Seal isolation valve, vacuum apparatus, and seal isolation method

Abstract

The application provides a sealing isolation valve, a vacuum device and a sealing isolation method, relates to the technical field of sealing isolation, and is used for controlling the communication and isolation of a cavity and the outside world. The sealing isolation valve comprises a valve body, an isolation panel and a locking device. The valve body is arranged at the opening of the cavity. The isolation panel is pivotally arranged on the valve body. The isolation panel is suitable for controlling the communication and isolation of the cavity and the outside world by rotating around a first rotation axis. The locking device is suitable for driving the isolation panel to rotate around a second rotation axis. The first rotation axis is perpendicular to the second rotation axis. The sealing isolation valve, the vacuum device and the sealing isolation method provided by the application can solve the problem that the vacuum degree of the vacuum environment obtained by the sealing mode in the prior art is low.

Description

Technical Field

[0001] This invention relates to the field of sealing technology, and more specifically, to a sealing isolation valve, a vacuum device, and a sealing isolation method. Background Technology

[0002] Many cutting-edge technologies require a vacuum environment, which is primarily achieved through vacuum valves, vacuum pumps, and electronically controlled isolation assemblies. The core functional components of the vacuum valve are located at the interface between the vacuum and atmosphere, and the quality of its seal directly determines the vacuum level of the created environment. Current sealing methods produce vacuum environments with relatively low vacuum levels and can even lead to water leakage. Summary of the Invention

[0003] The problem solved by this invention is that the vacuum level of the vacuum environment obtained by the sealing method of the prior art is low.

[0004] To address the aforementioned problems, the present invention provides a sealing isolation valve for controlling the connection and isolation between a cavity and the outside world. The valve includes a valve body, an isolation panel, and a locking device. The valve body is disposed at the opening of the cavity. The isolation panel is pivotally disposed on the valve body. The isolation panel is adapted to control the connection and isolation between the cavity and the outside world by rotating about a first rotation axis. The locking device is adapted to drive the isolation panel to rotate about a second rotation axis, wherein the first rotation axis is perpendicular to the second rotation axis.

[0005] Furthermore, the sealing isolation valve also includes a support ring, which surrounds the opening of the cavity and is integrally formed with the valve body. The isolation panel is adapted to isolate the cavity from the outside world by abutting against the support ring.

[0006] Furthermore, the sealing isolation valve also includes a first sealing ring, the contact surface between the isolation panel and the support ring is collinear with any surface passing through the second rotation axis and forms a Z-shape, the first sealing ring is disposed between the isolation panel and the support ring, and the first sealing ring is collinear with any surface passing through the second rotation axis and forms a Z-shape.

[0007] Furthermore, the sealing isolation valve also includes a second sealing ring. A sealing groove is provided on the isolation panel, and the second sealing ring is disposed between the isolation panel and the support ring. The second sealing ring is disposed in the sealing groove and is located inside the first sealing ring.

[0008] Furthermore, the sealing isolation valve also includes a push-pull device, one end of which is connected to the valve body and the other end of which is connected to the isolation panel. The push-pull device is adapted to drive the isolation panel to rotate around a first rotation axis.

[0009] Furthermore, the push-pull device is adapted to drive the isolation panel to abut against the support ring with a first thrust, and the locking device is adapted to drive the isolation panel to rotate around the second rotation axis after the isolation panel and the support ring abut against each other. The push-pull device is also adapted to drive the isolation panel to rotate around the first rotation axis with a second thrust when the locking device drives the isolation panel to rotate around the second rotation axis.

[0010] Furthermore, the locking device includes a first rotating ring and a second rotating ring. The first rotating ring is fixedly connected to the isolation panel, and the second rotating ring is connected to the first rotating ring via gears. The second rotating ring is adapted to drive the first rotating ring to rotate around the second rotating shaft.

[0011] Furthermore, the locking device also includes a rotating hinge seat, a locking electric cylinder, and a locking fixing plate. The rotating hinge seat is fixedly connected to the second rotating ring, and the locking fixing plate is fixedly connected to the valve body. The locking electric cylinder includes a locking cylinder body and a locking push rod. The locking cylinder body is fixedly connected to the locking fixing plate, and the locking push rod is fixedly connected to the rotating hinge seat. The locking push rod is adapted to move relative to the locking cylinder body, thereby driving the second rotating ring to move relative to the valve body.

