Actuator with spring return piston

Abstract

Single-acting actuator (1) comprising a cylinder (2), a pressure chamber (7), a spring-return piston (3), and an inner chamber region (8) in which a rack (13) protrudes from the underside of the piston (3), and the rack (13) interacts with a rotatable pinion (14) arranged perpendicular to the rack (13) in the inner chamber region (8), wherein the pitch line of the rack (13) is substantially aligned with the center of the piston (3), wherein one or more return springs (4) are arranged within the inner chamber region (8), and wherein the one or more return springs (4) are arranged on the same side of the piston (3) as the rack (13) and the pinion (14).

Description

[0001] The invention relates to an actuator with a spring return piston, which is used in particular, but not exclusively, as a fluid-operated valve actuator.

[0002] Common single-acting actuators comprise a pressure chamber and an outer chamber aligned axially with the pressure chamber. The piston is located in the pressure chamber and is driven in a first direction, toward the outer chamber, by the ingress of pressurized fluid into the pressure chamber. Return springs are located in the outer chamber and are mounted between one end of the outer chamber and the piston. When the piston is pushed in the first direction, the springs are compressed, and when the pressure in the pressure chamber is reduced, the springs drive the piston back in a second direction. A rack attached to the piston and a pinion arranged laterally to the rack are located in the pressure chamber, and as such, the pressure chamber is sometimes referred to as the "inner chamber." The forward or backward movement of the piston moves the rack, which in turn rotates the pinion.

[0003] These known designs of single-acting actuators have a number of disadvantages. First, because the piston is located inside the pressure chamber, it is necessary to provide pressure seals at each end where the piston leaves the chamber. Together with the seal on the piston itself, this means that these known actuators require three seals. Since these components can fail during operation, the chances of malfunction are greater than if fewer seals were required.

[0004] Secondly, the actuators must be large enough to contain both the pressure chamber and the outer chamber. The size of the outer chamber is determined by the size of the compressed springs. The size of an actuator can be of significant importance, especially if it has to be mounted on a valve in confined spaces.

[0005] DE 197 56 425 A1 relates to a rotary drive comprising a cylinder with a hydraulic connection, a piston linearly movable within the cylinder, a cam in the form of a helical groove attached to the piston, a base plate inserted into the cylinder, a centrally mounted rotary shaft therein, a transverse pin attached to the rotary shaft and engaging in the cam, and at least one guide rod mounted in the base plate that secures the piston against rotation. A stop segment is attached to the rotary shaft, which rests against the guide rod in the end positions. The stop segment and guide rod limit the angle of rotation to its exact target value, independent of the stroke. This ensures that the angle of rotation of the rotary drive is always maintained.

[0006] DE 600 12 222 T2 relates to rotary valves controlled by actuators, where the diaphragm actuator is characterized by a rack arranged such that the contact points between the rack and the gear are essentially on a straight line connecting the centers of the movable walls of the pressure chambers that effect the movement. A disadvantage of this actuator is that the spring holding the rack in its rest position is located in a separate, unpressurized spring chamber, which must be sealed off from the two pressure chambers. This increases the length of the actuator and its complexity.

[0007] The present invention aims to overcome some of the problems mentioned above.

[0008] For this purpose, a single-acting actuator according to the invention comprises a cylinder, a pressure chamber, a spring-return piston provided with a connecting means, and an inner chamber area in which a rack protrudes from the underside of the piston, and the rack interacts with a rotatable pinion mounted normal to the rack in the inner chamber area, wherein the pitch line of the rack is substantially aligned with the center of the piston, wherein one or more return springs are arranged within the inner chamber area, and wherein the one or more return springs are arranged on the same side of the piston as the rack and pinion, which form the connecting means.

[0009] (In known actuators, the chamber in which the connecting elements are arranged is referred to as the "inner chamber," while the chamber in which the return springs are arranged is referred to as the "outer chamber." However, these designations are no longer applicable with the actuator according to the invention, since the connecting elements and the return springs are arranged in the same chamber. Therefore, in the following description and the claims, the term "pressure chamber" refers to the chamber which is pressurized during operation, and the term "inner chamber area" refers to the chamber area of ​​the piston on the opposite side of the pressure chamber, which in known actuators would be referred to as the "outer chamber" due to the fact that it is not the pressure chamber.)Since the springs are necessarily located on the side of the piston opposite the pressure chamber, it is the "inner chamber area" that, in the present invention, houses the connecting means and the one or more return springs.

