Mixed die head

Abstract

The utility model relates to the technical field of extrusion molding equipment, in particular to a mixed die head which comprises an upper die base and a lower die base, the upper die base is provided with a molding channel, the molding channel penetrates through the upper die base along the axis of the molding channel, the lower die base is connected to the end, in the axis direction of the molding channel, of the upper die base, and a communicating groove is formed in the end, close to the upper die base, of the lower die base. And the communicating groove is used for communicating with the forming channel, and a plurality of feeding channels are formed in the groove wall of the communicating groove and communicate with the outside. The extruder die head is divided into the upper die base and the lower die base, the upper die base is provided with the forming channel used for forming raw materials and sending out products, the lower die base is provided with the connecting groove, and the multiple feeding channels are arranged on the groove wall of the connecting groove, so that raw materials of different colors enter the communicating groove through the feeding channels to be mixed and then enter the forming channel to be formed; the production requirements of multi-color products are met, and the application range of the extruder is widened.

Description

Technical Field

[0001] This application relates to the technical field of extrusion molding equipment, and in particular to a hybrid die. Background Technology

[0002] The extruder die is used to shape the medium to be extruded into a fixed shape. The quality of the extruder die design directly affects the quality of the extruded product; therefore, the extruder die plays a crucial role in the entire extruder.

[0003] Currently, extruders use single-hole dies, meaning the feed inlet and outlet are connected. Products extruded using single-hole dies can only meet market demands for transparency or single-color products, such as white or yellow, and cannot produce two- or multi-color products. Furthermore, the overall die structure makes installation and disassembly difficult, and the overall machine design is not optimal. Utility Model Content

[0004] In order to enable the production of multi-color products and improve the applicability of extruders, this application provides a mixing die.

[0005] The hybrid die head provided in this application adopts the following technical solution:

[0006] A hybrid die head includes an upper die base and a lower die base. The upper die base is provided with a forming channel that extends through the upper die base along the axis of the forming channel. The lower die base is connected to one end of the upper die base along the axis of the forming channel. The lower die base is provided with a connecting groove at one end near the upper die base. The connecting groove is used to communicate with the forming channel. The groove wall is provided with a plurality of feeding channels that are connected to the outside.

[0007] By adopting the above technical solution, the extruder die head is divided into an upper die seat and a lower die seat. The upper die seat is provided with a forming channel for raw material forming and product delivery. The lower die seat is provided with a connecting groove. Several feeding channels are provided on the wall of the connecting groove, which facilitates the mixing of raw materials of different colors through the feeding channels into the connecting groove, and then into the forming channel for forming, thus meeting the needs of multi-color product production and improving the applicability of the extruder.

[0008] Preferably, the feeding channel includes a main feeding port and a side feeding port. The axis of the main feeding port is parallel to the axis of the forming channel, and the axis of the side feeding port is perpendicular to the axis of the main feeding port. There are a plurality of side feeding ports, which are distributed circumferentially around the connecting groove.

[0009] By adopting the above technical solution, the feeding channel includes a main feeding port and a side feeding port, which facilitates the installation of the extruder die head on an extruder that requires a large amount of raw materials for product production. The extruder feeds the raw materials into the connecting groove from the main feeding port, and other extruders feed raw materials of other colors into the connecting groove through the side feeding port, thereby meeting the needs of multi-color product production and improving equipment production efficiency.

[0010] Preferably, the lower mold base is provided with a first inner ring groove at one end near the upper mold base, the first inner ring groove is arranged around the connecting groove, and the side feed port is connected to the first inner ring groove.

[0011] By adopting the above technical solution and setting a first inner ring groove, the raw materials entering through the side feed port are evenly dispersed to various parts of the connecting groove through the first inner ring groove, thereby improving the mixing effect of multiple raw materials.

[0012] Preferably, the inner wall of the main feed inlet at the end away from the connecting groove is provided with a first chamfer.

[0013] By adopting the above technical solution, a first chamfer is provided on the inner wall of the end of the main feed port away from the connecting groove, which guides the raw material entering the main feed port and increases the flow rate of the raw material entering the connecting groove in the main feed port, making it easier for the raw material to enter the forming channel.

