Multi-station vertical and horizontal bearing sealing durability test bench

Abstract

The invention discloses a multi-station vertical and horizontal bearing sealing durability test bench, which comprises a servo motor, a plurality of test bottom plates, a test rod and a test box, the test box is provided with a gas pressure interface, a liquid medium interface and a rotatable test shaft, a to-be-tested bearing is arranged in the test box, the test bottom plates are connected through the test rod, the test box is fixed on the test bottom plates, and the servo motor is connected with the test rod. The body of the servo motor is fixed on the test bottom plate, the rotating shaft is in transmission with the test shaft through a belt, the liquid medium interface is connected with the liquid control cylinder through a pipeline, the lower end of the test rod is provided with a vertical adjusting support leg, the side edge of the test bottom plate is provided with a horizontal adjusting support leg, and vertical-horizontal conversion of the rack is realized through contact between different adjusting support legs and the ground. According to the multi-station vertical and horizontal two-type bearing sealing durability test bench, vertical and horizontal test modes can be realized, different test requirements are met, the arrangement of the liquid control cylinder facilitates the control of a liquid medium, and the test accuracy and diversity are improved.

Description

Technical Field

[0001] The present invention relates to a bearing testing device, and more specifically to a multi-station vertical and horizontal two-mode bearing seal durability test bench. Background Art

[0002] With the continuous development of the domestic manufacturing level and the continuous improvement of the automation level in various industries, bearings have always played an important role as the joints of equipment. As a key direction for China's vigorous development, the manufacturing of high-end bearings, and as a key component, the upstream and downstream technology development of seals is the inevitable path for the development of high-end bearings. Its presence can be seen everywhere in moving parts from the deep sea to space. New demands drive new technologies, and also make its detection technology become increasingly important in the bearing field.

[0003] For bearings to be used for a long time, it is necessary to ensure their good lubrication and a strictly clean environment. Therefore, seals play a crucial role in isolating the harsh external atmosphere for bearings. A large number of application failures reveal that the failure of bearing seals will seriously affect the lubrication environment, and then greatly accelerate the failure of bearings, causing unexpected and serious economic losses and even safety problems. The durability performance of seals under harsh atmospheres for actual use conditions is increasingly becoming a necessary indicator for evaluating bearing performance.

[0004] Currently, in the existing technologies, testing devices are mostly used to achieve the sealing test of bearings. For example, the invention patent with the publication number CN118882934A and the name of a testing device for semi-immersion seal test of hub bearings discloses that the immersion seal test of bearings is achieved by setting a driving frame and a test frame. However, in the test process of the above-mentioned testing device, the use state of the bearing is fixed as vertical or horizontal. Therefore, it can only achieve the sealing test of bearings in a certain use state. Thus, the existing testing device has the problem of insufficiently wide application scope. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technologies, the purpose of the present invention is to provide a multi-station vertical and horizontal two-mode bearing seal durability test bench with a wider application scope.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a multi-station vertical and horizontal bearing seal durability test bench, including a servo motor, a plurality of test base plates, a plurality of test rods and a plurality of test boxes, the test box is provided with a gas pressure interface and a liquid medium interface and a rotatable test shaft, the bearing to be tested is installed on the test box, a plurality of test base plates are interconnected by a plurality of test rods, a plurality of the test boxes are fixedly installed on the test base plate, the body of the servo motor is fixedly installed on the test base plate, and the rotating shaft is driven by the test shaft through a belt. It also includes a control liquid cylinder, the liquid medium interface is connected to the control liquid cylinder through a pipeline, the lower end of the test rod is provided with a vertical adjustment foot, and the side of the test base plate is provided with a horizontal adjustment foot. When the vertical adjustment foot contacts the external ground, the test bench is vertical, and when the horizontal adjustment foot contacts the external ground, the test bench is horizontal.

