Cooling, blanking and vibrating device of single-screw extruder

Abstract

The invention relates to the technical field of single-screw extruders, in particular to a single-screw extruder cooling, discharging and vibrating device which comprises a base frame structure, a hopper structure, an anti-blocking discharging structure and an auxiliary cooling structure, a stepping motor drives a connecting cylinder, a round rod and a threaded rod to rotate, air enters the connecting cylinder and the round rod through the interior of a sleeve, and the air enters the connecting cylinder and the round rod; a lower inclined pipe blows air to a lower inner shell, an upper inclined pipe blows air to an upper inner shell, so that the lower inner shell and the upper inner shell generate tiny vibration, a vertical plate, the interior of a base shell and the inner side of an anchoring plate are slidably mounted and placed, a stud is in threaded assembly arrangement with the interior of the vertical plate and the interior of the anchoring plate, and the stud is in threaded assembly arrangement with the interior of a ring frame and the interior of a mounting ring. By means of the arrangement, the device body can conveniently conduct vibration treatment on the inner shell of the hopper structure and is used for improving the accumulation anti-blocking effect on plastic granules, the device body can conveniently assemble and combine the hopper structure, and the hopper structure is easy to replace and maintain.

Description

Technical Field

[0001] The present invention relates to the technical field of single-screw extruders, and specifically to a cooling and discharging vibration device for a single-screw extruder. Background Art

[0002] Single-screw extruders are mainly used for extruding thermoplastic plastics such as polyvinyl chloride and polyethylene, and can process various plastic products, such as pipe extrusion, pressing plates, etc. Single-screw extruders usually have a hopper structure for stacking and discharging plastic pellets. Take the cooling and discharging vibration device of a single-screw extruder as an example.

[0003] For some cooling and discharging vibration devices of single-screw extruders, the effect of the device main body vibrating the inner shell of the hopper structure is poor, resulting in a poor anti-blocking effect on the stacking of plastic pellets. Moreover, the device main body is not convenient for assembling and combining the hopper structure, and it is not easy to replace and maintain the hopper structure. Therefore, a cooling and discharging vibration device for a single-screw extruder is proposed to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a cooling and discharging vibration device for a single-screw extruder, which is used to solve the problems that for some cooling and discharging vibration devices of single-screw extruders, the effect of the device main body vibrating the inner shell of the hopper structure is poor, resulting in a poor anti-blocking effect on the stacking of plastic pellets, and the device main body is not convenient for assembling and combining the hopper structure, and it is not easy to replace and maintain the hopper structure.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A cooling and feeding vibration device for a single-screw extruder, comprising a base frame structure, a hopper structure, an anti-blocking feeding structure and an auxiliary cooling structure. The hopper structure is arranged on the top of the base frame structure, the anti-blocking feeding structure is arranged inside the hopper structure, and the auxiliary cooling structure is arranged on the left side of the base frame structure. The base frame structure includes a base shell, a silica gel ring and an anchoring plate. The bottom end of the base shell and the bottom end of the anchoring plate are fixedly arranged on the top of the main box of the single-screw extruder. The silica gel ring is fixedly arranged on the inner wall of the base shell. The hopper structure includes a shell, a lower inner shell, an upper inner shell, a vertical plate and a ring frame. The lower inner shell and the upper inner shell are fixedly arranged on the inner wall of the shell. The vertical plate is fixedly arranged on the outer side of the shell, and the ring frame is fixedly arranged on the top end of the shell. The anti-blocking feeding structure includes a mounting ring, a connecting plate, a frustum, a lower cushion plate, a sleeve, an upper cushion plate, a stepping motor, a connecting cylinder, a round rod, an air pump device, a cylinder shell, an upper inclined pipe, a lower inclined pipe, a threaded rod, a limiting rod, a chuck, a connecting rod, a cylinder block and a blocking block. The connecting plate is fixedly arranged inside the mounting ring, the frustum is fixedly arranged inside the connecting plate, the lower cushion plate and the air pump device are fixedly arranged on the top end of the frustum. The sleeve is fixedly arranged on the top end of the lower cushion plate, and the right end of the sleeve is fixedly communicated with the exhaust pipe of the air pump device. The upper cushion plate is fixedly arranged on the top end of the sleeve, the stepping motor is fixedly arranged on the top end of the upper cushion plate, the connecting cylinder is fixedly arranged at the end of the main shaft of the stepping motor, the round rod is fixedly arranged at the bottom end of the connecting cylinder, and the outer side of the round rod is rotatably arranged with a rubber ring arranged inside the frustum. The cylinder shell is fixedly arranged at the bottom end of the frustum, six upper inclined pipes and six lower inclined pipes are symmetrically distributed and fixedly arranged on the outer side of the cylinder shell. The threaded rod is fixedly arranged at the bottom end of the round rod, the limiting rod is fixedly arranged inside the cylinder shell, the chuck is arranged on the outer sides of the threaded rod and the limiting rod, the connecting rod is fixedly arranged at the bottom end of the chuck, the cylinder block is fixedly arranged at the bottom end of the connecting rod, and the blocking block is fixedly arranged at the bottom end of the cylinder block.

