Composite damping device for oil pressure lead screw

Abstract

The invention discloses an oil pressure lead screw composite damping device, which relates to the technical field of vibration reduction and shock resistance equipment, and comprises an oil cylinder, a piston rod and a ball lead screw, the oil cylinder is hollow to form a containing cavity; the piston rod penetrates through the oil cylinder, a piston sleeves the outer wall of the piston rod, a left lug plate is fixed to one end of the piston rod, a bearing seat is connected to the outer wall of the other end of the piston rod, and a guide channel is formed in the inner wall of the other end of the piston rod; a ball nut is rotationally connected to the outer wall of the ball screw, a right lug plate is fixed to one end of the ball screw and fixedly connected with the oil cylinder, the ball screw is coaxial with the guide channel, and one end of the ball nut is fixedly connected with the bearing seat. The piston rod does linear motion relative to the oil cylinder under the action of external power load, and meanwhile the ball nut and the piston rod are driven to rotate around the axis direction of the piston rod. Viscous damping force and inertia force can be provided at the same time on the basis that the size and the appearance of a traditional damper are almost not changed, and therefore the vibration reduction effect is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration reduction and anti-vibration equipment, and in particular to a hydraulic screw composite damping device. Background Art

[0002] As a common energy-dissipating vibration reduction device, dampers are widely used in various engineering fields. Compared to traditional viscous dampers, inertial capacitance dampers incorporate an inertial capacitance element. Under dynamic action, they can generate a large inertial force with low mass, thus achieving excellent vibration reduction.

[0003] Existing ball screw-based mechanical inertial damping devices rely solely on inertial force to achieve vibration reduction, lacking the synergistic effect of viscous damping force. Therefore, their vibration reduction capabilities are limited when faced with complex and changing vibration conditions, and they are unable to fully utilize the vibration reduction potential of the inertial damper, making it difficult to meet the requirements of some engineering scenarios with high vibration reduction requirements. Furthermore, hydraulic inertial dampers require external spiral pipes to connect the two ends of the cylinder filled with viscous fluid, making the entire device bulky and irregular in shape. This not only takes up a large space during transportation, increasing transportation costs and difficulty, but also makes installation more inconvenient and places high demands on installation space and conditions. This limits its applicability in engineering fields with limited space or special requirements for equipment appearance, affecting its widespread use in engineering projects. Summary of the Invention

[0004] The present application provides a hydraulic screw composite damping device, which can solve the technical problems of poor shock absorption effect and large space occupation in the prior art.

[0005] and a gear engaged with the drive means and the gear train connected Thereby, the gear train is connected along the axis of the oil cylinder to the axis of rotation of the oil pump, and the gear train is connected along the axis of the oil cylinder to the axis of rotation of the oil pump.

[0006] In combination with the above embodiments, in one embodiment, the bearing seat includes: a bearing seat baffle and a bearing seat cover plate, the bearing seat cover plate is located at the top of the bearing seat baffle, and the bearing seat baffle is fixedly connected to one end of the ball nut so that the rotational movement of the ball nut drives the rotation of the bearing seat.

[0007] In combination with the above embodiments, in one implementation, the hydraulic screw composite damping device further includes: a tapered roller bearing, which is arranged between the bearing seat and the piston rod so that the rotation of the bearing seat drives the rotation of the tapered roller bearing.

[0008] In combination with the above embodiment, in one implementation manner, the tapered roller bearings are arranged symmetrically in parallel around the axial direction of the piston rod.

[0009] In combination with the above embodiments, in one implementation, a left end cover and a right end cover are provided on the inner wall of the oil cylinder. The left end cover is detachably sealed and connected to the oil cylinder. The right end cover is detachably sealed and connected to the oil cylinder. The piston rod is sequentially passed through the left end cover, the piston and the right end cover. The left end cover, the right end cover and the oil cylinder are surrounded to form the cavity.

[0010] In combination with the above embodiments, in one embodiment, the left ear plate includes: a first fixed plate and two first side plates respectively arranged on both sides of the first fixed plate, the piston rod is fixedly connected to the first fixed plate, one end of the two first side plates are connected to the first fixed plate, and the other end of the two first side plates are slidably connected to the oil cylinder.

[0011] In combination with the above embodiments, in one embodiment, the right ear plate includes: a second fixed plate and two second side plates respectively arranged on both sides of the second fixed plate, the ball screw is fixedly connected to the second fixed plate, one end of the two second side plates is connected to the second fixed plate, and the other end of the two second side plates is fixedly connected to the oil cylinder.

[0012] In combination with the above embodiment, in one implementation manner, both the first fixing plate and the second fixing plate are provided with fixing holes.

