Hollow screw

Abstract

Hollow screw,- with a shaft (2) having an external thread (6) on the outside and a cavity (7) on the inside,- with a head (3) arranged at a first longitudinal end (8) of the shaft (2) and having a torque introduction contour (9),- with a throttling element (4) for throttling a flow through the cavity (7) with a fluid,- wherein the shaft (2) has an axial opening (15) at its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the shaft (2) has at least one radial opening (16) axially spaced from its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the throttling element (4) is adjustable relative to the shaft (2) between a first throttling position (DSI) and a second throttling position (DSII), which differ from each other by different throttling effects,- wherein the throttle element (4) is arranged linearly adjustably on or in the shaft (2) along a longitudinal central axis (5) of the shaft (2), characterized in that the throttle element (4) is arranged linearly adjustably on or in the shaft (2) such that in the first throttle position (DSI) the throttle element (4) is arranged in the cavity (7) or directly at the axial opening (15), while in the second throttle position (DSII) the throttle element (4) is arranged outside the cavity (7) and axially spaced from the axial opening (15).

Description

The present invention relates to a hollow screw according to the preamble of claim 1. A conventional hollow screw is known, for example, from GB 15 66 254 A. Such a hollow screw has a shank with an external thread on the outside and a cavity on the inside. Furthermore, the hollow screw has a head that is fixedly arranged at a first longitudinal end of the shank and has a torque introduction contour. Finally, such a hollow screw is equipped with a throttling element that serves to restrict the flow of fluid through the cavity. To enable such flow through the cavity, the shank has, at its second longitudinal end, an axial opening fluidically connected to the cavity and at least one radial opening fluidically connected to the cavity, which is axially spaced from the second longitudinal end of the shank.When the hollow screw is installed, a corresponding pressure difference between the axial opening and the respective radial opening can cause the aforementioned flow of fluid through the cavity, whereby this flow is throttled by the throttling element. A similar hollow screw with an integrated throttle element is known from JP 2015-051 393 A. A hollow screw of this type is known from DE 10 2012 104 286 A1 and differs from the conventional hollow screw mentioned above in that the throttle element is adjustable relative to the shaft between a first throttle position and a second throttle position, which differ in their throttling effects. In the known hollow screw, the throttle element is also arranged on or in the shaft so that it is linearly adjustable along a longitudinal axis of the shaft, and the shaft has a linear guide for the guided linear adjustment of the throttle element. With conventional hollow screws, the throttling effect of the restrictor is independent of the flow direction through the cavity. However, applications are conceivable where a different throttling effect is desired in one flow direction than in another. This creates a conflict of objectives in such applications that cannot be resolved with conventional hollow screws. Applications are also conceivable where the flow is to be throttled more or less depending on the differential pressure between the axial and radial openings. For example, it may be necessary to reduce the throttling effect at particularly high differential pressures to prevent damage to a machine. A varying throttling effect depending on the flow direction may be desirable, for example, to deliberately create a hysteresis effect. The present invention addresses the problem of providing an improved embodiment of a hollow screw of the type described above, which is characterized in particular by a variable throttling effect. Preferably, an embodiment in which the throttling effect depends on the flow direction may also be sought. This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims. The invention is based on the general concept of designing or arranging the throttle element to be adjustable relative to the shaft between a first throttle position and a second throttle position, with the two throttle positions differing from each other by their different throttling effects. The adjustability of the throttle element allows the flow conditions at the throttle element to be influenced relatively easily through the interaction of relevant contours. For example, it is conceivable that when adjusting from one throttle position to the other, a bypass is progressively opened or closed, allowing flow to bypass or circumvent the throttle element. Thus, the throttling effect can be easily influenced to achieve the required different states for the desired application.These two throttle positions are preferably configured as end positions for the throttle element, between which the throttle element is adjustable. These end positions limit the maximum possible adjustment range of the throttle element relative to the shaft. In this case, the throttle element can adjust freely between the end positions, but not beyond them. According to an advantageous embodiment, the throttling element