Cast pipe fitting polishing device

Abstract

The utility model discloses a casting pipe fitting polishing device, and relates to the technical field of pipe fitting machining. According to the technical key points, the device comprises a working platform, a mounting platform is placed on the working platform, a roller is arranged on the mounting platform, the surface of the roller is sleeved with polishing abrasive paper, and the two ends of a supporting main shaft penetrating through the center of the roller are connected with a first bearing seat and a second bearing seat respectively; a side rotating shaft is arranged over the second bearing seat, the two ends of the side rotating shaft are each sleeved with a third bearing seat, the two third bearing seats are installed on the end support, a grinding head is installed at one end of the side rotating shaft, and a power unit is installed at the other end of the side rotating shaft. And the side rotating shaft is connected with the supporting main shaft through a linkage unit. According to the polishing device, the polishing head and the polishing abrasive paper are integrated on the same equipment and are driven by the same power unit, so that during use, the convenience and the flexibility during operation of workers can be improved, and the cleanliness of a working area can be improved.

Description

Technical Field

[0001] This application relates to the field of pipe fitting processing technology, and in particular to a grinding device for cast pipe fittings. Background Technology

[0002] The casting process involves pouring molten metal into a mold, which then cools and solidifies to form the desired pipe fitting. Casting offers advantages such as high production efficiency and low cost, making it suitable for mass production. Grooved pipe fittings and malleable iron pipe fittings, commonly used at pipe joints, are frequently manufactured using this process. During casting, minor defects such as shrinkage cavities, porosity, and inclusions on the casting surface often require grinding to remove these defects, thereby improving product performance and quality. Furthermore, the casting process often results in roughness, unevenness, and roughness on both the inner and outer surfaces. This is due to the influence of thermal stress and shrinkage stress from the flow and solidification of the molten metal. Excessive surface roughness can lead to inaccurate product dimensions, unattractive appearance, and high fluid resistance, thus also requiring grinding.

[0003] When grinding cast iron pipe fittings such as grooved pipe fittings and malleable iron pipe fittings, which are typically used for pipe connections, multiple joints may be present on the fitting. While traditional grinding wheels can be used to grind the regular areas on the surface, the spaces between adjacent joints are usually narrow, requiring a hand drill with a smaller grinding head for specialized work. This necessitates frequent switching between two machines when grinding cast iron pipe fittings, which is inconvenient and involves numerous wiring connections, affecting the cleanliness of the work area. Utility Model Content

[0004] This application provides a grinding device for cast pipe fittings, which can improve the convenience of workers grinding cast pipe fittings and improve the cleanliness of the work area.

[0005] The above-mentioned objective of this application is achieved through the following technical solution:

[0006] A grinding device for cast pipe fittings includes a working platform, on which an installation platform is placed. A roller is arranged along the length of the installation platform, the axis of the roller is parallel to the plane of the installation platform, sandpaper is fitted on the surface of the roller, and a supporting spindle is fixedly connected through the center of the roller.

[0007] One end of the support spindle is fixedly mounted on a pad block via a first bearing seat, and the pad block is fixedly mounted on the mounting platform. The other end of the support spindle is fixedly mounted on an end bracket via a second bearing seat, and the end bracket is also fixedly mounted on the mounting platform.

[0008] A side rotating shaft is provided directly above the second bearing housing. A third bearing housing is respectively fitted at both ends of the side rotating shaft. Both third bearing housings are fixedly installed on the end bracket. A grinding head is installed at one end of the side rotating shaft, and a power unit is installed at the other end of the side rotating shaft.

[0009] The side rotation shaft and the support main shaft are connected by a linkage unit.

[0010] Furthermore, the power unit includes a first pulley connected to the end of the side rotating shaft away from the grinding head, a second pulley is provided on the lower side of the first pulley and the two are connected by a transmission belt, the center of the second pulley away from the end bracket is fixedly connected to the output end of the drive motor, and the housing of the drive motor is fixedly mounted on the mounting platform.