[0012] The present invention also provides a vacuum device, including a vacuum chamber and a sealing isolation valve provided in the embodiments of the present invention. The sealing isolation valve is disposed on the vacuum chamber and is suitable for controlling the connection and isolation between the vacuum chamber and the outside world.

[0013] The present invention also provides a sealing and isolation method, which uses the sealing and isolation valve provided by the present invention to seal and isolate a cavity, comprising: driving the isolation panel of the sealing and isolation valve disposed at the opening of the cavity to rotate around a first rotation axis with a first thrust to isolate the cavity from the outside; applying a second thrust in the same direction as the first thrust to the isolation panel, and simultaneously driving the isolation panel to rotate around a second rotation axis, wherein the first rotation axis is perpendicular to the second rotation axis.

[0014] The sealing isolation valve, vacuum equipment, and sealing isolation method provided in this invention, after the isolation panel is driven to rotate around the first rotation axis by the first thrust to cover the opening of the cavity, the locking device rotates the isolation panel to rotate around the second rotation axis perpendicular to the first rotation axis, and at the same time continues to apply a second thrust in the same direction as the first thrust to the isolation panel, thereby achieving a better sealing effect. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the sealing isolation valve and cavity assembly in a preferred embodiment of the present invention.

[0016] Figure 2 for Figure 1 A sectional view along AA.

[0017] Figure 3 for Figure 2Enlarged view of the middle section I.

[0018] Figure 4 for Figure 1 Right view of the sealing isolation valve.

[0019] Figure 5 for Figure 4 A schematic diagram of the push-pull mechanism.

[0020] Figure 6 for Figure 4 A schematic diagram of the structure of the second rotating ring.

[0021] Figure 7 for Figure 6 Enlarged view of section III.

[0022] Figure 8 for Figure 4 Enlarged view of the middle part II.

[0023] Explanation of reference numerals in the attached figures:

[0024] 100 - Sealed isolation valve, 101 - Bolt, 110 - Valve body, 113 - Panel hinge;

[0025] 130-Isolation panel, 133-Hinge plate, 135-Isolation panel, 137-Sealing groove, 139-Slide rail tooth groove;

[0026] 150-Locking device, 151-First rotating ring, 151a-Locking tooth, 152-Second rotating ring, 154-Push-pull mechanism, 155-Locking electric cylinder, 155a-Locking cylinder body, 155b-Locking push rod, 156-Rotating hinge seat, 157-Locking fixing plate, 158-Inverted slide rail;

[0027] 170-Push-pull device, 171-Push-pull cylinder, 173-Push-pull rod, 175-First hinge, 177-Second hinge;

[0028] 190-Support ring, 191-Outer ring, 193-Inner ring, 195-First sealing ring, 197-Second sealing ring;

[0029] 300 - cavity, 301 - opening;

[0030] L1 - First rotating axis, L2 - Second rotating axis. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] In the description of this invention, it should be noted that the terms used in the various embodiments, such as "upper," "lower," "front," and "rear," which indicate orientation, are only used to simplify the description of the positional relationships based on the accompanying drawings and do not mean that the components and devices referred to must be operated in accordance with the specific orientations and defined operations, methods, and structures in the specification. Such directional terms do not constitute a limitation of this invention.

[0033] Furthermore, the terms "first" and "second" used in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0034] Please combine Figure 1 This invention provides a sealing isolation valve 100 for controlling the connection and isolation between the cavity 300 and the outside world.

[0035] Please combine Figure 2 The sealing isolation valve 100 provided in this embodiment of the invention includes a valve body 110, an isolation panel 130, and a locking device 150.

[0036] Please combine Figure 3 In this embodiment of the invention, the valve body 110 is disposed at the opening 301 of the cavity 300, the isolation panel 130 is pivotally disposed on the valve body 110, and the two ends of the locking device 150 are respectively connected to the valve body 110 and the isolation panel 130.