[0007] As a further improvement of the present invention, there are two test base plates, both of which are square in shape and distributed up and down, and there are four test rods, which are fixedly mounted on the four corners of the test base plates respectively. The body of the servo motor is fixedly mounted on the test base plate at the top, and the rotating shaft of the servo motor passes downward through the test base plate and a driving wheel is coaxially sleeved thereon. Several test boxes are fixed on the upper side surface of the test base plate at the bottom, and the test shaft is arranged vertically upward, and the rotating shaft passes downward through the test base plate. A number of driven wheels corresponding to the positions of the test boxes are rotatably provided on the lower side surface of the test base plate at the top. The test shaft is connected to the driven wheel through a coupling, and the driving wheel is connected to the driven wheel through a belt. A waist-shaped hole is opened on the test base plate, and a tensioning bolt is installed in the waist-shaped hole. The lower end of the tensioning bolt is coaxially and rotatably sleeved with a tensioning wheel, and the tensioning wheel is located between the two driven wheels and in contact with the belt.

[0008] As a further improvement of the present invention, the test box includes a box cover and a box body, the box cover is fixedly mounted on the upper side of the box body by bolts, the gas pressure interface and the liquid medium interface are respectively mounted on two adjacent sides of the box body, the test shaft penetrates the box cover and the box body from top to bottom, and the bearing to be tested is mounted on the bottom of the box body and sleeved on the test shaft.

[0009] As a further improvement of the present invention, a viewing window is provided on the side of the box.

[0010] As a further improvement of the present invention, an L-shaped spoiler baffle is provided on the inner wall of the box body at a position relative to the gas pressure interface, and one end of the spoiler baffle is fixed on the inner wall of the box body so that the vertical plate surface of the spoiler baffle is arranged opposite to the gas pressure interface.

[0011] As a further improvement of the present invention, a test tooling is detachably connected to the lower end of the bearing to be tested, and a transparent measuring tube is provided at the lower end of the test tooling. The transparent measuring tube is of an L-shaped tube structure, and measuring tube scales are provided on the outer side wall of the horizontal section at the lower part.

[0012] As a further improvement of the present invention, the test tooling includes a mating flange, an adapter adjustment stud, and a quick-connect plug. The quick-connect plug is fixed to the upper end of the transparent measuring tube and is threadedly connected to the lower end of the adapter adjustment stud. The mating flange is sleeved on the adapter adjustment stud and is fixed by screwing in a set screw from the side. A sealing ring and a connecting component are provided on the adapter adjustment stud, and the upper end of the adapter adjustment stud is connected to the bottom of the box body through the connecting component.

[0013] As a further improvement of the present invention, the connecting component is a plurality of magnets, and the plurality of magnets are threadedly connected to the upper end face of the adapter adjustment stud.

[0014] Advantages of the present invention: In traditional bearing seal durability test benches, most of them have relatively single functions and fixed test methods, making it difficult to meet different test scenarios and diverse test requirements. However, in the multi-station vertical and horizontal two-mode bearing seal durability test bench of the present invention, by setting the liquid control cylinder to be connected to the liquid medium interface, the input of the liquid medium can be accurately controlled. And with the unique design of the vertical adjustment feet and horizontal adjustment feet, the test bench can flexibly switch between the vertical and horizontal working modes according to actual needs, greatly improving the flexibility and adaptability of the test. At the same time, the design of the double test bottom plates, four test rods, and related transmission components optimizes the power transmission structure, ensuring the stability and reliability of the test process. The design of the viewing window, flow disturbance resistance plate, etc. in the test chamber facilitates observing the test situation and optimizing the fluid environment in the chamber. The cooperation between the test tooling and the transparent measuring tube facilitates quantitative observation of the test results. Overall, compared with traditional test benches, it has more comprehensive functions, more scientific testing, and more convenient observation, greatly improving the efficiency and accuracy of bearing seal durability testing. Description of the Drawings

[0015] Figure 1 is the overall structure diagram of the multi-station vertical and horizontal two-mode bearing seal durability test bench of the present invention; Figure 2 is the schematic diagram in the horizontal state; Figure 3 is the cross-sectional schematic diagram of the test step; Figure 4 is the internal structure schematic diagram of the test chamber; Figure 5 is the structure schematic diagram of the test tooling; Figure 6 is the internal structure schematic diagram of the test tooling. DETAILED DESCRIPTION

[0016] The present invention will be further described below in detail with reference to the embodiments shown in the accompanying drawings.