[0011] Furthermore, the linkage unit includes a worm gear, which is coaxially sleeved on the outside of the side rotating shaft and fixedly connected to it. A worm wheel meshes with the lower side of the worm gear, and the worm wheel is sleeved on the supporting main shaft between the end of the roller away from the first bearing seat and the second bearing seat, and the worm wheel is fixedly connected to the supporting main shaft.

[0012] Furthermore, a protective shell is installed on the outer side of the end bracket, which can protect the second bearing seat, the third bearing seat, the power unit, and the linkage unit on the end bracket.

[0013] Furthermore, a sliding adjustment component is installed on the lower side of the installation platform, which is used to adjust the position of the installation platform on the working platform.

[0014] Furthermore, the sliding adjustment assembly includes a connecting plate arranged parallel to the bottom of the work platform. One end of the connecting plate is inserted into a groove arranged along the axis of the roller below the work platform, and the other end of the connecting plate extends upward and is fixedly connected to the lower side of the mounting platform.

[0015] Furthermore, an adjusting bolt is inserted at the center of the connecting plate and the two are threaded together.

[0016] Furthermore, a dust cover is provided on the outside of the installation platform, and the dust cover is fixedly installed on the working platform.

[0017] Furthermore, the dust cover has a lighting lamp on the inner side of its top plate and a dust collection port connected to a vacuum cleaner in the factory on the inner side of its back plate.

[0018] In summary, this application includes at least one of the following beneficial technical effects:

[0019] In this application, one end of the side rotating shaft equipped with the grinding head is connected to the power unit. The side rotating shaft is located directly above the second bearing supporting the main shaft, and the side rotating shaft and the main shaft are connected by a linkage unit. When the power unit is started, it can drive the side rotating shaft and the main shaft to rotate synchronously. Abrasive paper is installed on the roller fixedly sleeved on the main shaft. In this way, the equipment of this application can achieve the effect of synchronous operation of the abrasive paper and the grinding head after the power unit is started. In contrast, in the prior art, the grinding wheel used for grinding large regular areas of pipe fittings and the grinding head used for grinding small areas are two separate devices. Compared with this, the grinding device of this application integrates the two devices into one device, which can significantly improve the convenience of operation for workers. In addition, since the grinding head and abrasive paper are driven by the same power unit, it can not only reduce the cost of the power module, but also reduce the number of external cables in the work area, thereby improving the cleanliness of the work area. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the overall structure of this application;

[0022] Figure 2 This is a bottom view of this application;

[0023] Figure 3 This is a partial structural diagram after the dust cover and protective shell of this application have been removed;

[0024] Figure 4 yes Figure 3 Enlarged structural diagram at point A;

[0025] Figure 5 This is a structural diagram of a common type of cast pipe fitting.

[0026] Reference numerals: 1. Working platform; 2. Mounting platform; 3. Roller; 4. Sandpaper; 5. Support spindle; 6. First bearing seat; 7. Pad; 8. Second bearing seat; 9. End bracket; 10. Side rotating shaft; 11. Third bearing seat; 12. Grinding head; 13. Power unit; 131. First pulley; 132. Second pulley; 133. Drive motor; 14. Linkage unit; 141. Worm gear; 142. Worm wheel; 15. Protective shell; 16. Adjustment assembly; 161. Connecting plate; 162. Slide groove; 17. Adjusting bolt; 18. Dust cover; 19. Lighting lamp; 20. Dust collection port. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0028] like Figures 1-4 As shown, this application discloses a grinding device for cast pipe fittings, including a working platform 1, an installation platform 2 placed on the working platform 1, a roller 3 arranged along the length of the installation platform 2, the axis of the roller 3 being parallel to the plane of the installation platform 2, sandpaper 4 being fitted on the surface of the roller 3, and a supporting spindle 5 passing through the center of the roller 3 and the two being fixedly connected.

[0029] One end of the supporting spindle 5 is fixedly mounted on the pad 7 via the first bearing seat 6. The pad 7 is fixedly mounted on the mounting platform 2. The other end of the supporting spindle 5 is fixedly mounted on the end bracket 9 via the second bearing seat 8. The end bracket 9 is also fixedly mounted on the mounting platform 2.

