An ultralow-temperature inner-cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen

Abstract

This invention belongs to the field of CNC machine tool functional component design technology, and discloses an ultra-low temperature internally cooled tool post-turning tool system that can realize directional switching and delivery of liquid nitrogen. It mainly consists of an ultra-low temperature medium internally sprayed tool post, a quick-change liquid nitrogen internally cooled square shank turning tool, and a quick-change liquid nitrogen internally cooled round shank turning tool. Through the designed ultra-low temperature medium internally sprayed tool post, an internal spray cooling method is achieved, delivering the ultra-low temperature medium to the tool tip via the flow channel of the ultra-low temperature internally cooled tool post-turning tool system. This overcomes the ultra-low temperature sealing and heat insulation technology within the tool post and at the connection between the tool post and the tool, and solves the integration problem of the liquid nitrogen internal spray cooling function with the lathe tool post, square shank turning tool, and round shank turning tool structure. By designing an axially displaceable liquid nitrogen transmission pipeline, directional supply and switching of the ultra-low temperature medium to the working tool is achieved during automatic tool changing. The liquid nitrogen internally cooled tool features a separate tool head and tool holder design, ensuring reliable liquid nitrogen delivery while simplifying the tedious process of re-setting the tool after each tool change.

Description

Technical Field

[0001] This invention belongs to the field of CNC machine tool functional component design technology, and relates to an ultra-low temperature internal cooling tool post-turning tool system that can realize directional switching and delivery of liquid nitrogen. Background Technology

[0002] To meet the high performance requirements of advanced equipment in aerospace, nuclear engineering, and other fields, high-temperature alloys and uranium-based alloys are the preferred materials for key components such as shafts, discs, and cylinders due to their superior properties. However, under conventional cooling conditions, insufficient cooling efficiency is a common problem when turning parts made of these materials, leading to severe tool wear, easy material combustion, and deterioration of machining quality. An internal spray cooling method, which delivers cryogenic media such as liquid nitrogen to the tool tip through a special flow channel between the tool holder and the cutting tool, provides precise and intense cooling to the cutting area. This significantly reduces cutting temperature, extends tool life, suppresses cutting combustion, and improves part surface quality. Furthermore, the liquid nitrogen internally cooled turning tool features a separate tool head and tool holder design, requiring only the replacement of the tool head with a new insert each time, greatly shortening preparation time. Therefore, achieving cryogenic internal spray cooling of tools and rapid insert replacement in turning is of great significance for the high-quality, efficient, and safe machining of key components in critical fields.

[0003] Clearly, the cryogenic internal cooling tool turret-tool system capable of directional liquid nitrogen switching is one of the core functional components for cryogenically cooled turning of difficult-to-machine materials. However, effectively integrating the cryogenic medium internal spray cooling function with the tool turret structure while ensuring that conventional functions are not affected is extremely challenging. For example, how to integrate the cryogenic medium transmission channel into the compact tool turret structure and ensure its good thermal insulation and sealing performance; how to ensure that the cryogenic cooling medium is still supplied directionally to the working tool during automatic tool change; and how to simultaneously achieve the cryogenic medium internal spray cooling function and the rapid insert change function. Therefore, a reasonable design of the cryogenic internal cooling lathe tool turret-tool system capable of directional liquid nitrogen switching is essential.

[0004] Currently, several structural forms have been invented by domestic and foreign institutions for the design of cryogenic internal spray cooling tool holders and turning tools. In 2012, MAG Industrial Automation Systems Co., Ltd. disclosed "a tool turret for machining workpieces and a machining system having such a tool turret" in invention patent 201280006086.8. This design incorporates a cryogenic medium delivery pipeline inside the side of the turret, and also machines a delivery channel inside the turning tool and its mounting base to provide cryogenic medium to the working turning tool. However, the turning tools compatible with this machining system lack a quick-change insert function. In 2024, Dalian University of Technology disclosed "a cryogenic medium internal spray cooling CNC lathe via turret-turning tool" in invention patent 202411613330.8. This design features an axial transmission channel inside the turret and a transmission distribution block on the top of the tool head for delivering cryogenic medium to the working tool. However, the cryogenic medium transmission channel being located inside the turret places high demands on sealing performance; if leakage occurs, the moving structure of the turret will freeze and malfunction. Summary of the Invention

[0005] This invention addresses the shortcomings or improvement needs of existing technologies by proposing an ultra-low temperature internally cooled tool holder-turning tool system that enables directional switching and delivery of liquid nitrogen. It overcomes challenges such as the thermal insulation transmission of ultra-low temperature medium within the confined space of the tool holder, the directional supply of ultra-low temperature cooling medium to the working turning tool during automatic tool changing in a servo turret, and the integration of ultra-low temperature cooling and rapid insert changing functions.

