embodiments of the valve between the pressure generator and actuator utilize a smart material that deforms in response to an electrical voltage, a magnetic field, or temperature changes such as heating and cooling.Deformation allows a connecting channel between the pressure generator and the actuator to be opened and closed. Examples of electrically controllable smart materials include electroactive polymers, both electronic and ionic electroactive polymers, preferably electrostatic zipping actuators, dielectric elastomers, and conductive polymers. Other examples of electrically controllable smart materials are piezoelectric ceramics and polymers. Magnetically controllable smart materials include magnetorheological elastomers, magnetic shape memory alloys, and magnetostrictive materials. Examples of thermally controllable smart materials are thermal shape memory alloys and shape memory polymers. Thermally controllable bimetallic strips can also be used for the valve.

[0090] Furthermore, the actuator system according to the invention can include a media separation barrier. The media separation barrier is preferably located in a connecting channel between the pressure generator and the actuator. The function of the media separation barrier is to allow the pressure generator and the actuator to be filled and operated with different fluid media. For example, the pressure generator can be operated with oil as the primary fluid medium, and the actuator with water, an aqueous solution such as isotonic saline solution, or air as the secondary fluid medium. In this way, undesirable environmental contamination can be avoided in the event of a leak in the actuator. The media separation barrier can, for example, be a piston in the connecting channel between the pressure generator and the actuator. The piston separates the two fluid media and is displaced by a pressure difference between the two sides.When the electrical voltage, and thus the pressure on the first fluid medium, is increased in the pressure generator, the piston moves towards the actuator, forcing the second fluid medium into the actuator and deflecting it further. Conversely, when the electrical voltage, and thus the pressure on the first fluid medium (TI), is decreased in the pressure generator, the piston moves towards the actuator due to the restoring force of the actuator and the return flow of the second fluid medium, forcing the first fluid medium back into the pressure generator. The media separation barrier can also be a flexible or even elastically stretchable membrane that separates the two fluid media and is moved or stretched in one direction or the other by pressure changes, analogous to the piston mentioned above. It is also possible to use two fluid media that are immiscible.The immiscibility of the two fluid media has the same effect as a separate media separation barrier.

[0091] The connecting channel between the pressure generator and the actuator should expand as little as possible under the pressure of the fluid medium within it, thus minimizing the amount of additional fluid required for expansion. In many cases, it is advantageous for the connecting channel to be flat and wide at the point of connection to the pressure generator, thereby matching the cross-sectional area of ​​the foil cushion. Conversely, at the connection to the actuator at the other end, the connecting channel should preferably transition smoothly into a cross-sectional shape adapted to the actuator, such as a circle, to minimize flow resistance during fluid transport.

[0092] The fluid medium in the actuator, like the fluid medium in the pressure generator, can in principle be any liquid, such as an oil (mineral oil, synthetic oil, vegetable oil, silicone oil, etc.) or a mixture of different liquids. The mixture can be either homogeneous or an emulsion. It is also possible for the liquid to contain particles, meaning it is a suspension. Furthermore, the fluid medium can be a gas, such as air or nitrogen, or a combination of separate phases of a liquid and a gas. In many cases, the pressure generator and the actuator contain the same fluid medium. However, if there is a separation in the connecting channel between the pressure generator and the actuator, two different fluid media can be used.

[0093] Another advantageous embodiment of the actuator system, consisting of a pressure generator and a functional actuator, involves integrating a sensor that detects the deformation of the foil cushion during the zipping process. One possibility for this is to measure the electrical capacitance between the electrode layers of the foil cushion when an electrical voltage is applied between these same electrode layers. As the zipping process progresses, an increasing proportion of the electrode layer's surface area approaches each other, thereby increasing the electrical capacitance.

[0094] Another way to implement a sensor is to attach an additional electrode layer to the inside of at least one expansion barrier element. This additional electrode layer is separated from the nearest electrode layer of the foil cushion by an electrically insulating dielectric layer. The electrical capacitance is measured between these two electrode layers. As the zipping process progresses, the electrode layer of the foil cushion is attracted to the counter electrode layer of the foil cushion and thus moves away from the additional electrode layer on the expansion barrier element, causing the measured capacitance to decrease. Such a capacitance measurement can also be performed between the other electrode layer of the foil cushion and an additional electrode layer on the other expansion barrier element, with an electrically insulating dielectric layer in between.

