Connection box recycling structure
The detachable frame structure and ROV operation enable low-cost recovery of the subsea docking box, solving the problems of high cost and risk of false triggering, and is suitable for dynamic underwater environments.
Patent Information
- Application Number
- CN202423047884.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-10
- Publication Date
- 2025-10-17
- Estimated Expiration
- 2034-12-10
AI Technical Summary
Existing submarine docking box recovery solutions are expensive, carry the risk of false triggering of the acoustic releaser, and are not suitable for dynamic underwater environments.
A separate top frame and bottom frame structure is adopted. The frames are separated by cutting the connection lines or pulling the unhooker through ROV. The observation instruments are recovered by gravity and water surface traction, avoiding the use of acoustic releasers.
It achieves low-cost and reliable recovery of seabed observation instruments, is suitable for dynamic underwater environments, avoids the risk of false triggering of acoustic releasers, has a simple structure and is not restricted by seabed topography.
Smart Images
Figure CN223443732U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model is used in the field of connection box recycling technology, and particularly relates to a connection box recycling structure. BACKGROUND
[0002] The seabed connection box can carry related instruments and equipment, realize long-term placement on the seabed for in-situ observation, and can realize various functions according to different types of equipment carried by the seabed connection box. A typical seabed connection box should have an electronic cabin, a placement rack, an instrument, and an input cable. After the connection box completes its observation task, the electronic cabin carried by the connection box needs to be recycled. In the existing connection box recycling scheme, in addition to using a frogman or an underwater robot ROV to hang a hook, the automatic recycling structure is mainly realized in the form of carrying an acoustic release device to throw a load. This requires the connection box to be designed to ensure that the electronic cabin component to be recycled maintains positive buoyancy. When the acoustic release device on the placement rack carried by the instrument on the surface mother ship receives a release signal, the acoustic release device is unhooked and opened. At this time, the electronic cabin component group has positive buoyancy, and thus the electronic cabin can float up to the sea surface under the action of buoyancy. The relevant staff sail to the designated position to recycle the electronic cabin. This scheme needs to use an acoustic release device for recycling, and a set of acoustic release device costs as high as hundreds of thousands of yuan, making the overall cost of this recycling scheme expensive. In addition, the acoustic release device has a risk of false triggering. SUMMARY
[0003] The utility model discloses a connection box recycling structure, which is low in cost, firm and reliable in structure, and convenient for recycling of observation instruments.
[0004] The utility model discloses a connection box recycling structure, which is low in cost, firm and reliable in structure, and convenient for recycling of observation instruments.
[0005] A connection box recycling structure, comprising a top frame and a bottom frame that cooperate with each other, a space for containing observation instruments is formed between the top frame and the bottom frame, the top frame is used for connecting observation instruments, a connecting line is arranged between the top frame and the bottom frame, a first fixing part and a second fixing part are arranged on the bottom frame, the first fixing part and the second fixing part are arranged on opposite sides of the bottom frame, a first connecting part and a second connecting part are arranged on the top frame, the first connecting part and the second connecting part are arranged on opposite sides of the top frame, the first fixing part corresponds to the first connecting part and is located on one side of the top frame, the second fixing part corresponds to the second connecting part and is located on the other side of the top frame, one end of the connecting line is connected with the first fixing part, the other end of the connecting line passes through the first connecting part and the second connecting part in sequence and is connected with the second fixing part.
[0006] Preferably, the longitudinal section of the top frame is in the shape of a trapezoid with the top narrower than the bottom, the first connecting part and the second connecting part are located at the top corners of the top frame respectively, and the first fixing part and the second fixing part are located on the bottom frame near the bottom corners of the top frame respectively.
[0007] Preferably, the first fixing part and the second fixing part each comprise a shackle, the shackle comprises a lifting ring and a locking rod, the bottom frame is provided with a mounting hole, the locking rod passes through the mounting hole, and the two ends of the locking rod are connected with the lifting ring.
[0008] Preferably, the connecting line comprises a first rope section, a second rope section and a third rope section connected in sequence, the bottom end of the first rope section is connected with the first fixing part, the bottom end of the third rope section is connected with the second fixing part, one end of the second rope section is connected with the third rope section, and the other end of the second rope section is connected with the third rope section by passing through the first connecting part and the second connecting part.