[0006] The technical solution of the present invention: A cryogenic internally cooled tool post-turning tool system capable of directional switching and conveying of liquid nitrogen mainly consists of a cryogenic medium internally sprayed tool post, a quick-change liquid nitrogen internally cooled square shank turning tool, and a quick-change liquid nitrogen internally cooled round shank turning tool. The tool head 1 of the cryogenic medium internally sprayed tool post has two types of axially penetrating transmission channels evenly distributed around its circumference: a first type of transmission channel 2 and a second type of transmission channel 3. The first type of transmission channel 2 is adapted to the quick-change liquid nitrogen internally cooled square shank turning tool, and the second type of transmission channel 3 is adapted to the quick-change liquid nitrogen internally cooled round shank turning tool. The number and circumferential arrangement of the two types of axially penetrating transmission channels are determined by the type of tool to be installed at each tool position on the tool head 1 of the cryogenic medium internally sprayed tool post.

[0007] Assembly of the cryogenic medium internal spray type cutter holder: The first cryogenic sealing ring 4 and the second cryogenic sealing ring 5 are respectively embedded in the first mounting groove 7 and the second mounting groove 8 of the guide block 6; the third cryogenic sealing ring 9 is pushed into the first inner cavity 10 of the guide block 6 and fixed with the first retaining spring 11; Installation method of the first type of heat insulation sleeve 12: The first type of heat insulation sleeve 12 is installed on the tail end 13 of one guide block 6, and the first type of heat insulation sleeve 12 is pushed into the first type of transmission channel 2. This guide block 6 is fixed to the mounting surface 14 of the cutter disc 1 of the cryogenic medium internal spray type cutter holder; Installation method of the second type of heat insulation sleeve 15: The second type of heat insulation sleeve 15 is installed on the tail end 13 of another guide block 6, and the second type of heat insulation sleeve 15 is pushed into the second type of transmission channel 3. This guide block 6 is fixed to the mounting surface 14 of the cutter disc 1 of the cryogenic medium internal spray type cutter holder. The linear bearing housing 16 is mounted on the brake mechanism mounting surface 18 of the turret housing 17; the linear bearing 19 is pushed into the second inner cavity 20 of the linear bearing housing 16 and fixed by two second retaining rings 21; the vacuum transmission pipe 22 is pushed into the third inner cavity 23 of the linear bearing 19, one end of the vacuum transmission pipe 22 is fitted with a pressure block 24, and the other end is connected to the brake cylinder piston rod 26 through a floating joint 25; the brake cylinder body 28 is fixed to the brake mechanism mounting surface 18 of the turret housing 17 by two cylinder brackets 27; the sheet metal housing 29 is mounted on the brake mechanism mounting surface 18 of the turret housing 17 to prevent machining chips and powder from splashing into the floating joint 25; the first copper joint 30 is connected to the vacuum transmission pipe 22 for connection with the transmission pipe of the cryogenic medium.

[0008] Assembly of the quick-change liquid nitrogen internally cooled square shank turning tool: The fourth cryogenic sealing ring 31 is pushed into the fourth inner cavity 33 of the square shank turning tool shank ...

[0009] Assembly of the quick-change liquid nitrogen internally cooled round shank turning tool: The fifth cryogenic sealing ring 37 is pushed into the fifth inner cavity 39 of the round shank turning tool shank 38; the second mounting shank of the round shank turning tool head 40 is pushed into the fifth inner cavity 39 of the round shank turning tool shank 38 and locked with the second locking bolt 42; the liquid nitrogen transmission hose 43 is connected to the liquid nitrogen inlet 45 on the round shank turning tool shank 38 through the second copper connector 44.

[0010] When the quick-change liquid nitrogen internally cooled square shank turning tool is connected to the cryogenic medium internally sprayed tool holder, the sixth cryogenic sealing ring 46 is installed into the third mounting groove 47 of the tool disc 1 of the cryogenic medium internally sprayed tool holder; the injection channel 48 of the square shank turning tool rod 32 is coaxially aligned with the first type of heat insulation sleeve 12, and the square shank turning tool rod 32 is pushed into the tool position groove 49 of the tool disc 1 until the square shank turning tool rod 32 presses against the sixth cryogenic sealing ring 46; the wedge-shaped pressure block 50 is pressed into the tool position groove 49 of the tool disc 1 and fixed with the first internal hex bolt 51.