can be arranged on or in the shaft such that it is adjustable depending on a pressure difference between the axial opening and the respective radial opening relative to the shaft. This means that the pressure difference is used to drive the throttling element, enabling it to be adjusted between the first and second throttling positions. Thus, no additional external measures are required to adjust the throttling element and thereby change the throttling effect. According to another advantageous embodiment, the throttling element can be arranged on or in the shaft such that it can assume any intermediate position between the first and second throttling positions. These additional throttling positions can, in particular, be associated with further different throttling effects, preferably within a range that is bounded above and below by the two throttling effects present in the first and second throttling positions. Another embodiment proposes arranging the throttling element on or in the shaft such that, in the event of overpressure at the axial opening relative to the respective radial opening, it is driven to adjust relative to the shaft in the direction of the first throttling position, while in the event of overpressure at the respective radial opening relative to the axial opening, it is driven to adjust relative to the shaft in the direction of the second throttling position. This measure ensures that the throttling effect of the hollow screw depends on its flow direction. An advantageous embodiment involves pre-tensioning the throttling element to the first throttling position by means of a spring. This ensures that, below a threshold value for the differential pressure between the axial opening and the respective radial opening, the throttling element is driven and adjusted to the first throttling position by the spring. Furthermore, this has the effect of allowing the throttling element to be adjusted towards the second throttling position against the pre-tension force of the spring. According to another embodiment, the throttling element can be designed as a sieve, a filter, or a pinhole aperture. In particular, this allows an additional function, namely a filtration effect, to be integrated into the throttling element. Another embodiment proposes that the throttling element allows fluid to flow through the cavity in both the first and second throttle positions. This design prevents the cavity from being completely closed and thus prevents the flow from being blocked. In a first hollow screw according to the invention and in a second hollow screw according to the invention, the throttle element is arranged on or in the shaft so as to be linearly adjustable along a longitudinal central axis of the shaft. Such linear adjustability is particularly easy to implement, which enables cost-effective manufacturing of the hollow screw. In the second hollow screw according to the invention, the shaft has a linear guide for guided linear adjustment of the throttle element. This linear guide has a guide rod fixedly connected to the shaft, in particular centrally arranged, which extends coaxially and, in particular, concentrically to the longitudinal center axis of the shaft. The linear guide also has a guide opening formed on the throttle element, which is in particular centrally arranged, through which the guide rod extends, so that the throttle element is mounted on the guide rod and guided linearly along the guide rod. The aforementioned spring can, for example, extend concentrically around this guide rod in the form of a helical spring.Additionally or alternatively, the linear guide can be formed by a guide contour projecting radially from the throttle element, which interacts with a complementary counter-guide contour formed radially inside the shaft and projecting into the cavity. For example, the guide contour and counter-guide contour can interact in the manner of a tongue-and-groove guide. In the first hollow screw according to the invention, the throttling element is arranged on or in the shaft in such a way that, in the first throttling position, the throttling element is located in the cavity or directly adjacent to the axial opening, while in the second throttling position, the throttling element is located outside the cavity and axially spaced from the axial opening. It is particularly conceivable that, in the first throttling position, the throttling element completely fills the flowable cross-section of the cavity, so that the entire fluid flow must pass through the throttling element. In the second throttling position, on the other hand, the axial distance of the throttling element from the axial opening creates an annular gap between the axial opening and the throttling element, thus allowing the fluid to flow around the throttling element.In other words, in this embodiment, at least in the second throttle position, a bypass is opened to circumvent the throttle element, thereby significantly reducing the throttling effect. In a third hollow screw according to the invention, the throttle element is arranged in or on the shaft so as to be rotatable about a longitudinal central axis of the shaft. By means of such a rotatable adjustment of the throttle element, it is particularly easy to set virtually any intermediate position, in order to be able to set virtually any number of varying throttle effects that lie between