[0013] In combination with the above embodiment, in one implementation manner, the cavity is filled with a viscous fluid.

[0014] In combination with the above embodiment, in one implementation manner, the viscous fluid is dimethyl silicone oil.

[0015] The beneficial effects of the technical solutions provided in the embodiments of the present application include: (1) The embodiment of the present application is provided with a piston rod and a ball screw, so that the piston rod moves linearly relative to the cylinder under the action of an external dynamic load and drives the ball nut and the piston rod to rotate around the axis of the piston rod. This motion conversion method enables the device to generate inertial force and viscous damping force simultaneously during the vibration reduction process. When the piston reciprocates in the cylinder filled with viscous fluid, it can not only generate viscous damping force like a traditional viscous damper, but also convert the reciprocating motion of the piston rod into the rotational motion of the ball nut and the bearing seat through the ball screw provided on the right side, thereby generating a significant inertial amplification effect, realizing the coordinated work of viscous damping and inertial capacity effect, effectively improving the vibration reduction effect, being able to better cope with various complex vibration conditions, providing more reliable vibration reduction guarantee for engineering structures, and broadening the application scope of inertial capacity dampers in different engineering fields, especially suitable for scenes with high requirements for vibration reduction effect, such as bridges and other fields.

[0016] (2) The embodiment of the present application adopts an axially compact layout design, with the various functional components arranged in sequence along the axis. At the same time, the oil cylinder, piston rod, ball screw and other components are integrated into one body, which greatly reduces the volume of the overall damping device and makes its appearance more regular and compact. This not only facilitates transportation and installation, reducing transportation costs and installation difficulties, but also improves the versatility and flexibility of the damping device, enabling it to better adapt to various complex engineering environments and different installation space requirements, enhances engineering applicability, and provides a more convenient and efficient vibration reduction solution for engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 A schematic cross-sectional view of a hydraulic screw composite damping device provided in an embodiment of the present application; Figure 2 A schematic diagram of an application of a hydraulic screw composite damping device in a stayed cable damper provided in an embodiment of the present application; Figure 3 A schematic diagram of an application of a hydraulic screw composite damping device in a cable-stayed lever mass damper provided in an embodiment of the present application; Figure 4 A schematic diagram of the application of a hydraulic screw composite damping device provided in an embodiment of the present application in a large-tonnage damper.

[0019] In the figure: 1. Left ear plate; 2. Left end cover; 3. Piston rod; 4. Cylinder; 5. Piston; 6. Right end cover; 7. Tapered roller bearing; 8. Bearing seat cover; 9. Ball screw; 10. Ball nut; 11. Right ear plate; 12. Guide channel; 13. Bearing seat baffle; 101. Hydraulic screw composite damping device. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] The present application provides a hydraulic screw composite damping device, which can solve the technical problems of poor vibration reduction effect and large space occupation in the prior art.

[0022] Figure 1 This is a schematic cross-sectional view of a hydraulic screw composite damping device provided in an embodiment of the present application. Figure 1 As shown, the embodiment of the present application includes: an oil cylinder 4, the interior of the oil cylinder 4 is hollow to form a cavity; a piston rod 3 running through the oil cylinder 4, a piston 5 is sleeved on the outer wall of the piston rod 3, the piston 5 slides in the cavity, a left ear plate 1 is fixed to one end of the piston rod 3, a bearing seat is connected to the outer wall of the other end of the piston rod 3, and a guide channel 12 is opened on the inner wall of the other end of the piston rod 3; a ball screw 9 and a ball nut 10 located on the outer wall of the ball screw 9 and rotatably connected to the ball screw 9, wherein a right ear plate 11 is fixed to one end of the ball screw 9, and the right ear plate 11 is fixedly connected to the oil cylinder 4, the other end of the ball screw 9 is coaxial with the guide channel 12, and one end of the ball nut 10 is fixedly connected to the bearing seat, so that the piston rod 3 makes a linear motion relative to the oil cylinder under the action of an external dynamic load while driving the ball nut 10 and the piston rod 3 to rotate around the axis of the piston rod 3.