[0011] When the quick-change liquid nitrogen internally cooled round shank turning tool is connected to the cryogenic medium internally sprayed tool holder, the round shank turning tool holder 52 is fixed to the tool disc 1 by bolt connection; the round shank turning tool bar 38 is pushed into the round shank turning tool holder 52 and fixed with the second internal hex bolt 53; the liquid nitrogen transmission hose 43 is connected to the second type of transmission channel 3 on the tool disc 1 through the third copper connector 54.

[0012] During machining, the cryogenic internal cooling tool holder-turning tool system, which enables directional switching and delivery of liquid nitrogen, flows in from the first copper connector 30, and sequentially passes through the vacuum transmission pipe inner channel 55 inside the vacuum transmission pipe 22, the first type of heat insulation sleeve inner channel 56 inside the first type of heat insulation sleeve 12, the square shank turning tool shank inner channel 57 inside the square shank turning tool shank 32, and the square shank turning tool head inner channel 58 inside the square shank turning tool head 34, and finally exits from the first jet port 59 at the front end of the square shank turning tool head 34, completing the cryogenic cooling machining.

[0013] When the cryogenic internal cooling tool holder-turning tool system, which enables directional switching and delivery of liquid nitrogen, automatically changes tools, the brake cylinder piston rod 26 drives the vacuum transmission pipe 22 to move axially away from the tool disc 1. The flow channel 55 inside the vacuum transmission pipe 22 is interrupted from the flow channel 56 inside the first type of heat insulation sleeve 12. After the tool disc 1 rotates a certain angle, the brake cylinder piston rod 26 drives the vacuum transmission pipe 22 to move axially closer to the tool disc 1. The flow channel 55 inside the vacuum transmission pipe 22 is connected to the flow channel 60 inside the second type of heat insulation sleeve 15. The cryogenic medium passes through the liquid nitrogen transmission hose 43, the flow channel 61 inside the round shank turning tool rod 38, and the flow channel 62 inside the round shank turning tool head 40, and finally exits from the second jet port 63 at the front end of the round shank turning tool head 40, completing the directional supply of cryogenic medium to the working tool for automatic tool changing.

[0014] When changing the insert of the quick-change liquid nitrogen internally cooled square shank turning tool, the first locking bolt 36 is removed, the square shank turning tool head 34 with the new insert is replaced, and then the first locking bolt 36 is tightened again. The method of changing the insert of the quick-change liquid nitrogen internally cooled round shank turning tool is the same as that of the quick-change liquid nitrogen internally cooled square shank turning tool.

[0015] The beneficial effects of this invention are as follows: This invention independently designs an internally sprayed cryogenic medium tool post, realizing an internal spray cooling method in which the cryogenic medium is transported to the tool tip through the flow channel of the cryogenic internally cooled tool post-tool. It overcomes the cryogenic sealing and heat insulation technology inside the tool post and at the connection between the tool post and the tool, and solves the integration problem of liquid nitrogen internal spray cooling function with the structure of lathe tool post, square shank turning tool, and round shank turning tool. By designing an axially displaceable liquid nitrogen transmission pipeline, it realizes the directional supply and switching of cryogenic medium to the working turning tool during automatic tool changing. The liquid nitrogen internally cooled tool is designed with a separate tool head and tool holder, which ensures reliable liquid nitrogen transmission while simplifying the tedious step of resetting the tool after each tool change. Attached Figure Description