[0014] Preferably, the upper mold base is connected to a connecting column, the axis of the connecting column is parallel to the axis of the forming channel, and the lower mold base is rotatably connected to the connecting column, the axis of rotation of the lower mold base coincides with the axis of the connecting column.

[0015] By adopting the above technical solution, the upper and lower die holders are relatively fixed along the axis of the connecting column, reducing the possibility of loss of the upper or lower die holder and improving the service life of the extruder die head.

[0016] Preferably, it further includes a limiting post, which is slidably connected to the upper mold base. The sliding direction of the limiting post is parallel to the axial direction of the connecting post. The lower mold base is provided with a limiting hole for the limiting post to be inserted.

[0017] By adopting the above technical solution, the limiting post is embedded in the limiting hole, which reduces the possibility of relative rotation between the upper and lower die holders during installation or use, and improves the accuracy and reliability of the extruder die head.

[0018] Preferably, the upper mold base is provided with a sliding groove, and the limiting post is coaxially slidably embedded in the sliding groove, with both ends of the limiting post extending out of the sliding groove.

[0019] By adopting the above technical solution, the upper die base is provided with a sliding groove, and the limiting post is slidably embedded in the sliding groove. The sliding groove guides the sliding of the limiting post, making it easy for the limiting post to be embedded in the limiting groove. Both ends of the limiting post are extended out of the sliding groove, making it easy for the user to hold the end of the limiting post away from the lower die base, pull the limiting post away from the limiting hole, release the relative fixation between the upper die base and the lower die base, and improve the convenience of operating the extruder die head.

[0020] Preferably, it also includes a reset member, which is connected between the limiting post and the upper mold base, and the reset member causes the two ends of the limiting post to tend to extend out of the slide groove.

[0021] By adopting the above technical solution, when the limiting post is aligned with the limiting hole, the reset component drives the limiting post to embed into the limiting hole, reducing the possibility of the limiting post being dislodged from the limiting hole due to vibration and improving the reliability of the extruder die head.

[0022] Preferably, the outer periphery of the limiting post near the lower mold base is provided with a second chamfer, and the outer wall of the lower mold base near the upper mold base is provided with a third chamfer. The end of the second chamfer near the slide groove is located between the two ends of the third chamfer, and the third chamfer is used to abut against the second chamfer.

[0023] By adopting the above technical solution, the limiting post is provided with a second chamfer, and the lower die base is provided with a third chamfer. When the upper die base rotates, it drives the limiting post to rotate. The third chamfer is used to abut against the second chamfer, pushing the abutting post to overcome the elastic force of the reset member and embed into the slide groove. When the slide groove is directly opposite the limiting hole, the limiting post is embedded into the limiting hole under the action of the elastic force of the reset member. When the limiting post is embedded in the limiting hole, the outer wall of the limiting post is in contact with the wall of the limiting hole, and the third chamfer does not abut against the wall of the limiting hole. Therefore, the limiting post cannot be disengaged from the limiting hole by rotating the upper die base, which improves the convenience and reliability of the extruder die head operation.

[0024] In summary, this application includes at least one of the following beneficial technical effects:

[0025] 1. The extruder die head is divided into an upper die base and a lower die base. The upper die base is equipped with a forming channel for raw material forming and product delivery. The lower die base is equipped with a connecting groove. Several feeding channels are provided on the wall of the connecting groove, which facilitates the mixing of raw materials of different colors through the feeding channels into the connecting groove, and then into the forming channel for forming, thus meeting the needs of multi-color product production and improving the applicability of the extruder.

[0026] 2. The limiting post is embedded in the limiting hole, which reduces the possibility of relative rotation between the upper and lower die holders during installation or use, and improves the reliability of the extruder die head;

[0027] 3. When the limiting post is aligned with the limiting hole, the reset component drives the limiting post to embed into the limiting hole, reducing the possibility of the limiting post being dislodged from the limiting hole due to vibration and improving the reliability of the extruder die head. Attached Figure Description

[0028] Figure 1 This is a structural schematic diagram of Embodiment 1, mainly showing the state of the upper mold base and the lower mold base separated.

[0029] Figure 2 This is a cross-sectional view of Example 1.

[0030] Figure 3 This is a cross-sectional view of another embodiment.

[0031] Figure 4 This is a schematic diagram of the structure of the die head body, extruder body and extrusion mechanism in Example 1.