[0023] Figure 2 Schematic diagram of the application of a hydraulic screw composite damping device in a cable-stayed damper provided in an embodiment of the present application. Figure 3 Schematic diagram of the application of a hydraulic screw composite damping device in a cable-stayed lever mass damper provided in an embodiment of the present application. Figure 4 This is a schematic diagram of the application of a hydraulic screw composite damping device in a large-tonnage damper provided by an embodiment of the present application. Figure 2 、 Figure 3 as well as Figure 4The hydraulic screw composite damping device 101 provided in the embodiment of the present application can be applied to a cable-stayed cable damper, a cable-stayed cable lever mass damper or a large-tonnage damper. Specifically, the cable-stayed cable is prone to vibration under the action of dynamic forces such as wind loads and vehicle loads. The piston 5 in the hydraulic screw composite damping device 101 provided in the embodiment of the present application moves in the oil cylinder 4 to generate a viscous damping force, while the ball screw converts the linear motion of the piston rod 3 into the rotational motion of the ball nut 10 and the bearing seat to generate an inertial force. The synergistic effect of the two can effectively dissipate the vibration energy of the cable-stayed cable, reduce the amplitude of the cable-stayed cable, and thus improve the stability and durability of the bridge structure. At the same time, the overall structure of the damping device is compact and can be conveniently installed at different positions of the cable-stayed cable. Furthermore, for large-tonnage engineering objects such as large building structures and industrial equipment foundations, the vibration hazards that are easily generated under the influence of dynamic forces such as strong winds and earthquakes are extremely great. The piston 5 and viscous fluid in the cylinder 4 provided by the hydraulic screw composite damping device 101 provided in the embodiment of the present application can generate a large viscous damping force. At the same time, the setting of the ball screw can produce a significant inertia amplification effect, realizing the coordinated work of viscous damping and inertial volume effect, effectively improving the vibration reduction effect, and thus meeting the huge energy consumption demand of large-tonnage engineering objects for vibration reduction devices.

[0024] In some other embodiments of the present application, the ball screw and ball nut can be replaced by other inertial devices such as hydraulic motors and gear racks, as long as the piston rod can make linear motion relative to the cylinder under the action of external dynamic load while driving the inertial device to rotate around the axis of the piston rod. No limitation is made here. The left ear plate 1 and the right ear plate 11 in the embodiment of the present application are arranged at opposite ends of the oil cylinder 4. At the same time, one end of the piston rod 3 is fixedly connected to the left ear plate 1, and one end of the ball screw 9 is fixedly connected to the right ear plate 11. Therefore, the oil cylinder 4, the piston rod 3, and the ball screw 9 can be arranged in sequence along the axis, which greatly reduces the volume of the overall damping device and makes its appearance more regular and compact.

[0025] In the embodiment of the present application, the specific calculation formula for the total output of the hydraulic screw composite damping device is:

[0026] in, It indicates the total output of the hydraulic screw composite damping device, that is, the force generated by the damping device when it is subjected to external dynamic load, which is used to resist or slow down the relative movement caused by external vibration. represents the coefficient of inertia, represents the relative displacement between the left ear plate 1 and the right ear plate 11 in the damping device, Indicates time, Represents the damping coefficient.

[0027] The specific calculation formula of the inertia coefficient is:

[0028] in, represents the lead of the ball screw 9, It represents the moment of inertia of the rotating body composed of the ball nut 10 and the bearing seat.

[0029] Specifically, the damper's volume inertia and viscous damping coefficients vary across different projects. By adjusting the lead of the ball screw 9, the moment of inertia of the combined rotating assembly of the bearing seat and ball nut 10, the volume inertia coefficient can be quantitatively designed. By adjusting the cross-sectional area of the flow orifice of the piston 5 and the viscosity of the viscous fluid, the damping coefficient can be quantitatively designed. This allows for precise and quantitative parameter design to meet various vibration reduction requirements.

[0030] In an embodiment of the present application, the hydraulic screw composite damping device 101 also includes: a bearing seat, the bearing seat includes a bearing seat baffle 13 and a bearing seat cover 8, the bearing seat cover 8 is located at the top of the bearing seat baffle 13, and the bearing seat baffle 13 is fixedly connected to one end of the ball nut 10 so that the rotational movement of the ball nut 10 drives the rotation of the bearing seat.

[0031] Furthermore, the damping device also includes a tapered roller bearing 7, which is arranged between the bearing seat 8 and the piston rod 3, so that the rotation of the bearing seat drives the rotation of the tapered roller bearing 7.

[0032] Specifically, when the piston rod 3 is subjected to an external dynamic load and undergoes translation, the bearing seat baffle 13 and the tapered roller bearing 7 form a mechanical limit, forcing the bearing seat to undergo synchronous translation and rotation in the same direction as the piston rod 3, thereby achieving translational coordination between the piston rod 3 and the bearing seat. Furthermore, because the bearing seat baffle 13 is fixedly connected to one end of the ball nut 10, when the piston rod 3 is subjected to an external dynamic load and undergoes translation, the ball nut 10 is also driven to undergo synchronous translation in the same direction. The inner wall of the ball nut 10 is provided with threads that match the threads on the outer wall of the ball screw 9. The ball screw 9 and the ball nut 10 cooperate to enable the piston rod 3 to perform linear motion relative to the cylinder 4 under the action of the external dynamic load, while driving the ball nut 10 and the piston rod 3 to rotate about the axis of the piston rod 3.

