Pneumatic Linear Actuator

Abstract

Pneumatic linear actuators are cheap to manufacture and particularly suitable for applications in the field of robot-assisted surface processing. [Solution] A pneumatic actuating element is disclosed. According to one embodiment, the actuating element comprises a housing having a pressure chamber, a rod inserted from the outside into the pressure chamber of the housing, a rod seal arranged around the rod and sealing the pressure chamber, and a rod guide attached to the housing and configured to guide the rod along its longitudinal axis. No piston is arranged in the pressure chamber. Instead, the pressure chamber includes an annular gap that is not sealed between the rod and an inner wall of the pressure chamber, such that gas pressure present in the pressure chamber spreads throughout the pressure chamber up to the rod seal.

Description

[Technical field]

[0001] The present invention relates to the field of pneumatic actuators, and in particular to a cost-effective configuration of a pneumatic linear actuator that can replace a double-acting pneumatic cylinder in certain applications. [Background technology]

[0002] There are many different types of pneumatic actuators. In particular, pneumatic cylinders are used in a wide range of applications. It is also known to use pneumatic actuators for force control, for example in robot-assisted automated surface processing, and generally in applications where the robot touches the surface "gently" (without impact), for example with a tool. An example of a pneumatic handling device for use in industrial robots is described in US 10,906,177. Well-known devices and systems include, inter alia, bellows cylinders, air muscles, double-acting pneumatic cylinders, but such devices are complex and expensive to manufacture. One of the requirements for such handling devices for robot-assisted surface processing is the ability to absorb bending moments. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US 10,906,177 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors set out to develop a pneumatic linear actuator which is inexpensive to manufacture and which is particularly suitable for applications in the field of robot-assisted surface processing. [Means for solving the problem]

[0005] The above problem is solved by a device according to claim 1 and an actuating element according to claim 13. Different embodiments and further developments are the subject matter of the dependent claims.

[0006] A pneumatic actuating element is disclosed. According to one embodiment, the actuating element comprises a housing having a pressure chamber, a rod inserted from the outside into the pressure chamber of the housing, a rod seal arranged around the rod and sealing the pressure chamber, and a rod guide attached to the housing and configured to guide the rod along its longitudinal axis. No piston is arranged in the pressure chamber. Instead, the pressure chamber includes an annular gap that is not sealed between the rod and an inner wall of the pressure chamber, such that gas pressure present in the pressure chamber spreads throughout the pressure chamber up to the rod seal.

[0007] Further embodiments relate to a handling device or a linear actuator with a pneumatically actuated element. Effect of the Invention

[0008] It can be manufactured inexpensively, which is particularly advantageous for applications in the field of robot-assisted surface processing. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an exemplary schematic diagram of a robot-supported grinding apparatus with a grinding machine coupled to an industrial robot by a force-controlled linear actuator, which causes a partial mechanical decoupling between the industrial robot and the grinding machine.

[0010] [Diagram 2] FIG. 1 is a side view showing an example of a pneumatic linear actuator (handling device).

[0011] [Diagram 3] FIG. 1 is a schematic longitudinal cross-sectional view of a first embodiment.

[0012] [Figure 4] FIG. 11 is a schematic longitudinal cross-sectional view of a second embodiment.

[0013] [Diagram 5] FIG. 13 is a schematic longitudinal cross-sectional view of the third embodiment at a moderate displacement.

[0014] [Figure 6] FIG. 6 illustrates the minimum displacement of the embodiment shown in FIG. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Various embodiments are described in more detail below using illustrated examples, which are not necessarily to scale and the invention is not limited to the illustrated embodiments, but rather the emphasis is on explaining the principles underlying the invention.

[0016] In robot-assisted surface processing, a machine tool (e.g. grinding, drilling, milling, polishing, etc.) is guided by a manipulator, e.g. an industrial robot. The machine tool can be coupled in various ways to a so-called end-effector flange, whose orientation is fixed at the TCP (Tool Center Point) of the manipulator. The manipulator can usually adjust the position and orientation of the TCP practically freely and move the machine tool, e.g. in a trajectory parallel to the surface of the workpiece. The industrial robot is usually position-controlled, which allows the TCP to be moved precisely along the desired trajectory. However, the following does not only apply to robot-assisted surface processing, but also to any robotics application in general, where the robot has to contact the surface more or less gently (without impacts) with its tool. This can also be applied, for example, to pick-and-place uses.