[0030] A side rotating shaft 10 is provided directly above the second bearing housing 8. A third bearing housing 11 is respectively fitted at both ends of the side rotating shaft 10. Both third bearing housings 11 are fixedly installed on the end bracket 9. A grinding head 12 is installed at one end of the side rotating shaft 10, and a power unit 13 is installed at the other end of the side rotating shaft 10.

[0031] The side rotation shaft 10 and the support main shaft 5 are connected by a linkage unit 14.

[0032] In the above embodiments, the roller 3 of this application has a cylindrical structure, which provides installation space for the sandpaper 4 through the supporting spindle 5. The sandpaper 4 can be fixedly sleeved on the outside of the roller 3 with double-sided tape during use. This not only ensures good stability of the sandpaper 4 during use but also makes it convenient to replace the sandpaper 4 later (the worker can simply find the joint of the sandpaper 4 on the roller 3 and peel it off). The two ends of the supporting spindle 5 are respectively inserted into the first bearing seat 6 and the second bearing seat 8. The first bearing seat 6 and the second bearing seat 8 are fixedly mounted on the mounting platform 2 through the pad 7 and the end bracket 9, respectively. This ensures that the first bearing seat 6 and the second bearing seat 8 provide sufficient support for the supporting spindle 5 while also ensuring smoother rotation of the supporting spindle 5. The side rotating shaft 10 located above the second bearing seat 8 is mounted on the end bracket 9 through two third bearing seats 11. Similarly, the two third bearing seats 11, through the end bracket 9, provide stable support for the side rotating shaft 10 while ensuring smoother rotation during operation.

[0033] The grinding head 12 mounted on one end of the side rotating shaft 10 of this application is much smaller in volume than the roller 3 (the volume of the roller is about 50 times that of the grinding head; for example, when the diameter of the roller in this application is 3.6 cm and the height is 12.5 cm, its volume is about 127 cubic centimeters, and the volume of the grinding head is about 2.5 cubic centimeters). In practice, the grinding head 12, also called a grinding head, is mainly used for removing burrs, internal grinding, and polishing on molds and other metal parts. Due to its small size, the grinding head 12 is much more flexible to use than a traditional grinding wheel, and can reach areas that a grinding wheel cannot reach. However, due to its small size, the processing speed of the grinding head 12 on metal parts is limited. Figure 5 As shown, grooved pipe fittings and malleable iron pipe fittings in cast pipes are commonly used as pipe connectors. These fittings have many protrusions. The common grinding method is to first use a grinding wheel to quickly process the large, regular area on the outside of the cast pipe fitting, and then a worker uses a hand drill equipped with a grinding head 12 to further process the internal and surface protrusions and internal spaces of these cast pipe fittings. Currently, the grinding wheel and the hand drill with the grinding head 12 are usually two separate devices, each with its own power module. Correspondingly, each device also has an external power cord for obtaining power. This not only causes the two cables to frequently tangle during use, but also affects the cleanliness of the work area. During the grinding process of cast pipe fittings, workers often need to switch between the two devices. For example, when a worker finishes grinding the cast pipe fitting with a grinding wheel and needs to use the hand drill with the grinding head 12, they need to move their body first, then pick up the hand drill, and then hold the hand drill in one hand and the cast pipe fitting in the other to grind. After grinding, they also need to turn off the hand drill and put it in the designated area, which is very cumbersome.

[0034] In this application, one end of the side rotating shaft 10, which is equipped with a grinding head 12, is connected to a power unit 13. The side rotating shaft 10 and the support main shaft 5 are connected by a linkage unit 14. When the power unit 13 is started, it can drive the side rotating shaft 10 and the support main shaft 5 to rotate synchronously. The roller 3 fixedly sleeved on the support main shaft 5 is equipped with sandpaper 4. In this way, after the power unit 13 is started, the equipment of this application can achieve the effect of synchronous operation of the sandpaper 4 and the grinding head 12. When grinding the cast pipe fittings, the worker only needs to move the cast pipe fittings to the sandpaper 4 or the grinding head 12 as needed for the corresponding grinding operation. Even when using the grinding head 12 for grinding, the cast pipe fittings can be held with both hands. Compared with the prior art, it can effectively improve the grinding accuracy and the stability of the casting grinding process. In addition, it can significantly improve the convenience of the worker's operation. Meanwhile, since the grinding head 12 and the sandpaper 4 are driven by the same power unit 13, not only can the cost of the power module be reduced, but also the number of external cables in the work area can be reduced, thereby improving the cleanliness of the work area.