[0009] Preferably, the first connecting part is provided with a first fixed pulley, the second connecting part is provided with a second fixed pulley, and the second rope section is wound on the first fixed pulley and the second fixed pulley.
[0010] Preferably, a decoupler is arranged between the first rope section and the second rope section, the decoupler comprises a fixed part, a hook part, an arm part and a locking pin, the hook part and the arm part are rotatably connected with the fixed part, the fixed part is provided with a lifting hole, the second rope section is connected with the fixed part through the lifting hole, the first rope section is connected with the hook part, and the locking pin can detachably connect the arm part and the hook part.
[0011] Preferably, a tensioner is arranged between the second rope section and the third rope section, the tensioner comprises a first tensioning arm, a sleeve and a second tensioning arm connected in sequence, the bottom end of the second rope section is connected with the first tensioning arm, the top end of the second tensioning arm is connected with the top end of the second tensioning arm, and the first tensioning arm and the second tensioning arm are threadedly connected with the two ends of the sleeve respectively.
[0012] Preferably, the top end of the first tensioning arm is provided with a first lifting lug, the second rope section is fixedly connected with the first tensioning arm through the first lifting lug, the bottom end of the first tensioning arm is provided with a first external thread, the top end of the sleeve is provided with a first internal thread matched with the first external thread, the bottom end of the second tensioning arm is provided with a second lifting lug, the third rope section is fixedly connected with the second tensioning arm through the second lifting lug, the top end of the second tensioning arm is provided with a second external thread, the bottom end of the sleeve is provided with a second internal thread matched with the second external thread, and the screw directions of the first internal thread and the second internal thread are opposite.
[0013] Preferably, the top end of the top layer frame is provided with a load-bearing head, the top end of the load-bearing head is connected with an input cable, and the top of the input cable is connected with a buoy.
[0014] Preferably, the top layer frame and the bottom layer frame are both rectangular in cross section, and the bottom layer frame is provided with limiting baffle plates at positions of four corners, and the limiting baffle plates are located at the outer periphery of the top layer frame.
[0015] One of the above technical solutions has at least one of the following advantages or beneficial effects: the connection box recovery device forms a split underwater connection box frame structure through the top layer frame and the bottom layer frame cooperating with each other, when recovery is needed, an ROV dives to the vicinity of the connection box recovery structure, and then the underwater ROV recovery cooperation operation is performed, that is, the ROV uses the hydraulic clamp carried thereby to cut all connection lines, after cutting, the bottom layer frame is separated from the top layer frame under the action of gravity, after the bottom layer frame is separated, the counterweight disappears, so that the underwater connection box completes the unloading, the top layer frame overcomes the adsorption force in the underwater recovery process, and drags the top layer frame to float up on the water surface, thereby realizing the recovery of the connection box, the connection box recovery structure is simple and ingenious in structure, low in cost, firm and reliable in structure, not limited by the seabed topography, does not need to install an acoustic release device in the recovery structure, avoids the risk of mis-triggering of the acoustic release device, and is suitable for the underwater connection box application scene of the buoy seabed base, which has large load weight and dynamic cable continuous dynamic effect.
[0016] Additional aspects and advantages of the present application will be described in part in the description that follows, and will become apparent from the description that follows, or will be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS
[0017] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the description of the embodiments, taken in conjunction with the following drawings:
[0018] Figure 1 is a perspective view of one embodiment of the present application;
[0019] Figure 2is Figure 1 a front view of one embodiment of the present application is shown.
[0020] Figure 3 is a front view of another embodiment of the present application. DETAILED DESCRIPTION
[0021] The present application will be described in detail below with reference to the preferred embodiments thereof, and the preferred embodiments of the present application are shown in the drawings, which serve to supplement the description of the text part of the specification and enable one skilled in the art to intuitively and visually understand each technical feature and the overall technical scheme of the present application, but cannot be understood as a limitation on the scope of protection of the present application.
[0022] In the present application, if the directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical scheme of the present application, and is not intended to indicate or imply that the indicated technical features must have a specific orientation, be constructed in a specific orientation and be operated, so it cannot be understood as a limitation on the present application.