[0017] In many cases, control of the processing force (e.g., the force when contacting the workpiece, the contact force during surface treatment such as grinding force, etc.) is required, but it is often difficult to obtain sufficient accuracy with conventional industrial robots. Since the arm of an industrial robot is large and heavy, the inertial mass is large, and the controller (closed-loop control) cannot quickly respond to the fluctuation of the processing force. To solve this problem, a linear actuator that is smaller (and lighter) than the industrial robot can be placed between the end effector flange of the manipulator and the machine tool, which can couple the end effector flange of the manipulator and the machine tool. In surface processing, the linear actuator controls only the processing force (the contact force between the tool and the workpiece), and the manipulator is position-controlled to move the tool or machine tool along the desired trajectory together with the linear actuator. By force control, the linear actuator can compensate (within a certain range) for inaccuracies in the position and shape of the workpiece to be processed and inaccuracies in the trajectory of the manipulator. However, there are robots that can adjust the processing force by force / torque control even without the aforementioned linear actuator, but such robots are relatively complex and expensive.

[0018] Before describing the various embodiments of the present invention in detail, a general example of a robot-assisted grinding device will first be described. The concepts described herein can be applied to other types of surface finishing (e.g., polishing, milling, drilling) and are not limited to grinding. As previously mentioned, the embodiments described herein can be used as linear actuators (handling devices) in a wide variety of applications and are typically a cost-effective alternative to linear actuators driven by pneumatic cylinders.

[0019] According to FIG. 1, the robot-assisted grinding device comprises a manipulator 80, for example an industrial robot, and a grinding machine 50 with a rotating grinding tool 51. The grinding machine 50 is coupled to the end-effector flange of the manipulator 1 via a linear actuator 20. The pose (position and orientation) of the end-effector flange also determines the TCP. Strictly speaking, the TCP is not a point but a vector, and can be described, for example, by three spatial coordinates (position) and three angles (directions). In robotics, generalized coordinates in the configuration space (usually the six joint angles of the robot) are sometimes used to describe the position of the TCP. The position and orientation of the TCP are often called "pose". The position (including orientation) of the TCP defines the movement of the grinding tool as a function of time, and this movement is called a trajectory. The TCP is often defined as the center of the end-effector flange of the robot, but this is not necessarily the case. The TCP can be any point (theoretically it can be outside the robot) where the robot can adjust its position and orientation. The TCP can also define the origin of the tool coordinate system.

[0020] In the case of an industrial robot having six degrees of freedom, the manipulator 80 has joints G 11 , G 12 , G 13 The first segment 82 is usually (but not necessarily) fixedly (rigidly) connected to the foundation 81. The joint G 11 connects the segments 82 and 83. 11 The joint G may be biaxial, allowing the segment 83 to rotate about a horizontal axis of rotation (elevation) and a vertical axis of rotation (azimuth). 12 Joint G connects segment 83 and segment 84 and allows pivotal movement of segment 84 relative to the position of segment 83. 13 Joint G connects segment 84 and segment 85. 13 can be biaxial, so (joint G11 1 and 2). The end effector flange and therefore the TCP have a fixed relative position with respect to the segment 85, which typically includes a revolute joint (not shown) that allows a revolute movement of an end effector flange 86 arranged on the segment 85 about a longitudinal axis A (shown in dashed lines in FIG. 1 and corresponding in the illustrated example to the axis of rotation of the grinding tool). Each axis of the joints is assigned an actuator (e.g. an electric motor) by which a rotational movement about the respective joint axis can be brought about. The actuators of the joints are controlled by the robot control 70 according to a robot program. Various industrial robots / manipulators and associated controls are known and will not be described further here.

[0021] The manipulator 80 is usually position-controlled, i.e. the robot controller determines the pose (position and orientation) of the TCP and can move it along a predefined trajectory. In FIG. 1, the longitudinal axis of the segment 85 on which the TCP is located is denoted as A. When the actuator 100 of the handling device 100 is at its end stop, the pose of the end effector flange (or TCP) also defines the pose of the grinding machine 50 (and the tool / grinding disk 51). As mentioned at the beginning, the linear actuator 100 sets the contact force (machining force) between the tool and the workpiece 60 to the desired value during the grinding process. Direct force control by the manipulator 80 is usually too inaccurate for grinding applications. This is because the high mass inertia of the segments 83-85 of the manipulator 80 makes rapid correction of force peaks (e.g. when placing the grinding tool on the workpiece 60) practically impossible with conventional manipulators. For this reason, the robot control unit 70 is configured to control the posture (position and direction) of the TCP of the manipulator 80, and force control is usually performed solely by the actuator 100.

