A position holding device and a method for installing a nut rack on a dewar base

Abstract

The present invention discloses a position holding device and a method for installing a nut rack on a dewar base. The position holding device includes a tube body, a support assembly, a first adjustment assembly, and a second adjustment assembly. The tube body includes an outer tube and an inner tube, and the inner tube is coaxially arranged inside the outer tube. The first adjustment assembly is arranged at the upper end of the inner tube. The support assembly is arranged at the lower end of the inner tube, and includes a first pin shaft, a second pin shaft, and a rotatable support plate. The lower end of the inner tube is provided with a first pin hole, and the first pin shaft is inserted into the first pin hole. The rotatable support plate is connected to the lower end of the outer tube through the second pin shaft and meshes with the first pin shaft. The second adjustment assembly is arranged on the outer wall of the outer tube. The tube body sequentially passes through the first inner hole of the base member and the second inner hole of the fixed member. The device can be adjusted according to the thickness of the base member and the thickness of the fixed member, and the fixed member can be quickly and conveniently fixed to the lower surface of the base member.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear industry, and in particular relates to a position holding device and a method for installing a nut rack on a dewar base. Background Art

[0002] During the installation phase of the International Thermonuclear Organization's fusion reactor, the poloidal coil support (TFGS) is evenly mounted on the "straight flange" of the dewar base, which resembles a giant circular water tank, using special studs and nuts. The typical installation sequence is to pass the studs through the flange and then tighten them with the nuts. According to the fusion reactor installation construction sequence, the poloidal coil support (TFGS) must be in place first, and pre-tightened after surrounding items are installed. However, the space below the flange is already occupied by various items, leaving no room or conditions for the nuts. Therefore, in practice, the nuts must first be temporarily secured to the underside of the dewar base. This involves placing all the nuts in a nut rack and temporarily securing the rack to the underside. Once the surrounding items are installed and the pre-tightening window arrives, workers thread the bolts into the nuts from above the flange before performing the subsequent pre-tightening operation.

[0003] In addition, the TFGS base is square and needs to be fixed on all four sides. The thickness of each side is different, and multiple bolts and nuts are required. The size and quantity of the bolts and nuts used on each side are different, making the entire installation process cumbersome, inconvenient and time-consuming. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art and provide a position holding device and a method for installing a nut rack on a Dewar base. The position holding device can be adjusted according to the thickness of the TFGS and the thickness of the nut rack, so that the fixed part (nut rack) can be fixed on the lower surface of the base part (Dewar base) conveniently and quickly.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a position maintaining device, comprising a tube body, a support assembly, a first adjustment assembly and a second adjustment assembly, wherein the tube body comprises an outer tube and an inner tube, and the inner tube is coaxially arranged inside the outer tube; the first adjustment assembly is arranged at the upper end of the inner tube, and is used to change the axial position of the inner tube so that the axial relative position of the inner tube and the outer tube changes; the support assembly is arranged at the lower end of the inner tube, and comprises a first pin shaft, a second pin shaft and a rotatable support plate, and the lower end of the inner tube is provided with a first pin hole, and the first pin shaft is passed through the first pin hole The rotatable support plate is connected to the lower end of the outer tube through the second pin shaft and meshes with the first pin shaft, and is used for changing its own position by rotating to support the bottom of the fixed part when the axial relative position of the inner tube and the outer tube changes; the second adjusting component is provided on the outer wall of the outer tube, and is used for changing the position of the device by cooperating with the base part to fix the fixed part on the lower surface of the base part when the rotatable support plate supports the bottom of the fixed part; wherein, the tube body passes through the first inner hole of the base part and the second inner hole of the fixed part in sequence.

[0007] Preferably, a first groove is provided at the lower end of the inner tube, a second groove is provided at the lower end of the outer tube at a position corresponding to the first groove, and the rotatable support plate is located in the first groove and the second groove; a second pin shaft hole is provided at the lower end of the outer tube, and the second pin shaft is inserted into the second pin shaft hole.

[0008] Preferably, the inner tube is arranged vertically, the first pin shaft is arranged horizontally, and the axis of the first pin shaft intersects with the axis of the inner tube, the second pin shaft is arranged parallel to the first pin shaft, and two rotatable support plates are used, and the two rotatable support plates are symmetrically arranged on both sides of the first pin shaft. The upper part of the rotatable support plate is in the outer tube and corresponds to the position of the first groove and the second groove, and the lower part of the rotatable support plate extends out from the outer tube.

