Automatic sandpaper changing device

Abstract

The present invention relates to a grinding device, in particular to an automatic sandpaper replacement device, comprising: a frame; a sandpaper tearing device, the sandpaper tearing device is mounted on the frame; and a sandpaper feeding device, the sandpaper feeding device comprising: a feeding rack, the feeding rack is mounted on the frame; a feeding cylinder, the feeding cylinder is mounted on the feeding rack and is used to place sandpaper; a blocking device, the blocking device is mounted on one end of the feeding cylinder; and a pushing device, the pushing device is mounted on the other end of the feeding cylinder and is used to push sandpaper toward the blocking device. The device realizes automatic tearing of sandpaper through the sandpaper tearing device, and automatic adsorption of sandpaper through the sandpaper feeding device, realizes automatic replacement of sandpaper, improves the efficiency of sandpaper replacement, and can detect whether the sandpaper is torn off and whether the replacement is completed, and can prevent sandpaper from stacking together, thereby improving the reliability of sandpaper replacement.

Description

Technical Field

[0001] The invention relates to a grinding device, in particular to an automatic sandpaper replacement device. Background Art

[0002] In order to improve the grinding efficiency, nowadays, mechanical arms are mostly used for automatic grinding. However, sandpaper has a service life, so it needs to be replaced after a period of use. The back of the sandpaper is self-adhesive to the grinding disc (sticky disc) of the grinder, so when replacing the sandpaper, you need to tear off the old sandpaper first, and then load the new sandpaper. At present, the main method of replacing sandpaper is manual. The grinder moves to a set position, the old sandpaper is manually torn off, and the new sandpaper is loaded. The manual replacement speed is slow, which affects the improvement of processing efficiency. Therefore, how to realize the automatic replacement of sandpaper is an urgent problem to be solved to improve processing efficiency. Summary of the invention

[0003] In order to solve the above problems, the present invention provides an automatic sandpaper replacement device which can automatically tear off sandpaper and load new sandpaper. The specific technical solution is as follows:

[0004] A sandpaper automatic replacement device comprises: a frame; a sandpaper tearing device, which is mounted on the frame; and a sandpaper feeding device, which comprises: a feeding rack, which is mounted on the frame; a feeding tube, which is mounted on the feeding rack and is used to place sandpaper; a blocking device, which is mounted on one end of the feeding tube; and a pushing device, which is mounted on the other end of the feeding tube and is used to push sandpaper toward the blocking device.

[0005] Preferably, the sandpaper tearing device includes: a sand tearing frame, which is installed on the top of the frame; a sand tearing seat, which is installed on one side of the sand tearing frame; a sand tearing cylinder, which is fixed on the sand tearing frame; and a sand tearing plate, which is fixed on the sand tearing cylinder and arranged opposite to the sand tearing seat, and the sand tearing plate is provided with an insertion end, which is triangular.

[0006] Preferably, the material blocking device includes: a material blocking ring, which is fixed on the feeding rack and located at one end of the feeding tube; and a material blocking plate, which is fixed on the material blocking ring and has a plurality of material blocking plates arranged in an array along the axis of the material blocking ring, and a material blocking end is provided on the material blocking plate, and the material blocking end is triangular and has an arc-shaped top.

[0007] Preferably, the pushing device includes: a pushing rod, which is movably inserted in the feeding barrel; a pushing cylinder, which is connected to the pushing rod; a fixed pushing plate, which is movably inserted in the feeding barrel and connected to the pushing rod; a telescopic rod, which is movably inserted in the fixed pushing plate, and an array is provided with several of them; a spring, which is movably inserted on the telescopic rod, and its two ends are respectively connected to the telescopic rod and the fixed pushing plate; and a movable pushing plate, which is movably inserted in the feeding barrel and is located on one side of the telescopic rod, and the sandpaper is located between the movable pushing plate and the blocking device.

[0008] Furthermore, it also includes a linkage rod, the two ends of which are respectively connected to the pushing cylinder and the telescopic rod, and the pushing cylinder is located inside the feeding rack and on one side of the feeding tube.

[0009] Wherein, the thickness of the movable pushing plate is not less than 5 mm; a feeding trough is provided on the movable pushing plate, and the telescopic rod is located in the feeding trough.