[0037] In this embodiment of the invention, the isolation panel 130 is adapted to control the communication and isolation between the cavity 300 and the outside world by rotating about a first rotation axis L1. For example, in a preferred embodiment of the invention, the isolation panel 130 rotates clockwise about the first rotation axis L1 to cover the opening 301 of the cavity 300, thereby isolating the cavity 300 from the outside world. The isolation panel 130 rotates counterclockwise about the first rotation axis L1 to separate from the opening 301 of the cavity 300, thereby allowing the cavity 300 to communicate with the outside world. It should be noted that... Figure 2 In the diagram, the first rotation axis L1 is perpendicular to the paper and is shown as a point.

[0038] Please combine Figure 4 In this embodiment of the invention, the locking device 150 is adapted to drive the isolation panel 130 to rotate about the second rotation axis L2. The first rotation axis L1 is perpendicular to the second rotation axis L2.

[0039] It can be understood that the locking device 150 drives the isolation panel 130 to rotate around the second rotation axis L2, which is perpendicular to the first rotation axis L1, so as to tighten the isolation panel 130 to the opening 301 of the cavity 300.

[0040] Specifically, in a preferred embodiment of the present invention, the locking device 150 applies a pushing force to the isolation panel 130, causing the isolation panel 130 to rotate around the second rotation axis L2. When the isolation panel 130 is tightened to the opening 301 of the cavity 300, the resistance to the rotation of the isolation panel 130 around the second rotation axis L2 increases, and the isolation panel 130 stops rotating under the action of the resistance, thereby achieving the tightening of the isolation panel 130 to the opening 301 of the cavity 300.

[0041] Please combine again Figure 2 In a preferred embodiment of the present invention, the sealing isolation valve 100 further includes a push-pull device 170, one end of which is connected to the valve body 110, and the other end of which is connected to the isolation panel 130. In a preferred embodiment of the present invention, the push-pull device 170 is telescopic, and the push-pull device 170 is adapted to drive the isolation panel 130 to rotate around the first rotation axis L1 by telescopic movement.

[0042] In a preferred embodiment of the present invention, the push-pull device 170 is an electric cylinder. The push-pull device 170 includes a push-pull cylinder body 171 and a push-pull rod 173. The push-pull cylinder body 171 is hinged to the valve body 110 via a first hinge 175, and the push-pull rod 173 is hinged to the isolation panel 130 via a second hinge 177. The central axis of the first hinge 175 is the first rotation axis L1, and the push-pull rod 173 is adapted to make linear motion within the push-pull cylinder body 171, thereby driving the isolation panel 130 to rotate around the first rotation axis L1.

[0043] Please combine again Figure 3 In a preferred embodiment of the present invention, the sealing isolation valve 100 further includes a support ring 190. The support ring 190 is disposed around the opening 301 of the cavity 300, and the isolation panel 130 is adapted to isolate the cavity 300 from the outside world by abutting against the support ring 190. For example, in a preferred embodiment of the present invention, the isolation panel 130 rotates clockwise about the first rotation axis L1 and abuts against the support ring 190, thereby isolating the cavity 300 from the outside world. The isolation panel 130 rotates counterclockwise about the first rotation axis L1 and separates from the support ring 190, thereby allowing the cavity 300 to communicate with the outside world.

[0044] In a preferred embodiment of the present invention, the support ring 190 is integrally formed with the valve body 110, thereby enhancing the sealing effect of the sealing isolation valve 100.

[0045] like Figure 3As shown, in a preferred embodiment of the present invention, the isolation panel 130 and the valve body 110 are hinged together by a panel hinge 113. Specifically, the isolation panel 130 includes a hinge plate 133 and an isolation plate 135, which are staggered and integrally formed. The hinge plate 133 and the isolation plate 135 are hinged together with the valve body 110 by the panel hinge 113. In other embodiments of the present invention, the hinge plate 133 and the isolation plate 135 can also be fixedly connected by bolts 101.

[0046] In a preferred embodiment of the present invention, the support ring 190 includes an outer ring 191 and an inner ring 193, which are staggered and integrally formed. When the isolation panel 130 covers the opening 301 of the cavity 300, the hinge plate 133 abuts against the outer ring 191, and the isolation plate 135 abuts against the inner ring 193.