[0007] Preferably, the auxiliary cooling structure includes a heat conduction ring, a square pipe and a ring cylinder. The inside of the heat conduction ring is fixedly arranged on the outer side of the pipe body of the single-screw extruder. The ring cylinder is arranged on the outer side of the heat conduction ring, the square pipe is fixedly arranged inside the ring cylinder, and the square pipe is fixedly arranged with the heat conduction ring. Through holes are arranged inside the heat conduction ring. The front-end square pipe is communicated with the water supply pipe of the external cooling water circulation pipeline system, and the rear-end square pipe is communicated with the water return pipe of the external cooling water circulation pipeline system.

[0008] Preferably, the vertical plate is slidably installed inside the base shell and the inner side of the anchoring plate, the silica gel ring is in close contact with the shell, and the vertical plate and the anchoring plate are threadedly assembled through external studs.

[0009] Preferably, the ring frame and the mounting ring are threadedly assembled through external studs.

[0010] Preferably, a through hole is formed inside the connecting cylinder, the inside of the connecting cylinder is communicated with the inside of the round rod, and a slot hole is formed below the round rod.

[0011] Preferably, a plurality of through holes are arranged at intervals inside the chuck, the inside of the chuck is slidably arranged with the limiting rod, and the inside of the chuck is rotationally threaded with the threaded rod.

[0012] Preferably, the rubber ring arranged inside the bottom end of the cylinder shell is slidably arranged with the outside of the cylinder block, and the rubber ring arranged outside the plug block is in close contact with the inner wall of the lower inner shell.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. In the present invention, the stepping motor drives the connecting cylinder, the round rod and the threaded rod to rotate, the rubber ring arranged outside the plug block is separated from the inner wall of the lower inner shell, the air pump device is started, air enters the inside of the connecting cylinder and the round rod through the inside of the sleeve, the air passes through the slot hole arranged below the round rod and enters the inside of the cylinder shell, the lower inclined pipe blows air to the lower inner shell, and the upper inclined pipe blows air to the upper inner shell, so that the lower inner shell and the upper inner shell generate slight vibrations, promoting the discharging of the plastic pellets. Through the above settings, the device body can conveniently vibrate the inner shell of the hopper structure to improve the anti-blocking effect of the accumulation of plastic pellets;

[0015] 2. In the present invention, the vertical plate is slidably installed inside the base shell and the inner side of the anchoring plate, the shell is in close contact with the silica gel ring, the inside of the vertical plate and the inside of the anchoring plate are threadedly assembled through an external stud, the inside of the ring frame and the inside of the mounting ring are threadedly assembled through an external stud, and the rubber ring arranged outside the plug block is in close contact with the inner wall of the lower inner shell. Through the above settings, the device body can conveniently assemble and combine the hopper structure and is easy to replace and maintain the hopper structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0017] Figure 2 is a schematic diagram of the cross-sectional structure of the mounting ring and the frustum of the present invention;