[0022] As already mentioned, during the grinding process, the contact force F between the grinding tool (grinding machine 50 with grinding plate 51) and the workpiece 60 K is the contact force F between the grinding plate 51 and the workpiece 60 (in the direction of the longitudinal axis A). K The contact force F can be set by the linear actuator 100 and the force control (which can be realized in the control unit 70, for example) so that F corresponds to a predetermined value. K is the actuator force F with which the linear actuator 100 presses against the surface of the workpiece. A 5. In the absence of contact between the workpiece 60 and the tool 51, the actuator 100 moves to an end stop (not shown as it is integrated in the actuator 100) due to the lack of contact force on the workpiece 60 and presses with a defined force. In this case, the force control can be active all the time. Thus, in this situation (no contact), the actuator displacement is at a maximum and the actuator 100 is at its end. The defined force with which the actuator 100 presses against the end stop can be regulated to be very small or even zero (theoretically) in order to allow the smoothest contact with the workpiece surface.

[0023] The position control of the manipulator 80 can be performed completely independently of the force control of the actuator 100 (which can also be achieved by the control unit 70). The actuator 100 is not used for positioning the grinding machine 50, but rather for controlling the desired contact force F during the grinding process. K and to detect contact between the tool 51 and the workpiece 60. This contact is simply recognized, for example, by the linear actuator moving away from its end position (the actuator displacement is less than its maximum displacement at the end).

[0024] The direction of movement of the actuator 90 and the axis of rotation of the grinding machine 50 do not necessarily have to coincide with the longitudinal axis A of the segment 85 of the manipulator 80. In the case of a pneumatic actuator, the force control can be realized in a known manner using a control valve, a regulating device (for example implemented in the control unit 70), a compressed air accumulator or a compressor. To take into account gravity (i.e. the weight of the grinding machine 50), the tilt with respect to the vertical is relevant, so the actuator 100 may include a tilt sensor or this information may be determined based on the joint angle of the manipulator 80. The determined tilt is taken into account by a force regulating device. The specific implementation method of the force control is known and is not important for the following description, so a detailed description will be omitted. The linear actuator 100 not only allows a reliable mechanical decoupling between the manipulator 80 and the workpiece 60, but also compensates for inaccuracies in the positioning of the TCP and / or the workpiece.

[0025] In another type of robot-assisted surface processing, the machine tool is attached to a fixed base via a linear actuator and a conventional industrial robot is position controlled to guide the workpiece to the machine tool (e.g. a grinding machine). The processing force is controlled by the linear actuator, while the robot is position controlled in a conventional manner: during the surface treatment process, the linear actuator (supported by a base) presses the machine tool against the workpiece, which is held in a defined position by the robot.

[0026] Hereinafter, the linear actuator 100 is also referred to as a handling device. FIG. 2 is a side view of the embodiment. As shown in FIG. 2, the device has two opposing mounting plates (mounting flanges) 101, 102, where the first mounting plate 101 is configured to mechanically couple the device to a tool (e.g., a gripper) or machine tool (e.g., a grinding machine, a polishing machine, etc.) and the second mounting plate 102 is configured to mechanically couple the device to an end effector flange 86 (see FIG. 1) of a manipulator. For example, the second mounting plate 102 is attached to the end effector flange 86 by screws. Similarly, the machine tool can be attached to the first mounting plate 101 by screws. Other mounting methods (clamps, bayonet connection, etc.) are also possible.

[0027] The interior of the handling device, located between the mounting plates 101, 102, is covered in the example shown by a bellows 105, which serves essentially to keep dust and other impurities away from the internal components of the device, although other covering configurations are possible.