[0017] Reference Figure 1 As shown, the multi-station vertical and horizontal bearing seal durability test bench of this embodiment includes a servo motor 1, a plurality of test base plates 2, a plurality of test rods 3 and a plurality of test boxes 4. The test box 4 is provided with a gas pressure interface 41, a liquid medium interface 42 and a rotatable test shaft 43, and the bearing to be tested is installed on the test box 4. The plurality of test base plates 2 are interconnected through a plurality of test rods 3, and the plurality of test boxes 4 are fixedly installed on the test base plate 2. The body of the servo motor 1 is fixedly installed on the test base plate 2, and the rotating shaft is driven by the test shaft 43 through a belt. It also includes a control liquid cylinder 5, and the liquid medium interface 42 is connected to the control liquid cylinder 5 through a pipeline. The lower end of the test rod 3 is provided with a vertical adjustment foot 31, and the side of the test base plate 2 is provided with a horizontal adjustment foot 21. When the vertical adjustment foot 31 contacts the external ground, the test bench is vertical, and when the horizontal adjustment foot 21 contacts the external ground, the test bench is horizontal. In this way, vertical and horizontal conversion can be achieved through the setting of vertical adjustment legs 31 and horizontal adjustment legs 21. At the same time, the liquid control cylinder 5 is used to control the liquid pressure, which is not limited to the placement posture of the liquid control cylinder 5. Therefore, the test bench of this embodiment has the following test process: first, the required working state of the bearing to be tested is determined to choose whether to place the bench vertically or horizontally. After the selection is completed, it is placed on the water receiving tray, and then the bearing to be tested is installed in the test box 4. After that, the servo motor 1 is started to drive the test shaft 43 to rotate, so that the test can be effectively realized. During the test, the gas pressure interface 41, the liquid medium interface 42 and the liquid control cylinder 5 are used to cooperate to realize the gas pressure regulation and liquid pressure regulation in the test box 4. The liquid control cylinder 5 is embedded in the test base plate 2 slightly higher than the water receiving tray, which can greatly reduce the space and pipeline length required for installation, and can also reduce leakage pollution.

[0018] Further, see Figure 1As shown in the figure, there are two test bottom plates 2, both of which are square and distributed vertically. There are four test rods 3, which are respectively fixedly installed at the four corners of the test bottom plate 2. The body of the servo motor 1 is fixedly installed on the test bottom plate 2 at the upper part. The rotating shaft of the servo motor 1 passes downward through the test bottom plate 2 and is coaxially sleeved with a driving wheel on it. A number of test boxes 4 are fixed on the upper side of the test bottom plate 2 at the lower part, and the test shaft 43 is arranged vertically upward. The rotating shaft passes downward through the test bottom plate 2. A driven wheel corresponding to the test box 4 in terms of quantity and position is rotatably arranged on the lower side of the test bottom plate 2 at the upper part. The test shaft 43 is connected to the driven wheel through a coupling. The driving wheel is connected to the driven wheel through a belt. A waist-shaped hole 22 is opened on the test bottom plate 2, and a tensioning bolt 23 is installed in the waist-shaped hole 22. The lower end of the tensioning bolt 23 is coaxially and rotatably sleeved with a tensioning wheel. The tensioning wheel is located between the two driven wheels and contacts the belt. Through the above structure, a driving wheel system, a driven wheel system and a tensioning wheel system for transmission can be formed. During the working process, the driving wheel system is directly driven by the servo motor 1, and feedback control is carried out in cooperation with an absolute encoder. The driving wheel system is composed of a synchronous pulley with a rib and the driven wheel systems at the other three corners and a tensioning wheel system to form a four-axis parallel and tensioning-stabilized square wheel system array to realize multi-station parallel operation; among them, the driven wheel system controls the tensioning displacement amount by adjusting the belt pulley tensioning nut, so that the synchronous belts connected by the four peripheral wheel systems (one driving wheel system and three driven wheel systems) can operate for a long time without loosening; the test bottom plate 2 and the shafts of each wheel system are fixedly matched and locked with flange nuts. The shafts rotate relative to the belt pulleys through bearings, and the outer belt pulleys of each shaft system can rotate freely after the shafts are fixed on the test bottom plate 2; a one-way universal coupling is used at the end of each shaft system to be connected with the corresponding test box 4 with a set screw to offset the lateral force that may be caused by misalignment. At the same time, when each test box 4 on the test bottom plate 2 is disassembled from the coupling, it does not affect the other workstations, and tests with different numbers of workstations can be flexibly carried out simultaneously.