[0010] (The term "connecting element" refers to any mechanical connection that can transform the linear motion of the piston into the rotary output of the actuator. The most common arrangement in valve actuators is a rack and pinion, as described below.)

[0011] Consequently, the actuator according to the invention can be smaller than those in known arrangements, since there is no need to provide extra axial length for the compressed springs. These are now located longitudinally alongside the connecting means. Additionally, the actuator according to the invention does not require pressure seals at each end of the piston, since the piston is no longer arranged in a pressurized chamber.

[0012] Therefore, the one or more springs are arranged within the inner chamber area, the diameter of which can preferably be aligned axially with the diameter of the pressure chamber defined by the cylinder. The one or more return springs can comprise one or more coil springs, which can run essentially parallel to the cylinder. This is the simplest and most practical arrangement of the invention.

[0013] It is obvious that if one or more coil springs are used, they must be comparatively long to provide sufficient restoring forces. Since the internal chamber area described above is quite limited, it may be necessary to ensure that the one or more coil springs do not bend laterally during operation. In a preferred embodiment, the one or more restoring springs can be provided with support elements adapted to support the one or more springs along part or their entire axial length.

[0014] In one arrangement of the invention, the support means can include a rod arranged within each of the one or more coil springs. The one or more rods can protrude from the underside of the inner chamber region, thereby providing a gap between the one or more rods and the lowest stroke position of the underside of the piston, so that the piston does not collide with the rods during operation. The "underside" of the piston is the side opposite the pressure chamber.

[0015] In an alternative embodiment, one or more rods can protrude from the underside of the piston, thereby providing a gap between the one or more rods and the bottom of the inner chamber area when the piston is in its lowest stroke position, so that the rods do not touch the bottom of the inner chamber area during operation.

[0016] In one embodiment of the invention, a body can be arranged within the inner chamber area, and the support means can have one or more chambers formed in the body, each of which can be adapted to receive one or more springs. A spacer gap can be provided between the body and the lowest stroke position of the bottom of the piston so that the piston does not collide with the body during operation.

[0017] Regardless of the design of the support elements, the connecting elements can have a rack and pinion arrangement. The rack protrudes from the underside of the piston and interacts with a rotatable pinion located in the inner chamber area, which is arranged perpendicular to the rack. Consequently, the rack and pinion arrangement is essentially the same as known designs, except that the one or more springs are arranged around it in the inner chamber area.

[0018] The rack's rolling line is aligned with the piston's center, so that forces applied to the piston during operation are transmitted linearly to the pinion, and vice versa. This prevents the piston from tilting to one side during operation. The rack itself can be offset to one side to allow its rolling line to align with the piston's center. A screw can secure the rack to the piston, and the screw can thus be aligned with the piston's center. Again, such an arrangement ensures that a central linear load is applied to the screw during operation, eliminating any potentially disruptive lateral load. With the rack and pinion arranged in this way, piston support is unnecessary.

[0019] In embodiments where the inner chamber area is a free space, a bearing shell can be provided within it, partially surrounding the rack, and a bearing body can be positioned between the rack and the bearing shell. Consequently, a smooth and controlled linear movement can be achieved.

[0020] In the embodiment where the inner chamber is filled with a body, the body can be provided with a bearing chamber in which the rack is arranged, and a bearing element can be provided between the rack and the bearing chamber. This, in turn, can ensure that a smooth and controlled linear motion is achieved.

[0021] The pinion can be fitted with bearings on each side to ensure smooth rotation. Consequently, the separating force between the rack and pinion is contained between the bearing body and the ball / roller / gear bearings.

[0022] Preferably, the movement of the piston from its highest to its lowest position can rotate the pinion by substantially 90°. In other words, the actuator can be a 90° actuator, which can be arranged in all situations where a valve needs to be moved by 90°. It is understood that the invention is not limited to such an arrangement and that it can be used with actuators that provide for movements of more than 90°. The pinion can have three or four teeth.

[0023] It is self-evident that, according to the invention, a yoke or another known arrangement can also be used instead of interlocking teeth.