the first throttle effect acting in the first throttle position and the second throttle effect acting in the second throttle position. This rotatable adjustability of the throttle element can be provided in addition to or as an alternative to the linear adjustability of the throttle element described above. A particularly advantageous design is one in which the throttle element is constructed in two parts, comprising a rotatable, adjustable mobile throttle section and a stationary throttle section that is fixed to the shaft. This allows the throttle resistance to be adjusted or changed relatively easily by rotating the mobile throttle section relative to the stationary throttle section. Another refinement proposes that the mobile and stationary throttle components each have at least one eccentric axial through-opening. In the first throttle position, the through-openings of the two throttle components are axially aligned relative to each other, while in the second throttle position, this axial overlap is reduced or eliminated, i.e., absent. By rotating the mobile throttle component relative to the stationary throttle component, the axial overlap of the through-openings can be varied between maximum overlap with the lowest flow resistance and minimal, or even nonexistent, overlap with maximum flow resistance. This simplifies the adjustment of varying flow resistances, i.e., throttling effects. Another further development proposes that the movable throttle element be guided in a rotatable manner on a spindle formed within the cavity or on an internal thread formed within the cavity. This achieves a defined rotational adjustability for the movable throttle element. Accordingly, in the case of a one-piece throttle element, the throttle element can be guided in a rotatable manner on the aforementioned spindle or on the aforementioned internal thread. In conjunction with the spindle or the internal thread, the rotational adjustment of the throttle element or the movable throttle element is accompanied by a linear adjustment of the throttle element or the movable throttle element. The aforementioned spring can also be arranged, for example, coaxially and concentrically to the spindle and enclose it. In another advantageous embodiment, the mobile throttle element can be axially spaced from the stationary throttle element in the first throttle position, while in the second throttle position, the mobile throttle element rests axially against the stationary throttle element. In this case, the stationary throttle element essentially serves as an end stop for the adjustability of the mobile throttle element. In principle, the mobile and stationary throttle elements can be coordinated such that the passage openings are completely closed in the second throttle position. In particular, it can be provided that in the second throttle position, the two throttle elements are axially abutting each other, and there is no longer any overlap between the passage openings. The flowable cross-section of the cavity is then completely blocked. Alternatively, an embodiment is preferred in which the mobile and stationary throttle elements are designed and coordinated such that they do not completely close the flowable cross-section of the cavity even in the second throttle position. It is conceivable that the axial overlap of the passage openings is not completely eliminated in the second throttle position, so that a minimum or residual overlap can always be ensured.It is also conceivable that both throttle parts can be bypassed by a permanent bypass, which could, for example, be formed on the inside of the shaft. Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings. It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention. Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components. Figure 1 shows a highly simplified, circuit diagram-like schematic representation of a hollow screw in its installed state at a first throttle position, Figure 2 shows a view as in Figure 1, but at a second throttle position, Figure 3 shows a view as in Figure 1, but at a different embodiment, and Figure 4 shows an axial view of the hollow screw corresponding to a viewing direction IV in Figure 3. As shown in Figures 1, 2 to 3, a hollow screw 1 comprises a shank 2, a head 3, and a throttle element 4. The shank 2 has a longitudinal center axis 5, which defines an axial direction. The axial direction extends parallel to the longitudinal center axis 5. The radial direction extends perpendicular to the axial direction. The circumferential direction revolves around the longitudinal center axis 5. The shaft 2 has an external thread 6 on its radial outer surface and a cavity 7 on its radial inner surface. The head 3 is fixedly arranged at a first longitudinal end 8 of the shaft 2 and has a torque introduction contour 9. Here, the torque introduction contour 9 is designed as an external polygon. In principle, it could also be an internal polygon or any other contour suitable for introducing torque into the screw 1. The throttling element 4 serves to restrict the flow of fluid through the cavity 7. Such a flow can occur when the hollow screw 1 is installed. Figures 1, 2 to 3 show a possible, but purely exemplary, installation state in which the hollow screw 1, with its external thread 6, is screwed into a first component 10, passing through a second component 11 and securing it