Linear actuator with exhaust of extension arm using check valve

Abstract

The invention relates to an actuator with a housing, an extension arm and a threaded spindle. The threaded spindle is rotatably mounted on the housing about its central axis. The extension arm movably extends out of the shell in the direction of the central axis. The housing and the extension arm collectively delimit an interior space, the volume of which varies as the extension arm moves. The end of the threaded spindle extends into the tubular section of the extension arm irrespective of the position of the extension arm. The tubular section extends about a central axis with a constant inner cross-sectional shape. The end of the threaded spindle is connected to a piston, which subdivides the interior space into a first region and a second region, which are demarcated from one another in a fluid-tight manner. The first region is entirely bounded by the piston and the extension arm. The second region is sealed in a fluid-tight manner relative to the environment. A check valve is disposed in the piston between the first region and the second region. The check valve allows fluid to enter the first region from the second region of the extension arm in a first direction and prevents fluid from passing in a second direction opposite the first direction.

Description

Technical Field

[0001] The present invention relates to a linear actuator with an exhaust device for its extension arm as described in the preamble of claim 1, such as a lifting cylinder. Background Art

[0002] (Electromechanical) linear actuators are generally known in the prior art. For example, DE102020212703A1 proposes that a threaded spindle drives a nut connected to a sleeve (Pinole) or an extension arm (Ausleger, cantilever), and the threaded spindle is arranged such that a piston at the end of the threaded spindle demarcates a first region and a second region in a fluid-tight manner. The first region is located in the sleeve, is completely filled with ambient air, and can be connected to the environment through an exhaust perforation. When the linear actuator moves rapidly, a whistling sound may occur at the exhaust perforation due to air flow. Especially when used in an external area, condensate is also formed in the first region, which may have an adverse effect on the service life. Therefore, it is desired to deviate from this teaching and completely enclose the first region. For this purpose, the first region must have a sufficient minimum volume so that when the linear actuator retracts and extends rapidly, the seal between the first region and the second region will not be overloaded due to pressure fluctuations.

[0003] The second region is a cavity partially filled with lubricating oil, and the threaded spindle is located therein. The threaded spindle is connected to the sleeve that functions as an extension arm. If the threaded spindle extends, the pressure in the second region will decrease, and if the threaded spindle retracts, the pressure will increase due to the extrusion of the spindle. A piston is provided at the end of the spindle for sealing relative to the extension arm. In addition, the extension arm is sealed relative to the housing of the linear actuator on its outer side using a second seal and is guided therein. The interior space of the housing is sealed airtight relative to the outside and is filled with a mixture of gas and liquid for cooling and lubrication. If the interior space is closed in the state where the extension arm is retracted, then a negative pressure will be formed when the extension arm extends. Conversely, if the fluid cannot be discharged well enough at the threaded nut, then an overpressure will be formed between the threaded spindle and the second seal when retracting again.

[0004] Since the overpressure in the first region and the negative pressure in the second region (or vice versa) occur simultaneously, it is inevitable that a small amount of lubricating oil will enter the first cavity past the piston seal from the second cavity because the second cavity is largely filled with oil, and thus pressure fluctuations also occur there when the electric cylinder moves. In addition, the lubricating oil in the second cavity moves violently because it has to flow through the threaded nut so that the electric cylinder can move. This flow restriction part and the movement of the threaded nut jointly promote the above-mentioned flow in the second cavity. When the seal wears, external leakage will occur.

[0005] In the opposite direction from the first region to the second region, since the pressure in the first region is below atmospheric pressure most of the time, there is little oil exchange or oil discharge. Over time, the lubricating oil accumulates in the first region. In extreme cases, if the lubricating oil cannot be discharged from the first region, it will limit the maximum possible movement distance of the electric cylinder. This will cause a pressure peak in the first region, which in turn will damage the floating bearing of the main shaft piston. Therefore, in the above prior art, a connection to the external air is provided to avoid pressure peaks. Summary of the Invention

[0006] Different from the above prior art in which the pressure peak is avoided by connecting to the external air, the task of the present invention is to lead the lubricating oil from the first cavity back to the second cavity, so that the electric cylinder always remains sealed in an airtight manner to the outside.