[0009] Preferably, a thread is provided on the outer wall of the upper end of the outer tube, and a thread is provided on the outer wall of the upper end of the inner tube; the first adjusting assembly includes a first adjusting nut, a sleeve, and a plate, the first adjusting nut is threadedly connected to the outer wall of the outer tube, the sleeve is sleeved outside the inner tube, and its bottom is fixedly connected to the first adjusting nut, the plate is sleeved and fixed on the inner tube, a slot is provided on the sleeve, and the plate is inserted into the slot.

[0010] Preferably, the first adjusting assembly further includes a first nut, a second nut, a first washer, a second washer and a set screw. The first nut, the first washer, the second washer and the second nut are all sleeved on the outside of the inner tube. The first nut and the second nut are symmetrically arranged on both sides of the plate to clamp and fix the plate on the inner tube. The first washer is clamped between the first nut and the plate, and the second washer is clamped between the second nut and the plate. A screw hole is provided on the outer wall of the first adjusting nut, and the set screw fixes the sleeve and the first adjusting nut through the screw hole.

[0011] Preferably, a thread is provided within a preset range at the upper end of the outer wall of the outer tube; the second adjusting assembly includes a second adjusting nut, the second adjusting nut is threadedly connected to the outer wall of the outer tube, and the second adjusting nut is below the first adjusting nut; when the second adjusting nut is in contact with the upper surface of the base member, the second adjusting nut is rotated to move the outer tube upward, thereby fixing the fixed member on the lower surface of the base member.

[0012] Preferably, the second adjustment assembly further includes an adjustment washer, which is clamped between the second adjustment nut and the base member.

[0013] Preferably, a fixing area is provided within the threaded range on the outer wall of the outer tube, and the fixing area has no threads.

[0014] Preferably, a limiting hole is provided at the upper end of the outer tube.

[0015] In a second aspect, the present invention further provides a method for mounting a nut rack on a Dewar base, using the position holding device as described above, the method comprising:

[0016] Pass the lower end of the tube of the position holding device through the first center hole of the Dewar base and the second center hole of the nut rack in sequence;

[0017] Keeping the outer tube fixed, the first adjustment assembly is rotated to move the inner tube relative to the outer tube, so that the rotatable support plate changes its position to a horizontal position to support the bottom of the nut rack;

[0018] Rotate the second adjustment component until the second adjustment component is in contact with the Dewar base;

[0019] Keeping the outer tube fixed, rotate the second adjustment assembly to move the tube body of the position holding device upward until the nut holder fits against the lower surface of the Dewar base;

[0020] Rotating the first adjustment assembly again to move the inner tube relative to the outer tube, so that the rotatable support plate changes its position to a vertical position to release the bottom of the nut rack;

[0021] The tube body of the position holding device is pulled out from the first center hole of the Dewar base and the second center hole of the nut rack.

[0022] The position holding device in the present invention has a simple structure. The nut rack is supported by adjusting the rotation angle of the rotatable support plate. The position holding device can be removed from above the Dewar base after the nut is installed, thereby avoiding the problem of being unable to position the nut after other components are installed between the nut rack and the Dewar base.

[0023] The method for installing the nut rack on the dewar base of the present invention is simple and convenient to operate, and the method is highly efficient in installing the nuts, which can effectively save manpower. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a front view of the position holding device in Example 1 of the present invention;

[0025] FIG2(A) is a schematic diagram of a rotatable support plate in a horizontal position in Example 2 of the present invention;

[0026] FIG2(B) is a schematic diagram of a rotatable support plate in a vertical position in Example 2 of the present invention;

[0027] FIG3(A) is a schematic diagram of installation using a position holding device in Example 2 of the present invention;

[0028] FIG3(B) is a schematic diagram of installation using a position holding device in Example 2 of the present invention;

[0029] FIG3(C) is a schematic diagram of installation using a position holding device in Example 2 of the present invention;

[0030] FIG3(D) is a schematic diagram of installation using a position holding device in Example 2 of the present invention;

[0031] FIG3(E) is a schematic diagram of installation using a position holding device in Example 2 of the present invention;

[0032] FIG3(F) is a schematic diagram of installation using a position holding device in Example 2 of the present invention.

[0033] In the figure: 1-inner tube, 2-first nut, 3-first gasket, 4-plate, 5-second gasket, 6-second nut, 7-sleeve, 8-set screw, 9-first adjusting nut, 10-outer tube, 11-second adjusting nut, 12-adjusting pad, 13-first pin, 14-second pin, 15-rotatable support plate, 16-TFGS base, 17-nut holder, 18-nut, 19-stud, 20-position holding device. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of the present invention.