[0010] Preferably, it also includes a detection device, which includes: a detection plate, which is fixed on the movable push plate; a detection fixed plate, which is installed on the fixed push plate and movably inserted in the detection groove of the feeding barrel; and a proximity switch, which is fixed on the detection fixed plate and is arranged opposite to the detection plate.

[0011] Furthermore, it also includes: a concentric rib, on which a concentric groove is provided, the concentric rib is fixed to the material blocking device and is symmetrically located on both sides of the axis of the feed barrel, and the concentric groove matches the grinding disc of the grinder.

[0012] Furthermore, it also includes a color sensor, which is installed on the frame, the sandpaper tearing device or the sandpaper feeding device, and is used to detect whether the sandpaper is torn off and whether the sander is loaded with sandpaper.

[0013] Preferably, it also includes a sponge suction cup, which is installed on the frame, the sandpaper tearing device or the sandpaper feeding device.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The invention provides an automatic sandpaper replacement device which realizes automatic tearing off of sandpaper through a sandpaper tearing device and automatic adsorption of sandpaper through a sandpaper feeding device, thereby realizing automatic replacement of sandpaper and improving the efficiency of sandpaper replacement. The invention can detect whether the sandpaper has been torn off and whether the replacement has been completed, and can prevent the sandpaper from being stacked, thereby improving the reliability of sandpaper replacement. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of an automatic sandpaper changing device;

[0017] Figure 2 It is a structural schematic diagram of a sandpaper tearing device;

[0018] Figure 3 is a front view of the sandpaper tearing device;

[0019] Figure 4 It is a structural schematic diagram of a sandpaper feeding device;

[0020] Figure 5 is a cross-sectional view of the sandpaper feeding device;

[0021] Figure 6 It is a structural schematic diagram of the pushing device. DETAILED DESCRIPTION

[0022] The present invention will be further described with reference to the accompanying drawings.

[0023] Embodiment 1

[0024] like Figures 1 to 6 As shown, an automatic sandpaper changing device comprises a frame 1, a sandpaper tearing device 2 and a sandpaper feeding device 5.

[0025] A waste trough 11 is provided on the top of the frame 1, and a waste basket 12 is movably mounted in the waste trough 11. The sandpaper tearing device 2 is located above the waste basket 12. The waste basket 12 recycles old sandpaper.

[0026] The sandpaper tearing device 2 includes a sand tearing frame 21, a sand tearing seat 24, a sand tearing cylinder 22 and a sand tearing plate 23. The sand tearing frame 21 is installed on one side of the top of the frame 1 and is located above the waste trough 11. The sand tearing seat 24 is U-shaped and installed on one side of the sand tearing frame 21. The sand tearing cylinder 22 is a three-axis cylinder, which is fixed to the top of the sand tearing frame 21. The sand tearing plate 23 is fixed on the piston rod of the sand tearing cylinder 22 and is arranged opposite to the sand tearing seat 24. The sand tearing plate 23 is provided with an insertion end 231, which is triangular.

[0027] A sand tearing box 26 is also mounted on the sand tearing frame 21 , and the sand tearing box 26 prevents dust from entering the interior and protects the sand tearing cylinder 22 .

[0028] A positioning ring 25 is mounted on the sand tearing cylinder 22 , and the positioning ring 25 adjusts the distance between the sand tearing plate 23 and the sand tearing seat 24 .

[0029] The sandpaper feeding device 5 includes a feeding frame 51, a feeding cylinder 52, a blocking device and a pushing device. The feeding frame 51 is installed on the top of the frame 1 and is located on one side of the sand tearing frame 21. The feeding frame 51 is a U-shaped frame, and a feeding hole 511 and a mounting hole 512 are respectively provided at both ends of the feeding frame 51. The feeding hole 511 and the mounting hole 512 are coaxially arranged. A reinforcing plate 53 is installed at one end of the mounting hole 512.

[0030] The material blocking device includes a material blocking ring 54 and a material blocking plate 55. The material blocking ring 54 is fixed on the feed frame 51 and is coaxially arranged with the feed hole 511. The inner diameter of the material blocking ring 54 is slightly larger than the diameter of the sandpaper. The material blocking plate 55 is fixed on the material blocking ring 54, and three are arranged in a ring array along the axis. The material blocking plate 55 limits the sandpaper in the feed tube 52. The material blocking plate 55 is provided with a material blocking end 551 for blocking the sandpaper. The material blocking end 551 is triangular and has an arc-shaped top to prevent the sandpaper from being cut when the sandpaper is pulled out. The material blocking plate 55 is also provided with a waist-shaped fixing hole, which is convenient for adjusting the length of the material blocking plate 55 deep into the material blocking ring 54, and then it is convenient to adjust the position of the sandpaper blocking, so that the material blocking plate 55 can prevent the sandpaper from being automatically squeezed out, and at the same time facilitate the automatic removal of the sandpaper by the grinder.