[0023] In the present application, the meaning of "several" is one or more, the meaning of "multiple" is two or more, and "greater than", "less than", "exceeding" and the like are understood as not including the number; "above", "below", "within" and the like are understood as including the number. In the description of the present application, if "first" and "second" are described, they are only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.
[0024] In the present application, unless otherwise explicitly limited, the words "set", "install", "connect" and the like should be broadly understood, for example, they can be directly connected, or indirectly connected through an intermediate medium; they can be fixedly connected, or detachably connected, or integrally formed; they can be mechanically connected, or electrically connected or capable of communicating with each other; they can be the internal communication or interaction relationship of two elements. The skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical scheme.
[0025] Among them, Figure 1 A reference direction coordinate system of the embodiment of the present application is given, and the embodiment of the present application is described below in combination with the directions shown in Figure 1 and Figure 2 .
[0026] The embodiment of the present application provides a kind of docking box recycling structure, referring to Figure 1 and Figure 2, the top layer frame 100 and the bottom layer frame 200 are matched, the connection between the top layer frame 100 and the bottom layer frame 200 is matched in shape, a space for containing the observation instrument 700 is formed between the top layer frame 100 and the bottom layer frame 200, the top layer frame 100 is used for connecting the observation instrument 700, the connecting line 300 is arranged between the top layer frame 100 and the bottom layer frame 200, the first fixing part 210 and the second fixing part 220 are arranged on the bottom layer frame 200, the first fixing part 210 and the second fixing part 220 are oppositely arranged on two sides of the bottom layer frame 200, the first connecting part 110 and the second connecting part 120 are arranged on the top layer frame 100, the first connecting part 110 and the second connecting part 120 are oppositely arranged on two sides of the top layer frame 100, the first fixing part 210 and the first connecting part 110 are correspondingly arranged on one side of the top layer frame 100, the second fixing part 220 and the second connecting part 120 are correspondingly arranged on the other side of the top layer frame 100, one end of the connecting line 300 is connected with the first fixing part 210, the other end of the connecting line 300 passes through the first connecting part 110 and the second connecting part 120 in sequence and is connected with the second fixing part 220, the docking box recovery device forms a separated underwater docking box frame structure through the matched top layer frame 100 and the bottom layer frame 200, when recovery is needed, the ROV dives to the vicinity of the docking box recovery structure, and the underwater ROV recovery cooperation operation is performed, that is, the ROV uses the hydraulic clamp carried by the ROV to cut all the connecting lines 300, after cutting, the bottom layer frame 200 is separated from the top layer frame 100 under the action of gravity, after the bottom layer frame 200 is separated, the counterweight disappears, so that the underwater docking box completes the unloading, the top layer frame 100 overcomes the adsorption force in the underwater recovery process, and drags the top layer frame 100 to make the observation instrument 700 float on the water surface, thereby realizing the recovery of the docking box, the docking box recovery structure is simple and ingenious in structure, low in cost, firm and reliable in structure, not limited by the seabed topography, does not need to install an acoustic release device in the recovery structure, avoids the risk of mis-triggering of the acoustic release device, and is suitable for the underwater docking box application scene of the floating buoy seabed base, the underwater docking box has large counterweight, and the dynamic cable continuously acts dynamically.
[0027] In some embodiments, referring to Figure 2 , the longitudinal section of the top layer frame 100 is in the shape of a trapezoid with a narrow upper part and a wide lower part, the first connecting part 110 and the second connecting part 120 are respectively arranged at the positions of the top feet of the top layer frame 100, and the first fixing part 210 and the second fixing part 220 are respectively arranged at the positions close to the bottom corners of the top layer frame 100 on the bottom layer frame 200, the design enables the connecting line 300 to be arranged around the inner periphery of the docking box recovery structure, avoids occupying the space of the observation instrument 700, and enables the space between the top layer frame 100 and the bottom layer frame 200 to be larger, thereby facilitating the containing of the observation instrument 700.