[0095] The pressure generator and actuator system according to the invention can be used for a variety of actuator applications. These include, for example, lifting devices, robot grippers, seat adjustments, massage devices, surgical instruments, haptic feedback, positioning devices, battery tensioning and compression, valves, pumps, human-machine interfaces, buttons on demand, bumpers on demand, seat firmness adjustment, electromechanical elements for games, exoskeletons, prostheses, orthoses, and wearable controllable aids such as gloves.A particular advantage of the actuator system with the separation of the pressure generator and the power actuator is that the power actuator can be made very lightweight, for example, by manufacturing it entirely or largely from an elastomer, thus also allowing for elastic return of the fluid medium to the pressure generator. The pressure generator with its rigid expansion-stop elements and the high-voltage supply can be positioned separately at a suitable location.

[0096] Examples

[0097] The following figures and examples are intended to illustrate and explain the subject matter of the invention in more detail, without limiting it to the specific embodiments shown here.

[0098] The following describes some exemplary embodiments of the invention. These first relate to the pressure generator in various embodiments as the central component of the invention. Subsequently, examples of utility actuators are shown, which, considered individually, are not part of the invention but serve only to illustrate possible actuator applications of the pressure generator. Finally, examples of actuator systems as combinations of pressure generator and utility actuator are presented, which are again part of the invention.

[0099] The figures are not drawn to scale. In particular, the distances between the two expansion barrier elements (rigid plates) are shown relatively large in relation to their surface dimensions, such as length and width, for clarity. Smaller distances between the two expansion barrier elements are generally preferred in order to generate a higher pressure with the pressure generator.

[0100] Figure 1 shows a side view of a non-inventive zipping actuator (1) in the form of a foil cushion filled with a fluid medium (6), consisting of two flexible films (2, 2') with a sealing seam (3), and with two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5'). The electrode layers (4, 4') on the top and bottom of the foil cushion each cover only the left part of the foil cushion. When an electrical voltage is applied and increased between the electrode layers (4, 4'), the upper and lower films (2, 2') zip together increasingly from left to right and displace the fluid medium (6) into the right part of the foil cushion. As a result, this part to the right of the zipping zone expands increasingly upwards and downwards. Figure 1A shows the zipping actuator without an applied voltage, Figure 1B with an electrical voltage and Figure 1C with a higher electrical voltage.

[0101] Figure 2A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9'). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. Figure 2B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when an electrical voltage is applied. This zipping process shifts the expansion zone (10) towards the center of the pressure generator (7).Unlike prior art zipping actuators, the expansion of the foil cushion on the area enclosed by the zipping zone between the two expansion-stop elements (8, 8') is prevented. Only on the right side does the foil cushion expand upwards at the point where the upper of the two expansion-stop elements (8) is interrupted. This expansion lifts a support weight (11). Figure 2C shows the further contraction of the foil cushion between the two expansion-stop elements (8, 8') when a higher electrical voltage is applied than before. Only on the right side does the foil cushion continue to expand upwards at the point where the upper of the two expansion-stop elements (8) is interrupted, further lifting the support weight (11). Figure 2D shows a top view of the pressure generator (7) according to the invention. In this illustration, the upper expansion-stop element (8) has been removed.Figure 3A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9'). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. Figure 3B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when an electrical voltage is applied. This zipping process shifts the expansion zone (10) towards the center of the pressure generator (7).Unlike prior art zipping actuators, the expansion of the foil cushion on the area enclosed by the zipping zone between the two expansion-stop elements (8, 8') is prevented. The foil cushion expands upwards only in the center, at the point where the upper of the two expansion-stop elements (8) is interrupted. This expansion lifts a support weight (11). Figure 3C shows the further contraction of the foil cushion between the two expansion-stop elements (8, 8') when a higher electrical voltage is applied. The foil cushion expands further upwards only in the center, at the point where the upper of the two expansion-stop elements (8) is interrupted, and lifts the support weight (11) further. Figures 3D and 3E show the pressure generator (7) according to the invention in a top view in two versions: one with a rectangular base and the other with a circular base.In the illustration, the upper expansion stop element (8) has been removed.

[0102] Figure 4A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is attached over its entire surface to the lower expansion-stop element (8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. Figure 4B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when an electrical voltage is applied.This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). A portion of the fluid medium (6) is forced out of the foil cushion here. Figure 4C shows the further contraction of the foil cushion between the two expansion-stop elements (8, 8') when a higher electrical voltage is applied than before. Here, all of the fluid medium (6) is forced out of the foil cushion. Figure 4D shows a top view of the pressure generator (7) according to the invention with a rectangular base. In this illustration, the upper expansion-stop element (8) has been removed.