[0007] To solve this problem, the present invention proposes an actuator with a housing, an extension arm and a threaded spindle. The threaded spindle is rotatably supported on the housing about its central axis. The extension arm projects from the housing in a direction movable along the central axis. The housing and the extension arm together enclose an internal space whose volume changes when the extension arm moves. The end of the threaded spindle extends into the tubular section of the extension arm, regardless of the position of the extension arm. The tubular section extends around the central axis with a constant internal cross-sectional shape. The end of the threaded spindle is connected to a piston, which subdivides the internal space into a first region preferably filled only with gas and a second region preferably filled with a gas-liquid mixture, such that the first region and the second region are fluid-tightly separated from each other. The first region is completely bounded by the piston and the extension arm. The first region and the second region are (respectively) fluid-tightly sealed relative to the environment. A check valve is arranged in the piston between the first region and the second region, which allows fluid to enter the first region from the second region in a first direction and prevents fluid from passing through in a second direction opposite to the first direction.

[0008] Specifically, according to the present invention, it is realized that the internal space of the extension arm, which is substantially completely sealed relative to the environment when needed, is automatically exhausted. The exhaust of the extension arm is carried out by means of a check valve between the internal space of the extension arm and the holes or fluid channels in the piston and the main shaft in such a way that fluid can flow from the internal space of the extension arm to the holes in the piston in the first direction and prevent the fluid from flowing in the second direction opposite to the first direction. A preferred embodiment of the check valve includes an arched support disk, a diaphragm, and a piston cover. The support disk, the diaphragm, and the piston cover are engaged with each other in such a way that the support disk presses the diaphragm onto the piston cover. For this purpose, the support disk preferably has a pre-tightening force. The diaphragm and the piston cover each have through holes. In the assembled state, the through holes in the diaphragm are angularly offset relative to the through holes in the piston cover, that is, they are not aligned. In the first operating position, the internal space of the extension arm is sealed, while in the second / another operating position, the diaphragm is lifted from the piston cover to form a fluid connection between the through holes in the diaphragm and the through holes in the piston cover.

[0009] Since the inflexible (rigid) piston cover is located behind the hole in the diaphragm and the diaphragm is pressed in front of the hole in the piston cover, with such an arrangement, it is realized that the fluid pressure acting on the diaphragm from the direction of the support disk presses the diaphragm onto the piston cover, thereby strengthening the seal. Therefore, the fluid cannot easily pass through the diaphragm and the piston cover from the side of the support disk. Conversely, if the pressure in the extension arm increases, the pressure acts on the deformable diaphragm through the hole in the piston cover. The diaphragm is squeezed onto the piston cover by the pressure of the pre-tightened arched support disk, so that no fluid passes through when the pressure in the extension arm is low. Only when the fluid pressure through the hole in the piston cover exceeds the pre-tightening force of the support disk, the diaphragm will be lifted at the hole in the piston cover. Then, the fluid can pass through the piston cover, reach the holes in the lifted diaphragm, and further enter the space behind the support disk, that is, the side of the support disk facing the main shaft.

[0010] The support disk can be arched at least in its original state (i.e., the unmounted / unassembled state). In the mounted state, the crown is aligned in the direction of the diaphragm. If such a support disk is installed, the curvature will elastically become smaller during the installation process, so that the support disk exerts an elastic force on the diaphragm, and this elastic force squeezes or presses the diaphragm onto the piston cover. Therefore, by squeezing the diaphragm onto the piston cover, the above-mentioned function as a check valve can be simply generated.

[0011] The preferred support disk is arched even in the assembled state. Indeed, the support disk must establish a pre-tightening force in the assembled state, which can be suitably achieved by pressing the structures together during assembly to reduce the curvature. However, the curvature should not be reduced to zero, i.e., the support disk should be "flat" mounted, otherwise the support disk may "flip (Umschlagens)". Thus, the diaphragm will no longer be pressed against the piston head as expected by the support disk. If the curvature of the support disk remains unchanged even in the assembled state, it can prevent the support disk from "flipping" under the action of excessive pressure, thereby forming a support at an unexpected position, or even causing the support to fail due to the support disk lifting from the diaphragm, and further causing the valve action to fail.