[0028] Preferably, the first fixing part 210 and the second fixing part 220 each comprise a shackle 400, the shackle 400 comprising a lifting eye and a locking bar, the bottom frame 200 being provided with a mounting hole, the locking bar penetrating through the mounting hole, the two ends of the locking bar being connected with the lifting eye, the two ends of the connecting line 300 being connected with the first fixing part 210 and the second fixing part 220 through the lifting eye, the shackle 400 being capable of facilitating maintenance, replacement of parts or daily maintenance, through the shackle, the components needing repair or replacement can be conveniently accessed and handled, and in the assembly process, the shackle can be used to temporarily remove the connecting member, so as to adjust, position or install other components to the workpiece. It provides flexibility and convenience, so that the engineering personnel can effectively handle different assembly tasks.
[0029] Referring to Figure 2 , the connecting line 300 comprises a first rope section 310, a second rope section 320 and a third rope section 330 connected in sequence, the bottom end of the first rope section 310 being connected with the first fixing part 210, the bottom end of the third rope section 330 being connected with the second fixing part 220, one end of the second rope section 320 being connected with the third rope section 330, and the other end being connected with the third rope section 330 by passing through the first connecting part 110 and the second connecting part 120.
[0030] In some embodiments, the first connecting part 110 is provided with a first fixed pulley 111, the second connecting part 120 is provided with a second fixed pulley 121, the second rope section 320 is wound on the first fixed pulley 111 and the second fixed pulley 121, the first fixed pulley 111 and the second fixed pulley 121 can change the direction of the applied force, facilitate the transmission of force, pulling and lifting the bottom frame 200, and the first fixed pulley 111 and the second fixed pulley 121 can balance and distribute the force of the second rope section 320, so that the force can evenly distribute the force to each rope section, to achieve the effect of balance and stability, which is very important for the case of needing to evenly distribute the load or keep the structure stable, and the first fixed pulley 111 and the second fixed pulley 121 reduce the friction between the second rope section 320 and the first connecting part 110 and the second connecting part 120.
[0031] As the preferred embodiment of the utility model, the first rope section 310 and the second rope section 320 are provided with an unhooker 500, the unhooker 500 includes a fixed part, a hook part, an arm part and a locking pin, the hook part and the arm part are rotatably connected with the fixed part, the fixed part is provided with a lifting hole, the second rope section 320 is connected with the fixed part through the lifting hole, the first rope section 310 is connected with the hook part, the locking pin is detachably connected with the arm part and the hook part, after the locking pin is pulled out, the hook part and the arm part are separated, that is, the opening is opened, that is, the connecting line 300 is disconnected, and then the separation of the top frame 100 and the bottom frame 200 is realized, when the electronic bin of the adapter box needs to be recycled, at this time, the ROV operator can pull out the locking pin of the unhooker by operating the ROV manipulator, and then the connecting line 300 connected with the unhooker is loosened, so that the top frame 100 and the bottom frame 200 are separated; then the surface mother ship uses the winch to pull the input cable, and then the top frame 100 with the observation instrument 700 is recycled, the observation instrument 700 includes an electronic bin, a sensor and other components, it can be understood that the unhooker can also be selected as other structures, which can realize the disconnection of the connecting line 300, the unhooker can also facilitate the disconnection between the first rope section 310 and the second rope section 320, so that the first rope section 310 and the second rope section 320 are separated from each other, the unhooker can safely and efficiently release the connection to meet the operation requirement of separating the top frame 100 and the bottom frame 200.
[0032] Referring to Figure 2 , the second rope section 320 and the third rope section 330 are provided with a tensioner 600, the tensioner includes a first tensioning arm, a sleeve and a second tensioning arm connected in sequence, the first tensioning arm is connected with the bottom end of the second rope section 320, the top end of the second tensioning arm is connected with the top end of the second tensioning arm, the first tensioning arm and the second tensioning arm are respectively threadedly connected with the two ends of the sleeve, the tensioner can adjust the tightness of the connecting line 300, preferably, the connecting line 300 is a steel wire rope or other rigid or flexible material, so that the connection between the top frame 100 and the bottom frame 200 can be realized and the disconnection can be realized by cutting, and the tensioner 600 can tightly connect the second rope section 320 and the third rope section 330 together.