[0103] Figure 5A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and featuring a sealing seam (3), as well as two electrode layers (4, 4') and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). In contrast to Figure 4A, the foil cushion here is formed by a foil (2) on the upper side and the lower expansion-stop element (8') on the lower side, which are connected to each other at the circumferential edge of the foil cushion. The upper electrode layer (4) is located on the upper side of the foil (2) and the lower electrode layer (4') on the upper side of the lower expansion-stop element (8'). An expansion zone (10) begins at the sealing seam (3), in which the distance between the flexible foil (2) and the expansion-stop element (8') changes.On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. Figure 5B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when a high electrical voltage is applied. This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). All of the fluid medium (6) is forced out of the foil cushion in this case.Figure 6A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is not attached over its entire surface to either of the two expansion-stop elements (8, 8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. Figure 6B shows the contraction of the foil cushion between the two expansion barrier elements (8, 8') when an electrical voltage is applied.This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). A portion of the fluid medium (6) is forced out of the foil cushion here. Figure 6C shows the further contraction of the foil cushion between the two expansion-stop elements (8, 8') when a higher electrical voltage is applied than before. Here, all of the fluid medium (6) is forced out of the foil cushion. Figure 6D shows the pressure generator (7) according to the invention in a top view with a rectangular base. In this illustration, the upper expansion-stop element (8) has been removed.

[0104] Figure 7A shows another pressure generator (7) according to the invention, as in Figure 6D, with a rectangular foil cushion in a top view (the upper expansion stop element (8) has been removed in the illustration) for comparison with the following embodiments. Figure 7B also shows a pressure generator (7) according to the invention with a foil cushion in a top view (the upper expansion stop element (8) has been removed in the illustration). In contrast to Figure 7A, the foil cushion here has a rounded shape on the right side towards the outlet opening (12). Figure 7C also shows a pressure generator (7) according to the invention with a foil cushion in a top view (the upper expansion stop element (8) has been removed in the illustration). In contrast to Figure 7A, the foil cushion here, as well as the two expansion stop elements (8, 8'), have a progressive narrowing on the right side towards the outlet opening (12).

[0105] Figure 8A shows a pressure generator (7) according to the invention as shown in Figure 7A with a foil cushion in a top view (the upper expansion barrier element (8) has been removed in the illustration). In contrast to Figure 7A, the electrode layers (4, 4' (not visible)) extend only on the left side to the sealing seam (3) and are spaced from the sealing seam (3) on the other sides, i.e., they do not completely cover the expansion zone (10). Figure 8B shows a pressure generator (7) according to the invention as shown in Figure 7B with a foil cushion in a top view (the upper expansion barrier element (8) has been removed in the illustration). In contrast to Figure 7B, the electrode layers (4, 4' (not visible)) extend only on the left side to the sealing seam (3) and are spaced from the sealing seam (3) on the other sides, i.e., they do not completely cover the expansion zone (10).Figure 8C shows a pressure generator (7) according to the invention as shown in Figure 7C with a foil cushion in a top view (the upper expansion barrier element (8) has been removed in the illustration). In contrast to Figure 7C, the electrode layers (4, 4' (not visible)) extend only on the left side to the sealing seam (3) and are spaced from the sealing seam (3) on the other sides, i.e., they do not completely cover the expansion zone (10). In modified versions of the pressure generator (7) according to the invention as shown in Figures 8A, 8B and 8C, the electrode layers (4, 4') also do not extend to the sealing seam (3) on the left side (not shown).

[0106] Figure 9 shows a pressure generator (7) according to the invention as in Figure 8A with a foil cushion in a top view (the upper expansion barrier element (8) is removed in the illustration). In contrast to Figure 8A, the electrode layers (4, 4' (not visible)) are divided along the long side in the middle. This directs the zipping process more strongly from left to right towards the outlet opening (12) of the foil cushion.

[0107] Figure 10 shows a pressure generator (7) according to the invention with a foil cushion in a top view (the upper expansion barrier element (8) has been removed in the illustration). In contrast to the preceding figures, the outlet opening (12) of the foil cushion is arranged on the long side of the foil cushion. On the right side, the electrode layers (4, 4' (not visible)) do not extend completely onto the expansion zone (10). In this way, the zipping process is directed towards the lower long side of the foil cushion and thus towards the outlet opening (12).

[0108] Figure 11 shows a pressure generator (7) according to the invention with a foil cushion in a top view (the upper expansion stop element (8) has been removed in the illustration). In contrast to the preceding figures, the foil cushion consists of two segments (top and bottom in Figure 11), each with two electrode layers (4, 4' (not visible)) and each with a wide outlet opening (12', 12") in the middle of the foil cushion along the long side. The two wide outlet openings (12', 12") open into a common channel with a narrow outlet opening (12) on the right side of the foil cushion.