[0016] Figure 1 This is a structural diagram of the outer side of the cutter head of a cryogenic medium internal spray cutter holder. Figure 2 This is a structural diagram of the inner side of the cutter head of a cryogenic medium internal spray cutter holder. Figure 3 Axonometric view of the guide block; Figure 4 A cross-sectional isometric view of the guide block; Figure 5 This is a front view of a cryogenic medium internal spray-type tool holder. Figure 6 For cryogenic medium internal spray type tool holder in Figure 5 An enlarged view of the portion of the ellipse on the left side; Figure 7 For cryogenic medium internal spray type tool holder in Figure 5 An enlarged view of the portion within the circle shown, following section AA; Figure 8 For cryogenic medium internal spray type tool holder in Figure 5 An enlarged view of the portion of the ellipse on the right side; Figure 9 Axonometric drawing of a cryogenic medium internal spray tool holder; Figure 10 For cryogenic medium internal spray type tool holder in Figure 9 A magnified view of the part circled in the image; Figure 11 A schematic diagram of a quick-change liquid nitrogen internally cooled round shank turning tool. Figure 12 This is a schematic diagram of the structure of a square shank lathe tool head; Figure 13 This is a schematic diagram of the structure of a round shank lathe tool head; In the diagram: 1. Tool head; 2. First type of transmission channel; 3. Second type of transmission channel; 4. First cryogenic seal ring; 5. Second cryogenic seal ring; 6. Guide block; 7. First mounting groove; 8. Second mounting groove; 9. Third cryogenic seal ring; 10. First inner cavity; 11. First snap ring; 12. First type of heat insulation sleeve; 13. Tail end; 14. Mounting surface; 15. Second type of heat insulation sleeve; 16. Linear bearing seat; 17. Turret housing; 18. Braking mechanism mounting surface; 19. Linear bearing; 20. Second inner cavity; 21. Second snap ring; 22. Vacuum transmission pipe; 23. Third inner cavity; 24. Pressure block; 25. Floating joint; 26. Brake cylinder piston rod; 27. Cylinder bracket; 28. Brake cylinder body; 29. ​​Sheet metal housing; 30. First copper joint; 31. Fourth cryogenic seal ring; 32. Square shank turning tool holder; 33. Fourth inner cavity; 34. Square shank turning tool. 35 First mounting shank; 36 First locking bolt; 37 Fifth cryogenic sealing ring; 38 Round shank cutting tool holder; 39 Fifth inner cavity; 40 Round shank cutting tool head; 41 Second mounting shank; 42 Second locking bolt; 43 Liquid nitrogen transfer hose; 44 Second copper connector; 45 Liquid nitrogen inlet; 46 Sixth cryogenic sealing ring; 47 Third mounting groove; 48 Injection channel; 49 Tool position groove; 50 Wedge-shaped pressure block; 51 First internal hex bolt; 52 Round shank cutting tool holder; 53 Second internal hex bolt; 54 Third copper connector; 55 Vacuum transfer pipe inner channel; 56 First type of heat insulation sleeve inner channel; 57 Square shank cutting tool holder inner channel; 58 Square shank cutting tool head inner channel; 59 First jet port; 60 Second type of heat insulation sleeve inner channel; 61 Round shank cutting tool holder inner channel; 62 Round shank cutting tool head inner channel; 63 Second jet port. Detailed Implementation

[0017] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings and technical solutions.

[0018] In this embodiment, the cryogenic medium is liquid nitrogen, with a minimum temperature of -196℃; the center height of the cryogenic medium internal spray-type tool holder is 1100mm, the number of tools is 12T, the time for changing and locking adjacent tools is 0.6s, the time for changing and locking the furthest tool is 1.6s, and the repeatability is 0.003mm; the diameter of the vacuum transmission pipe 1.14 is 25mm, and its thermal conductivity is approximately 0; the liquid nitrogen transmission hose 3.5 is made of modified polytetrafluoroethylene, with a thermal conductivity of less than 0.15W / (m·K).