[0031] The two ends of the feed barrel 52 are respectively inserted into the feed hole 511 and the mounting hole 512, and are located between the stop ring 54 and the reinforcing plate 53. The stop ring 54 and the reinforcing plate 53 fix the feed barrel 52; the feed barrel 52 can also be welded to the feed hole 511 and the mounting hole 512. The diameter of the feed barrel 52 is slightly larger than the diameter of the sandpaper, and the sandpaper is movably inserted into the feed barrel 52.

[0032] The pushing device includes a pushing rod 61, a pushing cylinder 63, a movable pushing plate 66, a telescopic rod 67, a spring 68 and a fixed pushing plate 62. The fixed pushing plate 62 is a circular plate, the diameter of which is slightly smaller than the inner diameter of the feeding tube 52, and the fixed pushing plate 62 is movably inserted into the feeding tube 52. The pushing rod 61 is fixed on the fixed pushing plate 62, and the pushing rod 61 is slidably connected with the reinforcing plate 53 through a linear bearing, and the reinforcing plate 53 increases the strength to avoid the linear bearing from being skewed, thereby ensuring reliable sliding. The linear bearing can make the axis of the fixed pushing plate 62 coincide with the axis of the feeding tube 52, thereby avoiding friction between the fixed pushing plate 62 and the inner wall of the feeding tube 52, so that the fixed pushing plate 62 moves smoothly, avoids jamming, and ensures reliable feeding.

[0033] The push cylinder 63 is fixed on the feeding rack 51 and is located on the inner side of the feeding rack 51. The push cylinder 63 is also located on one side of the feeding tube 52, and the push cylinder 63 is arranged parallel to the feeding tube 52. The push cylinder 63 is located on the inner side of the feeding rack 51, which can shorten the length of the entire feeding device and make the structure compact. The piston rod of the push cylinder 63 is connected to the other end of the telescopic rod 67 through the linkage rod 64, so that the fixed push plate 62 moves synchronously with the push cylinder 63.

[0034] The telescopic rod 67 is movably inserted on the fixed push plate 62, and the fixed push plate 62 is provided with six axial ring arrays. A flat washer and a nut are installed at one end of the telescopic rod 67. The flat washer limits the extension length of the telescopic rod 67. A limit ring is provided at the other end of the telescopic rod 67. A spring 68 is movably inserted on the telescopic rod 67. The two ends of the spring 68 are respectively against the limit ring and the fixed push plate 62. The other end of the telescopic rod 67 is movably against the movable push plate 66. The diameter of the movable push plate 66 is slightly smaller than the inner diameter of the feed barrel 52. The movable push plate 66 is movably inserted in the feed barrel 52. The sandpaper is located between the fixed push plate 62 and the blocking device. The spring 68 provides a certain thrust to the movable push plate 66 to achieve buffering, so as to prevent the push cylinder 63 from directly pushing the sandpaper out of the feed barrel 52 when the push cylinder 63 is started after loading.

[0035] The thickness of the movable push plate 66 is not less than 5 mm. The movable push plate 66 has a certain thickness, so that the movable push plate 66 can be prevented from falling after being separated from the telescopic rod 67. If the push cylinder 63 loses air or extends accidentally, the movable push plate 66 will be in a free state, and the sandpaper will rebound after losing pressure, so that the movable push plate 66 moves backward. If the thickness of the movable push plate 66 is thin, the movable push plate 66 is easy to fall or tilt, causing part of the sandpaper to fall or tilt. After the push cylinder 63 is restored, the push cylinder 63 will squeeze the movable push plate 66 and the sandpaper when it retracts, and it is easy to squeeze the fallen or tilted sandpaper. When the movable push plate 66 has a certain thickness, the movable push plate 66 will not fall, thereby ensuring that the sandpaper will not fall or tilt, so that the sandpaper is in a nearly vertical state. The movable push plate 66 is movably connected to the telescopic rod 67 to solve the above problem, preventing the movable push plate 66 from retracting with the push cylinder 63. In the event of misoperation, the movable push plate 66 can always block one side of the sandpaper to prevent the sandpaper from tipping over or tilting.