[0019] Further, referring to Figure 3As shown in the figure, the test chamber 4 includes a chamber lid 44 and a chamber body 45. A companion bearing is installed at the center of the chamber lid 44 to maintain the axial stability of the test shaft 43 and improve the rotation accuracy. The chamber lid 44 is fixedly installed on the upper side of the chamber body 45 by bolts. The gas pressure interface 41 and the liquid medium interface 42 are respectively installed on two adjacent sides of the chamber body 45. The test shaft 43 passes through the chamber lid 44 and the chamber body 45 from top to bottom. The bearing to be tested is installed at the bottom of the chamber body 45 and sleeved on the test shaft 43. Such a structure of the test chamber 4 is convenient for installation and disassembly, and at the same time is convenient for accessing gas pressure and liquid medium, meeting the condition requirements for testing the sealing performance of the bearing. In this embodiment, the liquid control cylinder 5 has two upper and lower chambers corresponding to two upper and lower interfaces (high-pressure air inlet and liquid medium outlet). The test chamber unit has three interfaces (gas pressure interface 41, liquid medium interface 42, chamber body gas pressure test port). A switch control valve and a throttle valve are added between each interface to control the fluid switch and speed. Among them, the high-pressure air inlet is connected to the external air compressor air source; the liquid medium outlet is connected to the liquid medium interface 42; the gas pressure interface 41 is independently connected to the air source valve with controllable pressure outside; the chamber body gas pressure test port is connected to the pressure transmitter. The liquid application process is as follows: Open the switch of the high-pressure air inlet and the switch between the liquid medium outlet and the liquid medium interface 42. The pressure in the air chamber of the liquid control cylinder 5 rises, thereby compressing the space of the liquid chamber, so that the liquid is pressed into the test chamber unit at a throttling speed. Observe the liquid level height through the organic glass window of the test chamber 4, and then close the above two switches to complete the filling of the liquid medium. To drain the liquid in the chamber, the following steps are taken: Open the switch between the liquid medium outlet and the liquid medium interface 42. By adjusting the pressure of the gas pressure interface 41, a pressure difference is formed between it and the air chamber of the liquid control cylinder 5, and the liquid in the chamber is pushed back into the liquid chamber of the liquid control cylinder 5, and then close the switch between the liquid medium outlet and the liquid medium interface 42. According to the actual working conditions of the seal to be tested, the various inlets of the chamber body should be flexibly controlled to form a test atmosphere with a gas pressure environment, a liquid environment, or a gas pressure and liquid environment at the same time.

[0020] Further, referring to Figure 4 As shown in the figure, a viewing window 421 is provided on the side of the chamber body 45. A groove is opened on the side of the chamber body and filled with a transparent medium to form the viewing window 421 for observing the liquid height and the environment.

[0021] Further, referring to Figure 4As shown in the figure, an L-shaped flow disturbance and resistance plate 422 is provided on the inner side wall of the box body 45 at a position relative to the gas pressure interface 41. One end of the flow disturbance and resistance plate 422 is fixed on the inner side wall of the box body 45, so that the vertical plate surface of the flow disturbance and resistance plate 422 is arranged directly opposite to the gas pressure interface 41. The gas pressure interface 41 is provided with the flow disturbance and resistance plate 422, so that the gas diffuses evenly in the box during rapid inflation, avoiding phenomena such as liquid medium being splashed by the blowing air, and also hindering a large amount of liquid from being inhaled into the gas channel during rapid decompression; in this embodiment, an inverted V-shaped opening is provided at the closing position of the box cover 44 and the box body 45, which is convenient for applying sealant and is also easy to tear off in a whole circle after the test; the liquid medium interface (42) is placed at the lowest position in the internal space of the box body to ensure that the liquid is drained cleanly.