[0032] Figure 5 This is a partial sectional view of the die head body, extruder body, and extrusion mechanism in Example 1.

[0033] Figure 6 yes Figure 5 Enlarged view of point A in the middle.

[0034] Figure 7 This is a structural schematic diagram of Embodiment 2, mainly showing the state where the upper mold base and the lower mold base are separated.

[0035] Figure 8 This is a cross-sectional view of the die head body, extruder body, and extrusion mechanism in Example 2.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Die head body; 11. Upper die base; 111. Forming channel; 112. Slide groove; 113. Step groove; 114. Connecting rod; 115. Guide groove; 12. Lower die base; 121. Connecting groove; 122. Feeding channel; 1221. Main feed port; 1222. Side feed port; 123. First inner ring groove; 124. First chamfer; 125. Limiting hole; 126. Third chamfer; 127. First connecting channel; 128. Second connecting channel; 129. Outer ring groove; 1210. Rotating groove; 1211. Limiting groove; 1212. Second inner ring groove; 1213. Third connecting channel; 1214. Fourth connecting channel; 1215. Partition; 13. Connecting post; 131. Limiting ring; 14. Limiting post; 141. Second chamfer; 142. Guide ring; 15. Reset component;

[0038] 2. Extruder body;

[0039] 3. Extrusion mechanism; 31. Die head; 32. Connecting ring; 321. Mounting groove; 322. Positioning groove; 323. Discharge channel; 324. Discharge port; 33. Connecting pipe. Detailed Implementation

[0040] The present application will be further described in detail below with reference to the accompanying drawings.

[0041] This application discloses a hybrid mold head.

[0042] Example 1

[0043] Reference Figure 1 This application discloses a hybrid mold head including a mold head body 1, which includes a lower mold base 12. One end of the lower mold base 12 along its axial direction has a connecting groove 121, the axis of which coincides with the axis of the lower mold base 12. The lower mold base 12 near the connecting groove 121 has a first inner annular groove 123, which surrounds the connecting groove 121. The axis of the first inner annular groove 123 coincides with the axis of the connecting groove 121, and the depth of the first inner annular groove 123 is greater than the depth of the connecting groove 121. A first connecting channel 127 and a second connecting channel 128 are provided on the wall of the connecting groove 121, connecting the connecting groove 121 and the first inner annular groove 123. The inner walls of the first connecting channel 127 and the second connecting channel 128 near the bottom of the first inner annular groove 123 are flush with the bottom of the connecting groove 121. In this embodiment, there are two first connecting channels 127 and two second connecting channels 128. The two first connecting channels 127 and two second connecting channels 128 are symmetrically distributed along the direction perpendicular to the axis of the lower mold base 12. A second connecting channel 128 is provided between two adjacent first connecting channels 127, and a first connecting channel 127 is provided between two adjacent second connecting channels 128.

[0044] Reference Figure 1 and Figure 2 The lower mold base 12 has an outer ring groove 129 on its outer wall near the end of the connecting groove 121. The depth of the outer ring groove 129 is greater than the depth of the first inner ring groove 123. The upper mold base 11 has several feeding channels 122, which connect the connecting groove 121 to the outside. The feeding channels 122 include a main feeding port 1221 and a side feeding port 1222. The axis of the main feeding port 1221 coincides with the axis of the connecting groove 121. The inner wall of the main feeding port 1221 away from the connecting groove 121 has a first chamfer 124. The axis of the side feeding port 1222 is perpendicular to the axis of the main feeding port 1221. The side feeding port 1222 connects the first inner ring groove 123 and the outer ring groove 129. The inner wall of the side feeding port 1222 near the bottom of the outer ring groove 129 is flush with the bottom of the first inner ring groove 123. In this embodiment, there are two side feed ports 1222, and the inner walls on both sides of the side feed ports 1222 are parallel to the inner walls on both sides of the first connecting channel 127.