[0047] In a preferred embodiment of the present invention, the contact surfaces of the isolation panel 130 and the support ring 190 are collinear with any surface passing through the second rotation axis L2 in a Z-shape.

[0048] In a preferred embodiment of the present invention, the sealing isolation valve 100 further includes a first sealing ring 195, which is disposed between the isolation panel 130 and the support ring 190. The first sealing ring 195 is collinear with any surface passing through the second rotation axis L2 in a Z-shape.

[0049] In a preferred embodiment of the present invention, a sealing groove 137 is provided on the isolation panel 130. The sealing groove 137 is annular, and the cross-section of the sealing groove is rectangular.

[0050] In a preferred embodiment of the present invention, the sealing isolation valve 100 further includes a second sealing ring 197, which is disposed between the isolation panel 130 and the support ring 190, and is disposed within the sealing groove 137. The second sealing ring 197 is located within the first sealing ring 195.

[0051] In a preferred embodiment of the present invention, the first sealing ring 195 and the second sealing ring 197 are both made of metal or rubber.

[0052] Please combine again Figure 4 In a preferred embodiment of the present invention, the locking device 150 includes a first rotating ring 151 and a second rotating ring 152.

[0053] In a preferred embodiment of the present invention, the first rotating ring 151 is fixedly connected to the isolation panel 130. Specifically, the first rotating ring 151 is fixedly connected to the isolation panel 130 by bolts 101.

[0054] Please combine Figure 5In a preferred embodiment of the present invention, the locking device 150 further includes a push-pull mechanism 154, through which the second rotating ring 152 is connected to the valve body 110. Specifically, the push-pull mechanism 154 includes a rotating hinge seat 156, a locking electric cylinder 155, and a locking fixing plate 157. The rotating hinge seat 156 is fixedly connected to the second rotating ring 152, and the locking fixing plate 157 is fixedly connected to the valve body 110. The locking electric cylinder 155 includes a locking cylinder body 155a and a locking push rod 155b. The locking cylinder body 155a is fixedly connected to the locking fixing plate 157, and the locking push rod 155b is fixedly connected to the rotating hinge seat 156. The locking push rod 155b is adapted to make linear motion within the locking cylinder body 155a, thereby driving the second rotating ring 152 to move relative to the valve body 110.

[0055] Please combine Figure 6 In a preferred embodiment of the present invention, the locking device 150 further includes an inverted slide rail 158, and a slide rail groove 139 is provided on the isolation panel 130. The inverted slide rail 158 is slidably fixed in the slide rail groove 139. In a preferred embodiment of the present invention, the second rotating ring 152 is rectangular, and the locking device 150 includes four inverted slide rails 158. The four inverted slide rails 158 are respectively fixed to the four corners of the second rotating ring 152 by bolts 101. The inverted slide rails 158 are adapted to cooperate with the slide rail groove 139 to guide the second rotating ring 152 to rotate around the second rotating axis L2.

[0056] Please combine Figure 7 and Figure 8 In a preferred embodiment of the present invention, the second rotating ring 152 is connected to the first rotating ring 151 by gears, and the second rotating ring 152 is adapted to drive the first rotating ring 151 to rotate around the second rotating shaft L2.

[0057] Specifically, the second rotating ring 152 is provided with multiple embedded roller (not shown) assemblies 159, and the first rotating ring 151 is provided with multiple locking teeth 151a. The embedded roller (not shown) assemblies 159 are fixedly connected to the second rotating ring 152, and the embedded roller (not shown) assemblies 159 are adapted to roll on the isolation panel 130. The multiple locking teeth 151a are integrally formed with the first rotating ring 151. The multiple embedded roller (not shown) assemblies 159 are respectively connected to the corresponding locking teeth 151a gears.

[0058] It is understood that the push-pull mechanism 154 drives the second rotating ring 152 to rotate relative to the valve body 110, the second rotating ring 152 drives the embedded roller (not shown) assembly 159 to move, and the embedded roller (not shown) assembly 159 drives the locking tooth 151a, thereby driving the first rotating ring 151 to rotate around the second rotating shaft L2.