[0109] Figure 12A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the inner surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. In contrast to Figure 6, the electrode layers (4, 4') are located here on the inner surfaces of the foil cushion, which is also divided into an upper and a lower part by a rigid intermediate film (13). The foil cushion is not attached over its entire surface to either of the two expansion-stop elements (8, 8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be pushed out.Figure 12B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when a high electrical voltage is applied. This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). The entire fluid medium (6) is forced out of the foil cushion.

[0110] Figure 13A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the inner sides of the foil cushion and electrode leads (5, 5') between two expansion barrier elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. In contrast to Figure 6, the electrode layers (4, 4') are located here on the inner sides of the foil cushion, which is further divided into an upper and a lower part by a three-layer intermediate film. The intermediate film consists of two flexible electrically insulating dielectric layers (14, 14') and a conductive electrode layer (4") in between with an electrode lead (5").The foil cushion is not attached to either of the two expansion-stop elements (8, 8') across its entire surface. On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. The electrical voltage is applied between the middle electrode layer (4") and the two outer electrode layers (4, 4'), which are connected to ground potential. Figure 13B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when a high electrical voltage is applied. This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). All of the fluid medium (6) is forced out of the foil cushion in this area.

[0111] Figure 14A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). The distance between the expansion-stop elements (8, 8') decreases from left to right. An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is not attached over its entire surface to either of the two expansion-stop elements (8, 8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out.Figure 14B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when a high electrical voltage is applied. This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). The entire fluid medium

[0112] (6) is pushed out of the foil cushion here. In a modified version of the pressure generator (7) according to the invention as shown in Figures 14A and 14B, the distance between the expansion barrier elements (8, 8') increases from left to right (not shown).

[0113] Figure 15A shows a side view of a pressure generator according to the invention.

[0114] (7) with a foil cushion filled with a fluid medium (6) consisting of two flexible films (2, 2') with a sealing seam (3) and with two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion barrier elements (8, 8') with spacers (9, 9' (not visible)). The foil cushion contains an electrically conductive layer (15) in the circumferential sealing seam (3) between the interconnected film edges. An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is not attached over its entire surface to either of the two expansion barrier elements (8, 8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be expelled. Figure 15B shows an enlarged section of the left side of Figure 15A.Figure 15C shows, in this detail, the contraction of the foil cushion between the two expansion-stop elements (8, 8') when an electrical voltage is applied. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). In a modified version of the pressure generator (7) according to the invention, as shown in Figures 15A, 15B, and 15C, the foil cushion contains an electrically semiconducting layer (15) in the circumferential sealing seam (3) between the interconnected foil edges. In a further modified version of the pressure generator (7) according to the invention, as shown in Figures 15A, 15B, and 15C, the foil cushion contains an electrically insulating layer (15) in the circumferential sealing seam (3) between the interconnected foil edges.

[0115] Figure 16A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is not attached over its entire surface to either of the two expansion-stop elements (8, 8'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. The electrode layers (4, 4') do not completely cover the expansion zone (10) and are spaced away from the circumferential sealing seam (3) where the film edges are joined together.Figure 16B shows an enlarged section of the left side of Figure 16A. Figure 16C shows, in this section, the contraction of the foil cushion between the two expansion-stop elements (8, 8') when an electrical voltage is applied. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8').

[0116] The distance between the electrode layers (4, 4') and the circumferential sealing seam (3) can be the same everywhere or different at different points.

[0117] Figure 17A shows a side view of a pressure generator (7) according to the invention, comprising two foil cushions filled with a fluid medium (6), each consisting of two flexible films (2, 2') with a sealing seam (3), and each with two electrode layers (4, 4') on the outer surfaces of the foil cushions and electrode leads (5, 5') between three expansion-stop elements (8, 8', 8") with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3) in which the distance between the two flexible films (2, 2') changes. The foil cushions are not attached over their entire surface to any of the three expansion-stop elements (8, 8', 8"). On the right side, each foil cushion has an opening through which the fluid medium (6) can be forced out. The two openings lead into a common channel, which can convey the fluid medium from both foil cushions through an outlet opening (12).Figure 17B shows the contraction of the two foil cushions between the three expansion-stop elements (8, 8', 8") when a high electrical voltage is applied. This zipping process shifts the expansion zones (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushions to the right of the zipping zones is prevented between the three expansion-stop elements (8, 8', 8"). The entire fluid medium (6) is forced out of the two foil cushions.