[0033] In the embodiment of the present application, the tapered roller bearings 7 are arranged symmetrically in parallel around the axial direction of the piston rod 3. Therefore, when the damping device is subjected to tension or compression, mechanical limitation of the bearing seat baffle and the tapered roller bearings 7 can be achieved.

[0034] In an embodiment of the present application, a left end cover 2 and a right end cover 6 are provided on the inner wall of the oil cylinder 4. The left end cover 2 is detachably sealed and connected to the oil cylinder 4, and the right end cover 6 is detachably sealed and connected to the oil cylinder 4. The piston rod 3 is sequentially passed through the left end cover 2, the piston 5 and the right end cover 6. The left end cover 2, the right end cover 6 and the oil cylinder 4 are surrounded to form a cavity.

[0035] Specifically, the left end cover 2, the right end cover 6 and the oil cylinder 4 are jointly enclosed to form a sealed cavity to prevent leakage of the viscous fluid in the oil cylinder 4. The piston 5 is provided with a flow hole. The piston 5 moves back and forth, and the viscous fluid passes through the flow hole to ensure the stable generation of the viscous damping force.

[0036] In an embodiment of the present application, the left ear plate 1 includes: a first fixed plate and two first side plates respectively arranged on both sides of the first fixed plate, the piston rod 3 is fixedly connected to the first fixed plate, one end of the two first side plates are connected to the first fixed plate, and the other end of the two first side plates are slidably connected to the oil cylinder 4.

[0037] Specifically, a threaded hole is provided on the surface of the first fixing plate facing the piston rod 3, and the piston rod 3 is threadedly connected to the first fixing plate. The sliding connection between the two first side plates and the oil cylinder 4 provides a guide function for the left ear plate 1, ensuring that the left ear plate 1 moves axially on the oil cylinder 4 under the drive of the piston rod 3. In some other embodiments of the present application, other fixed connection methods can be used to fix the first fixing plate and the piston rod 3 together, which are not limited here. Among them, the vertical distance between the two first side plates is greater than the width of the oil cylinder 4, thereby providing sufficient installation and movement space for the oil cylinder 4, ensuring smooth relative movement between the two first side plates and the oil cylinder 4, and avoiding interference or wear due to insufficient space.

[0038] In an embodiment of the present application, the right ear plate 11 includes: a second fixed plate and two second side plates respectively arranged on both sides of the second fixed plate, the ball screw 9 is fixedly connected to the second fixed plate, one end of the two second side plates are connected to the second fixed plate, and the other end of the two second side plates are fixedly connected to the oil cylinder 4.

[0039] Specifically, one end of the ball screw 9 is fixed to the center of the second fixed plate, and the other end of the ball screw 9 extends into the guide channel 12. When the piston rod 3 slides under an external dynamic load, the ball screw 9 expands and contracts within the guide channel 12. One end of each of the two second side plates is connected to opposite ends of the second fixed plate, and the other ends of the two second side plates are fixedly connected to the outer wall of the oil cylinder 4. The fixed connection can be achieved by welding, clamping, or other fixed connection methods, which are not limited here.

[0040] In the embodiment of the present application, fixing holes are provided on both the first fixing plate and the second fixing plate.

[0041] Specifically, the fixing hole is used to mechanically connect the damping device to the equipment that requires vibration reduction. The damping device provided in the embodiment of the present application can be firmly installed on the equipment by passing bolts, screws or other fasteners through the fixing hole.

[0042] In the embodiment of the present application, the cavity is filled with viscous fluid.

[0043] Specifically, the viscous fluid is dimethyl silicone oil. Specifically, the viscous fluid should have good viscosity-temperature characteristics, chemical stability, and a low freezing point, and be suitable for various temperature environments. In some other embodiments of the present application, other materials can also be used as the viscous fluid as long as they meet the performance and reliability requirements of the damping device. The material of the viscous fluid is not limited here.