[0035] In practical use, the side shaft 10 can be used to connect to the grinding head 12, and the end can be set to the same structure as the end chuck of the hand drill in the prior art. This makes it convenient for workers to quickly change the grinding head 12 on the side shaft 10 as needed.

[0036] Furthermore, such as Figure 3 and Figure 4 As shown, the power unit 13 includes a first pulley 131 connected to the side shaft 10 at the end away from the grinding head 12. A second pulley 132 is provided on the lower side of the first pulley 131 and the two are connected by a transmission belt. The center of the end of the second pulley 132 away from the end bracket 9 is fixedly connected to the output end of the drive motor 133. The housing of the drive motor 133 is fixedly mounted on the mounting platform 2.

[0037] In the above embodiments, when the drive motor 133 of this application is working, it can drive the first pulley 131 to rotate through the second pulley 132. The first pulley 131 is connected to one end of the side rotating shaft 10. In this way, when the drive motor 133 is working, it can stably drive the side rotating shaft 10 to rotate with the grinding head 12.

[0038] Furthermore, such as Figure 3 and Figure 4 As shown, the linkage unit 14 includes a worm gear 141, which is coaxially sleeved on the outside of the side rotating shaft 10 and the two are fixedly connected. A worm wheel 142 is meshed on the lower side of the worm gear 141. The worm wheel 142 is sleeved on the support main shaft 5 between the end of the roller 3 away from the first bearing seat 6 and the second bearing seat 8, and the worm wheel 142 is fixedly connected to the support main shaft 5.

[0039] In the above embodiments, when the drive motor 133 drives the side rotating shaft 10 to rotate, the worm gear 141 fixedly sleeved on the side rotating shaft 10 will rotate together with the side rotating shaft 10, and the worm wheel 142 sleeved on the support main shaft 5 in the above manner will mesh with the worm gear 141. Therefore, while the side rotating shaft 10 rotates, it will synchronously drive the support main shaft 5 to rotate together. In this application, a grinding head 12 is installed on the side rotating shaft 10, and a sanding paper 4 is fixedly sleeved on the roller 3 of the support main shaft 5. In this way, the drive motor 133 can achieve the effect of simultaneously driving the grinding head 12 and the sanding paper 4 to rotate, effectively improving the utilization efficiency of the power of the drive motor 133.

[0040] Furthermore, such as Figure 1 and Figure 2 As shown, a protective shell 15 is installed on the outside of the end bracket 9. The protective shell 15 can protect the second bearing seat 8, the third bearing seat 11, the power unit 13 and the linkage unit 14 on the end bracket 9.

[0041] In the above embodiments, some metal dust is inevitably generated during the grinding process. If this metal dust drifts into structural components such as the power unit 13 and the linkage unit 14, it may affect the stable operation of the equipment. Therefore, this application provides a protective shell 15 on the outside of the end bracket 9 to reduce the impact of metal dust on the various components on the end bracket 9. Since the drive motor 133 in the power unit 13 generates heat during operation, in order to ensure that the drive motor 133 continues to maintain a stable and efficient working state, ventilation openings can be provided on the back of the protective shell 15 and at the position corresponding to the drive motor 133.

[0042] Furthermore, such as Figure 2 As shown, a sliding adjustment component 16 is installed on the lower side of the installation platform 2. The sliding adjustment component 16 is used to adjust the position of the installation platform 2 on the work platform 1.

[0043] In the above embodiments, the sliding adjustment component 16 provided under the installation platform 2 in this application allows workers to adjust the position of the installation platform 2 on the work platform 1 as needed when grinding the cast pipe fittings, so that the grinding head 12 or sandpaper 4 is close to them.