[0018] Figure 3 is the present invention Figure 2 is an enlarged schematic diagram of part A of the present invention;

[0019] Figure 4 is the present invention Figure 2 is an enlarged schematic diagram of part B of the present invention;

[0020] Figure 5 is a schematic diagram of the cross-section of some components of the anti-blocking discharging structure of the present invention;

[0021] Figure 6 For the present invention Figure 5 Schematic enlarged view of the structure at position C of the present invention;

[0022] Figure 7 For the present invention Figure 5 Schematic enlarged view of the structure at position D of the present invention;

[0023] Figure 8 Schematic installation view of the auxiliary cooling structure of the present invention;

[0024] Figure 9 For the present invention Figure 8 Schematic enlarged view of the structure at position E of the present invention.

[0025] In the figure: 1. Base frame structure; 11. Base shell; 12. Silicone rubber ring; 13. Anchor plate; 2. Hopper structure; 21. Shell; 22. Lower inner shell; 23. Upper inner shell; 24. Vertical plate; 25. Ring frame; 3. Anti-blocking blanking structure; 301. Installation ring; 302. Connecting plate; 303. Frustum; 304. Lower cushion plate; 305. Sleeve; 306. Upper cushion plate; 307. Stepper motor; 308. Connecting cylinder; 309. Round rod; 310. Air pump device; 311. Cylinder shell; 312. Upper inclined pipe; 313. Lower inclined pipe; 314. Threaded rod; 315. Limiting rod; 316. Chuck; 317. Connecting rod; 318. Cylinder block; 319. Blocking block; 4. Auxiliary cooling structure; 41. Heat conduction ring; 42. Square pipe; 43. Ring cylinder. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] In the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the position or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Similarly, words such as "a", "an" or "the" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "comprising" or "including" mean that the element or item appearing before the word covers the element or item listed after the word and its equivalents, without excluding other elements or items.

[0028] In addition, in the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected" and "coupled" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Please refer to Figures 1-9 , the present invention provides a technical solution:

[0030] A cooling and discharging vibration device for a single-screw extruder, comprising a base frame structure 1, a hopper structure 2, an anti-blocking discharging structure 3 and an auxiliary cooling structure 4. A hopper structure 2 is arranged on the top of the base frame structure 1. An anti-blocking discharging structure 3 is arranged inside the hopper structure 2. An auxiliary cooling structure 4 is arranged on the left side of the base frame structure 1. The base frame structure 1 includes a base shell 11, a silica gel ring 12 and an anchor plate 13. The bottom end of the base shell 11 and the bottom end of the anchor plate 13 are fixedly arranged on the top of the main box of the single-screw extruder. A silica gel ring 12 is fixedly arranged on the inner wall of the base shell 11. The hopper structure 2 includes a shell 21, a lower inner shell 22, an upper inner shell 23, a vertical plate 24 and a ring frame 25. A lower inner shell 22 and an upper inner shell 23 are fixedly arranged on the inner wall of the shell 21. A vertical plate 24 is fixedly arranged on the outer side of the shell 21. A ring frame 25 is fixedly arranged on the top end of the shell 21. The anti-blocking discharging structure 3 includes a mounting ring 301, a connecting plate 302, a frustum 303, a lower cushion plate 304, a sleeve 305, an upper cushion plate 306, a stepping motor 307, a connecting cylinder 308, a round rod 309, an air pump device 310, a cylinder shell 311, an upper inclined pipe 312, a lower inclined pipe 313, a threaded rod 314, a limiting rod 315, a chuck 316, a connecting rod 317, a cylinder block 318 and a blocking block 319. A connecting plate 302 is fixedly arranged inside the mounting ring 301. A frustum 303 is fixedly arranged inside the connecting plate 302. A lower cushion plate 304 and an air pump device 310 are fixedly arranged on the top end of the frustum 303. A sleeve 305 is fixedly arranged on the top end of the lower cushion plate 304. The right end of the sleeve 305 is fixedly communicated with the exhaust pipe of the air pump device 310. An upper cushion plate 306 is fixedly arranged on the top end of the sleeve 305. A stepping motor 307 is fixedly arranged on the top end of the upper cushion plate 306. A connecting cylinder 308 is fixedly arranged at the end of the main shaft of the stepping motor 307. A round rod 309 is fixedly arranged at the bottom end of the connecting cylinder 308. The outer side of the round rod 309 is rotatably arranged with a rubber ring arranged inside the frustum 303. A cylinder shell 311 is fixedly arranged at the bottom end of the frustum 303. Six upper inclined pipes 312 and six lower inclined pipes 313 are symmetrically distributed and fixedly arranged on the outer side of the cylinder shell 311. A threaded rod 314 is fixedly arranged at the bottom end of the round rod 309. The bottom end of the limiting rod 315 is fixedly arranged inside the cylinder shell 311. A chuck 316 is arranged on the outer sides of the threaded rod 314 and the limiting rod 315. A connecting rod 317 is fixedly arranged at the bottom end of the chuck 316. A cylinder block 318 is fixedly arranged at the bottom end of the connecting rod 317. A blocking block 319 is fixedly arranged at the bottom end of the cylinder block 318.