[0024] In a preferred embodiment of the invention, six coil springs can be provided. It is understood that any number of springs can be provided, but it has been found that six, arranged in groups of three on each side of the rack, work well. In particular, the use of six springs allows a high degree of operational flexibility, since two or four can be removed to reduce the restoring force. Consequently, restoring forces of 689.48 Pa (100 psi), 551.584 Pa (80 psi), and 413.688 Pa (60 psi) can be easily provided with the same configuration.

[0025] To accommodate six coil springs in the inner chamber, the rack and pinion must be shaped and dimensioned accordingly to provide sufficient space. Specifically, the diameter of the pinion body can be smaller than the outer diameter of the pinion teeth. In other words, the pinion teeth can be raised on the pinion.

[0026] In one embodiment, the piston can be provided with a raised central section on its base and underside. This feature ensures that the piston makes centered contact with the top and bottom of the pressure chamber. If the piston tilts slightly to one side, the raised central section will still make contact with the top or bottom of the pressure chamber before any edge does. This prevents any unwanted lateral load from being exerted on the piston, screw, or rack during operation, which could cause them to deflect.

[0027] The actuator can be powered in any known way, including by any fluid, liquid or gas, and it can preferably be a valve actuator.

[0028] Three exemplary embodiments of the invention will now be described with reference to the accompanying drawings. These show: Fig. 1 a perspective exploded view of an actuator according to the invention; Fig. 2 another perspective exploded view of the in Fig. 1 actuator shown; Fig. 3 a top view of the in Fig. 1 actuator shown; Fig. 4 a lateral cross-section through the in Fig. 3 actuators shown; Fig. 5 a top view of a second actuator according to the invention; Fig. 6 a lateral cross-sectional view of the in Fig. 5 actuators shown; Fig. 7 a top view of a third actuator according to the invention; and, Fig. 8 a lateral cross-sectional view of the in Fig. 7 actuators shown.

[0029] As in Fig. As shown in Figure 1, an actuator 1 comprises a cylinder 2 and a spring return piston 3 provided with connecting means in the form of a rack 13 and a pinion 14, wherein one or more return springs 4 are arranged on the same side of the piston 3 as the connecting means (13, 14).

[0030] (The piston 3 and the cover plate 9 are in Fig. 3 is not shown for the sake of simplicity. The same applies to those described below. Fig. 5 and Fig. 7.)

[0031] Actuator 1 is formed from a block 6, which defines the cylinder and houses the moving components of actuator 1. With reference to Fig. Figure 4 shows that cylinder 2 comprises a pressure chamber 7 and an inner chamber area 8, which is a free space arranged below the pressure chamber 7. As can be seen from the figures, the diameter of the inner chamber area 8 is axially aligned with the diameter of the pressure chamber 7.

[0032] The piston 3 is housed in the pressure chamber 7, which is sealed by a cover plate 9. The return springs 4 comprise 6 coil springs arranged parallel to the cylinder 2 and located within the inner chamber area 8 below the piston 3. Each spring 4 is provided with support elements in the form of rods 10, which protrude from a base 11 of the inner chamber area 8, to prevent lateral movement. Fig. 4 The rods 10 have such a length that a gap 12 is provided between them and the pistons 3 when the pistons 3 are in their lowest stroke position.

[0033] A rack 13 extends from the underside 5 of the piston 3 and interacts with a rotatable pinion 14 mounted laterally in the inner chamber area 8. The rack 13 and the pinion 14 each have four teeth 15 and 16, respectively, and a movement of the piston from its highest stroke position to its lowest stroke position rotates the pinion 14 by 90°.

[0034] The pitch line of the rack, which is marked by a dashed line A, is aligned with the center of the piston 3, so that forces exerted on the piston 3 are transmitted linearly to the rack 14 during operation, and vice versa. As such, the rack 13 is offset to one side. A screw 13a (not in Fig. 1 and Fig. (2 shown) secures the rack 13 to the piston 3. As shown Fig. As becomes clear in section 4, screw 13a is also aligned with the center of piston 3.

[0035] In the inner chamber area 8, a bearing shell 17 is provided, which partially surrounds the rack 13. The shell 17 is partially cylindrical and extends over more than 180°, so that it laterally contains the rack 13. A bearing body 17a is provided between the rack 13 and the bearing shell 17. The bearing body 17a is an elastic body that fits into a recess 18 provided in the rear face 19 of the rack 13. The bearing body 17a sits raised above the rear face 19 of the rack 13 and therefore engages with the bearing shell 17 to ensure that a smooth and controlled linear movement is achieved between the rack 13 and the bearing shell 17. The pinion 14 is mounted at each end on bearings 20.