[0028] FIG. 3 is a schematic diagram showing a first embodiment of the handling device described herein. It should be emphasized at the outset that it is not a conventional piston and (pneumatic) cylinder combination, but merely a rod 110 guided in a rod guide 112 and inserted inside a housing 130. A conventional rod seal 113 seals the inside of the housing 130 along the circumference of the rod 110. That is, the rod seal 113 and the rod guide 112 are spaced apart axially (along the longitudinal axis B of the rod). The rod 110 is mounted in the rod guide 112 so that it can move along its longitudinal axis. In the illustrated example, the rod guide 112 is arranged in a bush 131 that is arranged in the housing 130. For example, the rod guide 112 can be configured to be press-fitted into the bush 131. Other techniques for mounting the rod guide 112 in or on the housing 130 are also possible. The rod guide 112 may be or include a recirculating ball bearing guide. The rod guide is usually made of stainless steel. A variety of rod guides are known and commercially available and will not be described further herein.

[0029] The rod guide 112 allows only longitudinal movement of the rod 110 (along the longitudinal axis B) and is particularly able to absorb bending moments, i.e. torques about axes perpendicular / transverse to the longitudinal axis B. The rod guide is also called a shaft guide and in particular a linear bearing. In one construction, a linear ball bearing is used as the rod guide. A linear ball bearing, also called a ball bushing, has the advantage that the static friction between the bearing and the rod is relatively low (practically zero), which makes it possible to largely avoid stick-slip effects.

[0030] When the rod 110 is displaced, the volume of the interior of the housing 130 changes. The interior of the housing can be supplied with compressed air (see FIG. 3, compressed air inlet / outlet 115), so that the interior will be referred to below as a pressure chamber 114 (pressure p 1). The end face of the rod 110, which is on the outside of the housing 130, is connected to one of the mounting plates (in the example shown, mounting plate / flange 101). The housing 130 is attached to the other mounting plate (in the example shown, mounting plate / flange 102). The mechanical connections between the rod 110 and the mounting plate 101 and between the housing 130 and the mounting plate 102 can be made, for example, by means of screws. However, other joining techniques are also possible (gluing, press fit, etc.).

[0031] The (air) pressure p in the pressure chamber 114 1 A force F acting on the rod 110 (along its longitudinal axis B) at 1 p 1 ×A 1 where A is 1 =d 1 2 It is π / 4. Pressure p 1 is usually a positive pressure, higher than the atmospheric pressure outside the pressure chamber. 1 denotes the diameter of the rod 110 within the pressure chamber 114, specifically the diameter of the rod 110 in the region of the rod seal 113. In the embodiment described here, the pressure chamber 114 has an inner diameter d 1 ', and there is an (annular) gap d between the circumferential surface of the rod 110 and the inner wall of the pressure chamber 114 (i.e., d 1 '=d 1 +2×δ). Force F due to compressed air 1 is the restoring force F that can be generated by, for example, the spring 150 R In the illustrated example, the spring 150 also acts between the two mounting plates 101, 102 and exerts a restoring force F R (F R ≈ΔL, k denotes the spring constant). The minimum distance between the mounting plates 101 and 102 is defined, for example, by an end stop, L 0(ΔL=0, see FIG. 2). The maximum distance between mounting plates 101 and 102 can be similarly defined by end stops, which are not shown in FIG. 3. Other restoring elements can also be used instead of spring 150.

[0032] Unlike a conventional piston and cylinder combination, the pneumatic effective area is equal to the cross-sectional area of ​​the rod 110 in the region of the rod seal 113. In the example shown, there is no equivalent of a piston seal (that moves with the piston), only a rod seal 113 (that does not move with the rod) attached to the housing 130. Since there is no piston with a piston seal in the example described here, the gas pressure p 1 extends throughout the entire pressure chamber 114 (i.e., also in the annular gap d) up to the rod seal 113. In contrast, the piston divides the interior of the housing 130 into two pressure chambers, which is not the case in the example described here. The housing 130 consists of only one (single) pressure chamber 114. At the same time, the rod guide 112 (linear bearing) contributes to reliable absorption of bending moments in a compact and cost-effective configuration. In conventional actuators using normal pneumatic cylinders, the linear guide, which can absorb relatively large bending moments, is arranged separately next to the pneumatic cylinder (i.e., parallel to the cylinder).

[0033] The housing 130 can be made of plastic, for example using an injection molding process or additive manufacturing (3D printing). The material of the housing 130 is more elastic (less rigid) than the material of the rod guides (usually steel). In another example, the housing 130 is manufactured using aluminum die casting. Machining (e.g. milling) is only required in the area of ​​the bushings 131 and possibly the surfaces that are connected to the mounting plate 102. Overall, the linear actuator according to FIG. 3 is inherently easier and cheaper to manufacture than linear actuators that use conventional pneumatic cylinders as actuating elements.