[0036] The movable push plate 66 is provided with a feed trough 661, and the end of the telescopic rod 67 is located in the feed trough 661. The feed trough 661 can increase the amount of sandpaper without affecting the thickness of the movable push plate 66.

[0037] In order to prevent dust from entering the interior, a feeding box 57 is installed on the feeding rack 51 , and the feeding device and the feeding cylinder 52 are both located in the feeding box 57 .

[0038] During operation, the mechanical arm drives the grinder to move to the bottom of the sand tearing plate 23, and inserts the grinding disc and sandpaper between the sand tearing plates 23, then the sand tearing cylinder 22 retracts, the sand tearing plate 23 presses the sandpaper against the sand tearing seat 24, and then the mechanical arm drives the grinder away from the sand tearing seat 24, the old sandpaper is torn off, and then the sand tearing cylinder 22 extends, and the old sandpaper falls into the waste basket 12. When installing sandpaper, the push cylinder 63 extends, and the push cylinder 63 drives the fixed push plate 62 and the elastic device to retract to the tail of the feed tube 52, then remove the baffle plate 55, load the sandpaper, and push the movable push plate 66 to move toward the tail of the feed tube 52 until the set amount of sandpaper is loaded, then reinstall the baffle plate 55, start the push cylinder 63, and the push cylinder 63 drives the fixed push plate 62 and the elastic device to push the movable push plate 66 to move, and the movable push plate 66 presses the sandpaper against the baffle plate 55. When the grinding disc of the grinder is pressed onto the sandpaper, and the grinder moves outward after absorbing the sandpaper, the grinder drives the sandpaper to be pulled out from the baffle plate 55, and the remaining sandpaper continues to be restricted in the feed tube 52 by the baffle plate 55, and the push cylinder 63 continues to provide a pressing force.

[0039] The feeding barrel 52 has a certain depth and can hold a large number of sandpapers, thereby reducing the number of times the sandpapers need to be replenished, thereby extending the continuous working time and improving the processing efficiency.

[0040] Embodiment 2

[0041] like Figures 1 to 6 As shown, on the basis of the above-mentioned embodiment 1, a detection device is further included, and the detection device includes a detection plate 71, a detection fixing plate 72 and a proximity switch 73. Among them, a waist-shaped detection groove 521 is provided on the side of the feeding cylinder 52 along the axis, and the detection fixing plate 72 is movably inserted in the detection groove 521. The detection fixing plate 72 is also fixed on the fixed push plate 62. The proximity switch 73 is installed on the detection fixing plate 72. The detection plate 71 is fixed on the movable push plate 66 and is arranged opposite to the proximity switch 73.

[0042] In order to improve the feeding stability, the electromagnetic valve controlling the push cylinder 63 adopts a three-position five-port electromagnetic valve with a closed middle. When the proximity switch 73 detects the detection plate 71, the electromagnetic valve switches to a closed state, and the push cylinder 63 maintains a constant position and does not move. At this time, the spring 68 provides a clamping force to clamp the sandpaper, which solves the problem of the pressure fluctuation of the push cylinder 63 causing the clamping force fluctuation, and avoids the situation where the pressure increases during the pressure fluctuation and causes the sandpaper to be squeezed out of the feeding tube 52. Every time the grinder takes away a piece of sandpaper, the movable push plate 66 moves forward by the position of a sandpaper under the action of the spring 68. When a certain amount of sandpaper is taken away, the proximity switch 73 cannot detect the detection plate 71. At this time, the push cylinder 63 restarts and presses the sandpaper again until the proximity switch 73 detects the detection plate 71 again.

[0043] In order to facilitate the adjustment of the pressure of the spring 68 pressing the sandpaper, a detection limit screw 74 is also included, which is installed on the detection fixing plate 72 and is arranged opposite to the detection plate 71. When adjusting the position of the proximity switch 73, the detection limit screw 74 is first adjusted, and the detection limit screw 74 adjusts the distance between the fixed push plate 62 and the movable push plate 66, thereby adjusting the pressing force of the spring 68, and then adjusting the proximity switch 73. When the proximity switch 73 can detect the detection plate 71, the proximity switch 73 is fixed.