[0031] The auxiliary cooling structure 4 includes a heat-conducting ring 41, a square pipe 42, and a ring cylinder 43. The inside of the heat-conducting ring 41 is fixedly arranged on the outside of the single-screw extruder pipe body. A ring cylinder 43 is arranged on the outside of the heat-conducting ring 41. A square pipe 42 is fixedly arranged inside the ring cylinder 43. The square pipe 42 is fixedly arranged with the heat-conducting ring 41. A through hole is arranged inside the heat-conducting ring 41. The square pipe 42 arranged at the front end is communicated with the water delivery pipe of the external cooling water circulation pipeline system, and the square pipe 42 arranged at the rear end is communicated with the water return pipe of the external cooling water circulation pipeline system. Through the above settings, the auxiliary cooling structure 4 plays a role in cooling the outside of the single-screw extruder pipe body.

[0032] The vertical plate 24 is slidably installed inside the base shell 11 and on the inner side of the anchoring plate 13. The silica gel ring 12 is in close contact with the shell 21. The inside of the vertical plate 24 and the inside of the anchoring plate 13 are threadedly assembled through an external stud. Through the above settings, it is convenient to assemble and combine the base frame structure 1 and the hopper structure 2.

[0033] The inside of the ring frame 25 and the inside of the mounting ring 301 are threadedly assembled through an external stud. Through the above settings, it is convenient to assemble and combine the hopper structure 2 and the anti-blocking blanking structure 3.

[0034] A through hole is provided inside the connecting cylinder 308. The inside of the connecting cylinder 308 is communicated with the inside of the round rod 309. A slot is provided below the round rod 309. Through the above settings, air enters the inside of the connecting cylinder 308 and the round rod 309 through the inside of the sleeve 305, and the air passes through the slot provided below the round rod 309 and the inside of the cylinder shell 311.

[0035] A number of through holes are arranged at intervals inside the chuck 316. The inside of the chuck 316 is slidably arranged with the limiting rod 315. The inside of the chuck 316 is threadedly rotated with the threaded rod 314. Through the above settings, when the stepping motor 307 is started, it drives the connecting cylinder 308, the round rod 309, and the threaded rod 314 to rotate, so that the chuck 316 is vertically moved.

[0036] The rubber ring arranged inside the bottom end of the cylinder shell 311 is slidably arranged on the outside of the cylinder block 318. The rubber ring arranged on the outside of the blocking block 319 is in close contact with the inner wall of the lower inner shell 22. Through the above settings, the cylinder shell 311 plays a role in vertically limiting the cylinder block 318, and the blocking block 319 plays a role in blocking and discharging the plastic pellets.