[0045] The die head body 1 also includes an upper die base 11 and a connecting post 13. The lower die base 12 is provided with a rotating groove 1210, which runs through the lower die base 12 along its axis. The axis of the rotating groove 1210 is parallel to the axis of the lower die base 12 and is coplanar with the axis of the lower die base 12. One end of the connecting post 13 is coaxially rotatably embedded in the rotating groove 1210, and the side wall of the connecting post 13 is in contact with the groove wall of the rotating groove 1210. A limiting groove 1211 is provided at one end of the rotating groove 1210 on the groove wall of the upper die base 11. A limiting ring 131 is fixedly connected to the outer periphery of the connecting post 13. The limiting ring 131 is embedded in the limiting groove 1211, and the side surface of the limiting ring 131 closest to the upper die base 11 is in contact with the bottom of the limiting groove 1211. The upper mold base 11 is fixedly connected to the connecting column 13, and the end of the upper mold base 11 near the lower mold base 12 is in contact with the end of the lower mold base 12 near the connecting groove 121. The outer wall of the upper mold base 11 is flush with the outer wall of the lower mold base 12. A stepped groove 113 is provided on the outer wall of the upper mold base 11 away from the lower mold base 12, and the end of the connecting column 13 away from the lower mold base 12 extends into the stepped groove 113.

[0046] The upper mold base 11 is provided with a forming channel 111, which extends through the upper mold base 11 along its axis. The axis of the forming channel 111 coincides with the axis of the upper mold base 11, and the forming channel 111 is used to connect with the connecting groove 121. In this embodiment, the forming channel 111 has a circular cross-section.

[0047] Reference Figure 3 In another embodiment, the forming channel 111 has a circular cross-section, and six connecting rods 114 are fixedly connected to the inner wall of the forming channel 111. The six connecting rods 114 are evenly distributed around the axis of the forming channel 111, and the surface of the connecting rod 114 near the lower mold base 12 is flush with the end of the upper mold base 11 near the lower mold base 12.

[0048] Reference Figure 2The mold head body 1 also includes a limiting post 14 and a reset member 15. The upper mold base 11 is provided with a sliding groove 112, which extends through the upper mold base 11 along its axis and is connected to a stepped groove 113. The axis of the sliding groove 112 is parallel to the axis of the upper mold base 11, and is coplanar with the axes of the upper mold base 11 and the connecting post 13. The limiting post 14 is coaxially slidably embedded in the sliding groove 112, with its sidewalls fitting against the groove wall of the sliding groove 112. Both ends of the limiting post 14 extend out of the sliding groove 112. The groove wall of the sliding groove 112 is coaxially provided with a guide groove 115. A guide ring 142 is fixedly connected to the sidewall of the limiting post 14, and the guide ring 142 is slidably embedded in the guide groove 115. The sliding direction of the guide ring 142 is parallel to the sliding direction of the limiting post 14. A limiting hole 125 is provided at one end of the lower mold base 12 near the connecting groove 121. The limiting hole 125 passes through the lower mold base 12 along its axis, and the axis of the limiting hole 125 is parallel to the axis of the lower mold base 12. The axis of the limiting hole 125 is coplanar with the axis of the lower mold base 12 and the axis of the rotating groove 1210. The limiting hole 125 is used for the insertion of the end of the limiting post 14 away from the stepped groove 113. A second chamfer 141 is provided on the outer periphery of the end of the limiting post 14 away from the stepped groove 113. A third chamfer 126 is provided on the groove wall of the outer ring groove 129 near one end of the upper mold base 11. The end of the second chamfer 141 near the slide groove 112 is located between the two ends of the third chamfer 126, and the third chamfer 126 is used to abut against the second chamfer 141. A reset member 15 is connected between the guide ring 142 and the upper mold base 11. The reset member 15 makes the two ends of the limiting post 14 tend to extend out of the slide groove 112. In this embodiment, the reset member 15 is a spring. The reset member 15 is sleeved on the outer periphery of the limiting post 14. One end of the reset member 15 is connected to the guide ring 142 near the side surface of the lower mold base 12, and the other end of the reset member 15 is connected to the guide groove 115 near the side wall of the lower mold base 12.

[0049] Reference Figure 4 and Figure 5 The hybrid die head also includes an extruder body 2 and an extrusion mechanism 3. Several extruder bodies 2 are provided, spaced apart horizontally. In this embodiment, two extruder bodies 2 are provided. The extrusion mechanism 3 includes a die head 31 and a connecting ring 32. The number of die heads 31 and connecting rings 32 is the same as the number of extruder bodies 2 and corresponds one-to-one. One end of the die head 31 is fixedly connected to one end of the extruder body 2, and the connecting ring 32 is fixedly connected to the end of the die head 31 away from the extruder body 2.