[0044] Embodiment 3

[0045] like Figures 1 to 6 As shown, based on any of the above embodiments, it also includes a concentric rib 56, on which a concentric groove 561 is provided. The concentric rib 56 is fixed on the retaining ring 54 and is symmetrically located on both sides of the axis of the feed barrel 52. The concentric groove 561 matches the grinding disc of the grinder.

[0046] The grinding disc of some grinders is eccentrically set. When such grinders automatically press the grinding disc onto the sandpaper, the sandpaper and the grinding disc may not be concentric, which affects the grinding quality. After the concentric rib 56 is adopted, when the mechanical arm drives the grinder to move toward the feed tube 52, the position of the grinder is controlled according to the eccentric distance of the grinder, so that the grinding disc is stuck on the concentric grooves 561 of the two concentric ribs 56, so that the grinding disc and the sandpaper are coaxial, and then the mechanical arm drives the grinding disc to press onto the sandpaper, automatically adsorbing the sandpaper, solving the problem of the sandpaper and the eccentric grinding disc not being concentric.

[0047] Embodiment 4

[0048] like Figures 1 to 3 As shown, based on any of the above embodiments, a color sensor is further included, and two color sensors are provided, including a sand tearing color sensor 31 and a sandpaper loading color sensor 32. The sand tearing color sensor 31 and the sandpaper loading color sensor 32 are both installed on the sand tearing frame 21 and are arranged opposite to the detection through hole 241 of the sand tearing seat 24. The sand tearing color sensor 31 is used to detect whether the sandpaper is torn off, and the sandpaper loading color sensor 32 is used to detect whether the sandpaper is loaded on the grinder.

[0049] When the sand tearing is completed, the sand tearing color sensor 31 detects the grinding disc. If the grinding disc is detected, it means that the sandpaper has been torn off and new sandpaper can be installed. Otherwise, it means that the sandpaper has not been torn off and the sandpaper needs to be torn off again. The robotic arm can also drive the grinder to rotate the angle to repeat the sand tearing step, and then detect again whether the sand tearing is completed. The sand tearing color sensor 31 can detect whether the sandpaper has been torn off and whether there is residual sandpaper on the grinding disc to avoid residual sandpaper affecting the grinding quality. After the grinding disc absorbs the sandpaper, it moves to the sandpaper color sensor 32. The sandpaper color sensor 32 detects the sandpaper. When the sandpaper color sensor 32 detects the sandpaper, it means that the sandpaper installation is complete.

[0050] The sand tearing color sensor 31 and the sandpaper loading color sensor 32 ensure reliable tearing and adsorption of the sandpaper, thereby ensuring reliable grinding.

[0051] Embodiment 5

[0052] like Figures 1 to 3 As shown, based on any of the above embodiments, a sponge suction cup 41 is further included, and the sponge suction cup 41 is installed on the sand tearing frame 21 through a vacuum tube 42.

[0053] The sponge suction cup 41 is connected to the vacuum generator through the vacuum tube 42 to prevent multiple sandpapers from being adsorbed on the grinding disc and to avoid the sandpapers from being stacked together, thereby ensuring reliable grinding.

[0054] After the installation of the new sandpaper is completed, the robotic arm drives the grinder to move to the sponge suction cup 41, and then presses the new sandpaper onto the sponge suction cup 41. The sponge suction cup 41 adsorbs the sandpaper under the action of the vacuum generator. The adsorption force of the sponge suction cup 41 on the sandpaper is smaller than the adsorption force between the grinding disc and the sandpaper, thereby preventing the sponge suction cup 41 from sucking the new sandpaper off the grinding disc. If two sandpapers are superimposed, the sponge suction cup 41 can adsorb the outer sandpaper, and the adsorption force between the two sandpapers is smaller than the adsorption force of the sponge suction cup 41. Therefore, it can be ensured that there is only one piece of sandpaper on the grinding disc when the grinder is grinding, thereby effectively solving the problem of sandpaper superposition.

[0055] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the protection scope of the claims of the present invention.