[0036] As can be seen from the figures, the six coil springs 4 are arranged in two groups of three on each side of the rack 13 and the pinion 14. This arrangement provides a balanced and linear return spring force. The rack 13, the pinion 14, the bearing housing 17, and the springs 4 and rods 10 are, of course, dimensioned so that they fit together within the inner chamber area 8.

[0037] As from Fig. As becomes clear in Figure 3, the diameter of the pinion 14 is smaller than the outermost diameter of the pinion teeth 16. Consequently, the pinion 14 is limited and allows sufficient space behind it for three springs 4, and the pinion teeth 16 are raised above the pinion 14.

[0038] The piston 3 is provided with a raised central section 21 on its base 22 and a raised central section 23 on its underside 5, both of which are annular. Consequently, it is these central sections 21 and 23 that contact the top and bottom of the pressure chamber 7 during operation.

[0039] The top of the pressure chamber 7 is defined by the cover plate 9 and the bottom by the top of the bearing shell 17. Consequently, the top of the bearing shell 17 defines the lowest possible stroke position of the piston 3, as shown in Fig. 4 is shown, since the piston 3 cannot be moved behind it. It therefore also defines the boundary between the pressure chamber 7 and the inner chamber area 8. The rods 10 do not extend to the level of the upper side of the bearing shell 17, thus providing a gap 12.

[0040] Cams 24 are formed in the cylinder, which hold the pinion 14 in bearings 20.

[0041] The piston 3 is provided around its peripheral edge with an O-ring 26 (only in Fig. 4 shown).

[0042] During operation, a pressurized fluid (not shown) is introduced into the pressure chamber 7 through an opening 25 in the cover plate 9. The pressure of the fluid exceeds the extension force of the springs 4, causing the piston 3 to move downwards to the lower end of its stroke into the chamber. Fig. Position 4 is shown. The pressure is then reduced until it is less than the extension force of the springs 4, which then push the piston 3 back to the top of its stroke. This process is repeated many times to operate the actuator 1. The pressure seal 26 isolates the pressure chamber 7 from the inner chamber area 8.

[0043] When piston 3 is pushed downwards, the teeth 15 of rack 13 engage with the teeth 16 of pinion 14, and pinion 14 is rotated 90° counterclockwise. When piston 3 is pushed back, pinion 14 is rotated 90° clockwise. Pinion 14 is connected to a valve (not shown), and the forward and reverse rotations open and close the valve.

[0044] When the springs 4 are compressed and then pulled apart as described above, they do not bend laterally because they are guided by the rods 10. The section of the spring 4 that protrudes above the upper ends of the rods 10 and is therefore not guided is too short to bend laterally to any significant extent and cause problems.

[0045] Since the flank line A of the rack 13 is aligned with the center of the piston 3, the load exerted on the rack 13 and the piston 3 during the up and down movement of the piston 3 is linear and balanced. Therefore, the piston 3 does not tilt to one side during operation.

[0046] The separating force generated during operation between the rack 13 and the pinion 14 is absorbed between the bearing body 17a and the bearings 20, which ensures that the flank line A remains central to the piston 3.

[0047] When the piston 3 reaches the upper end of its stroke, the raised central section 21 contacts the cover plate 9. This arrangement ensures that if the piston 3 tilts slightly to one side, the initial contact point between the piston 3 and the cover plate 9 remains part of the raised central section 21. This prevents an edge portion of the piston 3 from striking the cover plate 9, which would exert an undesirable lateral load on the piston 3, the screw 13a, or the rack 13 during operation and could lead to their deflection.

[0048] Similarly, the raised central section 23 touches the upper surface of the bearing shell 17 when the piston 3 reaches the lower end of its stroke, as in Fig. 4 shown. Again, this arrangement ensures that if the piston 3 points slightly to one side during operation, the first contact point still remains relatively central, so that no undesirable lateral loads are exerted on the components.

[0049] When the piston 3 reaches the lower end of its stroke, it does not come into contact with the rods 10 due to the gap 12 between the rods 10 and the top of the bearing shell 17.

[0050] The arrangement of the springs 4 in two groups of three each ensures that the expansion forces exerted on the underside 5 of the piston 3 are evenly balanced. It is also advantageous due to its effective use of the space in the inner chamber area 8 around the rack 13 and the pinion 14.