[0050] Reference Figure 5 and Figure 6The connecting ring 32 has a coaxial mounting groove 321 at one end near the head 31. The die head body 1 is embedded in the mounting groove 321 of any connecting ring 32. The lower die base 12, away from the upper die base 11, abuts against the end of the head 31 near the connecting ring 32. The outer walls of the lower die base 12 and the upper die base 11 are in contact with the groove wall of the mounting groove 321. The bottom of the mounting groove 321 has a positioning groove 322 for the insertion of the end of the connecting post 13 away from the lower die base 12. The end of the limiting post 14 away from the lower die base 12 abuts against the bottom of the mounting groove 321. In this embodiment, when the upper die base 11 and the lower die base 12 are embedded in the mounting groove 321, the end of the limiting post 14 away from the lower die base 12 is flush with the bottom of the stepped groove 113. The extrusion mechanism 3 also includes a connecting pipe 33, with both ends of the connecting pipe 33 fixedly connected to the side walls of two connecting rings 32. The connecting rings 32 are provided with a discharge channel 323, which connects the mounting groove 321 and the connecting pipe 33. The discharge channel 323 is directly opposite the outer ring groove 129. The bottom of the mounting groove 321 of the connecting ring 32, which is embedded with the die head body 1, is coaxially provided with a discharge port 324, which connects the forming channel 111 and the outside.

[0051] The implementation principle of Example 1 is as follows: Pull the limiting post 14 to disengage it from the limiting hole 125. Rotate the upper mold base 11 to separate it from the lower mold base 12, and clean the lower mold base 12 and the upper mold base 11. Rotate the upper mold base 11 to rotate the limiting post 14. The second chamfer 141 abuts against the third chamfer 126, pushing the limiting post 14 to overcome the elastic force of the reset member 15 and embed it into the slide groove 112. When the slide groove 112 is aligned with the limiting hole 125, the limiting post 14 is embedded into the limiting hole 125 under the action of the elastic force of the reset member 15, realizing the relative fixation of the upper mold base 11 and the lower mold base 12 along the circumference of the connecting post 13. Embed the upper mold base 11 and the lower mold base 12 into the mounting groove 321, so that the connecting post 13 is aligned with the positioning groove 322, and fix the connecting ring 32 to the machine head 31.

[0052] One extruder conveys molten raw material to the connecting groove through the main feed port 1221, while another extruder conveys molten raw material to the outer ring groove 129 through the connecting pipe 33, enters the first inner ring groove 123 through the side feed port 1222, then enters the connecting groove through the first connecting channel 127 and the second connecting channel 128, and then enters the molding channel 111 together. The resulting two-color mixed product is discharged from the discharge port 324.

[0053] Example 2

[0054] Reference Figure 7The difference between this embodiment and Embodiment 1 is that a second inner ring groove 1212 is provided at one end of the lower mold base 12 near the connecting groove 121. The second inner ring groove 1212 is located outside the first inner ring groove 123, and the axis of the second inner ring groove 1212 coincides with the axis of the first inner ring groove 123. The bottom of the second inner ring groove 1212 is flush with the bottom of the first inner ring groove 123. Two side feed ports 1222 are provided, each corresponding to one of the two first connecting channels 127. One side feed port 1222 is connected to the first inner ring groove 123, and the other side feed port 1222 is connected to the second inner ring groove 1212. A third connecting channel 1213 and a fourth connecting channel 1214 are provided on the inner wall of the second inner ring groove 1212. The inner wall of the third connecting channel 1213 and the fourth connecting channel 1214 near the bottom of the second inner ring groove 1212 is flush with the bottom of the connecting groove 121. A third connecting channel 1213 is provided, corresponding to a side feed port 1222 that connects to the second inner ring groove 1212. The number of fourth connecting channels 1214 is the same as the number of second connecting channels 128, and they correspond one-to-one. A spacer 1215 is fixedly connected to the wall of the outer ring groove 129. The length direction of the spacer 1215 is parallel to the axis of the lower mold base 12. One end of the spacer 1215 along its length direction is fixedly connected to the bottom of the outer ring groove 129, and the other end of the spacer 1215 is flush with the end of the lower mold base 12 near the upper mold base 11. The surface of the spacer ring away from the wall of the outer ring groove 129 is flush with the outer wall of the lower mold base 12. Two spacers 1215 are provided, symmetrically distributed along an axis perpendicular to the side feed port 1222.