[0012] The support disk, diaphragm, and piston head are preferably fixed together by at least one screw and fastened to the piston, or more generally to a member for internally sealing and / or guiding the extension arm. This structure is particularly easy to maintain because it can be easily disassembled while reliably fixing all components together in the assembled state. If a structure with a support disk, diaphragm, and piston head is used, the support disk preferably has recesses, such as punched holes. The recesses make it easier for the lubricating fluid returning from the first region or space to be further conveyed through the diaphragm. In addition, the spring force acting on the diaphragm can also be appropriately adjusted by means of such recesses, because the spring force can be reduced by reducing the arched and thus elastic bridging portion between the recesses. If such recesses are provided, it is beneficial that the through holes in the diaphragm are located on the recesses of the support disk in the assembled state, so as not to cause resistance to the further conveyance of the fluid. In this way, the diaphragm is deformed by the pressurized fluid from the first region, thereby further promoting the entry of the fluid into the second region, where the fluid can be used at a predetermined position, such as for lubrication and cooling.

[0013] In addition, the diaphragm is preferably connected to the support disk in a non-detachable manner or a non-detachable manner without destruction, such as by vulcanization. Vulcanization is a known inexpensive joining method that can be used for most materials of the diaphragm (and support disk). This preparation method facilitates (especially automated) final assembly because the support disk imparts strength to the diaphragm, and through this strength, the operation of the formed assembly is simplified.

[0014] For the present invention, it is also beneficial that the extension arm is guided on its inner side by the piston, especially by means of a guiding strip, and on its outer side by guiding means in the actuator housing. The guiding on the outer side of the extension arm can also be carried out by means of guiding strips, which is an economical and effective method to achieve low-friction movement between the two components. Seals provided between the corresponding guiding strips can prevent the fluid from flowing out, thereby ensuring the airtight sealing of the internal space of the actuator.

[0015] The present invention is used in an electromechanical linear actuator or simply "actuator" which has a housing closed in an airtight manner and an extension arm, and is used for exhausting the extension arm. In such a linear actuator, when the extension arm retracts, overpressure often appears on the side of the extension arm, and when the extension arm extends, negative pressure often appears on the side of the extension arm. Since the two regions are demarcated in an airtight manner, the negative pressure will not transport fluid to the first region when extending. Due to the adoption of the present invention, when the extension arm retracts, the overpressure in the extension arm can also be used to send the fluid that accidentally enters the first region back to the second region. Therefore, the fluid that enters the extension arm during operation reliably returns again through the exhaust of the extension arm when the extension arm retracts. Description of the Drawings

[0016] Figure 1 is an exploded view of an extension arm exhaust device in a linear actuator according to a first embodiment of the present disclosure;

[0017] Figure 2 shows an isometric top view of a piston base on which an extension arm exhaust device is provided;

[0018] Figure 3 The piston cap of the extension arm exhaust device is shown as a separate component;

[0019] Figure 4 The diaphragm of the extension arm exhaust device is shown as a separate component; and

[0020] Figure 5 is a separate component view of a support disk of the extension arm exhaust device. Detailed Description of the Embodiment

[0021] An embodiment of the present disclosure will be described below with reference to the drawings.

[0022] As can be seen from Figure 1 , the exhaust device 1 of the extension arm 5 shown in the intercepted part of the linear actuator with the housing 17 in the figure is designed as a check valve, which includes a support disk 9, a diaphragm 10 and a piston cap 11 from left to right in the figure. These components are fastened to the piston 2 of the linear actuator by screws 14 (four in this example, only three are shown due to the cross-sectional view), thereby sealing the first region 4.1 ( Figure 1 on the left side of the piston or sliding piston 2, in the direction of arrow "A") and the second region 4.2 (on the "right side" of the piston 2, in the direction of arrow "E") in the extension arm 5 in an airtight manner. Here, the first region 4.1 is only demarcated by the piston 2 and the extension arm 5.

[0023] The support disk 9 is arched in its original shape (see in detail Figure 5), it is pre-tightened by being assembled on the piston 2 using screws 14. In the embodiment explained above, the support disk has screw through-holes 18 for this purpose. In addition, notches between the bridging pieces can also be seen on the support disk 9, and these notches fix the middle part and the outer ring of the support disk together. In this embodiment, the diaphragm 10 (see Figure 4 ) is applied to the support disk 9, for example, vulcanized. However, in principle, the diaphragm can also be "loosely" clamped between the support disk 9 and the piston cover described below. The diaphragm 10 has a first through-hole 13. In addition, in the embodiment described above, screw through-holes 19 are also provided on the diaphragm, and they are aligned with the holes 18 in the support disk 9 in the installed state.