[0022] Further, a test tooling is detachably connected to the lower end of the bearing to be tested. A transparent measuring tube 10 is provided at the lower end of the test tooling. The transparent measuring tube 10 is of an L-shaped tube structure, and measuring tube scales are provided on the outer side wall of the horizontal section at the lower part. The transparent measuring tube 10 and the measuring tube scales can directly measure the liquid leakage amount, so as to accurately evaluate the sealing performance of the bearing. The outer shell of the test piece tooling is detachable from the box body, and a sealing ring is added and locked with screws for sealing, which is convenient for quickly and efficiently replacing the test sample.

[0023] Further, referring to Figure 5 and Figure 6 As shown in the figure, the test tooling includes a mating flange 6, an adapter adjustment stud 7 and a quick-connect plug 8. The quick-connect plug 8 is fixed to the upper end of the transparent measuring tube 10 and is threadedly connected to the lower end of the adapter adjustment stud 7. The mating flange 6 is sleeved on the adapter adjustment stud 7 and is fixed by screwing in a set screw from the side. A sealing ring and a connecting component are provided on the adapter adjustment stud 7, and the upper end of the adapter adjustment stud 7 is connected to the bottom of the box body 45 through the connecting component. This structure design of the test tooling is reasonable, which is convenient for connecting and disassembling with the bearing to be tested, and at the same time ensures the sealing performance of the connection.

[0024] Further, the connecting components are a plurality of magnets 9, and the plurality of magnets 9 are threadedly connected to the upper end surface of the adapter adjustment stud 7. A magnetic adsorption type leakage measurement device is installed at the bottom of the test chamber 4 for different forms of seal failure states during the whole test process, facilitating obtaining real-time data during the R & D test. Four threaded strong magnets 9 are directly threadedly connected to the adapter adjustment stud; between the center hole of the mating flange and the outside of the adapter adjustment stud 7 is a threaded connection, and the thread is used to adjust the distance between the magnet 9 and the target plane (such as the bottom of the box body 45) with possible leakage holes, thereby adjusting the magnetic attraction force; three set screws are evenly distributed on the circumferential surface of the boss cylinder of the mating flange 6 for anti-loosening and stabilizing the magnetic attraction force. The large end face of the mating flange 6 is fitted with a sealing ring for quick disassembly and assembly, eliminating the operation of repeated sealing; the mating flange 6 is designed with auxiliary screw clearance holes for the case where strong locking with the target plane is required, and can also be used in the case where it is not allowed to remove the device from the fitting plane and disassemble the outer shell of the test sample; there is a sealed pipe threaded connection between the adapter adjustment stud 7 and the quick-connect plug 8; the quick-connect plug 8 can be directly inserted into the graduated measuring tube 10. When measuring liquid leakage, the end of the measuring tube 10 is connected to a measuring tool or closed, and the leaked liquid is directly guided by the taper angle at the end of the test shaft 43 and dripped into the collection tube; when measuring gas leakage, a drop of colored liquid that is immiscible with the gas is injected into the measuring tube 10 with a small inner diameter to the scale starting point, and the distance that the colored liquid moves outward in the tube within a certain time is observed, and the gas leakage volume (volume under the current atmospheric pressure environment) is directly read. This method is more accurate than the traditional method of indirectly calculating minute leakage by measuring gas pressure changes: not affected by external nodes of the seal, less affected by temperature, the pressure in the box can be controlled to a constant value, high-precision sensors are not required for minute pressure difference changes, and the leaked material can be collected for analysis.

[0025] In summary, the multi-station vertical and horizontal two-style bearing seal durability test bench can be flexibly adjusted to be vertical or horizontal, with stable power transmission, the test chamber is easy to install and disassemble and can meet the test conditions, the viewing window is convenient for observation, the flow disturbance resistance plate improves the test accuracy, the test fixture is easy to connect and can accurately measure the leakage amount. Compared with the background technology, the overall solution has significant advantages in terms of test flexibility, accuracy, and operation convenience.