[0118] Figure 18A shows a side view of a pressure generator (7) according to the invention, comprising two foil cushions filled with a fluid medium (6), each consisting of two flexible films (2, 2') with a sealing seam (3), and each with two electrode layers (4, 4') on the outer surfaces of the foil cushions and electrode leads (5, 5') between three expansion-stop elements (8, 8', 8") with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3) in each cushion, where the distance between the two flexible films (2, 2') changes. The foil cushions are not attached to any of the three expansion-stop elements (8, 8', 8") over their entire surface. On the right side, each foil cushion has an outlet opening (12) through which the fluid medium (6) can be forced out. The two outlet openings lead into two separate channels, each capable of conveying the fluid medium from a foil cushion.The two foil cushions can be controlled separately by two separate power supplies. Figure 18B shows the contraction of the two foil cushions between the three expansion-stop elements (8, 8', 8") when a high electrical voltage is applied. This zipping process shifts the expansion zones (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushions to the right of the zipping zones is prevented between the three expansion-stop elements (8, 8', 8"). The entire fluid medium (6) is forced out of the two foil cushions.

[0119] Figure 19A shows a side view of a pressure generator (7) according to the invention, comprising a foil cushion filled with a fluid medium (6) and consisting of two flexible films (2, 2') with a sealing seam (3), as well as two electrode layers (4, 4') on the outer surfaces of the foil cushion and electrode leads (5, 5') between two expansion-stop elements (8, 8') with spacers (9, 9' (not visible)). An expansion zone (10) begins at the sealing seam (3), in which the distance between the two flexible films (2, 2') changes. The foil cushion is not attached over its entire surface to either of the two expansion-stop elements (8, 8'). On the inner surfaces of each of the two expansion-stop elements, there is an additional electrode layer (16, 16') which is covered by an electrically insulating dielectric layer (17, 17'). On the right side, the foil cushion has an outlet opening (12) through which the fluid medium (6) can be pushed out.Figure 19B shows the contraction of the foil cushion between the two expansion-stop elements (8, 8') when a high electrical voltage is applied. This zipping process shifts the expansion zone (10) in the pressure generator (7) to the right. Unlike prior art zipping actuators, the expansion of the foil cushion to the right of the zipping zone is prevented between the two expansion-stop elements (8, 8'). The entire fluid medium (6) is forced out of the two foil cushions. Figure 19C shows the expansion of the foil cushion between the two expansion-stop elements (8, 8') after the high electrical voltage is switched off and a different electrical voltage is applied between each electrode layer (16, 16') on an expansion-stop element (8, 8') and the nearest electrode layer (4, 4') on the foil cushion.The entire fluid medium (6) is actively drawn back into the foil cushion through the outlet opening (12). Figure 20A shows a side view of a (non-inventive) utility actuator (18) in the form of a cube-shaped deformable hollow body (19) made of an elastic material with an inlet opening (20) on the left side. Figure 20B shows how the deformable hollow body (19) elastically elongates with increasing pressure in the cavity, the cross-sectional area being kept constant by rectangular stiffening rings (21) around the hollow body.

[0120] Figure 21A shows a side view of a (non-inventive) utility actuator (18) in the form of a rigid hollow body (22) with an inlet opening (20) on the left side, an opening at the top, and a stretchable membrane (23) made of an elastic material that closes the upper opening. Figure 21B shows how the stretchable membrane (23) bulges elastically upwards with increasing pressure in the hollow body.

[0121] Figure 22A shows a side view of a (non-inventive) utility actuator (18) in the form of a balloon-shaped deformable hollow body (19) made of an elastic material with an inlet opening (20) on the left side. Figure 22B shows how the deformable hollow body (19) expands elastically with increasing pressure inside the hollow body.

[0122] Figure 23A shows a side view of a (non-inventive) utility actuator (18) in the form of an elongated, cube-shaped, deformable hollow body (19) made of an elastic material with an inlet opening (20) on the left side. Figure 23B shows how the deformable hollow body (19) bends elastically upwards with increasing pressure inside the hollow body, whereby the transverse expansion perpendicular to the length is prevented by rectangular stiffening rings (21) around the deformable hollow body and longitudinal expansion on the top side by a flexible but non-stretchable film (not shown).

[0123] Figure 24A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 6A and a utility actuator (18) in the form of a cube-shaped deformable hollow body as shown in Figure 20A, which is connected to the pressure generator (7) via a connecting channel (25). The entire actuator system (24) is filled with a fluid medium. Figure 24B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This forces the fluid medium from the pressure generator (7) into the utility actuator (18), causing the deformable hollow body to expand lengthwise.