[0033] Preferably, the top end of the first tensioning arm is provided with a first lifting lug, the second rope section 320 is fixedly connected with the first tensioning arm through the first lifting lug, the bottom end of the first tensioning arm is provided with a first external thread, the top end of the sleeve is provided with a first internal thread matched with the first external thread, the bottom end of the second tensioning arm is provided with a second lifting lug, the third rope section 330 is fixedly connected with the second tensioning arm through the second lifting lug, the top end of the second tensioning arm is provided with a second external thread, the bottom end of the sleeve is provided with a second internal thread matched with the second external thread, and the spiral directions of the first internal thread and the second internal thread are opposite.
[0034] Referring to Figure 3 The top end of the top layer frame 100 is provided with a load bearing head 130, the top end of the load bearing head 130 is connected with an input cable 131, and the top of the input cable 131 is connected with a buoy.
[0035] In some embodiments, referring to Figure 2 The cross sections of the top layer frame 100 and the bottom layer frame 200 are both rectangular, and the bottom layer frame 200 is provided with limiting baffles 230 at the positions of the four corners, the limiting baffles 230 are located at the outer periphery of the top layer frame 100, can limit the horizontal displacement between the top layer frame 100 and the bottom layer frame 200, and ensure the overall structural stability of the docking box recycling structure.
[0036] It can be understood that the connecting line 300 can be provided with multiple, as the preferred embodiment of the utility model, the connecting line 300 is provided with 4, and the top layer frame 100 and the bottom layer frame 200 are stably connected.
[0037] The bottom layer frame 200 is provided with a counterweight, and the docking box recycling structure has various recycling modes, that is, the frame can be separated through the two modes of cutting steel wire rope and locking pin of pull-off hook, and the bottom layer frame 200 and the counterweight are discarded, so that the top layer frame 100 drives the observation instrument 700 to overcome the adsorption force in the underwater recycling process under the action of the buoy, and then the electronic cabin and the related instrument are recycled, the docking box recycling structure has the advantages that the docking box is not limited by the seabed topography, and even if the bottom layer frame 200 is settled, the structure can still realize the recycling of the docking box electronic cabin and the related instrument.
[0038] The existing docking box is recovered by the way of underwater hooking of a frogman or an underwater robot ROV, if the underwater docking box is settled, a great adsorption force will be borne in the recycling process, increasing the recycling difficulty and the requirement of the engineering ship capacity, and the docking box is released by the acoustic release carried by the docking box, but this way needs to make the recycling part in the positive buoyancy in the structural design stage, and the positive buoyancy design leads to the complex overall structure of the docking box, and the acoustic release is used, and the application of the acoustic release is suitable for the static scene of the underwater docking box, when the underwater docking box is in a dynamic pulling state, such as a buoy seabed base system, the acoustic release has the risk of false triggering in the dynamic stretching condition.
[0039] The utility model discloses a design need not to recover structure installation acoustic release, avoids acoustic release false trigger risk, and can select two ways to separate top frame 100 and bottom frame 200: (1) cut the connecting line 300, when ROV operator, operating ROV uses its carried hydraulic clamp to cut all connecting line 300, namely wire rope, makes top frame 100 and bottom frame 200 separate;Then the surface mother ship uses winch to pull input cable, and then makes top frame 100 drive observation instrument 700 (include electronic cabin, sensor) get recovery;(2) pull the locking pin of unhooker, when ROV operator, operating ROV manipulator pulls the locking pin of unhooker, and then makes the connecting line 300 connected with unhooker loose, makes the connection box top frame 100 and bottom frame 200 separate;Then the surface mother ship uses winch to pull input cable, and then makes top frame 100 drive observation instrument 700 (include electronic cabin, sensor) get recovery.
[0040] In the description of the present specification, the description referring to the terms "example", "embodiment" or "some embodiments" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.
[0041] Of course, the present application is not limited to the above-mentioned embodiments, and those skilled in the art can make equivalent modifications or replacements without departing from the spirit of the present application. These equivalent modifications or replacements are all included in the scope defined by the claims of the present application.