[0044] Furthermore, such as Figure 2 As shown, the sliding adjustment assembly 16 includes a connecting plate 161 arranged parallel to the bottom of the working platform 1. One end of the connecting plate 161 is inserted into a slide groove 162 arranged along the axis of the roller 3 below the working platform 1, and the other end of the connecting plate 161 extends upward and is fixedly connected to the lower side of the mounting platform 2.

[0045] In the above embodiments, this application provides a groove 162 with a length greater than that of the mounting platform 2 along the axis of the roller 3 below the working platform 1. A connecting plate 161 is slidably connected to one end of this groove 162. The other end of the connecting plate 161 extends horizontally to the end of the working platform 1 near the grinding head 12, then bends upwards and continues to extend upwards until it is fixedly connected to the lower side of the mounting platform 2. Thus, the mounting platform 2, guided by the groove 162, can adjust its position horizontally on the working platform 1. When the worker begins to use the roller 3... When the sandpaper 4 is used to polish the regular areas of the cast pipe fitting, the mounting platform 2 can be moved so that the roller 3 faces the worker, allowing the worker to use the roller 3 to polish the cast pipe fitting in a more comfortable posture. When the worker needs to use the grinding head 12 to polish the inside of the cast pipe fitting or some irregular areas on it, the mounting platform 2 can be moved so that the grinding head 12 is closer to the worker, allowing the worker to use the grinding head 12 to polish the cast pipe fitting in a more comfortable posture. This saves the worker the trouble of getting up and moving the stool back and forth, making the polishing process more flexible and convenient. A handle can also be added to the front of the work platform 1 of this application, so that the worker can have a better position to exert force to drive the mounting platform 2.

[0046] Furthermore, such as Figure 1 and Figure 2 As shown, an adjusting bolt 17 is inserted at the center of the connecting plate 161 and the two are threaded together.

[0047] In the above embodiments, after the worker adjusts the position of the mounting platform 2 on the work platform 1, the position of the mounting platform 2 can be fixed by turning the adjusting bolt 17 on the connecting plate 161 to prevent the mounting platform 2 from accidentally shaking on the work platform 1 during the grinding process and affecting the grinding effect.

[0048] Furthermore, such as Figure 1 and Figure 2 As shown, a dust cover 18 is provided on the outside of the installation platform 2, and the dust cover 18 is fixedly installed on the work platform 1.

[0049] In the above embodiments, the dust cover 18 provided on the outside of the installation platform 2 is open only on the front side near the grinding head 12. This effectively blocks the spread of metal dust during the process of workers grinding cast pipes, thereby reducing the pollution of the surrounding environment by metal dust.

[0050] Furthermore, such as Figure 1 and Figure 2 As shown, the top plate of the dust cover 18 is equipped with a lighting lamp 19, and the back plate of the dust cover 18 is equipped with a dust collection port 20 connected to a vacuum cleaner in the factory.

[0051] In the above embodiments, when grinding cast pipe fittings, workers often need to observe some small areas of the cast pipe fittings in order to ensure the accuracy of grinding. The lighting lamp 19 installed on the top plate of the dust cover 18 in this application can increase the brightness of the light during grinding, so as to help workers clearly observe the cast pipe fittings.

[0052] If workers inhale metal dust during the grinding process, it will inevitably harm their health. Therefore, this application has installed a dust collection port 20 on the back panel of the dust cover 18. The outside of the dust collection port 20 is connected to a vacuum cleaner or other dust collection equipment in the factory. In this way, the metal dust generated during the grinding process can be sucked away in time, thereby improving the protection of workers' health.