[0124] Figure 25A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 6A and a utility actuator (18) in the form of a balloon-shaped deformable hollow body as shown in Figure 22A, which is connected to the pressure generator (7) via a connecting channel (25). The entire actuator system (24) is filled with a fluid medium. Figure 25B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This forces the fluid medium from the pressure generator (7) into the utility actuator (18), causing the deformable hollow body to expand.

[0125] Figure 26A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 6A and a utility actuator (18) in the form of an elongated, cube-shaped, deformable hollow body as shown in Figure 23A, which is connected to the pressure generator (7) via a connecting channel (25). The entire actuator system (24) is filled with a fluid medium. Figure 26B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This forces the fluid medium from the pressure generator (7) into the utility actuator (18), producing a bending deformation of the deformable hollow body.

[0126] Figure 27A shows a side view of an actuator system (24) according to the invention as shown in Figure 25A, comprising a pressure generator (7) according to Figure 6A and a utility actuator (18) in the form of a balloon-shaped deformable hollow body according to Figure 22A, which is connected to the pressure generator (7) via a connecting channel (25). A valve (26) is located in the connecting channel (25). The entire actuator system (24) is filled with a fluid medium. Figure 27B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This forces the fluid medium from the pressure generator (7) into the utility actuator (18), causing the deformable hollow body to expand. Figure 27C shows that the connecting channel (25) between pressure generator (7) and utility actuator (18) is closed by the valve (26), which maintains the expansion of the deformable hollow body even without applied stress.

[0127] Figure 28A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 6A and a utility actuator (18) in the form of a cube-shaped deformable hollow body as shown in Figure 20A, which is connected to the pressure generator (7) via a connecting channel (25). A movable piston (27) is located in the connecting channel (25), separating the first fluid medium in the pressure generator (7) on the left side from a second fluid medium (28) in the utility actuator (18) on the right side. Figure 28B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This causes the first fluid medium from the pressure generator (7) to be forced against the movable piston (27), which in turn forces the piston against the second fluid medium (28) in the utility actuator (18), thus causing the utility actuator (18) to expand in length.

[0128] Figure 29A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 6A and a utility actuator (18) in the form of a cube-shaped deformable hollow body as shown in Figure 20A, which is connected to the pressure generator (7) via a connecting channel (25). A stretchable separating membrane (29) is located in the connecting channel (25), separating the first fluid medium in the pressure generator (7) on the left side from a second fluid medium (28) in the utility actuator (18) on the right side. Figure 29B shows the contraction of the foil cushion between the two expansion barrier elements in the pressure generator (7) when a high electrical voltage is applied. This causes the first fluid medium from the pressure generator (7) to be pressed against the expandable separating membrane (29), causing it to expand to the right, press against the second fluid medium (28) in the utility actuator (18) and thus create an expansion of the utility actuator (18) in length.Figure 30A shows a side view of an actuator system (24) according to the invention, comprising a dual pressure generator (7) as shown in Figure 18A and a utility actuator (18) in the form of a cube-shaped deformable hollow body containing two elongated, separate, parallel cavities. Lateral expansion perpendicular to the length is prevented by rectangular stiffening rings surrounding the hollow body. Each of the two cavities is connected to an opening of a foil cushion in the pressure generator (7). The entire actuator system (24) is filled with a fluid medium. Figure 30B shows the contraction of the lower foil cushion between the two surrounding expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied.This forces the fluid medium from the lower foil cushion into the lower cavity in the actuator (18), thereby causing the lower part of the actuator (18) to expand lengthwise, resulting in an upward bending deformation of the actuator (18). Figure 30C shows the contraction of the upper foil cushion between the two surrounding expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied to it. This forces the fluid medium from the upper foil cushion into the upper cavity in the actuator (18), thereby causing the upper part of the actuator (18) to expand lengthwise, resulting in a downward bending deformation of the actuator (18).

[0129] Figure 31A shows a side view of an actuator system (24) according to the invention, comprising a pressure generator (7) as shown in Figure 19A and a utility actuator (18) in the form of a cube-shaped deformable hollow body as shown in Figure 26A, which is connected to the pressure generator (7) via a connecting channel. Figure 31B shows the contraction of the foil cushion between the two expansion-stop elements in the pressure generator (7) when a high electrical voltage is applied. This forces the fluid medium from the pressure generator (7) into the utility actuator (18), causing a bending deformation of the deformable hollow body. Figure 31C shows the expansion of the foil cushion between the two expansion-stop elements after the high electrical voltage is switched off and another electrical voltage is applied between each electrode layer on an expansion-stop element and the nearest electrode layer on the foil cushion.The entire fluid medium is actively drawn back into the foil cushion, and the bending deformation of the deformable hollow body decreases.