[0037] Working process: The present invention provides a single-screw extruder cooling and blanking vibration device. The device body is convenient for vibrating the inner shell of the hopper structure 2, which is used to improve the anti-blocking effect of the accumulation of plastic pellets. And the device body is convenient for assembling and combining the hopper structure 2, and is easy to replace and maintain the hopper structure 2.

[0038] The stepper motor 307 and the air pump device 310 provided inside the device are controlled by an external PLC controller, and the stepper motor 307 and the air pump device 310 provided above are electrically connected to an external power supply.

[0039] First, assemble the base frame structure 1 and the hopper structure 2. The vertical plate 24 is slidably installed inside the base shell 11 and the inner side of the anchor plate 13. The shell 21 is in close contact with the silicone rubber ring 12. Threaded assembly is set inside the vertical plate 24 and the anchor plate 13 through external studs. Threaded assembly is set inside the ring frame 25 and the mounting ring 301 through external studs. The rubber ring provided on the outer side of the plug 319 is in close contact with the inner wall of the lower inner shell 22.

[0040] Plastic pellets are placed through the gap between the mounting ring 301 and the frustum 303. When it is necessary to conduct blanking treatment on the plastic pellets, the stepper motor 307 drives the connecting cylinder 308, the round rod 309, and the threaded rod 314 to rotate. The threaded rod 314 rotates in the internal thread of the chuck 316, causing the chuck 316, the connecting rod 317, the cylinder block 318, and the plug 319 to move upward. The rubber ring provided on the outer side of the plug 319 is separated from the inner wall of the lower inner shell 22. The air pump device 310 is started. The suction pipe provided at the front end of the air pump device 310 inhales air. The exhaust pipe provided at the left end of the air pump device 310 discharges air. The air enters the connecting cylinder 308 and the round rod 309 through the inside of the sleeve 305. The air passes through the slot holes provided below the round rod 309 and enters the inside of the cylinder shell 311. The air is communicated with the inside of the upper inclined pipe 312 and the lower inclined pipe 313 through the inside of the cylinder shell 311. The lower inclined pipe 313 blows air to the lower inner shell 22, and the upper inclined pipe 312 blows air to the upper inner shell 23, causing the lower inner shell 22 and the upper inner shell 23 to generate slight vibrations, promoting the discharging treatment of the plastic pellets, and improving the anti-blocking effect of the accumulation of the plastic pellets.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A cooling and feeding vibration device for a single-screw extruder, comprising a base frame structure (1), a hopper structure (2), an anti-blocking feeding structure (3) and an auxiliary cooling structure (4), characterized in that: A hopper structure (2) is provided at the top of the base frame structure (1). An anti-blocking blanking structure (3) is provided inside the hopper structure (2). An auxiliary cooling structure (4) is provided on the left side of the base frame structure (1). The base frame structure (1) includes a base shell (11), a silica gel ring (12), and an anchor plate (13). The bottom end of the base shell (11) and the bottom end of the anchor plate (13) are fixedly arranged on the top of the main box of the single-screw extruder. A silica gel ring (12) is fixedly arranged on the inner wall of the base shell (11). The hopper structure (2) includes a shell (21), a lower inner shell (22), an upper inner shell (23), a vertical plate (24), and a ring frame (25). A lower inner shell (22) and an upper inner shell (23) are fixedly arranged on the inner wall of the shell (21). A vertical plate (24) is fixedly arranged on the outside of the shell (21). A ring frame (25) is fixedly arranged at the top end of the shell (21). The anti-blocking blanking structure (3) includes a mounting ring (301), a connecting plate (302), a frustum (303), a lower cushion plate (304), a sleeve (305), an upper cushion plate (306), a stepping motor (307), a connecting cylinder (308), a round rod (309), an air pump device (310), a cylinder shell (311), an upper inclined pipe (312), a lower inclined pipe (313), a threaded rod (314), a limiting rod (315), a chuck (316), a connecting rod (317), a cylinder block (318), and a blocking block (319). A connecting plate (302) is fixedly arranged inside the mounting ring (301). A frustum (303) is fixedly arranged inside the connecting plate (302). A lower cushion plate (304) and an air pump device (310) are fixedly arranged at the top end of the frustum (303). A sleeve (305) is fixedly arranged at the top end of the lower cushion plate (304). The right end of the sleeve (305) is fixedly communicated with the exhaust pipe of the air pump device (310). An upper cushion plate (306) is fixedly arranged at the top end of the sleeve (305). A stepping motor (307) is fixedly arranged at the top end of the upper cushion plate (306). A connecting cylinder (308) is fixedly arranged at the end of the main shaft of the stepping motor (307). A round rod (309) is fixedly arranged at the bottom end of the connecting cylinder (308). The outside of the round rod (309) is rotatably arranged with a rubber ring arranged inside the frustum (303). A cylinder shell (311) is fixedly arranged at the bottom end of the frustum (303). Six upper inclined pipes (312) and six lower inclined pipes (313) are symmetrically distributed and fixedly arranged on the outside of the cylinder shell (311). A threaded rod (314) is fixedly arranged at the bottom end of the round rod (309). The bottom end of the limiting rod (315) is fixedly arranged inside the cylinder shell (311). A chuck (316) is arranged on the outside of the threaded rod (314) and the outside of the limiting rod (315). A connecting rod (317) is fixedly arranged at the bottom end of the chuck (316). A cylinder block (318) is fixedly arranged at the bottom end of the connecting rod (317). A blocking block (319) is fixedly arranged at the bottom end of the cylinder block (318).