[0019] The assembly process of the cryogenic internal cooling tool post-turning tool system, which enables directional switching and delivery of liquid nitrogen, is as follows: (See attached image) Figure 1-13As shown, in the first step, the first cryogenic sealing ring 4 and the second cryogenic sealing ring 5 are respectively embedded into the first mounting groove 7 and the second mounting groove 8 of the guide block 6. The third cryogenic sealing ring 9 is pushed into the first inner cavity 10 of the guide block 6 and fixed with the first retaining spring 11. The installation method of the first type of heat insulation sleeve 12 is as follows: the first type of heat insulation sleeve 12 is installed at the tail end 13 of one guide block 6, and the first type of heat insulation sleeve 12 is pushed into the first type of transmission channel 2. This guide block 6 is fixed to the mounting surface 14 of the cutter head 1 of the cryogenic medium internal spray cutter holder. The installation method of the second type of heat insulation sleeve 15 is as follows: the second type of heat insulation sleeve 15 is installed at the tail end 13 of another guide block 6, and the second type of heat insulation sleeve 15 is pushed into the second type of transmission channel 3. This guide block 6 is fixed to the mounting surface 14 of the cutter head 1 of the cryogenic medium internal spray cutter holder. Linear bearing seat 16 The brake mechanism mounting surface 18 is installed on the turret housing 17; the linear bearing 19 is pushed into the second inner cavity 20 of the linear bearing seat 16 and fixed by two second snap rings 21; the vacuum transmission pipe 22 is pushed into the third inner cavity 23 of the linear bearing 19, one end of the vacuum transmission pipe 22 is fitted with a pressure block 24, and the other end is connected to the brake cylinder piston rod 26 through a floating joint 25; the brake cylinder body 28 is fixed to the brake mechanism mounting surface 18 on the turret housing 17 by two cylinder brackets 27; the sheet metal housing 29 is installed on the brake mechanism mounting surface 18 on the turret housing 17 to prevent machining chips and powder from splashing into the floating joint 25; the first copper joint 30 is connected to the vacuum transmission pipe 22 for connection to the transmission pipe of the cryogenic medium; thus, the assembly of the cryogenic medium internal spray type tool holder is completed; The second step is to push the fourth cryogenic sealing ring 31 into the fourth inner cavity 33 of the square shank turning tool holder 32; push the first mounting shank 34 of the square shank turning tool head 34 into the fourth inner cavity 33 of the square shank turning tool holder 32 and lock it with the first locking bolt 36; thus, the assembly of the quick-change liquid nitrogen internally cooled square shank turning tool is completed. The third step is to push the fifth cryogenic sealing ring 37 into the fifth inner cavity 39 of the round shank turning tool holder 38; push the second mounting shank of the round shank turning tool head 40 into the fifth inner cavity 39 of the round shank turning tool holder 38 and lock it with the second locking bolt 42; the liquid nitrogen transfer hose 43 is connected to the liquid nitrogen inlet 45 on the round shank turning tool holder 38 through the second copper connector 44; at this point, the assembly of the quick-change liquid nitrogen internally cooled round shank turning tool is completed. Fourth step: Install the sixth cryogenic sealing ring 46 into the third mounting groove 47 of the cutter head 1 of the cryogenic medium internal spray tool holder; align the injection channel 48 of the square shank turning tool shank 32 coaxially with the first type of heat insulation sleeve 12, push the square shank turning tool shank 32 into the tool position groove 49 of the cutter head 1 until the square shank turning tool shank 32 presses against the sixth cryogenic sealing ring 46; press the wedge-shaped pressure block 50 into the tool position groove 49 of the cutter head 1 and fix it with the first internal hex bolt 51; at this point, the connection between the quick-change liquid nitrogen internally cooled square shank turning tool and the cryogenic medium internal spray tool holder is completed; Fifth step, fix the round shank turning tool holder 52 to the tool head 1 by bolt connection; push the round shank turning tool shank 38 into the round shank turning tool holder 52 and fix it with the second internal hex bolt 53; connect the liquid nitrogen transmission hose 43 to the second type of transmission channel 3 on the tool head 1 through the third copper connector 54; at this point, the connection between the quick-change liquid nitrogen internally cooled round shank turning tool and the cryogenic medium internal spray tool holder is completed. During machining, the cryogenic internal cooling tool holder-tool system, which enables directional switching and delivery of liquid nitrogen, flows in from the first copper joint 30 and sequentially passes through the vacuum transmission pipe 22, the first type of heat insulation sleeve 12, the square shank tool holder 32, the square shank tool head 34, and the square shank tool head 34, and finally exits from the first jet port 59 at the front end of the square shank tool head 34, thus completing the cryogenic cooling machining. When the cryogenic internal cooling tool holder-turning tool system, which enables directional switching and delivery of liquid nitrogen, automatically changes tools, the brake cylinder piston rod 26 drives the vacuum transmission pipe 22 to move axially away from the tool disc 1. The flow channel 55 inside the vacuum transmission pipe 22 is interrupted from the flow channel 56 inside the first type of heat insulation sleeve 12. After the tool disc 1 rotates a certain angle, the brake cylinder piston rod 26 drives the vacuum transmission pipe 22 to move axially closer to the tool disc 1. The flow channel 55 inside the vacuum transmission pipe 22 is connected to the flow channel 60 inside the second type of heat insulation sleeve 15. The cryogenic medium passes through the liquid nitrogen transmission hose 43, the flow channel 61 inside the round shank turning tool rod 38, and the flow channel 62 inside the round shank turning tool head 40, and finally exits from the second jet port 63 at the front end of the round shank turning tool head 40, completing the directional supply of cryogenic medium to the working tool for automatic tool changing. When changing the insert of the quick-change liquid nitrogen internally cooled square shank turning tool, the first locking bolt 36 is removed, the square shank turning tool head 34 with the new insert is replaced, and then the first locking bolt 36 is tightened again. The method of changing the insert of the quick-change liquid nitrogen internally cooled round shank turning tool is the same as that of the quick-change liquid nitrogen internally cooled square shank turning tool.