[0035] In the description of the present invention, it should be noted that the term "upper" and the like to indicate an orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience and simplification of 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 the present invention.

[0036] In the description of the present invention, the terms “first” and “second” are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connect," "dispose," "install," "fix," etc. should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integral connection; they may refer to direct connection, indirect connection through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0038] During the installation process of the existing polar coil support TFGS, it is necessary to evenly install it on the "straight flange" of the Dewar base, which is similar to a huge circular water tank, using special stud bolts and nuts. Since the entire installation process is cumbersome, inconvenient and time-consuming, the inventors of this application thought of providing a device that can fix the nut rack to the lower surface of the "straight flange" of the Dewar base, and after the pre-tightening and fixing operation is completed, the device can be easily removed.

[0039] Specifically, the present invention provides a position holding device, comprising a tube body, a support assembly, a first adjustment assembly, and a second adjustment assembly, wherein the tube body comprises an outer tube and an inner tube.

[0040] The inner tube is coaxially disposed inside the outer tube;

[0041] The first adjustment component is provided at the upper end of the inner tube and is used to change the axial position of the inner tube so as to change the relative axial position of the inner tube and the outer tube;

[0042] The support assembly is provided at the lower end of the inner tube, and includes a first pin shaft, a second pin shaft and a rotatable support plate.

[0043] A first pin hole is provided at the lower end of the inner tube, and the first pin shaft is passed through the first pin hole. The rotatable support plate is connected to the lower end of the outer tube via the second pin shaft and meshes with the first pin shaft, and is used to change its position by rotating to support the bottom of the fixed component when the axial relative position of the inner tube and the outer tube changes;

[0044] The second adjustment assembly is provided on the outer wall of the outer tube and is used to change the position of the device by cooperating with the base member to fix the fixed member on the lower surface of the base member when the rotatable support plate supports the bottom of the fixed member;

[0045] Wherein, the tube body passes through the first inner hole of the base component and the second inner hole of the fixed component in sequence.

[0046] Example 1

[0047] like Figure 1 As shown, this embodiment discloses a position holding device, including a tube body, a support assembly, a first adjustment assembly and a second adjustment assembly. The tube body includes an outer tube 10 and an inner tube 1, and the inner tube 1 is coaxially arranged inside the outer tube 10; the first adjustment assembly is arranged at the upper end of the inner tube 1, and is used to change the axial position of the inner tube 1 so that the axial relative position of the inner tube 1 and the outer tube 10 changes; the support assembly is arranged at the lower end of the inner tube 1, and includes a first pin shaft 13, a second pin shaft 14 and a rotatable support plate 15, and the lower end of the inner tube 1 is provided with a first pin hole, and the first pin shaft 13 is passed through the first pin hole. In the hole, the rotatable support plate 15 is connected to the lower end of the outer tube 10 through the second pin shaft 14 and engages with the first pin shaft 13. It is used to change its own position by rotating to support the bottom of the fixed part when the axial relative position of the inner tube 1 and the outer tube 10 changes; the second adjustment component is provided on the outer wall of the outer tube 10, and is used to change the position of the device by cooperating with the base part to fix the fixed part on the lower surface of the base part when the rotatable support plate 15 supports the bottom of the fixed part; wherein, the tube body passes through the first inner hole of the base part and the second inner hole of the fixed part in sequence.

[0048] A first groove is provided at the lower end of the inner tube 1, and a second groove is provided at the lower end of the outer tube 10 at a position corresponding to the first groove. The rotatable support plate 15 is located in both the first groove and the second groove; a second pin shaft hole is provided at the lower end of the outer tube 10, and the second pin shaft 14 is inserted into the second pin shaft hole.

[0049] The inner tube 1 is arranged vertically, the first pin shaft 13 is arranged horizontally, and the axis of the first pin shaft 13 intersects with the axis of the inner tube 1, the second pin shaft 14 is arranged parallel to the first pin shaft 13, and two rotatable support plates 15 are arranged opposite to each other. The two rotatable support plates 15 are symmetrically arranged on both sides of the first pin shaft 13. The upper part of the rotatable support plate 15 is in the outer tube 10 and corresponds to the position of the first groove and the second groove. The lower part of the rotatable support plate 15 extends out from the outer tube 10.