to the first component 10. The first component 10 defines a space 12. The second component 11 contains a channel 13. A fluid, in particular a liquid, can be supplied to or discharged from the space 12 via the channel 13. The supply and discharge of the fluid occurs through the cavity 7 of the hollow screw 1. The resulting flow is restricted by means of the throttling element 4. For this fluidic coupling of channel 13 with space 12 by the hollow screw 1 orThrough its cavity 7, the shaft 2 has an axial opening 15 at its second longitudinal end 14, furthest from the head 3. This opening is fluidically connected to the cavity 7 and is open to the space 12. Furthermore, the shaft 2 has at least one radial opening 16 axially spaced from its second longitudinal end 14. This radial opening is fluidically connected to the cavity 7 and is also open to the channel 13. The throttle element 4 is adjustable relative to the shaft 2 between a first throttle position DSI, shown in Figs. 1 and 3, and a second throttle position DSII, shown in Fig. 2. The two throttle positions DSI and DSII differ in their throttling effects. In the embodiment shown in Figs. 1 and 2, a variant is implemented in which the throttling effect is greater in the first throttle position DSI than in the second throttle position DSII. In the embodiment shown in Figs. 3 and 4, however, this can be reversed, so that the first throttle position DSI has a lesser throttling effect than the second throttle position DSII. In the embodiments shown here, the throttling element 4 is arranged on or in the shaft 2 such that it is adjusted relative to the shaft 2 depending on a pressure difference between the axial opening 15 and the respective radial opening 16. Thus, the flow resistance or throttling effect can be adjusted or varied, in particular depending on the differential pressure between the axial opening 15 and the respective radial opening 16, i.e., in the installed state, depending on the pressure difference between the chamber 12 and the channel 13. The pressure prevailing in the chamber 12 or at the axial opening 15 is denoted by Pa in Figures 1, 2 to 3. The pressure prevailing in the channel 13 or at the radial openings 16, on the other hand, is denoted by Pr. Furthermore, at least in the embodiment shown in Figs. 1 and 2, the throttling element 4 is driven in the direction of the first throttling position DSI when there is an overpressure at the axial opening 15 relative to the respective radial opening 16, i.e., when Pa > Prin. In this case, there is a flow through the cavity 7 from the chamber 12 towards the channel 13, i.e., from the axial opening 15 to the radial openings 16. This flow is indicated by arrows in Fig. 1. In contrast, under reversed pressure conditions, i.e., when there is an overpressure at the respective radial opening 16 relative to the axial opening 15 or when there is an overpressure in the channel 13 relative to the chamber 12, i.e., when Pa < Prin, the throttling element 4 is axially adjusted towards the second throttling position DSI. As a result, the cavity 7 flows from channel 13 to space 12, i.e., from radial openings 16 to axial opening 15, as shown in Fig.2 is also indicated by arrows. In the embodiments shown here, the throttle element 4 is pre-tensioned to the first throttle position DSI by means of a spring 17. The spring 17 is designed here as a helical compression spring. In principle, other springs 17 are also conceivable. The throttle element 4 can be designed as a sieve or filter, or, as shown in Fig. 4, as a perforated aperture. Furthermore, it is preferred that the throttle element 4 allows fluid to flow through the cavity 7 in both the first throttle position DSI and the second throttle position DSI. Complete blockage of the flowable cross-section of the cavity 7 should be avoided in the embodiments shown here. In all embodiments shown here, the throttle element 4 is arranged linearly adjustable along the longitudinal central axis 5 on or in the shaft 2. In the embodiment shown in Fig. 1 and Fig. 2, a linear guide 18 is provided for the linear adjustability of the throttle element 4, which enables a guided linear adjustment of the throttle element 4 relative to the shaft 2. The linear guide 18 comprises a guide rod 19 and a guide opening 20. The guide rod 19 is arranged concentrically and coaxially with the longitudinal center axis 5 in the cavity 7 and can be fixed, for example, at the head 3 or at the first longitudinal end 8. The guide rod 19 penetrates the guide opening 20, which is formed concentrically in the throttle element 4. This allows the throttle element 4 to be guided linearly and adjustably on the guide rod 19. An axial end stop 21 can be formed on the guide rod 19, as shown in Figures 1 and 2, which limits the axial adjustability of the throttle element 4 along the guide rod 19 in a direction away from the head 3. Simultaneously, the second throttle position DSII can be defined using the axial stop 21. The second throttle position DSII thus forms an end position for the adjustability of the throttle element 4.The first throttle position DSI can also be designed as an end position, especially with the aid of a further axial stop not shown here, e.g. in the form of a ring step inside the shaft 2. In the embodiment shown in Figures 1 and 2, the throttling element 4 is arranged on or in the shaft 2 so that it is linearly