[0020] This invention employs a cooling approach where cryogenic medium is delivered to the tool tip via a special flow channel between the tool holder and the cutting tool, achieving highly efficient, point-to-point cooling of the cutting area during turning. The design of the cryogenic medium-in-the-place tool holder ensures directional delivery of the cryogenic medium to the cutting tool and integrates with automatic tool changing functionality. The use of quick-change liquid nitrogen internally cooled tools simplifies the tool changing process and improves machining efficiency. Core functional components for high-end cryogenic machining machine tools are designed to facilitate the implementation of cryogenic cooling turning of special alloys.

[0021] Obviously, the embodiments described above are only some, not all, of the embodiments in this application. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort should fall within the scope of protection of this application. In summary, the content of this specification should not be construed as a limitation of this application.

Claims

1. An ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen, characterized in that, The cryogenic internally cooled tool post-turning tool system that enables directional switching and conveying of liquid nitrogen mainly consists of a cryogenic medium internally sprayed tool post, a quick-change liquid nitrogen internally cooled square shank turning tool, and a quick-change liquid nitrogen internally cooled round shank turning tool. The tool head (1) of the cryogenic medium internally sprayed tool post has two types of axially penetrating transmission channels evenly distributed on its circumference. The two types of axially penetrating transmission channels are the first type of transmission channel (2) and the second type of transmission channel (3). The first type of transmission channel (2) is adapted to the quick-change liquid nitrogen internally cooled square shank turning tool, and the second type of transmission channel (3) is adapted to the quick-change liquid nitrogen internally cooled round shank turning tool. The number and circumferential arrangement order of the two types of axially penetrating transmission channels are determined by the type of tool to be installed at each tool position on the tool head (1) of the cryogenic medium internally sprayed tool post. Assembly of the cryogenic medium internal spray type cutter holder: The first cryogenic sealing ring (4) and the second cryogenic sealing ring (5) are respectively embedded in the first mounting groove (7) and the second mounting groove (8) of the guide block (6), and the third cryogenic sealing ring (9) is pushed into the first inner cavity (10) of the guide block (6) and fixed with the first snap ring (11); Installation method of the first type of heat insulation sleeve (12): The first type of heat insulation sleeve (12) is installed at the tail end (13) of one guide block (6), the first type of heat insulation sleeve (12) is pushed into the first type of transmission channel (2), and this guide block (6) is fixed to the mounting surface (14) of the cutter head (1) of the cryogenic medium internal spray type cutter holder; Installation method of the second type of heat insulation sleeve (15): The second type of heat insulation sleeve (15) is installed at the tail end (13) of another guide block (6), the second type of heat insulation sleeve (15) is pushed into the second type of transmission channel (3), and this guide block (6) is fixed to the cutter head (1) of the cryogenic medium internal spray type cutter holder. Mounting surface (14); linear bearing housing (16) is mounted on the brake mechanism mounting surface (18) on the turret housing (17); linear bearing (19) is pushed into the second inner cavity (20) of linear bearing housing (16) and fixed by two second snap rings (21); vacuum transmission pipe (22) is pushed into the third inner cavity (23) of linear bearing (19), one end of vacuum transmission pipe (22) is fitted with a pressure block (24), and the other end is connected to the piston rod (26) of brake cylinder through a floating joint (25); the cylinder body (28) of brake cylinder is fixed on the brake mechanism mounting surface (18) on the turret housing (17) through two cylinder brackets (27); sheet metal housing (29) is mounted on the brake mechanism mounting surface (18) on the turret housing (17) to prevent machining chips and powder from splashing into the floating joint (25); first copper joint (30) is connected to vacuum transmission pipe (22) for connection with the transmission pipe of cryogenic medium; Assembly of the quick-change liquid nitrogen internally cooled square shank turning tool: The fourth cryogenic sealing ring (31) is pushed into the fourth inner cavity (33) of the square shank turning tool shank (32); the first mounting shank (35) of the square shank turning tool head (34) is pushed into the fourth inner cavity (33) of the square shank turning tool shank (32) and locked with the first locking bolt (36); Assembly of the quick-change liquid nitrogen internally cooled round shank turning tool: The fifth cryogenic sealing ring (37) is pushed into the fifth inner cavity (39) of the round shank turning tool shank (38); the second mounting shank of the round shank turning tool head (40) is pushed into the fifth inner cavity (39) of the round shank turning tool shank (38) and locked with the second locking bolt (42); the liquid nitrogen transmission hose (43) is connected to the liquid nitrogen inlet (45) on the round shank turning tool shank (38) through the second copper connector (44).