Claims
1. A junction box recovery structure, characterized by: It includes a top frame and a bottom frame that cooperate with each other, a space for holding observation instruments is formed between the top frame and the bottom frame, the top frame is used to connect observation instruments, a connecting line is provided between the top frame and the bottom frame, a first fixing part and a second fixing part are provided on the bottom frame, the first fixing part and the second fixing part are relatively arranged on both sides of the bottom frame, a first connecting part and a second connecting part are provided on the top frame, the first connecting part and the second connecting part are relatively arranged on both sides of the top frame, the first fixing part and the first connecting part correspond to and are located on one side of the top frame, the second fixing part and the second connecting part are correspondingly arranged and located on the other side of the top frame, one end of the connecting line is connected to the first fixing part, and the other end passes through the first connecting part and the second connecting part in sequence, and is connected to the second fixing part.
2. The junction box recycling structure according to claim 1, characterized in that: The longitudinal cross-section of the top frame is a trapezoid that is narrow at the top and wide at the bottom. The first connecting portion and the second connecting portion are respectively located at the top feet of the top frame, and the first fixing portion and the second fixing portion are respectively located on the bottom frame near the bottom corner of the top frame.
3. The junction box recycling structure according to claim 2, characterized in that: The first fixing part and the second fixing part both include a shackle, and the shackle includes a lifting ring and a locking rod. The bottom frame is provided with a mounting hole, and the locking rod passes through the mounting hole. Both ends of the locking rod are connected to the lifting ring, and both ends of the connecting line are connected to the first fixing part and the second fixing part through the lifting ring.
4. The junction box recycling structure according to claim 1, characterized in that: The connection line includes a first rope segment, a second rope segment, and a third rope segment connected in sequence, the bottom end of the first rope segment is connected to the first fixing portion, the bottom end of the third rope segment is connected to the second fixing portion, one end of the second rope segment is connected to the third rope segment, and the other end bypasses the first connecting portion and the second connecting portion to be connected to the third rope segment.
5. The junction box recycling structure according to claim 4, characterized in that: A first fixed pulley is provided on the first connecting portion, a second fixed pulley is provided on the second connecting portion, and the second rope segment is wound around the first fixed pulley and the second fixed pulley.
6. The junction box recycling structure according to claim 4, characterized in that: A dehooker is provided between the first rope segment and the second rope segment, and the dehooker includes a fixing portion, a hook portion, a stop arm portion and a locking pin. The hook portion and the stop arm portion are both rotatably connected to the fixing portion. A hanging hole is provided on the fixing portion, and the second rope segment is connected to the fixing portion through the hanging hole. The first rope segment is connected to the hook portion, and the locking pin enables the stop arm portion and the hook portion to be detachably connected.
7. The junction box recycling structure according to claim 4, characterized in that: A tensioner is provided between the second rope segment and the third rope segment, and the tensioner includes a first tensioning arm, a sleeve, and a second tensioning arm connected in sequence. The first tensioning arm is connected to the bottom end of the second rope segment, and the top end of the second tensioning arm is connected to the top end of the second tensioning arm. The first tensioning arm and the second tensioning arm are respectively threadedly connected to the two ends of the sleeve.
8. The junction box recycling structure according to claim 7, characterized in that: The top end of the first tensioning arm is provided with a first lifting ear, and the second rope segment is fixedly connected to the first tensioning arm through the first lifting ear, the bottom end of the first tensioning arm is provided with a first external thread, the top end of the sleeve is provided with a first internal thread matching the first external thread, the bottom end of the second tensioning arm is provided with a second lifting ear, and the third rope segment is fixedly connected to the second tensioning arm through the second lifting ear, the top end of the second tensioning arm is provided with a second external thread, and the bottom end of the sleeve is provided with a second internal thread matching the second external thread, and the spiral direction of the first internal thread is opposite to that of the second internal thread.
9. The junction box recycling structure according to claim 1, characterized in that: A bearing head is provided at the top of the top frame, an input cable is connected to the top of the bearing head, and a buoy is connected to the top of the input cable.
10. The junction box recycling structure according to claim 1, characterized in that: The cross sections of the top frame and the bottom frame are both rectangular. Position limiting baffles are provided at the four corners of the bottom frame. The position limiting baffles are located at the outer periphery of the top frame.