[0050] In this embodiment, specifically, the upper part of the rotatable support plate 15 is rotatably connected to the second pin shaft 14, the shape of the upper part is configured to be able to engage with the first pin shaft 13, and the lower part of the rotatable support plate 15 is in the shape of a long strip. In the natural state, the rotatable support plate 15 is placed in the vertical direction. In the working state, the rotatable support plate 15 is placed in the horizontal direction to support the bottom of the fixed part.

[0051] The first adjustment component can be used to adjust the axial relative position of the inner and outer tubes, thereby changing the opening and closing angle between the two rotatable support plates 15. The materials and specifications used in various parts of the device can also be adjusted to make the weight of the entire device support single-person use.

[0052] In this embodiment, the pin can be a cylinder, and the upper part of the rotatable support plate 15 can have a cavity to support the second pin 14 to pass through it. The first pin 13 is fixedly connected to the inner tube 1, and the upper part of the rotatable support plate 15 is engaged with the first pin 13. When the inner tube 1 and the outer tube 10 move axially relative to each other, since the rotatable support plate 15 is rotatably connected to the outer tube 10 through the second pin 14, the rotatable support plate 15 is driven by the first pin 13 to rotate around the second pin 14, and one end of the rotatable support plate 15 can be extended from the corresponding groove.

[0053] A thread is provided on the outer wall of the upper end of the outer tube 10, and a thread is provided on the outer wall of the upper end of the inner tube 1; the first adjusting assembly includes a first adjusting nut 9, a sleeve 7, and a plate 4. The first adjusting nut 9 is threadedly connected to the outer wall of the outer tube 10, the sleeve 7 is sleeved on the outside of the inner tube 1, and its bottom is fixed to the first adjusting nut 9. The plate 4 is sleeved and fixed on the inner tube 1, and a slot is opened on the sleeve 7, and the plate 4 is inserted into the slot.

[0054] The first adjusting assembly also includes a first nut 2, a second nut 6, a first gasket 3, a second gasket 5, a first nut 2, a first gasket 3, a second gasket 5 and a set screw 8; the first nut 2, the first gasket 3, the second gasket 5 and the second nut 6 are all sleeved on the outside of the inner tube 1, the first nut 2 and the second nut 6 are symmetrically arranged on both sides of the plate 4 to clamp and fix the plate 4 on the inner tube 1, the first gasket 3 is clamped between the first nut 2 and the plate 4, and the second gasket 5 is clamped between the second nut 6 and the plate 4; a screw hole is provided on the outer wall of the first adjusting nut 9, and the set screw 8 fixes the sleeve 7 and the first adjusting nut 9 through the screw hole.

[0055] In this embodiment, the plate 4 is fixed to the upper end of the inner tube and inserted into the slot on the sleeve 7. The bottom of the sleeve 7 is fixedly connected to the first adjusting nut 9. When the first adjusting nut 9 is rotated, the first adjusting nut 9 drives the sleeve 7 to move up and down, the sleeve 7 drives the plate 4 to move up and down, and the plate 4 drives the inner tube 1 to move up and down, thereby causing the axial relative position of the inner tube 1 and the outer tube 10 to change.

[0056] A thread is provided within a preset range at the upper end of the outer wall of the outer tube 10; the second adjusting assembly includes a second adjusting nut 11, which is threadedly connected to the outer wall of the outer tube 10, and the second adjusting nut 11 is below the first adjusting nut 9; when the second adjusting nut 11 is in contact with the upper surface of the base member, the second adjusting nut 11 is rotated to move the outer tube 10 upward, thereby fixing the fixed member on the lower surface of the base member.

[0057] In this embodiment, when the second adjusting nut 11 is in contact with the base member, the second adjusting nut 11 continues to be rotated so that the second adjusting nut 11 moves downward relative to the outer tube 10. Since the base member is fixed and the second adjusting nut 11 cannot move downward, the force generated by rotating the second adjusting nut 11 can drive the position maintaining device to move upward.

[0058] The second adjustment assembly further includes an adjustment washer 12 , which is sandwiched between the second adjustment nut 11 and the base member.

[0059] In this embodiment, the adjustment washer 12 and the outer tube 10 are not fixedly connected, so as to reduce friction between the second adjusting nut 11 and the base member during rotation.

[0060] A fixing area is provided within the threaded area on the outer wall of the outer tube 10. This fixing area is unthreaded. In this embodiment, the unthreaded fixing area is used to be clamped by a clamping tool to prevent the outer tube 10 from rotating when the user tightens the nut. The unthreaded fixing area can be cut out from the threaded area.