[0059] In a preferred embodiment of the present invention, the embedded roller (not shown) assembly 159 includes a slotted roller (not shown), a roller (not shown), and a thrust retainer (not shown). The slotted roller (not shown) is rotatably disposed on the second rotating ring 152, the roller (not shown) is sleeved on one end of the slotted roller (not shown), and the thrust retainer (not shown) is sleeved on the other end of the slotted roller (not shown). The roller (not shown) can rotate relative to the slotted roller (not shown).

[0060] In a preferred embodiment of the present invention, the sealing isolation valve 100 further includes a control panel (not shown). The control panel (not shown) is adapted to display the status of the sealing isolation valve 100 and receive instructions from the operator. The control panel (not shown) is provided with a "seal" button, a "lock" button, a "stop 1" button, a "stop 2" button, an "unload" button, and a "return" button.

[0061] This invention also provides a vacuum device, including a vacuum chamber and a sealing isolation valve 100 provided in this invention. The sealing isolation valve 100 is disposed on the vacuum chamber and is adapted to control the connection and isolation between the vacuum chamber and the outside world.

[0062] This invention also provides a sealing and isolation method, which uses the sealing and isolation valve provided in this invention to seal and isolate the cavity 300, including:

[0063] Step 1: Drive the isolation panel 130 of the sealing isolation valve 100 located at the opening 301 of the cavity 300 to rotate around the first rotating shaft L1 with the first thrust so that the cavity 300 is isolated from the outside.

[0064] Step 2: Apply a second thrust in the same direction as the first thrust to the isolation panel 130, and simultaneously drive the isolation panel 130 to rotate around the second rotation axis L2, with the first rotation axis L1 perpendicular to the second rotation axis L2;

[0065] When the isolation panel 130 is not closed at the opening 301 of the cavity 300, the push-pull rod 173 controlled by the push-pull electric cylinder is at the minimum stroke position, the embedded roller (not shown) assembly 159 on the second rotating ring 152 does not contact the locking tooth 151a, and the push-pull electric cylinder and the locking electric cylinder 155 are in the de-energized state.

[0066] In a preferred embodiment of the present invention, step one specifically includes:

[0067] Turn on the power to the push-pull electric cylinder, causing the push-pull rod 173 to move outward relative to the push-pull cylinder body 171, thereby driving the isolation panel 130 to rotate around the panel hinge 113 and close at the opening 301 of the cavity 300.

[0068] Step two specifically includes:

[0069] When the isolation panel 130 closes at the opening 301 of the cavity 300, the isolation panel 130 stops moving. At this time, the control panel (not shown) displays "Stroke reached". Click the "Seal" button on the control panel (not shown) to cause the push-pull electric cylinder to further drive the isolation panel 130 with a second thrust to seal the opening 301 of the cavity 300, and maintain this state. Turn on the power to the locking electric cylinder 155, causing it to drive the second rotating ring 152 to rotate clockwise and contact the locking teeth 151a on the first rotating ring 151. At this time, the control panel (not shown) again displays "Stroke reached". Click the "Lock" button to cause the locking electric cylinder 155 to control the locking push rod 155b to move outward relative to the locking cylinder body 155a. After 30 seconds, press the "Stop 1" and "Stop 2" buttons in sequence to stop the push-pull electric cylinder and the locking electric cylinder 155 from moving at the current stroke, and then disconnect the power.

[0070] The sealing and isolation method provided in this embodiment of the invention may further include step three, which specifically includes:

[0071] When it is necessary to open the isolation panel 130, click the "Unload" button on the control panel (not shown). The locking electric cylinder 155 controls the locking push rod 155b to retract relative to the locking cylinder body 155a, so that the second rotating ring 152 separates from the locking tooth 151a. Then click the "Return" button to flip the isolation panel 130 back to the initial position.

[0072] The sealing isolation valve 100, vacuum equipment, and sealing isolation method provided in this embodiment of the invention, after the isolation panel 130 is driven to rotate around the first rotation axis L1 by the first thrust to cover the opening 301 of the cavity 300, the locking device 150 rotates the isolation panel 130 so that it rotates around the second rotation axis L2 perpendicular to the first rotation axis L1, and at the same time continues to apply a second thrust in the same direction as the first thrust to the isolation panel, thereby achieving a better sealing effect.