[0034] Figure 4 shows an embodiment of another configuration with rod 120, housing 140, rod guide 122 and rod seal 123. The left part of Figure 4 has the same structure as the example of Figure 3 and is referred to above. The right part of the device of Figure 4 is constructed similarly to the left part, but is connected upside down to the mounting plates 101, 102. The two actuating elements (consisting of the housing with the rod guide and rod seal respectively and the rod) with longitudinal axes B and B' are arranged anti-parallel to each other, so to speak.

[0035] A two-rod configuration is more stable in terms of absorbing bending moments and can generate larger forces. It is also possible to arrange the two actuators in parallel (rather than anti-parallel). In this case, the right-hand part of the device in FIG. 4 is configured the same as the left-hand part and is connected to the mounting plates 101, 102 in the same way. In some embodiments, more than one combination of pressure chamber, rod and housing with rod guide is provided in order to increase the maximum actuator force (if the pressure in the pressure chamber is the same, the pneumatically effective end surfaces of the rods are additive) and to increase the maximum possible bending moment.

[0036] The housing 140 of the second actuating element is connected (e.g. by screws) to the mounting plate 101 and the end face of the rod 120, which is on the outside of the housing 140, is connected (e.g. also by screws) to the opposing mounting plate 102. The housing 140 has a bush 141 in which the rod guide 122 is arranged. A rod seal 123 is arranged adjacent (axially spaced apart) the rod guide 122 in the housing 140 (similar to the housing 130 and rod seal 113). The interior of the housing 140 forms a pressure chamber 124, the volume of which depends on the position of the rod 120. Compressed air (pressure p 2 ) can reach the pressure chamber 124 through the inlet / outlet 125. The force F acting on the rod 120 2 is the pressure p 2 and the effective air pressure area A 2 =d 2 2It is proportional to π / 4 (i.e., F 2 =P 2 ×A 2 ).

[0037] In the example of FIG. 4, the gas pressure p 2 When the pressure p is negative, the combination of the second rod 120 and the second pressure chamber 124 disposed in the second housing 140 can function as a restoring element. The negative pressure is a pressure p that is lower than the atmospheric pressure outside the device. 2 With the chambers at negative pressure, each rod / housing / chamber combination essentially acts like a spring that exerts a restoring force. In this case, the force is controlled by adjusting the (positive) pressure in the other chamber, since positive pressure is actually easier to control than negative pressure.

[0038] As already mentioned with reference to FIG. 3, also in this embodiment the pneumatically effective areas A1 and A2 are equal to the cross-sectional area of ​​the rods 110 and 120 in the area of ​​the rod seals 113 and 123. The areas A1 and A2 can be the same. Unlike conventional configurations, no piston seals are required. The rod seals 113 and 123 are located in the respective housings 130 and 140 and are not movable relative to the respective housings 130 and 140. The restoring force F 2 Since is generated by air pressure, no spring is needed in this example, however a spring could be provided (as in Figure 3).

[0039] As mentioned above, the housings 130 and 140 can be made of a more elastic (less rigid) material than the material of the rod guides 112, 122 (typically steel). For example, the housings 130 and 140 are made of plastic (by injection molding) or aluminum (by die casting). As mentioned above, additive manufacturing (3D printing) is also possible. A relatively elastic housing allows to compensate (within certain limits) deviations from perfect parallelism of the longitudinal axes B, B' of the rods 110, 120, thus preventing the linear actuator from jamming. Deviations from parallel alignment of the longitudinal axes B and B' occur on the one hand due to manufacturing tolerances and on the other hand due to bending moments during operation.

[0040] Figure 5 shows the construction of another embodiment, very similar to the embodiment shown in figure 4. In terms of functionality, the embodiment of figure 5 basically corresponds to the embodiment of figure 4, with two actuating elements arranged anti-parallel between the mounting plates 101, 102. Furthermore, a spring 150 is arranged between the two mounting plates 101, 102 as a restoring element, which brings the linear actuator / handling device into a defined end position, even when the pressure chambers 114, 124 of the two actuating elements are not pressurized.