2. The cooling and feeding vibration device of a single-screw extruder according to claim 1, wherein: The auxiliary cooling structure (4) includes a heat-conducting ring (41), a square pipe (42), and a ring cylinder (43). The inside of the heat-conducting ring (41) is fixedly arranged on the outside of the single-screw extruder pipe body. A ring cylinder (43) is arranged on the outside of the heat-conducting ring (41). A square pipe (42) is fixedly arranged inside the ring cylinder (43). The square pipe (42) is fixedly arranged with the heat-conducting ring (41). A through hole is arranged inside the heat-conducting ring (41). The square pipe (42) arranged at the front end is communicated with the water delivery pipe of the external cooling water circulation pipeline system. The square pipe (42) arranged at the rear end is communicated with the water return pipe of the external cooling water circulation pipeline system.

3. The cooling and feeding vibration device of a single-screw extruder according to claim 1, wherein: The vertical plate (24) is slidably installed inside the base shell (11) and on the inner side of the anchor plate (13). The silica gel ring (12) is in close contact with the shell (21). The inside of the vertical plate (24) and the inside of the anchor plate (13) are threadedly assembled through an external stud.

4. The cooling and feeding vibration device of a single-screw extruder according to claim 1, wherein: The inside of the ring frame (25) and the inside of the mounting ring (301) are threadedly assembled through an external stud.

5. The cooling and feeding vibration device of a single-screw extruder according to claim 1, wherein: A through hole is formed inside the connecting cylinder (308). The inside of the connecting cylinder (308) is communicated with the inside of the round rod (309). A slot hole is formed below the round rod (309).

6. The cooling and discharging vibration device of a single-screw extruder according to claim 1, characterized in that: A number of through holes are distributed at intervals inside the chuck (316). The inside of the chuck (316) is slidably arranged with the limiting rod (315). The inside of the chuck (316) is threadedly rotated with the threaded rod (314).

7. The cooling and feeding vibration device of a single-screw extruder according to claim 1, characterized in that: The rubber ring arranged inside the bottom end of the cylinder shell (311) is slidably arranged on the outside of the cylinder block (318). The rubber ring arranged on the outside of the plug block (319) is in close contact with the inner wall of the lower inner shell (22).

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