adjustable such that in the first throttling position DSI, the throttling element 4 is located in the cavity 7, while in the second throttling position DSII, it is located outside the cavity 7 and axially spaced from the axial opening 15. This results in a radial gap 22 being opened between the second longitudinal end 14 and the throttling element 4 in the second throttling position DSII, allowing flow to bypass the throttling element 4. Thus, the flow resistance or throttling effect is significantly reduced in this case for the second throttling position DSII. In the example shown here, the throttling element 4 is located inside the cavity 7 in the first throttling position DSI in order to fill the flowable cross-section of the cavity 7.In another embodiment, it can be provided that the throttle element 4 in the first throttle position DSIaxially rests against the second longitudinal end 14 and thereby completely covers the axial opening 15. In the other embodiment shown in Figs. 3 and 4, the throttle element 4 is arranged in or on the shaft 2 so as to be rotatably adjustable about the longitudinal central axis 5. For this purpose, according to an advantageous embodiment, the throttle element 4 can be designed in two parts, comprising a mobile throttle part 23 and a stationary throttle part 24. The mobile throttle part 23 is rotatably adjustable relative to the shaft 2, while the stationary throttle part 24 is fixedly arranged on the shaft 2. The mobile throttle part 23 and the stationary throttle part 24 each have at least one eccentric axial through-opening 25. In the example shown in Fig. 4, and purely by way of illustration and without limiting the generality, exactly four such through-openings 25 are formed on both the mobile throttle part 23 and the stationary throttle part 24. In the view of Fig.Figure 4 shows the mobile throttle element 23 behind the stationary throttle element 24 and is therefore not visible. The associated through-openings 25 are therefore partially shown with a dashed line. In the first throttle position DSI, the through-openings 25 of the two throttle elements 23 and 24 are aligned in axial overlap. This axial overlap is changed by a rotational adjustment of the mobile throttle element 23 relative to the stationary throttle element 24, indicated by a double arrow and labeled 26 in Figure 4. When the throttle element 4 is adjusted to the second throttle position DSII, this axial overlap is reduced until there is no overlap or only a minimal overlap. For the rotary adjustability of the throttle element 4 or the mobile throttle part 23, a spindle 27 can be arranged in the cavity 7 as shown in Fig. 3. The spindle 27 has an external thread (not specified in detail) on its outer surface and penetrates the mobile throttle part 23 in a complementary threaded opening 28, so that an axial adjustment of the mobile throttle part 23 necessarily results in a rotary adjustment of the mobile throttle part 23. Alternatively, instead of such a spindle 27, the shaft 2 can also have an internal thread (not specified in detail) on its inner surface, i.e., in the cavity 7, which interacts with a complementary external thread formed on the outer circumference of the throttle element 4 or the mobile throttle part 23. Here, too, an axial adjustment of the mobile throttle part 23 necessarily leads to a rotary adjustment of the mobile throttle part 23.An axial adjustment of the mobile throttle element 23 can occur when there is a corresponding pressure difference between chamber 12 and channel 13, or between axial opening 15 and radial openings 16. For example, an overpressure at the radial openings 16 relative to the axial opening 15, i.e., at Pr> Padas, drives the mobile throttle element 23 towards the stationary throttle element 24, which then leads to a corresponding rotation of the mobile throttle element 23 relative to the stationary throttle element 24. This rotational adjustment 26 then changes the overlap of the passage openings 25 and thus varies the flow resistance and therefore the throttling effect. As shown in Fig. 3, the movable throttle part 23 is axially spaced from the stationary throttle part 24 in the first throttle position DSI. In the second throttle position DSII, which is not shown here, the movable throttle part 23 can come into axial contact with the stationary throttle part 24. In this case, the spring 17 is tensioned. With a two-part throttle element 4, it is also conceivable that the spring 17 is arranged axially between the two throttle parts 23, 24. It is also conceivable that there are two springs: one as shown in Fig. 3 and another that is supported by both throttle parts 23, 24, i.e., arranged between the two throttle parts 23, 24. It is also preferred that, in the case where the two throttle parts 23, 24 are in axial contact with each other in the second throttle position DSII, the flowable cross-section of the cavity 7 is not completely blocked, i.e., closed. For this purpose, a minimum overlap of the passage openings 25 can be ensured, for example. It is also conceivable that a permanently open bypass is provided for the throttled circumvention of both throttle parts 23, 24, for example in the form of at least one longitudinal groove formed on the inside of the shaft 2 and / or in the form of at least one longitudinal groove formed on the outer circumference of the throttle parts 23, 24.