[0041] As in the previous embodiment, the housings 130, 140 have bushes 131, 141 for the rod guides 112, 122. The rod seals 113, 123 are arranged coaxially with the rod guides 112, 122 in the respective housings. The two rods 110, 120 are guided antiparallel in the rod guides 112, 122. Depending on the position of the rods (i.e. depending on the displacement ΔL of the linear actuator), the volume of the pressure chambers 114, 124 in the housings changes. In the state shown in FIG. 5, the displacement ΔL is in the medium range. The maximum volume of the pressure chambers 114, 124 is defined by end stops (not shown). The rod 110 is rigidly connected to the mounting plate 101 by the screw 111. Similarly, the rod 120 is connected to the mounting plate 102 by the screw 121. The corresponding housings 130, 140 are rigidly connected (e.g. screwed) to different mounting plates.

[0042] In the contracted state (i.e., the minimum displacement ΔL=0), the end faces of the rods 110, 120 located inside the pressure chambers 114, 124 must not be completely in contact with the walls of the pressure chambers. If they were completely in contact, the corresponding force p 1 A 1 , p 2 A 2 The area A over which pressure acts to generate 1 , A 2 5, which is screwed into the end face of the rod 120, forms an end stop in the contracted state. The screw 129 protrudes from the end face of the rod 110 and therefore also forms a spacer, so that the cross-sectional area A 2 At least a portion of the pressure chamber 124 remains pneumatically active, and the pressure p 2 This allows the rod to generate a force in the fully contracted state. Since the two rods 110, 120 and the corresponding housings 130, 140 are mechanically coupled to the mounting plates 101, 102, a spacer is not absolutely necessary for the rod 110.

[0043] A permanent magnet 118, which is part of a magnetic displacement sensor (not shown in Figures 5 and 6), can be attached to the other rod (left rod 110) by means of a screw 119. The displacement sensor is configured to measure the displacement ΔL of the linear actuator. Various types of suitable magnetic and other displacement sensors are known and will not be described further. Of importance in the embodiment shown is the magnet 118 attached to and moving with the rod 110, which allows for a simple displacement measurement.

[0044] FIG. 6 shows the device shown in FIG. 5 in a fully retracted state (ΔL=0). It can be seen that the head of the screw 129 forms an end stop and rests against the wall of the pressure chamber 124 (opposite the end face of the rod 120). Only the head of the screw 129 is in contact with the wall of the pressure chamber 124, the end face of the rod 120 is not in contact. In the position shown (ΔL=0), it is a distance x away from the opposite wall of the pressure chamber 124. The screw 129 can also be screwed into the opposite wall of the pressure chamber 124, rather than into the end face of the rod 120. Instead of the screw 129, a spacer can also be moulded directly into the wall of the housing or into the rod. The spacer and the housing 140 can be one part (for example a casting). [Explanation of symbols]

[0045] 101…First mounting plate 102…Second mounting plate 110…1st rod, rod 112…1st rod guide, rod guide 113…First rod seal, rod seal 114...first pressure chamber, pressure chamber 120…Second rod 122…Second rod guide 123…Second rod seal 124...Second pressure chamber 129…Spacer 130…First housing, housing 131…Bush 140…Second housing 150...restoring element, spring

Claims

1. a first housing (130) having a first pressure chamber (114); A first rod (110) inserted from the outside into the first pressure chamber (114) of the first housing (130); A first rod seal (113) is disposed around the first rod (110) and seals the first pressure chamber (114), and inside the first pressure chamber (114), there is an annular gap (δ) that is not sealed between the first rod and an inner wall of the first pressure chamber (114), and the gas pressure (p １ a first rod seal (113) configured so that the pressure in the first pressure chamber (114) can be transmitted to the first rod seal (113); a first rod guide (112) attached to the first housing (130) and configured to guide the first rod (110) along a longitudinal axis of the first rod (110), the first rod guide (112) being spaced apart from the first rod seal (113); The gas pressure (p １ a restoring element (150) arranged to exert a force on said first rod (110) in a direction opposite to the force exerted by said first rod (110); An apparatus having

2. 2. The apparatus of claim 1, wherein the first housing (130) has a single pressure chamber (114) and substantially the same pressure is present throughout the first pressure chamber.

3. 3. The apparatus of claim 1 or claim 2, further comprising a first mounting plate (101) and a second mounting plate (102), the first mounting plate (101) being fixedly connected to the first rod (110) and the first housing (130) being fixedly connected to the second mounting plate (102).