[0051] Additionally, the use of six springs allows for a degree of flexibility, as two or four of the springs 4 can be removed to reduce the return spring force. Consequently, return forces of 689.48 Pa (100 psi), 551.584 Pa (80 psi), and 413.688 Pa (60 psi) can be easily provided with the same design. It is only necessary to remove the cover plate 9 and the piston 3 from the actuator 1 to access the springs 4 and then simply remove the desired number of springs 4. Naturally, the same spring force must be provided on each side of the rack 13 and the pinion 14 to ensure a consistently linear and balanced return spring force.

[0052] Consequently, a simple and practical design is provided in which the return springs 4 and the connecting elements 13, 14 are arranged on the same side of the piston 3. The main advantages of this are that space is saved, since there is no need to provide extra axial space to accommodate the compressed springs, as they are arranged axially in the same space as the rack 13 and the pinion 14, and that improved reliability is achieved, since only one pressure seal, namely the O-ring 26, is required to seal the pressure chamber 7.

[0053] Two further embodiments of the invention are described in Fig. 5 to 8 shown. (As explained above, show Fig. 5 and Fig. 7 (the piston and the cover plate are not shown for the sake of simplicity in explaining the invention.) In Fig. 5 and Fig. 6 is an actuator 50 constructed like the actuator 1 described above, except that the rods 51 are attached to the underside 52 of the piston 53, i.e. opposite the end 54 of the inner chamber area 55.

[0054] With reference to Fig. 6. The rods 51 are long enough to provide a gap 56 between them and the bottom 54 of the inner chamber area 55 when the piston 53 is in its lowest stroke position. Consequently, the rods 51 do not touch the bottom 54 of the inner chamber area 55 during operation.

[0055] In Fig. 7 and Fig. Figure 8 shows a functionally identical actuator 70 to the actuator 1 described above, but with a different physical construction. Instead of the inner chamber area being a free space housing the moving components of the actuator, the inner chamber area 71 of actuator 70 is machined from a single block. A body 72 is arranged within the inner chamber area 71, and the support means for the springs 73 comprise chambers 74 formed in the body 71. Consequently, the inner chamber "area" 71 in this case is a region of the block below the pressure chamber 75, as opposed to an actually open space. This region is described in Fig. 8 defined by a broken line.

[0056] Furthermore, this design eliminates the need for a bearing housing, as described above for actuator 1. Instead, the bearing chamber 76 is formed within the body 72, and the rack 77 is arranged therein. The arrangement of the rack rolling line and the bearing, described above with reference to actuator 1, is also applied to actuator 70.

[0057] To accommodate the pinion 78, a pinion recess 79 is formed laterally in the body 72 (in Fig. (7 shown with a dashed line). The pinion recess 79 does indeed overlap the two chambers 74a and 74b to a small extent, but the pinion 78 does not touch any of the springs 73.

[0058] Consequently, the actuator 70 operates in the same way as the actuators 1 and 50 described above, except that the springs 73 are supported from their outside instead of their inside, and fewer component parts are required.

[0059] During operation, the piston 80 contacts the upper end 81 of the body 72. As with the actuator 1 described above, the same arrangement of raised central sections of the piston 80 is used. Consequently, when the piston 80, as in Fig. As shown in Figure 8, when the upper end of its stroke has been reached, it is the raised central section 82 which touches the body 72.

[0060] The embodiments described above can be modified without falling outside the scope of claim 1. In particular, alternative arrangements (not shown) can provide a different number of springs than the six provided here, and they can be arranged in other ways. For example, two springs can be provided, each on one side of the rack and pinion.

[0061] In addition, in further alternative embodiments (not shown) the actuators can be adapted to provide more than a 90° rotation of the pinion, which is achieved by using different tooth arrangements between the rack and pinion.

[0062] Furthermore, in alternative embodiments (not shown), other gear and yoke arrangements can be provided between the rack and the pinion.

[0063] Consequently, an actuator is provided which features a simple and functional design that eliminates the need for external spring chambers and piston seals.