Claims

Hollow screw,- with a shaft (2) having an external thread (6) on the outside and a cavity (7) on the inside,- with a head (3) arranged at a first longitudinal end (8) of the shaft (2) and having a torque introduction contour (9),- with a throttling element (4) for throttling a flow through the cavity (7) with a fluid,- wherein the shaft (2) has an axial opening (15) at its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the shaft (2) has at least one radial opening (16) axially spaced from its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the throttling element (4) is adjustable relative to the shaft (2) between a first throttling position (DSI) and a second throttling position (DSII), which differ from each other by different throttling effects,- wherein the throttle element (4) is arranged linearly adjustably on or in the shaft (2) along a longitudinal central axis (5) of the shaft (2), characterized in that the throttle element (4) is arranged linearly adjustably on or in the shaft (2) such that in the first throttle position (DSI) the throttle element (4) is arranged in the cavity (7) or directly at the axial opening (15), while in the second throttle position (DSII) the throttle element (4) is arranged outside the cavity (7) and axially spaced from the axial opening (15). Hollow screw,- with a shaft (2) having an external thread (6) on the outside and a cavity (7) on the inside,- with a head (3) arranged at a first longitudinal end (8) of the shaft (2) and having a torque introduction contour (9),- with a throttling element (4) for throttling a flow through the cavity (7) with a fluid,- wherein the shaft (2) has an axial opening (15) at its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the shaft (2) has at least one radial opening (16) axially spaced from its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the throttling element (4) is adjustable relative to the shaft (2) between a first throttling position (DSI) and a second throttling position (DSII), which differ from each other by different throttling effects,- wherein the throttle element (4) is arranged linearly adjustable along a longitudinal central axis (5) of the shaft (2) on or in the shaft (2), - wherein the shaft (2) has a linear guide (18) for guided linear adjustment of the throttle element (4), characterized in that the linear guide (18) has a guide rod (19) fixedly connected to the shaft (2) and a guide opening (20) formed on the throttle element (4) and penetrated by the guide rod (19). Hollow screw,- with a shaft (2) having an external thread (6) on the outside and a cavity (7) on the inside,- with a head (3) arranged at a first longitudinal end (8) of the shaft (2) and having a torque introduction contour (9),- with a throttling element (4) for throttling the flow of fluid through the cavity (7),- wherein the shaft (2) has an axial opening (15) at its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the shaft (2) has at least one radial opening (16) axially spaced from its second longitudinal end (14) which is fluidically connected to the cavity (7),- wherein the throttling element (4) is adjustable relative to the shaft (2) between a first throttling position (DSI) and a second throttling position (DSII), which differ from each other by different throttling effects, characterized in that- that the throttle element (4) is arranged in or on the shaft (2) so as to be rotatable about a longitudinal central axis (5) of the shaft (2). Hollow screw according to one of claims 1 to 3, characterized in that the throttle element (4) is arranged on or in the shaft (2) in such a way that it is adjustable depending on a pressure difference between the axial opening (15) and the respective radial opening (16) relative to the shaft (2). Hollow screw according to one of the preceding claims, characterized in that the throttle element (4) is arranged on or in the shaft (2) such that, in the event of overpressure at the axial opening (15) relative to the respective radial opening (16), it is driven to adjust relative to the shaft (2) in the direction of the first throttle position (DSI), while in the event of overpressure at the respective radial opening (16) relative to the axial opening (15), it is driven to adjust relative to the shaft (2) in the direction of the second throttle position (DSII). Hollow screw according to one of the preceding claims, characterized in that the throttle element (4) is pre-tensioned to the first throttle position (DSI) by means of a spring (17). Hollow screw according to one of the preceding claims, characterized in that the throttling element (4) is designed as a sieve or filter or aperture. Hollow screw according to one of the preceding claims, characterized in that the throttle element (4) allows the fluid to flow through the cavity (7) both in the first throttle position (DSI) and in the second throttle position (DSII). Hollow screw according to one of claims 1 and 4 to 8, characterized in that the shaft (2) has a linear guide (18) for guided linear adjustment of the throttle element (4). Hollow screw according to claim 2 or 9, characterized in that the throttle element (4) is arranged linearly adjustable on or in the shaft (2) such that the throttle element (4) is arranged in the first throttle position (DSI) in the cavity (7) or directly at the axial opening (15), while in the second throttle position (DSII) the throttle element (4) is arranged outside the cavity (7) and axially spaced from the axial opening (15). Hollow screw according to one of claims 1, 9 or 10, characterized in that the linear guide (18) has a guide rod (19) firmly connected to the shaft (2) and a guide opening (20) formed on the throttle element (4) through which the guide rod (19) passes. Hollow screw according to claim 3, characterized in that the throttle element (4) is designed in two parts and has a rotatably adjustable mobile throttle part (23) and a stationary throttle part (24) which is statically arranged on or in the shaft (2). Hollow screw according to claim 12, characterized in that the mobile throttle part (23) and the stationary throttle part (24) each have at least one eccentric axial through-opening (25), that the through-openings (25) of the two throttle parts (23, 24) are aligned in axial overlap with each other in the first throttle position (DSI), while this axial overlap is reduced or not present in the second throttle position (DSII). Hollow screw according to one of claims 3, 12 or 13, characterized in that the throttle element (4) or the mobile throttle part (23) is rotatably guided on a spindle (27) arranged in the cavity (7) or on an internal thread formed on the inside of the shaft (2). Hollow screw according to claim 14, characterized in that the mobile throttle part (23) is axially spaced from the stationary throttle part (24) in the first throttle position (DSI), while the mobile throttle part (23) is axially in contact with the stationary throttle part (24) in the second throttle position (DSII).

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