[0073] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A sealing isolation valve for controlling the connection and isolation of a cavity (300) from the outside world, characterized in that, The device includes a valve body (110), an isolation panel (130), and a locking device (150). The valve body (110) is disposed at the opening (301) of the cavity (300). The isolation panel (130) is pivotally disposed on the valve body (110). The isolation panel (130) is adapted to control the communication and isolation between the cavity (300) and the outside world by rotating about a first rotation axis. The locking device (150) is adapted to drive the isolation panel (130) to rotate about a second rotation axis, wherein the first rotation axis is perpendicular to the second rotation axis. The locking device (150) includes a first rotating ring (151) and a second rotating ring (152). The first rotating ring (151) is fixedly connected to the isolation panel (130), and the second rotating ring (152) is connected to the first rotating ring (151) through gears. The second rotating ring (152) is adapted to drive the first rotating ring (151) to rotate around the second rotating shaft. The locking device (150) further includes a rotating hinge seat (156), a locking electric cylinder (155), and a locking fixing plate (157). The rotating hinge seat (156) is fixedly connected to the second rotating ring (152), and the locking fixing plate (157) is fixedly connected to the valve body (110). The locking electric cylinder (155) includes a locking cylinder body (155a) and a locking push rod (155b). The locking cylinder body (155a) is fixedly connected to the locking fixing plate (157), and the locking push rod (155b) is fixedly connected to the rotating hinge seat (156). The locking push rod (155b) is adapted to move relative to the locking cylinder body (155a) to drive the second rotating ring (152) to move relative to the valve body (110).

2. The sealing isolation valve according to claim 1, characterized in that, It also includes a support ring (190) which is arranged around the opening (301) of the cavity (300). The support ring (190) is integrally formed with the valve body (110). The isolation panel (130) is adapted to isolate the cavity (300) from the outside world by abutting against the support ring (190).

3. The sealing isolation valve according to claim 2, characterized in that, It also includes a first sealing ring (195), the contact surfaces of the isolation panel (130) and the support ring (190) are collinear with any surface passing through the second rotation axis and form a Z-shape, the first sealing ring (195) is disposed between the isolation panel (130) and the support ring (190), and the first sealing ring (195) is collinear with any surface passing through the second rotation axis and forms a Z-shape.

4. The sealing isolation valve according to claim 3, characterized in that, It also includes a second sealing ring (197), and the isolation panel (130) is provided with a sealing groove (137). The second sealing ring (197) is disposed between the isolation panel (130) and the support ring (190), and is disposed in the sealing groove (137). The second sealing ring (197) is located inside the first sealing ring (195).

5. The sealing isolation valve according to claim 2, characterized in that, It also includes a push-pull device (170), one end of which is connected to the valve body (110) and the other end of which is connected to the isolation panel (130). The push-pull device (170) is adapted to drive the isolation panel (130) to rotate around the first rotation axis.

6. The sealing isolation valve according to claim 5, characterized in that, The push-pull device (170) is adapted to drive the isolation panel (130) to abut against the support ring (190) with a first thrust. The locking device (150) is adapted to drive the isolation panel (130) to rotate around the second rotation axis after the isolation panel (130) abuts against the support ring (190). The push-pull device (170) is also adapted to drive the isolation panel (130) to rotate around the first rotation axis with a second thrust when the locking device (150) drives the isolation panel (130) to rotate around the second rotation axis.

7. A vacuum device, characterized in that, It includes a vacuum chamber and a sealing isolation valve as described in any one of claims 1-6, the sealing isolation valve being disposed on the vacuum chamber and adapted to control the communication and isolation between the vacuum chamber and the outside world.

8. A sealing and isolation method, comprising sealing and isolating a cavity (300) using a sealing and isolation valve as described in any one of claims 1-6, characterized in that, include: The isolation panel (130) of the sealing isolation valve located at the opening (301) of the cavity (300) is driven by a first thrust to rotate about a first rotation axis so that the cavity (300) is isolated from the outside. A second thrust is applied to the isolation panel (130) in the same direction as the first thrust, and the isolation panel (130) is driven to rotate about a second rotation axis, wherein the first rotation axis is perpendicular to the second rotation axis.

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