[0061] A limiting hole may also be provided on the upper end of the outer tube 10. In this embodiment, the limiting hole is used to indicate the position of the first adjusting nut 9 to prevent the user from exceeding the position of the limiting hole when screwing the first adjusting nut 9.

[0062] The position retaining device provided in this embodiment has a simple structure and is easy to operate. It can be removed from the top of the Dewar base after the nut is installed, avoiding the problem of being unable to reposition the nut after installing other components between the nut holder and the Dewar base. Furthermore, the use of this device is highly efficient in nut installation, effectively saving labor costs.

[0063] Example 2

[0064] As shown in FIG2 , this embodiment discloses a method for mounting a nut rack on a Dewar base, using the position holding device described in Example 1, wherein the fixed member is the nut rack and the base member is the Dewar base (TFGS base). The method includes:

[0065] Pass the lower end of the tube of the position holding device through the first center hole of the Dewar base and the second center hole of the nut rack in sequence;

[0066] As shown in FIG2(A), the outer tube is kept from rotating and the first adjustment assembly is rotated to move the inner tube relative to the outer tube so that the rotatable support plate changes its position to a horizontal position to support the bottom of the nut rack.

[0067] In this embodiment, when the rotatable support plate supports the nut rack, components required by the user can be installed between the nut rack and the Dewar base, and then the bolts can be screwed in for pre-tightening.

[0068] Rotate the second adjustment assembly until the second adjustment assembly fits into the Dewar base;

[0069] Keeping the outer tube fixed, rotate the second adjustment assembly to move the tube of the position holding device upward until the nut holder fits against the lower surface of the Dewar base;

[0070] In this embodiment, the outer tube can be prevented from rotating when the nut is screwed by clamping the fixing area on the outer tube with a clamping tool.

[0071] As shown in FIG2(B), the first adjustment assembly is rotated again to move the inner tube relative to the outer tube so that the rotatable support plate changes its position to a vertical position to release the bottom of the nut rack;

[0072] Pull the tube body of the position holding device out of the first center hole of the Dewar base and the second center hole of the nut rack.

[0073] In this embodiment, after the nut rack is fixed to the Dewar base, it is impossible to enter the bottom of the nut rack. The first adjustment component can be rotated from the Dewar base to allow the rotatable support plate to change its position to a vertical position and then the position holding device can be pulled out.

[0074] In a specific embodiment, two position holding devices can be used to fix the TFGS base and the nut rack. As shown in Figure 3, there are five holes numbered 1, 2, 3, 4, and 5 on the TFGS base 16 and the nut rack, respectively, and nuts 18 are placed in the five holes of the nut rack 17.

[0075] As shown in FIG. 3(A) , the position holding device 20 passes through the nut rack 17 and the TFGS base 16 in the hole 2 and the hole 4 , respectively, so that the nut rack 17 is attached to the lower surface of the TFGS base 16 .

[0076] 3 (B), FIG3 (C) and FIG3 (D), without changing the state of the two position holding devices 20, the studs 19 and nuts 18 are screwed into the holes 1, 3, 5 respectively and fixed.

[0077] 3 (E) and FIG. 3 (F), respectively, remove the position holding device 20 at the hole 2 and the hole 4, and then sequentially screw the stud 19 and the nut 18 into the hole 2 and the hole 4 to complete the installation process.

[0078] The method in this embodiment is simple and convenient to operate, and the method is highly efficient in installing the nut. It is also possible to remove the position holding device from above the Dewar base after the nut is installed, thereby avoiding the problem of being unable to position the nut after other components are installed between the nut rack and the Dewar base.