[0130] Reference list for the figures

[0131] 1 Zipping actuator

[0132] 2, 2' Flexible films (electrically insulating dielectric films)

[0133] 3 Seal seam (joining zone)

[0134] 4, 4', 4" electrode layers

[0135] 5, 5', 5", 5'" Electrode leads

[0136] 6 Fluid Medium

[0137] 7 Pressure generator

[0138] 8, 8', 8" expansion stop elements

[0139] 9, 9' spacers

[0140] 10 Expansion Zone

[0141] 11. Support weight

[0142] 12, 12', 12" outlet openings

[0143] 13. Stiff electrically insulating dielectric layer

[0144] 14, 14' Flexible electrically insulating dielectric layers

[0145] 15 Electrically conductive, semiconducting or insulating layer

[0146] 16, 16' Additional electrode layers

[0147] 17, 17' electrically insulating dielectric layers

[0148] 18 Utility actuator

[0149] 19 Deformable hollow body

[0150] 20 Entrance opening

[0151] 21 Stiffening ring

[0152] 22 Rigid hollow body

[0153] 23 Stretchable Membrane

[0154] 24 actuator system

[0155] 25 Connection channel for fluid medium

[0156] 26 valve

[0157] 27 Sliding piston

[0158] 28 Second fluid medium

[0159] 29 Stretchable separating membrane

Claims

Fraunhofer Society...eV P149579PC00 Patent claims 1. Pressure generator containing • a foil cushion containing at least one flexible film and a cavity filled with a fluid medium, • two interconnected and fixed expansion barrier elements for the foil cushion, whose position and orientation relative to each other cannot be changed during operation, as well as • Two electrically contactable electrode layers, each arranged on an inner side of the foil cushion facing the cavity or on an outer side of the foil cushion facing an expansion barrier element or on an expansion barrier element for the foil cushion, wherein at least one of the two electrode layers is arranged on the at least one flexible foil and an electrically insulating layer and at least a part of the cavity containing the fluid medium are located between the two electrode layers, characterized in that by applying an electrical voltage between the two electrode layers or between the two electrode layers and a further electrode layer, the foil cushion is compressible in the areas of the foil cushion covered by electrode layers and is prevented by the expansion barrier elements from expanding further than the expansion barrier elements allow.

2. Pressure generator according to claim 1, characterized in that a) the film cushion is formed from two films connected to each other at the edge regions in a connection zone, wherein the first film is the flexible film and the second film is a flexible or rigid film, wherein the films are preferably connected to each other by a material bond, in particular by gluing or welding, or by a force bond, in particular by a clamping connection, or b) the film cushion is formed from the flexible film in the form of a bag folded into two partial films at the circumferential edge regions in a connection zone, or c) the film cushion is formed from one of the two expansion barrier elements and the flexible film, wherein the flexible film is connected to the expansion barrier element at the edge regions in a connection zone.

3. Pressure generator according to claim 2, characterized in that a) at the edge regions in the connection zone of the film cushion, an electrically conductive or an electrically semiconducting or an electrically insulating layer is located.

4. Pressure generator according to one of claims 1 to 3, characterized in that the inner surfaces of the expansion barrier elements, between which the foil cushion is located, are arranged at a constant distance from each other in at least one surface segment, wherein the constant distance of the expansion barrier elements is preferably a maximum of 30 mm, more preferably a maximum of 10 mm and particularly preferably in the range of 0.01 pm to 3 mm and / or wherein the expansion barrier elements have a maximum deformation of 10 mm at a differential pressure between the inner and outer surfaces of 10 kPa, preferably a maximum of 1 mm and particularly preferably a maximum of 0.1 mm, or that the distance between the inner surfaces of the expansion barrier elements, between which the foil cushion is located, continuously increases or decreases in at least one surface segment.

5. Pressure generator according to one of claims 1 to 4, characterized in that at most one outer surface of the foil cushion is connected or attached to an expansion barrier element at least partially over a surface.

6. Pressure generator according to one of claims 1 to 5, characterized in that the foil cushion between the two expansion barrier elements has a material-bonded connection, e.g. a sealing seam, or a force-fit connection in a connection zone, which either connects two foil edges or a foil edge and the inner surface of one of the expansion barrier elements and in which there is no cavity, and an expansion zone which is enclosed by the connection zone and in which the cavity widens towards the center of the foil cushion, wherein the electrode layers preferably do not completely cover the area enclosed by the connection zone, but have a distance to the connection zone.