[0024] Figure 3 The piston cover 11 shown in has second through-holes 12, and they are arranged offset from the first through-holes 13 passing through the diaphragm 10. In addition, screw through-holes 20 are provided here, and they are aligned with the screw through-holes 18 and 19 in the support disk 9 and the diaphragm 10 in the installed state. The screws 14 are screwed into the threaded holes in the piston through these screw through-holes 18 to 20, and the support disk 9, the diaphragm 10 and the piston cover 11 are fastened to the piston 2 by them. If the support disk 9 and the diaphragm 10 are pressed tightly against the piston cover 11 by tightening, then despite the presence of the through-holes 12, 13, a sealing effect can still be achieved because the through-holes 12, 13 are offset from each other in terms of angle. In addition, the pre-tightening force of the support disk 9 presses the diaphragm 10 against the piston cover 11. Therefore, the first region 4.1 and the second region 4.2 in the extension arm 5 are generally sealed relative to each other.

[0025] If the sleeve 5 retracts along the second direction (retraction direction) E, especially at a high speed, the pressure in the first region 4.1 that is hermetically sealed in the extension arm 5 increases. Therefore, the pressure acting on the diaphragm 10 also increases through the through-hole 12 on the piston cover 11. If the pressure acting on the diaphragm 10 exceeds the pre-tightening force acting against this pressure through the support disk 9, especially if an incompressible fluid enters the first region 4.1, the diaphragm 10 will be lifted. In this way, the lubricating fluid, especially the incompressible fluid that "accidentally" enters the first region 4.1 (the internal space of the extension arm 5 on the side of the piston 2 where the support disk 18 is located), can flow along the retraction direction "E" of the extension arm 5, thus ensuring pressure balance. Therefore, even if the incompressible lubricating fluid in the hermetically sealed extension arm 5 prevents the extension arm 5 from retracting, the extension arm 5 can still retract completely. The lubricating fluid can continue to flow through the hole 6 and the groove 7 in the piston 2, and then reach the longitudinal channel in the threaded main shaft (abbreviation "main shaft") 3 of the longitudinal actuator and / or the second region 4.2 in the pipe, so as to be able to continue lubricating and cooling the actuator.

[0026] When the extension arm 5 extends in the first direction (extending direction) A, the above pressure relationship is reversed. Thus, the diaphragm 10 is pressed against the fixed piston head 11 by the pre-tensioning force of the support disk 9 and also by the relative overpressure of the lubricating fluid (in the first direction A; Figure 1 from left in the figure). As a result, the sealing effect is enhanced, and the fluid cannot enter the inner space 4 of the sleeve on the other side of the piston head 11 through the piston seal. Instead, the fluid is used elsewhere, for example, is guided past the spindle nut (not shown here) and / or through the spindle drive (also not shown) so that effective lubrication and cooling can be carried out here.

[0027] In this way, the exhaust device 1 of the extension arm 5 acts as a check valve. Compared with traditional spherical or conical check valves (which can also be installed in the piston 2 to achieve a similar effect), the solution of this embodiment is very flat (flach). In addition, the diaphragm valve-based exhaust device 1 of the extension arm 5 has a better backflow effect than, for example, a traditional spring seat valve as a check valve because it is sensitive to pressure differences. Even if the linear actuator moves back and forth quickly, reverse fluid flow can be avoided, and the fluid can flow in the desired direction.

[0028] Finally, returning again to Figure 1 It can be seen that the check valve according to the invention can cooperate particularly advantageously with the guiding device of the extension arm 5 in the actuator, wherein with the aid of the guiding strip 16, the extension arm 5 is guided not only on its outer side in the end portion (Abschluss) of the housing 17, but also on its inner side on the piston 2. The guiding strip 16 is provided in the corresponding grooves in the piston 2 and in the end portion of the housing 17, which provides low-friction guiding for the extension arm on the housing 17 and the piston 2. In addition, such guiding strips come in various sizes and are inexpensive, so they can be used for actuators of various sizes, saving costs compared with other methods of manufacturing low-friction sliding surfaces.