[0079] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A position holding device, characterized in that: It comprises a tube body, a support assembly, a first adjustment assembly and a second adjustment assembly, wherein the tube body comprises an outer tube (10) and an inner tube (1). The inner tube (1) is coaxially placed inside the outer tube (10); The first adjustment component is provided at the upper end of the inner tube (1) and is used to change the axial position of the inner tube (1) so as to change the axial relative position of the inner tube (1) and the outer tube (10); The support assembly is provided at the lower end of the inner tube (1), and comprises a first pin (13), a second pin (14) and a rotatable support plate (15). The lower end of the inner tube (1) is provided with a first pin hole, the first pin shaft (13) is passed through the first pin hole, the rotatable support plate (15) is connected to the lower end of the outer tube (10) via the second pin shaft (14), and is engaged with the first pin shaft (13), and is used to change its own position by rotating to support the bottom of the fixed part when the axial relative position of the inner tube (1) and the outer tube (10) changes; The second adjustment component is provided on the outer wall of the outer tube (10) and is used for changing the position of the device by cooperating with the base member to fix the fixed member on the lower surface of the base member when the rotatable support plate (15) supports the bottom of the fixed member; Wherein, the tube body passes through the first inner hole of the base member and the second inner hole of the fixed member in sequence; A first groove is formed at the lower end of the inner tube (1), a second groove is formed at the lower end of the outer tube (10) at a position corresponding to the first groove, and the rotatable support plate (15) is located in the first groove and the second groove; A second pin shaft (14) hole is provided at the lower end of the outer tube (10), and the second pin shaft (14) is inserted into the second pin shaft (14) hole; The inner tube (1) is arranged vertically, the first pin shaft (13) is arranged horizontally, and the axis of the first pin shaft (13) intersects with the axis of the inner tube (1). The second pin shaft (14) is arranged parallel to the first pin shaft (13), Two rotatable support plates (15) are used, and the two rotatable support plates (15) are symmetrically arranged on both sides of the first pin shaft (13). The upper part of the rotatable support plate (15) is located in the outer tube (10) and corresponds to the position of the first groove and the second groove. The lower part of the rotatable support plate (15) extends out of the outer tube (10).

2. The position holding device according to claim 1, characterized in that: The outer wall of the upper end of the outer tube (10) is provided with a thread, and the outer wall of the upper end of the inner tube (1) is provided with a thread; The first adjustment assembly comprises a first adjustment nut (9), a sleeve (7), and a plate (4). The first adjusting nut (9) is threadedly connected to the outer wall of the outer tube (10). The sleeve (7) is sleeved outside the inner tube (1), and its bottom is fixedly connected to the first adjusting nut (9). The plate (4) is fitted onto and fixed on the inner tube (1). The sleeve (7) is provided with a slot, and the plate (4) is inserted into the slot.

3. The position holding device according to claim 2, characterized in that: The first adjustment assembly further comprises a first nut (), a second nut (6), a first washer (3), a second washer (5) and a set screw (8). The first nut (2), the first gasket (3), the second gasket (5) and the second nut (6) are all mounted on the outside of the inner tube (1); the first nut (2) and the second nut (6) are symmetrically arranged on both sides of the plate (4) to clamp and fix the plate (4) on the inner tube (1); the first gasket (3) is clamped between the first nut (2) and the plate (4); and the second gasket (5) is clamped between the second nut (6) and the plate (4); The outer wall of the first adjusting nut (9) is provided with a screw hole, and the set screw (8) is passed through the screw hole to fix the sleeve (7) and the first adjusting nut (9).

4. The position holding device according to claim 2, characterized in that: A thread is provided within a preset range at the upper end of the outer wall of the outer tube (10); The second adjustment assembly comprises a second adjustment nut (11), the second adjustment nut (11) being threadedly connected to the outer wall of the outer tube (10), and the second adjustment nut (11) being located below the first adjustment nut (9); When the second adjusting nut (11) is in contact with the upper surface of the base member, the second adjusting nut (11) is rotated to move the outer tube (10) upward, thereby fixing the fixed member on the lower surface of the base member.

5. The position holding device according to claim 4, characterized in that: The second adjustment component further includes an adjustment pad (12), The adjustment pad (12) is clamped between the second adjustment nut (11) and the base member.

6. The position holding device according to claim 4, characterized in that: A fixing area is provided within the threaded range on the outer wall of the outer tube (10), and the fixing area has no threads.

7. The position holding device according to claim 1, characterized in that: A limiting hole is provided at the upper end of the outer tube (10).

8. A method for installing a nut rack on a Dewar base, characterized in that: Using the position holding device according to any one of claims 1 to 7, the method comprises: Pass the lower end of the tube of the position holding device through the first center hole of the Dewar base and the second center hole of the nut rack in sequence; Keeping the outer tube fixed, the first adjustment assembly is rotated to move the inner tube relative to the outer tube, so that the rotatable support plate changes its position to a horizontal position to support the bottom of the nut rack; Rotate the second adjustment component until the second adjustment component is in contact with the Dewar base; Keeping the outer tube fixed, rotate the second adjustment assembly to move the tube body of the position holding device upward until the nut holder fits against the lower surface of the Dewar base; Rotating the first adjustment assembly again to move the inner tube relative to the outer tube, so that the rotatable support plate changes its position to a vertical position to release the bottom of the nut rack; The tube body of the position holding device is pulled out from the first center hole of the Dewar base and the second center hole of the nut rack.

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