7. Pressure generator according to one of claims 1 to 6, characterized in that the expansion barrier elements have at least one of the following properties: • a thickness in the range of 0.1 mm to 100 mm, preferably in the range of 0.3 mm to 30 mm, particularly preferably in the range of 1 mm to 10 mm, • a modulus of elasticity, measured according to DIN EN ISO 178 (bending test), of at least 0.1 GPa, preferably in the range of 0.5 GPa to 5000 GPa, particularly preferably in the range of 1 GPa to 2000 GPa, • a bending stiffness of at least 0.1 N mm 2 , preferably in the range of 1 N mm 2 up to 10 kN mm 2 , particularly preferably in the range of 10 N mm 2 up to 5 kN mm 2, measured according to DIN 53350.

8. Pressure generator according to one of claims 1 to 7, characterized in that the material of the expansion barrier elements is selected from the group consisting of • Thermoplastics, in particular polyethylene (PE), polypropylene (PP), polystyrene (PS), polyamides (PA), acrylonitrile butadiene styrene (ABS), polylactide (PLA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK) and polyvinyl chloride (PVC), • Thermosets, especially acrylates, epoxides, polyesters, vinyl esters, metals, especially steel, • Glass, ceramics or glass-ceramics, • Concrete or reinforced concrete and • Combinations thereof, which may also be reinforced, in particular with fibers, particles or fiber layups / mats, with particular preference given to materials that can be used in 3D printing.

9. Pressure generator according to one of claims 1 to 8, characterized in that an additional electrode layer is located on the inside of an expansion barrier element or an additional electrode layer is located on the inside of both expansion barrier elements, which is separated from the nearest electrode layer of the foil cushion by an electrically insulating layer.

10. Pressure generator according to one of claims 1 to 9, characterized in that the foil cushion has an opening through which, when an electrical voltage is applied between the two electrode layers of the foil cushion, the fluid medium can be forced out of the foil cushion.

11. Actuator system comprising a pressure generator according to claim 10 and a utility actuator with a cavity containing a fluid medium, preferably the same fluid medium as in the pressure generator, wherein the cavity of the utility actuator is connected to the cavity of the foil cushion by a connecting channel or is directly connected to the cavity of the foil cushion or is a part of the foil cushion, and wherein the utility actuator is deformable by the pressure of the fluid medium generated in the pressure generator.

12. Actuator system according to claim 11, characterized in that the connecting channel contains a valve which, in the closed state, blocks the flow of the fluid medium and, in the open state, allows the flow, wherein the valve preferably contains an actuator made of a smart material, particularly preferably an electrostatic zipping actuator or a dielectric elastomeric actuator.

13. Actuator system according to claim 11 or 12, characterized in that the connecting channel contains a movable or deformable media separating element that separates the fluid media on both sides from each other, preferably a movable piston or a flexible or stretchable membrane, wherein the fluid medium on the side of the media separating element towards the useful actuator is preferably a liquid, preferably water or an aqueous solution, or a gas, preferably air or nitrogen.

14. Actuator system according to one of claims 11 to 13, characterized in that, in the event of a pressure reduction at the useful actuator, a return transport of the fluid medium into the pressure generator is enabled, in particular by making the useful actuator elastically deformable back to its initial state, or by placing a weight on the useful actuator, or by applying an electrical voltage between one of the electrode layers of the foil cushion and an additional electrode layer on the inside of an expansion barrier element of the pressure generator.

15. Actuator system according to one of claims 11 to 14, characterized in that the pressure generator comprises two foil cushions filled with a fluid medium, each with an opening and each with two electrode layers, which are located between three interconnected and fixed expansion-stop elements, the position and orientation of which relative to each other cannot be changed during operation. are arranged, wherein it is preferred that the openings of the two foil cushions are connected to each other and to the utility actuator via a common connecting channel, or that the openings of the two foil cushions are not connected to each other and are connected to two utility actuators or to one utility actuator with two separate cavities via two separate connecting channels.

16. Use of the pressure generator according to one of claims 1 to 10 or the actuator system according to one of claims 11 to 15 for generating hydraulic or pneumatic pressure, in particular for actuator applications such as lifting devices, clamping devices, robot grippers, seat adjustments, massage devices, surgical instruments, haptic feedback, positioning devices, battery tensioning and compression, valves, pumps, human-machine interfaces, button-on-demand switches, bumper-on-demand safety systems, seat hardness adjustment, electromechanical elements for games, exoskeletons, prostheses, orthoses, wearable controllable aids such as gloves.

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