[0029] In summary, the present invention discloses an actuator with a housing 17, an extension arm 5, and a threaded spindle 3. The threaded spindle 3 is rotatably supported about its central axis on the housing 17. The extension arm 5 projects from the housing 17 in a displaceable manner along the central axis direction. The housing 17 and the extension arm 5 jointly enclose defined internal spaces 4.1, 4.2, and the volume of the internal space changes when the extension arm 5 moves. The end of the threaded spindle 3 extends into the tubular section of the extension arm 5, regardless of the position of the extension arm 5. The tubular section extends about the central axis with a constant internal cross-sectional shape. The end of the threaded spindle 3 is connected to a piston 2, and the piston 2 subdivides the internal space into a first region 4.1 and a second region 4.2. The first and second regions 4.1, 4.2 are fluid-tightly bounded from each other. The first region 4.1 is bounded only by the piston 2 and the extension arm 5. The second region 4.2 is sealed in a fluid-tight manner relative to the surrounding environment. Check valves 9, 10, 11 are arranged in the piston 2 between the first region 4.1 and the second region 4.2. The check valves allow fluid to enter the first region 4.1 of the extension arm 5 from the second region 4.2 in a first direction E and prevent fluid from passing through in a second direction A opposite to the first direction.

Claims

1. Actuator with housing (17), extension arm (5) and threaded spindle (3), in, The threaded spindle (3) is supported on the housing (17) so as to be rotatable about its center axis. The extension arm (5) is movably extended from the housing (17) along the direction of the central axis. The housing (17) and the extension arm (5) together surround and bound an internal space (4.1, 4.2); when the extension arm (5) moves, the volume of the internal space changes. The end of the threaded spindle (3) extends into the tubular section of the extension arm (5), regardless of the position of the extension arm (5). The tubular section extends around the central axis with a constant internal cross-sectional shape, the end of the threaded spindle (3) is connected to a piston (2), and the piston (2) subdivides the internal space (4.1, 4.2) into a first area (4.1) and a second area (4.2), so that the first area and the second area (4.1, 4.2) are mutually delimited in a fluid-tight manner, wherein the first region (4.1) is completely bounded by the piston (2) and the extension arm (5), and the first region (4.1) is sealed in a fluid-tight manner relative to the environment; wherein the second region (4.2) is also sealed in a fluid-tight manner relative to the environment; and A check valve (9, 10, 11) is arranged in the piston (2) between the first area (4.1) and the second area (4.2), wherein the check valve allows fluid to enter the first area (4.1) from the second area (4.2) of the extension arm (5) along a first direction (E) and prevents the fluid from passing along a second direction (A) opposite to the first direction.

2. The actuator according to claim 1, wherein: The check valve (9, 10, 11) comprises a support disk (9), a diaphragm (10) and a piston cover (11), wherein the support disk (9) presses the diaphragm (10) onto the piston cover (11) so that in a first operating position, the inner space (4) of the sleeve (5) is sealed, and in a second / other operating position, the diaphragm (10) is removed from the piston cover (11) to enable a fluid connection between a through hole (13) in the diaphragm (10) and a through hole (12) in the piston cover (11).

3. The actuator according to claim 2, wherein: The support disk (9) has a preload force which presses the diaphragm (10) onto the piston cover (11).

4. The actuator according to claim 2 or 3, wherein: The support plate (9) is arched in an original state, and the arch top is aligned in the direction of the diaphragm (10) in the installed state.

5. The actuator according to claim 4, wherein: The support plate (9) is still arched in the assembled state.

6. The actuator according to any one of claims 2 to 5, wherein: The support plate (9), the diaphragm (10) and the piston cover (11) are fixed together by at least one screw (14) and fastened to the piston (2).

7. The actuator according to any one of claims 2 to 6, wherein: The support plate (9) has a recess (15).

8. The actuator according to claim 7, wherein: The through hole (13) in the diaphragm (10) is located on the recess (15) of the support disk (9) in the assembled state.

9. The actuator according to any one of claims 2 to 8, wherein: The diaphragm (10) is connected to the support disc (9) in a manner that cannot be removed without destruction, in particular vulcanized to the support disc (9).

10. Actuator according to any one of the preceding claims, wherein: The extension arm (5) is guided on its inner side by the piston (2), in particular by means of a guide belt (16), and on its outer side by a guide device in the housing (17) of the actuator.

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