Claims

1. An automatic sandpaper replacement device, characterized in that: include: Rack(1); A sandpaper tearing device (2), wherein the sandpaper tearing device (2) is mounted on the frame (1); and A sandpaper feeding device (5), wherein the sandpaper feeding device (5) comprises: A feeding rack (51), the feeding rack (51) being mounted on the frame (1); A feeding cylinder (52), the feeding cylinder (52) being mounted on the feeding frame (51) and being used for placing sandpaper; a material blocking device, the material blocking device being mounted on one end of the feeding cylinder (52); and A pushing device, the pushing device being mounted at the other end of the feeding cylinder (52) and being used for pushing the sandpaper toward the blocking device; The pushing device comprises: A push rod (61), the push rod (61) being movably inserted into the feeding barrel (52); A pushing cylinder (63), the pushing cylinder (63) being connected to the pushing rod (61); A fixed push plate (62), the fixed push plate (62) being movably inserted into the feeding cylinder (52) and connected to the push rod (61); A telescopic rod (67), wherein the telescopic rod (67) is movably inserted into the fixed push plate (62), and a plurality of telescopic rods (67) are provided in an array; a spring (68), the spring (68) being movably inserted into the telescopic rod (67), and having two ends respectively connected to the telescopic rod (67) and the fixed push plate (62); and A movable push plate (66) is movably inserted into the feeding tube (52) and is located on one side of the telescopic rod (67); the sandpaper is located between the movable push plate (66) and the material blocking device.

2. The automatic sandpaper changing device according to claim 1, characterized in that: The sandpaper tearing device (2) comprises: A sand tearing frame (21), the sand tearing frame (21) being mounted on the top of the frame (1); A sand tearing seat (24), the sand tearing seat (24) being mounted on one side of the sand tearing frame (21); a sand-tearing cylinder (22), the sand-tearing cylinder (22) being fixed on the sand-tearing frame (21); and A sand tearing plate (23), the sand tearing plate (23) being fixed on the sand tearing cylinder (22) and arranged opposite to the sand tearing seat (24), the sand tearing plate (23) being provided with an insertion end (231), the insertion end (231) being triangular in shape.

3. The automatic sandpaper changing device according to claim 1, characterized in that: The material blocking device comprises: a material blocking ring (54), the material blocking ring (54) being fixed on the material feeding frame (51) and being located at one end of the material feeding cylinder (52); and A material blocking plate (55) is fixed on the material blocking ring (54), and a plurality of the material blocking plates (55) are arranged in an array along the axis of the material blocking ring (54). The material blocking plate (55) is provided with a material blocking end (551), and the material blocking end (551) is triangular in shape, and the top is arc-shaped.

4. The automatic sandpaper changing device according to claim 1, characterized in that: It also includes a linkage rod (64), the two ends of which are respectively connected to the push cylinder (63) and the telescopic rod (67), and the push cylinder (63) is located inside the feeding rack (51) and on one side of the feeding barrel (52).

5. The automatic sandpaper changing device according to claim 1, characterized in that: The thickness of the movable push plate (66) is not less than 5 mm; a material supply trough (661) is provided on the movable push plate (66), and the telescopic rod (67) is located in the material supply trough (661).

6. The automatic sandpaper changing device according to claim 1, characterized in that: Also included is a detection device, the detection device comprising: A detection plate (71), the detection plate (71) being fixed on the movable push plate (66); a detection fixing plate (72), the detection fixing plate (72) being mounted on the fixed material pushing plate (62) and being movably inserted into the detection slot (521) of the material feeding cylinder (52); and A proximity switch (73), wherein the proximity switch (73) is fixed on the detection fixing plate (72) and is arranged opposite to the detection plate (71).

7. The automatic sandpaper changing device according to any one of claims 1 to 6, characterized in that: Also includes: A concentric rib (56), wherein a concentric groove (561) is provided on the concentric rib (56), the concentric rib (56) is fixed to the material retaining device and is symmetrically located on both sides of the axis of the feeding tube (52), and the concentric groove (561) matches the grinding disc of the grinder.

8. The automatic sandpaper changing device according to any one of claims 1 to 6, characterized in that: It also includes a color sensor, which is installed on the frame (1), the sandpaper tearing device (2) or the sandpaper feeding device (5) and is used to detect whether the sandpaper has been torn off and whether the sandpaper has been loaded on the grinding machine.

9. The automatic sandpaper changing device according to any one of claims 1 to 6, characterized in that: It also comprises a sponge suction cup (41), wherein the sponge suction cup (41) is mounted on the frame (1), the sandpaper tearing device (2) or the sandpaper feeding device (5).

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