[0044] In summary, the embodiments of the present application employ a piston rod and a ball screw, so that the piston rod, under the action of an external dynamic load, simultaneously moves linearly relative to the cylinder and simultaneously drives the ball nut and piston rod to rotate about the piston rod axis. This motion conversion method enables the device to simultaneously generate inertial force and viscous damping force during vibration reduction. When the piston 5 reciprocates within the cylinder 4 filled with viscous fluid, not only does it generate viscous damping force like a traditional viscous damper, but the ball screw 9 disposed on the right side also converts the reciprocating motion of the piston rod 3 into rotational motion of the ball nut 10 and the bearing seat, thereby generating a significant inertial amplification effect. This achieves the synergistic effect of viscous damping and inertial capacitance, effectively improving the vibration reduction effect, better coping with various complex vibration conditions, providing more reliable vibration reduction for engineering structures, and broadening the application range of inertial capacitance dampers in various engineering fields, making them particularly suitable for applications requiring high vibration reduction, such as bridges. The embodiment of the present application adopts an axially compact layout design, with the various functional components arranged sequentially along the axis. The cylinder 4, piston rod 3, ball screw 9, and other components are integrated into one unit, significantly reducing the overall volume of the damping device and making its appearance more regular and compact. This not only facilitates transportation and installation, reducing transportation costs and installation difficulty, but also improves the versatility and flexibility of the damping device, enabling it to better adapt to various complex engineering environments and different installation space requirements, enhancing its applicability in engineering projects and providing a more convenient and efficient vibration reduction solution for engineering design.

[0045] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0046] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0047] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A hydraulic screw composite damping device, characterized in that: include: An oil cylinder (4), wherein the interior of the oil cylinder (4) is hollow to form a cavity; A piston rod (3) passes through the oil cylinder (4), a piston (5) is sleeved on the outer wall of the piston rod (3), the piston (5) slides in the cavity, a left ear plate (1) is fixed to one end of the piston rod (3), a bearing seat is connected to the outer wall of the other end of the piston rod (3), and a guide channel (12) is opened on the inner wall of the other end of the piston rod (3); A ball screw (9) and a ball nut (10) located at the outer wall of the ball screw (9) and rotatably connected to the ball screw (9), wherein a right ear plate (11) is fixed to one end of the ball screw (9), and the right ear plate (11) is fixedly connected to the oil cylinder (4), the other end of the ball screw (9) is coaxial with the guide channel (12), and one end of the ball nut (10) is fixedly connected to the bearing seat, so that the piston rod (3) performs linear motion relative to the oil cylinder (4) under the action of an external dynamic load, while driving the ball nut (10) and the piston rod (3) to rotate around the axis of the piston rod (3).

2. The hydraulic screw composite damping device according to claim 1, characterized in that: The bearing seat comprises: A bearing seat baffle (13) and a bearing seat cover (8), wherein the bearing seat cover (8) is located at the top end of the bearing seat baffle (13), and the bearing seat baffle (13) is fixedly connected to one end of the ball nut (10) so that the rotation of the ball nut (10) drives the rotation of the bearing seat.

3. The hydraulic screw composite damping device according to claim 2, characterized in that: The hydraulic screw composite damping device also includes: A tapered roller bearing (7) is provided between the bearing seat (8) and the piston rod (3), so that the rotation of the bearing seat drives the rotation of the tapered roller bearing (7).

4. The hydraulic screw composite damping device according to claim 3, characterized in that: The tapered roller bearings (7) are arranged symmetrically in parallel around the axial direction of the piston rod (3).

5. The hydraulic screw composite damping device according to claim 1, characterized in that: The inner wall of the oil cylinder (4) is provided with a left end cover (2) and a right end cover (6) opposite to each other. The left end cover (2) is detachably sealed and connected to the oil cylinder (4). The right end cover (6) is detachably sealed and connected to the oil cylinder (4). The piston rod (3) is sequentially passed through the left end cover (2), the piston (5) and the right end cover (6). The left end cover (2), the right end cover (6) and the oil cylinder (4) are surrounded to form the cavity.

6. The hydraulic screw composite damping device according to claim 1, characterized in that: The left ear plate (1) comprises: A first fixed plate and two first side plates respectively arranged on both sides of the first fixed plate, the piston rod (3) is fixedly connected to the first fixed plate, one end of the two first side plates are connected to the first fixed plate, and the other ends of the two first side plates are slidably connected to the oil cylinder (4).

7. The hydraulic screw composite damping device according to claim 6, characterized in that: The right ear plate (11) comprises: A second fixed plate and two second side plates respectively arranged on both sides of the second fixed plate, the ball screw (9) is fixedly connected to the second fixed plate, one end of each of the two second side plates is connected to the second fixed plate, and the other end of each of the two second side plates is fixedly connected to the oil cylinder (4).

8. The hydraulic screw composite damping device according to claim 7, characterized in that: The first fixing plate and the second fixing plate are both provided with fixing holes.

9. The hydraulic screw composite damping device according to claim 1, characterized in that: The cavity is filled with viscous fluid.

Images