[0026] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A multi-station vertical and horizontal bearing seal durability test bench, comprising a servo motor (1), a plurality of test base plates (2), a plurality of test rods (3) and a plurality of test boxes (4), the test box (4) being provided with a gas pressure interface (41) and a liquid medium interface (42) and a rotatable test shaft (43), the bearing to be tested being mounted on the test box (4), the plurality of test base plates (2) being connected to each other via a plurality of test rods (3), a plurality of the test boxes (4) being fixedly mounted on the test base plate (2), the body of the servo motor (1) being fixedly mounted on the test base plate (2), the rotating shaft being driven by the test shaft (43) via a belt, and characterized in that: The test bench also includes a control liquid cylinder (5), the liquid medium interface (42) is connected to the control liquid cylinder (5) through a pipeline, the lower end of the test rod (3) is provided with a vertical adjustment foot (31), and the side of the test base plate (2) is provided with a horizontal adjustment foot (21), when the vertical adjustment foot (31) is in contact with the external ground, the test bench is in a vertical position, and when the horizontal adjustment foot (21) is in contact with the external ground, the test bench is in a horizontal position.

2. The multi-station vertical and horizontal bearing seal durability test bench according to claim 1 is characterized in that: The test base plates (2) are provided with two, both of which are in a square shape and are distributed up and down. The test rods (3) are provided with four, which are respectively fixedly mounted on the four corners of the test base plates (2). The body of the servo motor (1) is fixedly mounted on the test base plate (2) located above. The rotating shaft of the servo motor (1) passes downward through the test base plate (2) and a driving wheel is coaxially sleeved thereon. A plurality of test boxes (4) are fixed on the upper side surface of the test base plate (2) located below. The test shaft (43) is arranged vertically upward, and the rotating shaft is The lower side of the test base plate (2) passes through the test base plate (2), and a number of driven wheels corresponding to the test box (4) are rotatably provided on the lower side of the test base plate (2) located above. The test shaft (43) is connected to the driven wheel through a coupling, and the driving wheel is connected to the driven wheel through a belt. The test base plate (2) is provided with a waist-shaped hole (22), and a tensioning bolt (23) is installed in the waist-shaped hole (22). The lower end of the tensioning bolt (23) is coaxially rotatably sleeved with a tensioning wheel. The tensioning wheel is located between the two driven wheels and is in contact with the belt.

3. The multi-station vertical and horizontal bearing seal durability test bench according to claim 1 or 2, characterized in that: The test box (4) comprises a box cover (44) and a box body (45); the box cover (44) is fixedly mounted on the upper side of the box body (45) by means of bolts; the gas pressure interface (41) and the liquid medium interface (42) are respectively mounted on two adjacent side surfaces of the box body (45); the test shaft (43) penetrates the box cover (44) and the box body (45) from top to bottom; and the bearing to be tested is mounted on the bottom of the box body (45) and sleeved on the test shaft (43).

4. The multi-station vertical and horizontal bearing seal durability test bench according to claim 3 is characterized in that: A visual window (421) is provided on the side of the box body (45).

5. The multi-station vertical and horizontal bearing seal durability test bench according to claim 4 is characterized in that: An L-shaped spoiler baffle (422) is provided on the inner side wall of the box body (45) at a position relative to the gas pressure interface (41), and one end of the spoiler baffle (422) is fixed to the inner side wall of the box body (45) so that the vertical plate surface of the spoiler baffle (422) is arranged opposite to the gas pressure interface (41).

6. The multi-station vertical and horizontal bearing seal durability test bench according to claim 3 is characterized in that: The lower end of the bearing to be tested is detachably connected to a test fixture, and the lower end of the test fixture is provided with a transparent measuring tube (10). The transparent measuring tube (10) is an L-shaped tube structure, and a measuring tube scale is provided on the outer side wall of the horizontal section at the lower side.

7. The multi-station vertical and horizontal bearing seal durability test bench according to claim 6 is characterized in that: The test fixture comprises a matching flange (6), a transfer adjustment stud (7) and a quick-connect plug (8). The quick-connect plug (8) is fixed to the upper end of the transparent measuring tube (10) and is threadedly connected to the lower end of the transfer adjustment stud (7). The matching flange (6) is sleeved on the transfer adjustment stud (7) and fixed by screwing a set screw into the side. The transfer adjustment stud (7) is provided with a sealing ring and a connecting component, and the upper end of the transfer adjustment stud (7) is connected to the bottom of the box (45) through the connecting component.

8. The multi-station vertical and horizontal bearing seal durability test bench according to claim 7 is characterized in that: The connecting components are a plurality of magnets (9), and the plurality of magnets (9) are threadedly connected to the upper end surface of the transfer adjustment stud (7).

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