2. The ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen according to claim 1, characterized in that, When the quick-change liquid nitrogen internally cooled square shank turning tool is connected to the cryogenic medium internal spray tool holder, the sixth cryogenic sealing ring (46) is installed in the third mounting groove (47) of the tool disc (1) of the cryogenic medium internal spray tool holder; the injection channel (48) of the square shank turning tool rod (32) is coaxially aligned with the first type of heat insulation sleeve (12), and the square shank turning tool rod (32) is pushed into the tool position groove (49) of the tool disc (1) until the square shank turning tool rod (32) presses the sixth cryogenic sealing ring (46); the wedge-shaped pressure block (50) is pressed into the tool position groove (49) of the tool disc (1) and fixed with the first internal hex bolt (51).

3. The ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen according to claim 1, characterized in that, When the quick-change liquid nitrogen internally cooled round shank turning tool is connected to the cryogenic medium internal spraying tool holder, the round shank turning tool holder (52) is fixed to the tool disc (1) by bolt connection; the round shank turning tool bar (38) is pushed into the round shank turning tool holder (52) and fixed with the second internal hex bolt (53); the liquid nitrogen transmission hose (43) is connected to the second type of transmission channel (3) on the tool disc (1) through the third copper connector (54).

4. The ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen according to claim 1, characterized in that, During machining, the cryogenic internal cooling tool holder-turning tool system that enables directional switching and delivery of liquid nitrogen flows in from the first copper connector (30), and sequentially passes through the vacuum transmission pipe inner channel (55) inside the vacuum transmission pipe (22), the first type of heat insulation sleeve inner channel (56) inside the first type of heat insulation sleeve (12), the square shank turning tool holder inner channel (57) inside the square shank turning tool holder (32), and the square shank turning tool head inner channel (58) inside the square shank turning tool head (34), and finally exits from the first jet port (59) at the front end of the square shank turning tool head (34) to complete the cryogenic cooling machining.

5. The ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen according to claim 1, characterized in that, When the cryogenic internally cooled tool holder-tool system capable of directional switching and delivery of liquid nitrogen automatically changes tools, the brake cylinder piston rod (26) drives the vacuum transmission pipe (22) to move axially away from the tool disc (1), and the flow channel (55) inside the vacuum transmission pipe (22) is interrupted from the flow channel (56) inside the first type of heat insulation sleeve (12); after the tool disc (1) rotates a certain angle, the brake cylinder piston rod (26) drives the vacuum transmission pipe (22) to move closer to the tool disc (1). As the axis moves, the inner flow channel (55) of the vacuum transmission pipe (22) is connected to the inner flow channel (60) of the second type of heat insulation sleeve (15); the cryogenic medium is ejected from the second jet port (63) at the front end of the round shank turning tool (40) through the liquid nitrogen transmission hose (43), the inner flow channel (61) of the round shank turning tool (38), and the inner flow channel (62) of the round shank turning tool (40), thus completing the directional supply of cryogenic medium to the working tool for automatic tool changing.

6. The ultra-low temperature inner cooling tool rest-tool bit system capable of realizing directional switching delivery of liquid nitrogen according to claim 1, characterized in that, When changing the insert of the quick-change liquid nitrogen internally cooled square shank turning tool, the first locking bolt (36) is removed, the square shank turning tool head (34) with the new insert is replaced, and then the first locking bolt (36) is tightened again. The method of changing the insert of the quick-change liquid nitrogen internally cooled round shank turning tool is the same as that of changing the insert of the quick-change liquid nitrogen internally cooled square shank turning tool.

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