[0053] The implementation principle of this embodiment is as follows: Before use, the worker first inspects the entire equipment to ensure that the equipment is in normal condition. Then, the cast pipe to be ground is prepared and the worker sits in front of the work platform 1. During use, the drive motor 133 is started, and the worker holds the cast pipe with both hands. First, the worker grinds the regular areas on the surface of the cast pipe on the sandpaper 4 on the roller 3. If the position of the sandpaper 4 is not comfortable, the worker can loosen the adjusting bolt 17 on the connecting plate 161, and then move the installation platform 2 along the work platform 1. After the position of the sandpaper 4 is adjusted, the adjusting bolt 17 is tightened again and the worker continues to grind the cast pipe using the sandpaper 4. Subsequently, when it is necessary to grind some irregular areas or inner surfaces on the cast pipe, the worker can loosen the adjusting bolt 17 again, move the installation platform 2 along the work platform 1, and after the grinding head 12 reaches a suitable position for operation, tighten the adjusting bolt 17 again, hold the cast pipe with both hands, and continue to grind the cast pipe using the grinding head 12. After the grinding work is completed, the workers turn off the power to the equipment and clean up the work site.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A grinding device for cast pipe fittings, comprising a working platform (1), characterized in that: An installation platform (2) is placed on the work platform (1). A roller (3) is arranged on the installation platform (2) along its length. The axis of the roller (3) is parallel to the plane of the installation platform (2). Sandpaper (4) is fitted on the surface of the roller (3). A supporting spindle (5) is passed through the center of the roller (3) and the two are fixedly connected. One end of the support spindle (5) is fixedly mounted on the pad (7) via the first bearing seat (6), and the pad (7) is fixedly mounted on the mounting platform (2). The other end of the support spindle (5) is fixedly mounted on the end bracket (9) via the second bearing seat (8), and the end bracket (9) is also fixedly mounted on the mounting platform (2). A side rotating shaft (10) is provided directly above the second bearing seat (8). A third bearing seat (11) is respectively fitted at both ends of the side rotating shaft (10). Both third bearing seats (11) are fixedly installed on the end bracket (9). A grinding head (12) is installed at one end of the side rotating shaft (10), and a power unit (13) is installed at the other end of the side rotating shaft (10). The side rotation shaft (10) and the support main shaft (5) are connected by a linkage unit (14).

2. The casting pipe grinding device according to claim 1, characterized in that: The power unit (13) includes a first pulley (131) connected to the side shaft (10) away from the grinding head (12). A second pulley (132) is provided on the lower side of the first pulley (131) and the two are connected by a transmission belt. The center of the second pulley (132) away from the end bracket (9) is fixedly connected to the output end of the drive motor (133). The housing of the drive motor (133) is fixedly installed on the mounting platform (2).

3. The casting pipe grinding device according to claim 2, characterized in that: The linkage unit (14) includes a worm gear (141), which is coaxially sleeved on the outside of the side rotating shaft (10) and the two are fixedly connected. A worm wheel (142) meshes with the lower side of the worm gear (141). The worm wheel (142) is sleeved on the support main shaft (5) between the end of the roller (3) away from the first bearing seat (6) and the second bearing seat (8), and the worm wheel (142) is fixedly connected to the support main shaft (5).

4. The casting pipe grinding device according to claim 1, characterized in that: A protective shell (15) is installed on the outside of the end bracket (9). The protective shell (15) can protect the second bearing seat (8), the third bearing seat (11), the power unit (13) and the linkage unit (14) on the end bracket (9).

5. The casting pipe grinding device according to any one of claims 1 to 4, characterized in that: A sliding adjustment component (16) is installed on the lower side of the installation platform (2), and the sliding adjustment component (16) is used to adjust the position of the installation platform (2) on the working platform (1).

6. The casting pipe grinding device according to claim 5, characterized in that: The sliding adjustment assembly (16) includes a connecting plate (161) arranged parallel to the working platform (1) below. One end of the connecting plate (161) is inserted into a slide groove (162) arranged below the working platform (1) along the axis of the roller (3), and the other end of the connecting plate (161) extends upward and is fixedly connected to the lower side of the mounting platform (2).

7. The casting pipe grinding device according to claim 6, characterized in that: An adjusting bolt (17) is inserted at the center of the connecting plate (161) and the two are threaded together.

8. The casting pipe grinding device according to any one of claims 1 to 4, characterized in that: A dust cover (18) is provided on the outside of the installation platform (2), and the dust cover (18) is fixedly installed on the working platform (1).

9. The grinding device for cast pipe fittings according to claim 8, characterized in that: The dust cover (18) has a lighting lamp (19) on the inner side of the top plate and a dust collection port (20) connected to a vacuum cleaner in the factory on the inner side of the back plate.

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