Claims

[1] Single-acting actuator (1) comprising a cylinder (2), a pressure chamber (7), a spring-return piston (3), and an inner chamber region (8) in which a rack (13) protrudes from the underside of the piston (3), and the rack (13) interacts with a rotatable pinion (14) arranged normal to the rack (13) in the inner chamber region (8), wherein the pitch line of the rack (13) is substantially aligned with the center of the piston (3), wherein one or more return springs (4) are arranged within the inner chamber region (8), and wherein the one or more return springs (4) are arranged on the same side of the piston (3) as the rack (13) and the pinion (14). [2] Actuator (1) according to claim 1, characterized by , that the diameter of the inner chamber area (8) is axially aligned with the diameter of the pressure chamber (7) defined by the cylinder (2). [3] Actuator (1) according to claim 2, characterized bythat the one or more return springs (4) have one or more coil springs which are substantially parallel to the cylinder (2). [4] Actuator (1) according to claim 3, characterized by , that the one or more return springs (4) are provided with support means adapted to support the one or more springs along part or their entire axial length. [5] Actuator (1) according to claim 4, characterized by that the support means have a rod (10) arranged within each of the one or more springs. [6] Actuator (1) according to claim 5, characterized by , that one or more rods (10) protrude from a base of the inner chamber area (8). [7] Actuator (1) according to claim 6, characterized by , that a gap (12) is provided between the one or more rods (10) and the lowest stroke position of the underside of the piston (3). [8] Actuator (1) according to claim 5, characterized by , that one or more rods (10) protrude from the underside of the piston (3) facing away from the pressure chamber (7). [9] Actuator (1) according to claim 8, characterized by , that a gap (12) is provided between the one or more rods (10) and a base of the inner chamber area (8) when the piston (3) is in its lowest stroke position. [10] Actuator (1) according to claim 4, characterized by , that a body is arranged within the inner chamber area (8) in which the support means have one or more chambers formed in the body, each being adapted to receive the one or more springs (4). [11] Actuator (1) according to claim 10, characterized by , that a gap (17) is provided between the body and the lowest stroke position of the underside of the piston (3). [12] Actuator (1) according to any of the preceding claims, characterized by, that a screw (13a) secures the rack (13) to the piston (3), wherein the screw (13a) is substantially aligned with the center of the piston (3). [13] Actuator (1) according to any one of claims 5 to 9 or according to claim 12 with reference to any one of claims 5 to 9, characterized by , that a bearing shell (17) is provided in the inner chamber area (8), which partially surrounds the rack (13), and wherein a bearing body is provided between the rack (13) and the bearing shell (17). [14] Actuator (1) according to any one of claims 10 to 11 or according to claim 12 with reference to claim 10 or 11, characterized by that the body has a bearing chamber in which the rack (13) is arranged, and wherein a bearing body is provided between the rack (13) and the bearing chamber. [15] Actuator (1) according to claim 13 or 14, characterized by , that the pinion (14) is attached to bearings at each end. [16] Actuator (1) according to claim 1, characterized by , that the diameter of the pinion body is smaller than the outer diameter of the pinion teeth provided on the pinion (14). [17] Actuator (1) according to any of the preceding claims, characterized by , that the piston (3) is provided with a raised central section at its bottom and a raised central section at its underside. [18] Actuator (1) according to claim 17, characterized by that the raised central sections are ring-shaped. [19] Actuator (1) according to any one of claims 3 to 18, characterized by , that six coil springs (4) are provided. [20] Actuator (1) according to claim 19, characterized by , that one or more of the six coil springs (4) can be removed from the actuator (1) so that the return spring force can be varied. [21] Actuator (1) according to claim 20, characterized by, that the six coil springs (4) provide essentially 689.48 Pa (100 psi) of return spring pressure, four of the six coil springs (4) provide essentially 551.584 Pa (80 psi) of return spring pressure, and two of the six coil springs (4) provide essentially 413.688 Pa (60 psi) of return spring pressure. [22] Actuator (1) according to any one of claims 19 to 21, characterized by , that the six coil springs (4) are arranged in two groups of three springs each, with each group being arranged on one side of a rack (13) projecting from the underside of the piston (3). [23] Actuator (1) according to claim 1, characterized by , that the movement of the piston (3) from its uppermost stroke position to its lowermost stroke position rotates the pinion (14) by essentially 90°. [24] Actuator (1) according to claim 23, characterized by that the pinion (14) has three or four teeth. [25] Actuator (1) according to any of the preceding claims, characterized by, that the actuator (1) is operated with pressurized fluid. [26] Actuator (1) according to any of the preceding claims, characterized by , that the actuator (1) is a valve actuator.

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