[0055] There are three extruder bodies 2, which are evenly distributed in the horizontal direction. There are two connecting pipes 33, and one connecting pipe 33 is provided between two adjacent connecting rings 32. The die head body 1 is embedded in the mounting groove 321 of the connecting ring 32 located in the middle.

[0056] The implementation principle of Example 2 is as follows: One extruder conveys molten raw material to the connecting groove through the main feed port 1221. The other two extruders convey molten raw material to the outer ring groove 129 through the connecting pipe 33. One extruder enters the first inner ring groove 123 through the side feed port 1222, and then enters the connecting groove through the first connecting channel 127 and the second connecting channel 128. The other extruder enters the second inner ring groove 1212 through the side feed port 1222, and then enters the first inner ring groove 123 through the third connecting channel 1213 and the fourth connecting channel 1214. Then it enters the connecting groove through the first connecting channel 127 and the second connecting channel 128, and then enters the molding channel 111 together. The generated three-color mixed product is sent out from the discharge port 324.

[0057] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A hybrid die head, characterized in that: The device includes an upper mold base (11) and a lower mold base (12); the upper mold base (11) is provided with a forming channel (111); the forming channel (111) passes through the upper mold base (11) along the axis of the forming channel (111); the lower mold base (12) is connected to one end of the upper mold base (11) along the axis of the forming channel (111); the lower mold base (12) is provided with a connecting groove (121) at one end near the upper mold base (11); the connecting groove (121) is used to communicate with the forming channel (111); a plurality of feeding channels (122) are provided on the wall of the connecting groove (121); the feeding channels (122) are connected to the outside.

2. The mixing die head according to claim 1, characterized in that: The feeding channel (122) includes a main feeding port (1221) and a side feeding port (1222); the axis of the main feeding port (1221) is parallel to the axis of the forming channel (111); the axis of the side feeding port (1222) is perpendicular to the axis of the main feeding port (1221); there are a plurality of side feeding ports (1222); the plurality of side feeding ports (1222) are distributed circumferentially around the connecting groove (121).

3. The mixing die head according to claim 2, characterized in that: The lower mold base (12) is provided with a first inner ring groove (123) at one end near the upper mold base (11); the first inner ring groove (123) is arranged around the connecting groove (121); the side feed port (1222) is connected to the first inner ring groove (123).

4. The mixing die head according to claim 2, characterized in that: The main feed inlet (1221) has a first chamfer (124) on the inner wall at the end away from the connecting groove (121).

5. The mixing die head according to claim 1, characterized in that: The upper mold base (11) is connected to a connecting column (13); the axis of the connecting column (13) is parallel to the axis of the forming channel (111); the lower mold base (12) is rotatably connected to the connecting column (13); the rotation axis of the lower mold base (12) coincides with the axis of the connecting column (13).

6. The mixing die head according to claim 5, characterized in that: It also includes a limiting post (14); the limiting post (14) is slidably connected to the upper mold base (11); the sliding direction of the limiting post (14) is parallel to the axial direction of the connecting post (13); the lower mold base (12) is provided with a limiting hole (125); the limiting hole (125) is used for the limiting post (14) to be inserted.

7. The mixing die head according to claim 6, characterized in that: The upper mold base (11) is provided with a slide groove (112); the limiting post (14) is coaxially slidably embedded in the slide groove (112); the two ends of the limiting post (14) extend out of the slide groove (112).

8. The mixing die head according to claim 7, characterized in that: It also includes a reset member (15); the reset member (15) is connected between the limiting post (14) and the upper mold base (11); the reset member (15) causes the two ends of the limiting post (14) to tend to extend out of the slide groove (112).

9. The mixing die head according to claim 8, characterized in that: The limiting post (14) has a second chamfer (141) on its outer periphery near the lower mold base (12); the lower mold base (12) has a third chamfer (126) on its outer wall near the upper mold base (11); the end of the second chamfer (141) near the slide groove (112) is located between the two ends of the third chamfer (126); the third chamfer (126) is used to abut against the second chamfer (141).

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