4. The restoring element generates an attractive force (F) between the first mounting plate (101) and the second mounting plate (102). Ｒ , F ２ 4. The apparatus of claim 3, configured to generate a

5. 5. The apparatus according to claim 1, wherein the first housing comprises a bush (131) outside the pressure chamber (114), and the first rod guide (112) is disposed within the bush (131).

6. 6. The apparatus of claim 1, wherein the first rod seal (113) is disposed in a groove in the first housing (130) that extends around the first rod (110).

7. 7. The device according to any one of the preceding claims, wherein the restoring element is a spring (150).

8. a second housing (140) having a second pressure chamber (124); A second rod (120) inserted from the outside into the second pressure chamber (124) of the second housing (140); A second rod seal (123) is disposed around the second rod (120) and seals the second pressure chamber (124), and inside the second pressure chamber (124), there is an unsealed annular gap (δ) between the second rod (120) and an inner wall of the second pressure chamber (124), and the gas pressure (p ２ a second rod seal (123) configured so that the second pressure chamber (114) can be propagated to the second rod seal (123); a second rod guide (122) attached to the second housing (140) and configured to guide the second rod (120) along a longitudinal axis (B') of the second rod (120); 8. The apparatus of claim 1, further comprising:

9. The restoring element is formed by the combination of the second pressure chamber (124) and the second rod (120) and is controlled by the gas pressure (p ２ 9. The apparatus of claim 8, wherein the pressure is negative.

10. An apparatus according to claim 8 or claim 9, wherein the second mounting plate (102) is fixedly connected to the second rod (120) and the second housing (140) is fixedly connected to the first mounting plate (101), the apparatus referring to claim 3.

11. 11. The device according to claim 1, further comprising a spacer (129) acting as an end stop, the spacer (129) being arranged either on an end face of the first rod (110) located in the first pressure chamber (114) or on a wall of the second pressure chamber (124) located opposite the end face of the first rod (110), the spacer (129) ensuring a distance (x) between the end face of the first rod (110) and the opposite wall of the first pressure chamber (114) in the contracted position of the device.

12. 12. The apparatus of claim 11, wherein the spacer (129) is threaded onto the first rod (110) or the first housing (130), or the spacer (129) is an integral part of the first housing (130) or the first rod (130).

13. 13. The device according to any one of the preceding claims, wherein the material of the first housing (130) is made of a material that is more elastic than the material of the first rod (110).

14. a housing (130) having a pressure chamber (114); a rod (110) inserted from the outside into the pressure chamber (114) of the housing (130); A rod seal (113) is disposed around the rod (110) and seals the pressure chamber (114), and inside the pressure chamber (114), there is an annular gap (δ) that is not sealed between the rod and the inner wall of the pressure chamber (114), and the gas pressure (p １ a rod seal (113) configured to allow the pressure in the pressure chamber (114) to propagate through the entire pressure chamber (114) to the rod seal (113); a rod guide (112) attached to the housing (130) and configured to guide the rod (110) along a longitudinal axis of the rod (110), the rod guide (112) configured to absorb bending moments; The gas pressure (p １ a restoring element (150) arranged to exert a force on said rod (110) in a direction opposite to the force exerted by said rod (110); A pneumatic linear actuator having a

15. 15. The pneumatic linear actuator of claim 14, further comprising a spacer (129) functioning as an end stop, the spacer (129) being arranged either on an end face of the rod (110) located within the pressure chamber (114) or on a wall of the pressure chamber (114) opposite the end face of the rod (110), the spacer (129) ensuring a distance (x) between the end face of the rod (110) and the opposite wall of the pressure chamber (114) in a contracted position of the pneumatic linear actuator.

16. Pneumatic linear actuator according to claim 14 or 15, wherein the rod guide (112) is a linear bearing, in particular a linear ball bearing or a ball bushing.

17. 17. The pneumatic linear actuator of claim 14, wherein the rod guide (112) is disposed outside the pressure chamber and in a bush of the housing (130) spaced from the rod seal (113).

18. A manipulator; A device according to any one of claims 1 to 13 attached to an end effector flange of the manipulator; A tool or a machine tool attached to the device; A system having

19. a manipulator for holding and positioning a workpiece; A device according to any one of claims 1 to 13 attached to a base; A tool or a machine tool attached to the device; A system having

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